Jahangir Masud - Academia.edu (original) (raw)

Papers by Jahangir Masud

Mikrochimica Acta, Jul 11, 2020

A simple binary copper selenide, CuSe nanostructure, has been investigated as electrochemical sen... more A simple binary copper selenide, CuSe nanostructure, has been investigated as electrochemical sensor for dopamine detection. The hydrothermally synthesized and electrodeposited CuSe nanostructures showed high sensitivity for dopamine detection with low limit of detection (LOD). A sensitivity of 26 μA/μM.cm 2 was obtained with this electrochemical sensor which is ideal to detect even small fluctuations in the transient dopamine concentration. Apart from high sensitivity and low LOD, the dopamine oxidation on the catalyst surface also occurred at a low applied potential (< 0.18 V vs Ag|AgCl), thereby significantly increasing selectivity of the process specifically with respect to ascorbic and uric acids, which are considered to be the most prominent interferents for dopamine detection. Electrochemical redox tunability of the catalytic Cu center along with low coordination geometry is believed to enhance the rate of dopamine attachment and oxidation on the catalyst surface thereby reducing the applied potential. The presence of Cu also increases conductivity of the catalyst composite which further improves the charge transfer thus increasing the sensitivity of the device. This is the first report of electrochemical dopamine sensing with a simple binary selenide comprising earth-abundant elements and can have large significance in designing efficient sensors that can be transformative for understanding neurodegenerative diseases further.

Meeting abstracts, 2017

Water electrolysis leading to generation of oxygen and hydrogen, has been one of the most promisi... more Water electrolysis leading to generation of oxygen and hydrogen, has been one of the most promising routes towards sustainable alternative energy generation and storage, with applications ranging from metal-air batteries, fuel cells, to solar-to-fuel energy conversion systems. Oxygen and Hydrogen evolution reaction (OER and HER respectively) are the two half reactions for water electrolysis, amongst which OER is the most challenging uphill process with a high electron count. Hence, designing efficient catalysts for OER process from earth-abundant resources has been one of the primary concerns for advancing this field. Recently transition metal chalcogenides has been identified as efficient OER electrocatalysts. We have synthesized a plethora of transition metal selenides including those based on Ni, Ni-Fe, Co, and Ni-Co, which show high catalytic efficiency characterized by low onset potential and overpotential at 10 mA/cm2 [Ni3Se2 - 200 - 290 mV; Co7Se8 - 260 mV; FeNi2Se4-NrGO - 170 mV (NrGO - N-doped reduced graphene oxide); NiFe2Se4 - 210 mV; NiCo2Se4 - 190 mV]. We have proposed the idea that one of the primary reasons these selenides show a much better OER catalytic activity is due to increasing covalency in the metal-selenium bond compared to the oxides caused by decreasing electronegativity of the anion, which in turn leads to variation of chemical potential around the transition metal center, specifically, lowering the Ni2+ --&amp;gt; Ni3+ oxidation potential (Ni3+ being the actually catalytically active species). In this presentation we will highlight the importance of this increasing covalency in enhancing the catalytic activity with the help of experimental evidence in selenide compositions ranging from binary Ni-selenides (Ni3Se2, NiSe2, NiSe), ternary mixed metal selenides (Ni-Co-Se, Ni-Fe-Se) as well as seleno-based molecular complex containing NiSe4 tetrahedral core. We will illustrate how the Ni(II) --&amp;gt; Ni(III) oxidation potential is indeed lowered within the selenide coordination compared to the oxide, in pure single crystals of the seleno-based coordination complex which is devoid of any surface impurities and adsorbates. We will also emphasize the lattice-plane-dependent catalytic activity through the example of electrodeposited NiSe2 which shows that if grown along the &amp;lt;311&amp;gt; direction exposing the Ni-rich terminating lattice plane, this catalyst can exhibit lowest overpotential at 10 mA/cm2 (140 mV) that has been reported so far for OER in alkaline medium. All of these selenide electrocatalysts has been characterized with pxrd, SEM, TEM, Raman, XPS, EDS and detailed electrochemical studies including LSV, CV, chronoameprometry, chronopotentiometry, determination of Faradaic efficiency, and ECSA. Through this presentation we will offer insight into possible reasons these selenides outperform most of the known OER electrocatalysts, which will hopefully initiate discussion and efforts to fully understand and utilize their full potential.

Meeting abstracts, 2017

Splitting water to hydrogen and oxygen through hydrogen evolution reaction (HER) and oxygen evolu... more Splitting water to hydrogen and oxygen through hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is basis to feed the fuel cell. OER is a thermodynamically uphill process as it requires higher potential to form O2 molecule. The best known catalysts to split water with low overpotential are the oxides of Ir and Ru. As these catalysts are precious metals there has been intensive research to substitute them with earth-abundant resources. The new catalyst should fulfill the following: (i) the catalyst to split water has to use minimal energy (measured as applied voltage and referred to as overpotential); (ii) should comprise of earth abundant elements; (iii) should be stable; (iv) should be scalable.1 Transition metal oxides have been recently identified as high-efficiency catalysts for oxygen and/or hydrogen evolution reaction. Apart from the oxides there has been reports of sulfide, selenide and nitride based catalysts.2 Although transition metal phosphides has recently gathered attention as HER catalysts,3 very less metal phosphides have been reported as OER electrocatalyst. In this presentation, ultra-small iron phosphide nanoparticles as well nanoparticle composite with reduced graphene oxide (FeP-rGO) has been reported as efficient electrocatalysts for OER under alkaline conditions. FeP nanoparticles require an overpotential of 290 mV @ 10 mAcm-2. It is well known that rGO is a good conductor and a support material for the catalysts. Hence, mixing of FeP nanoparticles with rGO has improved the catalytic efficiency further by reducing the overpotential to 260 mV to achieve 10 mAcm-2 current density4. The FeP nanoparticles and FeP-rGO composite showed the lowest overpotential at 10 mA/cm2 that has observed among the pnictide making these the most-efficient phosphide based OER catalyst till date. The hybrid catalyst showed a low Tafel slope of 50.8 mV/dec. The stability of the catalyst was excellent with 4h of continuous oxygen evolution and the catalytic activity was retained with a similar overpotential @ 10 mAcm-2. The synthesis of hybrid catalysts, detailed characterization, and electrochemical studies including liner scan voltammetry (LSV), choronoamperometry will be discussed in detail. References: Bard, A. J.; Fox, M. A. Artificial photosynthesis solar splitting of water to hydrogen and oxygen. Acc. Chem. Res. 1995, 28, 141-145 Swesi, A. T.; Masud, J.; M. Nath. Nickel selenide as a high-efficiency catalyst for oxygen evolution reaction. Energy Environ. Sci. 2016, 9, 1771-1782. Popczun, E, J.; Read, C, G.; Roske, C, W.; Lewis, N, S.; Schaak, R, E. Highly Active Electrocatalysis of the Hydrogen Evolution Reaction by Cobalt Phosphide Nanoparticles. Angew. Chem. Int. Ed. 2014, 53, 5427 –5430. Masud, J.; Umapathi, S.; Ashokaan, N.; Nath, M. Iron phosphide nanoparticles as an efficient electrocatalyst for the OER in alkaline solution. J. Mater. Chem. A, 2016,4, 9750-9754. Figure 1

Meeting abstracts, 2015

There is a growing interest in oxygen electrode catalysts for oxygen reduction reaction (ORR) and... more There is a growing interest in oxygen electrode catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as they play a key role in a wide range of renewable energy technologies such as fuel cells, metal-air batteries, and water splitting. Nevertheless, the development of highly-active bifunctional catalysts at low cost for both ORR and OER still remains a huge challenge [1]. Herein, we report, a cost effective alternative, viz. cobalt selenide Co­x­Se­­y nanotube and nanorod arrays which shows considerable catalytic activity afor OER and/or ORR., The CoxSey nanostructure arrays were produced by a protocol developed recently in the Nath laboratory [2] which involves confined electrodeposition on lithographically created nanoelectrodes. ORR activity of catalysts were evaluated in acidic medium (Fig. 1). Coating the CoxSey nanostructures with a thin layer of Pt (CoxSey-Pt) also exhibits enhanced catalytic efficiency. ORR current densities of CoxSey and CoxSey-Pt are comparable with Pt which indicate the four electron reduction process of all catalysts. Besides ORR, CoxSey exhibits excellent activity towards OER. The polarization curve (inset of Fig. 1) for CoxSeyin linear sweep voltammetry (LSV) conditions show higher current and earlier onset (ca. 330 mV) of catalytic current in comparison with Pt in 1M KOH solution. Detailed characterization and analysis of ORR/OER activity of catalyst will be presented along with structural and morphological characterization of the active catalyst surface and the relationship between morphology and the observed catalytic activity. References: N.I. Andersen, A. Serov, P. Atanassov Applied Catalysis B: Environmental, 2015, 163, 623. S. Mishra and Manashi Nath, Nano Energy, 2013, 2, 1207 Figure 1

Meeting abstracts, 2016

Transition metal chalcogenides has been a heartthrob of solid state chemists owing to the richnes... more Transition metal chalcogenides has been a heartthrob of solid state chemists owing to the richness of properties they exhibit as well as their structure-property correlation. In addition to their viable optoelectronic properties, it has been recently observed that some of these transition metal chalcogenide (especially selenides) show high electrocatalytic activities for oxygen evolution/reduction reactions (OER/ORR respectively) and hydrogen evolution reaction (HER). Recently we have formulated some new transition metal chalcogenide based compositions which show an enhanced catalytic activity for OER based on their d-electron occupancy and structural parameters.1 Among these the Ni-based selenide thin films and nanostructures show much better catalyst activity along with lower onset potential for O2 evolution outperforming the state-of-the-art precious metal based catalysts. It was also observed that doping other transitional metals in the Nickel selenide matrix led to enhancing catalyst efficiency. The catalysts were synthesized mainly through electrodeposition on different substrates like Au-coated glass, Au-coated Si as well as glassy carbon (GC). The nanostructured catalysts were made through chemical vapor deposition (CVD) and solvothermal reaction. In a separate approach nanorod and nanotube arrays of these electrocatalysts were grown through electrodeposition on lithographically patterned nanoelectrodes. Nanostructuring typically led to much better efficiency with low catalyst volume, with the nanorod/nanotube pattern producing the highest activity with lowest electrode coverage with the active material. The catalytic activities for OER, ORR and HER were investigated through detailed electrochemical measurements including linear scale voltammetry, chronoamperometry, Tafel slope analysis as well as determination of Faradaic efficiency through rotating ring disk electrode studies. Interestingly some of these selenides showed bifunctional or trifunctional nature showing efficient catalytic activity for OER-HER and OER-HER-ORR processes, respectively. In this talk we will present a systematic study of the selenide based electrocatalysts including binary (NixSey, CoxSey) as well as ternary chalcogenides, Ni xMy Sen (M = Fe, Co, Mn, Al) and investigating their catalytic activities for OER, HER, and ORR reactions. We will also discuss the effect of d-electron counts, electronic structure and morphology on the catalytic efficiency. References Swesi, A.; Masud, J.; Nath, M. Energy Environ. Sci. 2015 doi: 10.1039/C5EE02463C.

ACS omega, Jun 26, 2019

Developing Nonenzymatic glucose biosensors has recently been at the center of attention owing to ... more Developing Nonenzymatic glucose biosensors has recently been at the center of attention owing to their potential application in implantable and continuous glucose monitoring systems. In this article, nickel telluride nanostructure with the generic formula of Ni 3 Te 2 has been reported as a highly efficient electrocatalyst for glucose oxidation, functional at a low operating potential. Ni 3 Te 2 nanostructures were prepared by two synthesis methods, direct electrodeposition on the electrode and hydrothermal method. The electrodeposited Ni 3 Te 2 exhibited a wide linear range of response corresponding to glucose oxidation exhibiting a high sensitivity of 41.615 mA cm −2 mM −1 and a low limit of detection (LOD) of 0.43 μM. The hydrothermally synthesized Ni 3 Te 2 , on the other hand, also exhibits an ultrahigh sensitivity of 35.213 mA cm −2 mM −1 and an LOD of 0.38 μM. The observation of high efficiency for glucose oxidation for both Ni 3 Te 2 electrodes irrespective of the synthesis method further confirms the enhanced intrinsic property of the material toward glucose oxidation. In addition to high sensitivity and low LOD, Ni 3 Te 2 electrocatalyst also has good selectivity and long-term stability in a 0.1 M KOH solution. Since it is operative at a low applied potential of 0.35 V vs Ag|AgCl, interference from other electrochemically active species is reduced, thus increasing the accuracy of this sensor.

Journal of Materials Chemistry B, 2019

A CoNi2Se4–rGO nanocomposite fabricated on Ni foam shows excellent efficiency for non-enzymatic g... more A CoNi2Se4–rGO nanocomposite fabricated on Ni foam shows excellent efficiency for non-enzymatic glucose sensing at low applied potential.

ACS Catalysis, Jul 25, 2018

Designing high efficiency electrocatalysts for water oxidation has become an increasingly importa... more Designing high efficiency electrocatalysts for water oxidation has become an increasingly important concept in the catalysis community due to its implications in clean energy generation and storage. In this respect transition metal doped mixed metal selenides incorporating

Social Science Research Network, 2023

TechConnect Briefs, Oct 18, 2021

Meeting abstracts, Sep 1, 2016

First raw transition metal-based chalcogenides (FRTMCs) are promising devices for next generation... more First raw transition metal-based chalcogenides (FRTMCs) are promising devices for next generation to serve as effective substitutes for the Pt-based electrocatalysts in fuel cell systems. OER and HER are considered to be clean and sustainable energy technology and an alternative for fossil fuels. However, OER involving a complex 4 electron process, has several steps that have large reaction barriers, which lead to large required overpotentials. Identifying more-efficient, stable and earth-abundant catalysts for water splitting has long been investigated. The planar configuration of FRTMCs could lead to robust integration for electronic devices. Nanostructured electroactive materials that are fabricated in-plane FRTMCs have attracted great attentions as a kind of storage energy material due to its electrochemistry properties. Recently we have observed that Ni-chalcogenide (Ni3Se2) is superior to the precious transition metal oxide-based electrocatalysts in terms of onset overpotential for O2 evolution as well as overpotential to reach a current density of 10 mA cm-2. With the onset of decreasing particle size to nanometric scale, electrodeposition techniques have provided an alternative route to obtain a variety of new nanomaterials with improved and well controlled properties. The improvement of properties of the metallic composites is dependent mainly on the morphology of materials. Morphology-controllable Ni3Se2 films were successfully prepared by electrodepositing Ni3Se2 film on Au substrate and following by electrochemical dissolution. In electrochemical dissolution process, Ni3Se2 phase is well-preserved and porous structure formed. This technology is a promising way to fabricate other porous materials. A porous Ni3Se2 film showed an enhanced OER catalytic performance in comparison with the as-deposited Ni3Se2 film. The results proved that the OER catalytic performance of porous Ni3Se2 film delivers the highest activity. Introduction of pores to the catalyst material by the electrochemical dissolution is availability for improve the electrochemical performance of the material for OER electrocatalysts. The catalytic efficiency of the proposed catalysts was investigated through linear scan voltammetry (LSV), chronoamperommetry and double layer capacitance. Utilizing rotating ring disc electrode (RRDE) assemblies, the kinetics of OER process between various catalysts as well as the Faradaic efficiency were studied. The catalytic activity of the proposed novel compound (Ni3Se2) was also compared to the outstanding electrocatalysts for OER under conditions relevant to an integrated solar water-splitting device which have been reported so far. The synthesis, characterization, catalytic activity and advancement of the field will be presented in details.

Energy & Fuels, Feb 12, 2021

Recently, nickel-selenide- and -telluride-based electrocatalysts have shown promising results tow... more Recently, nickel-selenide- and -telluride-based electrocatalysts have shown promising results toward water electrolysis, exhibiting very low overpotential. However, a major challenge for these chal...

Advanced sustainable systems, Sep 22, 2017

Water splitting reaction using earth‐abundant and environmentally benign catalysts is critical fo... more Water splitting reaction using earth‐abundant and environmentally benign catalysts is critical for renewable energy generation and storage. Herein a hybrid composite, FeNi2Se4 nanoparticles supported on nitrogen doped reduced graphene oxide (FeNi2Se4–NrGO) is reported as an efficient and dependable bifunctional electrocatalyst for oxygen evolution and oxygen reduction reactions (OER and ORR, respectively) under alkaline conditions. While FeNi2Se4 nanoparticles themselves show good catalytic activity for water oxidation, the constructed hybrid nanocomposite with NrGO as the supporting matrix show enhanced catalytic activity with a small overpotential of 170 mV @ 10 mA cm−2, small Tafel slope of 62.1 mV per decade, and high current density. The ORR catalytic activity of the nanocomposite catalyst is also good with an onset potential of 0.93 V. This is possibly due to the synergistic chemical coupling effects between the FeNi2Se4 and NrGO matrix. Chronoamperometric studies show that the catalyst is stable under conditions of continuous O2 evolution and reduction with very less degradation. Apart from reporting highly efficient OER–ORR bifunctional catalyst, this study also provides more proof for the effect of anion coordination on the catalyst performance, as well as the synergistic role of nanoscale interactions between the catalyst particles and graphene matrix to enhance catalytic activity.

ACS energy letters, Apr 18, 2016

Co 7 Se 8 nanostructures electrodeposited on glassy carbon (GC) electrodes show high efficiency f... more Co 7 Se 8 nanostructures electrodeposited on glassy carbon (GC) electrodes show high efficiency for oxygen reduction reaction (ORR) with high methanol tolerance as compared to Pt electrocatalysts. In the presence of methanol, the onset potential for the ORR at Pt/GC is shifted from 0.931 V (vs reversible hydrogen electrode (RHE)) to 0.801 V (vs RHE), whereas it remains the same (0.811 V vs RHE) at Co 7 Se 8 /GC in the presence and absence of methanol in 0.5 M H 2 SO 4 solution. The Co 7 Se 8 /GC electrodes also showed high cyclability in the presence of methanol, with no degradation of catalytic performance. It is also noteworthy that the Co 7 Se 8 /GC exhibited exclusively a four-electron reduction pathway for ORR and very low H 2 O 2 yield in acidic electrolyte. The admirable performance of Co 7 Se 8 /GC catalyst along with its cost-effective nature holds great potential for application in direct methanol fuel cells.

Meeting abstracts, Apr 15, 2017

The development of a highly active catalyst for water splitting to produce oxygen and hydrogen fu... more The development of a highly active catalyst for water splitting to produce oxygen and hydrogen fuels is in rising demand to fulfill the increasing human need for clean and renewable energy. However, the most crucial step for efficient electrocatalytic water splitting is the oxygen evolution reaction (OER) that takes place at the anode. Traditionally, metal oxides have been introduced for this purpose however, recent developments have shown that transition metal selenides also shows better catalytic activity towards OER surpassing most of the conventional oxide electricatalysts. Herein we present how the family of chalcogenide electrocatalysts can be extended to transition metal tellurides and we will present the OER electrocatalytic activity of the first ever telluride, Ni3Te2 synthesized by hydrothermal reactions as well as electrodeposition technique. This catalyst show an overpotential of 170 mV at 10 mA/cm2 during the OER electrocatalytic activity in 1 M KOH, which is one of the lowest reported value till date and that highlight the high performance of this catalyst. Additionally, this catalyst also shows a high catalytic activity towards hydrogen evolution reaction (HER) and it only requires 250 mV over potential to achieve a current density of 10 mA/cm2 during HER conditions and that makes it a bifunctional elecrocatalyst. We will present the synthesis, characterization and electrochemical investigations of this new catalyst and additionally, we will also discuss the stability of this catalyst during long term OER conditions.

Journal of The Electrochemical Society, Jan 27, 2022

Rare earth elements (REEs) extraction via conventional technologies is exceedingly energy and env... more Rare earth elements (REEs) extraction via conventional technologies is exceedingly energy and environmentally intensive. New efficient and sustainable technologies for REE extraction from primary and secondary resources would be extremely beneficial. This research demonstrated a novel low-temperature electrochemical extraction process for extracting REEs from lignite coal ash (LCA) solutions. The LCA contained 17 different REEs with a concentration ranging from 13 to 1645 ppm. The LCA solution mixed with ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate (BMITF) was used for extracting REEs at different electrochemical potentials. The ICP-MS analysis confirmed an overall 26% REEs recovery from the LCA solution with 16 out of the 17 REEs successfully extracted from the LCA solution. This study shows an environmentally benign and energy-efficient REE extraction process that is suitable for coal and coal byproducts.

Meeting abstracts, May 1, 2019

Diabetes has long been recognized as one of the leading causes of death in the United States and ... more Diabetes has long been recognized as one of the leading causes of death in the United States and worldwide second only to cancer and heart-related ailments. Diabetes is a silent killer and early stage diagnosis and controlling blood glucose level is the key to maintain and control the disease. Blood glucose levels are typically monitored with the help of glucose detection through electrochemical oxidation of glucose to gluconic acid or gluconolactone. Typically, in conventional glucose detectors, enzyme-based electrochemical sensors are used which suffers from several critical challenges including reduced efficiency and sensitivity, reduced shelf lives, lack of long-term stability (due to enzyme denaturation), high fabrication cost (due to complex enzyme purification steps), and high detection limit (due to less efficient indirect electron transfer). In this presentation we will discuss about designing high-efficiency direct glucose electrochemical sensors from transition metal chalcogenides using principles of materials chemistry, specifically, tuning the redox potential of the transition metal site. We will present several examples of high-efficiency chalcogenide based glucose sensors including CoNi2Se4-rGO nanocomposite, Ni3Te2, Cu2Se, and NiSe. These chalcogenide based electrocatalysts show high activity for glucose oxidation at very low potential (~0.35 - 0.45 V vs Ag|AgCl) with high sensitivity (exceeding 18 mA/mM cm2) and low limit of detection (LOD). These chalcogenides can offer direct electron transfer pathways over a wide potential range leading to much higher sensor efficiency. Moreover, the sensing performance of these electrocatalysts were tested in presence of common interferents present in physiological samples such as dopamine, ascorbic acid, lactose, etc., where it showed that glucose sensing was unaffected primarily because at such low potential, other biomolecules are not affected. In fact, the ability to oxidize glucose at such low potential is considered to be one of the most prominent novelty of these chalcogenide electrocatalysts, and the glucose oxidation potential of 0.35V (CoNi2Se4) is one of the lowest reported potential till date. The reason for such high activity for glucose oxidation was investigated through a series of experiments designed to alter the redox potential of the transition metal site either by changing the anion (selenide to telluride), transition metal doping (NiSe vs CoNi2Se4), or changing the d-electron occupancy (NiSe vs Cu2Se). Through these measurements we observed that on changing the electronegativity of the anion from selenide to telluride, the glucose oxidation potential could be reduced further due to transition metal site oxidation occurring at a lower potential. The transition metal site oxidation can be considered as the catalyst activation step which initiates the glucose oxidation. Transition metal doping at the active site also helped to redistribute the electron density thereby influencing catalyst activation and subsequent glucose oxidation steps. Interestingly, using highly occupied d-orbitals, slowed the electrocatalytic process. In this presentation we will discuss in details these structure property correlation and other factors influencing the electrocatalytic activity. We will also discuss how nanostructuring of the electrocatalysts on the other hand, increases the catalytic efficiency manifold by increasing the functional surface area for catalytic activity. Electrochemical measurements as well catalyst synthesis and processing will be discussed in details in this presentation.

Journal of The Electrochemical Society, 2022

Rare earth elements (REEs) extraction via conventional technologies is exceedingly energy and env... more Rare earth elements (REEs) extraction via conventional technologies is exceedingly energy and environmentally intensive. New efficient and sustainable technologies for REE extraction from primary and secondary resources would be extremely beneficial. This research demonstrated a novel low-temperature electrochemical extraction process for extracting REEs from lignite coal ash (LCA) solutions. The LCA contained 17 different REEs with a concentration ranging from 13 to 1645 ppm. The LCA solution mixed with ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate (BMITF) was used for extracting REEs at different electrochemical potentials. The ICP-MS analysis confirmed an overall 26% REEs recovery from the LCA solution with 16 out of the 17 REEs successfully extracted from the LCA solution. This study shows an environmentally benign and energy-efficient REE extraction process that is suitable for coal and coal byproducts.

Cobalt telluride has been identified as an efficient multifunctional electrocatalyst for oxygen a... more Cobalt telluride has been identified as an efficient multifunctional electrocatalyst for oxygen and hydrogen evolution reactions and oxygen reduction reaction in alkaline medium. Both hydrothermally synthesized and electrodeposited, CoTe and CoTe2 show efficient electrocatalytic activities. CoTe shows better efficiency for OER with a low Tafel slope (43.8 mV dec-1) and lower overpotential (200 mV) at 10 mA cm-2 compared to CoTe2. DFT studies have also been performed which revealed that CoTe showed higher adsorption energy for intermediate-OH adsorption on the catalyst surface, which corresponds to the catalyst activation step. Comparison of the-OH adsorption energies (Eads) on different catalyst surfaces with the observed overpotential also revealed that this Eads can be used as an appropriate descriptor for benchmarking catalytic efficiencies. Both CoTe and CoTe2 exhibited improved OER catalytic efficiency compared to Co3O4, confirming the primary hypothesis that decreasing anion electronegativity enhances catalytic efficiency by virtue of increasing lattice covalency around the catalytically active site. The difference in OER catalytic activity between CoTe and CoTe2 could be explained from fundamental materials chemistry concepts by comparing their lattice structures which showed different packing density of catalytically active Co sites as well as varying unsaturation of Co-Terminated surfaces. Band structure calculations also corroborated such differences and could potentially explain the difference in activity due to observed differences in electron density distribution around the catalytically active Co site. The cobalt telluride compositions also showed moderate HER and ORR activity in alkaline medium, making them trifunctional catalysts which can be used in practical devices. Both CoTe and CoTe2 showed extensive functional and compositional stability for OER, HER, and ORR, under continuous operation in alkaline medium for over 24 h with less than 5% degradation of current density. The excellent compositional stability of each catalyst was revealed by detailed electrochemical measurements and surface and bulk analytical characterizations, which confirmed that there was no catalyst leaching even with long-Term operation and no other impurity enrichment in the electrolyte

Mikrochimica Acta, Jul 11, 2020

A simple binary copper selenide, CuSe nanostructure, has been investigated as electrochemical sen... more A simple binary copper selenide, CuSe nanostructure, has been investigated as electrochemical sensor for dopamine detection. The hydrothermally synthesized and electrodeposited CuSe nanostructures showed high sensitivity for dopamine detection with low limit of detection (LOD). A sensitivity of 26 μA/μM.cm 2 was obtained with this electrochemical sensor which is ideal to detect even small fluctuations in the transient dopamine concentration. Apart from high sensitivity and low LOD, the dopamine oxidation on the catalyst surface also occurred at a low applied potential (< 0.18 V vs Ag|AgCl), thereby significantly increasing selectivity of the process specifically with respect to ascorbic and uric acids, which are considered to be the most prominent interferents for dopamine detection. Electrochemical redox tunability of the catalytic Cu center along with low coordination geometry is believed to enhance the rate of dopamine attachment and oxidation on the catalyst surface thereby reducing the applied potential. The presence of Cu also increases conductivity of the catalyst composite which further improves the charge transfer thus increasing the sensitivity of the device. This is the first report of electrochemical dopamine sensing with a simple binary selenide comprising earth-abundant elements and can have large significance in designing efficient sensors that can be transformative for understanding neurodegenerative diseases further.

Meeting abstracts, 2017

Water electrolysis leading to generation of oxygen and hydrogen, has been one of the most promisi... more Water electrolysis leading to generation of oxygen and hydrogen, has been one of the most promising routes towards sustainable alternative energy generation and storage, with applications ranging from metal-air batteries, fuel cells, to solar-to-fuel energy conversion systems. Oxygen and Hydrogen evolution reaction (OER and HER respectively) are the two half reactions for water electrolysis, amongst which OER is the most challenging uphill process with a high electron count. Hence, designing efficient catalysts for OER process from earth-abundant resources has been one of the primary concerns for advancing this field. Recently transition metal chalcogenides has been identified as efficient OER electrocatalysts. We have synthesized a plethora of transition metal selenides including those based on Ni, Ni-Fe, Co, and Ni-Co, which show high catalytic efficiency characterized by low onset potential and overpotential at 10 mA/cm2 [Ni3Se2 - 200 - 290 mV; Co7Se8 - 260 mV; FeNi2Se4-NrGO - 170 mV (NrGO - N-doped reduced graphene oxide); NiFe2Se4 - 210 mV; NiCo2Se4 - 190 mV]. We have proposed the idea that one of the primary reasons these selenides show a much better OER catalytic activity is due to increasing covalency in the metal-selenium bond compared to the oxides caused by decreasing electronegativity of the anion, which in turn leads to variation of chemical potential around the transition metal center, specifically, lowering the Ni2+ --&amp;gt; Ni3+ oxidation potential (Ni3+ being the actually catalytically active species). In this presentation we will highlight the importance of this increasing covalency in enhancing the catalytic activity with the help of experimental evidence in selenide compositions ranging from binary Ni-selenides (Ni3Se2, NiSe2, NiSe), ternary mixed metal selenides (Ni-Co-Se, Ni-Fe-Se) as well as seleno-based molecular complex containing NiSe4 tetrahedral core. We will illustrate how the Ni(II) --&amp;gt; Ni(III) oxidation potential is indeed lowered within the selenide coordination compared to the oxide, in pure single crystals of the seleno-based coordination complex which is devoid of any surface impurities and adsorbates. We will also emphasize the lattice-plane-dependent catalytic activity through the example of electrodeposited NiSe2 which shows that if grown along the &amp;lt;311&amp;gt; direction exposing the Ni-rich terminating lattice plane, this catalyst can exhibit lowest overpotential at 10 mA/cm2 (140 mV) that has been reported so far for OER in alkaline medium. All of these selenide electrocatalysts has been characterized with pxrd, SEM, TEM, Raman, XPS, EDS and detailed electrochemical studies including LSV, CV, chronoameprometry, chronopotentiometry, determination of Faradaic efficiency, and ECSA. Through this presentation we will offer insight into possible reasons these selenides outperform most of the known OER electrocatalysts, which will hopefully initiate discussion and efforts to fully understand and utilize their full potential.

Meeting abstracts, 2017

Splitting water to hydrogen and oxygen through hydrogen evolution reaction (HER) and oxygen evolu... more Splitting water to hydrogen and oxygen through hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is basis to feed the fuel cell. OER is a thermodynamically uphill process as it requires higher potential to form O2 molecule. The best known catalysts to split water with low overpotential are the oxides of Ir and Ru. As these catalysts are precious metals there has been intensive research to substitute them with earth-abundant resources. The new catalyst should fulfill the following: (i) the catalyst to split water has to use minimal energy (measured as applied voltage and referred to as overpotential); (ii) should comprise of earth abundant elements; (iii) should be stable; (iv) should be scalable.1 Transition metal oxides have been recently identified as high-efficiency catalysts for oxygen and/or hydrogen evolution reaction. Apart from the oxides there has been reports of sulfide, selenide and nitride based catalysts.2 Although transition metal phosphides has recently gathered attention as HER catalysts,3 very less metal phosphides have been reported as OER electrocatalyst. In this presentation, ultra-small iron phosphide nanoparticles as well nanoparticle composite with reduced graphene oxide (FeP-rGO) has been reported as efficient electrocatalysts for OER under alkaline conditions. FeP nanoparticles require an overpotential of 290 mV @ 10 mAcm-2. It is well known that rGO is a good conductor and a support material for the catalysts. Hence, mixing of FeP nanoparticles with rGO has improved the catalytic efficiency further by reducing the overpotential to 260 mV to achieve 10 mAcm-2 current density4. The FeP nanoparticles and FeP-rGO composite showed the lowest overpotential at 10 mA/cm2 that has observed among the pnictide making these the most-efficient phosphide based OER catalyst till date. The hybrid catalyst showed a low Tafel slope of 50.8 mV/dec. The stability of the catalyst was excellent with 4h of continuous oxygen evolution and the catalytic activity was retained with a similar overpotential @ 10 mAcm-2. The synthesis of hybrid catalysts, detailed characterization, and electrochemical studies including liner scan voltammetry (LSV), choronoamperometry will be discussed in detail. References: Bard, A. J.; Fox, M. A. Artificial photosynthesis solar splitting of water to hydrogen and oxygen. Acc. Chem. Res. 1995, 28, 141-145 Swesi, A. T.; Masud, J.; M. Nath. Nickel selenide as a high-efficiency catalyst for oxygen evolution reaction. Energy Environ. Sci. 2016, 9, 1771-1782. Popczun, E, J.; Read, C, G.; Roske, C, W.; Lewis, N, S.; Schaak, R, E. Highly Active Electrocatalysis of the Hydrogen Evolution Reaction by Cobalt Phosphide Nanoparticles. Angew. Chem. Int. Ed. 2014, 53, 5427 –5430. Masud, J.; Umapathi, S.; Ashokaan, N.; Nath, M. Iron phosphide nanoparticles as an efficient electrocatalyst for the OER in alkaline solution. J. Mater. Chem. A, 2016,4, 9750-9754. Figure 1

Meeting abstracts, 2015

There is a growing interest in oxygen electrode catalysts for oxygen reduction reaction (ORR) and... more There is a growing interest in oxygen electrode catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as they play a key role in a wide range of renewable energy technologies such as fuel cells, metal-air batteries, and water splitting. Nevertheless, the development of highly-active bifunctional catalysts at low cost for both ORR and OER still remains a huge challenge [1]. Herein, we report, a cost effective alternative, viz. cobalt selenide Co­x­Se­­y nanotube and nanorod arrays which shows considerable catalytic activity afor OER and/or ORR., The CoxSey nanostructure arrays were produced by a protocol developed recently in the Nath laboratory [2] which involves confined electrodeposition on lithographically created nanoelectrodes. ORR activity of catalysts were evaluated in acidic medium (Fig. 1). Coating the CoxSey nanostructures with a thin layer of Pt (CoxSey-Pt) also exhibits enhanced catalytic efficiency. ORR current densities of CoxSey and CoxSey-Pt are comparable with Pt which indicate the four electron reduction process of all catalysts. Besides ORR, CoxSey exhibits excellent activity towards OER. The polarization curve (inset of Fig. 1) for CoxSeyin linear sweep voltammetry (LSV) conditions show higher current and earlier onset (ca. 330 mV) of catalytic current in comparison with Pt in 1M KOH solution. Detailed characterization and analysis of ORR/OER activity of catalyst will be presented along with structural and morphological characterization of the active catalyst surface and the relationship between morphology and the observed catalytic activity. References: N.I. Andersen, A. Serov, P. Atanassov Applied Catalysis B: Environmental, 2015, 163, 623. S. Mishra and Manashi Nath, Nano Energy, 2013, 2, 1207 Figure 1

Meeting abstracts, 2016

Transition metal chalcogenides has been a heartthrob of solid state chemists owing to the richnes... more Transition metal chalcogenides has been a heartthrob of solid state chemists owing to the richness of properties they exhibit as well as their structure-property correlation. In addition to their viable optoelectronic properties, it has been recently observed that some of these transition metal chalcogenide (especially selenides) show high electrocatalytic activities for oxygen evolution/reduction reactions (OER/ORR respectively) and hydrogen evolution reaction (HER). Recently we have formulated some new transition metal chalcogenide based compositions which show an enhanced catalytic activity for OER based on their d-electron occupancy and structural parameters.1 Among these the Ni-based selenide thin films and nanostructures show much better catalyst activity along with lower onset potential for O2 evolution outperforming the state-of-the-art precious metal based catalysts. It was also observed that doping other transitional metals in the Nickel selenide matrix led to enhancing catalyst efficiency. The catalysts were synthesized mainly through electrodeposition on different substrates like Au-coated glass, Au-coated Si as well as glassy carbon (GC). The nanostructured catalysts were made through chemical vapor deposition (CVD) and solvothermal reaction. In a separate approach nanorod and nanotube arrays of these electrocatalysts were grown through electrodeposition on lithographically patterned nanoelectrodes. Nanostructuring typically led to much better efficiency with low catalyst volume, with the nanorod/nanotube pattern producing the highest activity with lowest electrode coverage with the active material. The catalytic activities for OER, ORR and HER were investigated through detailed electrochemical measurements including linear scale voltammetry, chronoamperometry, Tafel slope analysis as well as determination of Faradaic efficiency through rotating ring disk electrode studies. Interestingly some of these selenides showed bifunctional or trifunctional nature showing efficient catalytic activity for OER-HER and OER-HER-ORR processes, respectively. In this talk we will present a systematic study of the selenide based electrocatalysts including binary (NixSey, CoxSey) as well as ternary chalcogenides, Ni xMy Sen (M = Fe, Co, Mn, Al) and investigating their catalytic activities for OER, HER, and ORR reactions. We will also discuss the effect of d-electron counts, electronic structure and morphology on the catalytic efficiency. References Swesi, A.; Masud, J.; Nath, M. Energy Environ. Sci. 2015 doi: 10.1039/C5EE02463C.

ACS omega, Jun 26, 2019

Developing Nonenzymatic glucose biosensors has recently been at the center of attention owing to ... more Developing Nonenzymatic glucose biosensors has recently been at the center of attention owing to their potential application in implantable and continuous glucose monitoring systems. In this article, nickel telluride nanostructure with the generic formula of Ni 3 Te 2 has been reported as a highly efficient electrocatalyst for glucose oxidation, functional at a low operating potential. Ni 3 Te 2 nanostructures were prepared by two synthesis methods, direct electrodeposition on the electrode and hydrothermal method. The electrodeposited Ni 3 Te 2 exhibited a wide linear range of response corresponding to glucose oxidation exhibiting a high sensitivity of 41.615 mA cm −2 mM −1 and a low limit of detection (LOD) of 0.43 μM. The hydrothermally synthesized Ni 3 Te 2 , on the other hand, also exhibits an ultrahigh sensitivity of 35.213 mA cm −2 mM −1 and an LOD of 0.38 μM. The observation of high efficiency for glucose oxidation for both Ni 3 Te 2 electrodes irrespective of the synthesis method further confirms the enhanced intrinsic property of the material toward glucose oxidation. In addition to high sensitivity and low LOD, Ni 3 Te 2 electrocatalyst also has good selectivity and long-term stability in a 0.1 M KOH solution. Since it is operative at a low applied potential of 0.35 V vs Ag|AgCl, interference from other electrochemically active species is reduced, thus increasing the accuracy of this sensor.

Journal of Materials Chemistry B, 2019

A CoNi2Se4–rGO nanocomposite fabricated on Ni foam shows excellent efficiency for non-enzymatic g... more A CoNi2Se4–rGO nanocomposite fabricated on Ni foam shows excellent efficiency for non-enzymatic glucose sensing at low applied potential.

ACS Catalysis, Jul 25, 2018

Designing high efficiency electrocatalysts for water oxidation has become an increasingly importa... more Designing high efficiency electrocatalysts for water oxidation has become an increasingly important concept in the catalysis community due to its implications in clean energy generation and storage. In this respect transition metal doped mixed metal selenides incorporating

Social Science Research Network, 2023

TechConnect Briefs, Oct 18, 2021

Meeting abstracts, Sep 1, 2016

First raw transition metal-based chalcogenides (FRTMCs) are promising devices for next generation... more First raw transition metal-based chalcogenides (FRTMCs) are promising devices for next generation to serve as effective substitutes for the Pt-based electrocatalysts in fuel cell systems. OER and HER are considered to be clean and sustainable energy technology and an alternative for fossil fuels. However, OER involving a complex 4 electron process, has several steps that have large reaction barriers, which lead to large required overpotentials. Identifying more-efficient, stable and earth-abundant catalysts for water splitting has long been investigated. The planar configuration of FRTMCs could lead to robust integration for electronic devices. Nanostructured electroactive materials that are fabricated in-plane FRTMCs have attracted great attentions as a kind of storage energy material due to its electrochemistry properties. Recently we have observed that Ni-chalcogenide (Ni3Se2) is superior to the precious transition metal oxide-based electrocatalysts in terms of onset overpotential for O2 evolution as well as overpotential to reach a current density of 10 mA cm-2. With the onset of decreasing particle size to nanometric scale, electrodeposition techniques have provided an alternative route to obtain a variety of new nanomaterials with improved and well controlled properties. The improvement of properties of the metallic composites is dependent mainly on the morphology of materials. Morphology-controllable Ni3Se2 films were successfully prepared by electrodepositing Ni3Se2 film on Au substrate and following by electrochemical dissolution. In electrochemical dissolution process, Ni3Se2 phase is well-preserved and porous structure formed. This technology is a promising way to fabricate other porous materials. A porous Ni3Se2 film showed an enhanced OER catalytic performance in comparison with the as-deposited Ni3Se2 film. The results proved that the OER catalytic performance of porous Ni3Se2 film delivers the highest activity. Introduction of pores to the catalyst material by the electrochemical dissolution is availability for improve the electrochemical performance of the material for OER electrocatalysts. The catalytic efficiency of the proposed catalysts was investigated through linear scan voltammetry (LSV), chronoamperommetry and double layer capacitance. Utilizing rotating ring disc electrode (RRDE) assemblies, the kinetics of OER process between various catalysts as well as the Faradaic efficiency were studied. The catalytic activity of the proposed novel compound (Ni3Se2) was also compared to the outstanding electrocatalysts for OER under conditions relevant to an integrated solar water-splitting device which have been reported so far. The synthesis, characterization, catalytic activity and advancement of the field will be presented in details.

Energy & Fuels, Feb 12, 2021

Recently, nickel-selenide- and -telluride-based electrocatalysts have shown promising results tow... more Recently, nickel-selenide- and -telluride-based electrocatalysts have shown promising results toward water electrolysis, exhibiting very low overpotential. However, a major challenge for these chal...

Advanced sustainable systems, Sep 22, 2017

Water splitting reaction using earth‐abundant and environmentally benign catalysts is critical fo... more Water splitting reaction using earth‐abundant and environmentally benign catalysts is critical for renewable energy generation and storage. Herein a hybrid composite, FeNi2Se4 nanoparticles supported on nitrogen doped reduced graphene oxide (FeNi2Se4–NrGO) is reported as an efficient and dependable bifunctional electrocatalyst for oxygen evolution and oxygen reduction reactions (OER and ORR, respectively) under alkaline conditions. While FeNi2Se4 nanoparticles themselves show good catalytic activity for water oxidation, the constructed hybrid nanocomposite with NrGO as the supporting matrix show enhanced catalytic activity with a small overpotential of 170 mV @ 10 mA cm−2, small Tafel slope of 62.1 mV per decade, and high current density. The ORR catalytic activity of the nanocomposite catalyst is also good with an onset potential of 0.93 V. This is possibly due to the synergistic chemical coupling effects between the FeNi2Se4 and NrGO matrix. Chronoamperometric studies show that the catalyst is stable under conditions of continuous O2 evolution and reduction with very less degradation. Apart from reporting highly efficient OER–ORR bifunctional catalyst, this study also provides more proof for the effect of anion coordination on the catalyst performance, as well as the synergistic role of nanoscale interactions between the catalyst particles and graphene matrix to enhance catalytic activity.

ACS energy letters, Apr 18, 2016

Co 7 Se 8 nanostructures electrodeposited on glassy carbon (GC) electrodes show high efficiency f... more Co 7 Se 8 nanostructures electrodeposited on glassy carbon (GC) electrodes show high efficiency for oxygen reduction reaction (ORR) with high methanol tolerance as compared to Pt electrocatalysts. In the presence of methanol, the onset potential for the ORR at Pt/GC is shifted from 0.931 V (vs reversible hydrogen electrode (RHE)) to 0.801 V (vs RHE), whereas it remains the same (0.811 V vs RHE) at Co 7 Se 8 /GC in the presence and absence of methanol in 0.5 M H 2 SO 4 solution. The Co 7 Se 8 /GC electrodes also showed high cyclability in the presence of methanol, with no degradation of catalytic performance. It is also noteworthy that the Co 7 Se 8 /GC exhibited exclusively a four-electron reduction pathway for ORR and very low H 2 O 2 yield in acidic electrolyte. The admirable performance of Co 7 Se 8 /GC catalyst along with its cost-effective nature holds great potential for application in direct methanol fuel cells.

Meeting abstracts, Apr 15, 2017

The development of a highly active catalyst for water splitting to produce oxygen and hydrogen fu... more The development of a highly active catalyst for water splitting to produce oxygen and hydrogen fuels is in rising demand to fulfill the increasing human need for clean and renewable energy. However, the most crucial step for efficient electrocatalytic water splitting is the oxygen evolution reaction (OER) that takes place at the anode. Traditionally, metal oxides have been introduced for this purpose however, recent developments have shown that transition metal selenides also shows better catalytic activity towards OER surpassing most of the conventional oxide electricatalysts. Herein we present how the family of chalcogenide electrocatalysts can be extended to transition metal tellurides and we will present the OER electrocatalytic activity of the first ever telluride, Ni3Te2 synthesized by hydrothermal reactions as well as electrodeposition technique. This catalyst show an overpotential of 170 mV at 10 mA/cm2 during the OER electrocatalytic activity in 1 M KOH, which is one of the lowest reported value till date and that highlight the high performance of this catalyst. Additionally, this catalyst also shows a high catalytic activity towards hydrogen evolution reaction (HER) and it only requires 250 mV over potential to achieve a current density of 10 mA/cm2 during HER conditions and that makes it a bifunctional elecrocatalyst. We will present the synthesis, characterization and electrochemical investigations of this new catalyst and additionally, we will also discuss the stability of this catalyst during long term OER conditions.

Journal of The Electrochemical Society, Jan 27, 2022

Rare earth elements (REEs) extraction via conventional technologies is exceedingly energy and env... more Rare earth elements (REEs) extraction via conventional technologies is exceedingly energy and environmentally intensive. New efficient and sustainable technologies for REE extraction from primary and secondary resources would be extremely beneficial. This research demonstrated a novel low-temperature electrochemical extraction process for extracting REEs from lignite coal ash (LCA) solutions. The LCA contained 17 different REEs with a concentration ranging from 13 to 1645 ppm. The LCA solution mixed with ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate (BMITF) was used for extracting REEs at different electrochemical potentials. The ICP-MS analysis confirmed an overall 26% REEs recovery from the LCA solution with 16 out of the 17 REEs successfully extracted from the LCA solution. This study shows an environmentally benign and energy-efficient REE extraction process that is suitable for coal and coal byproducts.

Meeting abstracts, May 1, 2019

Diabetes has long been recognized as one of the leading causes of death in the United States and ... more Diabetes has long been recognized as one of the leading causes of death in the United States and worldwide second only to cancer and heart-related ailments. Diabetes is a silent killer and early stage diagnosis and controlling blood glucose level is the key to maintain and control the disease. Blood glucose levels are typically monitored with the help of glucose detection through electrochemical oxidation of glucose to gluconic acid or gluconolactone. Typically, in conventional glucose detectors, enzyme-based electrochemical sensors are used which suffers from several critical challenges including reduced efficiency and sensitivity, reduced shelf lives, lack of long-term stability (due to enzyme denaturation), high fabrication cost (due to complex enzyme purification steps), and high detection limit (due to less efficient indirect electron transfer). In this presentation we will discuss about designing high-efficiency direct glucose electrochemical sensors from transition metal chalcogenides using principles of materials chemistry, specifically, tuning the redox potential of the transition metal site. We will present several examples of high-efficiency chalcogenide based glucose sensors including CoNi2Se4-rGO nanocomposite, Ni3Te2, Cu2Se, and NiSe. These chalcogenide based electrocatalysts show high activity for glucose oxidation at very low potential (~0.35 - 0.45 V vs Ag|AgCl) with high sensitivity (exceeding 18 mA/mM cm2) and low limit of detection (LOD). These chalcogenides can offer direct electron transfer pathways over a wide potential range leading to much higher sensor efficiency. Moreover, the sensing performance of these electrocatalysts were tested in presence of common interferents present in physiological samples such as dopamine, ascorbic acid, lactose, etc., where it showed that glucose sensing was unaffected primarily because at such low potential, other biomolecules are not affected. In fact, the ability to oxidize glucose at such low potential is considered to be one of the most prominent novelty of these chalcogenide electrocatalysts, and the glucose oxidation potential of 0.35V (CoNi2Se4) is one of the lowest reported potential till date. The reason for such high activity for glucose oxidation was investigated through a series of experiments designed to alter the redox potential of the transition metal site either by changing the anion (selenide to telluride), transition metal doping (NiSe vs CoNi2Se4), or changing the d-electron occupancy (NiSe vs Cu2Se). Through these measurements we observed that on changing the electronegativity of the anion from selenide to telluride, the glucose oxidation potential could be reduced further due to transition metal site oxidation occurring at a lower potential. The transition metal site oxidation can be considered as the catalyst activation step which initiates the glucose oxidation. Transition metal doping at the active site also helped to redistribute the electron density thereby influencing catalyst activation and subsequent glucose oxidation steps. Interestingly, using highly occupied d-orbitals, slowed the electrocatalytic process. In this presentation we will discuss in details these structure property correlation and other factors influencing the electrocatalytic activity. We will also discuss how nanostructuring of the electrocatalysts on the other hand, increases the catalytic efficiency manifold by increasing the functional surface area for catalytic activity. Electrochemical measurements as well catalyst synthesis and processing will be discussed in details in this presentation.

Journal of The Electrochemical Society, 2022

Rare earth elements (REEs) extraction via conventional technologies is exceedingly energy and env... more Rare earth elements (REEs) extraction via conventional technologies is exceedingly energy and environmentally intensive. New efficient and sustainable technologies for REE extraction from primary and secondary resources would be extremely beneficial. This research demonstrated a novel low-temperature electrochemical extraction process for extracting REEs from lignite coal ash (LCA) solutions. The LCA contained 17 different REEs with a concentration ranging from 13 to 1645 ppm. The LCA solution mixed with ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate (BMITF) was used for extracting REEs at different electrochemical potentials. The ICP-MS analysis confirmed an overall 26% REEs recovery from the LCA solution with 16 out of the 17 REEs successfully extracted from the LCA solution. This study shows an environmentally benign and energy-efficient REE extraction process that is suitable for coal and coal byproducts.

Cobalt telluride has been identified as an efficient multifunctional electrocatalyst for oxygen a... more Cobalt telluride has been identified as an efficient multifunctional electrocatalyst for oxygen and hydrogen evolution reactions and oxygen reduction reaction in alkaline medium. Both hydrothermally synthesized and electrodeposited, CoTe and CoTe2 show efficient electrocatalytic activities. CoTe shows better efficiency for OER with a low Tafel slope (43.8 mV dec-1) and lower overpotential (200 mV) at 10 mA cm-2 compared to CoTe2. DFT studies have also been performed which revealed that CoTe showed higher adsorption energy for intermediate-OH adsorption on the catalyst surface, which corresponds to the catalyst activation step. Comparison of the-OH adsorption energies (Eads) on different catalyst surfaces with the observed overpotential also revealed that this Eads can be used as an appropriate descriptor for benchmarking catalytic efficiencies. Both CoTe and CoTe2 exhibited improved OER catalytic efficiency compared to Co3O4, confirming the primary hypothesis that decreasing anion electronegativity enhances catalytic efficiency by virtue of increasing lattice covalency around the catalytically active site. The difference in OER catalytic activity between CoTe and CoTe2 could be explained from fundamental materials chemistry concepts by comparing their lattice structures which showed different packing density of catalytically active Co sites as well as varying unsaturation of Co-Terminated surfaces. Band structure calculations also corroborated such differences and could potentially explain the difference in activity due to observed differences in electron density distribution around the catalytically active Co site. The cobalt telluride compositions also showed moderate HER and ORR activity in alkaline medium, making them trifunctional catalysts which can be used in practical devices. Both CoTe and CoTe2 showed extensive functional and compositional stability for OER, HER, and ORR, under continuous operation in alkaline medium for over 24 h with less than 5% degradation of current density. The excellent compositional stability of each catalyst was revealed by detailed electrochemical measurements and surface and bulk analytical characterizations, which confirmed that there was no catalyst leaching even with long-Term operation and no other impurity enrichment in the electrolyte