Uday Azad - Academia.edu (original) (raw)

Papers by Uday Azad

Research paper thumbnail of MOF derived Co/C and Co3O4/C polyhedron for hydrogen evolution reaction

ADVANCES IN BASIC SCIENCE (ICABS 2019), 2019

We have synthesized MOF derived cobalt-polyhedron by facile method and the same was characterized... more We have synthesized MOF derived cobalt-polyhedron by facile method and the same was characterized by various spectroscopic and analytical techniques. Prepared polyhedronhas rhombic dodecahedron shape and shows efficient electrocatalytic activity for hydrogen evolution in 0.5M H2SO4 solution. Acid washed (AW) samples shows better HER activity as compared to their only heat-treated counterpart. 900AW show maximum HER activity (Tafel slope 86.9 mV dec-1). It was found that temperature as well as porosity plays very important role in HER.We have synthesized MOF derived cobalt-polyhedron by facile method and the same was characterized by various spectroscopic and analytical techniques. Prepared polyhedronhas rhombic dodecahedron shape and shows efficient electrocatalytic activity for hydrogen evolution in 0.5M H2SO4 solution. Acid washed (AW) samples shows better HER activity as compared to their only heat-treated counterpart. 900AW show maximum HER activity (Tafel slope 86.9 mV dec-1). ...

Research paper thumbnail of Electrochemical biosensors for monitoring of bioorganic and inorganic chemical pollutants in biological and environmental matrices

Microbial Biodegradation and Bioremediation

Research paper thumbnail of Lanthanide based double perovskites: Bifunctional catalysts for oxygen evolution/reduction reactions

International Journal of Hydrogen Energy

Research paper thumbnail of In situ transformed three heteroleptic Co(II)-MOFs as potential electrocatalysts for the electrochemical oxygen evolution reaction

Electrochimica Acta

Abstract Three Co(II)-MOFs, catena- [(diaqua-(μ2-bqdc-κO,O)-(phen-κN,N)-cobalt (II)] (1), { [Co(p... more Abstract Three Co(II)-MOFs, catena- [(diaqua-(μ2-bqdc-κO,O)-(phen-κN,N)-cobalt (II)] (1), { [Co(pa)(4,4′-bipy)(H2O) (CH3OH)]•DMF}n (2) and [Co(ia)(bpe)0.5(H2O)]n (3), (H2bqdc=2,2-biquinoline-4,4′-dicarboxylic acid, phen = 1,10-phenanthroline), (H2pa = pamoic acid) (H2ia = itaconic acid, bpe = 1,2-bi(4-pyridyl)ethane) have been re-synthesized and thoroughly characterized by FT-IR, PXRD, SEM, EDX, HRTEM, BET surface area and UV/vis techniques. The objective of choosing three Co(II)-MOFs 1-3 composed of different ligands and having 1D, 2D and 3D structures, respectively, was to have deep insights into role of linked ligands and the structural morphology toward electrocatalytic performance. MOFs 1-3 have been examined as electrocatalysts for water oxidation and comparative assessments revealed their catalytic performance in the order 2 > 3 ≈ 1. MOF 2 shows the best electrocatalytic activity for OER, which could be due to the higher amount of cobalt present in MOF-2, faster electron transfer kinetics and higher effective electrode surface area. The onset potential of MOF 2 was comparable or less as compared to benchmark catalysts IrO2 and Pt/C. Overall studies strongly suggest that MOF 2 could be promising materials for replacement of commercial high-cost electrode material.

Research paper thumbnail of Synthesis of colloidal MoSx nanoparticles and their transformation into carbon supported MoS2 nanocomposite

ADVANCES IN BASIC SCIENCE (ICABS 2019)

Research paper thumbnail of Studies on some spinel oxides based electrocatalysts for oxygen evolution and capacitive applications

Electrochimica Acta

Abstract In the present work the role of oxygen vacancies in improvement of catalytic activity in... more Abstract In the present work the role of oxygen vacancies in improvement of catalytic activity in spinel oxides is reported and further explored for oxygen evolution and capacitive applications. Sol-gel method is used to prepare nickel ferrite (NFO) and for the first time cobalt doped nickel ferrite (CFO and CNFO) spinel oxides for electrocatalytic studies. As prepared NFO. CFO and CNFO are characterized by various spectroscopic and microscopic techniques and the same are used for supercapacitive application as well as for oxygen evolution reaction (OER). The oxygen vacancy is studied by EDAX and XPS analysis and observed that the vacancies are playing crucial role in OER application.

Research paper thumbnail of Study of the Capacitive Behavior of MOF-Derived Nanocarbon Polyhedra

Research paper thumbnail of Vanadium doped few-layer ultrathin MoS2 nanosheets on reduced graphene oxide for high-performance hydrogen evolution reaction

RSC Advances

In this paper, we demonstrate a facile solvothermal synthesis of a vanadium(v) doped MoS2-rGO nan... more In this paper, we demonstrate a facile solvothermal synthesis of a vanadium(v) doped MoS2-rGO nanocomposites for highly efficient electrochemical hydrogen evolution reaction (HER) at room temperature.

Research paper thumbnail of Facile Synthesis of MoSx and MoSx -rGO Composite: Excellent Electrocatalyst for Hydrogen Evolution Reaction

ChemistrySelect

In this work, one pot synthetic methodology was developed, wherein simple purging of H2S gas into... more In this work, one pot synthetic methodology was developed, wherein simple purging of H2S gas into a solution/dispersion of polyoxometalates in the absence as well as presence of reduced graphene oxide (rGO) at room temperature resulted in the formation of MoSx and MoSx-rGO composites. Powder XRD, TEM, EDS elemental analysis, TGA, and XPS study reveal that as prepared samples mainly consist of nanocrystalline MoS3 particles whereas annealed samples mainly contain few layers of MoS2 nanosheets. Annealed samples exhibit better electrocatalytic activity towards hydrogen evolution reaction (HER) as compared to the as-prepared samples. Among all the annealed samples, MoS2-rGO nanocomposite exhibits superior catalytic activity for HER with lower onset overpotential and higher current density, as compared to other conventional MoS2. The Tafel slope of 41.7 mV/decade for MoS2-rGO nanocomposite signifies that MoS2 catalyzed HER follows the Volmer-Heyrovsky mechanism wherein, electrochemical desorption of hydrogen is the rate-limiting step. Moreover, the integration of few layers of MoS2 and rGO enable remarkable long-term electrochemical stability and showing negligible change in the current density even after 3000 cycles.

Research paper thumbnail of Electrocatalytic Oxygen Reduction by Dopant-free, Porous Graphene Aerogel

Research paper thumbnail of Synthesis, structure, photoluminescence and electrochemical properties of mononuclear Ag(I) and polymeric Zn(II) complexes of potassium 4-methyl piperazine-1-carbodithioate

Journal of Molecular Structure

Abstract New heteroleptic mononuclear complex [Ag(mpdtc)(PPh3)2] (1) and homoleptic polymeric com... more Abstract New heteroleptic mononuclear complex [Ag(mpdtc)(PPh3)2] (1) and homoleptic polymeric complex [Zn(mpdtc)2]n (2) have been synthesized from potassium 4-methyl piperazine-1-carbodithioate [K(mpdtc)]. The complexes have been characterized by elemental analyses, IR, NMR, UV–vis, thermal, cyclic voltammetry, and X-ray diffraction technique. Complexes 1 and 2 are fluorescent materials and exhibit emission maxima at around 32000 cm−1 upon excitation at 39000 cm−1. Thermogravimetric analysis of complexes as investigated by TG-DTA, suggests the formation of their respective metal sulfides as final thermally stable chemical entities. Electrochemical studies of silver(I) complex reveals the formation of silver nanoparticle which catalyses the oxidation of the ligand. The Ag(I) ion adopts a distorted tetrahedral geometry in complex 1 and the geometry around Zn(II) ion in complex 2 is in halfway between square planar and trigonal bipyramidal. The crystal structures of complexes are stabilized by intermolecular C-H…S interactions.

Research paper thumbnail of Syntheses of nickel sulfides from 1,2-bis(diphenylphosphino)ethane nickel(II)dithiolates and their application in the oxygen evolution reaction

International Journal of Hydrogen Energy

Abstract In this work, four heteroleptic Ni(II)dppe dithiolates complexes, [Ni(NED)(dppe)] (Ni-NE... more Abstract In this work, four heteroleptic Ni(II)dppe dithiolates complexes, [Ni(NED)(dppe)] (Ni-NED), [Ni(ecda)(dppe)] (Ni-ecda), [Ni(i-mnt)(dppe)] (Ni-i-mnt) and [Ni(cdc)(dppe)] (Ni-cdc) (dppe = 1,2-bis(diphenylphosphino)ethane; NED = 1-nitroethylene-2,2-dithiolate; ecda = 1-ethoxycarbonyl-1-cyanoethyelene-2,2-dithiolate; i-mnt = 1,1-dicyanoethylene-2,2-dithiolate and cdc = cyanodithioimidocarbonate), have been synthesized and characterized by analytical and spectroscopic techniques (Elemental analysis, vibrational, electronic absorption and multinuclear NMR spectroscopy). Structural characterization of all the four complexes by single crystal X-ray diffraction study suggests distortion in regular square planar geometry at Ni(II) center by coordination with two phosphorus of the dppe and two sulfur of the dithiolate ligands, respectively. The decomposition of all four complexes have been done to produce nickel sulfides and the resulting nickel sulfides have been utilized for electrocatalytic oxygen evolution reaction (OER). The nickel sulfide obtained by decomposing Ni-cdc shows best activity with overpotential η = 222 mV at j = 10 mA cm−2 and a Tafel slope of 44.2 mV dec−1 while other catalysts shows η > 470 mV at j = 5 mA cm−2 and η > 600 mV at j = 10 mA cm−2 at loading of 1.3 mg cm−2.

Research paper thumbnail of Copper(i) tertiary phosphine xanthate complexes as single source precursors for copper sulfide and their application in the OER

New Journal of Chemistry

Three heteroleptic bis(triphenylphosphine)copper(i) methyl pyridyl xanthate complexes used as sin... more Three heteroleptic bis(triphenylphosphine)copper(i) methyl pyridyl xanthate complexes used as single source precursors for copper sulfide and the resulting copper sulfides have been utilized for the electrocatalytic oxygen evolution reaction.

Research paper thumbnail of Yttrium Copper Titanate as a Highly Efficient Electrocatalyst for Oxygen Reduction Reaction in Fuel Cells, Synthesized via Ultrafast Automatic Flame Technique

Scientific Reports

Replacing platinum (Pt) metal-based electrocatalysts used in the oxygen reduction reaction (ORR) ... more Replacing platinum (Pt) metal-based electrocatalysts used in the oxygen reduction reaction (ORR) in fuel cells is an important research topic due to the high cost and scarcity of Pt, which have restricted the commercialization of these clean-energy technologies. The ABO 3-type perovskite family of an ACu 3 Ti 4 O 12 (A = Ca, Y, Bi, and La) polycrystalline material can serve as an alternative electrocatalyst for the ORR in terms of low-cost, activity, and stability. These perovskite materials may be considered the next generation electro-catalyst for the ORR because of their photocatalytic activity and physical and chemical properties capable of containing a wide range of A-and B-site metals. This paper reports the ORR activity of a new Y 2/3 Cu 3 Ti 4 O 12 perovskite, synthesized via a rapid and facile automatic flame synthesis technique using rotating disk electrode (RDE) measurements. Y 2/3 Cu 3 Ti 4 O 12 /C has superior ORR activity, stability, and durability compared to commercial Pt/C. The results presented in this article will provide the future perspectives to research based on ACu 3 Ti 4 O 12 (A = Ca, Y, Bi, Sm, Cd, and La) perovskite as the next generation electro-catalyst for the ORR in various electrochemical devices, such as fuel cells, metal-air batteries, and electrolysis. Fuel cells (FCs) are a new power source via the direct conversion of hydrogen to electricity as a potential replacement for Li-ion batteries systems in terms of safety, high efficiency, renewable sources, and environmental friendliness 1. The major obstacle to the commercialization of fuel cells is the high cost, poor stability, and slow kinetics of the oxygen reduction reaction (ORR) of platinum and platinum-based electrocatalysts in fuel-cell electrodes 2. Thus far, the best electrocatalysts for the ORR of the cathode are carbon-supported Pt and/or its composites 3-8. High cost and scarcity of platinum requires either use of noble metal with an increased efficiency or the utilization of non-precious electrocatalysts for commercialization on a large scale. In addition, Pt-based electrocatalysts suffer from methanol crossover and CO poisoning 9. The ORR is not only an essential electrochemical process in fuel cells, but is also required for other electrochemical technologies, such as metal-air batteries and water electrolysis 10. The ORR takes place through multiple electron transfer in alkaline media. Depending on the nature and electrocatalytic activity of the catalysts, the ORR in alkaline media can occur either via a two electron process to produce HO 2 − or a four electron process to produce OH − (O 2 + 2H 2 O + 4e − → 4OH −) 11. A high ORR overpotential has been the main obstacle to making these technologies viable. Therefore, major efforts have been made to discover cost-effective and efficient ORR catalysts in traditional aqueous media. A general model of the oxygen reduction kinetics in porous electrodes must include oxygen diffusion, oxygen adsorption, or surface reaction on the active sites of the catalyst, charge transfer, and the diffusion of products 12. ABO 3 type perovskite oxides, particularly ACu 3 Ti 4 O 12 (A = Ca, La, Bi, Sm, Cd, and Y), have great potential as low cost, high stability, and better kinetics electro-catalyst and may be considered the next generation electro-catalyst for the ORR because of

Research paper thumbnail of Pd@TTF Tailored Nanostructured Platform: Voltammetric Estimation of Ceftazidime

Research paper thumbnail of Hydrophobicity Effects in Iron Polypyridyl Complex Electrocatalysis within Nafion Thin-Film Electrodes

Phys. Chem. Chem. Phys., 2016

Four polypyridyl redox catalysts Fe(bp)32+, Fe(ph)32+, Fe(dm)32+, and Fe(tm)32+ (with bp, ph, dm,... more Four polypyridyl redox catalysts Fe(bp)32+, Fe(ph)32+, Fe(dm)32+, and Fe(tm)32+ (with bp, ph, dm, and tm representing 2,2′-bipyridine, 1,10-phenanthroline, 4,4′-dimethyl-2,2′-bipyridine, and 3,4,7,8-tetramethyl-1,10-phenanthroline, respectively) are investigated for the electrocatalytic oxidation of three analytes (nitrite, arsenite, and isoniazid).

Research paper thumbnail of Efficient Oxygen Reduction Electrocatalysts Based on Gold Nanocluster-Graphene Composites

ChemElectroChem, 2016

This paper describes the preparation and electrocatalytic activity of nanocomposites composed of ... more This paper describes the preparation and electrocatalytic activity of nanocomposites composed of reduced graphene oxide and Au25 clusters. Well-defined nanocomposites are prepared by coating the surface of reduced graphene oxide with multiple layers of Au25 film, the thickness of which can be precisely controlled according to the preparation conditions. The electrocatalytic activity of the nanocomposites are examined for the reduction of [Ru(NH3)6]3+ and in the oxygen reduction reaction by chronoamperometry and electrochemical impedance spectroscopy as a function of Au25 thickness. Whereas the catalytic rate constants obtained for the reduction of [Ru(NH3)6]3+ are found to be rather constant with varying Au25 thickness, those for the oxygen reduction reaction increased drastically with an increasing number of Au25 layers. This increase can be ascribed to the porous structures generated in the nanocomposites. The porous channels generated in the nanocomposites offer confined space surrounded by electrified surface, greatly enhancing the electrocatalytic activity for the oxygen reduction reaction. Additional rotating disk electrode and rotating ring-disk electrode voltammetry show that the nanocomposites support an efficient four-electron reduction of oxygen.

Research paper thumbnail of Electrochemical determination of nanomolar levels of isoniazid in pharmaceutical formulation using silver nanoparticles decorated copolymer

Electrochimica Acta, 2016

Research paper thumbnail of Selective determination of isoniazid using bentonite clay modified electrodes

Bioelectrochemistry (Amsterdam, Netherlands), 2015

Fe(dmbpy)3(2+) (where dmbpy is 4,4'-dimethyl-2,2'-bipyridine) was immobilized by ion-exch... more Fe(dmbpy)3(2+) (where dmbpy is 4,4'-dimethyl-2,2'-bipyridine) was immobilized by ion-exchange in a bentonite clay film coating on a glassy carbon electrode. Cyclic voltammetry characteristics of the immobilized Fe(dmbpy)3(2+) were stable and reproducible corresponding to the Fe(dmbpy)3(2+/3+) redox process. In the presence of isoniazid (IZ), the electrogenerated in film Fe(dmbpy)3(3+) oxidized IZ efficiently producing large anodic current. This current was linearly proportional to the IZ concentration in the solution. The process was described by an EC' electrocatalysis mechanism allowing for sensitive determination of IZ with a wide linear dynamic concentration range of 10.0μM to 10.0mM. The electrode was tested for its analytical suitability and possible discrimination of interferences by determining IZ in a commercially available pharmaceutical product. The paper reports on a simple, cheap, and easy to fabricate chronoamperometric chemical sensor for determination of ...

Research paper thumbnail of Tris(4,4′-dimethyl-2,2′-bipyridine)iron(II)-Exchanged Nafion for Arsenite Determination in Water Samples

ChemElectroChem, 2013

ABSTRACT A low cost and easy-to-construct electrochemical sensor is fabricated for the determinat... more ABSTRACT A low cost and easy-to-construct electrochemical sensor is fabricated for the determination of arsenite in water by using an Fe(dmbpy)32+-exchanged (dmbpy=4,4′-dimethyl-2,2′-bipyridine) Nafion (Nf) film. Arsenite at a glassy carbon electrode (GCE) coated with the Fe(dmbpy)32+-exchanged Nf film is shown to be electrocatalytically oxidized at lower overpotentials than at a bare GCE, and a tentative mechanism is proposed for the electrocatalytic oxidation. This new electrochemical sensing platform (ESP) exhibits a wide linear calibration range (from 10 μM to 100 mM) with a correlation coefficient above 0.99 for the precise determination of arsenite; the ESP exhibits a detection limit of 10.0 μM for arsenite determination. Utility of the developed sensor is further assured by determining the concentration of arsenite present in standard aqueous samples and in samples from different water sources. Among the several interferences studied, high concentrations of Zn2+ (50 times higher than arsenite) can affect arsenite determination. Kinetic parameters, such as the diffusion coefficient, catalytic rate constant, and so forth, are determined by using chronocoulometry and chronoamperometry techniques.

Research paper thumbnail of MOF derived Co/C and Co3O4/C polyhedron for hydrogen evolution reaction

ADVANCES IN BASIC SCIENCE (ICABS 2019), 2019

We have synthesized MOF derived cobalt-polyhedron by facile method and the same was characterized... more We have synthesized MOF derived cobalt-polyhedron by facile method and the same was characterized by various spectroscopic and analytical techniques. Prepared polyhedronhas rhombic dodecahedron shape and shows efficient electrocatalytic activity for hydrogen evolution in 0.5M H2SO4 solution. Acid washed (AW) samples shows better HER activity as compared to their only heat-treated counterpart. 900AW show maximum HER activity (Tafel slope 86.9 mV dec-1). It was found that temperature as well as porosity plays very important role in HER.We have synthesized MOF derived cobalt-polyhedron by facile method and the same was characterized by various spectroscopic and analytical techniques. Prepared polyhedronhas rhombic dodecahedron shape and shows efficient electrocatalytic activity for hydrogen evolution in 0.5M H2SO4 solution. Acid washed (AW) samples shows better HER activity as compared to their only heat-treated counterpart. 900AW show maximum HER activity (Tafel slope 86.9 mV dec-1). ...

Research paper thumbnail of Electrochemical biosensors for monitoring of bioorganic and inorganic chemical pollutants in biological and environmental matrices

Microbial Biodegradation and Bioremediation

Research paper thumbnail of Lanthanide based double perovskites: Bifunctional catalysts for oxygen evolution/reduction reactions

International Journal of Hydrogen Energy

Research paper thumbnail of In situ transformed three heteroleptic Co(II)-MOFs as potential electrocatalysts for the electrochemical oxygen evolution reaction

Electrochimica Acta

Abstract Three Co(II)-MOFs, catena- [(diaqua-(μ2-bqdc-κO,O)-(phen-κN,N)-cobalt (II)] (1), { [Co(p... more Abstract Three Co(II)-MOFs, catena- [(diaqua-(μ2-bqdc-κO,O)-(phen-κN,N)-cobalt (II)] (1), { [Co(pa)(4,4′-bipy)(H2O) (CH3OH)]•DMF}n (2) and [Co(ia)(bpe)0.5(H2O)]n (3), (H2bqdc=2,2-biquinoline-4,4′-dicarboxylic acid, phen = 1,10-phenanthroline), (H2pa = pamoic acid) (H2ia = itaconic acid, bpe = 1,2-bi(4-pyridyl)ethane) have been re-synthesized and thoroughly characterized by FT-IR, PXRD, SEM, EDX, HRTEM, BET surface area and UV/vis techniques. The objective of choosing three Co(II)-MOFs 1-3 composed of different ligands and having 1D, 2D and 3D structures, respectively, was to have deep insights into role of linked ligands and the structural morphology toward electrocatalytic performance. MOFs 1-3 have been examined as electrocatalysts for water oxidation and comparative assessments revealed their catalytic performance in the order 2 > 3 ≈ 1. MOF 2 shows the best electrocatalytic activity for OER, which could be due to the higher amount of cobalt present in MOF-2, faster electron transfer kinetics and higher effective electrode surface area. The onset potential of MOF 2 was comparable or less as compared to benchmark catalysts IrO2 and Pt/C. Overall studies strongly suggest that MOF 2 could be promising materials for replacement of commercial high-cost electrode material.

Research paper thumbnail of Synthesis of colloidal MoSx nanoparticles and their transformation into carbon supported MoS2 nanocomposite

ADVANCES IN BASIC SCIENCE (ICABS 2019)

Research paper thumbnail of Studies on some spinel oxides based electrocatalysts for oxygen evolution and capacitive applications

Electrochimica Acta

Abstract In the present work the role of oxygen vacancies in improvement of catalytic activity in... more Abstract In the present work the role of oxygen vacancies in improvement of catalytic activity in spinel oxides is reported and further explored for oxygen evolution and capacitive applications. Sol-gel method is used to prepare nickel ferrite (NFO) and for the first time cobalt doped nickel ferrite (CFO and CNFO) spinel oxides for electrocatalytic studies. As prepared NFO. CFO and CNFO are characterized by various spectroscopic and microscopic techniques and the same are used for supercapacitive application as well as for oxygen evolution reaction (OER). The oxygen vacancy is studied by EDAX and XPS analysis and observed that the vacancies are playing crucial role in OER application.

Research paper thumbnail of Study of the Capacitive Behavior of MOF-Derived Nanocarbon Polyhedra

Research paper thumbnail of Vanadium doped few-layer ultrathin MoS2 nanosheets on reduced graphene oxide for high-performance hydrogen evolution reaction

RSC Advances

In this paper, we demonstrate a facile solvothermal synthesis of a vanadium(v) doped MoS2-rGO nan... more In this paper, we demonstrate a facile solvothermal synthesis of a vanadium(v) doped MoS2-rGO nanocomposites for highly efficient electrochemical hydrogen evolution reaction (HER) at room temperature.

Research paper thumbnail of Facile Synthesis of MoSx and MoSx -rGO Composite: Excellent Electrocatalyst for Hydrogen Evolution Reaction

ChemistrySelect

In this work, one pot synthetic methodology was developed, wherein simple purging of H2S gas into... more In this work, one pot synthetic methodology was developed, wherein simple purging of H2S gas into a solution/dispersion of polyoxometalates in the absence as well as presence of reduced graphene oxide (rGO) at room temperature resulted in the formation of MoSx and MoSx-rGO composites. Powder XRD, TEM, EDS elemental analysis, TGA, and XPS study reveal that as prepared samples mainly consist of nanocrystalline MoS3 particles whereas annealed samples mainly contain few layers of MoS2 nanosheets. Annealed samples exhibit better electrocatalytic activity towards hydrogen evolution reaction (HER) as compared to the as-prepared samples. Among all the annealed samples, MoS2-rGO nanocomposite exhibits superior catalytic activity for HER with lower onset overpotential and higher current density, as compared to other conventional MoS2. The Tafel slope of 41.7 mV/decade for MoS2-rGO nanocomposite signifies that MoS2 catalyzed HER follows the Volmer-Heyrovsky mechanism wherein, electrochemical desorption of hydrogen is the rate-limiting step. Moreover, the integration of few layers of MoS2 and rGO enable remarkable long-term electrochemical stability and showing negligible change in the current density even after 3000 cycles.

Research paper thumbnail of Electrocatalytic Oxygen Reduction by Dopant-free, Porous Graphene Aerogel

Research paper thumbnail of Synthesis, structure, photoluminescence and electrochemical properties of mononuclear Ag(I) and polymeric Zn(II) complexes of potassium 4-methyl piperazine-1-carbodithioate

Journal of Molecular Structure

Abstract New heteroleptic mononuclear complex [Ag(mpdtc)(PPh3)2] (1) and homoleptic polymeric com... more Abstract New heteroleptic mononuclear complex [Ag(mpdtc)(PPh3)2] (1) and homoleptic polymeric complex [Zn(mpdtc)2]n (2) have been synthesized from potassium 4-methyl piperazine-1-carbodithioate [K(mpdtc)]. The complexes have been characterized by elemental analyses, IR, NMR, UV–vis, thermal, cyclic voltammetry, and X-ray diffraction technique. Complexes 1 and 2 are fluorescent materials and exhibit emission maxima at around 32000 cm−1 upon excitation at 39000 cm−1. Thermogravimetric analysis of complexes as investigated by TG-DTA, suggests the formation of their respective metal sulfides as final thermally stable chemical entities. Electrochemical studies of silver(I) complex reveals the formation of silver nanoparticle which catalyses the oxidation of the ligand. The Ag(I) ion adopts a distorted tetrahedral geometry in complex 1 and the geometry around Zn(II) ion in complex 2 is in halfway between square planar and trigonal bipyramidal. The crystal structures of complexes are stabilized by intermolecular C-H…S interactions.

Research paper thumbnail of Syntheses of nickel sulfides from 1,2-bis(diphenylphosphino)ethane nickel(II)dithiolates and their application in the oxygen evolution reaction

International Journal of Hydrogen Energy

Abstract In this work, four heteroleptic Ni(II)dppe dithiolates complexes, [Ni(NED)(dppe)] (Ni-NE... more Abstract In this work, four heteroleptic Ni(II)dppe dithiolates complexes, [Ni(NED)(dppe)] (Ni-NED), [Ni(ecda)(dppe)] (Ni-ecda), [Ni(i-mnt)(dppe)] (Ni-i-mnt) and [Ni(cdc)(dppe)] (Ni-cdc) (dppe = 1,2-bis(diphenylphosphino)ethane; NED = 1-nitroethylene-2,2-dithiolate; ecda = 1-ethoxycarbonyl-1-cyanoethyelene-2,2-dithiolate; i-mnt = 1,1-dicyanoethylene-2,2-dithiolate and cdc = cyanodithioimidocarbonate), have been synthesized and characterized by analytical and spectroscopic techniques (Elemental analysis, vibrational, electronic absorption and multinuclear NMR spectroscopy). Structural characterization of all the four complexes by single crystal X-ray diffraction study suggests distortion in regular square planar geometry at Ni(II) center by coordination with two phosphorus of the dppe and two sulfur of the dithiolate ligands, respectively. The decomposition of all four complexes have been done to produce nickel sulfides and the resulting nickel sulfides have been utilized for electrocatalytic oxygen evolution reaction (OER). The nickel sulfide obtained by decomposing Ni-cdc shows best activity with overpotential η = 222 mV at j = 10 mA cm−2 and a Tafel slope of 44.2 mV dec−1 while other catalysts shows η > 470 mV at j = 5 mA cm−2 and η > 600 mV at j = 10 mA cm−2 at loading of 1.3 mg cm−2.

Research paper thumbnail of Copper(i) tertiary phosphine xanthate complexes as single source precursors for copper sulfide and their application in the OER

New Journal of Chemistry

Three heteroleptic bis(triphenylphosphine)copper(i) methyl pyridyl xanthate complexes used as sin... more Three heteroleptic bis(triphenylphosphine)copper(i) methyl pyridyl xanthate complexes used as single source precursors for copper sulfide and the resulting copper sulfides have been utilized for the electrocatalytic oxygen evolution reaction.

Research paper thumbnail of Yttrium Copper Titanate as a Highly Efficient Electrocatalyst for Oxygen Reduction Reaction in Fuel Cells, Synthesized via Ultrafast Automatic Flame Technique

Scientific Reports

Replacing platinum (Pt) metal-based electrocatalysts used in the oxygen reduction reaction (ORR) ... more Replacing platinum (Pt) metal-based electrocatalysts used in the oxygen reduction reaction (ORR) in fuel cells is an important research topic due to the high cost and scarcity of Pt, which have restricted the commercialization of these clean-energy technologies. The ABO 3-type perovskite family of an ACu 3 Ti 4 O 12 (A = Ca, Y, Bi, and La) polycrystalline material can serve as an alternative electrocatalyst for the ORR in terms of low-cost, activity, and stability. These perovskite materials may be considered the next generation electro-catalyst for the ORR because of their photocatalytic activity and physical and chemical properties capable of containing a wide range of A-and B-site metals. This paper reports the ORR activity of a new Y 2/3 Cu 3 Ti 4 O 12 perovskite, synthesized via a rapid and facile automatic flame synthesis technique using rotating disk electrode (RDE) measurements. Y 2/3 Cu 3 Ti 4 O 12 /C has superior ORR activity, stability, and durability compared to commercial Pt/C. The results presented in this article will provide the future perspectives to research based on ACu 3 Ti 4 O 12 (A = Ca, Y, Bi, Sm, Cd, and La) perovskite as the next generation electro-catalyst for the ORR in various electrochemical devices, such as fuel cells, metal-air batteries, and electrolysis. Fuel cells (FCs) are a new power source via the direct conversion of hydrogen to electricity as a potential replacement for Li-ion batteries systems in terms of safety, high efficiency, renewable sources, and environmental friendliness 1. The major obstacle to the commercialization of fuel cells is the high cost, poor stability, and slow kinetics of the oxygen reduction reaction (ORR) of platinum and platinum-based electrocatalysts in fuel-cell electrodes 2. Thus far, the best electrocatalysts for the ORR of the cathode are carbon-supported Pt and/or its composites 3-8. High cost and scarcity of platinum requires either use of noble metal with an increased efficiency or the utilization of non-precious electrocatalysts for commercialization on a large scale. In addition, Pt-based electrocatalysts suffer from methanol crossover and CO poisoning 9. The ORR is not only an essential electrochemical process in fuel cells, but is also required for other electrochemical technologies, such as metal-air batteries and water electrolysis 10. The ORR takes place through multiple electron transfer in alkaline media. Depending on the nature and electrocatalytic activity of the catalysts, the ORR in alkaline media can occur either via a two electron process to produce HO 2 − or a four electron process to produce OH − (O 2 + 2H 2 O + 4e − → 4OH −) 11. A high ORR overpotential has been the main obstacle to making these technologies viable. Therefore, major efforts have been made to discover cost-effective and efficient ORR catalysts in traditional aqueous media. A general model of the oxygen reduction kinetics in porous electrodes must include oxygen diffusion, oxygen adsorption, or surface reaction on the active sites of the catalyst, charge transfer, and the diffusion of products 12. ABO 3 type perovskite oxides, particularly ACu 3 Ti 4 O 12 (A = Ca, La, Bi, Sm, Cd, and Y), have great potential as low cost, high stability, and better kinetics electro-catalyst and may be considered the next generation electro-catalyst for the ORR because of

Research paper thumbnail of Pd@TTF Tailored Nanostructured Platform: Voltammetric Estimation of Ceftazidime

Research paper thumbnail of Hydrophobicity Effects in Iron Polypyridyl Complex Electrocatalysis within Nafion Thin-Film Electrodes

Phys. Chem. Chem. Phys., 2016

Four polypyridyl redox catalysts Fe(bp)32+, Fe(ph)32+, Fe(dm)32+, and Fe(tm)32+ (with bp, ph, dm,... more Four polypyridyl redox catalysts Fe(bp)32+, Fe(ph)32+, Fe(dm)32+, and Fe(tm)32+ (with bp, ph, dm, and tm representing 2,2′-bipyridine, 1,10-phenanthroline, 4,4′-dimethyl-2,2′-bipyridine, and 3,4,7,8-tetramethyl-1,10-phenanthroline, respectively) are investigated for the electrocatalytic oxidation of three analytes (nitrite, arsenite, and isoniazid).

Research paper thumbnail of Efficient Oxygen Reduction Electrocatalysts Based on Gold Nanocluster-Graphene Composites

ChemElectroChem, 2016

This paper describes the preparation and electrocatalytic activity of nanocomposites composed of ... more This paper describes the preparation and electrocatalytic activity of nanocomposites composed of reduced graphene oxide and Au25 clusters. Well-defined nanocomposites are prepared by coating the surface of reduced graphene oxide with multiple layers of Au25 film, the thickness of which can be precisely controlled according to the preparation conditions. The electrocatalytic activity of the nanocomposites are examined for the reduction of [Ru(NH3)6]3+ and in the oxygen reduction reaction by chronoamperometry and electrochemical impedance spectroscopy as a function of Au25 thickness. Whereas the catalytic rate constants obtained for the reduction of [Ru(NH3)6]3+ are found to be rather constant with varying Au25 thickness, those for the oxygen reduction reaction increased drastically with an increasing number of Au25 layers. This increase can be ascribed to the porous structures generated in the nanocomposites. The porous channels generated in the nanocomposites offer confined space surrounded by electrified surface, greatly enhancing the electrocatalytic activity for the oxygen reduction reaction. Additional rotating disk electrode and rotating ring-disk electrode voltammetry show that the nanocomposites support an efficient four-electron reduction of oxygen.

Research paper thumbnail of Electrochemical determination of nanomolar levels of isoniazid in pharmaceutical formulation using silver nanoparticles decorated copolymer

Electrochimica Acta, 2016

Research paper thumbnail of Selective determination of isoniazid using bentonite clay modified electrodes

Bioelectrochemistry (Amsterdam, Netherlands), 2015

Fe(dmbpy)3(2+) (where dmbpy is 4,4'-dimethyl-2,2'-bipyridine) was immobilized by ion-exch... more Fe(dmbpy)3(2+) (where dmbpy is 4,4'-dimethyl-2,2'-bipyridine) was immobilized by ion-exchange in a bentonite clay film coating on a glassy carbon electrode. Cyclic voltammetry characteristics of the immobilized Fe(dmbpy)3(2+) were stable and reproducible corresponding to the Fe(dmbpy)3(2+/3+) redox process. In the presence of isoniazid (IZ), the electrogenerated in film Fe(dmbpy)3(3+) oxidized IZ efficiently producing large anodic current. This current was linearly proportional to the IZ concentration in the solution. The process was described by an EC' electrocatalysis mechanism allowing for sensitive determination of IZ with a wide linear dynamic concentration range of 10.0μM to 10.0mM. The electrode was tested for its analytical suitability and possible discrimination of interferences by determining IZ in a commercially available pharmaceutical product. The paper reports on a simple, cheap, and easy to fabricate chronoamperometric chemical sensor for determination of ...

Research paper thumbnail of Tris(4,4′-dimethyl-2,2′-bipyridine)iron(II)-Exchanged Nafion for Arsenite Determination in Water Samples

ChemElectroChem, 2013

ABSTRACT A low cost and easy-to-construct electrochemical sensor is fabricated for the determinat... more ABSTRACT A low cost and easy-to-construct electrochemical sensor is fabricated for the determination of arsenite in water by using an Fe(dmbpy)32+-exchanged (dmbpy=4,4′-dimethyl-2,2′-bipyridine) Nafion (Nf) film. Arsenite at a glassy carbon electrode (GCE) coated with the Fe(dmbpy)32+-exchanged Nf film is shown to be electrocatalytically oxidized at lower overpotentials than at a bare GCE, and a tentative mechanism is proposed for the electrocatalytic oxidation. This new electrochemical sensing platform (ESP) exhibits a wide linear calibration range (from 10 μM to 100 mM) with a correlation coefficient above 0.99 for the precise determination of arsenite; the ESP exhibits a detection limit of 10.0 μM for arsenite determination. Utility of the developed sensor is further assured by determining the concentration of arsenite present in standard aqueous samples and in samples from different water sources. Among the several interferences studied, high concentrations of Zn2+ (50 times higher than arsenite) can affect arsenite determination. Kinetic parameters, such as the diffusion coefficient, catalytic rate constant, and so forth, are determined by using chronocoulometry and chronoamperometry techniques.