Cost-effective carbon supported Fe 2 O 3 nanoparticles as an efficient catalyst for non-aqueous lithium-oxygen batteries (original) (raw)
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Iron-nickel spinel oxide as an electrocatalyst for non-aqueous rechargeable lithium-oxygen batteries
A lithium-oxygen (LieO 2) battery requires effective catalyst to enable oxygen reduction and evolution. Herein, we report the synthesis of novel macroporous NiFe 2 O 4 nanoparticles by a facile and cost-effective urea assisted co-precipitation process. Characterization of the catalysts by X-ray diffraction and transmission electron microscopy confirms the formation of a single phase NiFe 2 O 4 structure. The use of macroporous NiFe 2 O 4 particles as oxygen electrode catalyst in rechargeable LieO 2 batteries, exhibits a superior catalytic activity with high reversible capacity of 5940 mA h g À1. Additionally, catalytic activity results in low charge over potential and comparable discharge capacity and cycling stability, indicating its potential as a promising catalyst for LieO 2 batteries. The simple and cost effective chemical co-precipitation method can be explored for synthesis of another oxides based catalyst materials.
Chemistry of Materials, 2017
Flexible power sources and efficient energy storage devices with high energy density are highly desired to power a future sustainable community. Theoretically, rechargeable metal-air batteries are promising candidates for the next-generation power sources. The rational design of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts with high catalytic activity is critical to the development of efficient and durable metal-air batteries. Herein, we propose a novel strategy to mass synthesize non-precious transition-metal-based nitrogen/oxygen co-doped carbon nanotubes grown on carbon-nanofiber films (MNO-CNT-CNFFs, M= Fe, Co, Ni) via a facile free-surface electrospinning technique followed by in-situ growth carbonization. Combining the high catalytic activity of Fe-catalyzed CNTs and the efficient mass transport characteristics of 3D carbon fiber films, the resultant flexible and robust FeNO-CNT-CNFFs exhibit the highest bifunctional oxygen catalytic activities in terms of a positive half-wave potential (0.87 V) for ORR and low overpotential (430 mV @ 10 mA cm-2) for OER. As a proof-of-concept, newly designed hybrid Li-air batteries fabricated with FeNO-CNT-CNFFs as air electrode present high voltage (~ 3.4 V), low overpotential (0.15 V) and long cycle life (over 120 hours) in practical open air tests, demonstrating the superiority of the freestanding catalysts and their promising potential for the applications in fuel cells and flexible energy storage devices.
Hollow Iron Oxide Nanoparticles for Application in Lithium Ion Batteries
Nano Letters, 2012
Material design in terms of their morphologies other than solid nanoparticles can lead to more advanced properties. At the example of iron oxide, we explored the electrochemical properties of hollow nanoparticles with an application as a cathode and anode. Such nanoparticles contain very high concentration of cation vacancies that can be efficiently utilized for reversible Li ion intercalation without structural change. Cycling in high voltage range results in high capacity (∼132 mAh/g at 2.5 V), 99.7% Coulombic efficiency, superior rate performance (133 mAh/g at 3000 mA/g) and excellent stability (no fading at fast rate during more than 500 cycles). Cation vacancies in hollow iron oxide nanoparticles are also found to be responsible for the enhanced capacity in the conversion reactions. We monitored in situ structural transformation of hollow iron oxide nanoparticles by synchrotron X-ray absorption and diffraction techniques that provided us clear understanding of the lithium intercalation processes during electrochemical cycling.
Journal of Alloys and Compounds, 2018
The Fe 2 V 4 O 13 is considered as one of the most promising cathode materials for next generation secondary batteries owing to its high specific capacity and energy density. However, the synthesis of pure Fe 2 V 4 O 13 is difficult because of complicated Fe 2 O 3-V 2 O 5 phase diagram. Thus, in this paper, a facile solution combustion method which operates relatively at low temperature was proposed to synthesize impurity free Fe 2 V 4 O 13 nanoparticles. The selection of fuel, oxidizer/fuel (O/F) ratio and temperature on the formation of impurity free Fe 2 V 4 O 13 has been investigated. The optimum temperature and time for the preparation of impurity free Fe 2 V 4 O 13 nanoparticles was found to be 350 C/1 hour. The synthesized Fe 2 V 4 O 13 nanoparticles exhibit monoclinic phase with high surface area of 36 m 2 /g. The prepared Fe 2 V 4 O 13 nanoparticles were tested as cathode material for lithium secondary battery and charge discharge results show that the 154 mAh•g-1 is retained after 50 cycle.
Nano Research, 2014
We report a novel chemical vapor deposition (CVD) based strategy to synthesize carbon-coated Fe 2 O 3 nanoparticles dispersed on graphene sheets (Fe 2 O 3 @C@G). Graphene sheets with high surface area and aspect ratio are chosen as space restrictor to prevent the sintering and aggregation of nanoparticles during high temperature treatments (800 °C ). In the resulting nanocomposite, each individual Fe 2 O 3 nanoparticle (5 to 20 nm in diameter) is uniformly coated with a continuous and thin (two to five layers) graphitic carbon shell. Further, the core-shell nanoparticles are evenly distributed on graphene sheets. When used as anode materials for lithium ion batteries, the conductive-additive-free Fe 2 O 3 @C@G electrode shows outstanding Li + storage properties with large reversible specific capacity (864 mAh/g after 100 cycles), excellent cyclic stability (120% retention after 100 cycles at 100 mA/g), high Coulombic efficiency (~99%), and good rate capability.
Advanced Materials, 2020
OER) or only remain active for one of the reactions (different ORR/OER rates). [1-5] This can result in high overpotentials-excess energy above its thermodynamic value (2.96 V)-required to form and decompose lithium peroxide (Li 2 O 2) at the cathode during discharge (ORR) and charge (OER) processes, respectively. Numerous metal catalysts such as platinum (Pt), gold (Au), and ruthenium (Ru), as well as non-metallic catalysts such as transition-metal oxides, transition-metal dichalcogenides, and carbon-based catalysts, have been employed to resolve this issue, however, no major breakthrough has been reported to date. [4,6-11] Therefore, designing a highly active catalyst that can minimize the energy barriers-excess input energy-to form and decompose Li 2 O 2 nanoparticles at the cathode is a key challenge for the development of this technology. Electrocatalytic properties of transition metal phosphides have received great attention and been subject of theoretical and experimental studies. [12-16] Wang et al. demonstrated a convenient and straightforward approach to the synthesis of a 3D selfsupported Ni 5 P 4-Ni 2 P nanosheet cathode, very stable in acidic medium with an outstanding hydrogen evolution reaction (HER) activity. [17] Some other studies include development of The main drawbacks of today's state-of-the-art lithium-air (Li-air) batteries are their low energy efficiency and limited cycle life due to the lack of earth-abundant cathode catalysts that can drive both oxygen reduction and evolution reactions (ORR and OER) at high rates at thermodynamic potentials. Here, inexpensive trimolybdenum phosphide (Mo 3 P) nanoparticles with an exceptional activity-ORR and OER current densities of 7.21 and 6.85 mA cm −2 at 2.0 and 4.2 V versus Li/Li + , respectively-in an oxygen-saturated non-aqueous electrolyte are reported. The Tafel plots indicate remarkably low charge transfer resistance-Tafel slopes of 35 and 38 mV dec −1 for ORR and OER, respectively-resulting in the lowest ORR overpotential of 4.0 mV and OER overpotential of 5.1 mV reported to date. Using this catalyst, a Li-air battery cell with low discharge and charge overpotentials of 80 and 270 mV, respectively, and high energy efficiency of 90.2% in the first cycle is demonstrated. A long cycle life of 1200 is also achieved for this cell. Density functional theory calculations of ORR and OER on Mo 3 P (110) reveal that an oxide overlayer formed on the surface gives rise to the observed high ORR and OER electrocatalytic activity and small discharge/charge overpotentials. The advancement of lithium-air (Li-air) batteries, proposed as a potential alternative for existing energy storage systems, is mainly hampered by low energy efficiency and limited cycle life. One of the major drawbacks for today's Li-air batteries is that developed catalysts exhibit sluggish activity for both oxygen reduction and evolution reactions (ORR and
Solid-phase catalysts prepared by pyrolysis of Iron(II) phthalocyanine (FePC) embedded in high-surface carbons were evaluated for the catalysis of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Li +-conducting non-aqueous electrolytes. The ORR mechanism in high donor number (DN) dimethyl sulfoxide (DMSO)-based electrolytes is markedly different from that occurs in low DN acetonitrile(MeCN)-based electrolytes. The ORR is catalyzed by the reduced Fe(I) state of Fe(II)PC. Consequently, the Fe(II)PC/Fe(I)PC redox potential relative to O 2 reduction potential in each electrolyte is important for ORR catalysis. In MeCN-based electrolytes, the Fe(I)PC catalyst is formed at a higher potential than the ORR potential. Hence the catalyzed ORR occurs at the inner-Helmholtz plane of the electrode, stabilizing the superoxide ion (O 2 −) formed by one-electron reduction of O 2 , as Fe(I)PC–O 2 −. Indeed, LiO 2 was identified in the Raman spectra of cathodes from discharged Li-O 2 battery cells. In DMSO-based electrolytes, the Fe(I)PC formation potential occurs below the ORR potential and accordingly LiO 2 is more stable in its solvated state in the electrolyte solution as the Li(DMSO) n –O 2 − ion pair. This drives the ORR at the outer-Helmholtz plane of both catalyzed and uncatalyzed electrodes in DMSO-based electrolytes. The FePC embedded carbon electrode doubled the cycle life of Li-O 2 cells utilizing low DN electrolytes. The limited rechargeability of the Li anode, kinetic limitations of the oxygen electrode reactions and the constraints associated with the development of suitable battery architecture are deterrents to the development of a practical rechargeable Li-O 2 battery. 1 The major discharge product identified in a non-aqueous Li-O 2 battery is Li 2 O 2 involving an overall two-electron O 2 reduction which yields a theoretical specific energy of 3505 Wh/kg. This is thirty three percent lower than the theoretical specific energy of 5200 Wh/kg calculated on the basis of the four-electron reduction of O 2 to form Li 2 O as the discharge product. Therefore, a cathode catalyst that could catalyze the reduction of O 2 to form Li 2 O as the discharge product is appealing. 2–4 Simultaneously, if the same catalyst can promote oxygen evolution reactions at lower over-potentials, then the high capacity of the Li-O 2 battery could be accessed more efficiently in many charge/discharge cycles to realize the goal of an ultra-high energy density rechargeable Li-O 2 battery. Oxygen electrocatalysts based on transition metal-N 4 centers such as metal porphyrins and phthalocyanines have demonstrated varying degrees of activity to catalyze ORR in batteries and fuel cells. 2,3,5,6 The phthalocyanine macrocycle in particular is a strong electron ac-ceptor which facilitates the axial coordination of the metal center in metal phthalocyanines (MPC) with ligands having a range of electron donor characteristics. 7 Only a few studies have reported ORR/OER catalysis of the O 2 electrode by these metal-N 4 centers in non-aqueous electrolyte-based Li-O 2 batteries. 6,8–10 In this paper we provide evidence for the tunability of the redox potential of the iron(II) phthalo-cyanine by changing the electron donor property of the ligating solvent molecule. Our results demonstrate the tunability of the ORR catalysis on the metal-N 4 center with respect to the electron donor property of the organic electrolyte (via the solvates, Li + (solvent) n , formed between the organic solvent and Li +). We also show that iron(II) phthalocyanine can be transformed into insoluble solid catalysts by appropriate high temperature processing making them potentially useful for practical Li-air batteries. Recent study by Trahan et al. have shown that CoPC-based catalysts influence O 2 electrochemistry in Li-O 2 batteries. 2 According to these authors O 2 reduction reaction mechanism at the catalyst is determined by the solvent's ability to * Electrochemical Society Fellow. z E-mail: kmabraham@comcast.net modulate the Lewis acidity of Li + in the Li +-conducting electrolyte solution. In high DN solvents the ORR on the electrode proceeds at the outer-Helmholtz plane since the Li(solvent) n + –O 2 − intermediate is stabilized in the electrolyte solution. On the other hand, in low DN solvents such as acetonitrile and TEGDME the ORR proceeds at the electrode's inner-Helmholtz plane on the catalyst center since the electron acceptor property of the catalyst is higher than that of the solvated Li + , Li(solvent) n +. An ideal catalyst would be one that selectively catalyzes the ORR and OER reactions without interfering with the performance of the electrolyte or the lithium anode. We demonstrate that the solid phase FePC catalyst that we have developed approach this performance. Our results contrast the data reported by Sun et al. 11 who employed FePC, dissolved in TEGDME and DMSO-based electrolytes, as a re-dox shuttle for electrons and superoxide ions (O 2 − , the one-electron reduction product of O 2), between carbon cathode and the insulating Li 2 O 2 formed on it during discharge. They concluded that the O 2 adsorbed to the FePC present in the electrolyte solution as FePC–O 2 would undergo reduction to form FePC–LiOOLi which would then diffuse to a nucleated Li 2 O 2 site and precipitate there. Similarly, they claim that the Fe(III)PC in solution can oxidize the Li 2 O 2 to form FePC–O 2 − which would then diffuse to the carbon surface where the superoxide would be oxidized to O 2. However, there was little unambiguous electrochemical or spectroscopic evidence presented to support their solution catalyzed ORR and OER mechanisms. It is important to note that FePC dissolved in the electrolyte solution is an impractical catalyst since it reacts with the Li metal anode and delete-riously affects the rechargeability of the Li-air battery. Consequently, an FePC catalyst that does not dissolve in non-aqueous electrolytes while retaining its ORR and OER catalytic activity would be of great interest for use in Li-air batteries. We have developed such insoluble solid phase catalysts by heat-treating intimate mixtures of high surface area carbon and FePC at selected high temperatures. The properties of these catalysts we have prepared are reported together with their ORR and OER activities in non-aqueous electrolytes and Li-air battery cells. We present a comprehensive discussion of the structure-catalytic property relationships of these novel solid phase FePC embedded in carbon cathodes and the manner in which the non-aqueous electrolytes influence their electrochemical activity. The FePC embedded carbon cathodes have doubled the cycle life of Li-air battery cells.