Electrodes For Oxygen Evolution Reaction Research Articles

Simple Chemical Solution Deposition of Co₃O₄ Thin Film Electrocatalyst for Oxygen Evolution Reaction.

Oxygen evolution reaction (OER) is the key reaction in electrochemical processes, such as water splitting, metal-air batteries, and solar fuel production. Herein, we developed a facile chemical solution deposition method to prepare a highly active Co3O4 thin film electrode for OER, showing a low overpotential of 377 mV at 10 mA/cm(2) with good stability. An optimal loading of ethyl cellulose additive in a precursor solution was found to be essential for the morphology control and thus its electrocatalytic activity. Our results also show that the distribution of Co3O4 nanoparticle catalysts on the substrate is crucial in enhancing the inherent OER catalytic performance.

Oxygen Evolution Catalyzed by Nickel-Iron Oxide Nanocrystals with a Nonequilibrium Phase.

Mixed nickel-iron oxides are of great interest as electrocatalysts for the oxygen evolution reaction (OER), the kinetically challenging half-reaction required for the generation of hydrogen gas from water via electrolysis. Previously, we had reported the synthesis of single crystal, soluble nickel-iron oxide nanoparticles over a wide range of nickel:iron compositions, with a metastable cubic rock salt phase ([Ni,Fe]O) that can be isolated despite the low solubility of iron in cubic nickel oxide at ambient temperatures. Here, activity for OER was examined, catalyzed by these [Ni,Fe]O nanoparticles integrated with indium tin oxide (ITO) electrodes. Because the as-prepared [Ni,Fe]O nanoparticles are oleate-capped, the surface ligands needed to be removed to induce adherence to the ITO substrate, and to enable charge transfer and contact with water to enable OER catalysis. Two different approaches were taken to reduce or eliminate the coverage of oleate ligands in these films: UV irradiation (254 nm) and air plasma. UV irradiation proved to lead to better results in terms of stable and OER-active films at pH 13. Kinetic analysis revealed that the Tafel slopes of these nanoparticle [Ni,Fe]O OER electrodes were limited by the electrochemical surface area and were found to be within the range of 30 to 50 mV/decade. Across the four compositions of Ni:Fe studied, from 24:76 to 88:12, the observed overpotential at 10 mA/cm2 for the OER in basic conditions decreased from 0.47 to 0.30 V as the proportion of nickel increased from 24% to 88%.

Ionic liquid-assisted synthesis of N/S-double doped graphene microwires for oxygen evolution and Zn–air batteries

Catalysts with both dense active sites and large effective surface area are crucial to the realization of high activity and fast kinetics in catalytic applications, but are very challenging to produce. In this work, we report a facile protocol to synthesize such a material of nitrogen (N), sulfur (S)-double doped graphene microwires. The critical step in this protocol is the preparation of catalyst precursor, which was obtained by the infiltration of graphene framework with the ion liquid, N-methyl pyrrolidone hydrosulfate. The subsequent carbonization of catalyst precursor can result in the material with not only heavy heteroatom-doping content (N: 10.8%; S: 2.4%), but also densely packed microstructure (packing density: 1.4gcm−3) and rich porosity (surface area: 351m2g−1). Because of these remarkable structural properties, the material can work as an efficient catalyst electrode for oxygen evolution reaction (OER), showing a low overpotential of 0.31V at the current density of 10mAcm−2, high Faradaic efficiency of ~95%, and stable operation for 25h. Moreover, the electrode can also serve as a cathode for catalyzing the charging and discharging processes of a Zn–air battery. This new class of electrode, having a free-standing one-dimensional (1D) architecture, can work without extra supports, which is easily incorporated into various renewable energy devices.

Influence of Temperature on the Shape Evolution of IrO2-SiO2 coating and Its Electrochemical Activity for Oxygen Evolution

The surface structure of IrO2-SiO2/Ti anode was modified by thermal decomposition of non-aqueous solution of iridium chloride (IrCl3) and tetraethoxysilane (TEOS) with different calcination temperatures. The surface morphology and microstructure of these anodes were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray-photoelectron spectroscopy (XPS). At low calcination temperature, the surface was dominated by biphase solid solution, in which the IrO2-rich phase, spiculate IrO2-SiO2 crystal, was encircled by the SiO2-rich phase, the amorphous SiO2­-IrO2 solution. As the calcination temperature increase, more amorphous IrO2 from the SiO2-rich phase converted into rutile nanothorn, then into nanoparticle composed by fine crystallites nanosheet aggregated on the surface of coatings and grew larger constantly. The electrochemical behaviors of the oxygen evolution reaction (OER) were evaluated by cyclic voltammetry (CV) and quasi steady-state polarization. The results showed that the electrocatalytic activities and the electrochemically active sites on the surface of the oxide electrodes for OER decreased with the increase of calcination temperature. This could be explained by the decrease of amorphous IrO2 and the surface active sites, such as surface OH groups and crystal edges. The onset potentials of IrO2-SiO2/Ti anode were significantly affected by the calcinations temperature. The onset potential of amorphous film was shifted toward the negative side from that of the crystalline ones. The Tafel slopes indicated that the electron charge transfer process is the rate determining step of IrO2-SiO2/Ti electrodes for the OER.

Internal Resistance Reduction of a Membrane Electrolyzer for Electrohydrogenation of Toluene As Hydrogen Carrier Synthesis

Introduction Potential of renewable energy is uneven distribution with fluctuation; therefore, to increase renewable energies, energy carrier technology is needed for storage and transportation. Hydrogen can be produced with various energies, but its volumetric energy density is too low to storage and transport. Toluene-methylcyclohexane organic chemical hydride system is one of promising technologies as hydrogen storage and transportation by invention of the dehydrogenation catalyst (1). Electrohydrogenation of toluene with water splitting has higher theoretical energy conversion efficiency compare to a series process of water electrolysis and hydrogenation. Direct and indirect electrohydrogenation processes had been proposed (2, 3). However, further challenge is needed to improve efficiency, durability, and increasing of the scale. We focused on a membrane electrolysis as a direct process with water splitting. Cathode side is a cathode membrane assembly, which is applied PEFC technology with precious metal loaded carbon electrocatalyst. Anode is a dimensionally stable electrode for oxygen evolution reaction in acidic electrolyte using industrial electrolysis technology. In our previous study, cell voltage of electrohydrogenation of toluene was almost as same as water electrolysis, but internal resistance of the electrolyzer was not small enough and conversion was very low (4). In this study, the membrane of anode side was hydrophilized to release oxygen from anode to reduce internal resistance, and characteristics of low concentration of toluene has been evaluated to reach high conversion to methylcyclohexane. Experimental A cathode was a carbon paper (35BC, SGL) coated 0.5 mgcm-2 of PtRu (TEC61E54, TKK) with Nafion dispersion. The cathode was pressed on a perfluoroethylene sulfuric acid (PFSA) membrane (Nafion® 212CS, DuPont) for a cathode membrane assembly. The membrane of the cathode side was hydrophilized by ZrO2 power coating or mechanically roughing. A non-treated membrane was also used for comparison. A DSE® anode with IrO2 based electrocatalyst is used for oxygen evolution. Toluene/methylcyclohexane mixture and 1M (=moldm-3) of H2SO4 were supplied to the cathode and anode for hydrogenation of toluene, respectively. The toluene concentration was in the range from 1 to 100 %. Cell voltage was determined with 4 mVs-1 of voltage sweep from 0.6 for toluene hydrogenation. Current efficiency was determined with constant cell voltage electrolysis with the volume measurement of gas evolution from cathode during the electrolysis. Internal resistance (iR) was determined with higher frequency intercept of AC impedance method in the cell voltage range from 1.0 to 2.5 V. Results and discussion Figure 1 shows the internal resistance and cell voltage as a function of current density for 100 % TL fed with various membrane treatments of anode side. The output of H2SO4 pulsed especially in high current density region, and current fluctuated above 2.2 V of the cell voltage with hydrogen evolution from cathode. This behavior would be affected by oxygen release between the membrane and the anode. The cell voltage and resistance of the hydrophilized membranes was smaller than those of non-treated membrane. At this moment, the output of H2SO4 and oxygen mixture was smooth, and there was no gas evolution reaction from cathode. Figure 2 shows the cell voltage (a) and current efficiency of hydrogenation as a function of current density for 1 to 100 % of TL-MCH fed with the rough surface membrane cell. The side reaction is only hydrogen evolution for this system. Error bars were current variation during constant cell voltage electrolysis for current and current efficiency measurements. The lines show the polarization curves with 4 mVs-1 of cell voltage sweep. For 100 and 50 % of TL fed, the current efficiency of electrohydrogenation was above 97 % up to the limit of current source of 0.44 Acm-2. At this moment, electrolysis was stable, and the cell voltage was around 2.0 V at 0.4 Acm-2. Below 10 % of TL fed, simultaneously hydrogen evolution proceeded at higher current density region with current variation. Therefore, this process should be feasible, and improvement of mass transfer in the cathode catalyst layer is important issue for real application. Acknowledgment This work was supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), “energy carrier” (Funding agency: JST). We applicate the person concerned them. References 1) Y. Okada, E. Sasaki, E. Watanabe, S. Hyodo, H. Nishijima, J. Hydrogen Energy, 2006, 31, 1348. 2) T. Hirashige, T. Ishikawa, M. Sugimasa, WO 2011/122155 Al (PCT/JP2011/053478) 2011. 3) C. Iwakura, Y. Yoshida, S. Ogata, H. Inoue, J. Mater. Res., 2011, 13, 821. 4) S. Mitsushima, Y. Takakuwa, Y. Kohno, K. Matsuzawa, A. Kato, Y. Nishiki, of 226th meeting of the ECS, #619 (2014). Figure 1

High Energy Density Aqueous Metal Hydride-Air Batteries

Li-ion batteries exhibit poor abuse tolerance which necessitate complex charge management electronics, elaborate thermal management and adequate mechanical reinforcements, which result in reduced system-level energy densities and higher battery costs. These constraints make the aqueous systems more appealing, especially if their energy densities can be further improved. In this context, we are developing low cost and safe (aqueous) rechargeable metal-hydride / air batteries with high energy densities (200 Wh/kg and 400 Wh/l at cell level) and long cycle life for electric vehicle applications under an ARPA-E sponsored program. Our effort is focused on developing: i) new metal hydride alloys with higher hydrogen absorption capacities, ii) stable electro-catalysts for bifunctional oxygen electrode or suitable dual-electrodes for oxygen reduction/oxidation, iii) Stable hydroxyl membranes for improved cell durability and easier water management, and iv) New cathode designs with dispersed catalysts over nanostructured frameworks. For the metal hydride anodes, the desired performance parameters include: i) High hydrogen absorption of > 1.5 w% in the gas phase with low absorption pressures (below 2 bar) and desorption temperatures (ambient), ii) High electrochemical capacity of 400 mAh/g, iii) Low corrosion rate and long cycle life (> 1000 cycles) and iv) fast electrode kinetics to operate at > C/3 rate. We initially focused on AB5 alloys, supplied by BASF (e.g., La10.5Ce4.3Pr0.5Nd1.4Ni64.3Co5.0Al6.0Mn4.6Cu3.4)1 to establish the baseline for MH-air cells. In parallel, we have started developing metal hydride alloys of V-based BCC Alloys, specifically quaternary alloys of Ti-V-Ni-Cr, which reportedly have a maximum discharge capacity of 450 mAh/g with 90% capacity retention over 30 cycles.2 For the metal hydride air cells, we have been focusing on both the options of bifunctional air cathode as well as dual-electrode configuration, i.e., with an auxiliary electrode to support the oxygen evolution reaction (OER). Our initial studies for the bifunctional air cathode are based on thin-film noble metal catalysts, dispersed on nanostructures. For the dual electrode configuration, we are examining low-cost commercial electrodes based on manganese oxide catalysts for oxygen reduction, and Ni-based electrodes for OER. In either case, we have been able to demonstrate good cycling characteristics in laboratory MH-air test cells. In addition, we performed fundamental studies on the MH anodes as well as air cathodes, using the Differential Electrochemical Mass Spectroscopy (DEMS) technique (developed at Liox with swage-lock test cells coupled with mass spectrometer), to understand the gaseous environments within a MH-air cell. Young et al., J. of Alloys and Compounds 509 (2011) 4896.Inoue et al., Electrochimica Acta (2012), 59, 23-31

Metal-organic framework derived hybrid Co3O4-carbon porous nanowire arrays as reversible oxygen evolution electrodes.

Hybrid porous nanowire arrays composed of strongly interacting Co3O4 and carbon were prepared by a facile carbonization of the metal-organic framework grown on Cu foil. The resulting material, possessing a high surface area of 251 m(2) g(-1) and a large carbon content of 52.1 wt %, can be directly used as the working electrode for oxygen evolution reaction without employing extra substrates or binders. This novel oxygen evolution electrode can smoothly operate in alkaline solutions (e.g., 0.1 and 1.0 M KOH), affording a low onset potential of 1.47 V (vs reversible hydrogen electrode) and a stable current density of 10.0 mA cm(-2) at 1.52 V in 0.1 M KOH solution for at least 30 h, associated with a high Faradaic efficiency of 99.3%. The achieved ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the state-of-the-art noble-metal/transition-metal and nonmetal catalysts, originate from the unique nanowire array electrode configuration and in situ carbon incorporation, which lead to the large active surface area, enhanced mass/charge transport capability, easy release of oxygen gas bubbles, and strong structural stability. Furthermore, the hybrid Co3O4-carbon porous nanowire arrays can also efficiently catalyze oxygen reduction reaction, featuring a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal-air batteries, regenerative fuel cells, and other important clean energy devices.

Invited: Novel Cell Design and Inexpensive Electrocatalysts for Hybrid Lithium-Air Batteries

Growing environmental concerns and increasing demand for energy have stimulated extensive interest in electrical energy storage, particularly in the form of batteries. Li-air batteries are appealing in this regard as they offer much higher energy density than the current Li-ion batteries. However, the nonaqueous Li-air batteries are hampered by electrolyte degradation and clogging of the air electrodes by the insoluble discharge products. Interestingly, hybrid Li-air batteries in which a solid electrolyte separates the lithium metal anode in an aprotic electrolyte from the air electrode in an aqueous catholyte could overcome these problems. However, there are many challeges that need to be overcome, e.g.,poor stability of the solid electrolyte in strongly acidic or alkaline catholytes, high internal resistance, and lack of less expensive, efficient, durable oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts. Much effort has been focused on developing efficient bifunctionl catalysts to lower the overpotential and improve the stability of hybrid Li-air batteries in recent years, but the cycle life is still limited. This presentation will focus on advanced cell configurations and high-performance catalysts for hybrid lithium-air batteries.We have developed an advanced hybrid Li-air cell with decoupled, mesoporous nanocatalysts, which could be cycled for over 100 cycles (400 hours) in air with only 0.08 V increase in round-trip overpotential based on discharge and charge end voltages. With this cell configuration, mesoporous NiCo2O4 nanoflakes directly grown onto a nickel foam (NCONF@Ni) serve as the OER electrode. The catalytic active surface area increased from < 1 m2 g-1 for nickel foam to more than 80 m2 g-1. The spinel NiCo2O4 catalyst exhibits much higher catalytic activity and stability than Ni metal at high potentials, leading to a fairly low OER overpotential that is comparable to that seen with the noble-metal IrO2 catalyst. A nitrogen-doped mesoporous carbon (NMC) with extremely high surface area (1520 m2 g-1) and optimized nitrogen doping content (3.9 wt. %) was loaded onto a hydrophobic carbon fiber paper to act as the ORR electrode. The highly mesoporous NMC exhibits activity similar to the noble-metal Pt/C catalyst, but with much better stability. With this configuration, a variety of other non-noble-metal or metal-free catalysts could play the role of ORR without worrying about their stability in the high-voltage charge process. For example, we have developed a 3-D O- and N-doped carbon nanoweb as a highly active metal-free catalyst for ORR in hybrid Li-air cells. The 3-D nanoweb structure provides an ideal backbone support for catalytically active sites due to the fast electron and mass transport properties compared with the 1-D or 2-D structure. In addition, the synergistic effect between the O and N groups creates highly active pyridone groups all over the nanoweb surface, which significantly improves the catalytic activity toward ORR. Furthermore, a phosphate buffer catholyte with a moderate pH has been developed to protect the solid electrolyte in hybrid Li-air batteries. It contains phosphoric acid and supporting salts, which reduce the internal resistance and overpotential. A high energy density could be achieved by utilizing all three protons in phosphoric acid. Further increase in power density and efficiency has also been realized by increasing the solid-electrolyte conductivity and the operating temperature to 40 oC.

Invited Presentation: Highly Reversible Hybrid Lithium-Air Batteries

Lithium-air batteries have become attractive due to their extremely high theoretical energy density. However, conventional lithium-air cells operating with nonaqueous electrolytes suffer from poor cycle life due to the clogging of the porous air cathodes by insoluble discharge products, contamination of the organic electrolyte by moist air, and decomposition of the electrolyte during cycling. Attempts to overcome these problems by developing compatible electrolyte/catalyst combinations have invariably been disappointing. These difficulties could be overcome by adopting a new cell configuration consisting of a lithium metal anode in the conventional organic electrolyte separated by a lithium-ion conducting solid electrolyte from the air electrode in an aqueous catholyte. Accordingly, this presentation will focus on the development of catholytes that can avoid corrosion of the solid electrolyte as well as efficient, inexpensive electroctalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).A buffer catholyte solution with a moderate pH, consisting of phosphoric acid and a supporting salt, has been developed to keep the solid electrolyte stable and reduce the internal resistance and overpotential. With a high operating voltage and the utilization of all three protons of phosphoric acid, the buffer catholyte enables a rechargeable lithium-air cell with high energy density. Further increase in power density has been realized by increasing the solid-electrolyte conductivity and the operating temperature to 40 oC.The biggest challenge with lithium-air cells is the large overpotentials associated with the ORR and OER. Nanocrystalline iridium oxide has been the best OER catalyst, but it is expensive. In this regard, the low-temperature form of lithium cobalt oxide (designated as LT-lithium cobalt oxide) that adopts a lithiated spinel structure has been developed as an inexpensive, efficient electrocatalyst for OER. Its OER activity is much higher than that of the high-temperature form of lithium cobalt oxide (designated as HT-lithium cobalt oxide), which has a layered structure and is used as a cathode in lithium-ion batteries, and even slightly higher than that of iridium oxide. Although the ORR activity of LT-lithium cobalt oxide is low, a combination of high ORR and OER activity could be realized by chemically extracting lithium from the LT-lithium cobalt oxide, demonstrating the lithium-deficient, spinel-type LT-lithium cobalt oxide as a bifunctional catalyst for rechargeable metal-air batteries. The high OER and ORR activities of spinel-type LT-lithium cobalt oxides are attributed to cubane-like subunits and a pinning of the cobalt-3d energy with the top of the oxygen-2p band. Furthermore, a novel 3-D O- and N-doped carbon nanoweb (ON-CNW) has been developed as an inexpensive, metal-free catalyst for ORR. The 3-D nanoweb structure provides an ideal backbone support for catalytically active sites due to the fast electron and mass transport properties compared to 1-D or 2-D structures. Also, the synergistic effect between the O and N groups creates highly active pyridone groups all over the nanoweb surface that significantly improves the ORR activity. With a hybrid lithium-air cell, the ON-CNW exhibits performance close to that of commercial Pt/C. In addition, a novel hybrid lithium-air cell configuration with decoupled ORR and OER electrodes has been developed. With the conventional bifunctional air cathode that supports ORR during discharge and OER during charge, the ORR catalyst and carbon support suffer from degradation under the highly oxidizing conditions during the charge process, resulting in rapid increase in overpotential upon cycling and limiting the cycle life. In contrast, the hybrid lithium-air cell with decoupled ORR and OER electrodes eliminates the degradation problems and leads to high efficiency with good cycle life.

A High‐Performance Binary Ni–Co Hydroxide‐based Water Oxidation Electrode with Three‐Dimensional Coaxial Nanotube Array Structure

Developing nanostructured Ni and Co oxides with a small overpotential and fast kinetics of the oxygen evolution reaction (OER) have drawn considerable attention recently because their theoretically high efficiency, high abundance, low cost, and environmental benignity in comparison with precious metal oxides, such as RuO2 and IrO2. However, how to increase the specific activity area and improve their poor intrinsic conductivity is still challenging, which significantly limits the overall OER rate and largely prevent their utilization. Thus, developing effective OER electrocatalysts with abundant active sites and high electrical conductivity still remains urgent. In this work, a scrupulous design of OER electrode with a unique sandwich‐like coaxial structure of the three‐dimensional Ni@[Ni(2+/3+)Co2(OH)6–7]x nanotube arrays (3D NNCNTAs) is reported. A Ni nanotube array with open end is homogeneous coated with Ni and Co co‐hydroxide nanosheets ([Ni(2+/3+)Co2(OH)6–7]x) and is employed as multifunctional interlayer to provide a large surface area and fast electron transport and support the outermost [Ni(2+/3+)Co2(OH)6–7]x layer. The remarkable features of high surface area, enhanced electron transport, and synergistic effects have greatly assured excellent OER activity with a small overpotential of 0.46 V at the current density of 10 mA cm−2 and high stability.

Nitrogen-Doped Graphene Supported CoSe2Nanobelt Composite Catalyst for Efficient Water Oxidation

The slow kinetics of the oxygen evolution reaction (OER) greatly hinders the large-scale production of hydrogen fuel from water splitting. Although many OER electrocatalysts have been developed to negotiate this difficult reaction, substantial progresses in the design of cheap, robust, and efficient catalysts are still required and have been considered a huge challenge. Here, we report a composite material consisting of CoSe2 nanobelts anchored on nitrogen-doped reduced graphene oxides (denoted as NG-CoSe2) as a highly efficient OER electrocatalyst. In 0.1 M KOH, the new NG-CoSe2 catalyst afforded a current density of 10 mA cm(-2) at a small overpotential of mere 0.366 V and a small Tafel slope of ∼40 mV/decade, comparing favorably with the state-of-the-art RuO2 catalyst. This NG-CoSe2 catalyst also presents better stability than that of RuO2 under harsh OER cycling conditions. Such good OER performance is comparable to the best literature results and the synergistic effect was found to boost the OER performance. These results raise the possibility for the development of effective and robust OER electrodes by using cheap and easily prepared NG-CoSe2 to replace the expensive commercial catalysts such as RuO2 and IrO2.

Effect of Morphology of Co3O4 for Oxygen Evolution Reaction in Alkaline Water Electrolysis.

In this paper, three different morphological Co3O4 electrodes for oxygen evolution reaction (OER) have been synthesized. By comparing the three morphologies of Co3O4, the electrocatalytic properties show that the urchin-like spheres of Co3O4 electrode has relative low overpotential and good electrocatalysis stability, indicating that the structure of urchin-like Co3O4 spheres exhibit an easy OER for water splitting.

Novel phosphorus-doped PbO2–MnO2 bicontinuous electrodes for oxygen evolution reaction

Download options Please wait... Supplementary files Supplementary information PDF (1803K) Article information DOI https://doi.org/10.1039/C4RA01831A Article type Paper Submitted 02 Mar 2014 Accepted 30 Apr 2014 First published 01 May 2014 Download Citation RSC Adv., 2014,4, 24020-24028 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Novel phosphorus-doped PbO2–MnO2 bicontinuous electrodes for oxygen evolution reaction Y. Li, L. Jiang, F. Liu, J. Li and Y. Liu, RSC Adv., 2014, 4, 24020 DOI: 10.1039/C4RA01831A To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Yuan Li Liangxing Jiang Fangyang Liu Jie Li Yexiang Liu

Electrochemical behaviour of nickel-based electrodes for oxygen evolution reaction in alkaline water electrolysis

NiZnS electrode has been investigated for use in oxygen evolution reaction in alkaline media. Nickel mesh electrode was coated with the ternary composition of NiZnS by four methods, viz., direct current electrodeposition, pulse electrodeposition, sonoassisted direct current electrodeposition and sonoassisted pulse electrodeposition. The oxygen evolution studies carried out using these electrodes resulted in higher current density for the electrode prepared by sonoassisted pulse electrodeposition compared to those prepared by other methods. Effect of plating current density, pulse duty cycle and temperature on the electrochemical parameters of the alloy coating has been studied. Surface morphologies of the various coating were studied using scanning electron microscopy. Long-term stability of the electrodes prepared was studied in alkaline medium. Exchange current density (jo) was found to increase with the increase in temperature and was the highest for sonoassisted pulse electrodeposited electrode.

Novel phosphorus-doped lead oxide electrode for oxygen evolution reaction

A facile and cost-effective electrochemical approach was proposed for the first time to prepare a phosphorus-doped lead dioxide (P-PbO2) electrode on a lead substrate. This was achieved by introducing a pyrophosphate solution containing Cu2+, F− and peptone as essential additives. Such a novel P-PbO2 electrode exhibits a significantly improved electrocatalytic activity for the oxygen evolution reaction as compared to a traditional Pb/PbO2 electrode.

A silica co-electrodeposition route to nanoporous Co3O4 film electrode for oxygen evolution reaction

Nanoporous Co3O4 (po-Co3O4) films have been prepared on stainless steel substrate by a novel two-step method. Firstly, a composite Co3O4-SiO2 film was fabricated via electrochemical co-deposition under a cathodic potential from the mixed sol-gel precursor. Then, the obtained composite film was underwent consecutive cycling voltammetries in a concentrated KOH solution to etch the SiO2 component, leading to the formation of po-Co3O4 films. The resultant film electrode exhibits satisfactory electrocatalytic property towards the oxygen evolution reaction (OER).

Oxygen evolution in alkali with gas diffusion electrodes

Progresses in the area of the oxygen evolution reaction (OER) are now occurring at a much faster rate relative to few years ago. For this reason, it has been deemed appropriate to present a critical review of the major and most recent contributions towards a fundamental understanding of what determines the OER electrocatalytic properties of a material. Furthermore, the technologies used to produce practical OER electrodes with top activities are assessed and the current benchmarks of performance are identified. Furthermore, results pertaining to our work on Raney–Ni gas diffusion anodes, which have been optimized in thickness and composition, are presented. An addition of 10 wt.% of a Co3O4 micrometric powder as co-catalyst (with Raney Ni–Fe) was found to enhance the polarization behavior and performance. The electrode so obtained achieves activities comparable with those of the best electrodes reported in the literature.Great emphasis has been placed in the analysis of the stability of the prepared Gas Diffusion Electrodes. Most of the GDEs were found to be stable in weeks long experiments with intermittent operation. The issue of integrating several functional layers (gas diffusion layer, active layer with current collector, separator layer) within a single, mechanically strong electrode assembly is briefly addressed.

A novel composite electrode for oxygen evolution reaction

FeOOH nanowires were prepared and characterized with X-ray diffraction spectroscopy and scanning electron microscopy. A composite electrode consisting of FeOOH and Ni foam (FeOOH/Ni-foam) was fabricated, and its catalytic performance for oxygen evolution reaction (OER) was evaluated and compared with nanowire NiCo2O4/Ni-foam electrode. The mass current density of OER on FeOOH/Ni-foam is around three times of that on NiCo2O4/Ni-foam. Ni foam played a key role for the high activity of the FeOOH/Ni-foam. A synergistic mechanism of FeOOH and Ni was proposed to account for the superior catalytic performance of the FeOOH/Ni-foam electrode. Considering the low cost, abundant resource and environment-benign property of FeOOH, the FeOOH/Ni-foam electrode would be a promising anode for OER.

A Bifunctional Air Electrode Catalyzed by Ba0.5Sr0.5Co0.8Fe0.2O3–δ for Zinc-Air Batteries

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Preparation and characterization of Ir Pt1−O2 anode electrocatalysts for the oxygen evolution reaction

Towards competent production of clean and electrolytic hydrogen, proton exchange membrane (PEM) water electrolysis offers several advantages, such as high purity of the produced gases, very high level of operation safety and direct storage of gases under high pressure. The work presented deals with the development of efficient PEM water electrolyzers, employing high specific surface area IrxPt1−xO2 electrocatalysts synthesized by the modified Adams fusion method. A typical three-electrode cell was used to evaluate the performance of the materials for water splitting. The performance of electrodes for oxygen evolution reaction was assessed by steady-state current–potential measurements while their electrochemical characteristics and stability were studied by cyclic voltammetry. It was found that Ir–Pt bimetallic oxide electrodes present a stable performance for oxygen evolution reaction. Their intrinsic electrocatalytic activity in combination with their large surface area and stability are quite promising for the development of economically feasible electrocatalysts for PEM water electrolyzers.