Electrodes For Oxygen Evolution Reaction Research Articles

Failure Analysis of Nickel-Coated Anodes in Zinc-Air Hybrid Flow Batteries

A zinc-air flow battery system pumps "fuel” (a zinc particle/KOH slurry) from a fuel tank to a fuel cell stack, where the zinc particles are combined with oxygen from the air to form zincate ions and produce electricity. The zincate-rich electrolyte is then returned to the fuel tank. During the charging cycle, the electrolyte is passed to the zinc regenerator, where electricity (from renewable sources such as solar or wind) is utilized to convert the zincate ions to zinc particles. The regenerated fuel is pumped back into the fuel tank for the discharge process.Nickel is considered for use as the anode during zinc regeneration as it has been shown to be an active catalyst for the oxygen evolution reaction (OER). However, nickel electrodes pose manufacturing challenges due to machinability issues. Alternatively, nickel can be coated on a machinable metal substrate to improve scalability. These electrodes are subjected to open circuit voltage (OCV), OER, and the hydrogen evolution reaction (HER) during operation of zinc-air flow batteries. The electrodes have been observed to fail during prolonged voltage cycling due to nickel coating delamination, which manifests itself as blistering, flaking, and discoloration. It is hypothesized that this may be due to electrolyte penetration into the pores of the nickel coating during operation. The present work is aimed at analyzing and mitigating the coating delamination process through characterization of various Ni coating recipes. As-fabricated and cycled electrodes are characterized using various microstructural techniques, including optical microscopy, x-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and x-ray tomography. Coated electrodes are also evaluated electrochemically and the results are correlated with the microstructural analysis. The overall goal of the work is to understand the failure mechanisms and apply the knowledge to fabricate improved coatings for OER electrodes.

Low Cost Electrodes for Alkaline Water Electrolysis

To succeed with the green transition, one must have cheap and reliable ways to store intermittent renewable energy. It is believed that hydrogen will play a key role in this regard, preferably through electrochemical water splitting. Alkaline water electrolysis is a mature technology, using nickel materials in most key components. Although Ni and Ni-S are active materials towards the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, it is desirably to develop more active, durable and cheaper electrodes through a simple activation procedure of low-Ni containing materials. Moureaux et al. [1, 2] and Schäfer et al. [3] have shown that cheap stainless steel electrodes can be activated through electrooxidation in high pH electrolytes creating a nickel enriched surface.In this work we have employed a similar activation procedure, activating SS316 at 1.7 V for 18 hours at room temperature in a 3-electrode electrochemical cell using electrolytes with various KOH concentrations. The surface composition was analyzed with XPS and GD-OES before and after activation, and revealed that the Ni content in the surface increased with increasing KOH, at the expense of Fe and Cr. The composition converged to 73% Ni and 27% Fe for KOH concentration of 7.5 and higher. This composition showed the best OER performance of all surfaces prepared, including pure Ni electrodes. A similar enrichment of Ni was observed for SS304, reaching the same surface composition as SS316. However, the Ni content in the surface after activation changed less and was lower than SS316 and SS304 after activation for plate materials with higher nominal Ni bulk composition (Inconel718, Incoloy800 and NiFe 50:50 alloy). Hence, the surface composition can be tuned by selecting an electrode material and pH of the activation electrolyte.Furthermore, we have tested the activated SS316 electrodes at relevant operating conditions in a single cell alkaline water electrolyzer test rig (30wt% KOH, 80°C and 9 bar) and compared it with Ni and as-received SS316 electrodes. The activated SS316 electrodes outperformed the other electrodes and showed a stable performance during 255 hours operation at 0.8 A cm-2. The OER electrode activation procedure was successfully attempted in-situ in the alkaline single cell water electrolyzer test rig. However, the application of high currents needed for the activation led to high cell voltages (3 V) and hence harmful conditions.Finally, the effect of the activation procedure on the HER performance was also investigated and tied to the purity of the electrolyte. Deposition of Cu and Fe metal impurities was observed on the HER electrode, which increased with a lower grade of the KOH electrolyte. HER activity was observed to increase after activation in low grade KOH, which was attributed to an increased surface area and higher Fe to Cu ratio in the deposit.[1] F. Moureaux, P. Stevens, G. Toussaint, M. Chatenet, J. Power Sources 229 (2013) 123-132.[2] F. Moureaux, P. Stevens, G. Toussaint, M. Chatenet, Appl. Catal. B-Environ 258 (2019) 117963.[3] H. Schäfer, D.M. Chevrier, P. Zhang, J. Stangl, K. Müller‐Buschbaum, J.D. Hardege, K. Kuepper, J. Wollschläger, U. Krupp, S. Dühnen, Adv. Funct. Mater. 26 (2016) 6402-6417.

Low‐cost Trimetallic Ni‐Fe‐Mn Oxides/(Oxy)hydroxides Nanosheets Array for Efficient Oxygen Evolution Reaction

AbstractThe development of low‐cost, efficient, and stable water oxidation electrocatalyst is of great importance for hydrogen production. Herein, we report an approach to convert commercial stainless steel plate (SSP) into trimetallic Ni‐Fe‐Mn oxides/hydroxides nanosheets (NiFeMnOxHy‐SSP) as an oxygen evolution reaction (OER) electrode. The NiFeMnOxHy‐SSP exhibits excellent OER performance with an overpotential of 232 mV at 10 mA cmgeo−2, a Tafel slope of 37.6 mV dec−1, and long‐term stability (100 h) in 1.0 M KOH aqueous solution. The electrochemical results reveal that the Mn plays a significant role in reducing overpotential and improving stability at 500 mA cmgeo−2 for OER. This work provides a facile way to fabricate OER electrodes by surface modification of SSP towards industrial water splitting.

Molecular Regulation Based on Functional Trimetallic Metal-Organic Frameworks for Efficient Oxygen Evolution Reaction.

Metal-organic frameworks (MOFs) as classic crystalline porous materials have attracted great interest in the catalytic field. However, how to realize molecular regulation of the MOF structure to achieve a remarkable oxygen evolution reaction (OER) electrocatalyst is still a challenge. Herein, we designed several series of special MOF materials to explore the relationship between the structure and properties as well as the related reactive mechanism. First, various metal centers, including Fe, Co, Ni, Zn, and Mg, were utilized to construct the first series of trimetallic MOF materials, namely, M3-MOF-BDC, where BDC = 1,4-benzenedicarboxylic acid, also known as terephthalic acid. Among of them, Fe3-MOF-BDC shows the best OER performance and only needs an overpotential of 312 mV at 10 mA cm-2. Then, functional BDC-X ligands (X = NH2, OH, NO2, DH) with various characteristic groups were selected to construct a new series, namely, Fe3-MOF-BDC-X, to further improve its OER electrocatalytic performance. As expected, Fe3-MOF-BDC-NH2 exhibited a greatly enhanced OER performance with ultralow Tafel slopes of 45 mV dec-1 and overpotentials of 280 mV at 10 mA cm-2 when the BDC-NH2 ligand was adopted, even superior to commercial IrO2 (323 mV) and most of the reported pristine MOFs as OER electrodes. Much higher structural stability was proven. The detailed structure-property relationship and mechanism are discussed. In a word, this work provides a very important theoretical basis for the design and exploration of new MOF electrocatalysts.

Self-Supporting NiFe Layered Double Hydroxide “Nanoflower” Cluster Anode Electrode for an Efficient Alkaline Anion Exchange Membrane Water Electrolyzer

The development of an efficient and durable oxygen evolution reaction (OER) electrode is needed to solve the bottleneck in the application of an anion exchange membrane water electrolyzer (AEMWE). In this work, the self-supporting NiFe layered double hydroxides (NiFe LDHs) “nanoflower” cluster OER electrode directly grown on the surface of nickel fiber felt (Ni fiber) was synthesized by a one-step impregnation at ambient pressure and temperature. The self-supporting NiFe LDHs/Ni fiber electrode showed excellent activity and stability in a three-electrode system and as the anode of AEMWE. In a three-electrode system, the NiFe LDHs/Ni fiber electrode showed excellent OER performance with an overpotential of 208 mV at a current density of 10 mA cm−2 in 1 M KOH. The NiFe LDHs/Ni fiber electrode was used as the anode of the AEMWE, showing high cell performance with a current density of 0.5 A cm−2 at 1.68 V and a stability test for 200 h in 1 M KOH at 70 °C. The electrocatalytic performance of NiFe LDHs/Ni fiber electrode is due to the special morphological structure of “nanoflower” cluster petals stretching outward to produce the “tip effect,” which is beneficial for the exposure of active sites at the edge and mass transfer under high current density. The experimental results show that the NiFe LDHs/Ni fiber electrode synthesized by the one-step impregnation method has the advantages of good activity and low cost, and it is promising for industrial application.

Electroplated Ni-Fe Layer on Stainless Steel Fiber Felt as an Efficient Electrode for Oxygen Evolution Reaction

Electroplated Ni-Fe Layer on Stainless Steel Fiber Felt as an Efficient Electrode for Oxygen Evolution Reaction

Metal-Functionalized Hydrogels as Efficient Oxygen Evolution Electrocatalysts.

Conductive polymer hydrogels have large surface areas and electrical conductivities. Their properties can be further tailored by functionalizing them with metals and nonmetals. However, the potential applications of metal-functionalized hydrogels for electrocatalysis have rarely been investigated. In this work, we report the synthesis of transition-metal-functionalized polyaniline-phytic acid (PANI-PA) hydrogels that show efficient electrocatalytic activities for the oxygen evolution reaction (OER). Among the many transition metals studied, Fe is accommodated by the hydrogel the most due to the favorable affinity of the PA groups in the hydrogel for Fe. Meanwhile, those containing both Fe and Co are found to be the most effective electrocatalysts for OER. The most optimized such hydrogel, NF@Hgel-Fe0.3Co0.1, which is made using a solution that has a 3:1 ratio of Fe and Co, needs an overpotential of only 280 mV to catalyze OER in 1 M KOH solution with a current density of 10 mV cm-2. Furthermore, these metal-functionalized PANI-PA hydrogels can easily be loaded on the nickel foam or carbon cloth via a simple soak-and-dry method to generate free-standing electrodes. Overall, this work demonstrates a facile synthesis and fabrication of sustainable and efficient OER electrocatalysts and electrodes that are composed of easily processable hydrogels functionalized with earth-abundant transition metals.

The use of silica in IrO2-based DSA type electrode: An efficient approach to construct cost-effective, potent electrodes for oxygen evolution reaction

Two types of coating, coatings, i.e. IrO2–Ta2O5/Ti and IrO2–Ta2O5–SiO2/Ti were fabricated by the sol-gel method to investigate the effect of silica on the electrode characteristics. The characterization of the coatings was performed by the scanning electron microscope (SEM), energy dispersive X-ray spectroscopy mapping (EDS), and X-ray diffraction (XRD). The analysis of surface morphology indicated that the presence of SiO2 in the coatings decreased the size of cracks, where the minimum crack size was observed for the coating containing 35% of SiO2. The catalytic activities of the prepared electrodes to conduct the oxygen evolution reaction were evaluated in 0.5 M H2SO4 solution by electrochemical measurements including cycling voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrodes constructed were named hereafter as IT-0, ITS-35, and ITS-55 with the compositions of IrO2 (70%)-Ta2O5 (30%)/Ti, IrO2 (35%)-Ta2O5 (30%)-SiO2 (35%)/Ti and IrO2 (15%)-Ta2O5 (30%)-SiO2 (55%)/Ti, respectively. The accelerated lifetimes measured for the IT-0, ITS-35, and ITS-55 electrodes were obtained as 210, 230, and 173 h, respectively. Such a result was remarkable from the point of view that the optimization of SiO2 quantity in the coating composition not only decreased the content of IrO2 but also improved the stability of the electrode. Furthermore, the resulted electrode (ITS-35) exhibited no significant reduction in its catalytic activity when compared to the electrode with a higher amount of IrO2 (IT-0). Due to the high service lifetime of prepared electrodes, these electrodes are good candidates for OER processes such as electrowinning.

Rational structure design of FeCo-based materials as efficient electrodes for overall water-splitting

Rational design of efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential to promote the performance of overall water-splitting. In this work, we demonstrate the high performance electrolyzer by using Fe–Co phosphide grown on Ni foam (FeCoP/NF) as HER electrode and self-supported FeCo2O4@FeCo2S4/NF heterostructure as OER electrode. Thanks to the more active sites and faster charge transfer capability, the FeCoP/NF electrode can deliver low HER overpotentials of 59.6 and 233.6 mV at 10 and 100 mA cm[Formula: see text]. Furthermore, the synergistic effect at interfaces also endows low overpotentials of FeCo2O4@FeCo2S4/NF at specific current densities. As a result, the designed FeCoP/NF——FeCo2O4@FeCo2S4/NF device just needs a voltage of 1.52 V to afford 10 mA cm[Formula: see text], indicating greatly potential in practical application.

Cooperative electrocatalytic effect of Pd and Ce alloys nanoparticles in PdCe@CNWs electrode for oxygen evolution reaction (OER)

Electrocatalytic water oxidation is an ecofriendly and intelligent approach for oxygen evolution from water because it requires only water and electrical potential/energy as inputs. However, the oxygen evolution reaction (OER) is the most challenging multi-electron and proton transfer reaction during water electrolysis for hydrogen production. The electrocatalyst is the critical component that controls the efficiency of oxygen evolution. Therefore, it is essential to explore efficient and durable electrocatalysts that must have significant efficiency compared to the benchmark catalyst (i.e., RuO2) for OER. Herein, self-supported carbon nanowires (CNWs) decorated with bimetallic palladium-cerium PdCe alloys nanoparticles (NPs) were synthesized through an electrospinning-thermal carbonation approach to overcome the kinetic barriers and deliver decent alkaline OER activity. As a result, the PdCe/CNWs requires a low overpotential of ∼360 and ∼450 mV vs. RHE to deliver the current density of 10 and 50 mA/cm2 with low Tafel slope (62 mV/dec) for OER, which is even comparable to the benchmark, RuO2 (360 mV and 73 mV/ dec). Notably, only a slight increase (∼ 10 %) in overpotential was observed after 10,000 cycles indicating high electrocatalyst stability. The high stability and improved OER performance of the PdCe/CNWs electrode can be explained by the cooperative catalytic influence between Pd, Ce, and C species.

ZIF67@MoO3 NSs@NF composite electrocatalysts reinforced by chemical bonds and oxygen vacancy for efficient oxygen evolution reaction and overall water-splitting

A kind of composite electrocatalysts with the structure of MoO 3 nanosheets coated by ZIF67 nanocrystals and grown on the nickel foam substrate (ZIF67@MoO 3 NSs@NF) is prepared and mainly used as the electrode for oxygen evolution reaction (OER) and overall water splitting. The excellent electrocatalytic activity of ZIF67@MoO 3 NSs@NF are demonstrated. It can use the overpotential (ƞ) of 178 mV and 386 mV respectively to drive 10 mA cm −2 and 50 mA cm −2 . It is also observed that the ZIF67@MoO 3 NSs@NF electrode has the highest initial current density (45.7 mA cm −2 ) at 1.618 V and can maintain more than 90% of the initial current density after 20,000 s. The ZIF67@MoO 3 NSs@NF electrode also shows the small HER overpotential of 135 mV at 10 mA cm −2 . Furthermore, the voltage of ZIF67@MoO 3 NSs@NF as a bifunctional overall water splitting catalysts is 1.58 V at 10 mA cm −2 , which is superior to another noble metal electric catalyst combination RuO 2 /NF(+)//Pt–C/NF(−). And the ZIF67@MoO 3 NSs@NF(+)//ZIF67@MoO 3 NSs@NF(−) combination can maintain more than 90% of the initial current density after 65,000 s at 1.58 V. The main reason is the composite interface of MoO 3 NSs and ZIF67 phases with Co–O bonds, C–O–Mo bonds and oxygen vacancies defects facilitates the increase of the active sites and efficient electron transfer rate. • The composite structure of MoO 3 nanosheets grown on NF and coated by ZIF67 are prepared. • The ZIF67@MoO 3 NSs@NF can use the overpotential(ƞ) of 178 mV to drive 10 mA cm −2 . • It can maintain 90% of the initial current density after 65,000 s for overall water-splitting. • Chemical bonds and oxygen vacancy facilitates the increase of the active sites. • Non-highly conductive oxides can also promote the electrocatalytic activity of MOF composite.

Electrochemical deposited amorphous FeNi hydroxide electrode for oxygen evolution reaction

The electrodeposition approach is significant in electrode fabrication for practical application. Herein, the electrodeposited amorphous NiFe hydroxide species for oxygen evolution reaction (OER) in water splitting reaction is demonstrated by revealing the synergistic effect influenced by the support electrode of Fe and Ni foil and the contents of Fe and Ni in the electrolyte. All the electrodeposited samples have an amorphous structure and similar profiles of binding energy and chemical states for Fe and Ni as characterized by the spectroscopic techniques. While the support effect and Fe/Ni synergistic effect are indeed observed for the varied catalytic performances observed for the different electrodes; the Ni foil supported catalyst exhibits much higher performance than that of the Fe foil supported catalyst, and the different redox potentials of Ni species in the different Fe/Ni electrode resulting from the Fe–Ni synergism are observed in the cyclic voltammetry curve analysis. The surface roughness and the electrochemical surface area are also influenced by the support effect and the Fe/Ni ratio in the plating electrolyte. The optimal electrode shows a very low overpotential of ∼200 mV to reach 10 mA cm−2, and very high catalytic stability by the consecutive cyclic voltammetry measurements and 20 h stability test. Though it has the largest electrochemical surface area, the highest catalytic efficiency for these active sites is also indicated by the specific activity and turnover frequency polarization curves. The current work shows the effective experience for the electrodeposited Fe/Ni based catalysts in large-scale fabrication, which can be more practical for hydrogen generation in the alkaline water electrolysis.

Dynamic active site evolution and stabilization of core-shell structure electrode for oxygen evolution reaction

In robust oxygen evolution reaction (OER), the irregular transition metal atom migration at the catalyst-electrolyte interface disrupts the durability of the surface electronic structure. Herein, we induce the orderly migration of metal elements from core to the surface of NiCo2O4@FeOx model electrode to overcome the instable element balance between metal dissolution and deposition. In OER working potential, the driving force of concentration gradient on Ni element migration can be strengthen by the shuttle of miniscule oxygen intermediates in the bulk phase, which promotes the changes of metal species (Ni or Co) and migration direction, further optimizing the surface oxide state. Consequently, the resulting electrode would stabl react over 50,000 CV cycles as well as continued test for 300 h at current density of 100 mA cm−2.

3D-printed NiFe-layered double hydroxide pyramid electrodes for enhanced electrocatalytic oxygen evolution reaction

Electrochemical water splitting has been considered one of the most promising methods of hydrogen production, which does not cause environmental pollution or greenhouse gas emissions. Oxygen evolution reaction (OER) is a significant step for highly efficient water splitting because OER involves the four electron transfer, overcoming the associated energy barrier that demands a potential greater than that required by hydrogen evolution reaction. Therefore, an OER electrocatalyst with large surface area and high conductivity is needed to increase the OER activity. In this work, we demonstrated an effective strategy to produce a highly active three-dimensional (3D)-printed NiFe-layered double hydroxide (LDH) pyramid electrode for OER using a three-step method, which involves direct-ink-writing of a graphene pyramid array and electrodeposition of a copper conducive layer and NiFe-LDH electrocatalyst layer on printed pyramids. The 3D pyramid structures with NiFe-LDH electrocatalyst layers increased the surface area and the active sites of the electrode and improved the OER activity. The overpotential (η) and exchange current density (i0) of the NiFe-LDH pyramid electrode were further improved compared to that of the NiFe-LDH deposited Cu (NiFe-LDH/Cu) foil electrode with the same base area. The 3D-printed NiFe-LDH electrode also exhibited excellent durability without potential decay for 60 h. Our 3D printing strategy provides an effective approach for the fabrication of highly active, stable, and low-cost OER electrocatalyst electrodes.

Metal substrates activate NiFe(oxy)hydroxide catalysts for efficient oxygen evolution reaction in alkaline media

The amorphous NiFeOx(OH)y is synthesized on Fe, Ni, and Cu foam substrates to study the effects of the metal substrates on activity and stability for the electrochemical oxygen evolution reaction (OER) from water. The metal substrate for NiFeOx(OH)y catalyst does not merely perform the physical role of loading the catalyst, but actively participates in the activation process of the catalyst phase by controlling the charge transfer during the OER. The Ni foam substrate is found to be the best to make NiFeOx(OH)y/Ni foam the most active and the most stable electrode for OER in an alkaline medium due to its multiple functions. The nickel substrate forms the thinnest oxide layer on its surface to allow facile charge transfer, and stabilizes the M–Ox(OH)y structure of high oxidation degree of metals and balanced Ox/(OH)y responsible for excellent OER performance. The high intrinsic corrosion resistance of Ni and its ability to stabilize a thick layer of M–Ox(OH)y structure can also minimize the metal dissolution during the OER and provide superior long-term stability. Finally, oxidation of the Ni substrate itself results in more NiOOH phase formation to achieve an optimum NiFe composition.

Plasma Nitrided Cocrfenimn High Entropy Alloy Coating as a Self-Supporting Electrode for Oxygen Evolution Reaction

Plasma Nitrided Cocrfenimn High Entropy Alloy Coating as a Self-Supporting Electrode for Oxygen Evolution Reaction

Preparation of Practical High-Performance Electrodes for Acidic and Alkaline Media Water Electrolysis.

The synthesis of electrocatalyst and the electrode preparation were merged into a one‐step process and proved to be a versatile method to synthesize metal oxide electrocatalysts on the conductive carbon paper (CP). Very simply, the metal precursor deposited on the CP was thermally treated by a torch‐gun for just 6 s, resulting in the formation of RuO2, Co3O4, and mixed oxide nanoparticles. The material could be directly used as working electrode for oxygen evolution reaction (OER). Compared with commercial and other state‐of‐the‐art electrocatalysts, the fabricated electrode showed a superior electrocatalytic activity for OER in 1 m HClO4 and 1 m KOH in terms of not only a low overpotential to reach 10 mA cm−2 but also a high current density at 1.6 VRHE with satisfying a long‐term stability. The novel strategy without requiring time‐consuming and uneconomical steps could be expanded to the preparation of various metal oxides on conductive substrates towards diverse electrocatalytic applications.

Facile synthesis of black phosphorus directly grown on carbon paper as an efficient OER Electrocatalyst: Role of Interfacial charge transfer and induced local charge distribution

Black phosphorus (BP), as a new 2D material, is normally synthesized by a high-pressure and high-temperature (HPHT) method from white and red phosphorus, which severely hinders the further development of BP for any potential applications and leads to search for other potential applications of BP with big challenge. Herein, we develop a facile and efficient Thermal-Vaporization-Transformation (TVT) approach to prepare a highly active BP directly grown on carbon paper as the electrode for Oxygen evolution reaction (OER), showing a low onset potential of 1.45 V versus RHE. Simultaneously, the current density of BP-CP illustrates the excellent electro-catalysis stability only decreases by 3.4% after continuous operation for 10000 s. Meanwhile, the density functional theory (DFT) calculations further illustrates the P-doped carbon layer in the upper side of BP layer is actually responsible for its enhanced OER property, and the adjacent carbon atoms of the embedded P atoms are actually the active sites due to the induced local change distribution by intramolecular change transfer. Considering the facile, but efficient and scalable, TVT approach can directly synthesize BP-CP with excellent OER performance, which is promising for BP electrocatalysts used for OER in metal-air batteries, fuel cells, water-splitting devices, even other key renewable energy.

Electrochemically Fabricated Superhydrophilic/Superaerophobic Manganese Oxide Nanowires at Discontinuous Solid–Liquid Interfaces for Enhanced Oxygen Evolution Performances

AbstractThe design of an electrode surface is critical to the oxygen evolution reaction (OER) during electrochemical water splitting since the catalytic activity depends strongly on surface characteristics, such as the coating uniformity of the catalysts, electrolyte wetting, and the gas‐bubble release ability. Here, nonprecious‐metal electrocatalysts (MnO nanowires) are electrochemically deposited on the surface of a porous gold microgrid. The discontinuous solid–liquid contact lines, which are formed by the microgrids during the liquid‐phase electrochemical reaction, generate MnO nanowires with high coating uniformity. The micro/nanostructure of the electrode induces a superhydrophilic surface, which facilitates the wetting of the alkaline electrolyte and increases the electrochemical active surface area. Simultaneously, the underwater superaerophobicity of the electrode promotes the release of the oxygen products, thus reducing the occupation of the catalytic sites by the gas bubbles. The synergistic effect of electrolyte wetting and gas release ensures that this superhydrophilic/superaerophobic electrode exhibits a current density of 10 mA cm−2 for the OER at an overpotential of 530 mV in 0.1 m KOH, placing the catalyst among the best MnO catalysts for OER. This work avails a new basis for synergistically optimizing the synthesis methods (electrolyte wetting and gas‐bubble release) toward high‐performance OER electrodes.

Elctrocatalytic oxygen evolution reaction on Mg, Al and Fe doped spinel oxides

Metal doped cobalt-base spinel type catalysts were prepared by co-precipitation route are considered suitable candidates for OER, ORR, metal air batteries, fuel cells, detoxification of water etc. For the purpose, metal doped oxides with formula MCo 2 O 4 , M= Mg, Al and Fe were prepared thermal decomposition of their metal carbonate precipitates and characterized by IR, XRD, CV, EIS and Tafel polarization techniques. The IR spectra of oxides showed absorption bands 650 cm -1 and 560 cm -1 for respective stretching and bending modes of vibration of Co-O bond at octahedral sites and formation of nano-size ( 18 nm) single phase cubical crystal with spinel geometry was confirmed by XRD powder patterns. The cyclic voltammetric (CV) curves of oxide electrodes in 1 M KOH solution showed a redox peak at E o = 434 -516 mV for Co 2+ /Co 3+ reactions. The electrocatalytic activity of oxide electrodes for oxygen evolution reaction in 1M KOH at 25 0 C was also studied by Tafel polarization technique and polarization curve of each oxides showed two Tafel slopes ( 63 and 115 mV/decade) and order of OER is unity.