Kinetics of the oxygen evolution reaction on NiSn electrodes in alkaline solutions

The kinetics of anodic oxygen evolution have been studied on Pd, Au and Pd + Au alloys in ultra-pure sulphuric acid and potassium hydroxide solutions and mechanisms of the processes involved are proposed. The role of barrier-layer films in determining the kinetic behaviour is demonstrated and supported by self-consistent interpretations of the Tafel slopes and the e.m.f. decay behaviour observed on open-circuit. Transient effects, characteristic of barrier-layer films, are observed when changes of the polarization current are made. At Au, and the gold-rich alloys in alkaline solution, a transition region in the currentpotential relation is observed which probably corresponds to a limiting high coverage of the electrochemically active surface with adsorbed reaction intermediates. The transition region corresponds to an onset of passive behaviour. In acid solutions, only the lower Tafel region is observed which has the same Tafel constants b and i 0 as those for the lower Tafel line in alkaline solutions indicating that the discharge process involves water rather than OH - ions, irrespective of pH. The relation of exchange currents to composition of the alloys is considered.

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A Bifunctional Iron Nickel Catalyst for the Oxygen Evolution Reaction

10.26434/chemrxiv.7246859.v1 ◽

2018 ◽

Author(s):

fang song ◽

Michael Busch ◽

Benedikt Lassalle-Kaiser ◽

Chia-Shuo Hsu ◽

Elitsa Petkucheva ◽

...

Keyword(s):

Oxygen Evolution ◽

Transition Metal Oxides ◽

Oxygen Evolution Reaction ◽

Density Functional ◽

Maximum Activity ◽

Binding Energies ◽

Alkaline Solutions ◽

Bifunctional Mechanism ◽

Scaling Relationship ◽

Covalently Linked

The oxygen evolution reaction (OER) is a key process that enables the storage of renewable energies in the form of chemical fuels. Although numerous transition metal oxides have been explored as OER catalysts, the scaling relationship of the binding energies of various surface-bound intermediates imposes a limit on the maximum activity of these oxides. While previous computational studies have suggested bifunctional catalysts might be capable of overcoming this limit, stable and non-precious catalysts of this type remain elusive. Here, we describe a catalyst that exhibits activity significantly higher than current state-of-the-art catalysts that operate in alkaline solutions, including the benchmark nickel iron oxide. This new catalyst is both easy to prepare and stable for many hours. Operando X-ray absorption spectroscopic data reveal that the catalyst is made of nanoclusters of gamma-FeOOH covalently linked to the edge sites of a gamma-NiOOH support. According to density functional theory computations, this structure allows a reaction path involving iron as the oxygen evolving center and a nearby terrace O site on the gamma-NiOOH support oxide as a hydrogen acceptor. This bifunctional mechanism circumvents the aforementioned maximum activity limit associated with the scaling relationship and leads to superior OER activity.<br>

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An Efficient Electrocatalyst for Oxygen Evolution Reaction in Alkaline Solutions Derived from a Copper Chelate Polymer via In Situ Electrochemical Transformation

Catalysts ◽

10.3390/catal10020233 ◽

2020 ◽

Vol 10 (2) ◽

pp. 233 ◽

Cited By ~ 4

Author(s):

Ridwan P. Putra ◽

Hideyuki Horino ◽

Izabela I. Rzeznicka

Keyword(s):

Oxygen Evolution ◽

Oxygen Evolution Reaction ◽

Metal Chelate ◽

Metal Oxide Nanoparticles ◽

Alkaline Media ◽

Alkaline Solutions ◽

Composite Electrodes ◽

Potential Sweep ◽

Nanocomposite Catalyst ◽

Chelate Polymer

Efficient oxygen evolution reaction (OER) electrocatalysts are highly desired in the field of water electrolysis and rechargeable metal-air batteries. In this study, a chelate polymer, composed of copper (II) and dithiooxamide, was used to derive an efficient catalytic system for OER. Upon potential sweep in 1 M KOH, copper (II) centers of the chelate polymer were transformed to CuO and Cu(OH)2. The carbon-dispersed CuO nanostructures formed a nanocomposite which exhibits an enhanced catalytic activity for OER in alkaline media. The nanocomposite catalyst has an overpotential of 280 mV (at 1 mA/cm2) and a Tafel slope of 81 mV/dec in 1M KOH solution. It has a seven-fold higher current than an IrO2/C electrode, per metal loading. A catalytic cycle is proposed, in which CuO undergoes electrooxidation to Cu2O3 that further decomposes to CuO with the release of oxygen. This work reveals a new method to produce an active nanocomposite catalyst for OER in alkaline media using a non-noble metal chelate polymer and a porous carbon. This method can be applied to the synthesis of transition metal oxide nanoparticles used in the preparation of composite electrodes for water electrolyzers and can be used to derive cathode materials for aqueous-type metal-air batteries.

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