Robust Polyoxometalate/Nickel Foam Composite Electrodes for Sustained Electrochemical Oxygen Evolution at High pH

Abstract

The development of technologically viable electrodes for the electrochemical oxygen evolution reaction (OER) is a major bottleneck in chemical energy conversion. This article describes a facile one-step hydrothermal route to deposit microcrystals of a robust Dexter-Silverton polyoxometalate oxygen evolution catalyst, [Co_6.8 Ni_1.2 W₁₂ O₄₂ (OH)₄ (H₂ O)₈ ], on a commercial nickel foam electrode. The electrode shows efficient and sustained electrochemical oxygen evolution at low overpotentials (360 mV at 10 mA cm^-2 against RHE, Tafel slope 126 mV dec^-1 , faradaic efficiency (96±5) %) in alkaline aqueous solution (pH 13). Post-catalytic analyses show no mechanical or chemical degradation and no physical detachment of the microcrystals. The results provide a blueprint for the stable "wiring" of POM catalysts to commercial metal foam substrates, thus giving access to technologically relevant composite OER electrodes.

Keywords: electrocatalysis; metal oxides; oxygen evolution reaction; polyoxometalates; self-assembly.