Composite Thin Film Iridium- Niobium Oxide Electrocatalysts for the Oxygen Evolution Electrode

Abstract

A series of (IrO2)1-x(Nb2O5)x catalyst with Nb2O5 loading from 0.1-0.7 mol% was prepared by hydrolysis method and annealed at 500 ºC. Electrodes of the catalyst powder was characterized in 0.5 mol dm− 3 H2SO4 by cyclic voltammetry (CV) and quasi steady-state polarisation measurements (LSV). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicated a phase separation into iridium oxide and niobium pentoxide in the catalyst for all compositions and forms composite oxide rather than a solid solution. In line with this, at room temperature the catalytic activity decreased with increasing niobium content in the catalyst. However, raising the temperature to 80 oC inverted this sequence so that the catalytic activity increased in the order IrO2 < (IrO2)0.7(Nb2O5)0.3 < (IrO2)0.9(Nb2O5)0.1.