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

摘要

A series of (IrO_2)_(1-x)(Nb_2O_5)_x catalyst with Nb_2O_5 loading from 0.1-0.7 mol% was prepared by hydrolysis method and annealed at 500 °C. Electrodes of the catalyst powder was characterized in 0.5 mol dm~(-3) H_2SO_4 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 °C inverted this sequence so that the catalytic activity increased in the order IrO_2 < (IrO_2)_(0.7)(Nb_2O_5)_(0.3) < (IrO_2)_(0.9)(Nb_2O_5)_(0.1).