The physical-chemical properties and electrocatalytic performance of iridium oxide in oxygen evolution

Highlights: → The calcination temperature mainly influenced the valence state of Ir. → The activity of catalyst was influenced by the valence of Ir and crystallinity. → Optimum condition was found at the thermo-decomposing temperature of 500 deg. C. → Terminal voltage of water electrolysis was 1.72 V at 80 deg. C and 2 A cm-2. - Abstract: An IrO2 anode catalyst was prepared by using the Adams method for the application of a solid polymer electrolyte (SPE) water electrolyzer. The effect of calcination temperature on the physical-chemical properties and the electrochemical performance of IrO2 were examined to obtain a low loading and a high catalytic activity of oxygen evolution at the electrode. The physical-chemical properties were studied via thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical activity was investigated by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry in 0.1 mol L-1 H2SO4 at room temperature. The optimum condition was found to be at the calcination temperature of 500 deg. C, where the total polarization reached a minimum at high current densities (>200 mA cm-2). The optimized catalyst was also applied to a membrane electrode assembly (MEA) and stationary current-potential relationships were investigated. With an optimized catalytic IrO2 loading of 1.5 mg cm-2 and a 40% Pt/C loading of 0.5 mg cm-2, the terminal applied potential difference was 1.72 V at 2 A cm-2 and 80 deg. C in a SPE water electrolysis cell.