Structure and characteristics of Ti/IrO2(x) + MnO2(1 -x) anode for oxygen evolution

The Ti/IrO2(x) + MnO2(1 - x) anodes were prepared by thermal decomposition of a mixed H2IrCl6 and Mn(NO3)2 hydrosolvent. Field emission scanning electron microscopes (FESEM) showed nano IrO2 poles separated out of the Ti/IrO2(x) + MnO2(1 - x) coating surfaces and formed nano IrO2 array in the local region, especially at the surface of the Ti/IrO2(0.5) + MnO2(0.5) and Ti/IrO2(0.7) + MnO2(0.3) anodes prepared at 400 deg C. The physical phases and crystallite orientations of the IrO2(x) + MnO2(1 - x) coatings were identified by X-ray diffraction (XRD). The resistivity of the IrO2(x) + MnO2(1 - x) coatings descended with the increase of IrO2 content in the coating. Cyclic voltammetry (CV) has been used to investigate the electrochemical behavior of the IrO2(x) + MnO2(1 - x) electrodes in acid solution. The reaction mechanism of O2 evolution on the IrO2(x) + MnO2(1 - x) electrodes was studied by polarization curve. Tafel lines displayed two distinct linear regions with one of the slope close to 62 mV dec-1 in the low potential region and the other close to 135 mV dec-1 in the high potential region. The accelerated lifetime test was measured in 0.5 M H2SO4 solutions at 40 deg C with a constant anodic current density of 2 A/cm2. The Ti/IrO2(0.7) + MnO2(0.3) anode prepared at 400 deg C has the highest service life of 900 h.