Structure and characteristics of Ti/IrO_2(x) + MnO_2(1 - x) anode for oxygen evolution

摘要

The Ti/IrO_2(x) + MnO_2(l - x) anodes were prepared by thermal decomposition of a mixed H_2IrCl_6 and Mn(NO_3)_2 hydrosolvent Field emission scanning electron microscopes (FESEM) showed nano IrO_2 poles separated out of the Ti/IrO_2(x) + MnO_2(1 - x) coating surfaces and formed nano IrO_2 array in the local region, especially at the surface of the Ti/IrO_2(0.5) + MnO_2(0.5) and Ti/IrO_2(0.7) + MnO2(0.3) anodes prepared at 400 deg C. The physical phases and crystallite orientations of the IrO_2(x) + MnO_2(1 - x) coatings were identified by X-ray diffraction (XRD). The resistivity of the IrO_2(x) + MnO_2(1 - x) coatings descended with the increase of IrO_2 content in the coating. Cyclic voltammetry (CV) has been used to investigate the electrochemical behavior of the IrO_2(x) + MnO_2(1 - x) electrodes in acid Solution. The reaction mechanism of O_2 evolution on the IrO_2(x) + MnO_2(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 H_2SO_4 solutions at 40 deg C with a constant anodic current density of 2 A/cm~2. The Ti/IrO_2(0.7) + MnO_2(0.3) anode prepared at 400 deg C has the highest service life of 900 h.