Effect of composition on the surface and electrocatalytic properties of Ti/IrOx +RhOx electrodes: H2 evolution from acidic solution

IrO x +RhO x mixed oxide layers on a Ti support were prepd. by thermal decompn. at 450 ?C over the whole compn. range. The temp. range 450-600 ?C was explored for the compn. 30 mol% RhO x . Samples were characterized by means of SEM, XPS, cyclic voltammetry and polarization curves. Their electrocatalytic properties were tested for the H2 evolution reaction. The following exptl. parameters were scrutinized: voltammetric charge, Tafel slope, reaction order (H+), elec. resistance of electrocatalysts. The electrocatalytic properties were evaluated at const. potential as a function of temp. as well as of compn. The electrode stability was assessed by comparing CV curves before and after groups of expts. A reaction mechanism has been proposed. RhO x is more active than IrO x , its effect showing up for compns. >30 mol%.