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

IrOx+RhOx mixed oxide layers on a Ti support were prepared by thermal decomposition at 450 degrees C over the whole composition range. The temperature range 450-600 degrees C was explored for the composition 30 mol% RhOx . Samples were characterized by means of SEM, XPS, cyclic voltammetry and polarization curves. Their electrocatalytic properties were tested for the H-2 evolution reaction. The following experimental parameters were scrutinized: voltammetric charge, Tafel slope, reaction order (H+), electrical resistance of electrocatalysts. The electrocatalytic properties were evaluated at constant potential as a function of temperature as well as of composition. The electrode stability was assessed by comparing CV curves before and after groups of experiments. A reaction mechanism has been proposed. RhOx is more active than IrO (x) , its effect showing up for compositions > 30 mol%.