Influence of various metallic oxides on the kinetic of the oxygen evolution reaction on platinum electrodes

Abstract

Pt,50Pt-50RuO2 and50Pt-50IrO2 electrodes were prepared on titanium (Ti) substrate by thermal decomposition techniques. The micrographs of50Pt-50RuO2 and50Pt-50IrO2 have revealed that their surfaces are rough with cracked structures in contrast to platinum which exhibits smooth, compact and homogeneous surface. The richer the electrode surface in platinum, thinner is the crack size and also more compact is the electrode surface. The electrodes have also been characterized electrochemically by cyclic voltammetry in acidic (HClO4) and alkaline (KOH) electrolytes. These characterizations showed that the surface of the50Pt-50 RuO2 and50Pt-50IrO2 electrodes were composed of platinum and metal dioxide active sites. The Tafel slope obtained on Pt,50Pt-50RuO2 and 50Pt-50IrO2 for the oxygen evolution reaction (OER) were respectively 120, 90 and 44 mV dec-1 in acid electrolyte. In the alkaline electrolyte, they were 119, 87 and 42 mV dec-1 on Pt,50Pt-50RuO2 and50Pt-50IrO2 electrodes, respectively, indicating that for the prepared electrodes, Tafel slopes are the same in acidic and in alkaline media. Moreover, in acidic and in alkaline media, the kinetic of the oxygen evolution reaction was faster on50 Pt-50RuO2 and50Pt-50IrO2 than Pt owing to a synergetic effect of Pt and the oxides. That additional effect of the surface component50Pt-50RuO2 and50Pt-50IrO2 electrodes let them possess higher electrocatalytic activity towards OER than Pt in the two media. Though the kinetic of the oxygen evolution reaction is practically the same in acidic and alkaline media for all the electrodes, OER occurred at lower overpotential in alkaline electrolyte than in acidic electrolyte on the prepared electrodes.