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

Pt, ₅₀Pt-₅₀RuO₂ and ₅₀Pt-₅₀IrO₂ electrodes were prepared on titanium (Ti) substrate by thermal decomposition techniques. The micrographs of ₅₀Pt-₅₀RuO₂ and ₅₀Pt-₅₀IrO₂ have revealed that their surfaces are rough with cracked structures. That of platinum was smooth, compact and homogeneous. 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 acid (HClO₄) and in alkaline (KOH) electrolytes. These characterizations showed that the surface of the ₅₀Pt-₅₀RuO₂ and ₅₀Pt-₅₀IrO₂ electrodes were composed by 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 in acid electrolyte. In the alkaline electrolyte, they were 119, 87 and 42 mV/dec respectively on Pt, ₅₀Pt-₅₀RuO₂ and ₅₀Pt-₅₀IrO₂ electrodes indicating that for the prepared electrodes, Tafel slopes are the same in acid and in alkaline media. Moreover, in acid and in alkaline media, the kinetic of the oxygen evolution reaction was rapid on ₅₀Pt-₅₀RuO₂ and ₅₀Pt-₅₀IrO₂ than Pt owing to a synergetic effect of Pt and the oxides. That additional effect of the surface component ₅₀Pt-₅₀RuO₂ and ₅₀Pt-₅₀IrO₂ electrodes let them possess high 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.

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