The influence of solution composition on the kinetics of “reduced” CO2 electrooxidation at polycrystalline platinum

The electrooxidationof “reduced” CO₂ intermediate adsorbed at polycrystalline Pt was studied for comparison in 0.5 M H₂SO₄, 0.05 M HClO₄ and 1 M KOH. The voltammograms showed a current peak multicity in 0.05 M HClO₄ and in 1 M KOH. Current transients in 0.05 M HClO₄ showed a complex decay at E_o, between 0.6 and 0.8 V. In 1 M KOH these transients showed a minimum and a maximum which shift in the time scale with E_ad.The kinetic interpretation of the results was attempted considering a Temkin isotherm at low positive potentials. Tafel slopes obtained from the dependence of E_p vs. log υ are close to RT/F at high positive potentials. This value accounts for a chemical reaction as rds. Anion Adsorption at the polycrystalline Pt electrode would change the surface energy for Pt(OH) electroformation and hence it should influence the electrooxidation processes indirectly.