Step density dependence of CO2 reduction rate on Pt(S)-[n(111)x(111)] single crystal electrodes

CO2 reduction was studied by voltammetry with Pt single crystal electrodes of Pt(S)-[n(111) x (111)] at constant potentials. The rate of CO formation depends on crystal orientation as below; Pt(110) > Pt(331) > Pt(221) > Pt(332) > Pt(997) > Pt(111). The initial rates of the CO formation plotted against the amount of adsorbed hydrogen (Q(H)(0) gave a maximum of around Q(H)(0) = 40 mu C cm(-2) on the electrodes with high step density, Pt(110), Pt(331) and Pt(221), whereas the electrodes with low step density, Pt(332), Pt(997) and Pt(lll), showed monotonous increase with Q(H)(0). The activity series shown above was well correlated with the step density of crystal orientations except Pt(110)(1 x 2). The correlation and the anomalously high activity of Pt(110) are discussed with regard to the adsorption sites for hydrogen atoms with reference to UHV works in literatures. Reduction of CO2 proceeds with adsorbed hydrogen regenerated on the adsorption sites. Copyright (C) 1996 Elsevier Science Ltd.