Deconvolution of the Voltammetric Features of a Pt(100) Single-Crystal Electrode

The Pt(100) single-crystal electrode shows four voltammetric features in acid electrolytes, but the precise corresponding surface phenomena remain unresolved. Herein, a deconvolution of the classical "hydrogen region" from the "hydroxyl and anion region" is attempted by the comparison of voltammetric behavior of Pt(100) and GMLPt(100) electrodes. A systematic study performed on Pt(s)-[n(100) × (111)] and Pt(s)-[n(100) × (110)] electrodes reveals that the feature at EPI = 0.30 VRHE corresponds to pure hydrogen adsorption taking place at (111) step sites vicinal to (100) domains, while the peak at EPII = 0.36 VRHE actually involves hydroxyl replacing hydrogen at (100) domains. An analysis examined for H2SO4, HClO4, CH3SO3H, and HF demonstrates that the specific (H)SO4– adsorption commences at EPIII = 0.40 VRHE and effectively suppresses the formation of hydroxyl at the (100) terrace at higher potentials 0.40 < EPIV < 0.75 VRHE. Non-specifically adsorbing anions (ClO4−, CH3SO3− and F−) would only interact with the hydroxyl phase formed on the Pt(100) terrace in both potential regions.