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 G(ML)Pt(100) electrodes. A systematic study performed on Pt(s)-[n(100) x (111)] and Pt(s)-[n(100) x (110)] electrodes reveals that the feature at E-PI = 0.30 V-RHE corresponds to pure hydrogen adsorption taking place at (111) step sites vicinal to (100) domains, while the peak at E-PII = 0.36 V-RHE 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 E-PIII = 0.40 V-RHE and effectively suppresses the formation of hydroxyl at the (100) terrace at higher potentials 0.40 < E-PIV < 0.75 V-RHE. 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.