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_MLPt(100) electrodes. A systematic study performed on Pt(s)-[n(100) × (111)] and Pt(s)-[n(100) × (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.