The Difference in Electrocatalytic Activity between Pt(110)–(1×2) and Pt(110)–(1×1) Surfaces for Methanol Electrooxidation in an Acidic Medium

Abstract

The impact of Pt(110) reconstruction on the methanol oxidation reaction in 0.1 M HClO₄ solution was investigated by combining cyclic voltammetry, blank solution replacement, intermediate CO stripping, and in situ Fourier transform infrared spectroscopy. Distinct CO accumulation and CO₂ formation behaviors were identified on three different Pt(110) surfaces: (1×2), (1×1), and mixed (1×1, 1×2). The Pt(110)−(1×2) surface exhibits the relatively weak poisoning and high current of electro-oxidation in high applied potential, respectively, whereas Pt(110)−(1×1) is severely poisoned by strongly adsorbed CO with a peak adsorption intensity at the potential of 0.20 V (vs. RHE), which leads to kinetically hindered oxidation in high applied potential. Density functional theory calculations reveal that the (1×1) surface exhibits the lower activation energy for CO formation via methanol dehydrogenation, lower adsorption free energy of both CO and OH, and the higher activation energy for CO removal by OH, for explaining its more serious CO poisoning of methanol oxidation, less positive starting oxidation potential and smaller current density of CO stripping, compared to Pt(110)−(1×2) surfaces for the methanol electrooxidation and CO stripping. This study establishes a direct link between surface reconstruction, hydroxyl adsorption energetics, and MOR selectivity, providing mechanistic guidelines for tailoring platinum electrocatalysts with improved activity and CO tolerance.