Coverage-dependent formic acid oxidation reaction kinetics determined by oscillating potentials

Abstract Establishing correlations between catalytic activity and dynamic surface properties of real catalysts, such as adsorbate coverage, is not straight-forward but crucial for the understanding of catalytic phenomena. The formic acid oxidation reaction comprises the non-Faradaic dehydration to CO when no potential is applied to the catalyst surface and the subsequent Faradaic oxidative desorption to form CO2. Here, we report a methodology based on applying oscillating potentials to various electrocatalytically active metal surfaces during the formic acid oxidation reaction. Moderate frequency oscillations (0.1–10 Hz) allow us to control the coverage of intermediates on the surface, thus enabling the quantification of the transient effects (on the time scale of up to 10−4 s) of coverage on the reaction rate. We determined different coverage-dependences of turnover frequencies for Pt metal plate and various carbon-supported metal nanoparticle catalysts (Pt/C, Pd/C and Rh/C). This method therefore constitutes a valuable and simple tool for the elucidation of adsorbate coverages on metal surfaces and their resulting catalytic performance. We also demonstrate that dynamic catalytic processes can be analysed semi-quantitatively with this new approach, allowing the design of catalytic processes under optimized conditions.