The methanol electrooxidation activity and the CO-resilient surface of a LaxFe1−y−zCuyPdzO3 perovskite

Abstract

The use of direct methanol fuel cells (DMFCs) is still hindered by the sluggish kinetics of the methanol oxidation reaction and the electrocatalyst surface poisoning by the adsorbed CO. In this work, we performed methanol electrooxidation using a LaFePdCuO perovskite oxide, which exhibited an excellent mass activity of 1041 mA mg⁻¹. In addition to its superb electrocatalytic activity, this perovskite is remarkable because of the absence of CO poisoning, as observed in cyclic voltammetry and operando Raman spectroelectrochemistry measurements. These experimental observations were explained using density functional theory, which predicted an optimal balance between the adsorption energies of the CO intermediate and adsorbed OH, supporting the observed remarkable mass activity of this material. Regarding the mechanistic understanding of the reaction, this work proposes a general approach to interpret the Tafel slopes observed for methanol electrocatalysts. In general, Tafel slopes are reported extensively but without a proper interpretation linking the experimental observations and the underlying mechanism. We are thus offering a new tool for the identification of the rate-determining step during methanol electrooxidation. The validity of this approach was elegantly supplemented by DFT calculations, thus permitting us to foresee a paradigm shift in the analysis of this multistep electrode processes.