Electrocatalytic CO2 Reduction to Methanol on Pt(111) Modified with a Pd Monolayer

Electrochemical carbon dioxide (CO2) conversion to value-added, highly reduced chemicals such as methanol (CH3OH) is a promising possibility for producing renewable fuel and simultaneous CO2 recycling. However, this process remains a challenge, with only a few selective electrocatalysts known. Here, we present a study of a palladium monolayer on a platinum (111) single crystal (PdML/Pt(111)) as an electrocatalyst for CO2 conversion to CH3OH. A custom-made setup was employed in order to detect and quantify gaseous and liquid CO2 reduction products in sufficient concentrations despite the limitations of working with a single-crystalline electrode. Under ambient reaction conditions, a Faradaic efficiency (FE) of 1.5% at -0.9 V vs reversible hydrogen electrode (RHE) was obtained while using CO2 as the reactant. Other reaction intermediates, carbon monoxide (CO) and formaldehyde (HCHO) were subsequently used as reactants, leading to FEs of 1.8 and 2.5%, respectively, whereas formic acid is not reduced. The corresponding mechanism concluded from our work is compared to the literature. The electrocatalyst introduced here, with a highly well-defined structure for CO2 conversion to CH3OH, opens up possibilities for further catalytic explorations.