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

Electrochemical carbon dioxide (CO) conversion to value-added, highly reduced chemicals such as methanol (CHOH) is a promising possibility for producing renewable fuel and simultaneous CO 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 (Pd/Pt(111)) as an electrocatalyst for CO conversion to CHOH. A custom-made setup was employed in order to detect and quantify gaseous and liquid CO 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 CO 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 CO conversion to CHOH, opens up possibilities for further catalytic explorations.