Electrochemical Reduction of Carbon Dioxide at Gold-Palladium Core–Shell Nanoparticles: Product Distribution versus Shell Thickness

The electrocatalytic reduction of CO₂ at carbon-supported Au-Pd core–shell nanoparticles is investigated systematically as a function of the Pd shell thickness. Liquid- and gas-phase products were determined by off-line ¹H NMR spectroscopy and on-line electrochemical mass spectrometry. Our results uncover the relationship between the nature of the products generated and the Pd shell thickness. CO and H₂ are the only products generated at 1 nm thick shells, whereas shells of 5 and 10 nm produced HCOO−, CH₄ and C₂H₆. The concentration of HCOO− detected in the electrolyte was dependent on the applied potential and reached a maximum Faradaic efficiency of 27 % at −0.5 V versus the reversible hydrogen electrode for 10 nm thick shells. We conclude that collisions between absorbed hydrogen at relaxed Pd lattices and strongly bound “CO-like” intermediates promote the complete hydrogenation to C1 and C2 alkanes without the generation of other products, such as alcohols and aldehydes.