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.