Correlation between the work function of Au–Ag nanoalloys and their electrocatalytic activity in carbon dioxide reduction

Highlights: • Electrocatalytic reduction of CO₂ was performed on Au-Ag nanoalloys with well-defined composition. • The CO Faradaic efficiency was tuned by controlling the Au:Ag ratio in the alloy. • The Fermi level was shifted away from the vacuum level with increasing Au content. • Changes in the catalytic activity and selectivity correlated with the electronic properties. -- Abstract: The electrocatalytic reduction of carbon dioxide (CO₂) on Au–Ag bimetallic alloy nanoparticles was scrutinized. This system provides a good model to investigate the correlation between the electrocatalytic activity and the composition of the nanoparticles. The CO Faradaic efficiency (and thus the forming CO:H₂ ratio) was changed linearly by controlling the Au:Ag ratio in the alloy. This trend was attributed to the changes in the electronic properties, as there was a monotonous shift in the Fermi level away from the vacuum level with increasing Au content. This shift correspondingly reduces the binding energy of the intermediates (*COOH and *CO), resulting in the gradually enhanced CO₂-reduction activity. Finally, comparison of the catalytic activity of Ag@Au core–shell particles to that of pure Ag (which bears similar electronic properties), and to Au–Ag alloy nanoparticles (with similar bulk composition), emphasized the importance of both geometric and electronic effects on the CO₂ reduction activity.