Electrochemical CO₂ reduction on Au surfaces: mechanistic aspects regarding the formation of major and minor products

In the future, industrial CO₂ electroreduction using renewable energy sources could be a sustainable means to convert CO₂ and water into commodity chemicals at room temperature and atmospheric pressure. This study focuses on the electrocatalytic reduction of CO₂ on polycrystalline Au surfaces, which have high activity and selectivity for CO evolution. We explore the catalytic behavior of polycrystalline Au surfaces by coupling potentiostatic CO₂ electrolysis experiments in an aqueous bicarbonate solution with high sensitivity product detection methods. We observed the production of methanol, in addition to detecting the known products of CO₂ electroreduction on Au: CO, H₂ and formate. We suggest a mechanism that explains Au's evolution of methanol. Specifically, the Au surface does not favor C-O scission, and thus is more selective towards methanol than methane. These insights could aid in the design of electrocatalysts that are selective for CO₂ electroreduction to oxygenates over hydrocarbons.