Concentrating and activating carbon dioxide over AuCu aerogel grain boundaries

Alloys are active in CO₂ electroreduction due to their unique electronic and geometric structures. Nevertheless, CO₂ reduction selectivity is still low due to the low concentration of CO₂ near the catalyst surface and the high energy barrier for CO₂ activation. This paper describes an AuCu nanochain aerogel (NC–AuCu) with abundant grain boundaries (GBs) that promote the accumulation and activation of CO₂ for further electrochemical reduction, employing in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy and density functional theory calculations. GBs can induce a strong local electric field to concentrate the electrolyte cations and thus accumulate CO₂ near the catalyst surface. NC–AuCu exhibits a superior Faradaic efficiency of close to 100% for CO₂ electroreduction to CO at an extremely low overpotential of 110 mV with a high CO partial current density of 28.6 mA cm⁻² in a flow cell. Coupling with a Si solar cell to convert solar energy to CO, a very high conversion efficiency of ∼13.0% is achieved. It potentially provides broad interest for further academic research and industry applications.