Defect-engineered carbon-confined silver for enhanced CO2 electrocatalytic reduction to CO in acidic media

Electrocatalytic CO2 reduction (CO2RR) to carbon monoxide (CO) holds great promise for carbon capture and utilization. Despite the proposal of electrocatalytic CO2RR in acidic media for high-efficiency CO2 conversion, the challenges of low CO selectivity caused by the highly competitive hydrogen evolution reaction and catalyst corrosion have not been adequately addressed. Here, we present a strategy that restricts proton migration and stabilizes key intermediates over a defective carbon layers confined Ag catalyst (Ag@C-d) to enhance the catalytic selectivity and stability for CO2RR in acidic media. Density functional theory simulations first discovered that electron polarization from Ag to vacancy-defective carbon creates the desired electric field at the interface between Ag and defective carbon layers, enabling efficient acidic CO2RR to CO. We synthesized Ag@C-d catalyst and that exhibits exceptional CO Faraday efficiency (FE, >98 %) and activity across a wide range of current densities (50–500 mA cm−2) in an acidic flow cell. At a current density of 500 mA cm−2, the single-pass conversion efficiency of CO2RR to CO can reached 71.5 %, surpassing that of alkaline systems. An excellent operational stability, operating continuously for over 100 h at industrial-scale current density, was also achieved. In a membrane electrode assembly electrolyzer incorporating the Ag@C-d catalyst at the cathode, a 91.6 % CO FE at 200 mA cm−2 can be achieved, accompanied by an energy conversion efficiency of nearly 40 %. These findings highlight the promising performance and potential applications of the developed catalyst for acidic CO2RR.