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.