A Bi–Cu bimetallene array/carbonic anhydrase biohybrid for efficient and selective CO2 electroreduction at low concentration†

The dramatic increase in CO₂ emission has caused extreme weather events in recent years. Electrocatalytic CO₂ reduction reaction (CO₂RR) to useful fuels is an effective way of solving CO₂ emission. However, serious hydrogen reaction evolution interference and low Faraday efficiency restrict its large-scale application, especially at low CO₂ concentrations. This study presents a novel biohybrid comprising Bi–Cu bimetallenes (Bi–Cu BMLs) and carbonic anhydrase (CA) for efficient and selective electroreduction of CO₂ to formic acid at low CO₂ concentration. Ultra-thin Bi–Cu BMLs were synthesized via a facile galvanic replacement reaction, providing abundant sites for CA immobilization. The incorporation of Bi effectively suppresses the hydrogen evolution reaction and enhances the selectivity of the formic acid product, while the immobilized CA significantly increases the local CO₂ concentration at the electrode surface due to its exceptional CO₂ hydration activity and rapidly reversible equilibrium. As a result, the CA/Bi–Cu BML biohybrid system demonstrates remarkable performance, achieving 100% selectivity and 88.57% faradaic efficiency for formic acid production. Notably, the system maintains a high faradaic efficiency of 77.58% even at 5% CO₂ concentration. Furthermore, the biohybrid catalyst exhibits excellent stability and reusability, underscoring its potential for practical applications in dilute CO₂ streams.