Bicarbonate-to-CO electroreduction over NiCu catalysts with confined pore structures

Electrochemical bicarbonate reduction reaction offers a promising pathway of integrating carbon capture and conversion, which could bypass the energy-intensive upstream CO 2 regeneration and downstream CO 2 separation processes. Since the limited in-situ CO 2 ( i -CO 2 ) generation at the electrochemical interface, designing catalysts with highly exposed active sites and optimized structures is the key to achieve efficient bicarbonate reduction. In this work, we prepared a series of NiCu-based porous catalysts, using SiO 2 hard templates of different sizes to tune the pore structure. There exist an optimal mesopore size that could balance the mass transport, local i -CO 2 enrichment, and active-site distribution in bicarbonate electroreduction to CO. The optimal catalyst NiCu-TE achieved a bicarbonate-to-CO electrolysis at 100 mA cm −2 with 92.4% Faradaic efficiency (FE) and 41.3% energy efficiency (EE) in the membrane electrode assembly (MEA). It maintained a FE CO of 68.3% at a current density of −300 mA cm −2 . We found that pore architecture engineering, rather than pore size alone, is crucial in constructing efficient electrochemical microenvironments for bicarbonate electroreduction.