Core-shell nanoporous AuCu3@Au monolithic electrode for efficient electrochemical CO2 reduction
Selective conversion of carbon dioxide (CO2) to a reusable form of carbon via electrochemical reduction has attracted intensive interests for the storage of renewable energy. The achievement of efficient bulk monolithic electrocatalysts still remains a challenge. Herein, a facile oxidative etching of Au20Cu80 alloy has been developed to the synthesis of monolithic nanoporous core-shell structured AuCu3@Au electrode, which shows Faradaic efficiency (FE) of 97.27% with a partial current density of 5.3mA cm-2 at -0.6 V vs RHE for CO production. The FE value is about 1.45 times higher than that over Au nanocatalyst. Unlike single nanoporous Au, the AuCu3@Au maintains excellent performance at a broad potential window. Furthermore, a 23 cm long nanoporous AuCu3@Au bulk electrode with good ductility has been prepared, over which the active current reaches up to 37.2 mA with a current density of 10.78 mA cm-2 at -0.7 V vs. RHE, pushing the reduction of CO2 to industrialization. Unsaturated coordination environment with number of 8.2 over the shell gold and curved interface determines its high electrocatalytic performance. Density functional theory calculation suggests that the double-dentate adsorption structure in AuCu3@Au catalyst effectively improves the stability of the *COOH intermediate. The density of states indicates that the introduction of Cu cause the d-band-centre of the AuCu3@Au to move toward the Fermi level, directly bonding with *COOH. Therefore, the adsorption of *COOH on the surface of the AuCu3@Au catalyst is strengthened, facilitating the formation of CO. This work opens an avenue to achieve self-supported porous electrode for the various useful catalytic conversions.