In situ construction of 3D low-coordinated bismuth nanosheets@Cu nanowire core-shell nanoarchitectures for superior CO₂ electroreduction activity

Electrocatalytic reduction of CO2 (CO2RR) to formic acid (HCOOH) with high selectivity (>90%) and large current density (>100 mA cm(-2)) is highly challenging due to CO2 mass-transfer limitations. Herein, we in situ constructed 3D bismuth nanosheets@Cu nanowire core-shell nano-architectures on Cu foam (Cu@Bi NWs/Cu) as efficient electro-catalysts for CO2RR into HCOOH. The Cu@Bi NWs/Cu electrode achieves a large current density of 155.8 mA cm(-2) with a HCOOH faradaic efficiency of 90.1% in a H-type cell. The superior activity is attributed to the large catalytic surface area related to the porous structure and high intrinsic activity induced by lattice defects on the preferential exposure of the Bi (110) facet. The atomic defects in the Bi (110) facet facilitate the entry of CO2 and realize four low-coordination atoms around the defected Bi atom, thereby generating more active sites and improving the catalytic performance. The presence of the Cu NW support significantly enhances the Bi reducibility of the Cu@Bi surface due to the partial electron transfer from Cu to Bi, thereby boosting the C-terminal hydrogenation of CO2. This work demonstrates an effective strategy to fabricate 3D porous core-shell nanoarchitectures consisting of a shell with numerous unsaturated sites on a highly-conductive core for efficient catalysis.