Lattice-dislocated bismuth nanowires formed by in-situ chemical etching on copper foam for enhanced electrocatalytic CO2 reduction

A simple three-step chemical method was used to construct twisted bismuth nanowires with abundant lattice dislocations on copper foam, significantly lowering the CO2 reduction potential, driving the rate-determining step backward in the reaction sequence, and achieving large current densities at low applied potentials. [Display omitted] •A new in-situ etching method has been proposed for the uniform loading of Bi on the metal Cu surface.•A three-step involving oxidation, reduction, and in-situ etching has been employed to fabricate lattice-dislocated BiNWs.•The Cu Foam@BiNWs achieved a 95 % FEFormate, with a JFormate of ∼12 mA cm−2, at a low potential of −0.78 V vs. RHE.•The RDS on Cu Foam@BiNWs is the proton transfer chemical step following the fast single electron transfer process. Electrochemical CO2 reduction reaction (CO2RR) to HCOOH is one of the most feasible and economical methods to achieve carbon neutrality. Bismuth (Bi), as a metal catalyst for CO2RR, is considered to have great potential for application and has been widely studied due to its high formate selectivity, low toxicity, cheapness, and abundance. Unfortunately, low current density and short electrode lifetime have hindered its progress towards practical applications. In this work, we present a method that enables the chemical etching of Bi on Cu, which is capable of spontaneously accomplishing the loading of Bi on Cu foam in the liquid phase at room temperature. Additionally, to provide more abundant catalytically active sites, twisted Bi nanowires (BiNWs) with lattice dislocations were successfully prepared on the surface of Cu foam using a three-step chemical method involving oxidation, reduction, and in-situ etching. The Cu Foam@BiNWs was found to be a highly active electrocatalyst for CO2 reduction to formate at a low applied potential, achieving a faradaic efficiency for formate (FEFormate) of 95 % and a formate partial current density of ∼ 12 mA cm−2 at −0.78 V vs. RHE (reversible hydrogen electrode). Even within such a wide potential window of −0.68 ∼ -1.08 V vs. RHE, the FEFormate is consistently above 90 %. Such exceptional CO2 reduction activity can be attributed to the distortions and lattice dislocations present in the surface BiNWs. Furthermore, the Cu Foam@BiNWs electrode demonstrated a total current density close to 100 mA cm−2 at −0.98 V in an alkaline flow cell, while maintaining excellent catalytic stability over a prolonged 30-hour period of high current density ele