Br-doped Cu nanoparticle formed by in situ restructuring for highly efficient electrochemical reduction of CO2 to formate

Electrochemical conversion of CO₂ into chemical feedstock, such as an energy-dense liquid product (formate), is desirable to address the excessive emission of greenhouse gases and store energy. Cu-based catalysts exhibit great advantages in electrochemical CO₂ reduction reaction (eCO₂RR) due to their low cost and high abundance, but suffer from low selectivity of formate. In this work, a facile one-pot approach is developed to synthesize CuBr nanoparticle (CuBr NP) that can conduct in situ dynamic restructuring during eCO₂RR to generate Br-doped Cu NP. The in situ-formed Br-doped Cu NP can afford up to 91.6% Faradaic efficiency (FE) for formate production with a partial current density of 15.1 mA·cm⁻² at −0.94 V vs. reversible hydrogen electrode (RHE) in an H-type cell. Moreover, Br-doped Cu NP can deliver excellent long-term stability for up to 25 h. The first-principles density functional theory (DFT) calculations show that the doped Br can regulate the electronic structure of Cu active sites to optimize the adsorption of the HCOO* intermediate, greatly hindering the formation of CO and H₂. This work provides a strategy for electronic modulation of metal active site and suggests new opportunities in high selectivity for electrocatalytic reduction of CO₂ to formate over Cu-based catalysts.