Boosting CO2 electroreduction to formate via in-situ formation of ultrathin Bi nanosheets decorated with monodispersed Pd nanoparticles

A novel electrocatalyst for CO2-to-formate conversion at low overpotentials with abundant bimetallic interfaces aroused from Pd nanoparticles anchoring in the underlying Bi nanosheet (Pd-BiNS) was developed. This unique synthesis procedure undergoes a continuous reconstruction of Pd-BiOINS to Pd-Bi2O2CO3NS to Pd-BiNS, which was confirmed by in situ Raman spectra combined with quasi-in-situ electron microscopy. The optimized Pd1-BiNS exhibits a high Faradaic efficiency of 95 % for formate at only − 0.4 V versus reversible hydrogen electrode over 30 h electrolysis, breaking the limitation that metallic Pd-site is easily poisoned by the generated CO at low overpotentials. The in situ infrared spectroscopy indicates that Pd-BiNS has much suppressed *CO binding and enhanced *OCHO adsorption to inhibit the competing hydrogen evolution reaction by repelling surface water molecules, moreover, a systematic CO2RR mechanism with HCO3− participating as pre-proton donor for formate generation is unveiled. This work provides new insight into the multisite synergistic regulation at the atomic scale.