The overall energy efficiency is critical for commercializing promising electrochemical technologies such as the CO₂ reduction reaction (CO₂RR). Despite the rapid development of advanced catalysts and reactors for CO₂RR, its commercial potential is still hindered by the sluggish oxygen evolution reaction (OER), which causes high cell voltages and low energy efficiencies. Herein, we have developed a NiOOH@Ni₃S₂ catalyst on the surface of nickel foam (NF) via an electrochemical surface reconstruction strategy. We observe that the oxidation of glycerol to formate is more thermodynamically favorable than the OER on the developed NiOOH@Ni₃S₂/NF catalysts. The Ni²⁺/Ni³⁺ redox couples within the NiOOH@Ni₃S₂ heterojunction enhance the charge transfer kinetics between the active sites and adsorbed reaction intermediates, facilitating the highly selective and active generation of formate from glycerol oxidation reaction (GOR), with a remarkable Faradaic efficiency (FE) of 94% achieved at 100 mA cm^-2. Comprehensive mechanistic studies identified that the reaction pathway towards formate generation starts from glyceraldehyde intermediates and the glycolate was considered as the key species. Moreover, benefited from the efficient conversion of CO₂ to formate on bismuth nanosheets, the GOR//CO₂RR paired electrolysis system realizes a remarkable overall FE of ca. 190% for formate co-production at 160 mA cm^-2 (cathodic FE: 91.25%; anodic FE: 98.70%). This proceeds at a cell voltage of ca. 2.32 V, which is ca. 0.85 V lower than that of OER-assisted CO₂RR system at the same current density. This work provides new insights for co-upgrading CO₂ and biomass to value-added chemicals.

CO₂ electroreduction has been regarded as an appealing strategy for renewable energy storage. Recently, bismuth (Bi) electrocatalysts have attracted much attention due to their excellent formate selectivity. However, many reported Bi electrocatalysts suffer from low current densities, which are insufficient for industrial applications. To reach the goal of high current CO₂ reduction to formate, we fabricate Bi nanosheets (NS) with high activity through edge/terrace control and defect engineering strategy. Bi NS with preferential exposure sites are obtained by topotactic transformation, and the processes are clearly monitored by in-situ Raman and ex-situ X-ray diffraction (XRD). Bi NS-1 with a high fraction of edge sites and defect sites exhibits excellent performance, and the current density is up to ca. 870 mA·cm⁻² in the flow cell, far above the industrially applicable level (100 mA·cm⁻²), with a formate Faradaic efficiency greater than 90%. In-situ Fourier transform infrared (FT-IR) spectra detect *OCHO, and theoretical calculations reveal that the formation energy of *OCHO on edges is lower than that on terraces, while the defects on edges further reduce the free energy changes (ΔG). The differential charge density spatial distributions reveal that the presence of defects on edges causes charge enrichment around the C–H bond, benefiting the stabilization of the *OCHO intermediate, thus remarkably lowering the ΔG.