Crystalline/amorphous Bi-BiNiO_x electrocatalyst enables efficient concurrent formate production from CO₂ and methanol

Electrochemical CO₂ reduction reaction (CO₂RR) to formate presents a technoeconomic route for CO₂ utilization under mild conditions, yet practical implementation is constrained by the high energy consumption (> 90% of total input) of the anodic oxygen evolution reaction (OER). Replacement of OER by partial methanol oxidation reaction (MOR) could lead to simultaneous formate production at both electrodes and remarkably reduce the overall energy consumption. Herein, we designed a two-electrode system featuring a nickel foam-supported crystalline/amorphous bismuth-bismuth nickel oxide composite cathode (Bi-BiNiO_x/NF) and a β-Ni(OH)₂ anode, achieving excellent formate production behavior. The crystalline/amorphous Bi-BiNiO_x/NF cathode delivers exceptional CO₂RR performance, achieving 98.9% formate Faradaic efficiency (FE_formate) at −0.90 V vs. reversible hydrogen electrode (RHE) and maintaining > 90.7% FE_formate over 72 h continuous operation—attributed to its Bi-Ni bimetallic synergy and crystalline/amorphous heterostructure that enhance active site exposure and reaction kinetics. The integrated CO₂RR||MOR system operates stably for 90 h at 2.2 V and 10 mA·cm⁻², sustaining > 90% FE_formate at both electrodes with a cell voltage (1.760 V) significantly lower than conventional CO₂RR||OER systems (1.953 V). This work demonstrates efficient concurrent formate electrosynthesis and establishes an energy-efficient paradigm for electrocatalytic CO₂ valorization through synergistic catalyst design and reaction pathway integration.