Rationally designing advanced electrocatalysts and innovative energy-efficient electrolysis systems for converting carbon dioxide (CO₂) into value-added chemicals or fuels is of significance yet challenging. As for the electrochemical CO₂ reduction reaction (CO₂RR), the electrocatalytic efficiency is largely limited by the CO₂ adsorption and activation capability of active sites. Herein, B-doped Bi nanosheet arrays grown on Cu foam are synthesized by a galvanic replacement combined with in situ doping strategy. It was demonstrated that the B dopant could serve as Lewis acid sites for promoting the adsorption of CO₂, and more importantly, regulate the electronic structure and crystallinity of Bi nanosheet arrays, and create abundant amorphous/crystalline two-phase interfaces, which boost the CO₂RR activity. Moreover, coupling the CO₂RR with the thermodynamically more favorable methanol oxidation reaction (replacing the kinetically sluggish oxygen evolution reaction) within a pH-asymmetric electrolysis system could realize highly efficient pair-electrosynthesis of formate with a much-reduced energy consumption compared with a conventional electrochemical CO₂RR system.