Atomic-scale interface engineering in Bi/Bi₂O₃ heterojunctions for selective CO₂ photoreduction to methanol

The strategic engineering of an Ohmic junction at the Bi/Bi₂O₃ (BBO) interface is demonstrated to synergistically enhance photocatalytic CO₂-to-methanol conversion through precisely modulated charge behavior and interfacial energy alignment. This metallic Bi-semiconductor Bi₂O₃ Ohmic junction with local surface plasmon resonance effect induces a robust built-in electric field that promotes the unidirectional electron transfer from Bi₂O₃ to Bi while suppressing charge recombination. Theoretical calculations and experimental evidence reveal that the interfacial Bi sites within the Ohmic junction predominantly facilitate CO₂ adsorption and activation to form *COOH, whereas ensuing protonation steps are favored on metallic Bi sites on BBO Ohmic junction. Furthermore, the Ohmic junction enhances interfacial electron density and strengthens orbital hybridization between Bi 6p and O 2p orbitals, thereby reducing the activation energy of the rate-limiting *CO₂ → *COOH step by 0.6 eV, enabling a CH₃OH production rate of 610 μmol g^-1 under light irradiation. The work deciphers the dual role of Ohmic junctions in simultaneously resolving bulk charge transport limitations and tailoring surface catalytic landscapes, establishing a universal paradigm for metal-semiconductor heterojunction photocatalyst design.