Thermally-driven interface engineering of PMo ₁₂ /BiOBr heterojunctions for enhanced artificial photosynthesis of CO ₂ in water vapor

In this study, a heterojunction material composed of Keggin-type H₃PMo₁₂O₄₀ and BiOBr (PM/BOB) was synthesized by a hydrothermal-calcination method, and its photocatalytic CO₂ reduction performance and mechanism were investigated. Structural characterization through XRD, SEM, XPS, and UV-vis DRS revealed that calcination at 200 °C facilitated tight interfacial bonding between PM and BiOBr. The BiOBr sheets fragmented into nano-sized particles that uniformly integrated with PM, while partial reduction of PM generated active species containing mixed Mo⁵⁺/Mo⁶⁺ valence states. Under optimal conditions, the <i>t</i> ₂₀₀-PM/BOB_0.5 composite demonstrated exceptional CO₂ reduction performance without sacrificial agents, achieving a CO production rate of 18.82 μmol g^-1 h^-1, representing 10.06-fold and 7.13-fold enhancements over pristine BiOBr and PM, respectively. Mechanistic studies unveiled a Z-scheme electron transfer pathway where the reduced-state intervalence charge transfer (IVCT) excited species in PM act as electron mediators to drive CO₂ reduction, while the BiOBr valence band holes participate in water oxidation, achieving spatial separation of redox sites. This work provides a novel strategy for designing efficient Keggin-type molybdenum-based photocatalysts and advances the development of solar-driven CO₂ utilization technologies.