Constructing the facet junction on solid solution BiOBr_1-xCl_x for efficient photocatalytic CO₂ reduction with H₂O

Photocatalytic conversion of CO₂ to renewable clean fuels was a promising way to alleviate the energy crisis and solve environmental issues. However, it remained significantly challenging for designing highly efficient photocatalysts. Herein, the solid solution BiOBr_1-xCl_x (0 ≤ x ≤ 1, BOBC-n, n represented the amount of molten salt) with (001)/(102) facet junction was constructed through a molten salt method. In situ photochemical probing demonstrated that distinct exposed facets allowed photogenerated holes and electrons to migrate to the dominantly exposed and co-exposed facets and thus exhibited different reactivity. Benefiting from facet junction, the optimized BOBC-0.5 exhibited the superior performance of photocatalytic CO₂ to CH₃OH (5.52 μmol·g⁻¹·h⁻¹) to that of BiOBr with (001)/(110) facet junction (1.78 μmol·g⁻¹·h⁻¹). The density functional theory (DFT) calculations further confirmed the separation path of photogenerated carriers between distinct facets, which realized the effective spatial separation of electrons and holes. Moreover, the (102) facet revealed superior adsorption energy of CO₂ molecules to that of (110) facet. This work highlighted a molten-salt strategy to build facet junction for boosting photocatalytic CO₂ performance.