Targeted Electron-Hole Separation to Decoupled Redox-Active Sites Over a PEA2PbBr4/CeO2 P-N Heterojunction for Enhanced Photocatalytic Oxidation

Abstract

Photocatalytic selective oxidation of C(sp³)─H bonds into valuable carbonyl compounds offers a promising approach to advance green organic synthesis and contribute to a more sustainable chemical industry. However, significant challenges remain due to the low efficiency of photocatalysts, primarily caused by insufficient charge separation and the limited ability of intermixed surface redox-active sites to precisely capture photoinduced charge carriers. Here, a PEA₂PbBr₄/CeO₂ (PPB/CeO₂) p-n heterojunction is designed and fabricated. Experimental characterizations and theoretical calculations reveal that a strong internal electric field (IEF) is formed at the interface within the p-n heterojunction, which drives targeted accumulation of holes on PPB and electrons on CeO₂. Importantly, CeO₂ displays superior oxygen affinity facilitating O₂ reduction, while PPB validates stronger adsorption and activation capability to toluene molecule promoting C─H bond dissociation. In this context, the photoinduced electrons and holes are directionally separated and transported to the decoupled reduction and oxidation sites in the PPB/CeO₂, thereby significantly accelerating the aerobic oxidation of C(sp³)─H bonds. Toward photocatalytic oxidation of model substrate toluene, the optimized PPB/CeO₂-5% composite exhibits a toluene conversion rate of 10 050 µmol g⁻¹ h⁻¹, which is nine times enhanced in comparison with blank PPB (1160 µmol g⁻¹ h⁻¹).