In situ construction of Bi5O7I/Bi4Ti3O12 heterostructure composites with plentiful phase interfaces for the boosted selective oxidation of benzylic alcohols under visible light

Abstract

Novel flower-like Bi₅O₇I/Bi₄Ti₃O₁₂ (BOI/BTO) photocatalysts were successfully designed and fabricated by an in situ growth method. The BOI and BTO in BOI/BTO composites have abundant interface contact and constructed a Z-scheme heterojunction structure. Therefore, these composites exhibited excellent performance for the selective oxidation of benzylic alcohols under visible light. It was attributed to the stronger absorption capacity of visible light and the high separation efficiency of photogenerated carriers via the Z-scheme transfer mechanism; especially, the sample BOI/BTO-1.5 achieved 92.4% selectivity for the oxidation of 4-methylbenzyl alcohol (4-MBA) to 4-methyl-benzaldehyde (4-MBAD) in the presence of H₂O₂, which also exhibited good stability, reusability and substrate adaptability. As evidenced by the activity experiments, trapping experiments and ESR analysis, the ˙O₂⁻ radicals and HOO˙ radicals were supposed to be the main active species directly involved in the photocatalytic oxidation process. Based on the optical and electrical analysis, a Z-scheme transfer facilitated mechanism of photocatalytic selective oxidation of benzylic alcohols was speculated.