Modulation of sulfur vacancies at ZnIn₂S_4-δ/g-C₃N₄ heterojunction interface for successive C-H secession in photocatalytic gaseous formaldehyde complete oxidation

Inspired by formaldehyde (HCHO) complete oxidation in atmospheric environments involving hydroxyl radicals (•OH) engaged in the breakage of the carbon-hydrogen (C-H) bond, S_v-ZnIn₂S_4-δ/g-C₃N₄ (S_v-ZIS/CN) composite decorated with sulfur vacancies (S-vacancies, S_v) was designed and fabricated for HCHO elimination at ambient environment. ZnIn₂S₄ (ZIS) in-situ grows on the g-C₃N₄ (CN) flats with an electrostatic attraction effect of cationic precursors, leading to the simultaneous construction of heterojunction interface and generation of S-vacancies. The internal electron field formed at the interface accelerate the photocarriers separation for the surface O₂ activation which has been profited form S-vacancies, thus promoting the generation of •OH radicals from •O₂^-→H₂O₂→•OH route. The photocatalytic HCHO oxidation in the S_v-ZIS/5CN sample is kinetically favorable in the presence of abundant •OH engaged in the successive C-H bond scission route dioxymethylene (DOM)→formates(HCOO-)→CO₂ revealed by in-situ DRIFTS, which avoids the generation of undesirable CO and accumulation of intermediates. Copyright © 2023 Elsevier B.V. All rights reserved.