Modulation of sulfur vacancies at ZnIn2S4-δ/g-C3N4 heterojunction interface for successive C-H secession in photocatalytic gaseous formaldehyde complete oxidation

Abstract

Inspired by formaldehyde (HCHO) complete oxidation in atmospheric environments involving hydroxyl radicals (•OH) engaged in the breakage of the carbon-hydrogen (C-H) bond, Sv-ZnIn2S4-δ/g-C3N4 (Sv-ZIS/CN) composite decorated with sulfur vacancies (S-vacancies, Sv) 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 Sv-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.