In situ engineered Ce2O2S/CeO2 nanofibrous heterojunctions for photocatalytic H2O2 synthesis via S-scheme charge separation.

Photocatalytic H₂O₂ synthesis offers an efficient and sustainable means to convert solar energy into chemical energy, representing a forefront and focal point in photocatalysis. S-scheme heterojunctions demonstrate the capability to effectively separate photogenerated electrons and holes while possessing strong oxidation and reduction abilities, rendering them potential catalysts for photocatalytic H₂O₂ synthesis. However, designing S-scheme heterojunction photocatalysts with band alignment and close contact remains challenging. Here we report Ce₂O₂S/CeO₂ multiphase nanofibrous prepared via an in situ sulphuration/de-sulphuration strategy. This in situ process enables intimate contact between the two phases, thereby shortening the charge transfer distance and promoting charge separation. The interfacial electronic interaction and charge separation were investigated using in situ X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. The work function difference enables Ce₂O₂S to donate electrons to CeO₂ upon combination, resulting in the formation of an internal electric field (IEF) at interfaces. This IEF, along with bent energy bands, facilitates the separation and transfer of photogenerated charge carriers via an S-scheme pathway across the Ce₂O₂S/CeO₂ interfaces. The Ce₂O₂S as the reduction photocatalyst exhibits significant O₂ adsorption and activation along with a low energy barrier for the H₂O₂ production. The optimal Ce₂O₂S/CeO₂ nanofibers heterojunction demonstrate enhanced photocatalytic H₂O₂ production of 2.91 mmol g^-1h^-1, 58 times higher than that of pristine CeO₂ nanofibers. This investigation provides valuable insights for the rational design and preparation of intimate contact nanofibrous heterojunctions with efficient solar H₂O₂ synthesis.