In situ engineered CeOS/CeO nanofibrous heterojunctions for photocatalytic HO synthesis via S-scheme charge separation.

Photocatalytic HO 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 HO synthesis. However, designing S-scheme heterojunction photocatalysts with band alignment and close contact remains challenging. Here we report CeOS/CeO 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 CeOS to donate electrons to CeO 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 CeOS/CeO interfaces. The CeOS as the reduction photocatalyst exhibits significant O adsorption and activation along with a low energy barrier for the HO production. The optimal CeOS/CeO nanofibers heterojunction demonstrate enhanced photocatalytic HO production of 2.91 mmol gh, 58 times higher than that of pristine CeO nanofibers. This investigation provides valuable insights for the rational design and preparation of intimate contact nanofibrous heterojunctions with efficient solar HO synthesis.