Abstract: Photocatalytic hydrogen evolution from water splitting is an appealing method for producing clean chemical fuels. Cu₂O, with a suitable bandgap, holds promise as a semiconductor for this process. However, the strong photo-corrosion and rapid charge recombination of Cu₂O strongly limit its application in the photocatalytic fields. Herein, an S-scheme heterojunction photocatalyst composed of TiO₂ and Cu₂O was rationally designed to effectively avoid the photo-corrosion of Cu₂O. The introduction of an interfacial nitrogen-doped carbon (NC) layer switches the heterojunction interfacial charge transfer pathway from the p-n to S-scheme heterojunction, which avoids excessive accumulation of photogenerated holes on the surface of Cu₂O. Meanwhile, the hybrid structure shows a broad spectral response (300-800 nm) and efficient charge separation and transfer efficiency. Interestingly, the highest photocatalytic hydrogen evolution rate of TiO₂-NC-3%Cu₂O-3%Ni is 13521.9 μmol g^-1 h^-1, which is approximately 664.1 times higher than that of pure Cu₂O. In-situ X-ray photoelectron spectroscopy and Kelvin probe confirm the charge transfer mechanism of S-scheme heterojunction. The formation of S-scheme heterojunctions effectively accelerates the separation of photogenerated electron-hole pairs and enhances redox capacity, thereby improving the photocatalytic performance and stability of Cu₂O. This study provides valuable insights into the rational design of highly efficient Cu₂O-based heterojunction photocatalysts for hydrogen production.

Key words: Photocatalytic hydrogen evolution, Cu₂O, S-scheme heterojunction, Charge separation mechanism, Nitrogen doped carbon