Orchestrating Band Structures via Synergistic B and S Doping to Construct S-scheme g-C3N4 Homojunctions for Boosted Photocatalytic H2 Production
A dual-doping strategy incorporating boron (B) and sulfur (S) into graphitic carbon nitride (g-C3N4) was employed to engineer band structures and construct an S-scheme homojunction (BSCN) for enhanced photocatalytic hydrogen (H2) evolution. The BSCN catalyst exhibited an interwoven architecture of porous nanotubes and nanosheets, providing a large specific surface area and abundant active sites. In situ X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed an S-scheme charge transfer mechanism at the BCN/SCN interface, driven by a built-in electric field that facilitates efficient spatial separation of photogenerated charge carriers. Photoelectrochemical measurements confirmed improved light harvesting and charge separation. DFT simulations indicated near-thermoneutral hydrogen adsorption free energy (ΔGH* = 0.12 eV) at S-doped sites, favorable for hydrogen evolution reaction (HER) kinetics. The optimized BSCN achieved an exceptional H2 evolution rate of 14.409 mmol g−1 h−1, approximately 75-fold and 3.4-fold higher than pristine BCN and SCN, respectively. This work establishes a rational doping-mediated approach for designing high-efficiency g-C3N4 homojunctions and provides mechanistic insights into S-scheme charge transfer for solar-driven H2 production.