• • BSCN homojunction achieves a hydrogen evolution rate of 14.409 mmol g−1 h−1, which is 75-fold and 3.4-fold higher than pristine BCN and SCN, respectively, demonstrating a significant performance leap for practical solar fuel generation.
• • DFT calculations reveal a near-thermoneutral ΔGH* of 0.12 eV at S-doped sites, indicating optimized HER kinetics that reduce overpotential losses and enhance catalytic efficiency.
• • The interwoven porous nanotube/nanosheet architecture provides a large specific surface area and abundant exposed active sites, improving reactant accessibility and charge transfer kinetics.
• • In situ XPS and DFT confirm an S-scheme charge transfer mechanism at the BCN/SCN interface, which effectively suppresses charge recombination and prolongs carrier lifetime, critical for high quantum efficiency.