Abstract: The rapid recombination of photogenerated electron-hole pairs persistently hinders the advancements of single-component photocatalysts in hydrogen production. To address this fundamental challenge, this work constructed a 1D/2D ZnO nanofiber/SnIn₄S₈ nanosheet S-scheme heterojunction via an electrospinning and solvothermal synthesis strategy. The resultant ZnO/SnIn₄S₈ heterojunction exhibits a well-coupled nanofiber structure with SnIn₄S₈ nanosheet loading on the surface. The optimized ZSIS-0.03 composite achieves a record hydrogen evolution rate of 1374.41 µmol g^-1 h^-1, surpassing pristine ZnO and SnIn₄S₈ by 2.89 and 8.69-fold, respectively. Mechanistic investigations combining femtosecond transient absorption (fs-TA), in-situ XPS, electron paramagnetic resonance (EPR) spectroscopy, and DFT calculations elucidate the S-scheme charge transfer dynamics: the photoinduced holes in SnIn₄S₈ recombine with electrons in ZnO at the heterointerface through a built-in electric field, while high-potential electrons in SnIn₄S₈ and holes in ZnO are preserved to participate in the interfacial redox reactions. Furthermore, theoretical simulations coupled with Crystal Orbital Hamilton Population (COHP) analysis revealed that Sn sites exhibit enhanced water adsorption energy (-0.55 eV) through optimal adsorptive Sn-O coordination bonds (-ICOHP = 0.31), significantly promoting electron transfer to the adsorbed H₂O. Consequently, the unique 1D/2D structure significantly enhances light harvesting, provides abundant active sites (surface area 41.22 m² g^-1), and establishes directional charge transport pathways. This work not only deciphers the atomic-level charge transfer mechanisms in S-scheme systems but also provides a universal strategy for designing high-efficiency heterojunction photocatalysts.

Key words: S-scheme heterojunction, 1D ZnO nanofibers, 2D SnIn₄S₈ nanosheets, Photocatalytic hydrogen evolution, Charge transfer mechanism