Z-Scheme Strategy in Polymeric Graphitic C₃N₅/CdS Core–Shell Heterojunction Drives Long-Lived Carriers Separation for Robust Visible-Light Hydrogen Production

The intrinsic charge carriers’ recombination and excited states decay greatly suppress the active species survival and photo(electro)catalytic performance. Inspired by Z-scheme strategy, the polymeric nitrogen-rich carbon nitride/cadmium sulfide (g-C₃N₅/CdS) core–shell heterojunction is constructed to optimize photocatalytic performance. The optimal hydrogen production rate of g-C₃N₅/CdS heterojunction catalyst under visible light without adding extra cocatalyst is up to 7860 µmol h⁻¹ g⁻¹, which is 3 and 71 times higher than that of pure CdS and g-C₃N₅ photocatalysts, respectively. The femtosecond transient absorption spectroscopy is employed to observe the kinetic decay of carriers in the heterojunction, revealing the ultrafast charge trapping process (τ₁ = 52.3 ps) and long-lived excited states (τ₃ = 1109.2 ps) in g-C₃N₅/CdS photocatalyst. Meanwhile, density functional theory calculation results comprehensively suggest the promoted charge separation in heterojunction. Cost-effective Z-scheme g-C₃N₅/CdS photocatalyst in this work shows a great potential for sustainable and high-efficiency solar-to-H₂ conversion.