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-C 3 N 5 /CdS) core–shell heterojunction is constructed to optimize photocatalytic performance. The optimal hydrogen production rate of g-C 3 N 5 /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-C 3 N 5 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 (τ 1 = 52.3 ps) and long-lived excited states (τ 3 = 1109.2 ps) in g-C 3 N 5 /CdS photocatalyst. Meanwhile, density functional theory calculation results comprehensively suggest the promoted charge separation in heterojunction. Cost-effective Z-scheme g-C 3 N 5 /CdS photocatalyst in this work shows a great potential for sustainable and high-efficiency solar-to-H 2 conversion.