Femtosecond time-resolved spectroscopic observation of long-lived charge separation in bimetallic sulfide/g-C3N4 for boosting photocatalytic H2 evolution

Abstract

Copper-nickel sulfides could effectively suppress deep trapping states of active charge in carbon nitride. It also improves the efficiency of the shallow trapped electron transfer through CS bond for enhancing visible-light-driven photocatalytic hydrogen production with rates up to 752.8 μmol h−1 g−1, that is 470 times higher than that of pristine g-C3N4 (1.6 μmol h−1 g−1) so far. The kinetic coupling of electron transfer and long-lived charge separation (∼ 4896 ps) are systematically investigated by femtosecond time-resolved absorption spectroscopy (fs-TA). The TA signal of the composite is quenched by hole sacrificial agent, assigning to the effective hole extraction for high photocatalytic activity. Furthermore, a remarkable near-infrared-driven photocatalytic H2 evolution (0.32 μmol h−1 g−1, λ > 800 nm) was achieved due to the hole transfer from copper-nickel sulfide to the trap state of g-C3N4, indicating that the strong interaction between copper-nickel sulfide and g-C3N4 is favorable to charge transfer and long-lived charge separation states.