Fullerene–Graphene Acceptor Drives Ultrafast Carrier Dynamics for Sustainable CdS Photocatalytic Hydrogen Evolution

Abstract

Ultrafast excited-state decay and intrinsic charge carrier recombination restrain the photoactivity enhancement for solar-to-H₂ production. Here, a CdS-fullerene/graphene (CdS-F/G) photocatalyst is synthesized for enhancing visible-light-driven hydrogen generation from earth-abundant water. The CdS-F/G shows ultrafast interfacial electrons/holes transfer and holes self-trapping process in photocatalysis. The in-situ dynamic study from transient absorption spectroscopy reveals the sub-microsecond-lived excited states (≈172.6 ns), interfacial electron transfer (≈30.3 ps), and hole trapping (≈44.0 ps) in the CdS-F/G photocatalyst. The efficient active species transportation and prolonged lifetime significantly enhance the charge separation state survival, increasing the photoactivity and photostability. Consequently, visible-light activity enhancement (>400%) of H₂ evolution reaction (HER) is obtained at the CdS-F/G photocatalyst with high stability (>36 h). The 127.2 µmol h⁻¹ g⁻¹ performance corresponding to a quantum efficiency of 7.24% at 420 nm is not only higher than the case of pristine CdS (29.2 µmol h⁻¹ g⁻¹) but also much higher than that of CdS-Pt photocatalyst (73.8 µmol h⁻¹ g⁻¹). The cost-effective CdS-F/G photocatalyst exhibits a great potential for sustainable and high-efficiency photocatalytic water splitting into clean energy carriers. Moreover, the optimized electronic structure associated with interfacial electrons/holes transfer and holes self-trapping promotes overall water splitting for H₂ and O₂ generation.