Delocalized Electron Accumulation at Nanorod Tips: Origin of Efficient H-2 Generation

Abstract

Photocatalytic hydrogen (H-2) evolution requires efficient electron transfer to catalytically active sites in competition with charge recombination. Thus, controlling charge-carrier dynamics in the photocatalytic H-2 evolution process is essential for optimized photocatalyst nanostructures. Here, the efficient delocalization of electrons is demonstrated in a heterostructure consisting of optimized MoS2 tips and CdS nanorods (M-t-CdS Nrs) synthesized by amine-assisted oriented attachment. The heterostructure achieves photocatalytic H-2 activity of 8.44 mmol h(-1) g(-1) with excellent long-term durability (>23 h) without additional passivation under simulated solar light (AM 1.5, 100 mW cm(-2)). This activity is nearly two orders of magnitude higher than that of pure CdS Nrs. The impressive photocatalytic H-2 activity of M-t-CdS Nrs reflects favorable charge-carrier dynamics, as determined by steady-state PL and time-correlated single photon counting correlation analysis at low temperature. The MoS2 cocatalysts precisely located at the end of the CdS Nrs exhibit ultrafast charge transfer and slow charge recombination via spatially localized deeper energy states, resulting in a highly efficient H-2 evolution reaction in lactic acid containing an electrolyte.