Unraveling the Interfacial Charge Migration Pathway at the Atomic Level in a Highly Efficient Z-Scheme Photocatalyst

A highly efficient Z-scheme photocatalytic system constructed with 1D CdS and 2D CoS₂ exhibited high photocatalytic hydrogen-evolution activity of 5.54 mmol h⁻¹ g⁻¹ with an apparent quantum efficiency of 10.2 % at 420 nm. More importantly, its interfacial charge migration pathway was unraveled: The electrons are efficiently transferred from CdS to CoS₂ through a transition atomic layer connected by Co–S_5.8 coordination, thus resulting in more photogenerated carriers participating in surface reactions. Furthermore, the charge-trapping and charge-transfer processes were investigated by transient absorption spectroscopy, which gave an estimated charge-separation yield of approximately 91.5 % and a charge-separated-state lifetime of approximately (5.2±0.5) ns in CdS/CoS₂. This study elucidates the key role of interfacial atomic layers in heterojunctions and will facilitate the development of more efficient Z-scheme photocatalytic systems.