Heterojunction Photoanode of Atomic-Layer-Deposited MoS₂ on Single-Crystalline CdS Nanorod Arrays

Cadmium sulfide (CdS) is a semiconducting absorber for photoelectrochemical (PEC) hydrogen production with suitable electronic band structures. However, it suffers from severe photocorrosion and rapid charge recombination during the desired PEC reactions. Herein, we describe the identification of the optimal junction thickness of CdS/MoS2 core/sheath heterojunction nanostructures by employing atomic layer deposition (ALD) techniques. ALD-grown MoS2 sheath layers with different thicknesses were realized on single-crystalline CdS nanorod (NR) arrays on transparent conducting oxide substrates. We further monitored the resulting solar H2 evolution performance with our heterojunction photoanodes. The results showed that the junction thickness of MoS2 plays a key role in the reduction of photocorrosion and the enhanced photocurrent density by optimizing the charge separation. A better saturation photocurrent (∼46%) was obtained with the 7 nm-thick MoS2@CdS NRs than that with the bare CdS NRs. Moreover, the external quantum efficiency was increased twofold over that of the pristine CdS NRs. The ALD-grown MoS2@CdS heterojunction structures provides an efficient and versatile platform for hydrogen production when combining ALD-grown MoS2 with ideal semiconducting absorbers.