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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/MoS2core/sheath heterojunction nanostructures by employing atomic layer deposition (ALD) techniques. ALD-grown MoS2sheath layers with different thicknesses were realized on single-crystalline CdS nanorod (NR) arrays on transparent conducting oxide substrates. We further monitored the resulting solar H2evolution performance with our heterojunction photoanodes. The results showed that the junction thickness of MoS2plays 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 MoS2with ideal semiconducting absorbers.

We describe the direct preparation of crystalline Ni3S2thin films via atomic layer deposition (ALD) techniques at temperatures as low as 250 °C without postthermal treatments. A new ALD chemistry is proposed using bis(1-dimethylamino-2-methyl-2-butoxy) nickel(II) [Ni(dmamb)2] and H2S as precursors. Homogeneous and conformal depositions of Ni3S2films were achieved on 4 in. wafers (both metal and oxide substrates, including Au and SiO2). The resulting crystalline Ni3S2layers exhibited highly efficient and stable performance as electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline solutions, with a low overpotential of 300 mV and a high turnover frequency for HER and an overpotential of 400 mV for OER (at a current density of 10 mA/cm2). Using our Ni3S2films as both the cathode and the anode, two-electrode full-cell electrolyzers were constructed, which showed stable operation for 100 h at a current density of 10 mA/cm2. The proposed ALD electrocatalysts on planar surfaces exhibited the best performance among Ni3S2materials for overall water splitting recorded to date.