Atomic Layer Deposition of MoS<sub>2</sub> Decorated TiO<sub>2</sub> Nanotubes for Photoelectrochemical Water Splitting
Chengxu Shen, Ewa Wierzbicka, Thorsten Schultz, Rongbin Wang, Norbert Koch, Nicola Pinna
Abstract
Abstract A thermal atomic layer deposition (ALD) process to fabricate MoS 2 thin films is successfully demonstrated by using cycloheptatriene molybdenum tricarbonyl (C 7 H 8 Mo(CO) 3 ) and H 2 S as precursors at an ALD temperature below 300 °C. The process is systematically investigated, showing a typical self‐limiting characteristic within an ALD temperature window of 225–285 °C and a high growth‐per‐cycle of 0.11 nm. The as‐deposited films are amorphous while they can be crystallized in situ by sulfurization with H 2 S at a low temperature of 300 °C. A prototypical application of the developed ALD process is demonstrated by constructing a MoS 2 /TiO 2 heterostructure through depositing MoS 2 onto anodized TiO 2 nanotubes for photoelectrochemical water splitting. The MoS 2 /TiO 2 heterostructures exhibit approximately three times superior photoelectrochemical performance than the pristine TiO 2 nanotubes. This is attributed to an enhanced visible light‐harvesting ability of MoS 2 and an improved separation of the photo‐generated charge carriers at the heterostructure interface, which is affirmed by a staggering gap (type II) between MoS 2 and TiO 2 as probed by ultraviolet photoelectron spectroscopy.