SnS 2 Nanosheets/H-TiO 2 Nanotube Arrays as a Type II Heterojunctioned Photoanode for Photoelectrochemical Water Splitting.

Improving the separation efficiency of photogenerated electron-hole pairs and the conductivity of electrons to photoanode substrates are critical to achieve high-performance photoelectrochemical (PEC) water splitting. Here, a SnS2 /H-TiO2 /Ti heterojunction photoanode was fabricated with SnS2 nanosheets vertically grown on hydrogen-treated TiO2 (H-TiO2 ) nanotube arrays on a Ti substrate. It showed a significantly enhanced photocurrent of 4.0 mA cm-2 at 1.4 V (vs. reversible hydrogen electrode) under AM 1.5 G illumination, 70 times higher than that of SnS2 /TiO2 /Ti. Kelvin probe force microscopy measurements indicated that photogenerated electrons could be easily transported through the SnS2 /H-TiO2 interface but not through the SnS2 /TiO2 interface. Through hydrogen treatment, defects were created in H-TiO2 nanotubes to convert type I junctions to type II with SnS2 nanosheets. As a result, a high efficiency of electron-hole separation at the SnS2 /H-TiO2 interface and a high electron conductivity in H-TiO2 nanotubes were achieved and improved PEC performance. These findings show an effective route towards high-performance photoelectrodes for water splitting.