2H- and 1T- mixed phase few-layer MoS2 as a superior to Pt co-catalyst coated on TiO2 nanorod arrays for photocatalytic hydrogen evolution

Abstract

Recently, MoS2 as an efficient co-catalyst has attracted much attention for photocatalytic water splitting. MoS2 has two polymorphs: semiconducting phase (2H) and metallic phase (1T). The 2H- and 1T- MoS2 show different reaction mechanism in photocatalytic H2 evolution. However, so far, very few experiments have clearly evidenced the electron transfer process between TiO2 and mixed phase MoS2. This study for the first time has reported a simple hydrothermal synthesis method to prepare mixed phase few-layer MoS2 nanosheets coated on TiO2 nanorod arrays (MoS2@TiO2) with a conductive fluorine-doped tin oxide (FTO) as a substrate. The structure of mixed phase MoS2 was characterized carefully. The designed MoS2@TiO2 exhibits two times higher activity than Pt@TiO2 for photocatalytic H2 evolution. The reliable conclusion that the photo-generated electrons from TiO2 to MoS2 nanosheets has clearly been evidenced by photoelectrochemical analyses and in-situ KPFM experiments, and the mixed phase MoS2 here is a co-catalyst such like Pt rather than as a semiconductor. This study not only presents a series of solid experimental evidences to verify the electrons transfer process and photocatalytic mechanism, but also provides a new method in substituting MoS2 for noble metal Pt as co-catalyst in high-efficiency photocatalytic water splitting into hydrogen.