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

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 211- and 1T- MoS2 show different reaction mechanism in photocatalytic H-2 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 H-2 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.