In situ constructed oxygen-vacancy-rich MoO 3- x /porous g-C 3 N 4 heterojunction for synergistically enhanced photocatalytic H 2 evolution.

A simple method was developed for enhanced synergistic photocatalytic hydrogen evolution by in situ constructing of oxygen-vacancy-rich MoO 3- x /porous g-C 3 N 4 heterojunctions. Introduction of a MoO 3- x precursor (Mo(OH) 6 ) solution into g-C 3 N 4 nanosheets helped to form a porous structure, and nano-sized oxygen-vacancy-rich MoO 3- x in situ grew and formed a heterojunction with g-C 3 N 4 , favorable for charge separation and photocatalytic hydrogen evolution (HER). Optimizing the content of the MoO 3- x precursor in the composite leads to a maximum photocatalytic H 2 evolution rate of 4694.3 μmol g -1 h -1 , which is approximately 4 times higher of that of pure g-C 3 N 4 (1220.1 μmol g -1 h -1 ). The presence of oxygen vacancies (OVs) could give rise to electron-rich metal sites. High porosity induced more active sites on the pores' edges. Both synergistically enhanced the photocatalytic HER performance. Our study not only presented a facile method to form nano-sized heterojunctions, but also to introduce more active sites by high porosity and efficient charge separation from OVs.