Ultra-small molybdenum sulfide nanodot-coupled graphitic carbon nitride nanosheets: Trifunctional ammonium tetrathiomolybdate-assisted synthesis and high photocatalytic hydrogen evolution.

The preparation of nanoscale molybdenum sulfide (MoS)-modified graphitic carbon nitride (g-CN) nanosheets usually contains complex and multiple-step operations, including the separate synthesis of nanoscale MoS and g-CN nanosheet, and their subsequent composite process. To effectively overcome the above drawbacks, herein, a facile one-step trifunctional ammonium tetrathiomolybdate ((NH)MoS)-assisted approach has been designed to produce ultra-small MoS nanodot-coupled g-CN nanosheet photocatalyst, including the first addition of ammonium chloride (NHCl) and (NH)MoS into melamine precursors and their following one-step calcination. During high-temperature calcination, except for the promoting generation of the g-CN nanosheets by produced ammonia (NH) and hydrogen sulfide (HS) gases, the above (NH)MoS decomposition not only can efficiently clip the s-heptazine framework to produce more terminal amino groups and cyano groups, but also can produce ultra-small MoS nanodots on the resultant g-CN nanosheet surface, resulting in the final production of ultra-small MoS nanodot-coupled g-CN nanosheets. The resultant MoS nanodot-coupled g-CN nanosheets evidently exhibit increased photocatalytic hydrogen (H)-generation rate, about 8-fold increase to the traditional MoS-modified g-CN photocatalyst. The increased H-generation rate can be mainly attributed to the synergism of MoS nanodots and cyano group on the g-CN nanosheet surface. The current facile technology could open the sights for the preparation of other high-efficiency photocatalysts.