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SignificanceBlack phosphorus (BP) nanosheet is a “hot” class of 2D material having wide applications in optoelectronics, catalysis, biomedicine, etc. However, facile synthesis of BP nanosheets is not achieved by far. Currently, BP nanosheets are mainly prepared via solution-based exfoliation of bulk crystals, a process that is complicated, time-consuming, and costly. Moreover, the as-prepared BP nanosheets are not stable. Here, we developed a facile bottom-up protocol for preparing BP nanosheets in solution at low temperature. Our synthetic procedure is conceptually simple and can be performed in common chemical laboratories. The estimated synthesis cost is less than 1 US dollar per gram. Our work, therefore, offers the community an unlimited access to such 2D material.

Solar-driven water splitting using powdered catalysts is considered as the most economical means for hydrogen generation. However, four-electron-driven oxidation half-reaction showing slow kinetics, accompanying with insufficient light absorption and rapid carrier combination in photocatalysts leads to low solar-to-hydrogen energy conversion efficiency. Here, we report amorphous cobalt phosphide (Co-P)-supported black phosphorus nanosheets employed as photocatalysts can simultaneously address these issues. The nanosheets exhibit robust hydrogen evolution from pure water (pH = 6.8) without bias and hole scavengers, achieving an apparent quantum efficiency of 42.55% at 430 nm and energy conversion efficiency of over 5.4% at 353 K. This photocatalytic activity is attributed to extremely efficient utilization of solar energy (~75% of solar energy) by black phosphorus nanosheets and high-carrier separation efficiency by amorphous Co-P. The hybrid material design realizes efficient solar-to-chemical energy conversion in suspension, demonstrating the potential of black phosphorus-based materials as catalysts for solar hydrogen production.

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