Prussian blue analogues-derived 2D NiCo@C bimetals grown on g-C3N4 as photocatalysts for hydrogen evolution

The development of highly active and stable cocatalysts using earth-abundant transition metals to replace noble metals is important for the application of photocatalytic hydrogen production technology. In this study, two-dimensional (2D) carbon-encapsulated NiCo bimetallic nanosheets (NiCo@C) was designed for the first time as a new co-catalyst to synergistically combine with graphitic carbon nitride (g-C3N4) and promote its hydrogen evolution. The NiCo@C cocatalysts were using an innovative molten salt method by using nickel hexacyanocobaltate Ni3[Co(CN)6]2 (Ni-Co PBA) nanocubes as precursor. The Ni-Co PBA nanocubes undergo dissolution growth and salt templating processes to form bimetallic 2D nanosheets during charring in molten salt media, and combine with 2D g-C3N4 to form NiCo@C/g-C3N4 photocatalyst. The optimized NiCo@C/g-C3N4 photocatalyst significantly improved the H2 evolution activity, and the H2 evolution rate reached 3791.07 μmol·g−1·h−1, which was 5 times higher than that of the particle CoNi/g-C3N4 (636.89 μmol·g−1·h−1). The H2 evolution activity was also comparable to that of the photocatalytic activity of 1.0% Pt/g-C3N4 system, indicating that the earth-abundant NiCo@C can replace noble metal as a cocatalyst to significantly enhance the photocatalytic performance of 2D photocatalysts. The conversion of three-dimensional Ni-Co PBA into carbon-coated 2D metal nanosheets by molten salt-assisted pyrolysis provides a feasible approach to explore the synthesis and design of efficient and robust non-precious metal catalysts.