General Strategy for Preparation of Porous Nickel Phosphide Nanosheets on Arbitrary Substrates toward Efficient Hydrogen Generation

Nickel phosphides have been widely explored for electrocatalytic hydrogen evolution reaction (HER) due to their high activity and durability. To date, however, it is still a big challenge to develop facile and scalable approaches to preparing nickel phosphide structures with high HER performance for practical applications. Here, a general strategy is demonstrated for facile preparation of porous nickel phosphide nanosheets on arbitrary substrates by electroless Ni plating on the substrate followed by a convenient and stable phosphidation reaction. Typical porous nickel phosphide nanosheets (Ni₅P₄/NiP₂/Ni₂P) supported on carbon cloth show excellent electrocatalytic HER activities in acidic electrolyte with very small overpotentials of 63 mV and 120 mV to attain current densities of 10 mA cm^-2 and 100 mA cm^-2, respectively, and a very low Tafel slope of 47.3 mV dec^-1, which are among the best results compared to other non-noble HER electrocatalysts. Furthermore, the electrode exhibits superior flexibility and outstanding durability with negligible degradation under either an accelerated degradation test for 5000 cyclic voltammetry cycles or a durability test under a constant current density of 10 mA cm^-2 for 168 h. The excellent HER performance is contributed by the high specific surface area of porous nanosheets and the synergistic effect among Ni₅P₄, NiP₂, and Ni₂P phases. Besides, the porous nickel phosphide nanosheets grown on a large-area carbon cloth film via the same method show nearly the same high HER activities, suggesting a high potential for practical application. In addition, this strategy is employed to prepare porous nickel phosphide nanostructures on arbitrary substrates, even elaborate leaf vein and silkworm cocoon, with remarkable HER activities. The preparation method reported here is practical and scalable and can be extended to produce transition-metal-based structures on appropriate substrates for various applications.