In situ hydrothermal growth of Ni-based hydrogen phosphate polyhedrons on Ni foam for efficient hydrogen evolution reaction

The highlights for the manuscript are as follows:. • A green in-situ growth strategy was used to prepare the self-supporting electrode. • Ni hydrogen phosphate electrode was synthesized controllably via a facile hydrothermal method. • Synergistic effect among Ni hydrogen phosphate, NiO, and Ni foam contributed to the excellent alkaline HER activity. Developing a cost-effective and stable electrocatalyst is the key to achieve the large-scale applications of water electrolysis to produce green hydrogen. Herein, an in situ hydrothermal growth strategy was put forward to prepare a novel self-supporting electrode, that is, Ni-based hydrogen phosphate polyhedrons supported on 3D Ni foam. This electrode was composed of crystalline (Ni(H 2 PO 4 ) 2 ·2H 2 O, Ni(H 3 P 2 O 7 ) 2 ·2H 2 O), and amorphous phase in which NiO nanoparticles formed. The amorphous phase connected polyhedrons to the Ni foam substrate, forming multifarious heterogeneous interfaces. Such a structure possessed large number of active sites, favored the fast reaction kinetics and electron transport rate, synergistically resulting in a superior alkaline HER performance. In alkaline electrolyte, the electrode only needed a small overpotential of 69 mV to reach the current density of 10 mA cm −2 with a small Tafel slope of 56 mV dec −1 , and exhibited a good stability at the current density of 100 mA cm −2 for 50 h. This in situ hydrothermal growth strategy opened up a new route to green synthesis of cost-effective and stable 3D heterostructured self-supporting electrode for water-splitting. An in situ hydrothermal growth strategy was used to prepare a novel Ni-based hydrogen phosphate polyhedrons self-supporting electrode. The electrode has multifarious heterogeneous interfaces, large number of active sites, and fast electron transport rate, synergistically resulting in a superior alkaline HER performance. Moreover, it exhibits a good stability at the high current density of 100 mA cm −2 for 50 h.