Cerium-Doped Nickel Phosphide Nanosheet Arrays as Highly Efficient Electrocatalysts for the Hydrogen Evolution Reaction in Acidic and Alkaline Conditions

Developing inexpensive electrocatalysts with high activity and stability is of great value for the hydrogen evolution reaction (HER) in both acidic and alkaline environments. Despite serving as a model catalyst at the beginning of research studies on transition-metal phosphides, nickel phosphide (Ni2P) has not been an excellent HER electrocatalyst to date. Heteroatom incorporation is an effective strategy to optimize the electro-catalytic activities of materials. In this research, Ni2P nanosheet arrays doped with cerium elements were prepared through a facile hydrothermal process and subsequent phosphorization. In comparison with other similar phosphor-nickel-based catalysts, the superior electrocatalytic activity for the HER can be achieved in Ce-doped Ni2P, attributed to the cooperative effects from more active sites and higher intrinsic activity derived from the introduction of Ce heteroatoms. Ce-doped Ni2P with a Ce/Ni atomic ratio of 12.3% requires as low as 42 and 77 mV to achieve 10 mA cm-2 in acidic and basic environments, respectively. Compared with Pt/C, Ce-doped Ni2P shows a lower overpotential at a high current density (>220 mA cm-2). The outstanding electrocatalytic stability could be confirmed in cycling stability testing of 5000 cycles and continuous testing of 100 h at a current density of 20 mA cm-2. This work offers an efficient and stable alternative to scarce noble metal-based electrocatalysts for sustainable hydrogen generation from water electrolysis.