A theoretical study on the surface and interfacial properties of Ni₃P for the hydrogen evolution reaction

We report a comprehensive density functional theory (DFT) study on the stability, geometric structure, electronic characteristics, and catalytic activity for the hydrogen evolution reaction (HER) on low-index Ni₃P crystal surfaces, namely, the (001), (100), (110), (101) and (111) planes with different surface terminations. The results indicate that P-rich and some stoichiometric surfaces are thermodynamically stable. Eight stable surfaces were selected to investigate the electronic characteristics and catalytic activity. The (110)B facet of Ni₃P is indispensable for the HER, because it not only displays improved electrocatalytic activity, but also possesses suitable potential and high stability. Increasing the active sites through doping or enlarging the surface area could be a useful strategy to improve the HER activity further. Furthermore, it was found that Ni₃P requires higher energies for decomposition in the absence of O₂, although it is thermodynamically unstable in aqueous solutions with most pH values and potentials. This study provides important insights into the surface properties of Ni₃P for water splitting and opens up an exciting opportunity to optimize the performance of solar energy conversion devices by synthesizing preferentially exposed catalyst facets.