Catalytic hydrolysis of ammonia borane has tremendous potential as an energy-efficient approach to supply hydrogen for energy vehicles and portable electronic devices. Herein, DFT calculation is first performed on electronic properties of Ni2P and Ni5P4 nanocatalysts. It is found that more electrons are transferred from Ni to P for Ni5P4, indicating that Ni5P4 may show superior performance based on the electron effect. Therefore, Ni2P and Ni5P4 with high purity are synthesized by the phase-controlled thermal decomposition approach. Gratifyingly, the Ni5P4 catalyst exhibits the as-expected better catalytic activity than that of Ni2P catalyst. It also shows low activation energy and good stability. Furthermore, the structures and morphologies of both catalysts are characterized by multi-techniques such as XRD, HRTEM and XPS.The better performance could be ascribed to the higher positive charge of Ni together with the stronger ensemble effect of P. The insights sheds new light on the design of efficient Ni-P catalysts for hydrogen generation.