Developing efficient, durable, and economical electro-catalysts for large-scale commercialization of hydrogen evolution (HER) is still challenging. Herein, we report for the first time, to the best of our knowledge, a Pd-based ternary metal phosphide as an active and stable HER catalyst. The face-centered-cubic Pd-Ni-P nanoparticles (NPs) annealed at 400 degrees C show the best HER activity with a low overpotential of 32 mV to realize a current density of 10 mA cm(-2) and a high mass activity of 1.23 mA mu g(pd)(-1), superior to Pd NPs, Pd-P NPs, Pd-Ni NPs, and Pd-Ni-P NPs annealed under different temperatures. Moreover, this catalyst is also highly stable during 20 h of continuous electrolysis. Notably, the easily fabricated Pd-Ni-P NPs are among the most active Pd-based HER catalysts. This work indicates that Pd-based metal phosphides could be potentially applied as a type of practical HER catalyst and might inform the fabrication of analogous materials for hydrogen-related applications. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.