Palladium phosphides are explored as efficient catalysts for the electrocatalytic reduction of nitrate to ammonia (NRA). The explored PdP2 nanoparticles on reduced graphene oxide exhibit the maximum NH3 Faradaic efficiency of 98.2% with a corresponding NH3 yield rate of 7.6 mg h-1 cm-2 at -0.6 V (RHE). Theoretical calculations reveal that a PdP2 (011) surface can not only effectively activate and hydrogenate NO3- via a NOH pathway but also retard H adsorption to inhibit the competitive hydrogen evolution reaction.