An efficient bulk electrocatalyst is appealing to advance the efficiency of water electrolysis. In this study, we report a function-integrated bulk NiFeOx@NiFeP catalyst that exhibits excellent electrocatalytic activity and stability properties. This new catalyst possesses multiple advantages including three-dimensional (3D) nano-porous framework structure, excellent macro-conductivity, and unique Mott-Schottky architecture, which offers stereochemical and energetic flexibility to interact with reactants with multiple functions including large surface area, fast mass and charge transfers, and favorable catalysis kinetics. The bulk NiFeOx@NiFeP can serve simultaneously as catalyst and current collector, and catalyze both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as demonstrated with active and durable overall water splitting performances.