Tailoring　cobalt　phosphide　electrocatalysts　with　a　tunable　phase　and　morphology　is　of　great　importance　for　the　advancement　of　hydrogen　evolution　reaction　(HER).　The　synthesis　of　phase-　and　morphology-modulated　hollow　cobalt　phosphide　nanoparticles　coupled　with　N,　P,　S　co-doped　carbon　(Co-P@NPS-C)　polyhedrons　through　a　facile　three-step　method　is　reported.　Benefiting　from　the　cooperation　of　structural　features,　heteroatoms　doping,　and　catalytic　components　(Co　x　P,　a　mixture　of　CoP　and　Co　2　P),　the　hollow　Co　x　P@NPS-C　polyhedrons　exhibit　superior　HER　performance　and　long-term　stability　in　1.0 m　KOH　solution,　with　a　low　onset　potential　value　(18 mV),　an　overpotential　of　80 mV　at　10 mA cm　−2　,　and　a　small　Tafel　slope　of　57.6 mV dec　−1　.　In　addition,　the　Co　x　P@NPS-C　electrodes　exhibit　good　electrochemical　properties　and　stability　in　0.5 m　H　2　SO　4　solution.　These　results　suggest　a　novel　and　promising　coating　approach　with　poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol　(PZS)　to　fabricate　other　heterogeneous　catalysts　for　various　applications.　©　2019　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim