To accomplish mass hydrogen production by electrochemical water-splitting,it is a necessary to develop robust,highly active,stable,and cost-effective hydrogen evolution reaction (HER) electrocatalysts that perform comparably to Pt in the universal pH range.In this work,cobalt phosphide hybrid nanosheets supported on carbon felt (CoP HNS/CF) are presented,which exhibit the superior electrocatalytic hydrogen production under a universal-pH.In these nanosheets,a single CoP HNS is composed of polycrystalline CoP and oxygen-enriched amorphous Co-O-P phase.Benefiting from its unique nanoarchitecture,as-fabricated CoP HNS/CF exhibits a tremendous electrocatalytic HER activity and outperforms Pt/C as well as state-of-the-art CoP electrocatalysts in universal-pH.In acidic and neutral media,the CoP HNS/CF shows superior electrocatalytic activity while maintaining its original hybrid crystalline-amorphous phase and morphology.In alkaline medium,the unexpected phase and morphological reorganization of CoP HNS/CF results in outstanding electrocatalytic operation.CoP HNS/CF not only achieves high electrocatalytic activity and kinetics,but also a stable and long operating lifetime even under a high current density of 500 mA·cm-2.Furthermore,the fabrication of CoP HNS/CF can be scaled up easily,and the large CoP HNS/CF electrode also exhibits similar electrocatalytic activity and stability.