The　design　and　synthesis　of　efficient,　inexpensive,　and　long-term　stable　heterostructured　electrocatalysts　with　high-density　dislocations　for　hydrogen　evolution　reaction　in　alkaline　media　and　seawater　are　still　a　great　challenge.　An　amorphous/crystalline/amorphous　sandwiched　structure　with　abundant　dislocations　were　synthesized　through　thermal　phosphidation　strategies.　The　dislocations　play　an　important　role　in　the　hydrogen　evolution　reactions.　Copious　dislocation　defects,　combined　with　cracks,　and　the　synergistic　interfacial　effect　between　crystalline　phase　and　amorphous　phase　regulate　the　electronic　structure　of　electrocatalyst,　provide　more　active　sites,　and　thus　endow　the　electrocatalysts　with　excellent　catalytic　activity　under　alkaline　water　and　seawater.　The　overpotentials　of　P-NiMoO4　at　10　mA/cm(2)　in　1　M　KOH　aqueous　solution　and　seawater　are　45　and　75　mV,　respectively.　Additionally,　the　P-NiMoO4　electrocatalyst　exhibits　long-term　stability　over　100　h.　This　study　provides　a　simple　approach　for　synthesizing　amorphous/crystalline/amorphous　sandwiched　non-noble-metal　electrocatalysts　with　abundant　dislocations　for　hydrogen　evolution　reaction.