Among　many　ways　that　can　improve　the　electrolysis　catalysts　of　seawater,　designing　the　catalyst　with　hierarchical　nanostructure　has　received　extensive　attention　because　it　allows　a　larger　surface　area　and　more　active　sites.　In　this　work,　the　NC-enveloped　CoS/NiS@Cu2S　catalyst　with　multi-level　structure　was　successfully　synthesized　by　using　the　complex　of　trithiocyanuric　acid　and　copper　as　the　metal　dopant　to　coat　the　spherical　Co-Ni　precursor,　and　then　by　a　straightforward　one-step　high-temperature　self-vulcanization　reaction.　Trithiocyanuric　acid　not　only　facilitated　the　sulfurization　of　metal　elements　but　also　served　as　N　and　C　source　coated　on　the　catalyst.　This　method　constructed　structure-controllable,　multi-level,　and　yolk-shelled　nanostructure　in　a　facile　manner,　greatly　increasing　specific　surface　area,　expanded　mass　transport　channels,　and　enhancing　the　exposure　of　active　sites.　Besides,　the　coating　of　N　and　C　elements　significantly　increased　the　electrical　conductivity　and　electrochemical　activity　of　the　catalyst.　As　a　result,　CoS/NiS@Cu2S@NC　exhibited　excellent　hydrogen　evolution　performance　with　the　small　overpotential　of　105,　161,　and　176　mV　at　10　mA　cm−2　in　alkaline　water,　simulated　alkaline　seawater,　and　alkaline　seawater,　respectively.　The　present　approach　is　proposed　as　an　inspirational　idea　of　the　design　of　cobalt–nickel-copper-based　multi-level　structural　nanomaterials　as　non-platinum　electrocatalysts　for　hydrogen　evolution　in　seawater.　©　2025　Elsevier　Ltd