High-efficiency　electrochemical　hydrogen　evolution　reaction　(HER)　offers　a　promising　strategy　to　address　energy　and　environmental　crisis.　Platinum　is　the　most　effective　electrocatalyst　for　the　HER.　However,　challenging　scarcity,　valuableness,　and　poor　electrochemical　stability　still　hinder　its　wide　application.　Here,　we　designed　an　outstanding　HER　electrocatalyst,　highly　dispersed　rhodium　(Rh)　nanoparticles　with　an　average　diameter　of　only　3　nm　supported　on　boron　(B)　nanosheets.　The　HER　catalytic　activity　is　even　comparable　to　that　of　commercial　platinum　catalysts,　with　an　over-　potential　of　only　66　mV　in　0.5　M　H2SO4　and　101　mV　in　1　M　KOH　to　reach　the　current　density　of　10　mA　cm(-2).　Meanwhile,　the　catalyst　exhibited　impressive　electrochemical　durability　during　long-term　electrochemical　processes　in　acidic　and　alkaline　media,　even　the　simulated　seawater　environment.　Theoretical　calculations　unraveled　that　the　structure-activity　relationship　between　B(104)　crystal　plane　and　Rh(111)　crystal　plane　is　beneficial　to　the　release　of　hydrogen,　and　surface　O　plays　a　vital　role　in　the　catalysis　process.　Our　work　may　gain　insights　into　the　development　of　supported　metal　catalysts　with　robust　catalytic　performance　through　precise　engineering　of　the　strong　metal-supported　interaction　effect.