Supported metal catalysts often suffer from rapid degradation under harsh conditions due tomaterial failure andweakmetal-support interaction. Here we propose using reductive hydrogenated borophene to in-situ synthesize Pt/B/C catalysts with small sizes (~2.5 nm), high-density dispersion (up to 80 wt%Pt), and promising stability, originating from forming Pt-B bond which are theoretically ~5× stronger than Pt-C. Based on the Pt/B/C module, a series (~18 kinds) of carbon supported binary, ternary, quaternary, and quinary Pt intermetalliccompound nanocatalysts with sub-4 nm size are synthesized. Thanks to the stable intermetallics and strong metal-support interaction, annealing at 1000 °C does not cause those nanoparticles sintering. They also show much improved activity and stability in electrocatalytic oxygen reduction reaction. Therefore, by introducing the boron chemistry, the hydrogenated borophene derived multielement catalysts enable the synergy of small size, high loading, stable anchoring, and flexible compositions, thus demonstrating high versatility toward efficient and durable catalysis.(See Nature Communications | ( 2023) 14:7414)