Single-atom　catalysts　(SACs),　as　a　thriving　subfield　of　catalysis,　have　progressed　tremendously.　However,　the　contradiction　between　the　isolated　dispersion　feature　of　metal　sites　and　the　high　mass-specific　activity　of　the　catalyst　inhibits　the　advances　of　the　SACs.　Herein,　the　Pt　atoms　are　confined　at　the　metallic　Co　phase　edge　in　two-dimensional　Co/Co(OH)2　hierarchy　structure　(PtSA-Co@Co-Co(OH)2)　by　the　defect　inducted　order　electrodeposition　strategy.　Both　integrations　of　in-situ/ex-situ　experimental　characterizations　and　theoretical　calculation　reveal　that　such　metal　edge　confined　Pt　atoms　possess　an　enlarged　atom　exposure　ratio,　high　stability,　and　the　like-metal　electronic　state　contributed　by　metal　Co　3d,　which　enables　the　Pt　atoms　with　more　suitable　affinity　to　simultaneously　bind　the　multiple　H　atoms　for　durable　H*-H2　conversion　and　H2　evolution.　Moreover,　the　metallic　PtSA-Co　collaborated　Co/Co(OH)2　interfaces　demonstrate　a　strong　H2O　dissociation　capacity　by　the　preference　adsorption　of　H*　on　metallic　PtSA-Co　and　OH*on　Co/Co(OH)2　interfaces.　Combining　a　further　enhancement　of　constructing　the　catalysts　on　an　Ag　nanowire　network　to　form　a　seamlessly　conductive　nanostructure,　the　PtSA-Co@Co-Co(OH)2　achieves　a　high　mass　activity　with　5.92　A　mg−1　at　the　overpotential　of　100　mV　in　alkaline　condition,　37　times　to　that　of　the　benchmark　Pt/C　catalyst　and　significantly　outperforming　the　reported　catalysts.　While　our　work　has　focused　on　the　hydrogen　evolution　reaction,　this　class　of　metal　edge　collaborated　single-atom　catalysts　may　be　conducive　to　unlock　the　low　mass-specific　activity　of　atomically　dispersed　catalysts　for　various　processes,　such　as　oxygen　evolution　reactions　(OER),　CO2　reduction,　and　biomass　conversion,　etc.　©　2024　Elsevier　B.V.