Passivation Engineering Via Dynamic Construction of Amorphous Oxides on a Topologically Close‐Packed Phase for Sustainable Hydrogen Production

The pursuit of earth‐abundant electrocatalysts for acidic water electrolysis is fundamentally limited by a material‐design paradox: high activity necessitates reactive sites, yet these sites are inherently vulnerable to corrosion. Here, we present a paradigm shift that transforms corrosion from a destructive process into a useful synthesis tool. We demonstrate that a topologically close‐packed (TCP) intermetallic phase, when electrochemically activated in acid, naturally forms a self‐passivating, corrosion‐resistant amorphous oxide layer that establishes a durable and catalytically active interface. This corrosion‐built oxide layer enables exceptional hydrogen evolution reaction (HER) performance (90 mV at 10 mA/cm 2 ) coupled with extended stability (>200 h at 100 mA/cm 2 ). Our work establishes “passivation engineering” as a general design principle, leveraging guided corrosion to construct stable, active phases, offering a universal route to bridge the activity–stability divide in non‐precious electrocatalysis.