3D Printed Stiff Nickel Scaffolds Enabling Strained NiZn Catalysts for Ultra High‐Rate Alkaline Hydrogen Evolution Reaction at 3 A cm −2

ABSTRACT In this work, we propose a mechanics‐guided reactive substrate design concept that utilizes the substrate's mechanical properties (Young's modulus and ultimate strength) together with ordered scaffold geometry to control both intrinsic and extrinsic factors governing ultra‐high‐rate alkaline hydrogen evolution reaction (HER) performances. To realize this concept, we fabricate selective laser melting (SLM) 3D printed nickel (SLMN) lattices with dense and solid struts that support high‐loading Ni─Zn catalyst growth while preserving compressive strain in the surface layer. The resulting Ni—Zn catalyst coated SLMN (SLMN‐NZ) electrodes combine strain‐tuned intrinsic activity with ordered channels for rapid bi‐modal electrolyte‐bubble transport, and resist bubble‐induced mechanical shock under ultra‐high‐rate conditions. For example, the strained NiZn surface brings an increased number of highly intrinsic active sites with * H adsorption energies approaching thermoneutrality. The SLMN‐NZ electrode delivers 3000 mA cm −2 at just 156 mV overpotential and sustains at this current density for 200 h. An SLMN‐NZ||SLMN‐NZ electrolyzer achieves 3000 mA cm −2 at 2.45 V and operates stably for 1500 h. These results establish substrate mechanics as an active design parameter for electrocatalyst construction and demonstrate a transferable route to scalable, stable, and ultra‐high‐rate alkaline water electrolysis.