AbstractConstructing highly‐active and robust electrodes is vital for the industrialized application of water electrolysis to produce green hydrogen. Nevertheless, the strong disturbance of gas bubbles, especially under ampere‐level current densities, would bring about the exfoliation of catalytically active materials and performance deterioration. Herein, a Ru‐doped Ni(OH)₂ultrathin nanosheet array vertically grown on nickel foam with a mechanically‐robust interface is first constructed by a facile corrosive engineering strategy. Subsequently, thermal shrinkage engineering inspired by heat shrinkable film is applied to avoid the region away from the interface in ultrathin nanosheets from being damaged by the impact of intensive gas evolution. As a result, the final self‐supported electrode has plentiful features including robust binding at the electrocatalyst/support interface and amorphous/crystalline heterophase. These features promote the achievement of superior catalytic activity of a small overpotential of 400 mV and activity retention for over 100 h at 2000 mA cm⁻²current density.