Facile electrocatalyst development with minimum energy consumption is highly beneficial for practical water splitting. Scale up of lab-scale active catalysts presents challenges to this end. Here, we take advantage of the spontaneous corrosion electrochemistry to make nonprecious multi-metallic hydroxides for efficient oxygen evolution reaction in alkaline electrolytes. Ternary FeNiCr and FeCoCr hydroxides are developed by oxygen- and sulfate-mediated corrosion engineering of macroporous Fe foam substrates. Cr doping is successfully achieved for regulating and accelerating the in situ phase transformation of Ni active sites into oxyhydroxide active phase to afford high intrinsic electrocatalytic activity and surface-intermediate interactions. Low overpotentials of 323 and 329 mV are achieved for delivering a large current density of 500 mA cm–2 using FeNiCr and FeCoCr electrocatalysts, respectively. Long-term stability at large current densities, reproducible performance, and facile scale up obtained suggests a great potential of designing highly efficient multi-metal electrocatalysts for water electrolysis technologies by corrosion engineering.

Hard carbon has attracted great attention for energy storage owing to low cost and extremely high microporosity, however, hindered by its low electrical conductivity. The common strategy to improve the conductivity is through graphitization process which requires temperatures as high as 3000 °C and inevitably destroys the porous structure. Herein, a balance between the specific surface area and electrical conductivity in a 3D porous hard carbon by in situ iron‐catalyzed graphitization process together with the Si–O–Si network is successfully achieved. The Fe can accelerate the localized graphitization at relatively low temperature (1000 °C) to form nanographite domains with enhanced conductivity, while the Si–O–Si network contributes to generating a 3D porous structure. As a result, the optimized hard carbon exhibits a 3D interconnected and hierarchical porous structure with extremely high specific surface area (2075 m2  g−1) and excellent electrical conductivity (12 S cm−1) which is comparable with that of artificial graphite. And thus, high capacitance of 315 F g−1 and excellent rate capability (174 F g−1 at 40 A g−1) are simultaneously achieved when used as electrodes for supercapacitors. The strategy is promising to build hard carbon materials with well‐tuned properties for high‐performance energy storage.