Electrochemical Synthesis of High‐Valent Metal Oxides via In Situ Oxidant Generation with Real‐Time Phase and Composition Control

Abstract Unlike conventional electrosynthesis, which primarily targets homogeneous reactions, this study introduces a scalable electrochemical strategy for synthesizing high‐valent metal oxide powders with controlled crystalline phases. Reactive oxidants are generated in situ and modulated by applied potential and electrolyte composition, enabling selective transformation of α‐Co(OH) ₂ into trigonal γ‐CoOOH or brucite‐like β‐CoOOH through oxidant‐mediated phase control. Metal ions such as Ir, Cu, or Mo are directly incorporated during the phase transformation, yielding doped γ‐CoOOH with tailored composition. The resulting γ‐CoOOH exhibits superior oxygen evolution reaction activity in alkaline media, with further enhancement achieved through metal doping. This approach is also applicable to manganese‐based systems, enabling selective synthesis of γ‐MnO ₂ and δ‐MnO ₂ . The synthesis is readily integrated into a continuous‐flow system, allowing safe, waste‐minimized, and scalable production. These findings establish a new electrochemical methodology that unifies phase‐selective synthesis and in situ compositional control, offering a transformative route to the design of advanced electrocatalysts.