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

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-MnO₂ and δ-MnO₂. 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.