Ultrafast Synthesis of Ru/RuO ₂ /Mn ₃ O ₄ Heterostructures as High‐Performance Bifunctional Electrocatalysts for Acidic Water Splitting

Development of efficient and durable electrocatalysts for acidic water electrolysis is critical for sustainable hydrogen production. Herein, we report the ultrafast synthesis of Ru/RuO 2 /Mn 3 O 4 heterostructure composites via magnetic induction heating at controlled currents, which enables rapid formation of well‐defined interfaces between metallic Ru, RuO 2 , and Mn 3 O 4 within seconds. Among the series, the sample prepared at 300 A for 10 s (RuMn‐300) exhibits the best electrocatalytic performance towards both hydrogen evolution reaction and oxygen evolution reaction in 0.5 M H 2 SO 4 , requiring a low overpotential of only −41 mV and +223 mV to reach the current density of 10 mA cm −2 , respectively. Microscopic and spectroscopic characterizations confirm the formation of nanoscale heterostructures that feature strong electronic coupling and multiple valencies, where Mn 3 O 4 modulates the Ru electronic structure, stabilizes the Ru species, and enhances charge transfer, collectively resulting in improved electrocatalytic activity and durability. With RuMn‐300 as the anodic and cathodic catalysts, an electrolyzer is constructed achieving 10 mA cm −2 in overall water splitting at a low cell voltage of 1.58 V, with excellent long‐term stability, which outperforms that based on commercial Pt/C and RuO 2 benchmarks by 290 mV. This work highlights the unique potential of ultrafast synthesis in heterostructure engineering of high‐performance bifunctional electrocatalysts for electrochemical energy technologies.