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ABSTRACT Metal/carbon‐based nanocomposites have attracted significant interest for electrochemical water splitting due to their unique interfacial electronic structures, abundant active sites, and catalytic bifunctionality toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, Co/CoO‐rGO composites consisting of Co/CoO heterostructured nanoparticles encapsulated within a graphitized carbon scaffold are produced via magnetic induction heating at controlled currents for 10 s with cobalt(II) nitrate and reduced graphene oxide (rGO) loaded on nickel foam and effectively catalyze both HER and OER in alkaline media. Among the series, the sample prepared at 400 A for 10 s exhibits the best performance, featuring an overpotential of −144 mV for HER and +390 mV for OER at 10 mA cm⁻²and 50 mA cm⁻², respectively. The bifunctional activity can then be exploited for full water splitting, where a low cell voltage of 1.61 V is needed to generate a current density of 10 mA cm⁻², 260 mV better than that with commercial Pt/C and RuO₂. The remarkable performance is attributed to the synergistic interaction between the Co and CoO domains, enhanced charge transfer at the heterojunction interface, and conductive carbon support. These results highlight the potential of Co/CoO‐based nanocomposites as efficient and low‐cost catalysts for overall water splitting and the scalability of the MIH technology. 

Abstract Development of high‐performance, low‐cost catalysts for electrochemical water splitting is key to sustainable hydrogen production. Herein, ultrafast synthesis of carbon‐supported ruthenium–copper (RuCu/C) nanocomposites is reported by magnetic induction heating, where the rapid Joule's heating of RuCl₃and CuCl₂at 200 A for 10 s produces Ru–Cl residues‐decorated Ru nanocrystals dispersed on a CuCl_xscaffold, featuring effective Ru to Cu charge transfer. Among the series, the RuCu/C‐3 sample exhibits the best activity in 1 mKOH toward both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with an overpotential of only −23 and +270 mV to reach 10 mA cm⁻², respectively. When RuCu/C‐3 is used as bifunctional catalysts for electrochemical water splitting, a low cell voltage of 1.53 V is needed to produce 10 mA cm⁻², markedly better than that with a mixture of commercial Pt/C+RuO₂(1.59 V). In situ X‐ray absorption spectroscopy measurements show that the bifunctional activity is due to reduction of the Ru–Cl residues at low electrode potentials that enriches metallic Ru and oxidation at high electrode potentials that facilitates the formation of amorphous RuO_x. These findings highlight the unique potential of MIH in the ultrafast synthesis of high‐performance catalysts for electrochemical water splitting. 

Synergetic interactions between ruthenium and molybdenum oxide weaken H adsorption on ruthenium active sites and hence enhance the electrocatalytic activity towards hydrogen evolution reaction.