Supercritical CO 2 ‐Assisted Ru/CoO With Room‐Temperature Ferromagnetism for Efficient Alkaline Oxygen Evolution

In this work, Ru/CoO catalysts with room‐temperature ferromagnetism have been successfully fabricated by a supercritical CO 2 ‐assisted synthesis coupled with a subsequent annealing strategy. Furthermore, the efficient oxygen evolution reaction (OER) of the as‐prepared catalyst has been demonstrated. Structural characterizations indicated that the room‐temperature ferromagnetism of Ru/CoO is mediated by Ru─O─Co interfacial coupling. Experimentally, it shows the unannealed CoCO 3 –Ru showed modest OER activity with an overpotential of 284 mV at 10 mA cm −2 ( η 10 ) and a charge‐transfer resistance ( R ct ) of 115 Ω, both higher than the benchmark values for commercial RuO 2 (229 mV and 37.7 Ω), which indicates that the loading of Ru alone therefore did not trigger efficient catalysis. After annealing, the resulting Ru/CoO catalyst required only η 10 of 150 mV and R ct of 34.1 Ω. In addition, durability tests confirmed stable operation at 100 mA cm −2 for 50 h. Therefore, all the results imply a correlation between spin ordering and OER catalytic performance.