Dynamic evolution of high-valence metals in high-entropy systems enabling highly enhanced oxygen evolution reaction

The incorporation of high-valence metals into FeCoNi-based oxide/hydroxide/oxyhydroxide matrices is widely acknowledged as an effective approach to enhance oxygen evolution reaction (OER) performance. Traditionally, it is assumed that these metals could maintain structural stability during operation. Here, our in-situ and ex-situ characterizations reveal that the dynamic electro-dissolution behavior of Mo 6+ and W 6+ species in FeCoNiMoW pre-catalyst leads to fast formation of catalytic-active (Mo, W) co-incorporated metal oxyhydroxides, which play a key role in the OER performance. This leaching process enables structural reconstruction, while concurrently optimizing the adsorption of the oxygen intermediate. The resulting catalyst exhibits exceptional OER activity, achieving an overpotential of 218 mV at 10 mA cm −2 , as well as remarkable stability with a degradation rate of only 8.7 μV h −1 over 720 h at 500 mA cm −2 . Furthermore, anion-exchange membrane water electrolyzers based on FeCoNiMoW//Pt/C can stably operate at 500 and 1000 mA cm −2 with low cell voltages of 1.70 and 1.84 V, respectively. The cost of the electric bill using this catalyst is notably low, at only $0.88 per kg, which is significantly below target of $2.00 per kg set by the U.S. Office of Clean Energy (OCE) for 2026. These findings offer valuable insights into the critical role of high-valence metals in advancing the OER process and underscore the substantial potential of this approach for industrial scale-up applications.