Charge competition enhancing Ru-based high entropy oxide nanosheet for efficient and stable oxygen evolution

The sluggish kinetics of the oxygen evolution reaction (OER) caused by the complex process significantly hinder the advancement of electrolytic water to hydrogen technology. Herein, the valence of Ru is modulated and stabilized through inducing the electronic competition between Mo and Ru, and the charge transfer from Fe, Co, and Ni to Ru in 2D porous FeCoNiMoRu high entropy oxides (HEO) nanosheets to achieve efficient and stable OER. The 2D porous structure of FeCoNiMoRu HEO contributes to the high exposure of active sites while promoting rapid mass transfer, which can facilitate oxygen-evolving kinetics of the catalyst. Consequently, the optimized catalyst (FeCoNiMoRu HEO) surpasses RuO 2 (315 mV) in OER catalytic activity, exhibiting an overpotential of 226 mV at 10 mA cm −2 . Notably, the mass activity of FeCoNiMoRu HEO is nearly 18.6-fold that of RuO 2 . Combined experimental and theoretical analysis, a charge competition between Mo and Ru atoms, and the charge transfer from Fe, Co, and Ni elements to Ru in HEO can buffer the change of valence of Ru and modulate its electronic structure, thus enhancing the activity and durability of FeCoNiMoRu HEO during OER.