High entropy hydroxide with a hollow nanocage structure promotes efficient and stable water/seawater electro-oxidation.

High-entropy hydroxides (HEHs) exhibit excellent performance in electrocatalytic reactions, but controlling the synthesis of HEHs with a high specific surface area and rapid mass transfer kinetics is challenging. Herein, a series of hollow nanocage HEH catalysts decorated with nanosheet arrays were successfully synthesized by the "coordinated etching and precipitation" method. The hollow rich edge structure not only promotes the electrochemical mass transfer, but also has a high specific surface area and exposed active sites, which combined with the high entropy effect enhances the electrocatalytic performance. Theoretical calculations further confirm that the FeCoNiCuCrMn-OH HEH catalyst has a stronger adsorption capacity for OH than Cl, and can jointly improve the catalytic activity and corrosion resistance of the catalyst by effectively reducing the oxygen evolution reaction energy barrier and enhancing the resistance to Cl. In alkaline seawater electrolytes, only 275 and 292 mV overpotentials are needed to reach 100 and 200 mA cm. In addition, it has excellent stability and corrosion resistance, and can work stably for more than 400 hours when operating at 100 mA cm. This study provides new ideas for the morphology control and composition control of high-efficiency electrocatalysts.