Strong 3d–4d orbital coupling mechanism in high-en-tropy alloys enables industrial-level alkaline seawaterelectrolysis

Continuous seawater electrolysis for mass production of hydrogen suffersdrawbacks from electrode corrosion and low efficiency due to the presenceof multivalent ions in feed seawater. Herein, a strong 3d–4d orbital couplingmechanism is discovered in a FeNiCoMnRh high-entropy alloy (HEA), whichcan optimize the electron structure near the Fermi energy and reduce theuniversal reaction energy barrier. The HEA catalyst shows excellenthydro-gen/oxygen evolution reactions with overpotentials of 21 and 297 mV at 10mA cm−2, respectively, better than those of Pt/C and RuO2. Accordingly, itdelivers 500 mA cm−2 at 2.02 V and superior durability over 250 hours in ananion exchange membrane (AEM) seawater electrolyzer. More importantly,the AEM electrolyzer only requires 0.66 V to deliver 500 mA cm−2 when itcoupling with hydrazine oxidation. Thus, the 3d–4d orbital coupling mechanism in HEA can guide the development of green hydrogen fuel production.