Charge Equalization Strategy for Regulating Key Intermediate Adsorption on Bifunctional Fecr-Ni3s2 to Boost Seawater Splitting

Seawater splitting offers a sustainable way to meet the crises of globe warming and energy shortage. Bifunctional electrocatalysts for both oxygen and hydrogen evolution reaction (OER, HER) and naturally resistant for chlorine evolution reaction (CER) are highly anticipated. Here, we developed a charge equalization strategy through bimetallic doping and successfully constructed bifunctional electrocatalysts of FeCr-Ni3S2 by the in-situ growth on the Nickel foam (NF). After composition optimization, FeCr-Ni3S2 exhibits both excellent catalytic OER and HER performance. DFT calculations reveal the bimetallic doping of Fe and Cr in Ni3S2 synergistically drives the d-band center of Ni away from its Fermi energy level and weakens the activity of Ni site. Owing to this charge equalization, *O intermediate adopts a hetero-bidentate adsorption configuration of Ni-O-Cr. Consequently, the potential determining step of *OOH adsorption reversely transports on the Cr site, providing a significant reduction of the energy barrier and prompting intrinsic activity of the sluggish OER. As a result, the overall seawater splitting only requires 1.824 V to achieve a current density of 500 mA cm-2. Most importantly, the overpotential of 307 mV was achieved on FeCr-Ni3S2 in the alkaline natural seawater, which is much lower than that the overpotential of 490 mV required to trigger the CER. More significantly, when coupling with the urea oxidation reaction (UOR), the voltage of the urea-assisted seawater splitting keeps on decreasing to 1.676 V stably for 500 h, superior to all state-of-the-arts works, which offers a feasible strategy for achieving energy-efficient seawater electrolysis hydrogen production.