Self-Reconstructed Crystalline-Amorphous (Ni, Fe)OOH/NiFeS2 Heterostructure on NiFe-S Aerogel Electrocatalyst Enables High-Performance Electrochemical Seawater Oxidation

Seawater electrolysis offers a viable strategy for the large-scale production of clean hydrogen. However, the oxygen evolution reaction (OER) catalysts is often compromised by the competitive chloride evolution reaction and the associated corrosion in seawater environments. Herein, we present a novel NiFe-S aerogel (AG) electrocatalyst featuring a porous 3D-network structure and a core-shell architecture. This catalyst demonstrates outstanding OER performance, achieving a low overpotential of 260 mV at 100 mA cm- 2, a Tafel slope of 55 mV dec-1, and remarkable stability exceeding 500 h at 500 mA cm- 2 in alkaline natural seawater. Through combined experimental and computational analyses, we discovered that the self-reconstructed crystalline-amorphous (Ni, Fe)OOH/NiFeS2 heterojunction is pivotal to the outstanding performance of the NiFe-S AG electrocatalyst. The unique heterostructure facilitates electron transfer and down shifts the d-band center of the active sites, optimizing the adsorption strength of oxygen-containing intermediate species. Moreover, the stability is augmented by increased Fe and Ni vacancy formation energies, and higher affinity for OH- over Cl-, hence attenuating the corrosion from Cl- and suppressing the leaching of active sties. This work highlights the significance of the crystalline-amorphous heterojunction in aerogel catalyst and offers new insights into the design of efficient electrocatalysts for seawater oxidation.