S2−-modified hetero MOF-on-MOF of Ni-MOF/Fe-MOF with efficient seawater oxidation performance

Abstract

Direct seawater electrolysis offers a viable solution to the excessive consumption of fresh water resources in existing industrial electrolytic water processes. However, electrolysis efficiency and material stability are affected by electrode material corrosion caused by chlorine evolution reactions (CER) at the anode positions. In this study, the prepared S-Ni-MOF/Fe-MOF material exhibits an exceptional performance in the oxygen evolution reaction (OER) both in alkaline solution and seawater. Specifically, the material achieves low overpotentials of 281 and 279 mV in 1.0 M KOH and alkaline seawater at 100 mA cm−2 current density, and maintains stability for at least 100 h in both electrolyte solutions. The electronic structure of MOF-on-MOF was modulated through the introduction of S2−, which induced a large number of vacancies. Furthermore, the reconstruction process on the material surface was accelerated by the formation of NiOOH and FeOOH, that served as protective layers and prevented the corrosion of the electrode material by Cl−, thereby enhancing its stability in seawater. Furthermore, computational studies have indicated that the Fe-Ni active sites at the heterointerface exhibit a synergistic effect, which has been confirmed by density functional theory (DFT) calculations. These results prove that this combination significantly reduces the energy barrier associated with the OER. Consequently, the reaction process is accelerated.