Fe, S-uniformly dispersed Ni MOFs based on FeS substrate precipitation-dissolution equilibrium for water and seawater oxidation

Abstract

In the pursuit of advancing electrocatalysts for the alkaline oxygen evolution reaction (OER), the development of nickel-based metal–organic frameworks (MOFs) with a judicious balance of cost-effectiveness and catalytic efficacy is of paramount importance. Herein, we have achieved a commendable feat in the synthesis of Ni MOFs integrated with uniformly dispersed Fe and S species on a FeS substrate based on the precipitation-dissolution equilibrium. For the obtained Ni MOFs/FeS/IF catalyst, three factors including excellent conductivity of FeS substrate, conjugated carboxylate ligands and spindle-shaped structure with uniformly dispersed Fe and S can contribute to the enhanced activity for OER. The electrochemical measurements show that Ni MOFs/FeS/IF requires overpotentials of 250 and 280 mV to reach current densities of 100 mA cm⁻² in 1 M KOH and 1 M KOH seawater, respectively, as compared to that (427@100 mA cm⁻² in 1 M KOH, 455@100 mA cm⁻² in 1 M KOH seawater) of Ni MOFs/NF. Interestingly, the Ni MOFs/FeS/IF electrode displayed remarkable electrochemical stability with a high current density of 500 mA cm⁻² after testing for 50 h, which is attributed to the synergistic effect of the bimetallic centers and optimized coordination environments via Ni–S bonds. The study reveals the potential for efficiently driving freshwater and seawater splitting by uniformly distributing anions and cations based on the precipitation-dissolution equilibrium during the in situ generation of metal–organic frameworks toward advanced electrocatalysts.