Obtaining the High Valence of Ni/Fe Sites in a Heterostructure Induced by Implanting the NiFe-DTO MOF as a Highly Active OER Catalyst

Abstract

The oxygen evolution reaction (OER) is a pivotal half-reaction in water electrolysis to generate hydrogen. Currently, the development of efficient OER electrocatalysts is essential to accelerate the reaction process and enhance conversion efficiency. The MOF of NiFe-DTO (NiFe-D) composed of a dithiooxamide (DTO) ligand was constructed using nanosheet-like NiFe-LDH as the precursor and template. Eventually, a NiFe-DTO-derived NiSeS and Fe₃Se₄ heterostructure electrocatalyst supported on carbon cloth (NiFe-D-Se) was obtained by the subsequent selenization process. The results demonstrate that implanting NiFe-DTO could induce the transition of crystal composition. The optimal NiFe-D-Se catalyst is composed of NiSeS and Fe₃Se₄ crystals (NiSeS@Fe₃Se₄), whereas the catalyst (NiFe-Se) derived from NiFe-LDH is made of Ni₃Se₄ and Fe₃Se₄. Ascribed to the different composition, the high loading of Ni and Fe with low electronic density is gained in the NiFe-D-Se sample, which are active sites for the OER. In situ EIS test results indicate that NiFe-D-Se is easy to polarize. As a result, the NiSeS and Fe₃Se₄ heterostructure electrocatalyst exhibits excellent OER performance in 1 M KOH with an overpotential of only 177 mV at 10 mA cm^–2 and high TOF and FE values, and the current degradation is only 2.15% and 3.56% after 24 and 120 h I-t test, respectively, which confirms the outperforming performance in comparison with the advanced material reported recently. This work offers a feasible method for fabricating active OER heterostructure electrocatalysts.