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

The oxygen evolution reaction (OER) is a pivotal half-reaction\nin water electrolysis to generate hydrogen. Currently, the development\nof efficient OER electrocatalysts is essential to accelerate the reaction\nprocess and enhance conversion efficiency. The MOF of NiFe-DTO (NiFe-D)\ncomposed of a dithiooxamide (DTO) ligand was constructed using nanosheet-like\nNiFe-LDH as the precursor and template. Eventually, a NiFe-DTO-derived\nNiSeS and Fe<sub>3</sub>Se<sub>4</sub> heterostructure electrocatalyst\nsupported on carbon cloth (NiFe-D-Se) was obtained by the subsequent\nselenization process. The results demonstrate that implanting NiFe-DTO\ncould induce the transition of crystal composition. The optimal NiFe-D-Se\ncatalyst is composed of NiSeS and Fe<sub>3</sub>Se<sub>4</sub> crystals\n(NiSeS@Fe<sub>3</sub>Se<sub>4</sub>), whereas the catalyst (NiFe-Se)\nderived from NiFe-LDH is made of Ni<sub>3</sub>Se<sub>4</sub> and\nFe<sub>3</sub>Se<sub>4</sub>. Ascribed to the different composition,\nthe high loading of Ni and Fe with low electronic density is gained\nin the NiFe-D-Se sample, which are active sites for the OER. In situ\nEIS test results indicate that NiFe-D-Se is easy to polarize. As a\nresult, the NiSeS and Fe<sub>3</sub>Se<sub>4</sub> heterostructure\nelectrocatalyst exhibits excellent OER performance in 1 M KOH with\nan overpotential of only 177 mV at 10 mA cm<sup>–2</sup> and\nhigh TOF and FE values, and the current degradation is only 2.15%\nand 3.56% after 24 and 120 h I-t test, respectively, which confirms\nthe outperforming performance in comparison with the advanced material\nreported recently. This work offers a feasible method for fabricating\nactive OER heterostructure electrocatalysts.