Surface reconstruction and structural transformation of two-dimensional Ni-Fe MOFs for oxygen evolution in seawater media

As a four-electron transfer reaction, oxygen evolution reaction (OER) is limited by large overpotential and slow kinetics. Here, we in-situ synthesized two-dimensional (2D) Ni-Fe metal-organic framework nanosheets on nickel foam (NixFe-TPA/NF, TPA = terephthalic acid) for oxygen evolution in alkaline and alkaline seawater electrolytes. In 1 M KOH, Ni3Fe-TPA/NF shows a low overpotential (η10) of 189 mV at 10 mA·cm−2 and an ultra-low overpotential of only 260 mV at 500 mA·cm−2. In alkaline seawater, Ni3Fe-TPA/NF still provides impressive OER performance, with an η10 of 265 mV. In-situ Raman characterization results show that the phase transition occurs during the OER, and Ni3FeOOH with more oxygen vacancies is in-situ formed, reducing the OER energy barrier. Density functional theory (DFT) reveals that the synergy between Ni and Fe reduces the energy barrier and accelerates the rate-determining step. In addition, the ultra-thin 2D sheet structure and the close combination of Ni3FeOOH and highly conductive NF support ensure the high catalytic OER activity. Therefore, the surface reconstruction and structural modification strategy can be used to design and prepare high-performance OER electrocatalysts for energy-related applications.