Research Article Issue
Surface reconstruction and structural transformation of two-dimensional Ni-Fe MOFs for oxygen evolution in seawater media
Nano Research 2024, 17 (4): 2429-2437
Published: 07 September 2023

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.

Research Article Issue
Synergy between isolated Fe and Co sites accelerates oxygen evolution
Nano Research 2023, 16 (2): 2218-2223
Published: 22 October 2022

Dual-metal catalysts with synergistic effect exhibit enormous potential for sustainable electrocatalytic applications and mechanism research. Compared with mono-metal-site catalysts, dual-metal-site catalysts exhibit higher efficiency for the oxygen evolution reaction (OER) due to reduced energy barrier of the process involving proton-coupled multi-electron transfer. Herein, we construct dual-metal Fe-Co sites coordinated with nitrogen in graphene (FeCo-NG), which exhibits high OER performance with onset overpotential of only 126 mV and Tafel slope of 120 mV·dec−1, showing that the rate-determining step is controlled by the single-electron transfer step. Theoretical calculations reveal that the FeN4 site exhibits lower OER overpotential than the CoN4 site due to appropriate adsorption energy of OOH* on the former, while the O* adsorbed on the adjacent Co site could stabilize the OOH* on the FeN4 site through hydrogen bond interaction.

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