Electronic structure modulation with ultrafine Fe3O4 nanoparticles on 2D Ni-based metal-organic framework layers for enhanced oxygen evolution reaction

Two-dimensional (2D) metal organic frameworks (MOFs) are emerging as low-cost oxygen evolution reaction (OER) electrocatalysts, however, suffering aggregation and poor operation stability. Herein, ultrafine Fe3O4 nanoparticles (diameter: 6 +/- 2 nm) are homogeneously immobilized on 2D Ni based MOFs (Ni-BDC, thickness: 5 +/- 1 nm) to improve the OER stability. Electronic structure modulation for enhanced catalytic activity is studied via adjusting the amount of Fe3O4 nanoparticles on Ni-BDC. The optimal Fe3O4/Ni-BDC achieves the best OER performance with an overpotential of 295 mV at 10 mA cm(-2), a Tafel slope of 47.8 mV dec(-1) anda considerable catalytic durability of more than 40 h (less than 5 h for Ni-BDC alone). DFT calculations confirm that the active sites for Fe3O4/Ni-BDC are mainly contributed by Fe species with a higher oxidation state, and the potential-determining step (PDS) is the formation of the adsorbed O* species, which are facilitated in the composite. (c) 2021 The Authors. Published by ELSEVIER B.V. and Science Press on behalf of Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

In this study, ultrafine Fe3O4 nanoparticles were immobilized on 2D Ni-based MOFs to enhance OER stability and catalytic activity. The optimal Fe3O4/Ni-BDC composite showed the best OER performance with higher overpotential, lower Tafel slope, and considerable durability, facilitated by Fe species with a higher oxidation state for the formation of adsorbed O* species.