Preparation and investigation of Fe-MIL-101 as efficient catalysts for oxygen evolution reaction

In recent years, metal-organic frameworks (MOFs) have gradually been used in the field of oxygen evolution reaction (OER). In order to improve OER performance, MOFs are usually used as precursors to prepare metal oxide/porous carbon composites by pyrolysis at high temperatures in previous studies. Although metal oxide/porous carbon composites show high catalytic activity, they require complicated preparation processes and high temperature. Therefore, it is very significant to find a highly efficient MOFs, which can be directly used as OER without pyrolysis treatment. The results show that when Co-ZIF-67/NF, Ni-MOF-74/NF and Fe-MIL-101/NF are used as OER catalysts in 1 mol/L KOH solution, 377, 383 and 272 mV overpotentials are required to make the current density achieve 10 mA/cm². The charge transfer resistance (R_ct) of Fe-MIL-101/NF is 1.53 Ω, which is smaller than that of Co-ZIF-67/NF (32.40 Ω) and Ni-MOF-74/NF (43.78 Ω). Therefore, the higher of the R_ct of the catalyst, the smaller of the charge transfer capacity in the OER process. Thus, the fast charge transfer rate is the main reason for the excellent OER activity of Fe-MIL-101/NF. In addition, the OER activity of Fe-MIL-101/NF (272 mV) without pyrolysis treatment is much higher than that of commercial RuO₂/NF (302 mV), indicating that MOFs with fast charge transfer rate can be used as an efficient catalyst for OER without calcination.