Unveiling the real active sites of Ni based metal organic framework electrocatalysts for the oxygen evolution reaction

Pristine metal organic frames (MOFs) have emerged directly as the electrocatalysts for oxygen evolution reaction (OER). However, the OER performance needs further improvement and the real active sites remain exclusive. Herein, the effect of ligands on the performance of MOFs and the real active sites of each MOFs were explored. Specifically, three Ni based metal organic frames (Ni-MOFs) with different ligands including formic acid (FA), 1,4-benzenedicarboxylic acid (BDC) and 1,3,5-benzenetricarboxylic (BTC) were prepared by a solvothermal method. The morphology, specific surface area, porosity, wettability, electrochemically surface area (ECSA) of each Ni-MOFs were tested. However, none of them could be well correlated to the OER performance except the content of Ni(OH)2 on the surface from XPS test. Moreover, the OER performance of each Ni-MOF could be improved by cyclic voltammetry (CV) and chronopotentiometry (CP). The morphology and composition of each Ni-MOF before and after electrochemical activation further reveal the real active sites of three Ni-MOFs investigated here were Ni(OH)2. These results were expected to provide useful information for designing more excellent OER electrocatalysts based on MOFs.