In situ transformed three heteroleptic Co(II)-MOFs as potential electrocatalysts for the electrochemical oxygen evolution reaction

Abstract

Three Co(II)-MOFs, catena- [(diaqua-(μ2-bqdc-κO,O)-(phen-κN,N)-cobalt (II)] (1),{[Co(pa)(4,4′-bipy)(H2O) (CH3OH)]•DMF}n (2) and [Co(ia)(bpe)0.5(H2O)]n (3), (H2bqdc = 2,2-biquinoline-4,4′-dicarboxylic acid, phen = 1,10-phenanthroline), (H2pa = pamoic acid) (H2ia = itaconic acid, bpe = 1,2-bi(4-pyridyl)ethane) have been re-synthesized and thoroughly characterized by FT-IR, PXRD, SEM, EDX, HRTEM, BET surface area and UV/Vis techniques. The objective of choosing three Co(II)-MOFs 1–3 composed of different ligands and having 1D, 2D and 3D structures, respectively, was to have deep insights into role of linked ligands and the structural morphology toward electrocatalytic performance. MOFs 1–3 have been examined as electrocatalysts for water oxidation and comparative assessments revealed their catalytic performance in the order 2 > 3 ≈ 1. MOF 2 shows the best electrocatalytic activity for OER, which could be due to the higher amount of cobalt present in MOF-2, faster electron transfer kinetics and higher effective electrode surface area. The onset potential of MOF 2 was comparable or less as compared to benchmark catalysts IrO2 and Pt/C. Overall studies strongly suggest that MOF 2 could be promising materials for replacement of commercial high-cost electrode material.