Two-Dimensional π–d-Conjugated Cobalt-Based Metal–Organic Framework for Efficient Oxygen Evolution

Metal–organic frameworks (MOFs) have been increasingly studied for electrocatalytic materials of the oxygen evolution reaction (OER) because of their tunable compositions, permanent porosity, multiple chemical functionalities, and well-dispersed metal centers. However, the electrocatalytic OER performance of conventional MOFs is limited due to their electrical conductivity. In this work, two-dimensional (2D) π–d-conjugated Co-based conductive MOFs (Co-HHTP) are first synthesized by a solvothermal method and used as the electrocatalysts for the OER. Density function theory calculations demonstrate that the obtained Co-HHTP has favorable electrical conductivity and a moderate d-band center, promoting the adsorption/desorption of the OER intermediates. As a result, the Co-HHTP shows an overpotential of 245 mV at a current density of 10 mA cm–2, a small Tafel slope of 70 mV dec–1, and great stability under alkaline conditions, exceeding Co(OH)2, Co3O4, and most of the reported MOF-based electrocatalysts. In situ Raman spectroscopy reveals that the CoOOH transformed from Co-HHTP is the real active species during the OER process. This work provides a promising candidate for electrocatalytic water splitting with a high efficiency.