Ligand-engineered Ru-doped cobalt oxides derived from metal-organic frameworks for large-current-density water splitting

The influence of the preorganized structure and chemical composition of metal-organic frameworks (MOFs) on the morphology, surface properties, and catalytic activity of the MOFs-derived metal oxides is yet to be revealed. In this work, two types of Co-MOFs with different coordination configurations are synthesized for the preparation of the structure-engineered ruthenium (Ru)-doped cobalt oxides. The effect of the preorganized coordination structure of the MOFs on the morphology and surface properties is investigated. Interestingly, the oxalate-based MOFs derived Ru-doped cobalt oxide (OX-Co3O4-Ru) exhibits much better surface wettability and more oxygen vacancies than the zeolitic imidazolate framework-67 derived Ru-doped cobalt oxide. As expected, the OX-Co3O4-Ru owns excellent catalytic properties towards both hydrogen evolution reaction and oxygen evolution reaction with an overpotential of 49 and 286 mV, respectively at a current density of 100 mA cm-2 in 1.0 M KOH. Importantly, the bifunctional OX-Co3O4-Ru catalyst offers an extremely high current density of 500 mA cm-2 at a cell voltage of 1.71 V for overall water splitting and as well demonstrates robust working stability.