Metal-organic framework-derived cobalt oxide and sulfide having nanoflowers architecture for efficient energy conversion and storage

Water electrolyzers coupled with fuel cells offer a close loop of sustainable energy, requiring supercapacitors as energy storage devices; however, the performance of such devices largely depends on corresponding electrode materials. Metal oxides and sulfides containing Fe, Co, and Ni metals, in particular, have created significant interest due to their tunable and high theoretical energy performance for such devices. Herein, metal-organic framework (MOF) derived cobalt oxide (MOF-Co3O4) and sulfide (MOF-Co9S8) have been synthesized using solvothermal and hydrothermal strategies. The MOF-Co3O4 exhibited an overpotential of 375 and 213 mV for OER and HER, whereas, MOF-Co9S8 being a better electrocatalyst, displayed an overpotential of 278 and 212 mV for the same, respectively, at 10 mA/cm(2). The theoretical evaluation suggested that incorporation of S-atoms with Co active sites in MOF-Co9S8 significantly reduced the energy barriers for crucial elementary processes of OER and HER, endowing its electrocatalytic activity. In addition, MOF-Co9S8 with a specific capacitance of 2831 F/g was found to have over four times higher energy storage capacity than MOF-Co3O4 with a 674 F/g specific capacitance @1 mA/cm(2).

Automated summary

Metal-organic framework (MOF) derived cobalt oxide and sulfide show potential for high performance energy storage in water electrolyzers and fuel cells, with MOF-Co9S8 exhibiting superior electrocatalytic activity.