Metal-Organic Framework-Derived FeCoS/CoO Heterostructure with Enhanced Electrocatalytic Performance for Oxygen Evolution and Hydrogen Evolution Reactions.

Herein, a versatile FeCoS/CoO heterostructure consisting of zeolitic imidazolate framework ZIF-derived CoO and FeCo-layered double hydroxide-derived Fe-doped Co sulfide is employed for the all-important alkaline full water splitting process. The heterostructure is prepared by combining pyrolysis and hydrothermal/solvothermal processes. The synthesized heterostructure possesses an electrocatalytically rich interface and renders excellent bifunctional catalytic performance. An overpotential of 139 mV for a standard cathodic current of 10 mA cm with a low Tafel slope of 81 mV dec is recorded for the hydrogen evolution reaction. An overpotential of 210 mV is observed for an anodic current of 20 mA cm with a low Tafel slope of 75 mV dec recorded for the oxygen evolution reaction. The full-symmetric two-electrode cell was capable of generating a current density of 10 mA cm at a cell potential of 1.53 V and a low onset potential of 1.49 V. The symmetric cell architecture exhibits remarkable stability, as a negligible potential increase is observed for continuous water splitting over a 10 h period. With the reported performance, the heterostructure compares well with most of the excellent reported catalysts for alkaline bifunctional catalysts.