Hollow ZIF-67 derived porous cobalt sulfide as an efficient bifunctional electrocatalyst for overall water splitting

The design and construction of noble-metal free electrocatalysts with high efficiency for both hydrogen and oxygen evolution reactions holds promise for advancing the production of H2 fuels through the overall water splitting process. Herein, we report a novel hollow near-spherical superstructure of a cobalt sulfide electrocatalyst (h-CoxSy) via the accumulation of two-dimensional cobalt sulfide nanosheets in a sulfurization-pyrolysis process of hollow ZIF-67. Benefiting from the porous characteristics, a unique hollow superstructure and saw-toothed edges derived from the hollow ZIF-67 precursor, the h-CoxSy exhibited outstanding bifunctional electrocatalytic performances, with overpotentials of 320 and 295 mV to achieve 10 mA cm−2 for the OER and HER, respectively. When h-CoxSy was employed as both the anode and cathode for overall water splitting, a current density of 10 mA cm−2 can be obtained at a cell voltage of 1.88 V, along with impressive operation stability.