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

Abstract

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-Co_xS_y) 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-Co_xS_y 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-Co_xS_y 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.