Core-shell like rGO coated Co9S8 hollow dodecahedron for enhanced oxygen evolution reaction

Abstract

The development of low-cost, high-activity, high-durability non-precious metal OER electrocatalysts is still the most critical bottleneck for the preparation of clean-energy by water splitting. In this thesis, the Co₉S₈@rGO heterogeneous interface was constructed to optimize the electron transport pathway and enhance the active site to improve the OER activity. The ZIF-67 dodecahedron was used as a template to prepare Co₉S₈ with a hollow dodecahedron structure using the hydrothermal method and annealing treatment to shorten the charge transport path and increase its specific surface area. Subsequently, a protective shell layer of rGO with good conductivity and stability was wrapped around the Co₉S₈ catalyst core by the construction of a Co₉S₈@rGO core-shell heterostructure. It was found that the 30 % Co₉S₈@rGO core-shell heterostructure not only reduced the overpotential (190 mV at 10 mA cm⁻²) and tafel slope (66.48 mV dec⁻¹) but also improved the stability compared to Co₉S₈. The density of states and the Gibbs free energy of HO*, O* and HOO* intermediates of Co₉S₈@rGO were investigated by first-principles theoretical calculations according to density functional theory (DFT). The DFT calculation results showed that the Gibbs free energy ($\Delta G_3^0$) of Co₉S₈@rGO core-shell heterostructure was lower than that of Co₉S₈ in the rate-control step, which leaded to the decrease of overpotential and was beneficial to the OER reaction.