Regulation of Interface Active Site of Mofs ( Zif-67) Sulfide by Rgo to 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 to enhanced electrical conductivity and stability. The OER activity of the Co9S8@rGO core-shell heterostructure was investigated by varying the loading of rGO. It was found that the 30% Co9S8@rGOcore-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 ( ) 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.

Keywords: Co9S8, Electrocatalyst, Core-shell heterostructure, OER activity