Nickel Sulfide/Hierarchical Porous Carbon from Spent Residue Hydrocracking Catalyst as Electrocatalyst for the Oxygen...

Spent residue slurry-phase hydrocracking catalyst coated with coke have been classified as hazardous solid waste, presenting serious economic and environmental issues to refiners. Herein, the spent catalysts with a nickel sulfide nanoparticle/coke hierarchical structure (NiS_X /C) from our previous work were used to prepare nickel sulfide/hierarchical porous carbon (NiS_X /HPC) for the oxygen evolution reaction (OER) through the method of carbonization, activation, and sulfurization. The results indicate that the NiS_X /C converts into Ni/HPC after carbonization and activation, and then transform into NiS_X /HPC by sulfurization. The optimized NiS_X /HPC-8 possesses the crystal phase of NiS₂ , and the high specific surface area of 1134.9 m²  g^-1 with the hierarchical micro-mesoporous structure. Besides, NiS_X /HPC-8 achieves a low overpotential of 236 mV at 10 mA cm^-2 , a low Tafel slope of 64.1 mV dec^-1 , and excellent stability. This work provides a viable method for upcycling spent catalysts to re-constructed OER catalysts with high catalytic performance and durability.