Electrocatalytic effect of Co3V2O8 nanospheres loaded on Cu-doped MoS2 nanosheets toward enhanced oxygen reduction reaction

Abstract

Investigating electrocatalysts for oxygen reduction reaction (ORR) is necessary to increase the performance of various energy storage and conversion systems. The development of ORR electrocatalysts that are noble-metal free, low cost, efficient and stable is very desirable as the key to realizing the commercialization of metal-air batteries and fuel cells, but it is still a significant challenge. Transition metal dichalcogenides (TMD) are widely known as electrocatalytic materials. The performance of these materials can be improved by chemical doping with transition metals, because doping affects the electronic structure, which is favorable to increasing the active sites of the edges. Moreover, bimetal oxides have encouraging results in electrocatalytic applications due to the different oxidation states and synergistic interaction between multiple metal species, and many studies are being conducted on them. The combination of these two materials (doped TMDs and bimetallic oxides) has produced superior results in electrocatalytic activity, but has rarely been investigated. In this work, an efficient ORR electrocatalyst consisting of Co₃V₂O₈ nanospheres and Cu-doped MoS₂ was simply synthesized by an inexpensive hydrothermal method in several steps. The Co₃V₂O₈/Cu-MoS₂ nanocomposite, with the benefit of porous structure, has an overpotential of 262 mV and Tafel slope of 63 mV dec⁻¹, indicating its excellent catalytic activity toward ORR. The oxygen reduction mechanism occurs through a four-electron transfer pathway for this catalyst. Also, the current density, with a loading of 0.424 mg cm⁻² on the rotating disc electrode (RDE), can reach 4.59 mA cm⁻², which is comparable to 10% Pt/C. The improved ORR performance is attributed to the increase of active sites and the synergistic effect between Mo and Cu in Cu-MoS₂, which led to the change of electronic structure and charge redistribution in MoS₂. Furthermore, the highly accessible surface of Co₃V₂O₈ nanospheres and their combination with Cu-MoS₂ cause significant ORR activity for the final catalyst.