Integrating Mixed Metallic Selenides/Nitrogen-Doped Carbon Heterostructures in One-Dimensional Carbon Fibers for Efficient Oxygen Reduction Electrocatalysis

Abstract

Developing electrocatalysts for oxygen reduction reaction (ORR) with superior catalytic activity, long-period stability, and low price is extremely desirable but full of challenges. Hybrid nitrogen-doped carbon nanofibers encapsulated with mixed metallic selenides of ZnSe and CoSe₂ (assigned as Co₁–ₓZnₓSe, x represents the molar ratio of Zn/Co) nanoparticles are successfully prepared and denoted as Co₁–ₓZnₓSe@NCF-y (y represents the carbonization temperature). By controlling the ratio of Zn to Co and the carbonization temperature, the obtained Co₀.₆₂Zn₀.₃₈Se@NCF-800 fibers with a large specific surface area (385 m² g–¹) and a high content of nitrogen species (8.39 wt %) exhibit outstanding ORR electrocatalytic activity with a half-wave potential of 0.83 V (vs reversible hydrogen electrode, RHE), a limiting current density of 5.05 mA cm–², an excellent catalytic stability, and methanol tolerance. The superior ORR catalytic performances can be first explained by the hierarchical nanoparticles-in-fiber structure, which helps suppress the particle agglomeration, increase the structural stability, and promote the mass/electron transportation. The mixed metallic selenides are also believed to facilitate the electronic conductivity through redistribution of electrons from the metallic selenides to the nitrogen-doped carbon layers. Meanwhile, the highly nitrogen-doped carbon layers act as supports for metallic selenides to exhibit good electrocatalytic performances and electrochemical stability.