Facile synthesis of electrospun MFe2O4 (M = Co, Ni, Cu, Mn) spinel nanofibers with excellent electrocatalytic properties for oxygen evolution and hydrogen peroxide reduction

Abstract

Designing and preparing porous transition metal ferrites without using any template, shape-directing agent, and surfactant is a challenge. Herein, heterojunction MFe₂O₄ (M = Co, Ni, Cu, Mn) nanofiber (NF) based films with three-dimensional configurations were synthesized by electrospinning and the subsequent thermal treatment processes. Characterization results indeed show the 3D net-like textural structures of the electrospun spinel-type MFe₂O₄ NFs. In particular, the resulting MFe₂O₄ NFs have lengths up to several dozens of micrometers with an average diameter size of about 150 nm and possess abundant micro/meso/macropores on both the surface and within the films. The hierarchically porous structures and high surface areas of these MFe₂O₄ NFs (for example, the CoFe₂O₄ NFs possess a larger BET specific surface area (61.48 m² g⁻¹) than those of the CoFe₂O₄ NPs (5.93 m² g⁻¹)) can afford accessible transport channels for effectively decreasing the mass transport resistances, enhancing the electrical conductivity, and increasing the density and reactivity of the exposed catalytic active sites. All these advantages will be responsible for the better electrocatalytic performances of these MFe₂O₄ NFs compared with their structural isomers (i.e. the MFe₂O₄ NPs) for the oxygen evolution reaction (OER) and H₂O₂ reduction in alkaline solution. Meanwhile, both the OER and H₂O₂ reduction catalytic activities for these MFe₂O₄ NFs obey the order of CoFe₂O₄ NFs > CuFe₂O₄ NFs > NiFe₂O₄ NFs > MnFe₂O₄ NFs > Fe₂O₃ NFs. The CoFe₂O₄ NFs represent a new class of highly efficient non-noble-metal catalysts for both OER and H₂O₂ reduction/detection in alkaline media.