Three dimensional nanocomposite of reduced graphene oxide and hexagonal boron nitride as an efficient metal-free catalyst for oxygen electroreduction

Abstract

The present work demonstrates a simple and inexpensive method for the synthesis of a reduced graphene oxide/boron nitride (rGO/BN) nanocomposite using a one step hydrothermal method followed by annealing at high temperature. The structural analysis confirms the formation of a homogeneous composite with coalescence of the graphitic layers of reduced graphene oxide and hexagonal boron nitride (h-BN), making an ideal situation for better oxygen adsorption followed by electroreduction. The morphology study also clearly indicates a uniform distribution of boron nitride particles at both sides of the stratified graphene oxide. Interestingly, the electrochemical study implies that the rGO/BN nanocomposite shows a substantially higher oxygen reduction reaction (ORR) activity with a single step nearly 4-electron transfer pathway and an improved onset potential of ∼0.8 V versus RHE in alkaline conditions. Though the onset potential is inferior to Pt based catalysts, it is much superior to previously reported carbon or h-BN based electrocatalysts. However, the present rGO/BN nanocomposite catalysts show higher stability than commercial Pt/C catalysts even after 10 000 cycles, and hence it could be a first report of ORR by metal-free h-BN based materials. Additionally, this composite catalyst does not have any methanol oxidation reactions that nullify the issues due to the fuel cross-over effect in direct methanol fuel cells.