Iron functionalization on graphene nanoflakes using thermal plasma for catalyst applications

[Display omitted] •A new technique produces non-noble metal catalysts for oxygen reduction reaction using a thermal plasma batch process.•The structure and composition of the catalysts were analysed to link experimental conditions andelectrocatalytic activity.•The performances of the resulting catalysts are improved when iron is added to the nitrogen functionalized graphene nanoflakes. Graphene nanoflakes (GNFs), a stack of 5–20 layers of graphene sheets, are generated here using methane decomposition in a thermal plasma followed by homogeneous nucleation of the 2-dimensional structures in the gas stream. The GNFs are functionalized with nitrogen and iron to improve their electrocatalytic activity. The iron functionalization step is carried out as a post-processing step within the same thermal plasma reactor used to grow the nanoparticles. Two different iron precursors are tested in the reactor, iron powder and iron (II) acetate solution. The iron source carried by a nitrogen flow is injected in the argon plasma, and parameters such as the plasma power, pressure, and the exposure time during functionalization are optimized for enhanced catalyst activity. Structure and composition of the resulting catalysts are characterized, and their electrocatalytic performances in terms of onset potential, half wave potential and current density show an increase compared to the non-functionalized GNFs. This study proves the ability to entirely produce a pure and highly crystalline graphene-based non-noble metal catalyst using a thermal plasma single batch process with simple precursors such as methane and nitrogen gas, and an iron powder or iron acetate solution.