دانلود رایگان مقاله عاملدار کردن آهن از نانو ورقه گرافن توسط پلاسما حرارتی

ABSTRACT

 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.

4. Conclusion

Non-noble metal catalysts for the oxygen reduction reaction have been completely produced by an original method where the carbon matrix is grown and the iron functionalization step is performed in the same thermal plasma reactor by changing the feeding gas conditions. An improvement of the electrocatalytic activity has been noticed for different conditions, depending on the iron source employed. Even if the performances of the catalysts are lower than platinum based catalysts,this study represents the proof of concept on the generation of non-noble metal catalysts from nucleation to various functionalization steps within a thermal plasma reactor in a single batch process. The improvement ofthe electrocatalytic activity is currently under ongoing research to determine the role of the iron oxide, as well as the effective presence of atomic iron catalytic sites. Also, improvement of the iron functionalization step itself is still studied. Iron functionalization of GNFs in hotter areas of the thermal plasma reactor is considered to increase the chances of a direct contact between the GNFs and iron vapour. The addition of a higher amount of nitrogen functionalities would be another way to improve the electrocatalytic activity of the catalysts.