(513ek) Efficient Microwave-Assisted Annealing of Reduced Graphene Oxides in an up-Flow Reactor

Abundant defects present in graphene-based materials provide opportunities to anchor atomically dispersed metals with a high loading [1]. Tailoring the distribution and concentration of defects in graphene-based materials is anticipated to offer further ability to tailor properties of supported metal species. Our previous work suggests that low-density reduced graphene oxide (rGO) foams bearing macroscopic void spaces are desirable for efficient annealing [2]. In addition, the literature data indicate that a strong electric field is generated between two carbon particles when the distance between them is in the μm range [3]. Thus, we hypothesized that the efficiency of the conversion of MW energy to thermal energy depends on the macroscopic distance between adjacent carbon surfaces. Although annealing of low-density rGO foams proceeds efficiently, such materials pose a challenge in sample handling. In this work, we demonstrate that MW treatment of high-density rGO particles in an up-flow reactor formed a low-density sample bed, rapidly heated the sample bed to high temperatures, and consequently enables efficient annealing. We provide the evidence for the efficient annealing in an up-flow reactor relative to that in a down-flow reactor through characterization using Raman spectroscopy, X-ray photoelectron spectroscopy, elemental analysis, and temperature-programmed oxidation.

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2. Ogino, I., Fukazawa, G., Kamatari, S., Iwamura, S., Mukai, S.R. J. Energy Chem. 27, 1468 (2018).
3. Horikoshi, S., Osawa, A., Sakamoto, S., Serpone, N. Appl. Catal., A 460, 52 (2013).