O2-oxidation of individual graphite and graphene nanoparticles in the 1200-2200 K range: Particle-to-particle variations and the evolution of the reaction rates and optical properties

The kinetics for O-2 oxidation of individual graphite and graphene platelet nanoparticles (NPs) were studied as a function of temperature (1200-2200 K) at varying oxygen partial pressures, using a single nanoparticle mass spectrometry method. NP temperature (T-NP) was measured by measuring the NP thermal emission spectra during the kinetics studies. The initial oxidation efficiency is found to peak in the 1200-1500 K range, dropping by an order of magnitude as T-NP was increased above 2000 K. There were large NP-to-NP variations in the oxidation rates, attributed to variations in the NP surface structure. In addition, the oxidation efficiencies evolved, non-monotonically, as the NPs reacted, decreasing by factors of between 10 and 300. This evolution of reactivity is attributed to changes in the NP surface structure due to the combination of oxidation and annealing. The optical properties, including wavelength dependence of the emissivity and the absorption cross section for the 532 nm heating laser, also tended to evolve as the NPs oxidized, but differently for each individual NP, presumably reflecting differences in the initial structures and their evolution. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The kinetics of O-2 oxidation for individual graphite and graphene platelet nanoparticles were studied at different temperatures and oxygen partial pressures. The initial oxidation efficiency peaked in the 1200-1500 K range and decreased as temperature increased above 2000 K. Variations in oxidation rates and efficiencies were attributed to differences in the nanoparticles' surface structures.