High-Temperature Oxidation of Single Carbon Nanoparticles:Dependence on the Surface Structure and Probing Real-TimeStructural Evolution via Kinetics

O(2)oxidation and sublimation kinetics for >30 individual nano-particles (NPs) offive different feedstocks (graphite, graphene oxide, carbon black,diamond, and nano-onion) were measured using single-NP mass spectrometry attemperatures (TNP) in the 1100-2900 K range. It was found that oxidation,studied in the 1200-1600 K range, is highly sensitive to the NP surface structure,with etching efficiencies (EEO2) varying by up to 4 orders of magnitude, whereassublimation rates, significant only forTNP >=similar to 1700 K, varied by only a factor of similar to 3. Its sensitivity to the NP surface structure makes O2etching a good real-timestructure probe, which was used to follow the evolution of the NP surfacestructures over time as they were either etched or annealed at highTNP. All typesof carbon NPs were found to have initial EEO2values in the range near 10-3Da/O2collision, and all eventually evolved to becomeessentially inert to O2(EEO2<10-6Da/O2collision); however, the dependence of EEO2on time and mass loss was very different forNPs from different feedstocks. For example, diamond NPs evolved rapidly and monotonically toward inertness, and evolutionoccurred in both oxidizing and inert atmospheres. In contrast, graphite NPs evolved only under oxidizing conditions and wereetched with complex time dependence, with multiple waves of fast but non-monotonic etching separated by periods of near-inertness. Possible mechanisms to account for the complex etching behavior are proposed.

Automated summary

This study measured the oxidation and sublimation kinetics of individual nanoparticles from different feedstocks using single-nanoparticle mass spectrometry. The results showed that oxidation is highly sensitive to surface structure, while sublimation rates are influenced by temperature. All types of carbon nanoparticles eventually became inert to oxygen, but the evolution and time dependence varied for nanoparticles from different feedstocks.