A model of reaction field in gas-injected arc-in-water method to synthesize single-walled carbon nanohorns: Influence of water temperature

摘要

The method to synthesize single-walled carbon nanohorns (SWCNHs) using gas-injected arc in water (GI-AIW) has been experimentally studied. GI-AIW is known as one of the cost-effective methods to obtain SWCNHs. It was revealed that the yield of SWCNHs significantly decreases with the increase in water temperature although the purity of SWCNHs is not dependent on the temperature change. Then the model of relevant reactions in the GI-AIW system was proposed by accounting the emission of carbon vapor, formation of SWCNHs, and diffusion of water vapor in three zones inside the cathode hole (arc plasma zone, quenching zone, and downstream zone). The side reaction between H2O and C produces H2 gas and consumes a certain amount of carbon vapor, resulting in the hindered SWCNH formation. Moreover the observation of the optical spectra emitting from the arc plasma zone strongly supported that the H2 generating reaction does not occur at arc plasma zone since N2 flow can purge H2O out. The model proposed in this study can precisely explain the correlation between H2 gas production and water temperature.