Enhanced Photothermal Effect in Ultralow-Density Carbon Aerogels with Microporous Structures for Facile Optical Ignition Applications

The exact mechanism responsible for the phenomenon known as photoignition with an enhanced photothermal effect in high-surface-area carbon with the addition of a metal catalyst is an open issue. Here, we report the first successful flash ignition of a pure carbon material in ambient air microporous carbon aerogels (CAs) with ultralow density and high surface area. Under flash exposure, the CAs show a strong local heat confinement effect near microporous structures (0.6-2 nm), and the graphite crystallite structures existing in single carbon nanoparticles (∼15 nm) are damaged. The local heat confinement effects are mainly derived from the low gaseous thermal conductivity in micropores and low solid thermal conductivity in low-density CAs. In addition, the limiting effects of the microporous structure on the vibration amplitude of free-state electrons in low-density CAs result in a dramatic increase in optical absorption. Numerical simulations of unsteady temperature fields of CAs with different densities a...