ABSTRACT
Polyimide (PI) aerogel has surfaced in research and development as a result of its heat resistance, flame retardancy, and low dielectric constant. However, it is still a challenge to reduce the thermal conductivity while improving its mechanical strength and retaining hydrophobicity. Herein, the PI/thermoplastic polyurethane (TPU) composite aerogel was synthesized by coupling TPU with PI via a novel method of chemical imidization combined with freeze-drying technology. With this technique, PI aerogel with excellent comprehensive performance is produced. Interestingly, the volume shrinkage of the composite aerogel decreased from 24.14 to 5.47%, which leads to low density (0.095 g/cm3) and elevated porosity (92.4%). In addition, strong mechanical strength (1.29 MPa) and high hydrophobicity (123.6°) were achieved. More importantly, PI/TPU composite aerogel demonstrated a low thermal conductivity of 29.51 mW m-1 K-1 at ambient temperature. Therefore, PI/TPU composite aerogel can be a promising material for hydrophobic and thermal insulation applications.
ABSTRACT
Carbon aerogel (CA) based materials have multiple advantages, including high porosity, tunable molecular structures, and environmental compatibility. Increasing interest, which has focused on CAs as electrocatalysts for sustainable applications including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and CO2 reduction reaction (CO2RR) has recently been raised. However, a systematic review covering the most recent progress to boost CA-based electrocatalysts for ORR/OER/HER/CO2RR is now absent. To eliminate the gap, this critical review provides a timely and comprehensive summarization of the applications, synthesis methods, and principles. Furthermore, prospects for emerging synthesis, screening, and construction methods are outlined.
