Vacuum-Dried and Intrinsic Photothermal Phenolic Carbon Aerogel from Coal Tar Rich in Polycyclic Aromatics for Efficient Solar Steam Generation

Solar steam generation has been proven to be an efficient way for obtaining clean water from seawater or polluted water with solar energy as the only energy input. Due to the high porosity and light absorption, tunable micro-nano structure, and excellent thermal insulation, carbon aerogels as photothermal materials have attracted much attention. However, requirements of freeze drying and additional light absorbers as well as low strength restrict the large-scale utilization of carbon aerogels. Herein, self floating and low-cost coal tar-based phenolic carbon aerogels (CPCAs) were fabricated using a facile method, that is, polymerization/gelation, vacuum drying, and carbonization. CPCAs with comparable light absorption (96.6%) to carbon nanotube can be used as intrinsic photothermal materials owing to the existence of considerable polycyclic aromatics in coal tar. In addition, CPCAs possess hierarchical porous architectures and abundant polar functional groups, delivering fast water transportation. Moreover, the latent heat is obviously reduced due to the regulation of the water state. Therefore, the evaporation rate can reach up to 2.23 kg m-2 h-1 with an energy efficiency of 92.5% under 1 sun employing a CPCA as a photothermal material. Additionally, CPCAs with high strength (more than 4 MPa under 90% compressive strain) have versatile applications in seawater desalination and industrial wastewater for long-term stability. The excellent performance of CPCAs was tentatively revealed by density functional theory and COMSOL calculation.