Preparation And Studies On Phenol-Formaldehyde Carbon Aerogels Corporated With Resorcinol

Carbon aerogels (CAs) are a new type of nano-sized porous carbon materials with many outstanding properties such as electrical conductibility, thermal conductivity and porosity, which make it can be used as an ideal electrode material in supercapacitor and lithium cell, as well as in some other aspects such as catalyst supports, adsorbents, chromatography fillers and hydrogen storage materials. In recent more than 20 years since its birth, CAs have got a worldwide attention and a great deal of researches and studies have been carried out to the improvement of CAs in many aspects, such as the selection of raw materials, the optimization of preparation process and the specific applications.CAs are prepared traditionally using resorcinol and formaldehyde as raw materials. However, the high cost of resorcinol reduces their market competitiveness seriously. To change this situation, in our process, the cheapest phenols, i.e. phenol, was chosen and CAs were successfully obtained via the two-step polycondensation method of phenol and formaldehyde in an aqueous alkaline solution with a small amount of resorcinol used as nucleating and cross-linking agent.In this paper, the effects of the different dosage of resorcinol and catalyst on gel appearance, bulk density, drying and carbonization shrinkage as well as the microstructure of the resultant organic and carbon aerogels were studied and their surface chemical properties were characterized by Infrared Analysis (IR). Morphology and microstructure of CAs were investigated by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and N2 adsorption-desorption measurement. The experimental results showed that the prepared CAs have a three-dimensional network, consisting of interconnected pearl-like particles with abundance of micropores, controllable amount of mesopores and macropores. Besides, the addition of nucleating and cross-linking agent, i.e. resorcinol, can dramatically decrease the required amount of catalyst to form transparent organic gels. Furthermore, with different additive amounts of resorcinol, the porous microstructure of CAs can be tuned accordingly.Their electrochemical behaviors of the CAs samples as electrode material in electric double-layer capacitors (EDLCs) were characterized by constant current charge-discharge tests under different current densities. Due to the presence of the advisable amount of macropores, the specific capacitance of the CAs with the addition of resorcinol slightly decreased from 177.1F/g to 166.5F/g when increasing the current density from 1 mAcm-2 to 50mAcm-2, compared to the larger reduction of the CAs without the addition of resorcinol from 146.2F/g to 125.1F/g, indicating that the as-prepared samples have a high-rate charge-discharge performance.