Wei, Kaiying, et al. Journal of Energy Storage 51 (2022): 104342.
Preparation of oxygen and nitrogen co-doped porous carbon is a significant pathway to enhance the performance of carbon materials and broaden their application spectrum. Since most methods for preparing alginate-derived porous carbon require chemical activators and acid washing, synthesizing oxygen and nitrogen co-doped porous carbon from alginate salts using a simple and low-cost approach remains a substantial challenge. In this study, a high-surface-area oxygen and nitrogen co-doped porous carbon was successfully prepared by carbonizing ammonium alginate (AA) aerogels followed by air activation.
Synthesis Method of Porous Carbon
Initially, 1.0 g of AA powder was dissolved in different volumes of deionized water (20, 40, 60, 80, and 100 mL) under magnetic stirring to obtain a viscous solution. The solution was then freeze-dried to produce AA aerogels labeled as AA-x, where x denotes the volume of deionized water. Subsequently, the AA aerogels were carbonized in a tubular furnace under N2 atmosphere at 850 °C for 4 hours (with a heating rate of 5 °C min-1). The resulting porous carbons were designated as AA-Cx. To further modify the porous structure of the porous carbons, an air activation treatment was conducted in a muffle furnace at 400 °C for 2 hours (with a heating rate of 5 °C min-1). The final products were denoted as AA-Cx400. For comparative purposes, a carbon material labeled as AA-C0 was obtained by direct pyrolysis of AA powder in a tubular furnace under N2 atmosphere at 850 °C for 4 hours.
Chen, Hong-Bing, et al. Polymer 53.25 (2012): 5825-5831.
Low-flammability foamed materials based on bio-based and renewable ammonium alginate and sodium montmorillonite (Na+-MMT) clay were prepared using a simple and environmentally friendly freeze-drying process (with water as the solvent).
To produce aerogels containing 5 wt% alginate and 5 wt% clay, 5 grams of Na+-MMT were mixed with 100 mL of DI water using a high-speed setting of a small laboratory mixer for 1 minute, to obtain a 5 wt% clay aqueous suspension. Subsequently, 5 grams of ammonium alginate powder were slowly added to the clay gel under continuous stirring to obtain an ammonium alginate/clay gel containing 5 wt% ammonium alginate and 5 wt% clay. The resulting mixture was poured into polystyrene vials and immediately frozen in a dry ice/ethanol bath (~ -80 °C). The frozen samples were dried in a freeze-dryer under high vacuum to sublimate the ice. The freeze-drying process took 3-4 days, which may be longer than necessary but ensures the completion of the process.
Ji, Linken, et al. Journal of Power Sources 573 (2023): 232933.
Structures with ion migration channels and continuous conductive networks are critical for the high-rate performance of activated carbon. Phenolic resin and ammonium alginate composite-derived carbon was prepared using sol-gel, carbonization, and KOH activation methods.
In this study, a small amount of ammonium alginate (AA) was used as a template to prepare phenolic resin-derived hierarchical porous carbon with a 3D interconnected coral-like structure. First, molten phenolic resin was thoroughly mixed with an ammonium alginate solution to form a phenolic resin/ammonium alginate (PF-AA) composite gel. The gel was then cross-linked with Ca2+ to form hydrogel particles. After drying, the hydrogel particles underwent pre-oxidation, carbonization, and chemical activation with KOH. By adjusting the concentration of ammonium alginate, the 3D morphology and structure of the coral-like carbon material were altered.
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