Self-template mechanism of “selective silicon dissolution” for the construction of functional rice husk biochar

The global greenhouse effect is serious, and many countries have reached a consensus on carbon neutrality. The high-value utilization of agricultural waste is of great significance for carbon emission reduction, while the use of agricultural waste to prepare biochar products is containing lots of application prospects. Rice husk is with high content of carbon and reticulated silica skeleton structure, which could be the “self-template” for construction of functional rice husk biochar. In this paper, high-performance rice husk-derived biochar is prepared from rice husk with KOH or K2CO3 as the “selective silicon dissolution” agent and activator, namely “one-step silicon-dissolving” and “selective two-step silicon-dissolving” methods, respectively. The results show that K2CO3 as a silicon dissolution only works at high temperatures, while at 900 °C biochar could be with a specific surface area of 1764.66 m2/g and without orderly terraced pore structure. Rice husk-derived biochar obtains a surface area of 3011.06 m2/g and a layered pore structure from “KOH selective two-step silicon-dissolving”, which is more favorable to the maintenance of microporous and ultra-microporous structures. It provides a theoretical basis and new idea for the construction of functional rice husk-derived biochar.