Nitrogen Self-Doping Hierarchical Pore Biochar for Enhanced CO<sub>2</sub> Capture: Modulation of Pore Structure and Surface Properties
Wei Sun, Xudong Zheng, Biao Ji, Zihuai Xu, Sifan Bao, Zhouzhou Yang, Jinfeng Mei, Jian Rong, Zhongyu Li
Abstract
Negative emission technology aims to remove greenhouse gases such as CO 2 from the atmosphere, which is an important way to achieve efficient carbon reduction. The use of biochar materials as adsorbents can significantly reduce the cost while effectively capturing CO 2 . In this work, carp fish scales were used as biomass raw materials, a small amount of KOH was used as an activator to provide ionic active sites, and the activation ion K + was uniformly introduced into the material through a premixed hydrothermal reaction, followed by a single-step carbonization and activation process at a moderate temperature, along with an acid wash, to produce a N self-doping, layered-structured biochar with high porosity and uniform pore channels. A series of hierarchical biochars with dissimilar physicochemical properties were prepared by varying the carbonization temperature. Among them, the sample prepared at 700 °C (AF-700) has an ultrahigh specific surface area of 1371 m 2 g –1, a pore volume of 0.85 cm 3 g –1, and showed the highest adsorption performance of 3.34 mmol g –1 (0 °C, 1 bar). We also fitted the adsorption curves of the biochar using the Langmuir–Freundlich isotherm model and calculated the adsorption selectivity of the material for CO 2 (N 2 and Ar) with ideal adsorption solution theory. The results indicate that N self-doped hierarchical structure biochar exhibits high CO 2 adsorption efficiency and is composited in an economical and simple way, thus holding great potential for the large-scale production of efficient CO 2 adsorbents.