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<p>Biochar is a porous carbon material that can effectively remove NO<sub>x</sub> from flue gas. The influence of K element and active sites on the microscopic mechanism of NO<sub>2</sub> gas adsorption and reduction reaction remains elusive. Through density functional theory (DFT), two NO<sub>2</sub> molecules are selected on reasonable biochar models to calculate the reaction pathway. The reaction pathways involve the sequential adsorption of two NO<sub>2</sub> molecules at different active sites for reduction reaction, and desorption of two NO molecules and one CO<sub>2</sub> molecule. Through the energy barrier difference of the reaction path and interaction region indicator (IRI) analysis of important molecular structures, it was found that K atom promotes the adsorption reduction reaction in three reaction processes: the breakage of N–O bond, the desorption of NO molecule, and the dissociation of CO<sub>2</sub> molecule. Based on the different numbers of active sites in the four reactant models, it can be concluded that the promotion range of the K atom for the adsorption and reduction process of NO<sub>2</sub> molecules is 0.6157&#xa0;nm. Thermodynamic and kinetic analyses indicate that the addition of K enhances the upper limit and the maximum reaction rate of the reaction pathways. This study provides certain theoretical guidance for preparing biochar to regulate NO<sub>2</sub> emissions.</p> Graphical Abstract <p></p>

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Density functional theory study on the microscopic mechanism of NO2 adsorption and reduction by potassium-doped biochar: the key role of the active sites

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年4月1日

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  • Tong Hao,
  • Qian Zhou,
  • Jinyuan Jiang,
  • Haoyang Song,
  • Yiting Pan,
  • Dongni Shi

摘要

Biochar is a porous carbon material that can effectively remove NOx from flue gas. The influence of K element and active sites on the microscopic mechanism of NO2 gas adsorption and reduction reaction remains elusive. Through density functional theory (DFT), two NO2 molecules are selected on reasonable biochar models to calculate the reaction pathway. The reaction pathways involve the sequential adsorption of two NO2 molecules at different active sites for reduction reaction, and desorption of two NO molecules and one CO2 molecule. Through the energy barrier difference of the reaction path and interaction region indicator (IRI) analysis of important molecular structures, it was found that K atom promotes the adsorption reduction reaction in three reaction processes: the breakage of N–O bond, the desorption of NO molecule, and the dissociation of CO2 molecule. Based on the different numbers of active sites in the four reactant models, it can be concluded that the promotion range of the K atom for the adsorption and reduction process of NO2 molecules is 0.6157 nm. Thermodynamic and kinetic analyses indicate that the addition of K enhances the upper limit and the maximum reaction rate of the reaction pathways. This study provides certain theoretical guidance for preparing biochar to regulate NO2 emissions.

Graphical Abstract