Zhiyuan Liu,Fan Yang,Tingting Zhai,Jianwei Yu,Chunmiao Wang,Zhengang Liu,Zhixue Liu,Yingxin Gao,Min Yang
Activated carbon (AC) adsorption is a practical process for the removal of perfluorooctanoic acid (PFOA) in aquatic environments, but the relationship between its pore structure and adsorption performance is not well understood. In this study, the KOH-activated carbons (KACs) with different tailored pore structures were prepared, and presented a 2.61-fold higher adsorption capacity and a 2.21-fold higher adsorption rate than the raw AC. An in situ characterization method and a modified adsorption model were introduced to investigate the impact of pore size, which demonstrated that the ultra-micropores (<1.2 nm) and small mesopores (2.0–3.0 nm) contributed significantly to the adsorption of PFOA, with the highest mean contribution factor ( k ) of 0.45 and the second highest of 0.39, respectively. Molecular dynamics simulations revealed that PFOA molecules tend to attach to the pore walls at various pore sizes. The adsorption of PFOA in the ultra-micropores was dominated by enhanced interactions due to the overlapping potentials of the bilateral pore walls (maximum of −567.32 Kcal·mol −1 ) and hydrophobic interactions. PFOA micelles or hemi-micelles could be formed in the small mesopores, allowing them to function as both the molecule transportation channels and strong adsorption sites. This study would guide the development of activated carbon tailored for the selective adsorption of PFOA from water.
The charge storage processes of heteroatom–doped carbon materials with small mesopores (2 ∼ 4 nm) occur by both double–layer capacitance and pseudocapacitance. Yet, owing to the ambiguous understanding on how electrolyte ions affect their capacitive behavior, it is hard to form a unified design principle to guide the selection of electrolytes, with the purpose of boosting supercapacitors. Herein, an all–in–one carbon electrode with abundant oxygen–containing groups and an average pore size of 2.5 nm was used as a model electrode to investigate the capacitive behavior of this class of carbon materials. It is found that in ammonium acetate aqueous electrolyte the model electrode shows a significantly increased specific capacitance, and an ion exchange mechanism dominates charge storage. Acetate anions with a larger ion radius can better match small mesopores in size and thus increase double–layer capacitance due to the suppression of the “over–screening” effect in the first adsorbed layer on carbon surfaces. Besides, ammonium cations forms hydrogen bonds with oxygen–containing groups maximizing the Gibbs free energy change related to faradic reactions, which enhances pseudocapacitance. Our work elaborated the effect of electrolyte ions on the capacitance of heteroatom–doped carbon materials with small mesopores and provided new understanding on designing high–performance aqueous supercapacitors.
危险品化学品经营许可证（带存储）