Study on the mechanism of CO₂ adsorption by metal oxide coupled with pyrrole nitrogen biochar

In this study, density functional theory was used to study the influence mechanism of pyrroleaze-containing biochar (CN5) and its coupling of different metal oxides (ZnO, CaO, Na₂O) on the adsorption characteristics of CO₂. Calculating the adsorption capacity of CO₂ on different metal oxides coupled with pyrrole nitrogen-containing biochar (CN5@MO_x∶CN5@ZnO, CN5@CaO, CN5@Na₂O), and analyzing the difference in adsorption capacity combined with adsorption heat, it was found that CO₂ multi-layer adsorption occurred on the CN5@Na₂O surface, compared with CN5@ZnO and CN5@CaO, CO₂ adsorption heat and adsorption capacity on CN5@Na₂O were higher, reaching 6.11 mmol/g at 100 kPa and 20 ℃, with stronger interaction and more utilization of adsorption. The CN5@MO_x adsorption energy was further investigated, and the calculation results showed that the CN5@Na₂O adsorption energy for CO₂ was higher than that of CN5@CaO and CN5@ZnO, which was consistent with the adsorption capacity. The charge differential density and state density analysis were carried out, and the charge differential density showed that due to the participation of Na in Na₂O in adsorption, charge transfer occurred between O in CO₂, and the state density analysis showed that CO₂ was more stable adsorption on the CN5@Na₂O surface.