CO₂ capture performance of ZrO₂-doped Na₂CO₃/γ-Al₂O₃ adsorbent

Sodium-based adsorbents (Na₂CO₃/γ-Al₂O₃) exhibit significant potential for commercial utilization in CO₂ capture. Nevertheless, the requirement for high desorption temperatures poses challenges in terms of the high-quality heat needed for desorption. This study integrated ZrO₂ doping into a sodium-based adsorbent to enhance its CO₂ capture performance and lower its desorption temperature. The research investigated the CO₂ adsorption capacity, reaction rate, and desorption characteristics of the ZrO₂-doped Na₂CO₃/γ-Al₂O₃ adsorbents in detail. Additionally, the catalytic mechanism of ZrO₂ was elucidated through Density Functional Theory calculations. The results showed that ZrO₂ doping increased the adsorption rate and capacity of the adsorbent and reduced the desorption energy consumption. Desorption reaction activation energy reduced to 44.8 kJ/mol. The adsorbent doped with 3 wt.% ZrO₂ demonstrated the highest adsorption capacity and rate under optimal conditions, with a reaction temperature of 45 ℃, an adsorption capacity of 1.66 mmol/g, and a carbon conversion rate of 80.2 %. ZrO₂ acted as a catalyst, enhancing CO₂ and H₂O adsorption, and facilitated CO₂ desorption in the sodium-based adsorbent by forming [ZrO(OH)]⁺ and OH^- through H₂O adsorption activation. The lower energy barrier (0.17 eV) for the dissociative adsorption pathway of H₂O molecules on the ZrO₂ surface further supported the role of ZrO₂ in enhancing the overall adsorption performance of the adsorbent in the carbon capture process. Ultimately, the ZrO₂-doped Na₂CO₃/γ-Al₂O₃ adsorbent was identified as having low desorption energy consumption, high adsorption capacity, and rate, offering potential cost reductions in CO₂ capture and representing a promising adsorbent for this application.