Development of amine-functionalized cerium dioxide for direct air capture of CO₂: A chemical adsorption study

The direct capture of CO₂ from ambient air (Direct Air Capture, DAC) has emerged as a crucial technology for mitigating climate change and achieving carbon neutrality. In this study, cerium oxide (CeO₂) was functionalized with (3-aminopropyl)triethoxysilane (APTES) through a silanization reaction to enhance CO₂ adsorption performance. The APTES-modified CeO₂ adsorbents were systematically characterized using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) to confirm their structural and functional properties. The results demonstrated that APTES functionalization not only introduced amine groups capable of interacting with CO₂ but also induced the formation of oxygen vacancies through lattice distortion and redox interactions. CO₂ temperature-programmed desorption (CO₂-TPD) experiments revealed a significant enhancement in adsorption capacity after APTES modification, with the adsorption performance closely related to the presence of amine functional groups and oxygen vacancies. Importantly, APTES-functionalized CeO₂ exhibited improved stability during cyclic adsorption-desorption tests under pure CO₂ and 400ppm CO₂ conditions, outperforming conventional amine-modified adsorbents. These findings provide insights into the synergistic effects of amine functionalization and oxygen vacancies in DAC applications and highlight the potential of APTES-functionalized CeO₂ as an efficient, stable, and cost-effective CO₂ adsorbent.