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

Abstract

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 400 ppm 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.