Solar-driven photothermal desorption of CO₂ from PEI-infused silica gel

In light of the pressing global demand for effective carbon capture technologies to combat climate change, it is crucial to explore carbon dioxide (CO 2 ) adsorbent regeneration strategies that can be scaled and driven by renewables. Photothermal regeneration emerges as a viable approach for enhancing the efficiency and scalability of CO 2 capture systems. This study conducts a systematic investigation into laboratory-scale photothermal regeneration applied to polyethyleneimine (PEI)-infused silica gel. We evaluated three regeneration techniques: traditional thermal heating, direct illumination, and indirect photothermal heating, wherein solar-simulated light was incident onto an adsorbent bed coated with solar-selective paint. The results show that indirect photothermal regeneration substantially improves desorption kinetics, shortening the desorption time to ∼3058 s (with a desorption capacity of ∼0.28 mmol/g), compared to ∼3892 s (for traditional thermal heating, with a desorption capacity of ∼0.23 mmol/g) and ∼ 6025 s (with a desorption capacity of ∼0.28 mmol/g) for the direct illumination configuration. Surface analyses validated that indirect photothermal heating preserves the sorbent's integrity and composition, whereas direct illumination leads to discoloration and localized degradation. This laboratory-scale investigation presents the first geometrically matched comparative analysis of thermal, direct, and indirect photothermal regeneration modalities within a PEI–silica fixed-bed system. Additionally, it introduces novel thermal-uniformity metrics that provide a quantitative explanation for the approximately 22 % reduction in desorption time observed in the indirect regeneration mode. Furthermore, this work highlights the potential integration of PEI-infused silica gel systems with flat-plate solar collectors, supporting the development of fully renewable, solar-powered carbon capture technologies. • PEI-infiltrated CO 2 adsorbents regenerated using solar simulated radiation. • Comparison of direct and indirect photothermal regeneration of CO 2 adsorbents • Indirect heating improves heating uniformity and reduces adsorbent degradation.