A Novel Photocatalytic Integrated Carbon Capture and Utilization (ICCU) Approach for Conversion of CO2 to Methanol in Amine Solution

Abstract

Abstract Conventional CO2 utilization methods are often complex and costly. This is due to the requirement of capturing, purifying, storing, and transporting the CO2 feedstock prior to utilization. Recently, a new approach, namely Integrated Carbon Capture and Utilization (ICCU) has emerged, which allows the direct utilization of CO2 at the capture site such as an acid gas removal unit (AGRU). In this study, we introduce a novel ICCU method wherein CO2 captured in an amine-based solvent is directly converted into methanol via photocatalysis. A magnesium-doped titanium dioxide (Mg-TiO2) photocatalyst was synthesized via a one pot hydrothermal method. The synthesized photocatalyst was characterized using XRD, UV-Vis, BET, and XPS techniques. After 24 hours of UV-A photocatalysis, the Mg-TiO2 photocatalyst achieved a methanol yield of 31.49 μmol/gcat.h, which was 2.4 times higher than that of anatase TiO2 (12.94 μmol/gcat.h). Moreover, the Mg-TiO2 catalyst displayed excellent recyclability, maintaining its efficiency for up to 6 cycles of photocatalysis. This enhanced performance can be attributed to the presence of the Mg dopant, which improved CO2 adsorption and suppressed charge recombination rates. Furthermore, after 144 hours of photocatalysis, the amine solution exhibited minimal loss of alkalinity, indicating good retention of amine health. Notably, 8% of the loaded CO2 was stripped off from the amine after 144 hours, demonstrating that the photocatalysis system can serve as a 2-in-1 system, where CO2 was converted into methanol while simultaneously regenerating the amine's CO2 capturing capacity. This study presents the first report ICCU strategy employing photocatalysis.