Efficient solar-driven carbon dioxide capture system for greenhouse using graphene-contained deep eutectic solvents

As photosynthesis progresses, the concentration of CO2 within greenhouses rapidly declines, significantly impairing crop growth. In light of the prevailing limitations associated with complex systems, high energy consumption, and safety concerns related to existing CO2 supplementation methods, a novel “solar-driven CO2 capture system” was proposed for the first time in current work, in which high photothermal conversion materials were incorporated into the deep eutectic solvents (DES). This nanofluid system aims to elevate the system's temperature, facilitating the desorption process and promoting the CO2 absorption–desorption cycle. The graphene nanofluid (GNF) prepared with varying mass fractions of reduced graphene oxide (RGO) can raise CO2 absorption capacity. The results indicate that the CO2 absorption capacity has improved from 0.286 g/g to 0.399 g/g, which can be attributed to abundant adsorption sites provided by the surface of RGO for capturing CO2. Furthermore, the addition of RGO improves the photothermal conversion performance of DES. Maximum photothermal conversion efficiency of 94.3 % and a maximum temperature of 75.9℃ have been achieved for DES-500 (with the addition of 500 ppm RGO in DES) under the irradiation of 1000 W/m2; while pure DES presents 32.7 % and 54.7℃, respectively. Notably, GNF also exhibits excellent recyclability and can effectively regulate CO2 concentration within the greenhouse, ensuring normal growth and development of crops.