Novel Multiphase CO2 Photocatalysis System Using N-TiO2/CNCs and CO2 Nanobubble.

In this study, a novel CO₂ photocatalysis system was developed by modifying TiO₂ as a photocatalyst and introducing CO₂ nanobubble to the system. TiO₂ photocatalyst is modified by adding CNCs as support to increase the surface area and adding nitrogen doping to reduce the band gap and minimize electron-hole recombination. CO₂ nanobubbles are introduced to increase the surface area between the CO₂ gas and liquid phases to reduce mass transfer limitations. Thus, the amount of CO₂ in the liquid phase increases. Nanobubbles have been successfully generated by the hydrodynamic cavitation method, which produces bubbles with two size clusters, namely 200-400 nm, which belong to nanobubbles, and 2-10 um, which belong to microbubbles. The TiO₂ has an anatase phase and crystallite size of 20.90 nm for TiO₂/CNCs and 19.20 nm for N-TiO₂/CNCs. The activity test without nitrogen doping produced a methanol product of 0.77 mmol/g catalyst, which shows that this multiphase CO₂ photocatalytic system is feasible for CO₂ photocatalytic reactions. The addition of nitrogen doping succeeded in reducing the band gap from 3.20 eV to 3.10 eV and increasing the methanol yield. The photocatalysis activity test with N-doped TiO₂/CNCs resulted in a higher methanol yield, which is 1.13 mmol/g catalyst under UV-C irradiation for 6 hours. [ABSTRACT FROM AUTHOR]