CO2 to Liquid Fuels: Photocatalytic Conversion in a Continuous Membrane Reactor

The photocatalytic reduction of CO2 into value-added chemicals using sunlight is a promising approach to promote energy-bearing products, mitigating the adverse effects of anthropogenic CO2 emissions. In this work, exfoliated C3N4 was incorporated into Nafion matrix and used in a continuous photocatalytic reactor for converting CO2 into liquid fuels. Comprehensive structural and morphological diffuse reflectance spectroscopy (DRS), FT-IR, ATR-IR, and SEM measurements were performed for C3N4-loaded Nafion membrane and then compared with those of a Nafion membrane without any catalyst. The synergic effect of C3N4 organic catalyst embedded in a Nafion dense matrix and a continuous operating mode of the photoreactor was successfully accomplished for the first time, as yet absent in the literature, analyzing the reactor performance as a function of key parameters such as contact time and H2O/CO2 feed molar ratio. The reactor performance was analyzed under UV-vis light in terms of productivity, selectivity, and converted carbon. Alcohol (MeOH + EtOH) production was 32.8 μmol gcatalyst-1 h-1 corresponding to 47.6 μmol gcatalyst-1 h-1 of total converted carbon per gram of catalyst at the best operating conditions. So far, this value results as higher than most of the literature values reported up to date. Moreover, the membrane reactor converted at least 10 times more carbon than the batch system, as a result of the catalyst embedding in a Nafion matrix.