Fig. 3: Characterization and performance of the CO2U unit.
From: Direct air capture of CO2 for solar fuel production in flow
a, HAADF-STEM image and the relevant EDS maps (O, Si, Ti, N) of the composite. b, The effect of different alcohol electron donors on H2 and CO formation. Reactions were carried out in batch with 100 mg of CO2U composite (nSiO2|TiO2|CotpyP) and 0.15 ml of electron donor under 1 sun (100 mW cm–2, AM 1.5G) for 20 h. c, The effect of N2 versus CO2 carrier gas on product formation in fixed-bed flow setup. Reactions were performed with 250 mg of CO2U composite, moistened with 0.50 ml EG, under 1-sun illumination at a carrier gas flow rate of 1 ml min−1. d, The effect of different support materials on performance under similar conditions. e, An image of the parabolic trough reflector used for light concentration with the mounted tubular fixed-bed reactor. f, The effect of increasing solar intensity (around 3 suns) via reflector on CO formation when using γ-Al2O3|TiO2|CotpyP as the CO2U composite. g, The effect of temperature regulation on CO and H2 formation. The 43 oC and 56 oC reactions were performed without temperature regulation (elevated temperatures due to solar thermal heating), whereas in the 25 oC reaction, temperature was kept steady using a water jacket. h, Product evolution with time under 3-sun illumination when temperature was kept steady at 25 °C. For b–d and f–h, data are presented as the average of two independent runs and the individual data points are shown in hollow circles.
