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Open AccessArticle

High Pressure Photoreduction of CO2: Effect of Catalyst Formulation, Hole Scavenger Addition and Operating Conditions

1
Dip. Chimica, Università degli Studi di Milano, INSTM Unit Milano-Università and CNR-ISTM, via C. Golgi, 19, I-20133 Milano, Italy
2
Dip. di Ingegneria Civile, Chimica e Ambientale, Università degli Studi di Genova and INSTM Unit Genova, via all’Opera Pia 15A, I-16100 Genoa, Italy
*
Authors to whom correspondence should be addressed.
Catalysts 2018, 8(10), 430; https://doi.org/10.3390/catal8100430
Received: 15 August 2018 / Revised: 27 September 2018 / Accepted: 28 September 2018 / Published: 30 September 2018
The photoreduction of CO2 is an intriguing process which allows the synthesis of fuels and chemicals. One of the limitations for CO2 photoreduction in the liquid phase is its low solubility in water. This point has been here addressed by designing a fully innovative pressurized photoreactor, allowing operation up to 20 bar and applied to improve the productivity of this very challenging process. The photoreduction of CO2 in the liquid phase was performed using commercial TiO2 (Evonink P25), TiO2 obtained by flame spray pyrolysis (FSP) and gold doped P25 (0.2 wt% Au-P25) in the presence of Na2SO3 as hole scavenger (HS). The different reaction parameters (catalyst concentration, pH and amount of HS) have been addressed. The products in liquid phase were mainly formic acid and formaldehyde. Moreover, for longer reaction time and with total consumption of HS, gas phase products formed (H2 and CO) after accumulation of significant number of organic compounds in the liquid phase, due to their consecutive photoreforming. Enhanced CO2 solubility in water was achieved by adding a base (pH = 12–14). In basic environment, CO2 formed carbonates which further reduced to formaldehyde and formic acid and consequently formed CO/CO2 + H2 in the gas phase through photoreforming. The deposition of small Au nanoparticles (3–5 nm) (NPs) onto TiO2 was found to quantitatively influence the products distribution and increase the selectivity towards gas phase products. Significant energy storage in form of different products has been achieved with respect to literature results. View Full-Text
Keywords: CO2 reduction; photoreduction; Titania; photocatalysis; high pressure photocatalysis CO2 reduction; photoreduction; Titania; photocatalysis; high pressure photocatalysis
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Bahadori, E.; Tripodi, A.; Villa, A.; Pirola, C.; Prati, L.; Ramis, G.; Rossetti, I. High Pressure Photoreduction of CO2: Effect of Catalyst Formulation, Hole Scavenger Addition and Operating Conditions. Catalysts 2018, 8, 430.

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