Photocatalytic hydrogenation of CO2 reaction use visible light near ambient temperature and pressure
Date Issued
2015
Date
2015
Author(s)
Chen, Chun-Ying
Abstract
Global warming and energy crisis are our motivation to reduce CO2 and develop renewable energy. However, the reduction of carbon dioxide by photocatalyst is still low efficient for converting carbon dioxide into useful chemicals (hydrocarbons) by sunlight. The objective is to study the enhancement reduction of CO2 with H2. Various partial pressures of H2 was added and expected to maximize the CO2 photo hydrogenation under an optimal H2 pressure. After the optimal photo hydrogenation of CO2 was found, the final goal was that the reaction was performed by the combination of the water-splitting H2 and CO2 photoreduction. Thus the overall CO2 reduction can be significantly increased. In this study, the efficient Pt/CuAlGaO4 was used as CO2 reduction catalyst. The CO2 photo hydrogenation was carried out in three different reactor, gas reactor, liquid reactor and gas-liquid reactor, respectively. The gas-liquid reactor gave the highest yields. The results indicated that H2 would enhance the CO2 reduction at H2 partial pressures, 0.01atm、0.05atm、0.2atm under irradiation by AM 1.5G sunlight on gas-liquid reactor at ambient temperature. However, increasing H2 pressure did not enhance CO reduction. An optimal H2 pressure, 0.01atm, was observed with main products, methane, methanol and formic acid. The maximum yields of methane, methanol and formic acid were, 0.85, 7.35 and 2.27 μmol/g, respectively. When the reactor changed to gas reactor, the major product became methane and the maximum yields are 1.58μmol/g under 0.1atm H2 pressure Based on the results of three different reactors, the CO2 photoreduction was then carried out in a twin reactor using visible light. A 300W xenon lamp was used as the visible-light source and a Nafion membrane was applied to divide two sides of the twin reactor for H2 and O2 separately evolution. WO3 was used as oxygen catalyst into the oxidation-side half reactor. Pt/SrTiO3:Rh was used as hydrogen catalyst and Pt/CuAlGaO4 was used as reduction catalyst into the reduction-side half reactor. The yields of H2, methane, methanol and formic acid were 0.74 μmol/g, 0.20 μmol/g, 0.035 μmol/g and 0.07 μmol/g, respectively.
Subjects
CO2 photoreduction
ambient pressure and temperature
photohydrogenation
SDGs
Type
thesis
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