| Research Abstract |
The photochemical and photoelectrochemical reduction of CO_2 with catalysts was investigated. A purpose of the reseach is the development of CO_2 reduction method under ambient pressure.
a) Electrochemical reduction The electrochemical reduction of CO_2 with various metal electrodes are studied in benzalkonium/methanol at ambient temperature and pressure. The metal electrodes used were Ti, Fe, Co, Ni, Pt, Ag, Au, Zn and Sn. The products from CO_2 were CO,methane and ethane. High efficiency CO was formed at Ag, Au, Zn and Sn cathodes. The maximum amount of CO (71%, 185mumol) was formed on Ag electrode. Methane from CO_2 was produced at the Faradaic efficiency of 0.2-3.0% on these electrodes. Faradaic efficiency of ethane and ethylene were 0.5 and 0.3% at Ni electrode. The electrochemical reduction of CO_2 at an extremely low temperature (-30ﾟC) was investigated with a Cu electrode in methanol. Products of the electrochemical reduction of CO_2 were methane, carbon monoxide and ethylene. U
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nder optimal experimental conditions, the Faradaic efficiency of methane was more than 42%. At the low temperature, the efficiency of hydrogen formation as the competitive reaction was depressed to less than 8%. A Cu tube used as electrode was evaluated for the electrochemical reduction of CO_2 under atmospheric pressure. The main products from CO_2 were methanol and formic acid. Under the optimum experimental conditions, the Faradaic efficiencies for methanol, formic acid and methane from CO_2 in the electrochemical reduction system were 18% at-1.7V and 40ﾟC,0.91% at-1.8V and 20ﾟC,and 0.013% at-1.8V and 20ﾟC,respectively.
b) Photoelectrochemical reduction The photoelectrochemical reduction of CO_2 using silicate rock (andesite) powder suspended in water was evaluated. The working electrode was a Cu foil and the counter was a Pt foil. By the photoelectrochemical reduction of CO_2 in 0.1 M KHCO_3 solution dispersing andesite powder, formic acid, methanol, methane, ethylene, carbon monoxide, and hydrogen were mainly produced.
c) Photochemical reduction The photochemical reduction of CO_2 using Cu loaded-silicate rock (granite) powder suspended in water was investigated. By the photochemical reduction, 28 nmol/g of formic acid was pruduced under optimal experimental conditions. Less
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