Kenji Iiba

Electrochemical reduction of carbon dioxide to ethylene with high Faradaic efficiency at a Cu electrode in CsOH/methanol

Abstract The electrochemical reduction of CO2 with a Cu electrode in CsOH/methanol-based electrolyte was investigated. The main products from CO2 were methane, ethylene, ethane, carbon monoxide and formic acid. A maximum Faradaic efficiency of ethylene was 32.3% at −3.5 V vs. Ag/AgCl saturated KCl. The best methane formation efficiency was 8.3% at −4.0 V. The ethylene/methane current efficiency ratio was in the range 2.9–7.9. In the CsOH/methanol, the efficiency of hydrogen formation, being a competitive reaction against CO2 reduction, was depressed to below 23%.

Electrochemical conversion of carbon dioxide to formic acid on Pb in KOH/methanol electrolyte at ambient temperature and pressure

The electrochemical reduction of CO2 in KOH/methanol-based electrolyte has been investigated on a lead wire electrode at ambient temperature and pressure. The major products of electrochemical reduction of CO2 were formic acid, CO and methane. The formation of formic acid from CO2 predominated in the potential range −1.8 to −2.5V vs Ag/AgCl (saturated KCl). Hydrogen evolution in competition with CO2 reduction was observed at only 3.5% faradaic efficiency. The partial current density for CO2 reduction was more than 22 times larger than that for hydrogen evolution. Study of the Tafel plot showed that the reduction of CO2 to formic acid and CO was not limited by mass transfer in this potential range.

Electrochemical reduction of CO2 on Au in KOH + methanol at low temperature

The electrochemical reduction of CO2 in KOH + methanol electrolyte was investigated with a gold electrode at −25, −15, 0 and 15°C. The main products from CO2 were carbon monoxide and formic acid. The current efficiency for CO formation was larger than that for formic acid formation. In general, the formation efficiency for CO increased as the temperature decreased, however in contrast, hydrogen formation decreased. The selectivity of CO2 reduction over H2 evolution was ameliorated by decreasing temperature. From the Tafel plot study, a sufficiently high mass transfer of CO2 to the electrode was confirmed even in the low temperature region. Consequently, it was found that temperatures of less than 0°C were effective for the suppression of hydrogen formation on the Au electrode in the KOH + methanol electrolyte.

Electrochemical reduction of CO2 at an Ag electrode in KOH-methanol at low temperature

Abstract The electrochemical reduction of CO 2 in 0.1 M KOH-methanol electrolyte with a silver electrode was investigated at 248, 258 and 273 K. The main products from CO 2 were carbon monoxide and formic acid. A predominant formation of CO from CO 2 on Ag electrode in the methanol electrolyte was found. The formation efficiency of CO increased at relatively negative potential as temperature decreased, however in contrast, hydrogen formation decreased. The selectivity of CO 2 reduction over H 2 evolution was ameliorated by lowering temperature. From the Tafel plot study, a sufficiently high mass transfer of CO 2 to the electrode was confirmed even in low temperature region. Consequently, it was found that low temperature was extremely effective for the depression of hydrogen formation on Ag electrode in the KOH-methanol.

Reduction of carbon dioxide to petrochemical intermediates

The electrochemical reduction of CO2 at the Cu electrode was investigated in methanol-based electrolyte using various cesium supporting salts as the ionophore at an extremely low temperature (243 K). Cesium acetate, chloride, bromide, iodide, and thiocyanate were used as the ionophore. The main products from CO2 by electrochemical reduction were methane, ethylene, ethane, carbon monoxide, and formic acid. In the methanol-based electrolyte using cesium supporting salts, except for acetate, the Faradaic efficiency for ethylene was larger than that for methane. This research can contribute to large-scale manufacturing of petrochemical interme diate products, such as methane and ethylene, from readily available and cheap raw materials: CO2-saturated methanol from industrial absorbers (the Rectisol process). Thus the synthesis of hydrocarbons by the electrochemical reduction of CO2 may be of practical interest for fuel production, storage of solar energy, and production of intermediate materials for the petrochemical industry.The electrochemical reduction of CO2 at the Cu electrode was investigated in methanol-based electrolyte using various cesium supporting salts as the ionophore at an extremely low temperature (243 K). Cesium acetate, chloride, bromide, iodide, and thiocyanate were used as the ionophore. The main products from CO2 by electrochemical reduction were methane, ethylene, ethane, carbon monoxide, and formic acid. In the methanol-based electrolyte using cesium supporting salts, except for acetate, the Faradaic efficiency for ethylene was larger than that for methane. This research can contribute to large-scale manufacturing of petrochemical interme diate products, such as methane and ethylene, from readily available and cheap raw materials: CO2-saturated methanol from industrial absorbers (the Rectisol process). Thus the synthesis of hydrocarbons by the electrochemical reduction of CO2 may be of practical interest for fuel production, storage of solar energy, and production of intermediate materials for the petroc...

Electrochemical CO2 Reduction on a Copper Wire Electrode in Tetraethylammonium Perchlorate Methanol at Extremely Low Temperature

The electrochemical reduction of CO2 in tetraethylammonium perchlorate methanol electrolyte was investigated with a copper wire electrode at an extremely low temperature (-30 C). The main products from CO2 by the electrochemical reduction were methane, ethylene, carbon monoxide, and formic acid. Under the optimum experimental conditions, 28.1% faradaic efficiency methane, 7.2% ethylene, 67.8% carbon monoxide, and 23.2% formic acid were produced from CO2 by the electrochemical reduction. The maximum partial current densities for CO2 reduction and hydrocarbons were 4.5 and 1.6 mA cm-2 at 4.0 V vs SCE, respectively. At -30 C, the efficiency of hydrogen formation, being a competitive reaction against CO2 reduction, was suppressed to less than 10.1%.