Electrocatalytic reduction of low concentration CO₂

Abstract

Utilization of low concentration CO₂ contained in the exhaust gases from various industries and thermal power stations without the need for energy-consuming concentration processes should be an important technology for solving global warming and the shortage of fossil resources. Here we report the direct electrocatalytic reduction of low concentration CO₂ by a Re(i)-complex catalyst that possesses CO₂-capturing ability in the presence of triethanolamine. The reaction rate and faradaic efficiency of CO₂ reduction were almost the same when using Ar gas containing 10% CO₂ or when using pure CO₂ gas, and the selectivity of CO formation was very high (98% at 10% CO₂). At a concentration of 1% CO₂, the Re(i) complex still behaved as a good electrocatalyst; 94% selectivity of CO formation and 85% faradaic efficiency were achieved, and the rate of CO formation was 67% compared to that when using pure CO₂ gas. The electrocatalysis was due to the efficient insertion of CO₂ into the Re(i)-O bond in <i>fac</i>-[Re(dmb)(CO)₃{OC₂H₄N(C₂H₄OH)₂}] (dmb = 4,4'-dimethyl-2,2'-bipyridine).