Efficient Electrochemical Flow System with Improved Anode for the Conversion of CO₂to CO

The electroreduction of CO2 to CO or other products is one approach to curb the rise in atmospheric CO2 levels and/or to store excess energy of renewable intermittent sources like solar and wind. To date most efforts have focused on improving cathode catalysis, despite other components such as the anode (oxygen evolution reaction, OER) also being of key importance. Here, we report that the dihydrate form of IrO2 as the anode catalyst in alkaline media can achieve onset cell potentials as low as −1.55 V with a cathode overpotential of only 0.02 V, partial current densities for CO as high as 250 mA cm−2 (compared to ∼130 mA cm−2 with a Pt anode), and energy efficiencies as high as 70%. The IrO2 non-hydrate proved to be much more durable by maintaining more than 90% of its activity after cycling the anode potential over the 0 to 1.0 V vs. Ag/AgCl range for over 200 times, whereas the dihydrate lost most of its activity after 19 cycles. Possible causes for these differences are discussed. This work shows that improvements to the anode, so to the OER, can drastically improve the prospects of the electrochemical reduction of CO2 to useful chemicals.