Electrocatalytic carbon dioxide reduction microchanneled with nanostructured electrodes

The electrocatalytic reduction of carbon dioxide (CO 2 ) is a promising solution for the utilization of renewable energy. Conversion to other useful substances is expected to diversify the applications of CO 2 and alleviate the environmental problems caused by the continuous increase in its concentration in the atmosphere. Herein, an electrochemical reduction microdevice was developed to increase the reduction current density and explore the possibility of the highly efficient electrochemical reduction of CO 2 to produce methane (CH 4 ). A serpentine microchannel composed of an interdigitated Cu cathode and a Pt anode was filled with an electrolyte, and CO 2 gas was flowed through it to attempt CO 2 reduction. To increase the electrocatalytic reaction activity, the base of the electrodes was made of porous Si prepared through metal-assisted chemical etching. This configuration reduced the distance between the anode and cathode and increased the current density. The average Faraday efficiency reached 40 % at an applied potential of −4.2 V versus reversible hydrogen electrode (vs. RHE), with a current density of 316 mA/cm 2 at a temperature of 20 °C. The unique configuration of the microdevice with the interdigitated porous electrodes ensured a high current density and showed a high CO 2 reduction efficiency.