Selective Photoelectrochemical Reduction of Aqueous CO 2 to CO by Solvated Electrons

Reduction of CO 2 by direct one‐electron activation is extraordinarily difficult because of the −1.9 V reduction potential of CO 2 . Demonstrated herein is reduction of aqueous CO 2 to CO with greater than 90 % product selectivity by direct one‐electron reduction to CO 2 .− by solvated electrons. Illumination of inexpensive diamond substrates with UV light leads to the emission of electrons directly into water, where they form solvated electrons and induce reduction of CO 2 to CO 2 .− . Studies using diamond were supported by studies using aqueous iodide ion (I − ), a chemical source of solvated electrons. Both sources produced CO with high selectivity and minimal formation of H 2 . The ability to initiate reduction reactions by emitting electrons directly into solution without surface adsorption enables new pathways which are not accessible using conventional electrochemical or photochemical processes.