Selective Photoelectrochemical Reduction of Aqueous CO2 to CO by Solvated Electrons

Reduction of CO₂ by direct one‐electron activation is extraordinarily difficult because of the ?1.9 V reduction potential of CO₂. Demonstrated herein is reduction of aqueous CO₂ to CO with greater than 90 % product selectivity by direct one‐electron reduction to CO₂^.? 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 CO₂ to CO₂^.?. 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 H₂. 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.