Semiconductor Photocatalysis of Bicarbonate to Solar Fuels: Formate Production from Copper(I) Oxide

Copper-oxide-based photocatalysts, micron- and nanosized, and silver nanoparticle–copper oxide nanocomposites (Ag/Cu₂O) were characterized and evaluated for the first time in the application of bicarbonate conversion to formate. The Ag/Cu₂O nanocomposite yielded considerable production improvement over pure copper oxides due to the role of silver as a plasmonic sensitizer. We attribute these marked production improvements to plasmon-induced electron transfer from metal to semiconductor. These photocatalysts were studied in two different hole scavenger solvents (2-propanol and glycerol) using a solar simulator with air mass coefficient 1.5 and 0 (AM 1.5, AM 0) filters. Formate production increased significantly with AM 0 solar irradiation due to inclusion of the ultraviolet portion of the solar spectrum, and nanoparticulate Cu₂O showed improved photocatalysis relative to micron Cu₂O. Green chemistry solvent, glycerol, proved to be a far superior hole scavenger in comparison to 2-propanol.