Quantitative In Situ Monitoring of Cu-Atom Release by Cu 2 O Nanocatalysts under Photocatalytic CO 2 Reduction Conditions: New Insights into the Photocorrosion Mechanism.

Cu 2 O is among the most promising photocatalysts for CO 2 reduction, however its photocorrosion remains a standalone challenge. Herein, we present an in situ study of the release of Cu ions from Cu 2 O nanocatalysts under photocatalytic conditions in the presence of HCO 3 as a catalytic substrate in H 2 O. The Cu-oxide nanomaterials were produced by Flame Spray Pyrolysis (FSP) technology. Using Electron Paramagnetic Resonance (EPR) spectroscopy in tandem with analytical Anodic Stripping Voltammetry (ASV), we monitored in situ the Cu 2+ atom release from the Cu 2 O nanoparticles in comparison with CuO nanoparticles under photocatalytic conditions. Our quantitative, kinetic data show that light has detrimental effect on the photocorrosion of Cu 2 O and ensuing Cu 2+ ion release in the H 2 O solution, up to 15.7% of its mass. EPR reveals that HCO 3 acts as a ligand of the Cu 2+ ions, promoting the liberation of {HCO 3 -Cu} complexes in solution from Cu 2 O, up to 27% of its mass. HCO 3 alone exerted a marginal effect. XRD data show that under prolonged irradiation, part of Cu 2+ ions can reprecipitate on the Cu 2 O surface, creating a passivating CuO layer that stabilizes the Cu 2 O from further photocorrosion. Including isopropanol as a hole scavenger has a drastic effect on the photocorrosion of Cu 2 O nanoparticles and suppresses the release of Cu 2+ ions to the solution. Methodwise, the present data exemplify that EPR and ASV can be useful tools to help quantitatively understand the solid-solution interface photocorrosion phenomena for Cu 2 O.