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

CuO is among the most promising photocatalysts for CO reduction, however its photocorrosion remains a standalone challenge. Herein, we present an in situ study of the release of Cu ions from CuO nanocatalysts under photocatalytic conditions in the presence of HCO as a catalytic substrate in HO. 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 atom release from the CuO nanoparticles in comparison with CuO nanoparticles under photocatalytic conditions. Our quantitative, kinetic data show that light has detrimental effect on the photocorrosion of CuO and ensuing Cu ion release in the HO solution, up to 15.7% of its mass. EPR reveals that HCO acts as a ligand of the Cu ions, promoting the liberation of {HCO-Cu} complexes in solution from CuO, up to 27% of its mass. HCO alone exerted a marginal effect. XRD data show that under prolonged irradiation, part of Cu ions can reprecipitate on the CuO surface, creating a passivating CuO layer that stabilizes the CuO from further photocorrosion. Including isopropanol as a hole scavenger has a drastic effect on the photocorrosion of CuO nanoparticles and suppresses the release of Cu 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 CuO.