O2 activation is essential in life processes, in energy conversion (fuel cells), and in many catalysis applications (organic oxidation and hydrogenperoxide production).  In organic oxidation reactions, the catalytic oxidation capacity or oxidation rate is dependent on the O2 activation capacity or O2 activation rate. Previous research reported that Au deposits on a TiO2 support are able to catalyse formic acid oxidation at ambient conditions by activating molecular oxygen, and treating the Au/TiO2 with UV light before reaction enhances the oxygen activation capacity of Au/TiO2. The extent of the enhancement provided by pre-treatment is a function of the Au loading, light pre-treatment time, and initial formic acid loading.

In this study, we exploited the semiconducting properties of TiO2 as a support and the low activation energy of Au to investigate the pre-illumination enhancement effect on the oxidation reaction in an aqueous system.  UV light pre-treatment was found to invoke the transfer of photoexcited electrons from the TiO2 support to the Au deposits, which catalyses molecular oxygen activation and promotes the oxidation reaction. Confirmation that light pre-treatment stimulated oxygen activation was seen via electrochemical oxygen reduction reaction (ORR) assessment which showed an increased ORR efficiency (higher current density) and a decreased activation energy (lower onset potential) after UV light pre-treatment. The work also featured a single-crystal study employing Scanning Tunneling Microscopy coupled with Density Functional Theory calculations.

Read more on Catalysis Science and Technology, doi: 10.1039/c6cy01717g

Proposed electron pathways in the process of molecular oxygen activation on Au/TiO2 during UV light pre-illumination