Light, Catalyst, Activation: Boosting Catalytic Oxygen Activation Using a Light Pretreatment Approach

Oxygen activation is a key reaction step in assorted thermal-catalytic processes. Here we use light pretreatment to boost oxygen activation by platinum, palladium, or gold loaded on TiO₂. Light pretreatment improved catalyst performance by altering metal oxidation state and/or activated oxygen (O_ads) generation. For Pt/TiO₂ and Pd/TiO₂, light pretreatment initially promoted O_ads accumulation on the metal. In time, the metal deposits underwent oxidation with a concomitant decrease in the light pretreatment benefit. Au/TiO₂ differed in that no Au oxidation was observed. Electrocatalytic assessment indicated that light pretreatment lowered the energy for oxygen activation and that Au was less able to activate oxygen overall. First-principles calculations demonstrated that light pretreatment reduces the oxygen dissociation barrier as each metal becomes negatively charged via electron injection from the TiO₂ conduction bands. The calculations also illustrated the ability of Pt and Pd to stabilize the oxygen once dissociated, a trait not imbued by Au.