Selective aerobic photocatalytic glycerol oxidation on Au/TiO2 with borate additives

Photocatalytic valorization is a sustainable approach for converting glycerol to value-added chemicals under ambient conditions, which remains challenging. Herein, using Au/TiO2 as photocatalyst, we report glycerol oxidation reaction in non-pressurized reactor with borate additives. The activity and selectivity of photocatalytic glycerol oxidation depends on Au loading, borate concentration and solution pH. Both superoxide and hydroxyl radicals are generated due to oxygen reduction and water oxidation by photoexcited charge carriers. Apart from coordinating and protecting the oxidized intermediates from further oxidation, borate additives are discovered to up-regulate the superoxide radical generation, beneficial for C3 products formation. In pH 12 solution, C3 products selectivity of 58% and 37% on liquid-phase and carbon basis respectively, was realized at 94% glycerol conversion under AM 1.5 G irradiation for 4 h. Our finding may help guiding future catalyst design for photocatalytic biomass valorizations, where a balanced oxidative power is needed to steer the reaction pathway.

Automated summary

Using Au/TiO2 as photocatalyst, glycerol oxidation was achieved in a non-pressurized reactor with borate additives. The activity and selectivity of the reaction depended on Au loading, borate concentration, and solution pH. Borate additives not only coordinated and protected oxidized intermediates, but also enhanced the production of superoxide radicals, promoting the formation of C3 products. Under AM 1.5 G irradiation for 4 hours in pH 12 solution, a glycerol conversion rate of 94% was achieved, with C3 product selectivity of 58% on liquid-phase basis and 37% on carbon basis. This finding has implications for future photocatalytic biomass valorization catalyst design, emphasizing the need for balanced oxidative power to guide reaction pathways.