Photoelectrochemistry-driven selective hydroxyl oxidation of polyols: Synergy between Au nanoparticles and C3N4 nanosheets

Abstract

Selective and efficient oxidation of a certain hydroxyl group in biomass-derived polyols is quite appealing but challenging. We herein propose a new photoelectrochemical strategy for enhancing the selectivity and kinetics of the middle hydroxyl oxidation in glycerol molecules using Au/C 3 N 4 catalyst. The introduction of illumination and usage of C 3 N 4 are first demonstrated to have a direct bearing on enhancing the selectivity of middle hydroxyl oxidation on Au through the electron transfer and accelerating the kinetics by accumulating photogenerated holes with moderate oxidizability. By this strategy, the selectivity of glycerol to dihydroxyacetone and turnover frequency are achieved as high as 53.7% and unprecedented 4,619 h −1 . The synergy of electronic interaction, localized surface plasmon resonance effect, and photogenerated carriers dual injection is revealed to account for such high selectivity and kinetics of the middle hydroxyl oxidation during the photoelectrochemical process. Our results sheds light on the photoelectrocatalysis-driven selective hydroxyl oxidation in polyols. • Photoelectrochemical strategy to tackle challenging selective hydroxyl oxidation • Reasonably designed polymeric C 3 N 4 nanosheets supported Au as catalyst • Unprecedented kinetics and good selectivity are reported • Synergy mechanism for photoelectrocatalytic process is revealed Different from the harsh conditions of thermocatalysis such as high temperatures and pressures, electrochemical synthesis (i.e., electro-valorization or electro-refinery) promises to handle the chemical production under ambient conditions. The widely known electrochemical synthesis includes nitrogen reduction reaction, carbon dioxide reduction reaction (CO 2 RR), and hydrogen evolution reaction. Actually, the electrochemical synthesis promises to handle more reactions; for example, allylic C-H oxidation ( https://doi.org/10.1038/nature17431 ), desaturation of carbonyl compounds ( https://doi.org/10.1038/s41557-021-00640-2 ), and hydroxyl oxidation (the target reaction in this work). We herein propose a photo-assistant electrochemical strategy to drive hydroxyl oxidation of polyols with high selectivity and unprecedented reaction rate. We hope electrochemical synthesis can be complementary to conventional thermocatalysis and help to build a better society. Simultaneous selectivity and kinetics enhancement of hydroxyl oxidation in polyols is demonstrated using glycerol as the model molecule, which benefits from a photo-assistant electrochemical strategy using heterogeneous Au/p-C 3 N 4 as the catalyst.