Lignin decomposition has been investigated by several diverse methods, however, these typically involve thermochemical or electrochemical approaches requiring severe reaction conditions. This study explores a heterogeneous photocatalysis approach for driving the chemoselective oxidation of recurring C–O bonds found in lignin using dye-sensitized photoelectrochemical cells (DSPECs) under mild condition. A TiO2nanorod electrode was prepared with surface immobilized RuC, (bis-2,2'-bipyridine)(2,2'-bipyridine-4,4'-dicarboxylic acid), coatings on conductive fluorine-doped glass (FTO) substrates (FTO/TiO2-RuC). The photophysical and electrochemical properties of FTO/TiO2-RuC photoanode were studied using the UV-visible absorption, cyclic voltammetry (CV), incident photon to current efficiency (IPCE), impedance and photoluminescence spectroscopy. Interestingly, the FTO/TiO2-RuC photoanode in the presence of a hydrogen atom transfer (HAT) agent established a photocatalytic route to use interfacial light absorption/electron transfer to carry out the selective oxidation of substrates with benzylic 2° alcohol groups to form the benzylic ketone in lignin model compounds (e.g. veratrylglycerol-β-guaiacyl ether model compound). The photocatalytic conversion of 2° alcohol to ketone was &gt; 96% over 8 h illumination experiment with 200 mW cm-2white light (AM 1.5G) under aerobic mild conditions. This novel system via HAT process opens a new opportunity for biomass processing of lignin to yield valuable aromatic compounds.

Photoelectrocatalytic chemoselective lignin oxidation in lignin models at Ru-coated TiO2 nanorod photoanodes

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.