Electrochemical Generation of ROS in Ionic Liquid for the Degradation of Lignin Model Compound

p-benzyloxyl phenol (PBP), as a lignin model compound, was electrochemically degraded in [BMIM]BF4 ionic liquid (IL) using an oxygen reduction reaction (ORR) cathode. The utilization of this kind of aprotic IL made it possible to identify which kind of reactive oxygen species (ROS) played an important role in the electrochemical depolymerization of lignin. Electrochemical study confirmed that superoxide radical (center dot O-2(-)), the one-electron reductive product of dioxygen, is the main resultant of ORR in [BMIM]BF4. However, the generated center dot O-2(-) radical transformed into hydroperoxyl radical (center dot OOH) in the presence of protons donated by PBP, and then received one more electron to form H2O2, which then attacked and broke down the alkyl-O-aryl bonds in PBP molecules. The continuous electrolysis of PBP in [BMIM]BF4 provided indirect evidence to reveal that the in situ generated H2O2 on ORR cathode was responsible for the cleavage of ether bonds in PBP. (C) 2018 The Electrochemical Society.