H2O2 generated through ORR on cathode in a protic ionic liquid and its utilization in lignin valorization

Lignin valorization to obtain small aromatic compounds requires selective oxidation to break the linkage bonds among the C9 units in lignin molecules. It has been reported that hydrogen peroxide (H 2 O 2 ) generated through the oxygen reduction reaction (ORR) on the cathode could be an appropriate oxidizing reagent to depolymerize lignin, but the current efficiency was still unsatisfactory. In this study, a protic ionic liquid [Et 3 NH][HSO 4 ] is used as electrolyte instead of aqueous solution, and the generation rate of H 2 O 2 is determined as 0.0563 mmol cm −2 min −1 and the current efficiency of 79.7 % by the Ti-TPyP colorimetric method. Then using p -benzylethoxyphenol (PBP) as a lignin model compound, it is figured out that approximately-two molecules of H 2 O 2 are consumed for breaking one α-O-4 ether bond. Finally, in the electrolysis of an actual lignin sample, it is evaluated that about 19.4 molecules of H 2 O 2 are needed for producing one molecule of vanillin when taking vanillin as a representative degradation product of lignin.