(Table ). Despite of the decrease in current density and CO formation rates, the CO selectivity remained stable, highlighting the structural stability of CoPL. After electrolysis, the anolyte was worked-up (see Experimental Section for details) and the crude product was analysed by and), which shows that aromatic monomer formation is promoted by electrooxidation. The observed 1 H NMR signals corresponded to syringaldehyde and vanillin (see Figure , and Figure ), which are aromatics that can be formed from lignin. 8, 10 After 4 h CA, 0.14±0.03 µmol and 0.31±0.03 µmol of vanillin and syringaldehyde were detected, respectively. These yields equated to 0.62 g of vanillin and 1.65 g of syringaldehyde per kilogram of lignin. Compared with oxygen evolved from water oxidation, vanillin and syringaldehyde have potential as bio-derived monomers in the polymer industry. The observed moderate yields for vanillin and syringaldehyde could be attributed to the acidic degradation of reaction intermediates, i.e., lignin-fragment oxidation decreased the local pH at the CP|MWCNT anode surface below 11.5, and hence halt the formation of the targeted aromatics. In addition to the two identified aromatic compounds, other unidentified signals in the aromatic aldehyde (~9.8 ppm) and methoxy regions (3.8-4.0 ppm) can be observed in the 1 H NMR spectra (Figure ). In comparison with CP|MWCNT, the use of heterogeneous anodes for lignin oxidation based on metals/metal oxides, such as toxic Pb/PbO2, has been reported. For instance, these Pb/PbO2 anodes were able to generate different lignin-derived products, such as vanillin (5.83 g kglignin -1 ) and syringaldehyde (9.30 g kglignin -1 ), via electrooxidation/electrohydrogenation of bamboo-derived lignin when used with Cu cathodes in 1 M NaOH solution. Despite the difficulty to compare this previously reported system with our CP|MWCNT||CP|CoPL system due to the different experimental conditions (i.e., electrode materials and surface, pH, temperature, substrate concentration, applied voltage and currents), the metal-free CP|MWCNT anodes were able to generate yields of vanillin and syringaldehyde within the same order or one-order of magnitude lower than those reported for the metal/metal oxide based Pb/PbO2||Cu system.