Calibration was performed by determining the response factor by flowing a calibration gas with known CO and H2 composition under the same condition (9 mL min -1 ). To analyse the products, after electrocatalysis the anolyte was acidified to a pH of 3 with 0.1 M HCl, extracted with EtOAc (3 x 5 mL), dried over MgSO4, filtered and dried at 40°C under vacuum to obtain a light brown solid. The solid was further analysed by 1 H NMR in CDCl3 with mesitylene as internal standard. Control experiments were performed under the same conditions but without the lignin model substrate or lignin fraction dissolved in the anolyte.