Electrocatalytic degradation of rice straw lignin in alkaline solution through oxidation on a Ti/SnO2–Sb2O3/α-PbO2/β-PbO2 anode and reduction on an iron or tin doped titanium cathode
A novel procedure for selective production of biomass-based compounds by electrochemical conversion has been developed in this work. At ambient pressure and mild temperature, rice straw lignin dissolved in sodium hydroxide solution was directly electro-oxidized on the surface of a Ti/SnO2–Sb2O3/α-PbO2/β-PbO2 anode, and subsequently, electro-reduction by the electro-generated chemisorbed hydrogen on the titanium-based (iron or tin doped titanium) cathodes proceeded. The electro-catalysis could effectively break the chemical linkages among phenylpropyl units in rice straw lignin, and more than 16 kinds of aromatic compounds containing phenols, aromatic hydrocarbon, aromatic ester, aromatic ketone, aromatic acid and aromatic aldehyde (e.g. guaiacol, syringol, dihydroeugenol, vanillin, p-coumaric acid, ferulic acid, etc.) were generated and identified utilizing GC-MS measurement. The operation conditions for the enhancement of the product yield including the current density, lignin concentration, temperature and reaction time were optimized. The results indicate that the properties of the cathode materials, current density and reaction time play important roles in the electrocatalytic hydrogenation of rice straw lignin.