Self-powered electrochemical synthesis of hydrogen peroxide from air and lignin†

Abstract

Lignin, which is typically available as a by-product of the pulping process and biomass biorefinery, is a sustainable feedstock for production of carbon fuels and materials. Here, we report a novel coupled electrochemical system to achieve efficient production of H₂O₂ with air as the oxygen source and lignin as a carbon-based catalyst precursor and electron donor (fuel). By using a direct lignin fuel cell to power a paired electrolytic cell, the endogenous electrons of lignin can be transferred to air, resulting in the formation of H₂O₂via a two-electron oxygen reduction reaction. A facile and efficient approach to synthesizing a B,O-doped carbonaceous catalyst was developed with lignin as a carbon precursor, achieving a H₂O₂ productivity of 11 812 mmol g⁻¹ h⁻¹ and a faradaic efficiency of 95.7%. Moreover, by using the [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻ redox couple as the electron mediator for oxidation of lignin on the anode instead of the oxygen evolution reaction, the energy consumption of the electrolytic cell could be decreased by 11.4%. The self-powered system could obtain 93.7% of total electron transfer efficiency and avoid using external electricity. Therefore, this work provides a novel technical route for lignin utilization and production of H₂O₂ and biomass-based chemicals in a sustainable way.