Efficient harvesting of electricity, aromatic aldehydes and H2 from lignin over nanoflower-like cobalt-based bifunctional electrocatalysts

Abstract

Lignin is a promising feedstock for the production of aromatic compounds and green energy. Here, using cobalt-based bifunctional electrocatalysts, we have developed a new coupled system for efficient transformation of lignin into electricity, aromatic aldehydes and H₂. A facile approach for preparing nanoflower-like catalysts has been developed by using high current density electrodeposition of Co on Ni foam. The obtained electrode showed excellent performance in converting lignin to electricity in a direct lignin fuel cell (DLFC) and in the electro-oxidation of lignin to obtain aromatic aldehydes, as well as the hydrogen evolution reaction in an electrolytic cell. The peak power density of the DLFC reached 196.1 mW cm⁻². By using the DLFC as a power supply for lignin depolymerization and the HER, the endogenous electrons of lignin could be well transferred to water, resulting in the formation of aromatic aldehydes and H₂ without the input of external electricity. The total aromatic aldehyde yields at the anodes of the DLFC and the electrolytic cell were 2.90% and 3.34%, respectively, and the H₂ production at the cathode of the electrolytic cell was 12.7 mL cm⁻². This work can thus provide a novel system for lignin valorization and sustainable production of hydrogen.