Electrocatalytic lignin depolymerization enabled by a biomass-supported atomically dispersed iron catalyst

Abstract

Transitioning from crude oil to renewable carbon sources is crucial for a circular economy. Lignin, a byproduct of the paper industry, has significant potential as a renewable feedstock, but its efficient depolymerization remains challenging. This study presents an iron atomically dispersed catalysts supported on biochar derived from spent coffee grounds for the selective electrochemical depolymerization of Kraft lignin under ambient conditions. The catalyst was synthesized via pyrolysis and characterized using X-ray absorption spectroscopy (XAS), low-energy ion scattering (LEIS), and X-ray photoelectron spectroscopy (XPS). These techniques confirmed the catalysts atomic dispersion and chemical composition. The catalysts in-operando stability was confirmed through XAS under varying electrochemical potentials. In a water/sodium carbonate electrolyte, the catalysts achieved lignin depolymerization within 20 h. Nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) analyses identified aliphatic products such as sodium acetate and formate, alongside phenolic monomers and dimers. This work demonstrates the potential of the iron atomically dispersed catalyst for the valorization of biomass while establishing a framework for the monitoring of catalyst behavior at an atomic level during electrochemical biomass depolymerization, thus contributing to the development of advanced catalytic processes.