Electrocatalytic Lignin Depolymerization enabled by a Bio-mass-derived Iron Dual-Atom Catalyst: from Synthesis to an In-Operando X-Ray Absorption Spectroscopy Study

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 dual-atom catalyst (DAC) 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 pho-toelectron spectroscopy (XPS). These techniques confirmed the DAC’s atomic dispersion and chemical composition. The DAC’s in-operando stability was confirmed through XAS under varying electrochemical potentials. In a water/sodium carbonate electrolyte, the DAC 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 DACs 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