Design and application of an operando XAS cell for biomass electrocatalysis

Operando X-ray absorption spectroscopy (XAS) is a powerful method to probe structural and electronic changes in electrocatalysts under reaction conditions, providing essential insight for the rational design of sustainable catalytic systems. However, the lack of suitable electrochemical cells for strongly absorbing biomass-derived electrolytes, such as lignin-containing media, remains a significant challenge. To date, there have been no reports of a transmission-capable setup for this type of electrolyte systems. We hereby present a newly developed modular operando XAS cell that is chemically resistant, mechanically robust, and reproducibly assembled, specifically designed to support studies in biomass electrocatalysis. The design incorporates 3D-printed polypropylene components, Kapton ® windows, FKM seals, and steel reinforcements, thereby ensuring stable operation under alkaline conditions. It is noteworthy that the configuration facilitates both fluorescence and transmission measurements. In the present study, transmission mode was deliberately employed to circumvent self-absorption artifacts and to optimize data quality. The cell was benchmarked with copper nanoparticles on carbonized cellulose during the electrocatalytic depolymerization of Kraft lignin, a key step in biomass valorization. Operando XAS revealed the structural stability of the metallic Cu 0 state up to −0.74 V versus RHE, while increased noise at more negative potentials correlated with gas bubble formation from water splitting. In accordance with the FAIR principles (Findable, Accessible, Interoperable, and Reusable), all technical drawings and design details are made openly available to promote transparency, reproducibility, and reuse by the broader scientific community. By disclosing both the strengths and limitations of the present study, this work provides a practical blueprint for future studies. We present an operando electrochemical XAS cell enabling transmission measurements for lignin depolymerization, thereby establishing a methodological benchmark for greener and more efficient electrochemical processes for biomass conversion.