Laser-Engraved Kapton Electrodes for in-Situ/Operando XAS Characterization of Electrocatalysts for CO2 Reduction

Electrochemical CO₂ reduction (CO₂R) has emerged as a promising solution to mitigate climate change by enabling net-negative emissions while producing valuable fuels and chemicals. However, advancing CO₂R technologies requires in-depth characterization of electrocatalysts under realistic operating conditions to elucidate performance-structure-property relationships that can guide next generation catalyst and reactor designs. X-ray Absorption Spectroscopy (XAS) is a powerful technique for such studies due to its ability to provide real-time insights into catalyst structures and dynamics. However, the success of an in-situ/operando XAS experiments heavily depends on the design of custom electrodes and electrochemical cells that allow the penetration of X-rays to the catalyst layer while mimicking practical reactor conditions. This study introduces a laser-engraved Kapton electrode as a conductive, X-ray-transparent, and mechanically stable substrate, that is integrated into a custom-designed three-electrode electrochemical cell capable of operating in both fluorescence and transmission XAS modes. The Kapton electrode engraved with both a working and counter electrode, demonstrated excellent performance as a catalyst substrate. Copper nanoparticles, used as a model CO₂R catalyst, achieved reproducible product selectivity and activity in the in-situ/operando XAS cell, matching results obtained with conventional setups. This work provides a robust platform for in-situ/operando studies of electrocatalysts, enabling detailed structural and mechanistic insights across diverse reactions. The laser-engraved Kapton electrode and versatile cell design pave the way for advancing CO₂R and other electrochemical technologies by addressing key limitations in XAS-based catalyst characterization. Keywords: Laser-engraved Kapton electrode, in-situ/operando XAS, electrochemical CO2 reduction