Methodological Optimization of ATR-IR Spectroelectrochemistry for Powdered and Poorly Conductive Electrocatalysts

In-situ infrared spectroscopy combined with electrochemistry has become a key tool for studying the processes that govern the activity of electrocatalysts under operating conditions. However, its application has been limited almost exclusively to model electrodes, which are either electronically conductive or specifically designed to maximise the ATR optical signal, thereby limiting its use for a family of emerging heterogenous catalysts typically available in powder form and exhibiting poor electrical conductivity. Extending ATR-IR spectroelectrochemistry to this type of catalyst requires simultaneously reconciling optical, adhesion and electrochemical requirements which, until now, have rarely been addressed systematically. Rather than focusing on the elucidation of electrocatalyst mechanisms, this paper presents a structured and transferable methodology for optimising ATR-IR spectroelectrochemical measurements on emerging classes of electrocatalyst. Three groups of interrelated parameters that mostly affect the feasibility of the technique, namely spectroscopic, interfacial and electrochemical parameters, are discussed proposing a step-by-step workflow that enables their methodological standardization and balance. The proposed workflow is validated by applying this methodology to three different materials (Ni(OH) 2 , ZnO and Zn-Al LDH) showing distinct spectroscopic, electrochemical and interfacial properties. The results demonstrate that, following appropriate optimisation, ATR spectroelectrochemistry can be extended to more challenging powdered catalyst layers, providing a practical and generalisable guide for future robust mechanistic investigations of this broad family of materials and contributing to the rational understanding and development of new electrocatalysts for reactions of energy and chemical interest.