Understanding the behavior of energy-related materials under realistic operating conditions is essential for the rational design of more efficient systems for energy conversion and storage. The chemical composition, oxidation states, and structural evolution at interfaces and in the bulk are strongly influenced by the surrounding environment, ultimately governing the material’s performance and long-term stability. This is particularly critical for complex, hybrid, or nanostructured materials, where subtle changes at the atomic or molecular level can lead to significant variations in functionality. However, capturing such information during operation remains highly challenging, as the harsh conditions required for many processes—such as high pressures, temperatures, liquid electrolytes, intense illumination, or reactive gas atmospheres—are often incompatible with traditional analytical methods.

Synchrotron-based X-ray techniques have emerged as powerful, non-destructive tools to address these challenges, providing element-specific insights into electronic structure, oxidation states, local coordination, and chemical speciation from the bulk to buried interfaces. These capabilities are especially valuable for studying dynamic processes in energy technologies, including charge transfer, ion transport, and interfacial reactions. Despite their great potential, the application of synchrotron X-ray methods under in situ or operando conditions—particularly in electrochemical, catalytic, and photoactive environments—has long been limited by constraints related mainly to the available sample environments to mimic the relevant experimental conditions.

In recent years, major progress has been achieved in adapting synchrotron methodologies to probe functional energy systems under relevant conditions. Advanced cell designs, time-resolved techniques, and multimodal approaches now enable direct observation of materials while they operate. This symposium will highlight recent advances in in situ and operando synchrotron X-ray techniques for the study of energy materials, including electrocatalysts, battery electrodes, photovoltaic absorbers and interfaces, and systems for hydrogen production and CO₂ valorization. Emphasis will be placed on both methodological developments and their application to technologically relevant processes, with the goal of bridging the gap between advanced materials characterization and functional understanding under real operating conditions.