The CNR Beamline for Advanced Circular dicHroism (BACH), operating at the Elettra synchrotron facility in Trieste, works in the EUV–soft X-ray photon energy range and offers selectable light polarization with high energy resolution. Its multi-technique spectroscopic capabilities enable comprehensive investigations of the electronic, chemical, structural, magnetic, and dynamical properties of advanced materials.

A major research line at BACH is the study of energy-related materials under realistic operating conditions, with a particular focus on solid/liquid interfaces relevant to photocatalysis, electrocatalysis, and electrochemical energy storage. Techniques such as X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) are routinely employed in in situ and operando configurations to track, in real time, interfacial phenomena including charge transfer, ion migration, catalytic intermediate formation, and chemical transformations. These approaches are essential for understanding key systems such as batteries, supercapacitors, and catalytic processes for sustainable energy conversion

At BACH, different experimental strategies have been implemented to access liquid–solid interfaces while maintaining compatibility with soft X-ray conditions. One successful method involves encapsulating liquid solutions between a graphene membrane and a solid substrate, enabling temperature- and photo-induced processes to be probed by XAS and XPS [1,2]. A second approach relies on liquid cells based on thin Si₃N₄ membranes that separate the aqueous environment from the vacuum. Several variants of these cells have been developed to meet specific experimental needs, including static configurations, two-electrode cells, and three-electrode electrochemical microfluidic cells [3]. The latter enable in situ cyclic voltammetry, controlled electrodeposition, and operando monitoring of electrocatalytic reactions.

This capability has been applied, for example, to Copper-based materials by resolving porosity, surface utilization, and stability in nanoporous Cu-based catalysts [4], and by uncovering how composition (e.g., Cu–Ag synergy) [5] and interface modifiers influence oxidation states and product selectivity, revealing the key factors governing the formation of C₂⁺ products during CO₂ electroreduction. Together, these results underscore the importance of correlating 3D architecture, chemical dynamics, and catalyst–environment interactions to guide the rational design of high-performance materials for sustainable energy conversion.

In the presentation, I will highlight representative experiments performed under ambient-pressure and liquid electrochemical environments, along with recent technical developments and future directions for advancing operando spectroscopy at the BACH beamline.