Prospects for electrochemical X-ray photoelectron spectroscopy as a powerful electrochemical interface characterization technique

X-ray spectroscopies provide a powerful way to disentangle the roles of the different elements in electrochemical systems. Within this family of spectroscopies, electrochemical X-ray photoelectron spectroscopy (EC-XPS) has recently emerged as a technique that can specifically probe the heart of any electrochemical process: the electrode-electrolyte interface. Here, we discuss the current state-of-the-art of EC-XPS and review the practical implementation of the measurements. We identify three principal categories of EC-XPS approaches: quasi in situ, thin electrolyte, and thin electrode. As each presents distinct advantages and drawbacks, we highlight the importance of matching the electrochemical system of interest with the most suitable approach.