X-ray spectroscopy of energy materials under in situ/operando conditions

A perspective and brief review of in situ/operando X-ray spectroscopic techniques with focus on energy materials is presented, including discussion on current status, choice of cells and suitable X-ray energy range. Initial discussion focuses on the scientific advancement achieved using ambient pressure X-ray photoelectron spectroscopy (APXPS) at the solid/gas interface, and then progresses through the techniques evolution to probe the liquid/vapor and the emerging solid/liquid interface. This is followed by an overview of soft X-ray adsorption spectroscopy (sXAS) for energy science using both window and windowless cell configurations. Concluding remarks provide a future outlook for where the authors believe these techniques and class of science will progress toward.