“…In situ and operando spectroscopies are often employed to gain a mechanistic understanding of electron, ion, and mass transport at catalyst interfaces, 444 providing insights into the surface and bulk structure of catalysts, their composition, oxidation states, and adsorbed intermediates under reaction conditions. 436,441,445 In situ and operando spectroscopies additionally enable critical insights into reaction pathways, 446 especially when coupled with computational studies. Some of the most frequently used in situ and operando characterization techniques of catalyst materials are in situ Raman and surface enhanced Raman spectroscopy (SERS), 445,447 Fourier transform infrared spectroscopy (FTIR), 446 and the synchrotronbased techniques X-ray diffraction, 446 X-ray absorption spectroscopy, 448 near ambient pressure X-ray photoelectron spectroscopy, 446 high-energy-resolution fluorescence-detection X-ray absorption spectroscopy, 449 and X-ray absorption fine structure spectroscopy, 449 sometimes used in grazing incidence angle configuration to enhance catalyst surface specific information.…”