In situ/Operando Synchrotron Radiation Analytical Techniques for CO 2 /CO Reduction Reaction: From Atomic Scales to Mesoscales.

Electrocatalytic carbon dioxide/carbon monoxide reduction reaction (CO (2) RR) has emerged as a prospective and appealing strategy to realize carbon neutrality for manufacturing sustainable chemical products. Developing highly active electrocatalysts and stable devices has been demonstrated as effective approach to enhance the conversion efficiency of CO (2) RR. In order to rationally design electrocatalysts and devices, a comprehensive understanding of the intrinsic structure evolution within catalysts and micro-environment change around electrode interface, particularly under operation conditions, is indispensable. Synchrotron radiation has been recognized as a versatile characterization platform, garnering widespread attention owing to its high brightness, elevated flux, excellent directivity, strong polarization and exceptional stability. This review systematically introduces the applications of synchrotron radiation technologies classified by radiation sources with varying wavelengths in CO (2) RR. By virtue of in situ/operando synchrotron radiationanalytical techniques, we also summarize relevant dynamic evolution processes from electronic structure, atomic configuration, molecular adsorption, crystal lattice and devices, spanning scales from the angstrom to the micrometer. The merits and limitations of diverse synchrotron characterization techniques are summarized, and their applicable scenarios in CO (2) RR are further presented. On the basis of the state-of-the-art fourth-generation synchrotron facilities, a perspective for further deeper understanding of the CO (2) RR process using synchrotron radiation analytical techniques is proposed.