(Invited) In Situ x-Ray Spectroscopies Gear up for Energy Science

Abstract

To reduce global greenhouse gas emissions in response to globalization and increasingly strict carbon emission policies, green energy technologies must be developed. Improving the energy conversion/generation/storage efficiency of energy materials has always been a great challenge. Monitoring the atomic/electronic structures close the interface in many important energy materials, such as nanostructured catalysts, artificially photosynthesizing materials, smart materials, and energy storage devices, is of great importance. Understanding and controlling the interfacial electronic structures of energy conversion/storage materials require in-situ/operando characterization tools, of which synchrotron x-ray spectroscopy is one with many unique features. The last decade has witnessed a golden age of operando and in situ synchrotron x-ray spectroscopy for energy materials. X-ray absorption spectroscopy can be used to determine local unoccupied electronic structures while X-ray emission spectroscopy can be utilized to examine the occupied electronic structure. The additional use of resonant inelastic X-ray scattering reveals inter- or intra-electric transitions (d-d or f-f excitation or charge transfer excitation). An emerging scanning transmission x-ray microscopy is a spatial-resolved x-ray absorption spectroscopy which allows us to study the regional electronic structures. The in situ/operando approach enables modifications of atomic/electronic structures of an energy material in an operational environment to be tracked. This presentation will report recent studies and perspectives of the application of in situ/operando synchrotron x-ray spectroscopy to energy materials. It will also introduce Tamkang University (TKU) end-station constructed at the Taiwan Photon Source (TPS) 45A and 27A beamlines for the in situ/operando x-ray spectroscopic investigation of energy materials.