Heterogeneous catalysis at metal-oxide interfaces using in situ and operando spectroscopy: From nanoparticles to single-atom sites

The use of in situ and operando spectroscopy in applied catalysis is driven by the recognition that it is a powerful tool to elucidate the nature and changes of atomic arrangements and chemical species at a surface during heterogeneous catalytic reactions. The aim of this article is to provide an overview of recent processes in using in situ and operando spectroscopy to investigate the relationship between structure and activity/selectivity, as well as mechanisms of gas-surface reactions on oxide-supported metal catalysts and at metal-oxide interfaces. The selected reactions include water-gas shift reaction, CO oxidation, and selective CO2 hydrogenation. Special attention is given to oxide-supported single-atom catalysts, which are known to provide maximum atom utilization and high efficiency towards catalytic performance but is lack of detailed understanding under operando conditions. Recent research from 2018 to 2021 using in situ and operando spectroscopy with an emphasis on diffuse-reflectance infrared spectroscopy (DRIFTS), combined with X-ray spectroscopy and theoretical calculations, are reviewed for the three reactions on relevant catalysts for general audience in applied catalysis. The perspectives on how to improve catalytic performance are discussed.