Operando chemistry of catalyst surfaces during catalysis

Abstract

Chemistry of a catalyst surface during catalysis is crucial for a fundamental understanding of mechanism of a catalytic reaction performed on the catalyst in the gas or liquid phase. Due to the pressure- or molecular density-dependent entropy contribution of gas or liquid phase of the reactants and the potential formation of a catalyst surface during catalysis different from that observed in an ex situ condition, the characterization of the surface of a catalyst under reaction conditions and during catalysis can be significant and even necessary for understanding the catalytic mechanism at a molecular level. Electron-based analytical techniques are challenging for studying catalyst nanoparticles in the gas or liquid phase although they are necessary techniques to employ. Instrumentation and further development of these electron-based techniques have now made in situ/operando studies of catalysts possible. New insights into the chemistry and structure of catalyst nanoparticles have been uncovered over the last decades. Herein, the origin of the differences between ex situ and in situ/operando studies of catalysts, and the technical challenges faced as well as the corresponding instrumentation and innovations utilized for characterizing catalysts under reaction conditions and during catalysis, are discussed. The restructuring of catalyst surfaces driven by the pressure of reactant(s) around a catalyst, restructuring in reactant(s) driven by reaction temperature and restructuring during catalysis are also reviewed herein. The remaining challenges and possible solutions are briefly discussed.

Surface‐supported cluster catalysis: Ensembles of metastable states run the show

“…Hence, operando methodology describes in situ spectra under true catalytic operation as determined by simultaneous online activity/selectivity measurements. Determination of intrinsic reaction kinetics of catalyzed reactions is of importance in the safe and economical design and control of industrial chemical and environmental processes, and in the development of new and improved catalysts . Echoing all the assertions in this review, operando studies have shown that catalysts may undergo dynamic structural transformations upon small changes in the reaction conditions and such transformations have a strong impact on the performance of the catalysts .…”

The Orientation of Silver Surfaces Drives the Reactivity and the Selectivity in Homo‐Coupling Reactions

“…Surface science techniques and scanning tunnelling microscopy (STM) are tools of choice for studying basic catalytic processes thanks to their ability to provide unique characterization of the structural and electronic state of the catalyst surface at the nanoscale . Notably, real‐space imaging with molecular resolution allows discriminating between the different reaction products occurring possibly simultaneously on the surface ,…”

Needs and Gaps for Catalysis in Addressing Transitions in Chemistry and Energy from a Sustainability Perspective

“…[25] The laboratorybased NAP-XPS system is even availablef or daily catalyst studies. [25] The laboratorybased NAP-XPS system is even availablef or daily catalyst studies.…”

“…[25] Under thesec onditions, photoemission from the gas phase may overcome surface-bound contributions. [25] Under thesec onditions, photoemission from the gas phase may overcome surface-bound contributions.…”