In Situ Observation of Model Catalysts under Reaction Conditions Using X‐ray Core‐Level Spectroscopy

Abstract

Chemical reactions at solid surfaces are of great importance in heterogeneous catalysis and the understanding of their reaction mechanisms has been challenged for a long time by a wide variety of approaches. In situ observation of model catalysts under reaction conditions is a promising approach to understand the mechanisms. Toward this aim we have been developing several spectroscopic techniques using synchrotron-radiation X-rays. In this Personal Account, synchrotron-radiation-based X-ray core-level spectroscopies for in situ observation are introduced and some of their applications in studying the mechanisms of catalytic reactions are highlighted. Future directions for further development of these spectroscopies are also described.

Ceria-Based Catalysts Studied by Near Ambient Pressure X-ray Photoelectron Spectroscopy: A Review

“…The application of NAP-XPS in heterogeneous catalysis has opened new possibilities and a large number of reviews and book chapters have appeared in the last years [50,[52][53][54][55][56][57][58][59][60][61][62][63][64][65]. NAP-XPS has been used within this field to study from single crystals and model metal-oxide systems [35,55,58,60,66] to more realistic mono-and bimetallic unsupported nanocatalysts and metal-oxide complex systems [57]. For the particular case of bimetallic catalysts, the combination of NAP-XPS with synchrotron radiation allows following the segregation of the different metals under reaction conditions [67], i.e., the excitation energy can be tuned and therefore it is possible to detect photoelectrons ejected from different depths of the sample without destroying it.…”

An Operando Investigation of (Ni–Fe–Co–Ce)Ox System as Highly Efficient Electrocatalyst for Oxygen Evolution Reaction

“…The methods have provided element-specific characterization of catalysts 53,54 and illustrated the importance of collecting data under functional conditions. [55][56][57][58][59][60] In the present work we advance the state-of-the-art of these techniques with the interrogation of the quinary oxide catalyst. We investigate the role of each transition metal-Ce oxide using two operando techniques (defined here as actively performing OER under potentiostatic control), ambient pressure X-ray photoelectron spectroscopy (APXPS) as a surface probe and X-ray absorption spectroscopy (XAS) as a bulk-probe.…”

Characterization of oxygenated species at water/Pt(111) interfaces from DFT energetics and XPS simulations

“…In contrast, core-level binding energies generated by XPS have been employed to identify similar species under both UHV [23][24][25][26][27][28][29][30] and in-situ electrocatalytic conditions. [7,[31][32][33][34][35][36][37] Of particular relevance for developing fundamental understanding of the ORR, O1s binding energies have been fit and assigned to various oxygenated species, including adsorbed O, [7,23,24,30] multilayer H 2 O, [7,23,24,30] adsorbed H 2 O, [7,[23][24][25]30] hydrated OH, [7,23,24,30] and nonhydrated OH [7] at the water/Pt interface. Since the core-level binding energies are very sensitive to the local environment, every oxygenated species with different local structure has distinct binding energies, providing the tantalizing possibility of rigorously determining the structure and hydration environment of OH.…”