In Situ X‐ray Absorption Spectroscopy of Metal/Nitrogen‐doped Carbons in Oxygen Electrocatalysis

Abstract

Metal/nitrogen-doped carbons (MÀ NÀ C) are promising candidates as oxygen electrocatalysts due to their low cost, tunable catalytic activity and selectivity, and well-dispersed morphologies. To improve the electrocatalytic performance of such systems, it is critical to gain a detailed understanding of their structure and properties through advanced characterization. In situ X-ray absorption spectroscopy (XAS) serves as a powerful tool to probe both the active sites and structural evolution of catalytic materials under reaction conditions. In this review, we firstly provide an overview of the fundamental concepts of XAS and then comprehensively review the setup and application of in situ XAS, introducing electrochemical XAS cells, experimental methods, as well as primary functions on catalytic applications. The active sites and the structural evolution of MÀ NÀ C catalysts caused by the interplay with electric fields, electrolytes and reactants/intermediates during the oxygen evolution reaction and the oxygen reduction reaction are subsequently discussed in detail. Finally, major challenges and future opportunities in this exciting field are highlighted.

Dual‐Atomic‐Site Catalysts for Molecular Oxygen Activation in Heterogeneous Thermo‐/Electro‐catalysis

“…Especially, accurate identification of the structure and dynamic changes of DASCs active sites under reaction conditions is helpful to understand the property of DASCs and guide the design of catalysts. In situ X‐ray absorption spectroscopy (XAS) may be a powerful tool for monitoring the dynamic changes of the chemical valence and coordination environment of DASCs under reaction conditions [48] …”

“…In situ X-ray absorption spectroscopy (XAS) may be a powerful tool for monitoring the dynamic changes of the chemical valence and coordination environment of DASCs under reaction conditions. [48] Last, the application of DASCs for MOA mainly focuses on CO oxidation and electrocatalytic ORR recently. Considering the diversity and flexibility of dual-atomic structure, it is expected to become a candidate for the next generation of efficient catalysts.…”

Low-cost transition metal–nitrogen–carbon electrocatalysts for the oxygen reduction reaction: operating conditions from aqueous electrolytes to fuel cells

“…In addition, in situ electron microscopy and X-ray absorption spectroscopy techniques can be used to observe the changes in the morphology and bulk structure of catalysts during the reaction process in real-time. 82 However, these characterization methods mainly operate at the aqueous electrolyte/electrode testing level, which oversimplifies the ORR reaction conditions in practical PEMFCs. The conclusions drawn from these techniques may not be directly applicable to the working environment of fuel cells.…”

An asymmetrically coordinated ZnCoFe hetero-trimetallic atom catalyst enhances the electrocatalytic oxygen reaction

“…S28, ESI †) were conducted in standard fluorescence excitation mode during the potentials relevant to the ORR. [57][58][59] In Fig. 4(a), the Zn absorption edge gradually migrates to a lower energy at the applied potential of 1.0 V, resulting in the lower oxidation state (Fig.…”