Beware of cyclic voltammetry! Measurement artefact in accelerated stress test of fuel cell cathode revealed by operando X-ray diffraction

Comparison of methods to determine electrocatalysts’ surface area in gas diffusion electrode setups: a case study on Pt/C and PtRu/C

“…Recently, Chattot et al investigated the effect of potential cycling to low potential after the application of an accelerated stress test protocol. Their results demonstrate that the observed agglomeration of catalyst particles is induced by cycling to low potential rather than a consequence of the performed stress protocol [63]. Therefore, special care has to be taken, when ECSA methods are performed after or in between stress tests.…”

In Situ and Operando X-ray Scattering Methods in Electrochemistry and Electrocatalysis

“…Beyond the oxidation-dependent size dynamics, WAXS has also been extensively used to investigate the long-term stability of Pt-based catalysts in the environment of electrochemical cells. Taking the nanoparticles’ coherent domain size increase as an indicator of catalyst degradation, the influence of the catalyst support material chemistry such as doped metal oxides − or carbon functionalization, , the initial particles ’size distribution, , the liquid vs solid electrolyte, the upper potential limit during accelerated cycling, or the post-mortem cyclic voltammetry experiment on the material stability were investigated by means of in situ WAXS.…”

“…Furthermore, Chattot et al also characterized in operando the anomalous aging of the Pt catalyst after accelerated stress test (AST). 462 the AST's low potential limit, which removes the surface oxygen from oxophilic sites and causes sintering of the catalyst particles and increase of the electrochemical surface area. These findings are only obtainable by performing operando measurements in industrially relevant, high-performance devices.…”

“…From the WAXS data the size of coherent domains, i.e., the individual crystallites, was determined and the SAXS data provided the size of aggregated particles, given that aggregation occurs during the aging of the catalyst. Furthermore, Chattot et al also characterized in operando the anomalous aging of the Pt catalyst after accelerated stress test (AST) . Interestingly, the catalyst fully degrades only when the potential is swept below the AST’s low potential limit, which removes the surface oxygen from oxophilic sites and causes sintering of the catalyst particles and increase of the electrochemical surface area.…”

Shedding Light on Electrocatalysts: Practical Considerations for Operando Studies with High‐Energy X‐Rays

“…[92] It has e.g been shown that CVs performed after the completion of a typical AST of a PEMFC cause a more coherent domain size increase in the Pt catalyst than the AST itself. [93] This measurement-induced artifact can lead to misinterpretations of catalyst performance, which appears to be less stable. One should carefully choose the operational window in both oxidating and reducing potential windows, as both oxidation and reduction can induce structural changes in the catalyst.…”