This Review addresses the technical challenges, scientific basis, recent progress, and outlook with respect to the stability and degradation of catalysts for the oxygen evolution reaction (OER) operating at electrolyzer anodes in acidic environments with an emphasis on ion exchange membrane applications. First, the term "catalyst stability" is clarified, as well as current performance targets, major catalyst degradation mechanisms, and their mitigation strategies. Suitable in situ experimental methods are then evaluated to give insight into catalyst degradation and possible pathways to tune OER catalyst stability. Finally, the importance of identifying universal figures of merit for stability is highlighted, leading to a comprehensive accelerated lifetime test that could yield comparable performance data across different laboratories and catalyst types. The aim of this Review is to help disseminate and stress the important relationships between structure, composition, and stability of OER catalysts under different operating conditions.

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The porous transport layer (PTL) is an essential component of the polymer electrolyte membrane water electrolyzer (PEMWE), responsible for a better utilization of the catalyst layer (CL). The PTL allows...

QCD Laplace sum-rules must satisfy a fundamental (Hölder) inequality if they are to consistently represent an integrated hadronic cross-section. After subtraction of the pion-pole, the Laplace sum-rule of pion currents is shown to violate this fundamental inequality unless the u and d quark masses (respectively denoted by mu and m d ) are sufficiently large, placing a lower bound on the 1GeV MS running masses.QCD Laplace sum-rules, a technique which equates a theoretical quantity to an integrated hadronic cross-section to determine a QCD prediction of hadronic properties [1], have demonstrated their utility in numerous applications to hadronic physics. It has recently been shown that Laplace sum-rules must satisfy a fundamental inequality in order to consistently represent an integrated hadronic cross-section [2]. When applied to the Laplace sum-rule related to the pion, a strong dependence on the light quark masses m u and m d occurs in the analysis of this inequality because the pseudoscalar correlation is proportional to (m u + m d ) 2 . In this paper we employ this fundamental Hölder inequality to place lower bounds on the sum of the u and d 1.0 GeV MS running masses.Consider the correlation function of pseudoscalar currents with the quantum numbers of the pion:To leading order in the quark masses, the perturbative contributions Π pert 5 are known to four-loop order in the MS scheme [3]. Divergent polynomials in Q 2 are ignored in (3) since they correspond to subtraction constants in dispersion relations which do not contribute to sum-rules.In the QCD sum-rule approach, nonperturbative effects are parametrized by the QCD condensates representing infinite correlation-length vacuum effects [1]. In addition to the QCD condensate contributions, scalar and pseudoscalar correlation functions must also take into account the effects of instantons which represent vacuum effects 1

The suitability of the Thin-Film RDE (TF-RDE) technique to rigorously evaluate stability measurements for the oxygen evolution reaction (OER) was recently questioned. The main issue was the inability to deconvolute bubble blockage of catalytic active sites from catalyst dissolution using the TF-RDE technique. It is also possible that the low-loading of TF-RDE OER catalysts exacerbates the effect of bubble blockage. In this work, the modified rotating disk electrode (MRDE) is used with commercial catalyst coated membranes (CCMs) to evaluate catalyst stability. The MRDE may be better suited for stability measurements, since the CCM samples used can better avoid experimental artifacts and can explore much higher current densities than a TF-RDE. Thicker catalyst layers have good adhesion to the membrane, making experimental artifacts less pronounced in stability measurements. Three different stability protocols are used to study the effect of cycling, lower/upper potential limits, and regeneration. The protocol which induced the most irreversible degradation was the square-wave voltammetry (SWV) cycling between 0.05–2.0 VRHE. This irreversible degradation is likely the result of catalyst dissolution. The importance of differentiating between irreversible and reversible degradation is highlighted as a potential future standard for stability evaluation.

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Dieser Aufsatz befasst sich mit den technischen Herausforderungen, wissenschaftlichen Grundlagen, neuen Entwicklungen und Perspektiven auf dem Gebiet der Stabilität und Degradation von OER‐Katalysatoren (OER=Sauerstoffentwicklungsreaktion) an Elektrolyseuranoden in saurer Umgebung. Vorrangig wird der Betrieb auf Basis von Membran‐Elektrode‐Einheiten betrachtet. Zuerst wird der Begriff “Katalysatorstabilität” diskutiert; weitere Themen sind die aktuellen Leistungsziele sowie die Hauptmechanismen der Katalysatordegradation und Strategien zu deren Verminderung. Anschließend werden geeignete In‐situ‐Methoden für die Untersuchung der Katalysatordegradation bewertet und Entwicklungen bei der Abstimmung der OER‐Katalysatorstabilität beschrieben. Abschließend wird die Bedeutung allgemeingültiger Kennzahlen für die Stabilität diskutiert, und es wird ein umfassender beschleunigter Alterungstest vorgeschlagen, der vergleichbare Leistungsdaten für verschiedene Laborbedingungen und Katalysatortypen liefert. Ziel ist es, die Beziehungen zwischen Struktur, Zusammensetzung und Stabilität von OER‐Katalysatoren bei verschiedenen Betriebsbedingungen aufzuzeigen.