Following Adsorbate Coverage on Anodes of High‐Temperature Polymer Electrolyte Membrane Fuel Cells in the Presence of CO and H₂O by using In Operando X‐ray Absorption Spectroscopy

Abstract

Application of the Δμ X‐ray absorption near‐edge spectroscopy analysis technique to a polybenzimidazole‐membrane‐based high‐temperature (170 °C) polymer electrolyte membrane fuel cell (PEMFC) under varying conditions reveals binding‐site details for H, CO, and biphosphate on a platinum nanoparticle anode surface. A synergistic interplay between CO and biphosphate adsorption is found, so that with increasing CO in the gas feed (below 3–4 % in H2), an increased biphosphate coverage becomes visible, apparently because small amounts of adsorbed CO force more localization of the phosphate species, which is believed to be adsorbed on top of the existing H overlayer. Increasing the concentration of CO (well above 4 %) causes CO poisoning to takeover and dramatically decrease the activity, though, compared to low‐temperature PEMFCs, huge amounts of CO can still be tolerated. Adding small amounts of water (less than 7 mg min−1) with CO to the anode feed reduces the amount of adsorbed phosphate and, thereby, increases the activity.

The Stability Challenges of Oxygen Evolving Catalysts: Towards a Common Fundamental Understanding and Mitigation of Catalyst Degradation

“…In these studies, a full PEM electrolyzer setup is not an ideal test apparatus because of the large number of components and the overall complexity involved. A reported PEM fuel cell setup for use in in situ EXAFS may be applicable to PEM electrolysis if the necessary water film for operation can be kept sufficiently thin (≤1 μm) to avoid total absorption of the beams . Synchrotron‐based in situ variations of X‐ray absorption spectroscopy (XAS) such as extended X‐ray absorption fine structure (EXAFS) and X‐ray absorption near‐edge spectroscopy (XANES) as well as X‐ray photoelectron spectroscopy (XPS) can help identify changes in the catalyst structure as well as surface species during and after catalysis.…”

“…Areported PEM fuel cell setup for use in in situ EXAFS may be applicable to PEM electrolysis if the necessary water film for operation can be kept sufficiently thin ( 1 mm) to avoid total absorption of the beams. [136] Synchrotron-based in situ variations of X-ray absorption spectroscopy (XAS) such as extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge spectroscopy (XANES) as well as X-ray photoelectron spectroscopy (XPS) can help identify changes in the catalyst structure as well as surface species during and after catalysis.X AS is suitable for investigating ill-defined and amorphous materials because it does not depend on the presence of long-range order.A ss uch, it is an ideal local probe for many of the OER catalysts whose active state(s) appear to be quite amorphous in structure.…”

Carbon monoxide poisoning and mitigation strategies for polymer electrolyte membrane fuel cells – A review

“…(2015) applied Δµ adsorption near-edge spectroscopy (XANES) to reveal details of the binding-site for H, CO and biphosphate on the platinum anode catalyst that contributes to the better performance of HT-PEMFC in the presence of CO. 244 Another example is the use of the H2-D2 switch with Ar purge (HDSAP) method to study the effect of humidity on contamination. 226,227 Computational and modelling methods, often combined with experimental validation, are being more extensively applied to derive new insights and optimise mitigation techniques.…”

Stabilitätsanforderungen von Elektrokatalysatoren für die Sauerstoffentwicklung: der Weg zu einem grundlegenden Verständnis und zur Minimierung der Katalysatordegradation

“…Angesichts der hohen Komplexität und großen Anzahl beteiligter Komponenten eignet sich ein Aufbau mit vollständigem PEM‐Elektrolyseur für solche Studien nicht. Ein gängiger PEM‐Brennstoffzellen‐Aufbau für die In‐situ‐EXAFS‐Untersuchung ließe sich auf die PEM‐Elektrolyse übertragen, sofern der für den Betrieb notwendige Wasserfilm so dünn (≤1 μm) ist, dass die Strahlung nicht vollständig absorbiert wird . In‐situ‐Techniken mit Varianten der Röntgenabsorptionsspektroskopie (XAS) und Synchrotronstrahlung, wie die Analyse der kantennahen Feinstruktur eines Röntgenspektrums (EXAFS), Röntgen‐Nahkanten‐Absorptions‐Spektroskopie (XANES) und Röntgenphotoelektronenspektroskopie (XPS), können für die Identifizierung von Veränderungen in der Katalysatorstruktur und von Oberflächenspezies während und nach der Katalyse sinnvoll sein.…”