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Projekt Druckansicht

Einfluss der Katalysator-Träger-Wechselwirkung auf die Aktivität und Stabilität von Wasserspaltungs-Katalysatoren

Fachliche Zuordnung Herstellung und Eigenschaften von Funktionsmaterialien
Förderung Förderung von 2019 bis 2023
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 424873219
 
Erstellungsjahr 2024

Zusammenfassung der Projektergebnisse

In this project, we studied the role of the interface between catalyst and substrate in photoelectrochemical (PEC) devices used for the OER. We investigated the PEC prototype catalyst|support systems Ti/TiOx and Ti/TiOx/M (M = Au, Ni, Fe) with NiFe layered double hydroxides (NiFe LDH) on top. The metal interlayer M leads to a 100-fold increase of the OER current. We employed electrochemical voltammetry and impedance methods as well as x-ray spectroscopic methods on drop casted NiFe LDH and compared results with NiFeOx thin film model systems. With ex-situ and in-situ methods, we show that both the NiFe LDH as well as the thin film systems undergo comparable transitions of the starting catalyst material into the highly active (oxy)hydroxide phase, when using metallic interlayers. In parallel with this activation, the interface between catalyst and metal modified substrate becomes permissive to currents. It is known that the higher oxidized (oxy)hydroxide phases are more conductive, however, we could not finally conclude whether an initial better interface conductivity between substrate and catalyst leads to a better catalyst conversion or if instead an initially better interface coupling alignment allows for an efficient conversion of the catalyst. We have shown that our interface experiments on thin-film model systems are representative for more complicated practical electrolysis structures, and they provide more detailed insight into the electronic coupling between substrate, metal interlayer and catalyst. However, the exact mechanism for the better OER performance of these systems stays elusive, yet. Related to the molecular systems for the hydrogen evolution reaction (HER), variations in the ligand environment, metal center and on substituents were performed to unravel the dominating factor for the catalytic activity. Based on the results, it can be generalized that Cobased systems outperform Fe-based systems by almost 100 mV less overpotential. In order to enable in-situ and operando spectroscopy, pre-tests were performed with a flow cell. However, further improvement was obtained by changing from Mössbauer spectroscopy to NFS. On the basis of these results, we were able to determine the intermediate that is formed prior to the rate determining step. In order to gain insights on the role of the support, three different supports were used. The comparison of the electrochemical data and the vibrational spectra after pyrolysis in a temperature range from 600 – 800 °C indicate that in parallel to the increase in performance also the binding strength of the metal center towards the surround matrix became stronger. The analysis of the corresponding in-situ data is still ongoing but will help to conclude on similarities and differences of the pyrolyzed MNC in comparison to nonpyrolyzed porphyrinic systems.

Projektbezogene Publikationen (Auswahl)

 
 

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