Development and Application of a Flexible Synthesis for Unprotected Colloidal Pt Nanoparticles as a Platform for Systematic Degradation Studies in Electrocatalysis

• Applicant: Professor Dr.-Ing. Bastian Etzold, since 12/2018
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 354106573

The direct use of H2 as an energy carrier is one possible scenario for the switch from nuclear power and fossil fuels to regenerative energy. The fuel cell technology is thereby of significant relevance and the optimization of activity and stability are essential challenges in order to foster their applicability. While the catalytic activity has been investigated quite intensively in the past and active material have been developed, knowledge about relations between the catalyst properties and the stability are still scarce. The primary goal for the proposed project is to establish a preparation platform that enables for systemic investigations of the influence of the most relevant catalyst properties (particle size, loading, and support) on the performance and hence also the catalyst stability. For state-of-the-art fuel cell catalysts (carbon supported Pt nanoparticles) this task can basically be addressed using so-called unprotected Pt nanoparticles (NPs). Such NPs are synthesized as colloids in alkaline ethylene glycol. The application of further preparation steps enables for depositing these particles onto every type of support material. As a result support and particle loading can be controlled independently. However, the application of unprotected NPs is still hindered by the limited control over particle size. Any attempt to achieve particle size control by thermally driven preparation protocols did not give any satisfying results. However, recent investigations have shown that unprotected NPs can also be synthesized using photochemical methods. This so far unexplored potential for controlling the synthesis of unprotected NPs shall be investigated within the proposed project in order to achieve an appropriate particle size control. Such a synthesis protocol will ultimately enable for investigating systematically and independently the influence of the catalytically relevant material properties (particle size, loading, and support).For fuel cells different degradation mechanisms have been identified. The dependence of these mechanisms on the particle size and particle loading of the catalyst has however still not been determined. Therefore, the second part of the project will focus on this topic by using the previously developed synthesis protocol. Model catalysts will be prepared by deposition of the NPs onto TEM grid carbon films. Furthermore, the application of STEM (scanning transmission electron microscopy) as an experimental tool is planned in order to establish an automated, fast method for performing particle size analyses. In contrast to the established methodology of IL-TEM (identical location transmission electron microscopy) the use of STEM enables not merely for local analysis but also for investigating larger areas within a reasonable time frame. This will perspectively allow not merely for qualitative but also quantitative conclusions regarding the relevance of individual degradation mechanisms.

• DFG Programme: Research Grants
• Ehemalige Antragsteller: Professor Dr. Marcus Bäumer, from 9/2018 until 11/2018; Dr. Sebastian Kunz, until 8/2018