Optimization of Time-of-Flight Secondary Ion Mass Spectrometry for Analysis of Porous Transport Layers

As we move towards commercialization of the proton exchange membrane water electrolyzers (PEMWEs), fundamental understandings of individual components and their integration with focus on material composition and its correlation to performance and lifetime of electrolysis cell operation is of significant importance. Porous Transport Layers (PTLs) increase overpotential of the cell when the titanium passivates, i.e. develops a titanium oxide surface layer of a certain thickness. To prevent this passivation, platinum group metal coatings are typically applied to the PTL, but this adds significant costs. This presentation will cover recent developments in characterization of PTL coatings and PTL-coating interfaces using Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) in correlation with Scanning Transmission Electron Microscopy and Energy Dispersive X-ray Spectroscopy (STEM-EDS) analysis. Although this technique is extremely beneficial, ToF-SIMS is typically applied to flat substrates and therefore has been mainly utilized in other scientific fields such as the thin film industry. This talk will discuss method validation and optimization that has been conducted for PTL analysis to allow its characterization by ToF-SIMS. Topics include understanding parameters and limitation of using SIMS on these morphologically challenging samples, as well as looking at elemental and species identification, and applying depth profiling to gauge information on coating and oxide thickness and their consistency. Correlations between real and flat substrates prepared under similar conditions are made, allowing standardization of depth profiling for future analysis of a wider variety of samples.