(Invited) Traversing Length Scales for Electrochemical Hydrogen Production and Use: Developing a Platform for Material Design and in Situ Material Characterization of Electrocatalysts
Authors: Burke Stevens Michaela 
Published: August 2024

Converting chemical processing to carbon-free or to closed carbon cycle processing (e.g. carbon neutral) will require large quantities of sustainable, and likely electrically produced, fuels and processes. Hydrogen is both a chemical fuel alternative, but also an important commodity for chemical manufacturing e.g. ammonia production for fertilizers. Water electrolyzers (WE) and hydrogen fuel cells (H2FCs) for either making or converting hydrogen to electrical energy will require cheaper and more readily available catalyst materials than the current platinum or iridium based state-of-the-art. Alkaline zero-gap devices (anion exchange membrane, AEM WE or H2FCs) offer a promising landscape for earth abundant materials, however they have traditionally underperformed due to large scale component instabilities, e.g. membranes, ionomer, catalysts, etc. With recent advances in alkaline membrane technology it is imperative that commercializable catalysts are developed. Due to a variety of architectural differences, the dissimilar microenvironments and catalyst-electrolyte-gas interfaces between classical fundamental (e.g. three electrode cell measurements with a rotating disc electrode (RDE) and device studies makes it difficult to translate materials to industrial readiness. It is imperative that these trends translate from the small lab-scale (mA), an environment that engenders rapid catalyst evaluation, to industrial-relevant scales (> A) in multi-variable devices.
Herein I will discuss work we have done both on developing a robust a platform for measuring performance trends across length scales and microenvironments and expanding tools for characterizing in situ material stability related primarily to WE and H2FCs. For H2FCs, I will discuss our teams’ recent work translating Ag-Pd catalysts from first principles with density function theory (DFT), to classic fundamental studies with RDEs, and finally to H2FCs with a max ~ 10 W/mgPGM on the cathode.1,2 I will discuss the thin film, ionomer-free system that extended across length scales and microenvironments and how we are currently using this platform to develop Ag-based fully non-platinum group metal catalysts. Comparing both H2FCs and WEs, I will go on to discuss one large component of performance, stability, and our ongoing efforts to develop tools for in situ characterization. On-line inductively coupled plasma mass spectrometry (on-line ICP-MS) and electrochemical mass spectrometry (EC-MS) are emerging tools for monitoring material dissolution and product production, respectively, in real time. By coupling these techniques, looking at Co-based metals we have identified degradation mechanisms as well as windows of stable hydrogen evolution and oxygen reduction catalysis in highly acidic electrolytes. A focus on catalyst activity and nature of the active site across microenvironments and in situ material stability provides insights that could enable the next generation materials and stabilization techniques, e.g. in situ, synthetic, morphology, etc. for improving overall performance across technological length scales.

References

1) Zamora Zeledón, J. A.; Stevens, M.B.; Gunasooriya, G.T.K.K.; Gallo, A.; Landers, A.T.; Kreider, M.E.; Hahn, C.; Nørskov, J.K.; Jaramillo, T.F. Tuning the Electronic Structure of Ag-Pd Alloys to Enhance Performance for Alkaline Oxygen Reduction, Nature Comm.,
2021, 12, 1-9.
2) Douglin, J.C.; Zamora Zeledón, J. A; Keider, M. E; Singh, R.K.; Stevens, M.B. ‡ Jaramillo, T. F. ‡ Dekel, D.R. ‡ High performance anion-exchange membrane fuel cells with ionomerless cathodes employing ultra-low loading Ag-Pd alloy electrocatalysts, Nature Energy, 2023, 1-11.