Collaborative Research: Addressing Morphological Instability in Topologically Complex Electrocatalytic Nanostructures

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Non-Technical Summary:Commercialization of renewable energy storage and conversion devices, such as water electrolyzers and fuel cells, requires advancements in both efficiency and operational longevity. Performance as well as cost of these electrochemical energy devices is strongly tied to the electrocatalyst materials that drive the reactions producing energy or fuel. Electrocatalyst materials development has centered on the design of nanoscale catalysts that maximize the exposure and usage of precious metals, i.e. Platinum, of which they are composed. These unique nanoscale architectures, however, are susceptible to multiple mechanisms of degradation, the rate of which is typically inversely proportional to the activity of the catalyst. The goal of this project is to highlight these mechanisms of degradation for electrocatalysts possessing complex nano-architectures. With a better understanding of how these materials degrade, mitigation strategies can be proposed, improving durability and breaking away from the inverse proportional relationship between electrocatalyst activity and durability. Insight developed through the proposed work will have a significant impact on the effort to bridge the gap between highly active and highly stable materials where integration of these morphologically stable yet complex and active electrocatalysts into electrochemical energy conversion and storage devices will yield significant improvements in both precious metal loading and device operational longevity. The proposed work will provide one PhD student and several undergraduate students with a broad and interdisciplinary research experience in interfacial electrochemistry and nanomaterial synthesis for renewable energy technologies. Through a partnership with the Lindy Center at Drexel, the PI will highlight the principles of renewable and carbon neutral energy storage and conversion and promote interest in STEM for grade 4-12 community members.Technical Summary:This project will investigate the mechanisms by which three-dimensional, porous, morphologically complex electrocatalytic nanomaterials degrade under relevant electrochemical conditions. The products of this proposed research will highlight the limiting atomic processes and provide insight for the development of mitigation strategies that maintain morphological and compositional integrity with negligible impact on the intrinsic activity of the catalysts. The research objective of the proposed work is to develop a more detailed fundamental understanding of the convolution of electrochemical dissolution and surface diffusion driven coarsening for these three-dimensional nanomaterials that are in a constant state of meta-stability. It is hypothesized that electrochemical coarsening is driven by a dissolution/redeposition process rather than a pure surface diffusion driven process. Through a combination of experimental, local and global measurements, and computational analysis, this project will qualitatively and quantitatively assess the impact of relevant operational parameters on the morphological and compositional evolution of nanoporous materials. This proposed concept has a broad parameter space, composed of a complex web of intertwined interactions. Computational manipulation of this parameter space, through kMC, will be used to explore the underlying physics of electrochemical coarsening: a) the distance along the surface the dissolved species travels before redepositing, b) response time of dissolution and deposition, c) flux of local dissolution for a given UPL, d) the coordination of the preferred defect site, e) flow rate of electrolyte solution (simply by a time-dependent removal of dissolved species), and f) type of surface impurity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.