MXene-based energy materials guided by 3D Atomic-Resolution Tomography

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The efficiency of devices for green energy conversion, i.e. fuel cells and electrolyzers for hydrogen generation, is dependent on catalysts, materials that accelerate the rate of desired chemical reactions. The catalytic sciences are undergoing a revolution as scientists are pushed to focus on improving durability and reducing price rather than just maximizing activity. Such benchmarks are only achievable by the discovery of new materials and establishing processing-structure-property relationships at the atomic scale. MXenes, discovered in 2011, are the latest and least understood two-dimensional (2D) materials. They derive their name from their parent Mn+1AXn (“MAX”) phases where M is an early transition metal, A is an A-group element, X is carbon and/or nitrogen, and n = 1–3. Recent theoretical papers have predicted the suitability of MXenes as low-cost catalysts for energy applications, but a robust experimental validation of these studies does not exist. This project aims to tailor MXenes for energy conversion applications, and extract atomic-scale structural and chemical insights about their stability, using atom probe tomography (APT) and high-resolution electron microscopy. The Sokol group will synthesize novel MXenes by wet chemistry, whereas the Eliaz group will process MXenes by electroplating as well as by state-of-the-art 2D patterning and 3D printing. APT and other advanced analytical techniques will be used by the Raabe and Gault groups to characterize the chemistry and structure of these materials, before and after catalytic testing by the Rosen group. Thermal desorption spectroscopy (TDS) will be used in order to detect residues of hydrogen and oxygen in the catalyst as well as to determine the binding energy between hydrogen atoms and microstructural traps in MXene-based materials. A correlation will be made with electron microscopy and APT to determine hydrogen trapping sites and how catalytic and material properties are influenced. The Raabe and Eliaz groups will study hydrogen- and oxygen-induced degradation of the catalyst materials, which will be correlated with results from APT to better understand how to optimize their lifetime. Thus, our team will combine processing of a newly discovered class of materials (MXenes) in different ways, with catalytic testing, and state-of-the-art atomic resolution characterization to tackle one of the grand challenges of our generation.