Nano textured core-shell carbide-derived carbon particles for electrochemical energy storage and electrocatalysis (COSH-CDC)

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In this project, we will synthesize core/shell hybrid materials for electrochemical applications, based on a novel two-step synthesis that we have recently developed. Using a metal carbide powder, our approach is to first achieve partial transformation of the outer part of the granular material to carbide-derived carbon (CDC) by chlorination. The second step employs either calcination of the residual core (yielding metal oxide for energy storage applications), or a second chlorination step (yielding a carbon core with a porosity very different from the shell for electrocatalysis). The key of partial transition of carbide-to-CDC is the use of homogenously distributed NiCl2, yielding a highly controllable in situ formation of chlorine gas in a precisely tuned stoichiometric ratio. The use of different metal carbides, namely, TiC, VC, NbC, and Mo2C, enables us to design different metal oxide cores (for energy storage) or different porosities of the core (for electrocatalysis).Recent joint work of the two PIs has established the feasibility of both core/shell designs, namely, metal oxide / CDC and CDC/CDC core shell particles. Yet, a systematic and comprehensive understanding of structure/property correlations and surveying of the electrochemical properties is still missing. Bringing the key expertise of synthesis, electrochemical energy storage, and electrocatalysis of the Etzold Group (TU Darmstadt) and Presser Group (INM Saarbrücken), we will be able to create synergistic added value and provide for the project-involved PhD students a vibrant collaborative research environment to broaden their knowledge beyond a selected electrochemical application.Electrochemical energy storage of our core/shell particles will capitalize on the high charge storage capacity of the metal oxide core, which can only be utilized because of the high electrical conductivity of the mesoporous carbon shell. By this way, no additional conductive additive is required to be added and possibly high power handling can be enabled. Having a metal oxide core and a carbon shell is also different from a large amount of current hybrid material works, where the metal oxide is grown on top of the carbon substrate. We will investigate aqueous and non-aqueous electrolytes to study the hybrid materials' redox-activity and lithium ion intercalation ability.For electrocatalysis, platinum will be deposited on the hierarchically structured carbons with graphitic and mesoporous shell and microporous and amorphous cores. The influence of the special carbon architecture on cathode (oxidation reduction reaction) and anode site (hydrogen oxidation reaction; methanol oxidation reaction) fuel cell reactions will be studied. Thereby improved performance is expected as the core facilitates a high dispersion and thus activity of the catalyst, while the shell improves with its mesoporosity the mass transfer and reduces with its graphitic character the Ohmic resistance.