Laser-generated Multinary High Entropy Alloy Nanoparticles for Catalytical Applications
Sven Reichenberger, University of Duisburg-Essen, Germany
During the last decade, pulsed laser ablation and processing of colloidal nanoparticles became an established method to study the catalytic activity in terms of functional nanoparticle properties (size, morphology, oxidation state), and material design (metals, oxides, alloys).[1–3] During nano-integration of the nanoparticles on support materials the pre-adjusted nanoparticle properties are maintained which allows both mechanistic4,5 and applicatory studies e.g. in real fuel cell stacks6 or industrial exhaust gas studies7. High entropy alloys (HEAs) are a rather new class of multinary complex solid solution and are already prominent for their high mechanical strength and ductility8 but also gaining increasing attention as energy material in catalysis.4,9 Previous studies have shown the successful synthesis of crystalline high entropy alloy nanoparticles by pulsed laser ablation in ethanol.9 Due to partial surface oxidation in ethanol, acetonitrile was used in the present study to further suppress oxidation4. Increasing atom percentages (6-30 at%) of Mo were added to the MnFeCoNiCr system to study the effect of Mo on the electrocatalytic OER and ORR activity. XRD analysis showed that mainly amorphous HEA nanoparticles were gained when using acetonitrile as a solvent during laser ablation. A significant carbon doping was detected by HR-TEM-EDX and previously discussed to stabilize amorphous nanoparticles during laser-based synthesis3. XPS showed a gradual surface enrichment with Mn and a depletion with Mo. The catalytic investigation delivered pronounced activity trends with the composition where the different optimal contents of Mo resembled opposite trends for OER and ORR7. Overall, the presented study solidifies the feasibility of the scalable laser-based catalyst synthesis in developing new catalytic systems for industrial and scientific applications.
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