Universität Stuttgart

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Institute: search.filters.UBSInstitut.Max-Planck-Institut für FestkörperforschungAuthor: search.filters.author.Klemm, Elias

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    ItemOpen Access
    Investigating the long-term kinetics of Pd nanoparticles prepared from microemulsions and the Lindlar catalyst for selective hydrogenation of 3-hexyn-1-ol
    (2024) Tari, Faeze; Hertle, Sebastian; Wang, Hongguang; Fischer, Julian; Aken, Peter A. van; Sottmann, Thomas; Klemm, Elias; Traa, Yvonne
    The effect of non-saturated corner and edge sites of Pd particles on the long-term selectivity of cis-3-hexen-1-ol in the hydrogenation of 3-hexyn-1-ol was studied in this work. Non-supported Pd agglomerates were synthesized through the microemulsion synthesis route and used at  nalkynol/APdratios between 0.08 and 21 mol/m2for the catalytic conversion of 3-hexyn-1-ol for 20 h. The selectivity of the cis-hexenol product increased by reducing the quantity of Pd catalytic sites (increasing the nalkynol/APdratio) without introducing any modifier or doping agent to poison the nonselective sites. Then, Pd aggregates with fused primary particles and, thus, fewer corner and edge sites were produced through thermal sintering of the agglomerates at 473-723 K. By comparing the catalytic performance of the agglomerates and aggregates, it was observed that at a rather similar kinetic behavior (99.99% conversion and 85-89% selectivity to cis-hexenol), the sintered aggregates could stay selective despite a catalytic surface area about seven times larger. This emphasizes the role of low-coordinated edge and corner sites on the final selectivity of the cis product and demonstrates that thermal sintering allows the number of non-selective sites to be reduced without any need for toxic or organic doping agents or modifiers.
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    ItemOpen Access
    Assembling metal organic layer composites for high‐performance electrocatalytic CO2 reduction to formate
    (2022) Liu, Hang; Wang, Hongguang; Song, Qian; Küster, Kathrin; Starke, Ulrich; Aken, Peter A. van; Klemm, Elias
    2D metal-organic-framework (MOF) based composites have emerged as promising candidates for electrocatalysis due to their high structural flexibility and fully exposed active sites. Herein, a freestanding metal-organic layer (MOL) with a 2D kgd (kagome dual) lattice was constructed with abundant surface oxygenate groups serving as anchoring sites to immobilize diverse guests. Taking Bi as an example, tetragonal Bi2O3 nanowires can be uniformly grown on MOLs after solvothermal treatment, the structural evolution of which was followed by ex situ electron microscopy. The as-prepared Bi2O3/MOL exhibits excellent CO2 electroreduction activity towards formate reaching a specific current of 2.3 A mgBi−1 and Faradaic efficiencies of over 85 % with a wide potential range from -0.87 to -1.17 V, far surpassing Bi2O3/UiO (a 3D Zr6-oxo based MOF) and Bi2O3/AB (Acetylene Black). Such a post-synthetic modification strategy can be flexibly extended to develop versatile MOL composites, highlighting the superiority of optimizing MOL-based composites for electrocatalysis.