Yazar "Zhao, Yuxin" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • Küçük Resim
    Öğe
    Atomically dispersed zeolite-supported rhodium complex: Selective and stable catalyst for acetylene semi-hydrogenation
    (Elsevier, 2024) Kurtoğlu-Öztulum, Samira Fatma; Zhao, Yuxin; Hoffman, Adam S.; Uzun, Alper; Demircan, Oktay; Yordanli, Melisa Su; Hong, Jiyun; Perez-Aguilar, Jorge E.; Saltuk, Aylin; Akgül, Deniz; Ateşin, Tülay A.; Aviyente, Viktorya; Gates, Bruce C.; Bare, Simon R.
    Supported rhodium catalysts are known to be unselective for semi-hydrogenation reactions. Here, by tuning the electronic structure of supported mononuclear rhodium sites determined by the metal nuclearity and the electron-donor properties of the support, we report that atomically dispersed HY zeolite-supported rhodium with reactive acetylene ligands affords a stable ethylene selectivity > 90 % for acetylene semi-hydrogenation at 373 K and atmospheric pressure, even when ethylene is present in a large excess over acetylene. Infrared and X-ray absorption spectra and measurements of rates of the catalytic reaction complemented with calculations at the level of density functional theory show how the catalyst performance depends on the electronic structure of the rhodium, influenced by the support as a ligand that is a weak electron donor.
  • Küçük Resim
    Öğe
    Reduced graphene aerogel-supported Ir(C2H4)2 complexes at an exceptional Ir loading of 23.8 wt%: Confirming site-isolation by combining XAS and STEM
    (Turkish Catalysis Society, 2023) Kurtoğlu-Öztulum, Samira Fatma; Yalçın, Kaan; Zhao, Yuxin; Ünal, Uğur; Uzun, Alper
    Atomically dispersed supported metal catalysts offer significant opportunities when compared to conventional analogues. They provide maximum utilization of expensive noble metals, interesting catalytic properties, and understanding of structure-catalytic activity relationships [1]. These novel catalysts consist of supported single metal atoms bonded to ligands as well as clusters incorporating only a few metal atoms. However, they face certain challenges hindering their industrial use. The main challenges are their limited stability and limited metal loading. Typical metal loadings are limited with <1 wt.%. The support material is crucial in overcoming these challenges. Here, we used reduced graphene aerogel (rGA) as a novel support for Ir(C2H4)2 complexes and assessed the maximum metal loading we can reach. Thanks to the outstanding properties of rGA, such as excellent electronic properties, high porosity and surface area, and multiple bonding sites for Ir atoms, an exceptionally high Ir loading of 23.8 wt% was obtained. Aberration-corrected scanning transmission electron microscopy (STEM) images and X-ray absorption spectroscopy (XAS) data confirmed the site-isolation of Ir atoms at this exceptional loading. Figure 1 shows the STEM images of rGA-supported Ir(C2H4)2 complexes at an Ir loading of 23.8 wt%, a challenging sample because of the three-dimensional multilayer wrinkled-sheet structure of rGA. Besides, these images are one of the first atomic resolution images obtained on a Hitachi HF5000 Cs-corrected cold FEG STEM in Koç University. Results demonstrate the potential of rGA as a superior support material for expensive noble metal complexes to reach exceptional loadings.