Imaging and Characterization Core Lab

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  • Article

    Brønsted Acid-Site Density Controls the Mechanistic Cycle and Product Selectivity in the Methanol-to-Hydrocarbons Reaction in BEA Zeolite

    (American Chemical Society (ACS), 2024-04-05) Navarro de Miguel, Juan Carlos; Chung, Sang-Ho; Dikhtiarenko, Alla; Li, Teng; Patarroyo, Javier; Ruiz-Martinez, Javier; Imaging and Characterization Department, KAUST Core Laboratories, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia; Catalysis Research Center; KAUST Catalysis Center (KCC); Physical Sciences and Engineering; Physical Science and Engineering (PSE) Division; Physical Characterization; Water Desalination & Reuse Center; Water Desalination and Reuse Research Center (WDRC); Biological, Environmental Sciences and Engineering; Biological and Environmental Science and Engineering (BESE) Division; Chemical Engineering; Chemical Engineering Program; Imaging & Characterization Core Lab; Imaging and Characterization Core Lab

    In this work, we show that the acid-site density controls the dominant cycle during the methanol-to-hydrocarbons reaction on beta zeolite. Our experimental evidence is based on the study of beta zeolites with very similar diffusional pathways and different aluminum content. High selectivity to propylene was observed for samples with low Brønsted acid-site density, which is a consequence of the promotion of the olefinic cycle. Our results also confirm that the production of ethylene via the olefinic cycle is negligible. In contrast, high ethylene and aromatics are found at a high Brønsted acid-site density, highlighting the predominancy of the aromatic cycle. Operando UV–vis data show that monoenylic carbocationic species predominate on the olefinic cycle, whereas the aromatic cycle is dominated by polyalkylated monoaromatics. Analysis of the spectroscopy data also shows a linear correlation of the formation of polyaromatic species with the Brønsted acid-site density.

  • Article

    Revealing the effect of cobalt content and ligand exchange in the bimetallic Ni–Co MOF for stable supercapacitors with high energy density

    (Elsevier BV, 2024-04-03) Raissa,; Wulan Septiani, Ni Luh; Wustoni, Shofarul; Failamani, Fainan; Wehbe, Nimer; Eguchi, Miharu; Nara, Hiroki; Inal, Sahika; Suendo, Veinardi; Yuliarto, Brian; Imaging and Characterization Core Labs, KAUST, Thuwal, 23955-6900, Saudi Arabia; Biological, Environmental Sciences and Engineering; Biological and Environmental Science and Engineering (BESE) Division; Surface Science; Bioengineering; Bioengineering Program; Imaging & Characterization Core Lab; Imaging and Characterization Core Lab; Doctoral Program of Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung, Bandung, 40132, Indonesia; Department of Chemistry, Faculty of Science and Computer, Universitas Pertamina, Jakarta, 12200, Indonesia; Research Center for Advanced Materials, National Research and Innovation (BRIN), Komplek Puspiptek, South Tangerang, 15314, Indonesia; Advanced Functional Materials Research Group, Faculty of Industrial Technology, Institut Teknologi Bandung (ITB), Bandung, 40132, Indonesia; Department of Chemistry, Faculty of Mathematics and Natural Science, ITB, Bandung, 40132, Indonesia; Faculty of Science and Engineering, Waseda University, Shinjuku, Tokyo, 169-8555, Japan; International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan; Research Organization for Nano & Life Innovation, Waseda University, 513 Wasedatsurumakicho, Shinjuku, Tokyo, 162-0041, Japan; Research Center for Nanosciences and Nanotechnology (RCNN), ITB, Bandung, 40132, Indonesia

    Metal-organic frameworks (MOF) exhibit considerable potential as electrode materials for supercapacitors. Nevertheless, the electrochemical performance of the MOF is impeded by its low electrical conductivity and chemical stability. In this study, we investigate the impact of cobalt composition and ligand exchange on the performance of bimetallic NiCo-MOF to unlock its optimal performance. Our results reveal that integrating cobalt affects the abundance of Ni3+ and Co2+, which serve as electrochemical active species. Additionally, ligand exchange with a phosphate group leads to further modifications in both abundance and surface area. The result indicates that a Ni/Co ratio of 10:1 in NiCo-MOF exhibits superior performance (437 C g−1 at 0.5 A g−1), surpassing the performance of other ratios. Furthermore, the process of ligand exchange in NiCo-MOF with a Ni/Co ratio of 10:1 yields an even higher capacity of 522 C g−1 at 0.5 A g−1, with an energy density of 22 Wh kg−1 at 363 W kg−1 when assembled in an asymmetric supercapacitor cell. The supercapacitor cell demonstrates a remarkable capacity retention of 99 % at 5 A g−1 over 5000 cycles. This study provides insight into the pivotal role of cobalt composition and ligand exchange in improving the electrochemical performance of NiCo-MOF.

  • Article

    Temperature stability of perovskite-structured lead-free piezoceramics: evaluation methods,improvement strategies, and future perspectives

    Lv, Xiang; Wang, Xin; Ma, Yinchang; Zhang, Xixiang; Wu, Jiagang; Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal, 239955, Kingdom of Saudi Arabia; Material Science and Engineering; Material Science and Engineering Program; Core Labs and Research Infrastructure; Imaging & Characterization Core Lab; Imaging and Characterization Core Lab; Physical Sciences and Engineering; Physical Science and Engineering (PSE) Division; College of Materials Science and Engineering, Sichuan University, Chengdu 610065, P. R. China

    Due to ever-increasing environmental concerns, lead-free piezoceramics have been studied for more than half a century with the purpose of replacing toxic lead-based counterparts. A series of notable breakthroughs have been reported in perovskite-structured lead-free piezoceramics, such as ultra-high piezoelectric and strain properties. By contrast, the development of the temperature stability of lead-free piezoceramics has left far behind and has always been the one of the biggest hindrances for practical applications. In this context, we have summarized the most cutting-edge advances in the temperature stability of perovskite-structured lead-free piezoceramics. We first emphasized the measurement methods of evaluating temperature stability, then summarized the regulating strategies (including phase boundary engineering, texturing, composite ceramics, defect engineering, quenching, and others) used for improving the temperature stability of these lead-free piezoceramics, and addressed the physical mechanisms from a multi-scale view. Finally, we concluded advantages and disadvantages of these strategies and provided our perspective on the challenges and future research of the temperature stability. We hope that this timely review could help the development of the temperature stability of lead-free piezoceramics towards practical applications.

  • Article

    Strategies for high-temperature methyl iodide capture in azolate-based metal-organic frameworks

    (Springer Nature, 2024-03-23) Pan, Tingting; Yang, Kaijie; Dong, Xinglong; Zuo, Shouwei; Chen, Cailing; Li, Guanxing; Emwas, Abdul-Hamid M.; Zhang, Huabin; Han, Yu; Chemistry; Chemical Science Program; Physical Sciences and Engineering; Physical Science and Engineering (PSE) Division; Water Desalination & Reuse Center; Water Desalination and Reuse Research Center (WDRC); Biological, Environmental Sciences and Engineering; Biological and Environmental Science and Engineering (BESE) Division; Catalysis Research Center; KAUST Catalysis Center (KCC); Advanced Membranes and Porous Materials Center; Advanced Membranes and Porous Materials Research Center; NMR; Imaging & Characterization Core Lab; Imaging and Characterization Core Lab; School of Chemistry, University of Lincoln, Brayford Pool, Lincoln, United Kingdom; School of Emergent Soft Matter, South China University of Technology, Guangzhou, China; Center for Electron Microscopy, South China University of Technology, Guangzhou, China

    Efficiently capturing radioactive methyl iodide (CH3I), present at low concentrations in the high-temperature off-gas of nuclear facilities, poses a significant challenge. Here we present two strategies for CH3I adsorption at elevated temperatures using a unified azolate-based metal-organic framework, MFU-4l. The primary strategy leverages counter anions in MFU-4l as nucleophiles, engaging in metathesis reactions with CH3I. The results uncover a direct positive correlation between CH3I breakthrough uptakes and the nucleophilicity of the counter anions. Notably, the optimal variant featuring SCN- as the counter anion achieves a CH3I capacity of 0.41 g g−1 at 150 °C under 0.01 bar, surpassing all previously reported adsorbents evaluated under identical conditions. Moreover, this capacity can be easily restored through ion exchange. The secondary strategy incorporates coordinatively unsaturated Cu(I) sites into MFU-4l, enabling non-dissociative chemisorption for CH3I at 150 °C. This modified adsorbent outperforms traditional materials and can be regenerated with polar organic solvents. Beyond achieving a high CH3I adsorption capacity, our study offers profound insights into CH3I capture strategies viable for practically relevant high-temperature scenarios

  • Article

    Shaping technical catalyst particles in a bottom-spray fluidized bed

    (Elsevier BV, 2024-03) Alkadhem, Ali; Mohamed, Hend Omar; Kulkarni, Shekhar Rajabhau; Hoffmann, Torsten; Zapater, Diego; Musteata, Valentina-Elena; Tsotsas, Evangelos; Castano, Pedro; Multiscale Reaction Engineering, KAUST Catalysis Center (KCC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia; Chemical Engineering Program; Physical Science and Engineering (PSE) Division; KAUST Catalysis Center (KCC); Electron Microscopy; Imaging and Characterization Core Lab; Thermal Process Engineering, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany

    This work aims to elucidate the particle growth mechanism during agglomeration using a bottom-spray fluidized bed process to produce technical catalysts. The influences of the fundamental operating parameters of the granulation process were investigated through (i) experiments in a newly designed small-scale bottom-spray fluidized bed reactor, (ii) morphological characterization of the catalytic particles produced, (iii) dimensionless number analysis, and (iv) principal component analysis. These results could define the growth stage as dust formation, seed formation, agglomeration, and dust integration or layering. The particle growth mechanism results from the complex interplay of several effects and forces (mass transfer, viscous force, inertial force, surface tension, and gravity), and the prevailing growth stage can be linked with the Weber (We) and capillary (Ca) numbers (i.e., low values of We = 5.7 and Ca = 1.4 leads to layering growth and high values of We = 19.1 and Ca = 7.1 results in dust formation).