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743 results on '"Niemantsverdriet, J.W."'

20. Light-Switchable N-Alkylation Using Amine-Functionalized Mof

Author

Huang, Yu, primary, Li, Yaru, additional, Zhang, Dongsheng, additional, Mai, Yuanqiang, additional, Besenbacher, Flemming, additional, Dong, Chuan, additional, Rosei, Federico, additional, Yang, Yong, additional, Li, Yongwang, additional, Niemantsverdriet, J.W. (Hans), additional, Liang, Wenting, additional, and Su, Ren, additional

Published
2023
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33. Revisiting Oxygen Adsorption on Ir(100)

Author

Cao, Xu, Liu, Chunli, Zhang, Tianfu, Xu, Qian, Zhang, Dongling, Liu, Xiaotong, Jiao, Haijun, Wen, Xiaodong, Yang, Yong, Li, Yongwang, Niemantsverdriet, J.W., Zhu, Junfa, Cao, Xu, Liu, Chunli, Zhang, Tianfu, Xu, Qian, Zhang, Dongling, Liu, Xiaotong, Jiao, Haijun, Wen, Xiaodong, Yang, Yong, Li, Yongwang, Niemantsverdriet, J.W., and Zhu, Junfa

Abstract

The adsorption and dissociation of O2on Ir(100) has been studied with X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunneling microscopy together with density functional theory calculations. At low coverage, XPS shows a single O 1s peak at 530.6 eV, associated with bridged O atoms in an Ir(100)-(3 × 1)-O structure. At saturation coverage, an additional peak at 529.5 eV appears, accompanied by an Ir(100)-(2 × 1)-O structure. The O 1s peak at 530.6 eV is assigned to oxygen atoms adsorbed on bridge sites of Ir atoms, and the peak at 529.5 eV to oxygen atoms on fourfold hollow sites of Ir. Based on our detailed experimental and computational study, oxygen diffusion into the subsurface region can be ruled out. The present study provides new findings on an additional oxygen state of the O/Ir(100) system. It also provides evidence for the absence of subsurface oxygen in Ir, implying that some discussions on subsurface oxygen in the literature may be misleading.

Published
2022

36. Atomistic Understanding of the Formation, Structure, and Decomposition of an Fe4C Iron Carbide Phase on a Copper Substrate

Author

Gubo, Richard, Ren, Pengju, García Rodríguez, Daniel, Yu, Xin, Zhang, Tianfu, Wen, Xiaodong, Yang, Yong, Li, Yong-Wang, Niemantsverdriet, J.W., and Weststrate, C.J.

Abstract

Having an atomistic understanding of the formation and structural characteristics of bulk and surface iron carbide phases plays a crucial role in comprehending the mechanisms of phase transformation, microstructure formation, and surface reconstructions in the development of advanced materials with improved magnetic, mechanical, and catalytic properties. This study uses synchrotron (SR) and angle-resolved (AR) XPS, STM, LEED, and theoretical calculations (DFT) with the aim to provide a detailed experimental and theoretical discussion on the formation, stabilization, structure, and decomposition of Fe4C iron carbide. FCC(100) Fe4C iron carbide multilayer films were prepared on Cu(100) by evaporating iron in the presence of an ethylene atmosphere. Angle-resolved XPS measurements reveal that surface and interior carbon can be distinguished due to their appearance at different binding energies and reveal that the surface consists of Fe2C while the bulk has Fe4C stoichiometry. LEED and STM measurements show that the surface exhibits the p4g(2 × 2) clock reconstruction. Theory simulations show that the bulk Fe4C iron carbide has a constrained crystal lattice with alternating Fe and Fe4C2layers, which grow in a pseudomorphic way on the copper. The carbide phase is stable up to 700 K. Above this temperature, iron diffuses into the copper while carbon remains on the surface, where it forms graphite.

Published
2023
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48. Optimized CO2Capture of the Zeolitic Imidazolate Framework ZIF-8 Modified by Solvent-Assisted Ligand Exchange

Author

Abraha, Yuel W., Tsai, Chih Wei, Niemantsverdriet, J.W., Langner, Ernst H.G., Abraha, Yuel W., Tsai, Chih Wei, Niemantsverdriet, J.W., and Langner, Ernst H.G.

Abstract

Zeolitic imidazolate frameworks, like ZIF-8 and related structures, have shown great potential for the capture of carbon dioxide. Modifying their structure by exchanging part of the constituent organic ligands is a proven method for enhancing the capacity to absorb CO2. In this work, we performed solvent-assisted ligand exchange (SALE) on nanosized ZIF-8 (nZIF-8) with a series of functionalized imidazole derivatives (exchange percentages, after 24 h): 2-bromoimidazole (19%), 2-chloroimidazole (29%), 2-trifluoromethylbenzimidazole (4%), 2-mercaptobenzimidazole (4%), and 2-nitroimidazole (54%). The sodalite topology and porosity of nZIF-8 were maintained with all SALE modifications. Low-pressure CO2 adsorption of nZIF-8 (38.5 cm3 g-1) at STP was appreciably enhanced with all mixed-linker SALE products. Using halogenated (-Cl, -Br, and -CF3) imidazole derivatives in a 24 h SALE treatment resulted in increases between 11 and 22% in CO2 adsorption, while the thiol (-SH)- and nitro (-NO2)-functionalized SALE products led to 32 and 100% increases in CO2 uptakes, respectively. These CO2 uptakes were further optimized by varying the SALE treatment time. The SHbIm- and NO2Im-exchanged SALE products of nZIF-8 show 87 and 98 cm3 g-1 of CO2 uptakes after 60 and 120 h of SALE, respectively. These are record high CO2 adsorptions for all reported ZIF derivatives at low-pressure conditions.

Published
2021

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