Advanced Electron Microscopy of Metal–Support Interactions in Supported Metal Catalysts

Liu, Jingyue Jimmy

doi:10.1002/cctc.201100090

Cited by 283 publications

(249 citation statements)

References 210 publications

(100 reference statements)

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“…1,13 Improvements in ultrahigh spatial and energy resolutions have been accompanied by remarkable advances of in situ TEM techniques, which enable the real-time observation of the dynamic structural and chemical evolution in materials under a variety of external stimuli or battery operating conditions. The progress in this field is evident, as demonstrated by the success of in situ mechanical testing or heating while maintaining a high spatial resolution, 14,15 by the imaging of reaction processes in gases and liquids, [16][17][18][19] by the observations of reactions and phase transformations upon external biasing 20,21 and so on. In addition, the newly developed CMOS camera, which enables the direct electron detection and fast image acquisition at over 400 frames per second for 1 × 1 K images, has significantly advanced the capability to observe fast reactions in real time.…”

Section: Recent Advancements In Aem Capabilitiesmentioning

confidence: 99%

Advanced analytical electron microscopy for lithium-ion batteries

Qian

et al. 2015

NPG Asia Mater

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Lithium-ion batteries are a leading candidate for electric vehicle and smart grid applications. However, further optimizations of the energy/power density, coulombic efficiency and cycle life are still needed, and this requires a thorough understanding of the dynamic evolution of each component and their synergistic behaviors during battery operation. With the capability of resolving the structure and chemistry at an atomic resolution, advanced analytical transmission electron microscopy (AEM) is an ideal technique for this task. The present review paper focuses on recent contributions of this important technique to the fundamental understanding of the electrochemical processes of battery materials. A detailed review of both static (ex situ) and real-time (in situ) studies will be given, and issues that still need to be addressed will be discussed. NPG Asia Materials (2015) 7, e193; doi:10.1038/am.2015.50; published online 26 June 2015 INTRODUCTIONTo implement the commercialization of lithium-ion batteries in electric vehicles and smart grid systems, further improvements are required, especially with respect to the energy/power density, coulombic efficiency and cycle life. These parameters primarily depend on the diffusion of lithium-metal ions, electron transport, structure and chemical dynamics of the electrode/electrolyte materials, among others. During electrochemical cycling, significant changes in the material structure and elemental distributions occur, including ion relocation, lattice expansion/contraction, phase transition and structure/surface reconstruction. These changes could substantially influence ion and electron transport and affect the performance of the entire battery system. Understanding the structure-property relationships for each component and their synergistic behaviors during electrochemical processes is, therefore, essential for the design of new battery materials and the optimization of existing systems.Although many analysis techniques (for example, X-ray diffraction, X-ray absorption spectroscopy, neutron diffraction, nuclear magnetic resonance and so on) have been employed for such studies, most of them can acquire only spatially averaged information. Nevertheless, the structural and chemical evolution of battery materials upon electrochemical cycling can often be linked to specific nanofeatures, such as defects, interfaces and surfaces. As a result, techniques based on analytical transmission electron microscopy (AEM) are ideal tools to study these issues. The capability of AEM to precisely probe the structural/chemical evolutions at an ultrahigh spatial resolution frequently provides insight that cannot be obtained directly using macroscopic characterization methods.

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Section: Recent Advancements In Aem Capabilitiesmentioning

confidence: 99%

Advanced analytical electron microscopy for lithium-ion batteries

Qian

et al. 2015

NPG Asia Mater

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“…Pt loading on the Pt-air-TNTs electrode was lower than that on Pt-H-TNTs (shown in Table 2); this could be attributed to the anchoring of more Pt atoms because of the increased number of oxygen vacancies and hydroxyl groups that were created during hydrogenation. [27] Prior to Pt electrodeposition, the H-TNTs were pretreated with Pd nanoparticles by using a successive ion adsorption [28] Typically, the TNT sample was initially sensitized in an aqueous solution containing SnCl 2 and HCl for 8 min before the sample was rinsed with deionized water for 30 s to remove excess ions that were weakly bound to the top of TNTs. The sample was then activated by using a solution containing PdCl 2 and HCl for 2 min; finally, the sample was washed with deionized water.…”

Section: Support Pt Catalysts On the H-tntsmentioning

confidence: 99%

“…This indicates that using Pd as an activator could provide more uniform nucleation sites for Pt. [21,27] In contrast to the TNTs that did not contain electrodeosited catalysts, the H-TNT-supported catalysts annealed in H 2 at 450 8C for a further 1 h (Pt-Pd-H-TNTs-1-450-H) exhibited no change in morphology for the Ti sheet. After annealing, the smaller Pt nanoparticles on the Pt-Pd-H-TNTs-1 aggregated together and the mean diameter increased to 6.1 nm, also the surface of the Pt tended to become less rough.…”

Section: Support Pt Catalysts On the H-tntsmentioning

confidence: 99%

Supported Noble Metals on Hydrogen‐Treated TiO₂ Nanotube Arrays as Highly Ordered Electrodes for Fuel Cells

Zhang

et al. 2013

ChemSusChem

102

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Hydrogen‐treated TiO2 nanotube (H–TNT) arrays serve as highly ordered nanostructured electrode supports, which are able to significantly improve the electrochemical performance and durability of fuel cells. The electrical conductivity of H–TNTs increases by approximately one order of magnitude in comparison to air‐treated TNTs. The increase in the number of oxygen vacancies and hydroxyl groups on the H–TNTs help to anchor a greater number of Pt atoms during Pt electrodeposition. The H–TNTs are pretreated by using a successive ion adsorption and reaction (SIAR) method that enhances the loading and dispersion of Pt catalysts when electrodeposited. In the SIAR method a Pd activator can be used to provide uniform nucleation sites for Pt and leads to increased Pt loading on the H‐TNTs. Furthermore, fabricated Pt nanoparticles with a diameter of 3.4 nm are located uniformly around the pretreated H–TNT support. The as‐prepared and highly ordered electrodes exhibit excellent stability during accelerated durability tests, particularly for the H–TNT‐loaded Pt catalysts that have been annealed in ultrahigh purity H2 for a second time. There is minimal decrease in the electrochemical surface area of the as‐prepared electrode after 1000 cycles compared to a 68 % decrease for the commercial JM 20 % Pt/C electrode after 800 cycles. X‐ray photoelectron spectroscopy shows that after the H–TNT‐loaded Pt catalysts are annealed in H2 for the second time, the strong metal–support interaction between the H–TNTs and the Pt catalysts enhances the electrochemical stability of the electrodes. Fuel‐cell testing shows that the power density reaches a maximum of 500 mW cm−2 when this highly ordered electrode is used as the anode. When used as the cathode in a fuel cell with extra‐low Pt loading, the new electrode generates a specific power density of 2.68 kW gPt−1. It is indicated that H–TNT arrays, which have highly ordered nanostructures, could be used as ordered electrode supports.

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“…Generally, metal-support interaction (MSI) plays an important role in affecting the catalytic performances of supported nanocatalysts [22,23], especially for Au-based catalysts that are sensitive to many factors such as the size of GNPs, valence state of gold and synthesis methods [24,25]. The combined effect of the above factors makes the catalytic mechanism of the supported gold systems quite complicated.…”

Section: Introductionmentioning

confidence: 99%