Layered Double Hydroxide-Based Catalysts: Recent Advances in Preparation, Structure, and Applications

The development of high-efficiency and low-cost catalysts for hydrogen release from chemical hydrogen-storage materials is essential for the hydrogen-economy paradigm. Herein, we report a facile and controllable method to fabricate a series of Co-doped nickel phosphides and their corresponding nanohybrids with graphene oxide (GO) as highly efficient, robust and noble-metal-free catalysts for ammonia borane hydrolysis. The incorporation of Co into Ni2P effectively optimizes the electronic structures of Ni2−xCoxP catalysts to enhance their interaction with AB and simultaneously facilitate the hydroxyl activation of AB, resulting in the reduction of the reaction energy barrier and thus substantial improvement of the catalytic rate.

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Ternary Ni–Co–P nanoparticles as noble-metal-free catalysts to boost the hydrolytic dehydrogenation of ammonia-borane

We report a new synthetic strategy for the fabrication of several supported nickel phosphides (Ni12P5, Ni2P, and NiP2) with particle size ranging from 5 to 15 nm via a two-step procedure: preparation of supported Ni particles from layered double hydroxide precursors, followed by a further reaction with a certain amount of red phosphorus. The selective hydrogenation of phenylacetylene over these metal phosphides was evaluated, and the as-prepared Ni2P/Al2O3 catalyst shows a much higher selectivity to styrene (up to 88.2%) than Ni12P5/Al2O3 (48.0%), NiP2/Al2O3 (65.9%), and Ni/Al2O3 (0.7%) catalysts. EXAFS and in situ IR measurements reveal that the incorporation of P increases the bond length of Ni–Ni, which imposes a key influence on the adsorption state of alkene intermediates: as the Ni–Ni bond length extends to 0.264 nm, the alkene intermediate undergoes di-π(C═C) adsorption, facilitating its desorption and the resulting enhanced selectivity. Moreover, electron transfer occurs from Ni to P, as confirmed...

Metal Phosphides Derived from Hydrotalcite Precursors toward the Selective Hydrogenation of Phenylacetylene

SBA-15 supported NiMo hydrotreating catalysts with different EDTA/Ni molar ratio were prepared by incipient wetness impregnation method. Hydrotreating activities of these catalysts were studied with Athabasca bitumen derived light gas oil and comparison was done with NiMo/SBA-15 and NiMo/γ-Al2O3 catalysts. A beneficial effect of chelating ligand was seen in hydrotreating activity and 28% increase in HDS of LGO was found as compared to NiMo/γ-Al2O3 in the case of EDTA/Ni molar ratio 4. Detailed mechanistic aspect of interaction between support – EDTA (ethylene diamine tetraacetic acid), EDTA-metallic species, support – metal, metallic species – metallic species at different reaction conditions is studied at different process parameters by using different characterization techniques such as X-ray absorption near-edge structure (XANES), Fourier transform infrared spectroscopy (FTIR), HRTEM, XRD, Raman, temperature programmed reduction (TPR), ICP-MS, CO chemisorption and N2 adsorption. A detailed scheme has been developed to explain the behavior of chelating agent in mesoporous SBA-15 supported catalysts. HRTEM results explain the high dispersion of Ni and MoS2 active phases in sulfided state even though big crystallite of MoO3 was seen in oxide state characterized by XRD and Raman spectra which explains role of EDTA in redistribution of active phases during sulfidation. XANES technique is used as predominant method for atomic level study of various structural changes in sulfided and oxide catalysts to find out the appropriate mechanism of the reaction. Characterization by XANES reveals that the presence of chelating agent delayed Ni2+ sulfidation which is main cause of improvement in HDS and HDN activity of the catalysts prepared in presence of organic chelates. Nickel sulfidation starts only when the EDTA–Ni complex decomposes and released nickel atoms move to the reactive edges of the MoS2 to form a finely dispersed sulfide Ni Mo S type II active phase.

Beneficial influence of EDTA on the structure and catalytic properties of sulfided NiMo/SBA-15 catalysts for hydrotreating of light gas oil

The nature of active sites of Ni2P electrocatalyst for hydrogen evolution reaction

In situ FTIR and XANES studies of thiophene hydrodesulfurization on Ni2P/MCM-41

The cleanliness of transferred graphene is of significant importance for its application as the window material in environmental cells used for electron microscopy and spectroscopy. We investigated...

Investigation of the Cleanliness of Transferred Graphene: The First Step toward Its Application as a Window Material for Electron Microscopy and Spectroscopy

Introduction Precise size control of metal species on oxide surfaces, especially in the range of <1 nm, is now highly important to develop the next-generation catalysts, sensors, and electronic devices. However this is not easy since metal atoms are easily aggregated to form large particles on oxide surfaces. Our group has developed the “premodified surface method” to obtain a highly dispersed metal species, where before metal deposition an oxide surface is precovered with a functional organic molecule possessing a substituent atom which can strongly coordinate to a metal atom [1-2]. Here, Cu was vacuum-deposited onto the TiO2(110) surface premodified with ortho-mercaptobenzoic acid molecules (o-MBA), and the structure of the deposited Cu species was determined by Polarization dependent TotalReflection Fluorescence (PTRF) XAFS.

http://pfwww.kek.jp/acr2010pdf/part_b/pf10b081.pdf

PTRF-XAFS Study of Atomically Dispersed Cu Species on a TiO 2 (110) Surface Premodified with Functional Organic Molecules

Investigation of the Cleanliness of Transferred Graphene: The First Step Toward Its Application as a Window Material for Electron Microscopy and Spectroscopy

Kotaro Miyazaki

Papers

In situ FTIR and XANES studies of thiophene hydrodesulfurization on Ni2P/MCM-41

Investigation of the Cleanliness of Transferred Graphene: The First Step toward Its Application as a Window Material for Electron Microscopy and Spectroscopy

PTRF-XAFS Study of Atomically Dispersed Cu Species on a TiO 2 (110) Surface Premodified with Functional Organic Molecules

Investigation of the Cleanliness of Transferred Graphene: The First Step Toward Its Application as a Window Material for Electron Microscopy and Spectroscopy