Restructuring-Induced Activity of SiO2-Supported Large Au Nanoparticles in Low-Temperature CO Oxidation

Surface and interface design for heterogeneous catalysis

Recent progresses in catalytic nanocrystals with uniform and well-defined structures, in situ characterization techniques, and theoretical calculations are facilitating the innovation of efficient catalysts via surface and interface designs, including crystal phase design, morphology/facet design, and size design, followed by controlled synthesis.

Catalytic Performance of Gold Supported on Mn, Fe and Ni Doped Ceria in the Preferential Oxidation of CO in H2-Rich Stream

Ceria supported metal catalysts often exhibit high activity in the preferential oxidation (PROX) of CO in H2-rich stream and doping the ceria support with other metals proves to be rather effective in further enhancing their catalytic performance. Therefore, in this work, a series of ceria materials doped with Mn, Fe and Ni (CeM, where M = Mn, Fe and Ni; M/Ce = 1/8) were synthesized by a modified hydrothermal method; with the doped ceria materials (CeM) as the support, various supported gold catalysts (Au/CeM) were prepared by the colloidal deposition method. The influence of metal dopant on the performance of these ceria materials supported with gold catalysts in CO PROX was then investigated in detail with the help of various characterization measures such as N2 sorption, XRD, TEM, Raman spectroscopy, H2-TPR, XPS and XAS. The results indicate that the incorporation of Mn, Fe and Ni metal ions into ceria can remarkably increase the amount of oxygen vacancies in the doped ceria support, which is beneficial for enhancing the reducibility of ceria, the metal-support interaction and the dispersion of gold species. Although the gold catalysts supported on various doped ceria are similar in the size and state of Au nanoparticles, the CO conversions for CO PROX over Au/CeMn, Au/CeFe and Au/CeNi catalysts are 65.6%, 93.0% and 48.2%, respectively, much higher than the value of 33.6% over the undoped Au/CeO2 catalyst at ambient temperature. For CO PROX over the Au/CeNi catalyst, the conversion of CO remains near 100% at 60–130 °C, with a PROX selectivity to CO2 of higher than 50%. The excellent performance of Au/CeNi catalyst can be ascribed to its large amount of oxygen vacancies and high reducibility on account of Ni incorporation. The insight shown in this work helps to clarify the doping effect of other metals on the physicochemical properties of ceria, which is then beneficial to building a structure-performance relation for ceria supported gold catalyst as well as developing a better catalyst for removing trace CO in the hydrogen stream and producing high purity hydrogen.

The wet synthesis and quantification of ligand-free sub-nanometric Au clusters in solid matrices

The synthesis of ligand-free sub-nanometric metal clusters on a large scale suffers typically from very low yields (<5% yield) and needs very high dilutions. Here we show that Au clusters can be prepared with ethylene-vinyl alcohol copolymers (EVOH), charcoal, and different metal oxides (CeO₂, Al₂O₃, TiO₂ and ZnO) in >15% yields, as unambiguously determined using a very simple and extremely sensitive analytical reaction test.

Surface chemistry of group IB metals and related oxides

Catalytic surface chemistry of IB metals are reviewed with an attempt to bridge model catalysts and powder catalysts.

Metal–organic framework MIL-101 supported bimetallic Pd–Cu nanocrystals as efficient catalysts for chromium reduction and conversion of carbon dioxide at room temperature

A series of bimetallic Pd–Cu nanocrystals supported on the zeolite-type metal–organic framework MIL-101 and their application in the reduction of Cr(vi) to Cr(iii) using formic acid and the conversion of terminal alkynes into propiolic acids with CO₂ are reported.

A pulse chemisorption/reaction system for in situ and time-resolved DRIFTS studies of catalytic reactions on solid surfaces

A pulse chemisorption/reaction system in combination with Fourier transform infrared spectrometer equipped with a diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) reaction cell and online mass spectrometer is described in detail. Such a system provides an approach to effectively suppress the interference of the gas-phase reactants to the vibrational signals of surface adsorbates during the operando DRIFTS measurements and, thus, allows for in situ and real-time monitor of surface species on catalyst surfaces during chemisorption/reaction processes. Employing this system, we successfully acquired DRIFTS spectra that clearly demonstrate surface species formed by propylene chemisorption and reaction on octahedral Cu2O nanocrystals; we also observed simultaneous chemisorption of CO on top, twofold, and threefold bridged sites of Pd nanoparticles supported on SiO2 upon the collision of CO prior to the saturation of strongly bound sites and the transformation of weakly bound CO(a) into strongly bound CO(a) during the dynamic chemisorption-desorption processes.

Low temperature CO sensor based on cataluminescence from plasma-assisted catalytic oxidation on Ag doped alkaline-earth nanomaterials

Based on cataluminescence from plasma-assisted catalytic oxidation, a low temperature CO sensor was fabricated. With Ag doped alkaline-earth catalyst as sensing element, air as discharge gas, carrier gas and oxidant supplier, significant cataluminescence was achieved at low temperature, demonstrating a potential low-consumption and portable sensor of CO.