Yu-Ying Huang

Bio: Yu-Ying Huang is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Catalysis & X-ray absorption fine structure. The author has an hindex of 9, co-authored 11 publications receiving 439 citations.

Highly Dispersed Copper Oxide Clusters as Active Species in Copper-Ceria Catalyst for Preferential Oxidation of Carbon Monoxide

Abstract: Copper-ceria is one of the very active catalysts for the preferential oxidation of carbon monoxide (CO-PROX) reaction, which is also a typical system in which the complexity of copper chemistry is clearly exhibited. In the present manuscript, copper–ceria catalysts with different Cu contents up to 20 wt % supported on CeO2 nanorods were synthesized by a deposition–precipitation (DP) method. The as-prepared samples were characterized by various structural and textural detections including X-ray diffraction (XRD), Vis-Raman, transmission electron microscopy (TEM), ex situ/in situ X-ray absorption fine structure (XAFS), and temperature-programmed reduction by hydrogen (H2-TPR). It has been confirmed that the highly dispersed copper oxide (CuOx) clusters, as well as the strong interaction of Cu-[Ox]-Ce structure, were the main copper species deposited onto the ceria surface. No separated copper phase was detected for both preoxidized and prereduced samples with the Cu contents up to 10 wt %. The fresh copper–...

Contributions of distinct gold species to catalytic reactivity for carbon monoxide oxidation

Abstract: Small-size (<5 nm) gold nanostructures supported on reducible metal oxides have been widely investigated because of the unique catalytic properties they exhibit in diverse redox reactions. However, arguments about the nature of the gold active site have continued for two decades, due to the lack of comparable catalyst systems with specific gold species, as well as the scarcity of direct experimental evidence for the reaction mechanism under realistic working conditions. Here we report the determination of the contribution of single atoms, clusters and particles to the oxidation of carbon monoxide at room temperature, by the aid of in situ X-ray absorption fine structure analysis and in situ diffuse reflectance infrared Fourier transform spectroscopy. We find that the metallic gold component in clusters or particles plays a much more critical role as the active site than the cationic single-atom gold species for the room-temperature carbon monoxide oxidation reaction. Nanoscale supported gold clusters are common redox catalysts but in many cases the nature of the active sites remains unclear. Here, the authors use X-ray absorption to determine the contribution of single gold atoms, clusters and particles on the reactivity of room-temperature carbon monoxide oxidation.

Effect of strongly bound copper species in copper–ceria catalyst for preferential oxidation of carbon monoxide

Abstract: Copper–ceria catalysts with the Cu contents up to 40 at.% were prepared by the coprecipitation method. Ammonium carbonate was used as the leaching agent on the as-calcined samples to remove the weakly bound copper species. The parent and leached catalysts were tested for the preferential oxidation of carbon monoxide (CO-PROX) reaction from 40 to 200 °C in 1%CO/1%O2/50%H2/N2 with a space velocity of 60,000 mL h−1 gcat−1. When the Cu doping amount reached 30 at.%, the stable and constant CO-PROX reactivity, including CO conversion and O2 selectivity, was presented for both parent and ammonium carbonate leached catalysts. The fresh and used samples have been carefully characterized by various techniques such as power X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), transmission electron microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H2-TPR). It was confirmed that there are two different types of copper species, i.e. weakly bound CuOx clusters and strongly bound Cu–[Ox]–Ce structure, in both parent and leached catalysts. Furthermore, we have demonstrated that the weakly bound CuOx clusters removed by ammonium carbonate can be recovered by the migration of Cu–[Ox]–Ce species under the reduction or reaction conditions. The strongly bound copper species in CeO2 have been identified to be the reservoir for the active Cu sites for CO-PROX.

Uniform 2 nm gold nanoparticles supported on iron oxides as active catalysts for CO oxidation reaction: structure-activity relationship.

Abstract: Uniform Au nanoparticles (∼2 nm) with narrow size-distribution (standard deviation: 0.5–0.6 nm) supported on both hydroxylated (Fe_OH) and dehydrated iron oxide (Fe_O) have been prepared by either deposition-precipitation (DP) or colloidal-deposition (CD) methods. Different structural and textural characterizations were applied to the dried, calcined and used gold-iron oxide samples. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) showed high homogeneity in the supported Au nanoparticles. The ex situ and in situ X-ray absorption fine structure (XAFS) characterization monitored the electronic and short-range local structure of active gold species. The synchrotron-based in situ X-ray diffraction (XRD), together with the corresponding temperature-programmed reduction by hydrogen (H2-TPR), indicated a structural evolution of the iron-oxide supports, correlating to their reducibility. An inverse order of catalytic activity between DP (Au/Fe_OH Au/Fe_O) was observed. Effective gold-support interaction results in a high activity for gold nanoparticles, locally generated by the sintering of dispersed Au atoms on the oxide support in the DP synthesis, while a hydroxylated surface favors the reactivity of externally introduced Au nanoparticles on Fe_OH support for the CD approach. This work reveals why differences in the synthetic protocol translate to differences in the catalytic performance of Au/FeOx catalysts with very similar structural characteristics in CO oxidation.

Solvent Influence on the Role of Thiols in Growth of Thiols-Capped Au Nanocrystals

Abstract: Solvent has a key role in the controllable synthesis of nanocrystals (NCs). Here, using X-ray absorption spectroscopy, we demonstrate that solvent can significantly influence the adsorption of thiols on Au NCs, and thereby affects their growth. It is shown that increasing the solvent polarities leads to the higher thiol coverage on the NC surface. The high coverage of thiols then retards the growth of particles, and as a result, the NCs' sizes decrease with the increase in the solvents' polarities. The underlying reason for the solvent dependence is proposed to be the synergistic effects of different hydrogen bond and hydrophobic interactions between the sulfhydryl and alkyl groups of thiols with the solvents molecules. This work addresses the important role of the solvent environments in the size-controlled synthesis of NCs.

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

Abstract: Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

Heterogeneous single-atom catalysis

Abstract: Single-atom catalysis has arguably become the most active new frontier in heterogeneous catalysis. Aided by recent advances in practical synthetic methodologies, characterization techniques and computational modelling, we now have a large number of single-atom catalysts (SACs) that exhibit distinctive performances for a wide variety of chemical reactions. This Perspective summarizes recent experimental and computational efforts aimed at understanding the bonding in SACs and how this relates to catalytic performance. The examples described here illustrate the utility of SACs in a broad scope of industrially important reactions and highlight the advantages these catalysts have over those presently used. SACs have well-defined active centres, such that unique opportunities exist for the rational design of new catalysts with high activities, selectivities and stabilities. Indeed, given a certain practical application, we can often design a suitable SAC; thus, the field has developed very rapidly and afforded promising catalyst leads. Moreover, the control we have over certain SAC structures paves the way for designing base metal catalysts with the activities of noble metal catalysts. It appears that we are entering a new era of heterogeneous catalysis in which we have control over well-dispersed single-atom active sites whose properties we can readily tune. Single-atom catalysts are heterogeneous materials featuring active metals sites atomically dispersed on a surface. This Review describes methods by which we prepare and characterize these materials, as well as how we can tune their catalytic performance in a variety of important reactions.

Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities

Abstract: Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1–3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the s...

Fundamentals and Catalytic Applications of CeO2-Based Materials

Abstract: Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40th anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are dee...

Development of MOF-Derived Carbon-Based Nanomaterials for Efficient Catalysis

Abstract: Carbon-based nanomaterials have been widely used as catalysts or catalyst supports in the chemical industry or for energy or environmental applications due to their fascinating properties. High surface areas, tunable porosity, and functionalization are considered to be crucial to enhance the catalytic performance of carbon-based materials. Recently, the newly emerging metal–organic frameworks (MOFs) built from metal ions and polyfunctional organic ligands have proved to be promising self-sacrificing templates and precursors for preparing various carbon-based nanomaterials, benefiting from their high BET surface areas, abundant metal/organic species, large pore volumes, and extraordinary tunability of structures and compositions. In comparison with other carbon-based catalysts, MOF-derived carbon-based nanomaterials have great advantages in terms of tailorable morphologies and hierarchical porosity and easy functionalization with other heteroatoms and metal/metal oxides, which make them highly efficient as...