The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

Photoinduced reactivity of titanium dioxide

The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...

http://pubs.acs.org/doi/pdfplus/10.1021/acs.chemrev.5b00482

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

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...

Fundamentals and Catalytic Applications of CeO2-Based Materials

Hydrogen is considered to be the most viable energy carrier for the future. Producing hydrogen from ethanol steam reforming would not only be environmentally friendly but also would open new opportunities for utilization of renewable resources, which are globally available. This paper reviews the current state of the steam reforming process of ethanol, examines different catalysts, and, finally, makes a comparative analysis. Different catalysts have been used for the steam reforming of ethanol. Depending on the type of catalysts, reaction conditions, and the catalyst preparation method, ethanol conversion and hydrogen production vary greatly. It was observed that Co/ZnO, ZnO, Rh/Al2O3, Rh/CeO2, and Ni/La2O3−Al2O3 performed the best, in regard to the steam reforming of ethanol. Currently, hydrogen production from ethanol steam reforming is still in the research and development stage.

Current status of hydrogen production techniques by steam reforming of ethanol : A review

Low-temperature water-gas shift reaction over Au/CeO2 catalysts

Gold, silver and copper catalysts supported on TiO2 for pure hydrogen production

The reduction of NO x by CO was studied over gold catalyst supported on ceria and ceria–alumina. The mixed supports with different CeO 2 /Al 2 O 3 ratios were prepared by co-precipitation. The catalysts were characterized by means of XRD, TPR, XPS and Raman spectroscopy. The addition of alumina led to a slight enlargement of the gold particles, while the ceria particle size was decreased. Deeper oxygen vacancies formation in the presence of alumina was detected by TPR, XPS and Raman spectroscopy, compared to the pure ceria support. The samples exhibited a high and stable activity and 100% selectivity towards N 2 was reached at 200 °C.

Gold catalysts supported on CeO2 and CeO2–Al2O3 for NOx reduction by CO

The complete benzene oxidation reaction was used to test the reactivity of the Au-V 2 O 5 /TiO 2 and Au-V 2 O 5 /ZrO 2 catalytic systems. A strong synergistic effect between gold and vanadia was established when molecular oxygen was used as an oxidizing agent. This effect was more pronounced for titania than for the zirconia support. In the presence of gold, predominantly polyvanadate structures are formed on the surface which are more active in the reaction of complete benzene oxidation in comparison with monovanadate species and bulk V 2 O 5 . The deposition of gold leads to a relative lengthening of the VO bond and to a higher electron delocalization. The B and C parameters calculated from ESR spectra showed no differences for the fresh and spent gold-containing samples, i.e. the catalytic systems seemed to be “stabilized” under the working conditions. The effect of gold on the vanadium oxide reducibility, which could be related to the strength of the VO-support bond, results in a considerable lowering of the temperature of the V 5+ → V 3+ transition. With ozone as the oxidizing agent, an additional lowering of the reaction temperature was achieved and very close values of the catalytic activity on all investigated samples were registered. Upon oxidation by molecular oxygen the oxidant activation takes place on the nanosize gold particles while the vanadium oxide surface species are responsible for the activation of benzene. This is in agreement with synergistic effect between the finely dispersed gold and the surface vanadium structures.

Nanosize gold catalysts promoted by vanadium oxide supported on titania and zirconia for complete benzene oxidation

The new generation of gold-vanadia catalysts supported on mesoporous titania and zirconia for complete benzene oxidation were explored. The catalysts were characterized by X-ray, TEM, SEM, N2 adsorption analysis, TPR and ESR spectroscopy. The vanadia loading stabilized structure of the both mesoporous supports and this effect is stronger for zirconia comparing to titania. The presence of gold enhanced the V5+→V3+ reduction step and depending on the preparation method, differences in the reduction behavior were established. The catalytic activity of the catalysts also strongly depends on the preparation techniques. For the both series of the studied catalysts when the gold is loaded firstly the activity in complete benzene oxidation is higher than when the vanadia is deposited firstly (VAT>AVT and VAZ>AVZ). A strong synergistic effect between gold and vanadia supported on titania was observed and the catalysts on titania exhibit higher catalytic activity than the catalysts based on zirconia. Comparing the activity of the gold-vanadia/zirconia and gold/zirconia catalysts, it was established for the both catalysts high and equal activity in the reaction studied. The observed differences in the structural and catalytic properties of the both series of the studied catalysts were connected with the nature of the supports used.

Lyuba Ilieva

Papers

Low-temperature water-gas shift reaction over Au/CeO2 catalysts

Gold, silver and copper catalysts supported on TiO2 for pure hydrogen production

Gold catalysts supported on CeO2 and CeO2–Al2O3 for NOx reduction by CO

Nanosize gold catalysts promoted by vanadium oxide supported on titania and zirconia for complete benzene oxidation

Complete benzene oxidation over gold-vanadia catalysts supported on nanostructured mesoporous titania and zirconia