Bimetallic heterostructures are used as industrial catalysts for many important transformations. However, conventional catalysts are primarily prepared in cost-effective manners without much appreciation in metal size control and metal-metal interaction. By employing recent nanotechnology, Pt nanocrystals with tailored sizes can be decorated with Co atoms in a controlled manner in colloid solution as preformed nanocatalysts before they are applied on support materials. Thus, we show that the terminal CO hydrogenation can be achieved in high activity, while the undesirable hydrogenation of the CC group can be totally suppressed in the selective hydrogenation of alpha,beta-unsaturated aldehydes to unsaturated alcohols, when Co decorated Pt nanocrystals within a critical size range are used. This is achieved through blockage of unselective low coordination sites and the optimization in electronic influence of the Pt nanoparticle of appropriate size by the Co decoration. This work clearly demonstrates the advantage in engineering preformed nanoparticles via a bottom-up construction and illustrates that this route of catalyst design may lead to improved catalytic processes.

In recent years, the carbon dioxide (CO 2 ) issue has become the focus of attention because of the position of CO 2 as the primary greenhouse gas and the implication of its emissions on the problem of climate change. Burning fossil fuels releases the CO 2 stored millions of years ago. Deforestation releases the carbon stored in trees, resulting in more CO 2 in the atmosphere. The resulting climate change is an immediate threat to our security and prosperity, as the global food supplies will be compromised. Therefore, in pursuit of a stable climate, there is an urgent need to construct a low carbon global economy. For example, the U.K. government targets a 60% cut in emissions by 2050 1 as a necessary step for the development of a sustainable economy. Thus, an instantaneous response for research studies in the chemistry of CO 2 including its activation, utilization, and fixation is urgently needed. Apart from the physical storage of CO 2 into depleted oil/gas/coal reservoirs, chemical fixation of CO 2 has attracted additional attention as a possible way to manufacture useful chemicals in some specific locations. As a result, the activation of CO 2 at high yields appears to be the essential step to achieve the above objective. However, there has been limited work in literature reporting a catalytic approach to activate and to fix CO 2 under industrial applicable conditions, despite the fact that this process has been recognized as a significant innovation to chemical industry. 2 Most previous attempts were unable to attract industrial attention as they suffer from either the use of expensive but non-robust homogeneous catalysts or the use of peculiar reaction conditions (requires excess ligand(s) and solvents at extreme conditions). 3 Here, we demonstrate a one-step catalytic fixation of CO 2 to methyl formate (MF) in liquid phase under mild industrial applicable conditions by using a new concept of coupling surface formate species formed from CO 2 on solid catalyst with excess methanol in hydrogen to form the MF, and the quantity of the product is found to greatly exceed the surface coverage of the catalyst by >45-fold. As a result, we report, for the first time, that the optimum Pd/Cu/ZnO/alumina nanocatalyst prepared from simple co-precipitation is capable of activating gaseous CO 2 to condensable MF at high yields (>20%) with excellent selectivity (>96%).As an initial effort, co-precipitated Cu/ZnO/alumina (Cat) was used as the catalyst for the proof of concept of surface coupling with blended molecule, which is an industrial catalyst for water gas shift reaction, WGS (and also reversed reaction, RWGS), where formate species is believed to be the intermediate species. 4 The use of hydrogen to activate CO 2 to useful chemicals at low temperature could be commercially viable with regard to future hydrogen availability from hydrocarbon reformations with carbon capture/storage and from catalytic water splitting via solar energy. Thus, screening of different solvent molecules in order to identify a candidate that...

Catalytic coupling of carbon dioxide with epoxide to cyclic carbonate is an important reaction that has recently been receiving renewed interest. This route allows the use of carbon dioxide as a greener chemical feedstock, which challenges the current practices for the synthesis of cyclic carbonates and derivatives. The present study is mainly concerned with catalytic coupling reaction between CO(2) and propylene oxide using organic amine as catalyst. The structural aspects of amines and the effects of their immobilization on solid surfaces on reaction kinetics are particularly studied. It is found that 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) amine maintains high catalytic activity both with and without solid support, but other primary amines, such as p-phenylenediamine give much reduced activity when placed on a solid surface. It is attributed to the absence of surface hydrogen in the supported TBD, prohibiting the catalyst sites from CO(2) poisoning. The coupling of other epoxides, including epichlorohydrin and styrene oxide over the solid supported amine, is also briefly carried out. Reaction mechanisms are proposed to explain the experimental observations.

A new class of copper, zinc, and gallium mixed oxides (CuZnGaO x ) with different chemical compositions obtained by a coprecipitation technique is identified as a highly active catalyst for the low-temperature, direct steam reforming of methanol to supply hydrogen gas to portable fuel cell devices. Their catalytic activity and selectivity are found to be critically dependent on the copper surface area, catalyst structure, and metal–support interaction, etc. As a result, temperature-programmed reduction has been used to investigate the copper ion reducibility and resulting copper speciation; N2O chemisorption and advanced microscopies to determine specific copper surface area, dispersion, and particle size; XRD to investigate the catalyst structure; EPR spectroscopy to probe the environment of Cu2+ species; and AC impedance spectroscopy to probe the mobility of trapped ions in solids. It is proposed that Ga incorporation into Cu–Zn oxide leads to the formation of a nonstoichiometric cubic spinel phase containing interstitial Cu+ ions, which can produce in situ a high population of extremely small 5 Å copper clusters at high dispersion on a defective ZnGa2O4 surface for effective catalysis.

Utilization of hydrogen gas (and carbon dioxide) from methanol steam reforming reaction directly without CO post-treatment to supply proton exchange membrane fuel cells for mobile applications is an attractive option. CuZnGaOx based mixed oxides prepared by co-precipitation are found to be active as catalysts for the reforming reaction. It is also found that the use of lower temperature and a faster substrate flow rate with a shorter contact time with the catalyst bed can significantly reduce the CO level in the product gas stream. At 150 °C this class of oxides gives a decent methanol conversion but can also totally suppress the CO production at a short contact time, which is in a sharp contrast with conventional CuZnOx based catalysts that give a significant degree of CO formation. Characterization using Diffuse Reflectance Infrared Fourier Transform (DRIFT) analysis presented in this work clearly suggests the importance of the interface between copper metal-defective oxides for the catalysis. Mechanistic aspects of this reaction are therefore discussed in this paper.