The reduction of CO2 by photocatalysts is one of the most promising methods since CO2 can be reduced to useful compounds by irradiating it with UV light at room temperature and ambient pressure. The aim of this work was to assess the effect of a reaction media on CO2 photocatalytic reduction yields over ZnS nanoparticles deposited on montmorillonite (ZnS-MMT). Four different reaction media, such as NaOH, NaOH+Na2SO3 (1:1), NH4OH, NH4OH+Na2SO3 (1:1), were tested. The pure sodium hydroxide was better than ammonium hydroxide for the yields of the both gas phase (CH4 and CO) and liquid phase (CH3OH). The addition of Na2SO3 improved methanol yields due to the oxidation prevention of incipient methanol to carbon dioxide. The gas phase yields were decreased by the Na2SO3 addition. The best tested reaction medium for the photocatalytic reduction of CO2 was the solution of sodium hydroxide.
Preparation of highly active palladium catalyst supported on silica by ion exchange method was investigated. The catalytic activities and physical properties of catalysts were investigated on hydrogen reaction of benzene, CO pulse method, X-ray analysis and the temperature programmed reduction. The Pd/SiO2 catalysts were prepared by an ion exchange method using various aqueous ammonia solution (28-0.5%) of PdCl2. The catalytic activity of Pd/SiO2 catalyst prepare d using 28% ammonia solution decreased rapidly with a process time in the hydrogenation of benzene. However, the catalysts prepared using aqueous ammonia solution below 1.0% exhibited the high initial activity and little decreased during the reaction for 2 h. In a DTA measurement, the catalyst prepared using high concentration (28%) of ammonia solution showed a peak at 300 °C based on ammonia combustion, while the catalyst prepared using a low ammonia concentration (below 1.0%)did not show a peak around at 300 °C. In the case of the catalyst prepared using a low concentration ammonia solution, palladium oxide on SiO2 was easily reduced at low temperature and metallic palladium produced contains a number of lattice defects. In conclusion, very high catalytic activity and stability can be achieved when the catalyst is prepared by ion exchange method using a low ammonia concentration of the ion exchange solution.
One kind of novel heterogenous bifunctional catalyst, MCM-41 grafted quaternary ammonium salts with terminal amino group, was prepared. These catalysts exhibited excellent catalytic performance and good reusability in the sequential synthesis of dimethyl carbonate from epoxides, CO2, and methanol.
Well-dispersed NaTaO(3) particles with a cubic morphology and high crystallinity were prepared by a hydrothermal route. The NaTaO(3) was doped with nitrogen by heat treatment in ammonia atmosphere. The nitrogen-doped NaTaO(3) shows an additional visible light absorption shoulder up to 550 nm. The photoelectrochemical investigation demonstrated that the photocurrent density of the photoanode of the nitrogen-doped NaTaO(3) was enhanced under the irradiation of both UV-visible light and visible light, compared to that of the undoped NaTaO(3).
Single-crystal triangular and hexangular nanoplates of gold can be obtained by electrochemical reducing AUCl(4)(-) in the presence of PVP and a small amount of H2PtCl6. With the concentration of H2PtCl6 increasing from 0 to I X 10(-3) mol/dm(3), the morphology of An nanoparticles evolved from spheroids to triangular and hexangular nanoplates with well-defined facets.
The high quality CdTe/Te multiple heterostructure nanowire arrays were Successfully fabricated by a nano-confined precipitation process. The optical properties of the as-obtained CdTe/Te heterostructure nanowires are systematically investigated, which demonstrate the strong coupling of electronic hands in CdTe/Te heterojunction.
Multiple-twinned gold nanostructures with decahedral shape have been prepared in aqueous solution by a one-step thermal process method. The decahedra of nano-gold can be obtained by heating aqueous PVP/HAuCl4 solution. In this process, poly(vinyl pyrrolidone) (PVP) acted as both reducing agent and shape-controlling surfactant. By control of the reaction condition, decahedral, icosahedral, and plate-like gold nanostructures have been obtained.
The novel fluorine-containing trisilahydrocarbon lubricants with methyl and 3,3,3-trifluoropropyl substituents (named SiFCH) were synthesized. Importantly, as potential aerospace lubricants, their chemical, physical, and tribological properties under simulated atomic oxygen (AO) exposure in space environment were investigated by a laboratory-built simulation multifunctional space tribo-tester system. The results showed that the SiFCH synthetic oils possess good physical properties and favorable tribological performance, which are superior to that of multi-alkylated cyclopentanes (MACs) in terms of frictional reduction and antiwear capacity under vacuum.