| Mixing two different metals to form alloy nanostructure can obtain enhanced activities for novel electron structure which is different from either of the single component. Deposited metal on the semiconductor such as TiO2 to develop metal/TiO2 catalysts which can be applied to all kinds of heterogeneous catalytic reaction with high performance. On the other hand, under light irradiation, the energetic electrons will generated on the surface of metal particles by localized surface plasmon resonances and interband excitations. These energetic electrons transferred to the conduction band of TiO2 over the interface of metal and semiconductor to realize the separation of electrons and holes making the catalyst have high photocatalytic activity.One-dimensional titanium dioxide nanomaterials, such as nanobelts, nanowires, can be used as support to load evenly dispersed metal for its remarkable stability, high surface area and smooth surface to improve the catalytic activity and stability. What’s more, the excellent axial transmission performance of one-dimensional nanomaterials can effectively promote the transfer of hot electron from metal to TiO2 to improve its photocatalytic activity.In this paper, bimetallic nanocatalysts supported on TIO2-NB, namely as Cu-M(M=Pt、Pd、Au)/TiO2 nanobelts were prepared via deposition-precipitation method and the structure and composition were characterized by ICP, XRD, SEM, TEM, HR-TEM, XPS and Uv-vis-NIR. The photoactivities of bimetallic nanocatalysts were evaluated by photocatalytic aerobic oxidation of benzyl alcohol with photoelectric chemical testing and thermal activities were assessed via catalytic of alcohol. The detail contents are as follows:1、TiO2 nanobelts were synthesized via a simple hydrothermal process by using titanium dioxide (P25) as the precursor and then deposited Cu-M (M=Pt、Pd、Au) metal clusters on them by deposition-precipitation method to obtain Cu-M/TiO2-NB nanostructure. From TEM image, we can see that many small-sized (less than 2 nm) metal nanoclusters uniformly dispersed on TiO2-NB. Bimetallic nanoclusters have smaller size compared with the monometallic metal clusters. And Cu-Pt clusters had the smallest size of about 1 nm. ICP test showed that the amount of metal deposition and composition of the metal clusters can be adjusted via controlling the composition and dosage of precursor bodily fluids. The HR-TEM observation, XPS spectra and Light absorption characteristics measurements revealed the supported metal clusters were alloy structure. XPS spectra indicated that Au and Pt can keep for metallic state for their large electronegativity while metal Pd and Cu are easily oxidized because of small electronegativity. But for Cu-Pd, Cu-Pt and Cu-Au bimetallic nanoclusters, Pd and Cu in which can still maintain for metallic state even if smaller size than the corresponding single metal clusters showing that alloying can effectively avoid the surface oxidation of Pd and Cu atoms.2、 The as-synthesized nanostructures Cu-Pt/TiO2-NB were evaluated via aerobic oxidation of benzyl alcohol under visible light irradiation to study the photocatalytic activities. The results showed that Cu-Pt/TiO2-NB exhibited the remarkable synergistic catalytic activity in the dark, and Cu1Pt1/TiO2-NB catalyst showed the highest activity,15.4μmol of benzaldehyde were produced after 5 h reaction. Cu-Pt/TiO2-NB exhibited more remarkable synergistic catalytic activity under light irradiation, and Cu1Pt1/TiO2-NB catalyst showed the highest photo-assisted activity, 31.8μmol of benzaldehyde were produced after 5 h reaction. From the spectra of Uv-vis-NIR, wo can observed that bare TiO2 nanobelts only absorb light at wavelength below 450 nm, while all metal nanoclusters loaded on TiO2 nanobelts showed a remarkable absorption above 450 nm. Pure copper sample had a strongest light absorption capacity while exhibited no activity to the aerobic oxidation of benzyl alcohol both in the dark and under light irradiation which revealed that the high photo-assised activities of aerobic oxidation of benzyl alcohol was dominated by alloy nanoclusters. Light absorption properties and electrochemical tests showed the cause of such light enhancement for catalytic reactions is that interband excitation of the Pt-Cu clusters, especially the contained metallic Cu atoms, can generate long-life hot holes in clusters, which act as catalyst to effectively accelerate the intrinsic aerobic oxidation reactions on the surface of clusters. Photocurrent responses and photocatalytic activity decreased with the increasing metal clusters size showed that size was an important factor for the catalytic activity of catalysts, the smaller the particle size, the higher catalytic activity. On the basis of the above research, this paper puts forward the mechanism of photocatalytic activity by Cu-Pt/TiO2 nanostructured in the oxidation of alcohols aerobic.3、The as-synthesized Cu-Pt/TiO2-NB nanostructures were assembled to monolithic catalyst and evaluated via aerobic oxidation of ethanol to study the influences of catalytic activities by the reaction temperature, the ratio of oxygen and ethanol and the velocity of air. Ethanol oxidation products CO2 was detected by infrared detector. As for Cu-Pt/TiO2-NB catalyst, when the velocity of ethanol was 2 uL/min and the ratio of oxygen and alcohol was 5:1, the conversion rate of CO2 was more than 99.9% and the selectivity was as high as 90% with the reaction temperature being 140℃. While the lower catalytic activities were observed over Cu-Pd/TiO2-NB, Cu-Au/TiO2-NB. The catalytic stabilities of Cu-Pt/TiO2-NB were studied under the temperature of 120℃ for more than 10 h, and the results showed that Cu-Pt/TiO2-NB had a good stabilities. The conversion of CO2 was stabled at 43% by a long time with a tendency to increase. The catalytic activity would be slightly lower by repeated use with a same stable trend. |
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