Liquid Phase Photo-Deposition Research Articles

Growth of Ag/g-C3N4 nanocomposites on nickel foam to enhance photocatalytic degradation of formaldehyde under visible light

Formaldehyde is a pollutant that significantly affects the indoor air quality. However, conventional remediation approaches can be challenging to deal with low-concentration formaldehyde in an indoor environment. In this study, Photocatalysts of Ag/graphitic carbon nitride (g-C3N4)/Ni with 3D reticulated coral structure were prepared by thermal polymerization and liquid phase photo-deposition, using nickel foam (NF) as the carrier. Experiments demonstrated that when the Ag concentration was 3%, and the relative humidity was 60%, the Ni/Ag/g-C3N4 showed the maximum degradation rate of formaldehyde at 90.19% under visible light irradiation, and the formaldehyde concentration after degradation was lower than the Hygienic standard stated by the Chinese Government. The porous structure of Ni/Ag/g-C3N4 and the formation of Schottky junctions promoted the Adsorption efficiency and degradation of formaldehyde, while the nickel foam carrier effectively promoted the desorption of degradation products. Meanwhile, the degradation rate was only reduced by 3.4% after 16 recycles, the three-dimensional porous structure extended the lifetime of the photocatalyst. This study provides a new strategy for the degradation of indoor formaldehyde at low concentrations.

Synthesis and characterization of Pt, Pt–Fe/TiO2 cathode catalysts and its evaluation in microbial fuel cell

In this present study TiO2 supported metal catalysts (Pt/TiO2, Pt–Fe/TiO2) were prepared by liquid phase photo deposition method. The prepared catalysts were characterized electrochemically. X-ray Diffractometer (XRD) results showed the presence of metal particle deposition on TiO2. HR-SEM and TEM results confirmed the nano size of the metal particles and their uniform dispersion on the surface of TiO2. Electrochemical methods such as cyclic Voltammetry, linear sweep Voltammetry were used to study the stability and oxygen reduction properties of the synthesized TiO2 supported metal catalysts. The prepared catalysts were tested in Single Chamber Microbial Fuel Cell (SCMFC) with Escherichia coli of type DH5-α as bacterium. The power densities of Pt/TiO2 and Pt–Fe/TiO2 (110.5 and 136.8 mW/m2) were found to be higher compared to that of Pt/C (77 mW/m2) in MFC operation. The results visualized the better electro catalytic property for oxygen reduction in cathodic part of microbial fuel cell.

Synthesis of nickel oxide nanoparticles supported on SiO2 by sensitized liquid phase photodeposition for applications in catalytic ozonation

Efficient degradation of 2,4-dichlorophenoxyacetic acid (2,4-D, herbicide) aqueous solutions was achieved on NiO/SiO2 catalysts in presence of ozone. NiO nanoparticles were deposited on the silica surface by impregnation (I) and liquid phase photodeposition (P) in presence of sensitizers (acetone or benzophenone). The most promising method of preparation appears to be the sensitized photodeposition allowing a higher reduction of the precursor (Ni(acac)2) at short irradiation time. The resulting catalysts were characterized by transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM–EDS), and X-ray photoelectron spectroscopy (XPS). It was found from TEM observations, that the size of NiO nanoparticles was smaller than 2nm for both preparation methods, however the particle size distribution for impregnated catalyst was broader than that of photodeposited catalyst. On the other hand, the surface composition of both catalysts was similar, showing Ni(0), NiO, Ni(OH)2 as the main species for impregnation, in the case of photodeposition an additional contribution of Ni(acac)2 were detected. According to the results of catalytic ozonation of 2,4-D, the initial specific activity of the photodeposited catalyst was almost 7 times higher compared with that of impregnation catalyst.

Liquid phase photo-deposition in the presence of unmodified β-cyclodextrin: A new approach for the preparation of supported Pd catalysts

The preparation of alumina supported Pd catalysts through a photochemical approach, consisting in the liquid phase photo-deposition (LPPD) technique in the presence of unmodified β-cyclodextrin (βCD) as protecting agent, has been here investigated. It was found that it is possible to tune both the Pd nanoparticles size and their distribution over the support surface by changing the concentration of the βCD used during the photodeposition process. In fact, on increasing the amount of the βCD, the obtained Pd/Al 2O 3 samples exhibited Pd nanoparticles (NPs) smaller and more homogeneously distributed over the support, pointing out that the βCD has a protective effect, avoiding the growth of Pd NPs and their aggregation. It is concluded that LPPD in the presence of unmodified β-cyclodextrin represents an interesting approach for the preparation of supported Pd catalysts with a controlled metal nanoparticle size and distribution to be used in structure sensitive reactions.

Preparation and Characterization of Pt/C and Pt/TiO2 Electrocatalysts by Liquid Phase Photodeposition

The preparation of carbon and titanium dioxide supported Pt catalysts through a photochemical and photocatalytic routes were investigated. The catalysts were prepared by irradiation with UV-light (365 nm) at room temperature using H2PtCl6 and C10H14O4Pt (Pt(acac)2) as platinum precursors. The kinetic studies revealed that H2PtCl6 produced metallic platinum faster than Pt(acac)2 and also showed that the amount of platinum deposited on TiO2 was higher than on carbon. The samples were characterized by X-ray diffraction, SEM/EDS and cyclic voltammetry. X-ray diffraction permitted to identify the crystallographic (111) and (200) planes from platinum metal on the catalysts synthesized, the intensity of peaks depends of the amount of platinum deposited. SEM/EDS test confirmed what it was found by the kinetics studies. The electrocatalytic activity was compared with a commercial Pt E-Tek catalyst (10 wt%). The electrochemical results showed that Pt/C-AA catalyst synthesized by liquid phase photo-deposition method has stability in acid media and high distribution of the actives sites on the electrode surfaces. It could be considered as a candidate for electro-catalyst for polymer electrolyte fuel cell. The Pt/TiO2 catalysts did not present electrochemical activity.

Direct and sensitized liquid phase photodeposition for the preparation of alumina supported Pd nanoparticles for applications to heterogeneous catalysis

Different photochemical approaches have been investigated to prepare alumina supported Pd nanoparticles to be used as heterogeneous catalysts. The employed techniques were: (i) direct photodeposition, (ii) sensitized photodeposition, and (iii) photodeposition in the presence of a protecting agent (polyvinylpirrolidone). The sensitized photodeposition with acetone resulted to be the most proper technique, allowing to obtain, in very short irradiation time, Pd particles homogeneously distributed over the support surface, with a very narrow and symmetrical monomodal distribution centered at 4–5 nm, found to be appropriate for the deep oxidation of methanol.

Preparation of ceria and titania supported Pt catalysts through liquid phase photo-deposition

The preparation of supported platinum catalysts through a photochemical approach, namely the liquid phase photo-deposition, has been investigated. Pt catalysts were prepared by irradiating at 25 °C and 254 nm an alcohol solution of platinum acetylacetonate complex, where two different supports (ceria or titania) were successively suspended. The prepared catalysts were characterized by TEM analysis and tested for the catalytic deep oxidation of two representative volatile organic compounds, namely toluene and acetone. Results were compared with those from Pt samples prepared by a conventional impregnation technique. It was found that the ceria supported Pt sample prepared by the photochemical approach exhibits much better performance in the combustion of both acetone and toluene, compared to the corresponding impregnated catalyst. A similar trend but to a lesser extent was observed on the Pt/titania series. These results were rationalized on the basis of the different distribution of Pt particles on the support, catalysts prepared by impregnation exhibiting both local massive Pt aggregates and very small Pt particles, samples prepared by photo-deposition showing instead Pt nanoparticles with a homogeneous and narrow size distribution, with diameters in the range of 1.6–2 nm, regarded as appropriate for the deep oxidation of volatile organic compounds.

Oxygen Reduction Reaction on Pt/C Catalysts Prepared by Impregnation and Liquid Phase Photo-Deposition

Pt/C catalysts supported on carbon (5 wt.% Pt) synthesized by photo-deposition and impregnation methods were electrochemi- cally evaluated in the oxygen reduction reaction. Platinum nanoparticles were prepared by photo-irradiation of Pt precursors (H2PtCl6 and C10H14O4Pt) with UV-irradiation (365 nm) at room temperature. The photo-reduction of H2PtCl6 to metallic platinum (Pt4+→Pt2+→Pt0) was faster than C10H14O4Pt (Pt2+→Pt0) at the same operation conditions. The Pt/C samples were characterized by XRD, EDS, H2 chemisorption, TEM, cyclic and linear voltammetry techniques. XRD and TEM/EDS studies showed that Pt particles synthesized with C10H14O4Pt by the photo-deposition method were smaller with a higher dispersion on carbon than those prepared with H2PtCl6. A similar behavior was found when the impregnation method is used. The platinum particle size was smaller with C10H14O4Pt as compared to H2PtCl6 precursor. The Pt/C catalyst synthesized with C10H14O4Pt by the photo-deposition method displayed a catalytic activity in the oxy- gen reduction reaction comparable to a commercial 10 wt. % Pt/C, ETEK catalyst.

Nickel nanostructured materials from liquid phase photodeposition

Liquid Phase Photo-Deposition (LPPD) technique has been used to obtain both colloidal particles and thin films of metallic and chloride nickel from solutions of only precursor Ni(acac)2 (acac=2,4-pentandionato). Metallic nickel was obtained from ethanol solutions by direct nickel(II) photoreduction at 254 nm and by acetone sensitised reaction at 300 nm. In this latter process the rate was higher than in the first one. NiCl2 was formed from CCl4 solution by a solvent-initiated reaction. TEM analysis, performed on colloidal particles of nickel, showed that their dimensions are in the range 2–4 nm. The films did not present carbon contamination and were characterized by AFM, XPS and GIXRD. Metallic films consisted of particles of 20–40 nm that are the result of the aggregation of smaller crystallites (4–5 nm). Larger agglomerations (around 200 nm) have been observed for NiCl2 films.

An investigation on the use of liquid phase photo-deposition for the preparation of supported Pt catalysts

The preparation of alumina supported Pt catalysts through a photochemical approach, namely the liquid phase photo-deposition (LPPD) technique, was here investigated. LPPD Pt/γ-Al 2O 3 catalysts were prepared irradiating at 25 °C and different wavelengths (254, 350 and 400 nm) an ethanol suspension of Pt(acac) 2 containing γ-Al 2O 3. Catalytic activity of so prepared samples was evaluated in the combustion of volatile organic compounds (VOC) and in the hydrogenation of propene, comparing the results with those of a conventionally impregnated Pt/γ-Al 2O 3 sample. LPPD catalysts exhibited better performance, in particular in the VOC combustion, compared to the reference Pt sample. The activity was found to be substantially independent from the wavelength irradiation employed during catalysts preparation. On the basis of characterization results (TEM, H 2 chemisorption and FT-IR of chemisorbed CO) the higher activity of LPPD samples was related to the narrower particle size distribution of Pt clusters observed on these samples with respect to that of the impregnated Pt catalyst.