Activity Of Composite Materials Research Articles

Synthesis of Cu@Pt‐Pd Ternary Metallic Composites for Efficient Electrocatalysis of Methanol

AbstractAn electrochemical preparation method of Cu@Pt‐Pd ternary metallic composite, which is used as excellent catalytic materials to oxide methanol under alkaline conditions, is reported in this work. Cu polyhedron as nuclei and Pt‐Pd alloy nanoclusters as shells of Cu@Pt‐Pd are proved by X‐ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The activities of composite materials are examined by linear sweep voltammetry, cyclic voltammetry, and chronoamperometry. The catalytic activity is investigated by modulating metal element proportion of Pt and Pd. The highest mass activity of Cu@Pt11.3Pd10.1 is 2387 mA mgPt+Pd−1 for methanol oxidation reaction. The mass activity of Cu@Pt11.3Pd10.1 is 3.42 folds relative to Pt/C catalysts. Compared with Pt/C catalysts, Cu@Pt‐Pd composites have higher CO resistance. This enhanced catalytic performance is closely related to its alloy structure through ligand and strain effects.

Preparation of ZnO-GO nanocomposites and their properties

ZnO nanoparticles were prepared by hydrothermal method. The modified Hummer process was then used to prepare go. The ZnO-GO com posites were then mixed to produce different ratios of ZnO-GO, characteris ed and their photocatalytic properties were investigated using rhodamine B as the target degradation species. The results showed that the degradation r ates of rhodamine B were 41.96% and 84.42% for the nano-ZnO and ZnO-GO 7% composites, respectively, when illuminated with xenon light for 36 0 min. The improved photocatalytic activity of composite materials is prim arily due to the introduction of appropriate amount of GO, which could ra pidly capture and transfer to the photogenerated electrons, and could load more ZnO and prevent the agglomeration of ZnO particles, increasing the s pecific surface area of ZnO and its activation point, as well as increasing th e adsorption of pollutants on the ZnO surface and improving the photocatal ytic efficiency.

Physicochemical Characteristics and Catalytic Activity of Composite Materials Based on Mixed Oxides MTiO3/TiO2 (М = Co, Ni) in 1,2-Dihydroxybenzene Photodegradation Reactions in Aqueous Solutions

Mixed cobalt and nickel oxides MTiO3/TiO2 (M = Co2+, Ni2+) are synthesized. Organometallic complexes of titanium tetrabutylate Ti(OBu)4 with 1,2-dihydroxybenzene and nitrate hydrates of corresponding metals (M) synthesized under conditions of the modified sol-gel process are used as precursors. The synthesized samples are characterized by field-emission scanning electron microscopy, energy-dispersive X-ray analysis, diffuse reflectance spectroscopy, dispersive X-ray radiation analysis, X-ray diffraction, and low-temperature nitrogen adsorption. The photocatalytic activity of the samples is tested in the ultraviolet spectral range (200 nm < λ < 400 nm) in the photodegradation of 1,2-dihydroxybenzene (catechol) in aqueous solutions.

Polymer electrets with quadratic nonlinear-optical activity

The nonlinear-optical (NLO) activities of composite materials with a binary set of chromophores are measured with the Second Harmonic Generation technique (λ=1064 nm). In these materials the host matrix is an epoxy amine polymer with an azochromophore, covalently attached in such a way that its donor-group is included in the main chain. Apart from this chromophore functionalized epoxy amine oligomer, CFAO, a guest azochromophore dispersed orange, DO3, is added. The addition of DO3 in two concentrations (10 and 20 wt%) enhances the NLO coefficient compared to that for CFAO by ca. 40%. Molecular modeling in an amorphous cell is used for estimating the local mobility of different groups and fragments of the polymeric chain, in particular, that of the azochromophores. The information obtained from the modeling can be used for the development of an effective time-temperature poling protocol. It is shown that for a high chromophores orientation the poling temperature should be some 20–30 K higher than the glass transition Tg.

In Ukrainian

in Ukrainian

Preparation and properties of hydroxyapatite/titania composite for microbial filtration application

A series of TiO2 modified hydroxyapatite composites (HA/TiO2) with different compositions were prepared. Phase formations and morphologies of the obtained HA/TiO2 composite were characterised using X-ray diffraction and SEM, and their photocatalytic activities were also determined by decomposition of methylene blue solution. Filter cloths were prepared by depositing the composite on polyester non-wovens via pad dry cure, and their filtering effectiveness was examined by photocatalytic activity measurement and bactericidal test. Hydroxyapatite/TiO2 composites were successfully prepared and exhibited photocatalytic properties. With increasing ratio of anatase titania in the HA/TiO2 composite from 20 to 30 and 50%, photocatalytic activity of composite material increased such that HATi5050 composite exhibited the highest photocatalytic activity. Non-woven filters coated with HA/TiO2 composites also exhibited good photocatalytic activities. Less difference in photocatalytic activity between HATi7030 and HATi5050 coated non-woven filters was observed, compared to that in powder form. The filter coated with HA/TiO2 composite exhibited good bactericidal effect.

Pyropolymer-based Oxygen Electrode for Solid Polymer Electrolyte Systems

The activity of composite materials (acetylene black or ultrafinely divided dynamic diamond + Co-pyropolymer + Nafion solution) in the oxygen electroreduction in a 0.5 M H2SO4solution and when using a Nafion-117 film 200 μm thick as a proton-conducting electrolyte is compared. It is established that the addition of Nafion in the active mass leads to a decrease in the electrocatalytic activity of the latter. The same composite catalyst (at an insignificant thickness of the active layer) in contact with a solid polymer electrode makes it possible to obtain current densities ten times those in a sulfuric acid solution. Possible reasons for these effects are discussed.