A composite aerogel with superhydrophobic external surface has been synthesized from reduced graphene oxide and polytetrafluoroethylene taken in a weight ratio of 1 : 1. The porous structure of the aerogel has been studied by the standard contact porosimetry method (SCPM). The porosimetric curves measured with respect to octane and water intersect in the region of small pores, thereby leading to the fact that the specific surface area of the aerogel in water is much larger than that in octane, although octane is known to wet any material almost ideally. This phenomenon, which is referred to as “superhydrophilicity,” is explained by the fact that, in the region of mesopores, a sample swells in water due to the hydration of surface –CO and –COH groups, which have been identified with the help of IR and Raman spectroscopies. Thus, the outside surface of the aerogel granules is superhydrophobic, while their interior is superhydrophilic in the region of small pores. As follows from the SCPM data, the total porosity and specific surface area of the aerogel are substantially larger than those of Vulcan XC-72 carbon black, which is a standard carrier for Pt catalysts used in fuel cells based on proton-exchange membranes. Oxygen electroreduction at the aerogel, containing Pt deposited in an amount of 28 µg/cm 2 , has been studied by the method of rotating disk electrode (RDE) in an aqueous 0.5 M H 2 SO 4 solution, and the results obtained have been compared with the data on standard commercial Pt (20%)/Vulcan XC-72 catalyst. It has been shown that the limiting diffusion RDE currents for Pt supported on the hydrophobic–hydrophilic aerogel are markedly higher than those for the standard catalyst because of the easier access of oxygen to the reaction zone as compared with hydrophilic Vulcan XC-72 carbon black carrier.
A method for the preparation of film coatings of titania doped with bismuth (Bi3+) and lead (Pb2+) ions, separately and simultaneously, has been developed based on sol–gel synthesis. According to X-ray phase analysis, the films represent a single-phase system of titania in anatase modification. It has been shown that doping of titania with bismuth and lead leads to a shift of the absorption maximum to the visible light region; in this case, the largest shift is observed in the sample containing 2.5 wt % bismuth and lead. The film coatings have been studied as catalysts of photoelectrooxidation of methanol, formic acid, and phenol. It has been shown that the highest catalytic effect is observed for the samples containing simultaneously bismuth and lead; however, doping of titania with bismuth has the greatest effect on the rate of organic substrates oxidation. It has been assumed that photoelectrochemical oxidation of the model systems with visible light is due to a decrease in the band gap of doped titania to 2.7 eV.
Activities of the synthesized trimetallic catalysts PtRuPd/C and PtRuIr/C supported on highly dispersed carbon soot from solutions of coordination compounds of the corresponding metals are studied in the electrooxidation of methanol. According to the data of voltammetry, the Pt 0.43 Ru 0.47 Pd 0.1 /C and Pt 0.44 Ru 0.46 Ir 0.1 /C catalysts are not inferior to the commercial catalyst Pt 0.5 Ru 0.5 /C in specific characteristics, which is consistent with the data of structural studies and the electrochemical and power characteristics of the membrane electrode unit tested in the composition of a single methanol/air fuel cell.
From solutions of organic precursors, nanosized films of titanium dioxide with photoelectrochemical activity in the visible region are obtained. A possibility of photoelectrochemical oxidation of a number of organic compounds under illumination with monochromatic light at a wavelength of 464 nm is demonstrated, which may be due to a decrease in the n-TiO2 band-gap energy to 2.7 eV.
Bi- and trimetallic platinum–ruthenium and platinum–ruthenium–palladium catalysts with specified atomic ratios Pt: Ru = 1: 1 and Pt: Ru: Pd = 1: 1: 0.1, respectively, were synthesized from the coordination compounds of the metals deposited on highly dispersed carbon black. The catalysts were characterized by powder X-ray diffraction, electron dispersive analysis, and transmission electron microscopy. According to voltammetry data, the highest activity in the dimethyl ether (DME) electrooxidation is exhibited by the catalyst Pt0.43Ru0.47Pd0.1/C; hence, it may be considered as a promising anode material for direct DME fuel cells.
The possibility of the photoelectrochemical reaction of acetate and trifluoroacetate oxidation to yield the corresponding hydrocarbons and perfluorocarbons on UV illumination of a film of nanosized titania n-TiO2 is demonstrated by the methods of cyclic voltammetry and preparative photoelectrolysis. Thus, the use of solar energy makes it possible to synthesize the Kolbe reaction products at substantially lower potentials on electrodes-catalysts containing no platinum.