V. A. Grinberg

Cyclometalated ruthenium complex as a promising sensitizer in dye-sensitized solar cells

Ruthenocycle bis(4,4′-dicarboxy-2,2′-bipyridine)(2-phenylpyridine-2C,N)ruthenium(II) hexafluorophosphate was used as a sensitizer in a dye-sensitized solar cell (DSSC) based on nanocrystalline TiO2, which was applied onto a conducting substrate. Its electrochemical and spectral characteristics were studied. It was found that, when the DSSC was illuminated with visible light of power 35 mW/cm2, the short-circuit current density was 11.6 mA cm−2 and the open-circuit voltage was 0.49 V. The efficiency (η) of DSSC at a fill factor of 45% was 7.1%. Using the method of modulation spectroscopy of photocurrents and photopotentials, the life time and transit time of electrons were found to be 7 and 5 ms, respectively, and the diffusion coefficient of electrons was found to be 10−5 cm2 s−1. Comparing the life and transit times of electron, it was concluded that the photogenerated electrons had time to reach the conducting substrate during their life time.

Development of methanol–air fuel cells with membrane materials based on new sulfonated polyheteroarylenes

New proton-conducting membranes were synthesized from sulfonated polynaphthoyleneimide (SPNI) and polytriazole (SPTA), which are of interest for use in portable methanol fuel cells. The membrane electrode assembly (MEA) based on SPNI and SPTA showed power and voltage-current characteristics comparable to those of MEA based on Nafion®-117. The direct and reverse polarization curves coincided almost completely in shape, indicating that the obtained characteristics are stable. At a voltage of 0.3 V and a temperature of 40°С, the current density and power density reached 68 mA cm–2 and 20.5 mW cm–2, respectively.

Photoelectrocatalytical Kolbe synthesis on thin film electrode of n-TiO2

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.

Nanostructured catalysts for direct electrooxidation of dimethyl ether based on Bi- and trimetallic Pt–Ru and Pt–Ru–Pd alloys prepared from coordination compounds

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 Photoelectrochemical Activity of Titanium Dioxide Nanosized Films in the Visible Spectral Region

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.

Development of hydrogen–air fuel cells with membranes based on sulfonated polyheteroarylenes

Proton-conducting membranes based on sulfonated polynaphthoyleneimide (PNI) and polytriazole (PTA) are synthesized that can be used in portable hydrogen–air fuel cells (HAFC). Membrane–electrode assemblies (MEAs) based on sulfonated PNI and PTA membranes in individual HAFC manifested power and voltammetric characteristics exceeding the characteristics of MEA based on the commercial Nafion-212 membrane. Thus, the current density of 320 mA cm–2 and the power density of 160 mW cm–2 are obtained at the room temperature with no pressure or gas humidification at the voltage of 0.5 V. Also activity of the oxygen electroreduction Pt–Fe/C (30 wt % of metals in total) catalyst synthesized on the basis of coordination compounds is tested in MEA HAFC. It is shown that the values of power for MEAs with the cathodic Pt–Fe/C catalyst at the voltage of 0.5 V, at the room temperature, without additional pressure and gas humidification considerably exceed the corresponding values for MEAs with the commercial E-TEK 20% Pt/C catalyst.

Photoelectrochemical cells based on nanocrystalline TiO 2 synthesized by high temperature hydrolysis of ammonium dihydroxodilactatotitanate(IV)

Photoelectric parameters of dye-sensitized solar cells (DSSC) based on nanocrystaline titanium dioxide synthesized by several methods are studied. The lifetime of charge carriers (electrons) is shown to be 10 ms for DSSC with anodes of TiO2 synthesized by hydrolysis of ammonium dihydroxodilactatotitanate(IV) (DLTA) and about 7 ms for anodes of commercial titanium dioxide (AEROXIDE®, TiO2, P 25, Evonik), which points to the lower recombination losses for anodes of DLTA. The transition times for both cell versions are close to one another and equal to 10 ms; under these conditions, the diffusion coefficient of electrons is assessed to be ca. 10−5 cm2 s−1. The comparable transition times and lifetimes of electrons in DSSCs under study suggest that a part of photogenerated electrons is lost at the diffusion to the conducting substrate.