Improvement of Orange II Photobleaching by Moderate Ga 3+

Highly photoactive Ga3+-doped anatase modification of titania was prepared by homogeneous hydrolysis of aqueous solutions mixture of titanium oxo-sulphate TiOSO4 and gallium(III) nitrate with urea. Incorporation of Ga3+ into the anatase lattice has a clear positive effect on the photocatalytic activity under UV and Vis light irradiation up to a certain extent of Ga. Ga3+ doping decreased the size of the crystallites, increased surface area, and affected texture of the samples. Higher amount of gallium leads to the formation of a nondiffractive phase, probably photocatalytically inactive. The titania sample with 2.18 wt.% Ge3+ had the highest activity during the photocatalysed degradation in the UV and visible light regions; the total bleaching of dye Orange II was achieved within 29 minutes. Ga concentration larger than 5% (up to 15%) significantly inhibited the growth of the anatase crystal domains which formed the nondiffractive phase content and led to remarkable worsening of the photobleaching efficiency

Metal deposition in absence of convective mass transport in polymer gel electrolytes: a model of lithium anode in batteries

Zkoumáno bylo ochuzení PMMA gelové elektrody obsahující binární elektrolyt (chloristan kademnatý Cd(ClO4)2 v propylen karbonátu PC). Impedanční spektra byla měřena před a po záznamu voltamogramu při elektrodepozici kadmia. Vyhodnoceno bylo zvýšení odporu elektrolytu vlivem polarizačních ztrát a kapacity jednotlivých komponent. Všechny tyto parametry ukazují silný úbytek iontů, který je známý v Li polymerních sekundárních článcích, a který byl snížen, když část chloristanu kademnatého byla nahrazena odpovídající částkou chloristanu lithného LiClO4 jako indiferentního elektrolytu.The depletion of PMMA gel polymer electrode containing a binary electrolyte (cadmium perchlorate Cd(ClO4)2 in propylene carbonate PC) has been investigated. Impedance spectra were measured before and after recording a voltammogram of cadmium electrodeposition. The increase of electrolyte resistance, of polarisation resistance, and capacity component were evaluated. All these parameters indicate a strong depletion, which is known in Li polymer secondary cells, and which was lowered if a part of cadmium perchlorate was replaced by corresponding amount of LiClO4 as an indifferent electrolyte

Capacity of a glassy carbon electrode in propylene carbonate based electrolytes

The capacity of glassy carbon in aprotic salt solutions in propylene carbonate (PC) is investigated as an approach to the optimalisation of electrochemical supercapacitors. The strong influence of water residuum on capacities at negative potentials is indicated. The capacities exhibit a shallow minimum at potential from 0 V to +0.5 V (vss. Cd/Cd2+ reference electrode) and they increase with increasing electrolyte concentration. The admittance of the electrode in pure PC (as received) is by 2 – 3 orders of magnitude smaller. Undoubtedly, the properties of ions in solution influence the capacity by a factor not exceeding 2 to 5

Impact of Ge4+ Ion as Structural Dopant of Ti4+ in Anatase: Crystallographic Translation, Photocatalytic Behavior, and Efficiency under UV and VIS Irradiation

Nanometric particles of germanium-doped TiO2 were prepared by homogeneous hydrolysis of TiOSO4 and GeCl4 in an aqueous solution using urea as the precipitation agent. Structural evolution during heating of these starting Ge-Ti oxide powders was studied by X-ray diffraction (XRD) and high-temperature X-ray powder diffraction (HTXRD). The morphology and microstructure changes were monitored by means of scanning electron microscopy (SEM), Raman and infrared spectroscopy (IR), specific surface area (BET), and porosity determination (BJH). The photocatalytic activity of all samples was determined by decomposition of Orange II dye under irradiation at 365 nm and 400 nm. Moderate doping with concentration upto value 2.05 wt.% positively influences azo dye degradation under UV and Vis light. Further improvement cannot be achieved by higher Ge doping. Effect of the annealing (200, 400, and 700°C) on photocatalysis and other properties has been assessed

Electrochemical activity of manganese oxide/carbon based electrocatalyst – comparison with platinum/carbon electrocatalysts

International audienceElectrocatalysts prepared by chemical deposition of MnOx on carbon were tested successfully for the oxygen reduction reaction (ORR) in 1 M KOH solution using the rotating disk electrode (RDE). Nickel or magnesium doped MnOx/C exhibit better activity towards ORR than undoped MnOx/C. In comparison, the benchmark catalyst, 10 wt% Pt/C from E-Tek, exhibits ORR activity close to those of the doped MnOx/C catalysts. We believe that the doping transition metals stabilize an intermediate MnIII/MnIV phase, which favors oxygen bond splitting, and thus enhances ORR rate. In consequence these doped MnOx-based materials exhibit remarkable ORR catalytic activity