Rutile electrode

Toyoda T, Tsuboya 1, Shen Q (2005) Effect of rutile-type content on nanostructured anatase-type Ti02 electrode sensitized with CdSe quantum dots characterized with photoacoustic and photoelectrochemical current spectroscopies. Mater Sci Eng C 25 853-857... 

The photolytic reduction of N2 at TiO -suspensions was at first reported by Schrauzer et al. Small amounts of NH3 and N2H4 were obtained as products. The highest activity was found with anatase containing 20-30 % rutile. Very low yields were also obtained with p-GaP electrodes under illumination It is much easier to produce NH3 from NO -solutions at CdS- and Ti02-particles using S -ions as hole scavengers . Efficiencies are not reported yet. Recently the formation of NH3 from NO was observed at p-GaAs electrodes under illumination. In this case NH3-formation was only found in the presence of transition metal ions or their complex with EDTA. 

X-ray diffraction conducted on the codeposited powder revealed that the deposit obtained from a suspension of gamma alumina, which had been partially converted to the alpha phase, contained both phases of alumina. Whereas, the powder codeposited from a suspension having a 50 50 mixture of alpha to gamma alumina powder, consisted only of the alpha phase. Using a parallel plate electrode configuration, Chen et al. [31] concluded that only alpha alumina can be codeposited. Chen also observed a difference in codeposition with copper when using two different phases of the titanium oxide particle system rutile readily codeposited but anatase titania did not... 

Technical electrodes usually consist of a mixture of Ru02 and TiC>2 plus a few additives. They are called dimensionally stable anodes because they do not corrode during the process, which was a problem with older materials. These two substances have the same rutile structure with similar lattice constants, but RuC>2 shows metallic conductivity, while pure TiCU is an insulator. The reaction mechanism on these electrodes has not yet been established the experimental results are not compatible with either of the two mechanisms discussed above [4]. 

Fujishima and Honda reported the splitting of water by the use of a semiconductor electrode of titanium dioxide (rutile) connected through an electrical load to a platinum black counter-electrode. Irradiation of the Ti02 electrode with near-UV light caused electrons to flow from it to the platinum counter-electrode via the external circuit. 

Figure 11.8 Schematic diagrams of the Fujishima-Honda cell using an illuminated Ti02 (rutile) semiconductor electrode and a platinum counter-electrode...

Giordano N, Antonucci V, Cavallaro S, Lembo R, Bart JCJ (1982) Photoassisted decomposition of water over modified rutile electrodes. Int J Hydrogen Energy 7 867-872... 

This chapter considers photoanodes comprised of metal oxide semiconductors, which are of relatively low cost and relatively greater stability than their non-oxide counterparts. In 1972 Fujishima and Honda [1] first used a crystal wafer of n-type Ti02 (rutile) as a photoanode. A photoelectrochemical cell was constructed for the decomposition of water in which the Ti02 photoanode was connected with a Ft cathode through an external circuit. With illumination of the Ti02 current flowed from the Ft electrode to the... 

Polycrystalline oxide materials, both undoped and doped, have been extensively examined for use as photoanodes. Ti02 electrodes have been prepared by thermal oxidation of a Ti plate in an electric furnace in air at 300-800°C (15-60 min) and in a flame at 1300°C (20 min) [27-30]. XRD analysis of thermally oxidized samples indicates the formation of metallic sub-oxide interstitial compounds, i.e. TiOo+x (x < 0.33) or Ti20i y (0 < y < 0.33) and Ti30 together with rutile Ti02 [27]. The characteristic reflection of metallic titanium decreases in intensity after prolonged oxidation (60 min) at 800° C indicating the presence of a fairly thick oxide layer (10-15 pm). Oxidation at 900°C leads to poor adhesion of the oxide film... 

Commercial Ti02 powder, such as P25 (Degussa or Nippon Aerosil [75]), are usually used to prepare the Ti02 photoelectrode. However, colloidal Ti02 solution prepared by hydrolysis of Ti(IV) alkoxides, such as isopropoxide and butoxide, has also been used to produce high-performance solar cells. Generally, anatase rather than rutile is more suitable for electrodes [76]. Preparation involves the following steps ... 

The largest titanium reserves in the world are in the form of anatase and titano-magnetite, but these cannot be worked economically at the present time. About 95 % of the world s production of ilmenite and rutile is used to produce TiOz pigments, the remainder for the manufacture of titanium metal and in welding electrodes. 

Fig. 17.6 1—V characteristics of a rutile Ti02 electrode in an aqueous solution containing 0.01 mol dm-3 sulfuric acid and 0.5 mol dm-3 potassium nitrate (a), and those obtained after addition of Fe(III) nitrate (2.0 mmol dm-3) to the solution (b). The potential was swept at a rate of 20 mV s 1.

Samples of the ceramic polycrystalline Ti02 (rutile) doped electrodes of the VxTi . x02 composition were studied at different vanadium content (0.001 < x < 0,05) in [128, 129]. It was shown that at x < 0,003 the EPR spectra perform a well resolved hyperfine structure (hfs) typical of V4+-doped rutile (Fig. 8.10), in which V4+ ions substituted Ti4+ ions in the crystal lattice. At 0.003 < x < 0.01, the dipolar broadening of the individual lines 8H occurred. At x > 0.01, in parallel with continuing broadening of the hfs lines, a broad single line appears (Fig. 8.11). Its part in the spectrum increased with the increase of vanadium content. 

A disc of reduced semiconducting rutile crystal 2 cm in diameter and 2 mm thick is heated in air for 10 s at 300 °C. After cooling, circular electrodes, lcm in diameter, are applied symmetrically to the two major surfaces. The chemical diffusion coefficient D for the oxidation reaction in reduced single-crystal TiC is given by... 

The titanium oxide film consists of rutile or anatase (31) and is typically 250-A thick. It is insoluble, repairable, and nonporous in many chemical media and provides excellent corrosion resistance. The oxide is fully stable in aqueous environments over a range of pH, from highly oxidizing to mildly reducing. However, when this oxide film is broken, the corrosion rate is very rapid. Usually the presence of a small amount of water is sufficient to repair the damaged oxide film. In a seawater solution, this film is maintained in the passive region from ca 0.2 to 10 V versus the saturated calomel electrode (32,33). 

The XRD of Sn02 electrode at different calcined temperature (Fig. 14.3) showed that the square rutile Sn02 can be detected at 400°C and 500°C pyrolysis temperature. When calcined temperature increased, a rutile Ti02 can also be found in the layer which might induce poor electrocatalysis of the electrodes. 

The XRD patterns of electrodes fabricated at different temperatures (Fig. 14.6) showed that rutile Sn02 was detected at every temperature. Diffraction lines of electrode prepared at 500° C are broadened, indicating the nanosized crystallites in the surface coating of the electrode. When the annealing temperature increases from 500 to 700°C, the intensity of the peaks increases sharply and it means that the crystal of electrode surface grows more integrated. Better electrocatalytic ability can be achieved. 

Iridium dioxide — Iridium oxide crystallizes in the rutile structure and is the best conductor among the transition metal oxides, exhibiting metallic conductivity at room temperature. This material has established itself as a well-known - pH sensing [i] and electrochromic [ii] material (- electrochromism) as well as a catalytic electrode in the production of chlorine and caustic [iii]. The oxide may be prepared thermally [iv] (e.g., by thermal decomposition of suitable precursors at temperatures between 300 and 500 °C to form a film on a substrate such as titanium) or by anodic electrodeposition [v]. 

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