Titanium fuel cell catalysts

Nanostructured TiOj has also been utilized as PEMFC catalyst supports with dimensions well below 100 nm. Like other TiOj structures, these materials also inherit high stability, high surface areas, and moderate electrical conductivity. Titanium oxide nanotubes are of particular interest for fuel cell catalyst supports due to their abihties to form porous networks, disperse catalytic metals upon the surface... 

Transition metal carbides, such as tungsten carbide and its alloys, tantalum carbide, titanium carbide, and molybdenum carbide (Cowling et al, 1970,1971 Voorhies et al., 1972 Scholl et ah, 1992,1994 Borup et al., 2007), have been studied as catalysts for electrochemical reactions. However, it has been found that these transition metal carbides are unstable under high potentials and in acid solution, and this limits their application as PEM fuel cell catalysts (Borup et al., 2007). Transition metal nitrides have been studied as electrochemical catalysts in PEM fuel cell environments, and Zhong et al. (2006) showed that molybdenum nitride supported on carbon powder resulted in a cell performance of about 0.3 V at 0.2 A cm, and the catalyst was stable for 60 h of cell operation. However, the long-term performance durability is still questionable. 

Titanium dioxide supported gold catalysts exhibit excellent activity for CO oxidation even at temperatures as low as 90 K [1]. The key is the high dispersion of the nanostructured gold particles over the semiconducting Ti02 support. The potential applications of ambient temperature CO oxidation catalysts include air purifier, gas sensor and fuel cell [2]. This work investigates the effects of ozone pretreatment on the performance of Au/Ti02 for CO oxidation. 

For obvious reasons related to the necessary reduction of the amount of catalyst used in fuel cells, ORR has been studied on thin films of platinum deposited onto glassy carbon or titanium [73, 79] and on small metal particles on carbon [80-82]. The reduction of the Pt film thickness (<1 nm), as well as of the size of the particles (diam. < 3 nm), induces a moderate loss of activity attributed to differences in the adsorption of O2 on the metal surface. 

Electroless deposition of the catalytic Pt or Pt-Ru layer was proposed for the preparation of electrodes in microdirect methanol fuel cells.53 A porous silicone substrate is prepared by the anodic etching in HF-ethanol-water (1 1 1) solution. After the etching, at the surface of porous silicon substrate, a thin film of titanium is sputtered and then a film of Pt or Pt-Ru alloy with thickness of about 150-200 nm was electroless deposited. The electrodes prepared in this way helped in minimization of the fuel cell size and increased the reactive area of the catalyst over the silicon electrode surface. 

Ignaszak A, Song C, Zhu W, Zhang J, Bauer A, Baker R, et al. Titanium carbide and its core-shelled derivative title=TiC Ti02 as catalyst supports for proton exchange membrane fuel cells. Electrochim Acta 2012 69(0) 397—405. 

Kakinuma K, Wakasugi Y, Uchida M, Kamino T, Uchida H, Deki S, et al. Preparation of titanium nitride-supported platinum catalysts with well controlled morphology and their properties relevant to polymer electrolyte fuel cells. Electrochim Acta 2012 77 279-84. 

Rajalakshmi, N., Lakshmi, N., and Dhathathreyan, K.S. (2008) Nano titanium oxide catalyst support for proton exchange membrane fuel cells. / /. Hydrogen Energy, 33, 7521-7526. 

With this respect, the work from Atanasoski and coworkers is promising (compare section Transition Metal Carbides, Nitrides and Chalcogenides ) [35], By performing a heat treatment of their sputtered C-N iFe Aims, the activity was drastically enhanced but still much lower compared to macrocycle-based catalysts. However, when titanium carbide was used as support instead of carbon, a high stability was obtained. The fact that by changing the support, an essentially better durability was obtained is an important result as it shows that even for catalysts based on molecular centers, alternative support materials can be utilized and that the interaction between the support and the catalytic centers might be cmcial for the optimization of those catalysts for a fuel cell application. 

Huang, S.-Y., Ganesan, R, and Popov, B. N. 2010. Electro catalytic activity and stabihty of niobium-doped titanium oxide supported platinum catalyst for polymer electrolyte membrane fuel cells. Appl. Catal, B 96 224-231. 

Titanium dioxide or titania (TiOj) has been considered a promising alternative catalyst support in low-temperature fuel cells because of its excellent corrosion resistance, good stability in acid, and tolerance to high potentials (Diebold, 2003 George et al., 2008). As an electrocatalyst support, TiOj deposited... 

The German company Siemens later modified these electrodes with skeleton metal catalysts. Small amounts of titanium were added to the anodic nickel catalysts, and nickel, bismuth, and titanium were added to the cathodic silver catalysts. Fuel cells with such electrodes and a matrix electrolyte operated at 95°C and a current density of 400 mA/cm had a working voltage of 0.8 to 0.9 V. 

Kakinuma, K., Wakasugi, Y., Uchida, M., Katnino, T., Uchida, H. Watanabe, M. Electrochemical activity and durability of platinum catalysts supported on nanometer-size titanium nitride particles for polymer electrolyte fuel-cells. Electrochem. 79 (2011), pp. 399-403. 

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