# Progress in the Development of Electrodeposited Catalysts for Direct Liquid Fuel Cell Applications
## 3 Electrodeposition on Non-Carbon Substrates
However, the increase in thickness of the so formed TiO2, with an increase in the number of polarization cycles, hindered the further formation of noble metal crystal nuclei. SEM images displayed the formation of noble metal smooth bead arrays with good dispersion. Electrochemical studies showed that the well dispersed arrays of Pt and Pd on TiO2 exhibited higher surface area, good characteristic features of metal surface electrochemistry, and comparable ORR activities with respect to the best Pt, Pd catalysts synthesized by other methods. They proposed that these smooth metal bead arrays could be used as micro disc array electrodes. [PERSON] et al. [69] reported on the synthesis and application of Pd/titania nanotubes/titanium (Pd/TNT/Ti) by pulse electrodeposition for ORR in fuel cells. The authors studied the influence of synthesis conditions on the performance of Pd/TNT/Ti electrode in detail. The authors concluded that the Pd/TNT/Ti, with better control of sensitization, activation conditions on the TNT/Ti surface before the Pd electrodeposition, will have an acceptable catalytic activity for ORR. They also reported that the pulse anodic current oxidation method is superior to the direct method for synthesising highly ordered and uniformly crystalline TNTs. Another promising study of this kind of material is utilizing Ti meshes, which show good conductivity and are electrochemically stable and, therefore, can be good support for a wide range of electrocatalysts. Mesh-based anodes consist of only one layer, which allows the electrode to be thin. Additionally, electrodes based on meshes do not need to contain Teflon because they are more hydrophilic than conventional electrodes [70]. [PERSON] and his co-workers [70, 71, 72, 73] investigated a range of Pt and Pd based catalyst coated on to a titanium mesh support prepared by electrodeposition from chloride precursors, for oxidizing a range of organic fuels, viz., formic acid, dimethoxymethane (DMM), trimethoxymethane (TMM), ethylene glycol, ethanol, and methanol. The results concluded that PtRu/Ti and PtSn/Ti could be efficient catalysts for the oxidation of direct organic liquid fuels. Results from Figure 5 reported by [PERSON] et al. [71] demonstrated that the mesh-based electrodes could provide respectable power densities when direct liquid fuels are employed at near ambient temperatures. Similarly, TiN possess certain superior characteristics such as high electrical conductivity (4000 S cm\({}^{-1}\)), density (5.1 g cm\({}^{-3}\)) to carbon (1190 S cm\({}^{-1}\), 1.9 g cm\({}^{-3}\)), facilitates the formation of metal catalyst layer with low thickness, when supported on TiN offering low mass transfer limitations in contrast with carbon [74]. Considering this, one of the promising routes for developing new generation support is the investigation of TiN as a highly conductive specific surface area support for Pt, Pt-Ru/Sn catalysts. Indium tin oxide (ITO) is another kind of material that has good electronic conductivity and high optical transparency, widely used in areas such as an organic light emitting diode and photo voltaic devices. [PERSON] et al. [75] studied the electrochemical deposition of Pd nanoparticles (NPs) on ITO substrates by varying the scan rate, and the number of cycles of potential scan using cyclic voltammetry (CV) technique and the activity towards formic acid oxidation was compared. The size and amount of the NPs deposited at a low scan rate, and high cycle number was shown to increase compared with the NPs deposited vice-versa (high scan rate, low cycle number). However, the electrochemical oxidation of formic acid results displayed that the performance of the latter was higher than that of the former. The authors concluded that large particle size of the NPs deposited at a low scan rate and high cycle number was responsible for its low activity. Table 3 shows the Pt and Pd-catalysts electrodeposited employing different modes of deposition on various non-carbon supports for applications in DLFCs involving other organic molecules as fuels.