# Progress in the Development of Electrodeposited Catalysts for Direct Liquid Fuel Cell Applications
## 2 Progress in the Electrodeposition of Carbon Supported Pt and Pd Catalysts
### Electrodeposition of Pt
The resulting uncatalysed carbon electrode consisted of two layers, i.e., a hydrophobic layer followed by a hydrophilic layer. Pulse electrodeposition was employed to deposit Pt from H2 PtCl6 and HCl on the carbon substrate. The catalyst so synthesized was used as the cathode, and Pt/C from E-TEK was used as the anode. Back scattered scanning electron microscopy (SEM) image showed that the thickness of the cathode catalyst is lower than that of the anode catalyst layer. Electron probe microanalysis studies showed the concentration profile of pulse electrodeposited Pt decayed with increasing distance from the membrane to gas diffusion layer (GDL). In contrast, a uniform profile was observed in the E-TEK anode. Fuel cell polarization studies showed that the MEA containing the pulsed electrodeposited Pt cathode (Pt loading--0.32 mg cm\({}^{-2}\)) displayed higher current densities at lower Pt loadings than that of the commercial Pt/C catalyst powder coated electrodes (TKK--46 wt %; Pt loading--0.40 mg cm\({}^{-2}\)) at a given potential when operated under same conditions. [PERSON] and [PERSON] [32] aimed at increasing the utilization of Pt catalysts by lowering the catalyst loadings in the electrode. The study emphasised on the electrodeposition of Pt on an uncatalysed carbon electrode (UCE), i.e., glassy carbon (GC) rotating disc electrode (RDE) coated with a thin layer of Nafion-bonded Vulcan from an aqueous chloropolatinic acid (H\({}_{2}\)PtCl\({}_{6}\)) solution. Moreover, the influence of Nafion content on the effective utilization of Pt particles towards oxygen reduction reaction (ORR) was also studied. Firstly, the behaviour of GC RDE and Pt RDE (a layer of 20 wt % Pt/C commercial E-TEK catalyst bonded with Nafion on RDE) were studied in an aqueous H\({}_{2}\)PtCl\({}_{6}\) solution with HCl as the supporting electrolyte. Secondly, Pt was electrodeposited on both the electrodes and the electrocatalytic ability of the prepared electrodes towards ORR was tested. The authors concluded that the Pt RDE exhibited a better ORR activity than the 20 wt % Pt/C commercial E-TEK catalyst due to its Pt deposition at the carbon support-electrolyte interface. Such an improvement was primarily related to the increased utility of Pt. The findings demonstrated a very low current efficiency for Pt deposition under acidic aqueous conditions, where hydrogen evolution was unavoidable. Since then, there have been many efforts and attempts to decrease the Pt catalyst loading while increasing the mass activity. [PERSON] et al. [33] developed a new method for depositing Pt nanoparticles on glassy carbon substrate using different Pt precursor salts by electrodeposition. A platinum precursor is brought into contact with the carbon-Nafion layer, and the resulting solution is sprayed on a glassy carbon disc, electrodeposited using the pulsed electrochemical deposition (PED) technique. The advantage of this method is that it activates not only the interface of the electrode surface but also the layer in its full depth. Electron micrographs and X-ray diffraction (XRD) characterization verified the nanocrystalline shape of the Pt particles. For comparison, Pt nanoparticles were also deposited by the constant current technique. Among the Pt precursors used, hexachloroplatinic acid (H\({}_{2}\)PtCl\({}_{6}\)) precursor was turned out to be the most suitable for this preparation technique. The results showed an increased catalytic activity towards methanol oxidation for the PED Pt nanoparticles. The same group extended their work to the synthesis of Pt-Ru catalysts with varying Ru content, i.e., from 10-60 at %. The Pt-Ru catalyst with 50 at. % Ru was identified to be the most active for methanol oxidation due to the oxyphilic nature associated with the addition of Ru [34]. Since then, numerous efforts have been made to develop the Pt-Ru catalysts towards improving the performance of the methanol oxidation in DMFCs.