# 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  
It is well known that the performance of an electrocataly is strongly dependent on the method of its preparation. Besides the preparation methods, the performance of the catalyst is evaluated in terms of its activity towards reactions, which increases with increase in its active surface area and decrease in size of the metal particle [24; 25]. Therefore, the catalysts are supported on high surface area conductive carbon substrates to improve their dispersion while maintaining the specific activity. Carbon supports, especially Vulcan, synthesized from the pyrolysis of hydrocarbons and having polycrystalline particle nature was widely used as a support for Pt and Pd catalysts in low temperature fuel cells. Vulcan support is resistant to corrosion and has a high surface area. Metal catalysts are typically synthesized as nanoparticles for obtaining a high surface area. These nanoparticles are essential to be formed in the porous electrodes for effectively promoting reactions in electrocatalytic applications such as fuel cells and sensors [26].  
Since the catalysts are bonded to support, the support (typically carbon-based) will influence the activity of the catalyst potentially, which in turn depends on the method of preparation of the metal catalyst. The presence of finely distributed catalyst metal particles on support facilitates mass transfer of the fuel/oxidant into the pores and release of products at the catalyst surface. Various synthesis methods of preparation have been adopted to improve the dispersion of noble metal particles supported on different carbon  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type of DLFC** & **Anode Reaction** & **Cathode Reaction** & **Overall Reaction** \\ \hline DMFC 1 & CH\({}_{3}\)OH + H\({}_{2}\)O \(\rightarrow\) CO\({}_{2}\) + 6H\({}^{+}\) + 6e\({}^{-}\) & 3/2 O\({}_{2}\) + 6H\({}^{+}\) + 6e\({}^{-}\) \(\rightarrow\) 3H\({}_{2}\)O & CH\({}_{3}\)OH + 3/2 O\({}_{2}\)\(\rightarrow\) CO\({}_{2}\) + 2H\({}_{2}\)O \\ \hline DEFC 2 & C\({}_{2}\)H\({}_{3}\)OH + 3H\({}_{2}\)O \(\rightarrow\) 2 CO\({}_{2}\) + 12H\({}^{+}\) + 12e\({}^{-}\) & 3 O\({}_{2}\) + 12H\({}^{+}\) + 6e\({}^{-}\)\(\rightarrow\) 3H\({}_{2}\)O & C\({}_{2}\)H\({}_{3}\)OH + 3H\({}_{2}\)O \(\rightarrow\) 2 CO\({}_{2}\) + 3H\({}_{2}\)O \\ \hline DEFC 3 & HCOOH + H\({}_{2}\)O \(\rightarrow\) CO\({}_{2}\) + 2H\({}^{+}\) + 2e\({}^{-}\) & 1/2 O\({}_{2}\) + 2H\({}^{+}\) + 2e\({}^{-}\)\(\rightarrow\) H\({}_{2}\)O & HCOOH + 1/2 O\({}_{2}\)\(\rightarrow\) CO\({}_{2}\) + H\({}_{2}\)O \\ \hline DEFC 4 & C\({}_{2}\)H\({}_{4}\)O\({}_{2}\) + 2H\({}_{2}\)O \(\rightarrow\) 2 CO\({}_{2}\) + 10H\({}^{+}\) + 10e\({}^{-}\) & 5/2 O\({}_{2}\) + 10H\({}^{+}\) + 10e\({}^{-}\) \(\rightarrow\) 10H\({}_{2}\)O & C\({}_{2}\)H\({}_{4}\)O\({}_{2}\) + 2H\({}_{2}\)O \(\rightarrow\) 2 CO\({}_{2}\) + 5H\({}_{2}\)O \\ \hline DGFC 5 & C\({}_{3}\)H\({}_{6}\)O\({}_{3}\) + 3H\({}_{2}\)O \(\rightarrow\) 3 CO\({}_{2}\) + 14H\({}^{+}\) + 14e\({}^{-}\) & 3/2 O\({}_{2}\) + 6H\({}^{+}\) + 6e\({}^{-}\)\(\rightarrow\) 3H\({}_{2}\)O & C\({}_{3}\)H\({}_{8}\)O\({}_{3}\) + 7/2 O\({}_{2}\)\(\rightarrow\) 3 CO\({}_{2}\) + 4H\({}_{2}\)O \\ \hline \hline \end{tabular}  
* DMFC: Direct Methanol Fuel Cells; 2 DEFC: Direct Ethanol Fuel Cells; 3 DEFC: Direct Formic Acid Fuel Cells; 4 DEFC: Direct Ethylene Glycol Fuel Cells; 5 DEFC: Direct Glycerol Fuel Cells.  
\end{table}
Table 1: Table listing the DLFCs that are most commonly studied and associated electrochemical reactions involving supported Pd catalysts. Reprinted with permission from [16].  
-based substrates. This section will focus on developing electrodeposited noble metal (Pt and Pd) catalysts supported on carbon and carbon-based materials.