# Progress in the Development of Electrodeposited Catalysts for Direct Liquid Fuel Cell Applications
## 5 Fuel Cell Polarisation  
DLFCs are exceptionally attractive for low power and portable applications since they provide the convenience of fast recharging as well as a longer lifetime. However, there are  
Figure 9: Progress in the developments of shape controlled noble metal (Pt, Pd) structures synthesised by electrodeposition covering the period 2000–2020. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Fuel Cell Reaction** & **Catalyst** & **Technique** & **Electrolyte** & **Morphology** & **Dominant** & **Crystal Size,** **nm** & **Reference** \\ \hline EtOH Oxidation & Pd & SWP & 1 mM PdCl\({}_{2}\) + & Concave-disdyakis & [631] & - & [115] \\  & & & (ChChClUrea—1:2] & triaconthefical & & & \\ \hline HCOOH Oxidation & Pd & CV & \
\begin{tabular}{c} 5 mM PdCl\({}_{2}\) + \\ [ChCl:EG—1:2] \\ \end{tabular} & Nanoparticles & - & \(41\pm 5\) & [116] \\ \hline HCOOH Oxidation & Pd & PS &
\begin{tabular}{c} 6 mM PdCl\({}_{2}\) + \\ [Ch:EG—1:2] \\ \end{tabular} & Nanoparticles & - & \(41\pm 5\) & [116] \\ \hline \hline \end{tabular}  
* HCOOH: Formic acid; MeOH: Methanol; EtOH: Ethanol; ChCl: Choline chloride; EG: Ethylene glycol. 2 CV: Cyclic voltammetry; PS: Potentiostatic; SWP: Square wave potential.  
\end{table} 
Table 5: _Cont._various restrictions to the operational complexities of DLFCs, particularly with relation to cell design, in order to effectively replace the architecturally simpler batteries. Some of the obstacles impeding DLFC commercialization include an expensive electrocatalyst, liquid fuel crossover, and water management. One way of addressing these issues is to identify the best fuel delivery mode and develop an efficient fuel delivery system. Based on the fuel delivery mode, there are two basic types of DLFCs: passive and active [118,119]. An active system requires an external mechanism (such as pump, fan) to feed the fuel and oxidant. On the contrary, the feeding mechanism for fuel and oxidant to the anode is passive and is generally accomplished through natural diffusion processes without the usage of any auxiliary devices. The passive DLFC derives its oxidant fuel from natural breathing of atmospheric air, hence the name passive or self-breathing DLFCs. In comparison to active DMFCs, self-breathing DMFCs with an open cathode have distinct advantages such as simple structure, small size, and light weight, as they do not require the employment of a sophisticated auxiliary equipment system. For stacks, active ones are favoured over passive ones for low-power portable applications (e.g., laptops). For DLFCs to function effectively, they require ideal electrocatalysts with high activity in fuel oxidation and the oxygen reduction reaction for the anode and cathode, respectively. They should also have strong long-term stability, appropriate electrical conductivity, and a reasonable price. Although great efforts are being made around the world to develop novel electrocatalysts for fuel cells, most evaluations primarily discuss the findings of testing electrodeposited catalysts under the given operating conditions and pay minimal attention to real-time test results. There is a substantial amount of research in the literature devoted to the introduction of unique electrocatalytic systems that can be used as promising candidates for DLFCs. The majority of these experiments, however, are conducted in a typical three-electrode electrochemical cell. Likewise, the majority of the reviews that have been published so far have summarised the results based on the catalysts developed using wet chemical procedures. This section will provide an overview of the performance of electrodeposited Pt and Pd-based electrocatalysis evaluated recently by different researchers in DLFCs. A Teflon coated microporous backing layer, Nafion-bonded catalyst, and a macroporous carbon-based gas diffusion layer (GDL) constitute the most typical DLFC anode electrode configuration. [PERSON] et al. proposed a hybrid electrodeposition method for creating a bimetallic Pt-Ru catalyst based on carbon for methanol oxidation.