# Progress in the Development of Electrodeposited Catalysts for Direct Liquid Fuel Cell Applications
## 5 Fuel Cell Polarisation
Ru/C with different Ru wt % (i.e., 8, 17, and 30 wt %) was initially synthesised utilising the polyol procedure and ethylene glycol as a reducing agent. Electroreduction of Pt was performed by impregnating the Pt-precursor on Ru/C coated carbon paper followed by square wave pulse deposition technique. The authors demonstrated that, when compared to the standard electroreduction method, their synthesis process could result in more uniform Pt particles with smaller size. The authors achieved a peak power density of 80 mW cm\({}^{-2}\) when tested as an anode catalyst at 80 \({}^{\circ}\)C in a single DMFC with a 2 M fuel concentration. The same authors extended it further and tested the oxidation performance of the electrodeposited Pt-Pd, nanoleafs employing formic acid as the liquid fuel [98,99]. However, in a passive mode of operation, this design inhibits the release of organic fuel oxidation products such as CO\({}_{2}\) from the anode. This results in a noticeable change in mass-transport restrictions at the anode, resulting in fuel deficiency at the anode catalyst layer [120]. Recognizing the significance of mesh-based electrodes as viable and advantageous alternatives to standard GDLs, tests were carried out using various organic compounds as liquid fuels and metal mesh coated Pt-based catalysts as anodes. Metal meshes are substantially thinner and, in addition to operating as an effective current collector, can provide more efficient transportation of methanol to the catalyst layer and improve CO\({}_{2}\) removal capabilities. Earlier studies demonstrated that the metal mesh electrodes enhanced fuel distribution and performance than the circular perforated current collectors [121]. Amongst the different mesh based electrodes such as stainless steel [122], gold plated stainless steel mesh [123], Ti mesh is identified as the potential substrate for the an ode catalyst due to their superior physicochemical properties, stability, and good electrical conductivity than the others [72]. Moreover, Ti mesh was demonstrated to offer (i) good distribution of reactant (liquid organic fuels: methanol, ethanol, formic acid, etc.) to the catalyst layer, (ii) act as catalyst support, and (iii) a current collector. Such a configuration was proved to (i) improve the performance of self-breathing/passive DLFCs, (ii) effectively decrease the overall thickness of the MEA, and (iii) the corresponding losses associated with the resistances offered by the traditional ones [71; 122; 123; 124]. [PERSON] et al. [71] designed a new clamping mechanism with reduced fuel leakage for a low temperature DMFC operating in an air-breathing mode (AB-DMFC) which limits cell resistance, tested them using Pt, Pt-Ru catalysts supported on Ti mesh synthesized by pulse electrodeposition. Multiple efforts were made to optimise the various Ti mesh-based MEA topologies for use in passive DMFCs. The single cell architecture was later extended to mini-stacks consisting of 2-cells, 6-cells, and the architecture built by [PERSON] et al. [71] is represented in Figure 10.  
The 6-cell stack demonstrated an open circuit potential of 2.9 V when tested with 2 M methanol and ambient air with a maximum power of 60 mW, allowing it to operate a small portable device. Table 6 lists the summary of the fuel cell test results that are conducted using different conditions and liquid fuels. Figure 10: Comparison showing the fuel cell assembly of (**a**) conventional 6-cell DMFC stack (recreated from [122]), and (**b**) the novel 6-cell AB-DMFC architecture proposed by [PERSON] et al.. Reprinted with permission from [71].