Anode catalyst loading

In this study, we investigated the effects of anode catalyst loading and oxidant on the performance of DFAFC at various temperatures to better understand the significance of anode catalyst in a DFAFC system. 

Fig. 4. Effect of anode catalyst loading on the DFAFC performance.

Figure 5. Graph illustrating reduction of cathode carbon corrosion during start-stop with (a) corrosion-resistant carbon support (Gr-Vulcan) and (b) lower anode catalyst loading (0.05 mgpt/cm2). The base case is Vulcan and 0.40 mgpt/cm2 anode loading.

Even more important is the fact that most PEM materials (see below) are also quite permeable for water and methanol. Thus, thin membranes lead to substantial transport of these molecules from the anode side to the cathode (e. g., [25-29]). The permeation of methanol in the DMFC is undesirable for the obvious reason that it reduces the cell power ( mixed potential formation ), because no electrical work is generated in a cathodic oxidation reaction. Furthermore methanol on the cathode is unfavorable because it can block adsorption sites needed for the oxygen reduction reaction. The presence of methanol may even alter the rate constant of the oxygen reduction reaction. A typical solution to the problem of methanol transport is the use of dilute aqueous solutions of methanol, which assures almost complete oxidation when the anodic catalyst loading is high enough [30],... 

An approach described most recently for maximizing CO tolerance at relatively low anode catalyst loadings involves a combination of a CO-tolerant electrocatalyst, for example, a PtRu alloy and a separate chemical oxidation catalyst layer of zero... 

Fuel-cell tests offer the ultimate verification of the usefulness of an electrocatalyst by determining its long-term stability under real operating conditions. They were performed on single cells using electrodes of 50 cm and an anode catalyst loading of 0.2 mg... 

Figure 2 shows the material cost ( /kilowatt electrical [kWe]) versus cathode platinum loading for stacks operating at 3 atmospheres, 160°C, and 0.8 volts with direct hydrogen and reformate. Assumptions in this analysis include use of an alloy catalyst having a kinetic activity two times that of platinum, a unit cell resistance of 0.1 ohm centimeter squared (cm ), and an anode catalyst loading equal to one half the cathode loading. 

Fig. 3.5 Polarization curves of the DEFC based on a 20 % PtsCri/C cathode at 60 °C and 90 °C, with a 20 % PtSn/C anode. Catalyst loading 1 mg/cm. Membrane Nafion 117. Ethanol concentration 1 M...

Regarding the co-catalytic role of Sn for methanol oxidation, on the other hand, the experimental evidence is less conclusive compared to the case of CO oxidation. Colmati et al. prepared PtSn/C catalyst formulations (9 1 and 3 1 atomic ratio) using formic acid reduction and compared the activity with commercial (E-TEK Inc.) Pt/C and PtSn (3 1)/C, including DMFC foel cell experiments [79]. Unfortunately, no comparison with PtRu was presented. Employing 0.4 mg cm anode catalyst load and 3 atm O2 pressure, the maximum fuel cell power output at 343 K was obtained with PtSn (3 1) produced by the formic acid method, 400 mW... 

Figure 4.10. DMFC polarization curves using PtSn anode catalysts produced by a microwave-assisted polyol method. Anode catalyst load 4 mg cm , 2 M CH3OH with 2 ml min cathode Pt/C 3 mg cm , O2 pressure not specified in the original source, O2 flow rate 500 cm min 353 K [85]. (Reproduced from Electrochemistry Communications, 8(1), Liu Z, Guo B, Hong L, Lim TH, Microwave heated polyol synthesis of carbon-supported PtSn nanoparticles for methanol electrooxidation, 83-90, 2006, with permission from Elsevier.)...

In order to improve the methanol utilization efficiency in DMFC, Wilkinson et al. patented the multilayer anode concept, where a number of CCDLs are stacked together to provide an enhanced reaction zone volume [303]. They reported that for the same total anode catalyst load, the distribution of the earbon-supported PtRu catalyst onto three separate diffusion layers (carbon fiber sheets, 300 pm total thickness) enhanced the methanol utilization efficiency by 33% compared to a single CCDL at a constant current density of 200 mA cm and 388 K. 

Anode Anode Catalyst Loading J 0.5V (mA cm Pmtx ") (mWcm" ) I Pmax (mAcm" ) (mV) T(°C) Ethanol Feed Membrane Reference... 

Reference Anode Catalyst Loading Cathode Catalyst Loading Current Density Temperature Potential Duration... 

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