Polarization curve DMFC anode

Liquid-feed DMFC polarization curves with (a) Pt, (b) PtRu, and (c) PtRuOs anodes at 90°C, 0.5 MeOH, and O2 feeds. (K. L. Ley et al., Journal of the Electrochemical Society, 144,1543 (1997). Reproduced by permission of The Electrochemical Society.)... 

Figure 41. Comparison of localized polarization curves between experiments (a) and model predictions (b) for a 50 cm DMFC with an anode flow stoichiometry of 27 and a cathode air stoichiometry of 5 at 0.1 A/cm. ...

Fig. 53 Comparison of DMFC polarizations curves at 80 °C with anode feed of 0.5 M methanol solution and the air cathode operating at zero backpressure for a cell with a Nafion 115 membrane and a cell with a polyaromatic membrane of lower methanol permeability [105].

Omran et al. have proposed a 3D, single phase steady-state model of a liquid feed DMFC [181]. Their model is implemented into the commercial computational fluid dynamics (CFD) software package FLUENT . The continuity, momentum, and species conservation equations are coupled with mathematical descriptions of the electrochemical kinetics in the anode and cathode channel and MEA. For electrochemical kinetics, the Tafel equation is used at both the anode and cathode sides. Results are validated against DMFC experimental data with reasonable agreement and used to explore the effects of cell temperature, channel depth, and channel width on polarization curve, power density and crossover rate. The results show that the power density peak and crossover increase as the operational temperature increases. It is also shown that the increasing of the channel width improves the cell performance at a methanol concentration below 1 M. 

Figure 4.2. DMFC polarization behavior using aqueous methanol and solid polymer electrolyte (SPE Nafion 117) [52]. a) Anode half-cell polarization comparison between SPE and 0.5 M H2SO4, PtRu/C 0.5 mg cm, b) fuel cell polarization curve using 2 M CH3OH in water effect of temperature. PtRu/C coated Nafion 117 membrane. Note the anode and cathode catalyst loads in the case of fuel cell experiments were not specified in [52]. (Reproduced Ifom Journal of Power Sources, 47(3), Surampudi S, Narayanan SR, Vamos E, Frank H, Halpert G, LaConti A, Kosek J, Surya Prakash GK, and Olah GA, Advances in direct oxidation methanol fuel cells, 377-85, 1994, with permission fi-om Elsevier.)...

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.)...

Figure 13.9. Liquid-feed DMFC polarization curves at 90 C (a) Pt, (b) Pt-Ru (1 1), and (e) Pt-Ru-Os (65 25 10). Methanol (0.5 M) was delivered to the anode at a flow rate of 25 ml/min with ambient baekpressure. The oxidant was 10 psig dry O2 with a flow rate of 400 ml/min [38]. (Reprodueed by permission of ECS—The Electroehemieal Society, from Ley KL, Liu R, Pu C, Fan Q, Leyarovska N, Segre C, et al. Methanol oxidation on single-phase Pt-Ru-Os ternary alloys.)...

Figure 23.14. Impact of ruthenium on oxygen reduction performance (a) CO stripping scans for the cathode and anode, (b) steady-state anode polarization plots before and alter contamination of the eathode, (c) H2-air steady-state polarization curves, and (d) DMFC steady-state polarization curves. Methanol concentration 0.3 M, anode potential during contamination 1.3 V vs. hydrogen counter/quasi-reference electrode, cell temperature 75 °C [65]. (Reprinted by permission of ECS— The Electrochemical Society, from Piela P, Eickes C, Brosha E, Garzon F, Zelenaya P. Ruthenium crossover in direct methanol fuel cell with Pt-Ru black anode.)...

Yang et al. (2010) developed an EIS technique to characterize a DMFC under various operating conditions. A silver/silver chloride electrode was used as an external reference electrode to probe the anode and cathode during fuel cell operation. The external reference was sensitive to the anode and cathode as current was passed in the working DMFC. The impedance spectra and DMFC polarization curves were investigated systematically as a function of air and methanol flow rates, methanol concentration, temperature, and current density. Water flooding in the cathode was also examined. 

FIGURE 4.31 Analytical (lines) and experimental polarization curves of DMFC anode measured by Nordlund and Lindbergh (2004) for the indicated methanol concentrations and cell temperature of (a) 50°C and (b) 70°C. The fitting parameters are listed in Table 4.4. 

Kulikovsky, A. A. 2013a. Analytical polarization curve of DMFC anode. 

Figure 4.9 (a) TEM image of PtRu/DWNTs (50wt%). (b) SEM image of PtRu/DWNTs thin film, (c) Polarization curve of methanol oxidation in 05 M H2SO4 + 05 M methanol on PtRu/CNT catalysts. (d) Single DMFC with PtRu/CNTs anode catalysts [177]. 

Several authors have shown the fuel cell performance with varying PTFE content [103, 106, 108, 109]. Figure 7.16 shows the polarizatirais curves of DMFC with different contents of PTFE on the anode and cathode GDL respectively [82]. An excess of PTFE has an adverse effect on the fuel cell polarization as observed in both graphs. The better performance is attained with different PTFE amounts at the anode and the cathode, indicating that an optimum amount has to be chosen according to the particular material and application. This is related to the fact that different amounts of water are present in the anode and the cathode. While an aqueous solution is fed to the anode, water reaches the cathode mainly by transport from the anode through the membrane, because dried O2 or air is typically supply to the cathode. 

Figure 29. Polarization and power density curves at different temperatures of an active DMFC with a Pd/MWCNT anode (Pd loading 1 mg cm ), fuelled with an aqueous 2 M KOH solution of methanol (10 wt%). The inset reports the temperatures of fuel (left), cell (central), oxygen gas (right). Reprinted from Ref. 29, Copyright (2009) with permission from Elsevier.

Figure 13.8. DMFC polarization (a and c) and power density (b and d) curves of various catalysts at 75 °C (a and b) and 90 °C (c and d), respectively. Methanol concentration at the anode 1 mol with a flow rate of 1.0 mL min oxygen at cathode non-htunidified oxygen at a pressure of 0.2 MPa with a flow rate of 200 seem. Except for Pt-Ru black and Pt-Ru black (JM) with a Pt loading of 2.66 mg cm, the Pt loading of other anode catalysts is 1.33 mg cm. 40 wt% Pt/XC72 (Johnson Matthey) used as the cathode catal57st with a Pt loading of 1.4 mg cm [35]. (Reprinted from Journal of Power Sources, 168, Guo J, Sun G, Sun S, Yan S, Yang W, Qi J, et al. Polyol-synthesized PtRu/C and PtRu black for direct methanol fuel cells, 299-306, 2007, with permission from Elsevier.)...

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