Determination of ionic resistance and optimal composition in the anodic catalyst layers of DMFC using AC impedance

Zhao, Xinsheng; Fan, Xiaoying; Wang, Suli; Yang, Shuai; Yi, Baolian; Xin, Qin; Sun, Gongquan

doi:10.1016/j.ijhydene.2005.01.006

Cited by 55 publications

(41 citation statements)

References 20 publications

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“…The 2 M methanol fuel was supplied at 3 mL min -1 ,O 2 at 500 sccm, and again Nafion-117 was used as membrane. A very promising DMFC performance was reported by Zhao et al [39]. They reported a maximal power density of 217 mW cm -2 at 75°C for a total Pt + Ru loading of 4 mg cm -2 , but, otherwise similar conditions as used in this work [39].…”

Section: Original Research Papersupporting

confidence: 67%

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The Influence of Pt Loading, Support and Nafion Content on the Performance of Direct Methanol Fuel Cells: Examined on the Example of the Cathode

et al. 2011

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Nano‐sized Pt colloids were prepared using the polyol method and supported on Ketjen black EC 600J (KB), Vulcan XC‐72 (VC) and high surface area graphite 300 (HG). The effects of the Nafion ionomer content, and the Pt loading of the cathode catalyst layer as well as the Pt loading on the support on the performance of direct methanol fuel cells (DMFCs), were studied. The membrane electrode assemblies (MEAs) were analysed using current–voltage curves, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and adsorbed CO stripping voltammetry. Optimum Nafion to carbon (N/C) ratios (N/C being defined as the weight ratio of the Nafion ionomer to the carbon) were determined. The optimum N/C ratios were found to depend on the support as follows, 1.4, 0.7 and 0.5 for Pt/KB, Pt/VC and Pt/HG, respectively and to be independent of the Pt/C loading range of 20–80 wt% tested in this work. The highest DMFC performances, as well as the highest electrochemical active surface areas, and improved gas diffusivities, were achieved using these ratios. For the catalysts prepared in this work, the average Pt crystallite size was found to decrease with increasing surface area of the support for a particular Pt loading. MEAs made using KB as support and the optimal N/C ratio of 1.4 showed the best performances, i.e. higher than the VC and HG supports for any N/C ratio. The highest DMFC performance was observed using 60 wt% Pt on KB cathode electrodes of 1 mg Pt cm–2 loading and an N/C value of 1.4. For all three supports studied, the 60 wt% Pt on carbon loading resulted in the best DMFC performance. This may be linked to the Pt particle size and catalyst preparation method used in this work. In comparison to literature results, high DMFC performances were achieved using relatively ‘low' Pt and Ru loadings. For example, a maximum power density of >100 mW cm–2 at 60 °C was observed using a 1 mg Pt cm–2 cathode loading and a 2 mg PtRu cm–2 anode loading.

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Section: Original Research Papersupporting

confidence: 67%

“…A very promising DMFC performance was reported by Zhao et al [39]. They reported a maximal power density of 217 mW cm -2 at 75°C for a total Pt + Ru loading of 4 mg cm -2 , but, otherwise similar conditions as used in this work [39]. The latter is achieved utilising an optimised anode of 15 wt% Nafion content, i.e.…”

Section: Original Research Papersupporting

confidence: 60%

The Influence of Pt Loading, Support and Nafion Content on the Performance of Direct Methanol Fuel Cells: Examined on the Example of the Cathode

et al. 2011

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“…An appropriate amount of the freeze dried powder is then placed into a stainless steel stencil and hot pressed at 135°C for 1 min. at 75 kg cm -2 onto a piece of 6.45 cm 2 Toray carbon paper (10 wt.% wet proofed, TGPH-060, E-Tek). The stencil is a mask made out of a flat stainless steel plate exposing an area of 6.45 cm 2 .…”

Section: Electrodesmentioning

confidence: 99%

“…In fact, it has been proposed in previous work that less than 7 lm of the DMFC anode [23] is active due to proton conductivity limitations in the catalyst layer. In the case of DMFCs, only a few studies [2,24] are available, hence, possible measurement procedures for R p are evaluated and discussed in this work. For PEM fuel cells, the measurement of R p has been well established [18][19][20]25].…”

Section: Determination Of R Pmentioning

confidence: 99%

“…For example, electrodes are often made by pasting, brushing or spraying a catalyst ink on the membrane or a carbon based diffusion layer [1][2][3][4][5]. These techniques involve many important variables, most of which are not reported in their entirety in the literature, as for example, the viscosity of the ink solution and the exact composition of the ink (e.g., the solvent to catalyst powder ratio and ionomer content), the spraying pressure and distance, as well as the air to ink ratio.…”

Section: Introductionmentioning

confidence: 99%

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DMFC electrode preparation, performance and proton conductivity measurements

et al. 2008

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A method that involves stenciling electrodes using dry powders for fuel cells is described and compared to anodes and cathodes prepared by the traditional spraying method using catalyst inks. Methods to determine the proton conductivity of the DMFC anode layer are also discussed. The stenciling method allows for the preparation of highly reproducible membrane electrode assemblies (MEAs) utilizing little waste material. MEAs can be prepared in a controlled manner using the stenciling technique. The resulting morphology of the as-prepared electrodes is observed to be dependent on the preparation method, while the thickness of the once hot-pressed catalyst layers appears to be independent of the preparation method. Stenciled anodes of the same catalyst loading were found to show a lower proton resistance (R p ) than sprayed anodes. However, the lower R p value was not sufficient to result in a measurable increase in the performance of a direct methanol fuel cell (DMFC); as in fact, the average steady-state DMFC performance was found to be the same using sprayed or stenciled electrodes. The DMFC performance was found to be strongly dependent on the Nafion content and large increases in the Nafion content were needed to increase the DMFC performance measurably. Even though thick electrodes were prepared in this work, the R p values of the stenciled anodes were found to be comparable to results reported in the literature for much thinner electrodes made using high metal catalyst loadings on carbon. This observation is most probably due to the higher Nafion content used in this work.

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Impedance Spectroscopy

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Determination of ionic resistance and optimal composition in the anodic catalyst layers of DMFC using AC impedance

Cited by 55 publications

References 20 publications

The Influence of Pt Loading, Support and Nafion Content on the Performance of Direct Methanol Fuel Cells: Examined on the Example of the Cathode

The Influence of Pt Loading, Support and Nafion Content on the Performance of Direct Methanol Fuel Cells: Examined on the Example of the Cathode

DMFC electrode preparation, performance and proton conductivity measurements

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