(146a) A Microfluidic Fuel Cell as a Platform for Individual Fuel Cell Component Analysis

Fuel cell-based systems are promising alternative power sources for a range of energy conversion applications due to their high efficiency, high energy density and low emissions. For portable and transportation applications polymer electrolyte membrane (PEM)-based fuel cells, utilizing either hydrogen or small organics as fuels, are considered the most promising configuration [1]. Unfortunately, for widespread commercialization of fuel cell technologies to be realized, significant reductions in system costs and improvements in durability are required. For example, the cathodic oxygen reduction reaction (ORR) requires high loading of expensive platinum (Pt)-based catalysts to maintain acceptable power densities. While alternative Pt-transition metal alloys are being investigated to improve catalytic activity and lower costs, such alloys exhibit insufficient stability under acidic conditions [2]. As recently highlighted in C&E News, the processes that govern individual component (i.e., catalyst layer, Nafion membranes and gas diffusion layers) performance and degradation within an operating fuel cell remain poorly understood [3]. At present, analytical tools for the in-situ investigation of these complex electrochemical and transport phenomena do not exist.

To address this need, we have developed a microfluidic fuel cell with a flowing aqueous electrolyte instead of a stationary PEM. The constantly refreshing electrolyte stream eliminates water management issues, facilitates by-product removal (i.e., carbonates) and enables electrolyte flexibility (i.e., no pH restrictions). By placing an external reference electrode at the electrolyte stream outlet, in-situ electrochemical analyses (i.e., CA, CV, EIS) of individual electrode characteristics can be conducted to identify performance-limiting factors. This microfluidic fuel cell enables the experimental versatility of a three-electrode electrochemical cell within an operating fuel cell without disassembly. Both the performance of individual components as well as the effects of operating conditions can be evaluated. We have demonstrated the utility of such an analytical tool by investigating the performance and durability of several novel electrodes and catalysts under acidic and alkaline conditions [4-6]. Here, we will present our ongoing work further investigating electrode degradation processes and optimizing membrane-electrode assemblies (MEAs) for use in conventional PEM-based fuel cells.

References

[1] L. Carrette, K. A. Friedrich and U. Stimming, ChemPhysChem, 1, 2000, 162.

[2] H.A. Gasteiger, S.S. Kocha, B. Sompalli, F.T. Wagner, Appl. Cat., B, 56, 2005, 9.

[3] M. Jacoby, Chem. Eng. News, 87(13) 2009, 39.

[4] R.S. Jayashree, M. Mitchell, D. Natarjan, P.J.A. Kenis, Langmuir, 23, 2007, 6871.

[5] F.R. Brushett, W.P. Zhou, R.S. Jayashree, P.J.A. Kenis, J. Electrochem Soc., 156, 2009, B565.

[6] F.R. Brushett, H.T. Duong, J.W.D. Ng, A. Wieckowski, P.J.A. Kenis, in preparation.