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Research Papers

# Analysis of Drying and Dilution in Phosphoric Acid Fuel Cell (PAFC) Using Galvanometric Study and Electrochemical Impedance Spectroscopy

[+] Author and Article Information
Tanmoy Paul

Department of Physics,
Indian Association for the Cultivation of Science,
2A & 2B Raja S.C. Mullick Road,
e-mail: paultanmoy00@gmail.com

Mrinal Seal

Department of Physics,
Bengal Engineering & Science University,
Shibpur, West Bengal 711103, India
e-mail: mrinal.phy@gmail.com

Dipali Banerjee

Professor
Department of Physics,
Bengal Engineering & Science University,
Shibpur, West Bengal 711103, India
e-mail: dipalibanerjeebesu@gmail.com

Saibal Ganguly

Professor
Chemical Engineering Department,
Universiti Technologi Petronas (UTP),
Bandar Seri Iskandar, Perak Darul Ridzuan,
Tronoh 31750, Malayasia
e-mail: gangulysaibal2011@gmail.com

Kajari Kargupta

Professor
Chemical Engineering Department,
Kolkata 700032, India
e-mail: karguptakajari2011@gmail.com

Pavitra Sandilya

Assistant Professor
Cryogenic Engineering Department,
I.I.T. Kharagpur,
West Bengal 721302, India
e-mail: profsandilya@gmail.com

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF FUEL CELL SCIENCE AND TECHNOLOGY. Manuscript received January 14, 2013; final manuscript received January 29, 2014; published online February 27, 2014. Assoc. Editor: Abel Hernandez-Guerrero.

J. Fuel Cell Sci. Technol 11(4), 041001 (Feb 27, 2014) (7 pages) Paper No: FC-13-1004; doi: 10.1115/1.4026622 History: Received January 14, 2013; Revised January 29, 2014

## Abstract

Different experimental and analytical techniques namely steady state galvanometric study and electrochemical impedance spectroscopy (EIS) are employed to generate rule sets for identification of the acid drying and dilution phenomena in a phosphoric acid fuel cell (PAFC). The slope of steady state current versus voltage is used as a performance marker. A new parameter Δ, which signifies the net moisture transport in PAFC, is introduced and evaluated from the experimental data to locate the regimes of electrolyte dilution and drying. Based on these two parameters, the performance of a PAFC is mapped on the plane of operating variables. Performance decay at higher cell temperature and lower humidifier temperature (below 60 °C) signifies acid drying; on the contrary the same at lower cell temperature and higher humidifier temperature is attributed to acid dilution. EIS is employed by imposing a sinusoidal potential excitation on steady state DC load and the shift of maximum phase angle position in the frequency spectrum is used as a diagnostic marker. Results show absence of peak in the domain of positive frequency for acid drying condition, while acid dilution causes the peak to be shifted at higher frequency value. Electrochemical timescales estimated from EIS increases by many order of magnitudes compared to that in a normal PAFC, when electrolyte drying occurs. The results obtained from EIS analysis are in agreement with the performance mapping based on galvanometric steady analysis. The results are significant in context of water management and humidity control in a PAFC. The tools and parameters introduced in the present publication show promising potential to map the performance and SOH of a PAFC on the plane of various operating variables. Results and logics revealed are of significance in development of inferential model for the online optimization of PAFC.

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## Figures

Fig. 1

Experimental setup for characterization of PAFC unit cell

Fig. 2

Schematic diagram of the constituent components of the PAFC unit cell

Fig. 3

Schematic diagram of reactant and product transport mechanism in a fuel cell unit

Fig. 4

Voltage responses for different currents at fixed cell temperature of 150 °C

Fig. 5

Voltage responses for different operating currents at fixed humidifier temperature of 70 °C

Fig. 6

Performance mapping of a single cell for different cell temperatures and humidifier temperatures with the variation of Δ

Fig. 7

Nyquist diagrams for the operation of single cell

Fig. 8

Bode diagrams for the operation of single cell: (a) dilution has peak around positive logarithm of frequency whereas (b) drying has peak around negative logarithm of frequency

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