Influence of Feed Vapour Fraction on the Performance of Direct Methanol Fuel Cell
Direct methanol fuel cells are known to suffer from methanol crossover, sluggish electrode kinetics and flooding in the channels which results in a decrease in the efficiency of the fuel cell. In this investigation experiments were conducted to establish
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1 Introduction Direct methanol fuel cells (DMFC) are promising power sources for portable power devices and transportation. It has received much attention because of its simplicity, higher energy density, quick refueling and easy transportation of fuel. The commercialization of DMFC is still an uphill task because of the problems associated with methanol crossover, slow reaction kinetics, cathode flooding and heat management. In DMFC, methanol solution is fed to the anode where methanol and water molecules react to form electrons and protons by the electrochemical reaction (Xianglin et al. 2008) CH3 OH þ H2 O ! 6H þ þ 6e þ CO2 The generated protons reach to the cathode through the electrolyte and the electrons through the external circuit. In cathode, air combines with protons and electrons to form water. 3 O2 þ 6H þ þ 6e ! 3H2 O 2 The overall reaction CH3 OH þ
3 O2 ! 2H2 O þ CO2 2
V. Ravi S. Joseph (&) National Institute of Technology Calicut, Kozhikode, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2017 R. Mohan B. et al. (eds.), Materials, Energy and Environment Engineering, DOI 10.1007/978-981-10-2675-1_23
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Generally liquid methanol with a lower concentration of methanol is fed on the anode side (active or passive) which reduces the methanol crossover, but it decreases the throughput power from the cell. The present study deals with the feasibility of methanol in lower concentration as well as in the pure form in the vapour phase as well as in a different fraction of vapour to the liquid ratio as fuel on the anode side. The study conducted by Shukla et al. (1995) used a quartz vaporizer for producing methanol vapour from 1 M solution. They reported that the performance of the DMFC using vapour feed is better than that of liquid feed. Scott et al. (1999) conducted flow visualisation studies on carbon dioxide evolution in liquid as well as vapour feed and also compared the performance. They observed a current density of 1.7 W/cm2 for vapour feed compared to 0.12 W/cm2 of liquid feed under the same operating conditions. Transient studies were conducted by Kallo et al. (2004a, b) in a vapour feed fuel cell. Sumio et al. (2011) conducted studies on methanol crossover in vapour feed and concluded that lower concentration of methanol solution gives a better result compared to higher concentration. They also compared the methanol crossover with liquid feed and CO2 production on the cathode side is found to be half with vapour feed under same operating conditions. Nakagawa et al. (2012) used a PCP for generation of methanol vapour to feed DMFC and studied the effects of different variables like methanol concentration, temperature, methanol flow rate, air flow rate and humidity. Faghri and co-workers (2007, 2010, 2011, 2012) did extensive work on passive DMFC modelling and fuel delivery system. Their work focused on neat methanol in the vapor phase as feed using membranes. The developed steady state and transient model and found that the response time varies f
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