Energy Sciences

Title :

Area of research :

Focus area :

Principal Investigator :

Timeline Start Year :

Timeline End Year :

Contact info :

Executive Summary :

Objective: Development of alternative Nafion hybrid membranes with high electrochemical selectivity (restricted methanol cross over, improved proton conductivity) for the DMFC; Perfect engineering, development and demonstration of 250 W direct methanol fuel cell stack.

Summary: of methanol from anode to cathode through the polymer electrolyre and reduces the overall cell performance. Methanol crossoveris caused by the concentration gradient, depends on operational current and molecular transport through electro-osmotic drag. Methanol crossover during DMFC operation causes (1) electrode de-polarization, (2) mixed potential, resulting in the open-circuit voltage (OCV) of the DMFC below 0.8 V (3) consumption of O2 (4) cathode catalyst poisoning by CO (an intermediate of methanol oxidation), and (5) water accumulation on the cathode catalysts sites. Morever, the overall fuel utilization efficiency is lowered when there is excessive methonal crossover. The current state of art polymer elctrolyte membrane for DMFCs os Nafion which has shown promising results due its remarkable mechanical and chemical stability and high proton conductivity. These are attributed to the presence of a strog hydrophobic fluorinated backbone and the presence of a strong hydrophobic sulfonic acid groups. The amphiphilic features between hydrophobic and hydrophilic phases enable the sulfonic acids group to form ionic ckusters are much larger than the diameter of a methanol molecule (0.38 nm). Hence there is severe methanol crossover when used as polymer electrolyte membrane (PEM) in DMFC. In order to overcome the same, hybrids of Nafion are explored by incorporating inorganic additives like silica, zirconia and zeolites are few important potential additives to Nafion in making gybrid membranes which reduce the methanol crossover drastically (upto 40%). The above hybrid membranes when used in DMFC, delivers superior power and may be explored for their potential scale up in developng a suitable power pack of desired applications. CECRI Madras Unit, has developed and demonstrated self-supported direct methanol fuel cell (DMFC) of 45W with pristine Nafion membrane and gained confidence to develop DMFC stack of higher power output. Series of Nafion membranes with inorganis fillers such as SiO2, zeolites, carbon nanotubes (CNTs), graphene, porous carbon are explored as potential candidates for DMFCs. The membrane electrode assemblies (MEAs) fabricated from these membranes are assembled in a single cell DMFC and the superior performance were evaluated. The active area of DMFCs are limited to 25 cm2 for performance analysis . The synthesis of materials, half cell electrochemical studies, fabricating membrane electrode asemblies and fuel cell/ stack assembly and testing are the major strength of CECRI madras unit. In this project, we porpose in developing Nafion-hybrid membranes that is competitive to Nafion 117, both in reducing methanol crossover and other physical properties. Scale of up this membranes to higher size (= 100cm2 )and development of 250W DMFC system with the optimized hybrid membrane is the main focuses on this proposal.

Implementing Agency :

Funding Agency :

Source (more info) :