Enhancing proton conduction in metal organic frameworks by post synthetic modification

Abstract

The human need for energy is increasing in response to the increasing population rapid urbanization and industrialization especially in the developing countries U S Energy Information Administration 8217 s EIA recently released International Energy Outlook 2013 IEO2013 projects claim that the global energy consumption will increase by 56 between 2010 and 2040 In response to this demand various energy alternatives to fossil fuels are being looked at out of which fuel cells have proven to be a promising candidate due to their high conversion efficiency low pollution and high fuel flexibility They are electrochemical conversion devices that produce electrical energy from the chemical energy of a fuel and oxygen at high thermodynamic efficiencies They mainly have three components the cathode the anode and the electrolyte At one of the electrodes hydrogen is oxidized to protons The electrolyte is necessary to transfer these protons to the other electrode where they combine with the oxygen to form water At present Nafion is the commercially used electrolyte membrane which has a conductivity of 10 2 to 10 1 S cm in the presence of humidity but it fails to conduct ions at a higher temperature under anhydrous conditions Regardless the Nafion is still the commercially used proton conducting electrolyte because of its robust structure excellent thermal and mechanical stability high proton conductivity and reusability without any significant loss of activity Various materials are being studied to be used as electrolytes in the fuel cells Developing Metal Organic Framework MOF based proton conducting electrolytes for fuel cell applications is an important target that has drawn a lot of attention They are coordination framework compounds formed by linking metal ions clusters via organic linkers and have emerged as a new class of functional materials The modular and crystalline nature of the MOF permits controlled introduction of functional species and characterization of their composition with high precision a task