DEVELOPMENT OF POLYMER ELECTROLYTE MEMBRANES FOR FUEL CELL APPLICATIONS

Abstract

The demand for sustainable energy across the world is gradually increasing, which is driven by the increasing global population, limited supply of fossil fuels, the emission of greenhouse gases, the onset of global warming and climate changes, and the standard of living. Fuel cell technology has emerged as the most promising power source for producing clean energy, where chemical energy stored in liquid/gas/solid fuels gets directly converted to electrical energy without being combusted. A typical fuel cell comprises an electrolyte (e.g., polymeric membrane, solid oxide layer, acid solution, buffer solution, alkali solution, etc.), one anode, and a cathode. The anode and cathode layers are made up of catalyst and support materials forming the main support structure of the fuel cell, which contribute to the improvement of fuel cell performance. In the case of the hydrogen fuel cell, ionization of the hydrogen atom (fuel oxidation) occurs at the anode, releasing the electron and proton; the electron travels through an external circuit and combines with the oxygen available at the cathode, while the proton travels through the electrolyte to combine with oxygen forming water and electricity. Depending on the nature of the electrolyte used, fuel cells are classified as (i) proton exchange membrane fuel cells, (ii) solid oxide fuel cells, (iii) molten carbonate fuel cells, (iv) phosphoric acid fuel cells, (v) alkaline fuel cells, etc. Based on the nature of the fuel used, fuel cells can be further classified as (i) hydrogen fuel cells, (ii) natural gas fuel cells, (iii) methanol fuel cells, (iv) ethanol fuel cells (v) biofuel cells (vi) hydrocarbon fuel cells, (vii) ammonia fuel cells. Hydrogen is the most common and well-known fuel, hydrogen fuel cell is the most popular. The electrolyte layer in a fuel cell is usually sandwiched between two electrodes in which other essential components, i.e. the bipolar plate, catalyst, and gas diffusion layer are separately adhered. In the case of a proton exchange membrane fuel cell (PEMFC) transport of proton (through anodic oxidation of hydrogen) occurs through the electrolyte (polymer membrane), to react with oxide anions formed at a cathode (reduction of oxygen by ‘e’ released during oxidation of H atom).