Performance enhancement of phosphoric acid fuel cell by using phosphosilicate gel based electrolyte

Replacement of phosphoric acid electrolyte by phosphosilicate gel based electrolytes is proposed to enhance the performance of phosphoric acid fuel cell (PAFC). Phosphosilicate gels in paste form and in powder form are synthesized from tetraethoxysilane and orthophosphoric acid by using sol-gel method, for two different P/Si ratios of 5 and 1.5, respectively. Replacement of phosphoric acid electrolyte by phosphosilicate gel paste enhances the peak power generation of the fuel cell by 133% at a cell temperature of 120°C, increases the voltage generation in the ohmic regime and extends the maximum possible load current. Polyvinyl alcohol (PVA) is used to bind the phosphosilicate gel powder and to form the hybrid crosslinked gel-polymer electrolyte membrane. Soaking the membrane with phosphoric acid solution instead of with water improves the proton conductivity of the membrane, enhances the fuel cell voltage and power generation and extends the maximum possible operating temperature. At a low temperature of 70°C, peak power produced by phosphosilicate gel polymer electrolyte membrane fuel cell (PGMFC) is increased by 40% compared to that generated by phosphoric acid fuel cell (PAFC). However, the performance of composite membrane diminishes as the cell temperature increases. Thus the phosphosilicate gel in paste form is found to be a good alternative of phosphoric acid electrolyte at medium operating temperatures, while the phosphosilicate gel PVA composite performs better at low operating temperatures.