A study on electric conductivity of phosphoric acid supported on nano-pore rice husk silica in H2|Pt|H3PO4/RHS|Pt|O2 fuel cells

PEMFC (Polymer Electrolyte Membrane Fuel Cell) is widely considered as an energy conversion system from the chemical energy of hydrogen to electric energy. But, hydrogen fuel obtained from hydrocarbons has trace amount of carbon monoxide which is a potential poison for platinum electrode at the cell operating temperature similar to 100 degrees C and it becomes a huddle for the general usage of PEMFC. On the other hand PAFC (Phosphoric Acid Fuel Cell) operates at a higher temperature and the platinum electrode oxidizes carbon monoxide poison while there is a leakage problem of the liquid phase. To combine the advantages of two fuel cells, the electrolyte systems of phosphoric acid supported silica on ceramics are recently being tested. In this study, we investigated the nm pore rice husk silica as a support for phosphoric acid and tested the electric conductivity of the silica plate and the characteristics of a prototype fuel cell H-2 vertical bar Pt vertical bar H3PO4/RHS vertical bar Pt vertical bar O-2 at 100-200 degrees C. The conductivity of H3PO4/RHS was 8 mS cm(-1) above 175 degrees C under 200 torr H2O. In the fuel cell, the apparent conductance of the electrolyte from I-V characteristics was 2.45 mS/cm at 160 degrees C under 1 atm H-2 and air at present.