The Mathematical modelling of electrode performance in fuel cells

ABSTRACT Specially prepared Ni- porous electrode used in this study has been investigated for its unsteady-state behaviour at the temperature ranges from 20°C to 55°C, and KOH electrolyte concentrations from 25 % to 30% with different hydrogen-gas flow rates. Ni-flat plate electrode has been used as counter electrode in the fuel cell. It has been observed that the higher the temperature, the faster electrode reaches the steady- state voltage. Fresh Ni/PTFE electrode surface is normally oxidized in air; therefore, the surface is covered with NiO. Reduction of this oxide to elemental Ni is accomplish in situ electrocatalytically. The more Ni at surface, the more voltage generated. Voltage readings were taken between anode and referance electrode at certain time intervals to follow the fractional surface coverage of Ni (0 ). According to the an autocatalytic reaction rate law the reaction expression was d9/dt=k0(l-8)C*H2, where (1- 0) is the fraction of NiO on the surface and C*H2 is the solubility of hydrogen in the electrolyte. Upon integration of the above equation one gets In [0 /(l-0)]=at + b. Since voltage generated is proportional to 0, this last equation becomes In [V/ (m-V)]= at + b where constants m, a and b are determined by using the MATHCAD package program. Experimental data fit the proposed model equation reasonably well. The activation energy for the reduction was also determined. Key Words: Fuel cell, electrode potantial, mathematical modelling, Ni/PTFE porous gas difusion electrode