Fuel cells, being environmental friendly and renewable source of energy, are generating world wide interest. This type of fuel cells can also function on natural gas, hydrocarbon and other fuels. Fuel to electricity conversion efficiency in SOFC is around 50 - 60% and by utilization of system’s waste heat, efficiency can be further raised up to 80 - 85%. Solid Oxide Fuel Cell (SOFC) appears to be the most promising technology for small electric power plants over 1 kW. Due to high oxygen ion conductivity at high temperature (> 800 0C), stabilized zirconia (in cubic phase) is an excellent electrolyte for solid oxide fuel cell and also for oxygen gas sensors. Ionic conductivity in a solid oxide fuel is determined by its grain size, composition, dopants, processing etc. Ionic conductivity cannot be increased beyond a certain value by adding charge carrier concentration, as increase in ionic charge carrier concentration above the optimal value decreases its ionic conductivity due to association of ionic defects. Recently it has been shown that the ionic conductivity of Yettria-stabilized Zirconia (YSZ) electrolyte increases with reduction in particulate size below < 100 nm. Use of nano-grained stabilized zirconia as an electrolyte for SOFC, therefore, provides a means to develop highly efficient Fuel cell. Although there are various methods to produce nanoparticles of zirconia e.g. laser evaporation, sol-gel, hydrolysis, pyrolysis etc., laser method is preferred due to controlled reaction volume, steep temperature gradient and non-contact clean process. The process yields controlled and narrow size distribution of nano particles. Currently CO2 lasers have been used economically to produce ZrO2 nanoparticles.
The main objective of current research program is to increase ionic conductivity of ZrO2-based SOFC at low temperature (< 800 oC) through reduction in associated particle size in the nanometer range. Operation of SOFC at low temperature would have the benefit of reduced thermal stress in the electrolyte and using cheaper structural component which would serve to reduce the cost and increase the life of fuel cell.
