Porous Silicon Membrane Based Formic Acid Fuel Cells for Micro Power Generation

Micro fuel cells based on porous silicon membranes are developed and characterized in this work and are demonstrated to be a promising candidate for powering portable electronic instruments. First, different pore morphologies of porous silicon are explored. The pore morphologies are characterized using scanning electron microscopy. The pore sizes can be controlled to range from microns to nanometers. Proton conductivities of porous silicon membranes are derived using impedance spectroscopy. It is shown that pore morphology determines the transport property of the porous silicon membrane through the volume fraction of the proton conducting phase in the membrane. A percolation model is shown to well explain the transport phenomena in porous silicon membranes. Finally, micro fuel cells are fabricated using porous silicon membranes with different thickness and different pore morphologies, and their performances are tested. Fuel solutions with different formic acid concentrations are also tested. With formic acid solution as the fuel, the micro fuel cells based on either p-type or n-type porous silicon membrane produce promising peak power density.