Effects of nano/microstructures on performance of Si-based microfuel cells

We investigated the effects of the contact surface structure of porous Si-based membrane electrode assemblies (MEAs) on the performance of microfuel cells, because the contact area of the triple-phase boundary among the MEA components plays an important role in the performance of polymer electrolyte fuel cells (PEFCs). An n-type silicon substrate was first wet-etched with KOH and subsequently anodically etched to fabricate a porous Si substrate. The cross section of the mechanically polished Si wafer showed pores with high aspect ratios. Electrolyte solutions were filled into the pores to prepare a porous Si membrane (PSM), and the MEA was fabricated by hot-pressing the PSM between two conventional catalyst-coated carbon-paper electrodes. The porous Si-based MEA worked well and showed a power density higher than that of the Nafion®-212-based membrane. Further, we examined the effects of the nano/microstructures at the triple-phase boundary and found that the more densely arranged nano/microstructures reduced the magnitudes of the activation overvoltage and ohmic overvoltage, thereby improving the cell performance.