Figure 1                                                                                                             Figure 2

           The Abruña group has been focusing on the active pursuit of anode catalysts for fuel oxidation, as well as the investigation of possible catalysts to enhance the cathodic reduction of oxygen.  While we have been looking at the individual components of a fuel cell in great detail, we have also tried our hand at developing an actual fuel cell.  We have now developed a micro fuel cell which includes both of the components above, but is unique in a number of ways when compared to a macro scale room temperature fuel cell.   One of the main differences is that typical fuel cells employ polyelectrolyte membranes (PEMs) that prevent the fuel from mixing with the oxidant.  While that seems like an easy enough task, it is difficult to actually carry out because the PEM must be selectively permeable to protons.  That makes a PEM very costly to develop.  It also turns out that the PEMs used today are not very robust and are not completely selective.  Our idea was to completely eliminate the costly PEM in our micro fuel cell. 

                                            Figure 3                                                                                                        Figure 4

            It has been shown that laminar flow can be employed, in place of a polyelectrolyte membrane (PEM), in order to develop a membraneless microchannel fuel cell.  In a microchannel, two solutions can be flowed side by side and they will not mix.  They don’t even have to be pump very fast for this to occur due to the dimensions of the microchannel!  We can then pump fuel and oxidant together and fuel crossover will not occur to an appreciable extent at the temperatures, flow rates, and time scales involved.  Laminar flow also allows proton conduction at the interface of the two solutions, thus eliminating the need of the PEM completely.  By eliminating the PEM, a common component in macro-fuel cells, development costs can be reduced, and the complexity of the micro-fuel cell design can be decreased.   We have developed a planar membraneless microchannel fuel cell design which includes a silicon microchannel with a “tapered flow boundary” in order to ensure the establishment of laminar flow of the fuel and oxidant streams prior to their coming into contact.  This design takes advantages of a large electrode area and allows for the testing of a variety of microchannels and fuel systems. The power produced from the H₂/O₂ single microchannel fuel cell, using Pt as the catalyst, was on the order of 0.60 mW/cm².  Using this design, we will be able to integrate the catalyst materials above in order to increase the power generated from this device.  Figure 1 shows a side-view of the planar microchannel fuel cell.  Figure 2 is a power curve for a 5-microchannel array, using hydrogen as a fuel, fabricated in order to increase the power output of this device.  This system can be a considered a versatile platform for testing a number of electrodes, fuels, and microchannel dimensions.  We will continue design optimization and power output enhancement.  We will also continue to investigate the use of new fuel systems that could not be considered with PEM fuel cells.  Figure 3 shows the actual individual components of the versatile device platform, as well as the fully assembled micro fuel cell integrated with a fuel pumping system and data collection instrumentation.

                This research has been spear-headed by the formation of the Cornell Fuel Cell Institute taking a radical departure from conventional thinking and approaches to develop new materials that could improve the efficiency of the main components of a low temperature (< 150°C) fuel cell and on reformer catalysts for low temperature operation.