On-chip fuel cells are promising power sources for future electronics and microdevice applications including on-chip sensors and micro-air-vehicles. Previously, we reported a small scale (0.4 mm wide and 6 mm long) on-chip fuel cell of an air-breathing, membrane-less and monolithic design, which exhibited the highest power for an on-chip fuel cell, 1.4 μW (J. Am. Chem. Soc., 2008, 130, 10456). In order to improve the performance, precise understanding of the phenomena occurring in the cells is of primary importance. Thus, this paper focuses on understanding cell operation by using numerical simulation, and on implementing cell improvements based on the simulation results. The initial quantitative study concluded that the performance of the on-chip fuel cell was limited owing to oxygen-supply caused by cathode flooding. Thus, we experimentally added the hydrophobic ionomer (Nafion) onto the cell to reduce the influence of the flooding, and successfully increased the maximum power from 2.0 to 2.8 μW. This power is considered sufficient for microsensor application. On the basis of additional simulation results, we show that performance may potentially be improved to over 100 μW by increasing the effective surface areas of catalysts to a level comparable with methanol fuel cells. If successful, such performance enhancements would position the on-chip fuel cell as a viable candidate for future micro-devices, and point to promising directions for fuel cell development efforts.
