Improved fuel use efficiency in microchannel direct methanol fuel cells using a hydrophilic macroporous layer

We demonstrate state-of-the-art room temperature operation of silicon microchannel-based micro-direct methanol fuel cells (μDMFC) having a very high fuel use efficiency of 75.4% operating at an output power density of 9.25 mW cm−2 for an input fuel (3 M aqueous methanol solution) flow rate as low as 0.55 μL min−1. In addition, an output power density of 12.7 mW cm−2 has been observed for a fuel flow rate of 2.76 μL min−1. These results were obtained via the insertion of novel hydrophilic macroporous layer between the standard hydrophobic carbon gas diffusion layer (GDL) and the anode catalyst layer of a μDMFC; the hydrophilic macroporous layer acts to improve mass transport, as a wicking layer for the fuel, enhancing fuel supply to the anode at low flow rates. The results were obtained with the fuel being supplied to the anode catalyst layer via a network of microscopic microchannels etched in a silicon wafer.