A miniature direct formic acid fuel cell battery

This work describes miniature formic acid fuel cell batteries, which are built based on a Nafion® membrane and thin metal foils. The intrinsic advantages of formic acid fuel allow for a very simple design of the fuel cell, and the volume of the complete system, including fuel reservoir, can be as small as 11 mm3. This work examines the effect of membrane thicknesses and fuel concentrations on the cell performance. The optimized cell performance is obtained with N117 membrane and 12 M fuel. Peak power density of the optimized cell is 112 mW cm−2. Life tests are conducted at various conditions using 6 μL of fuel. An energy density of 70 Wh L−1 with 40% fuel utilization rate is observed when 12 M formic acid is used at 0.5 V.