A versatile electrochemical fuel sensor for direct membrane fuel cell applications

A simple fuel cell-type electrochemical sensor for measuring the concentration of a specific fuel, e.g., methanol, ethanol, formic acid, sodium borohydride, etc., prepared in an aqueous solution has been developed. The heart of the fuel sensor is mainly composed of a membrane electrode assembly (MEA), which is uniquely designed to have the anode size much smaller than that of the cathode and utilize the ambient air as the oxidant. The innovation of this approach is to ensure that the fuel diffuses to the anode/membrane interface can be completely reacted so as to eliminate the interferences of the fuel crossover and enhance the output signals. Thus, the measured sensor current reflects the true concentration of the diffusion-limited fuel at the membrane/electrode interface, which is proportional to the fuel concentration in the bulk. It can be readily operated in a passive mode as well as in an active mode with the aqueous fuel solution under a stagnant or a flowing condition. The developed electrochemical fuel sensor can be applied to a variety of direct membrane fuel cell systems including direct methanol fuel cell system.