The existing fuel cell alcohol sensors [1-3] suffer severely with humidity interference and signal instability. This interference and instability renders the existing sensors useless for transdermal ethanol detection in non-ideal environment. To address these issues of the fuel cell alcohol sensor, various electrode designs along with the catalysts were explored in this work. The design includes both two and three electrode setups with the Nafion as proton exchange membrane, where the three electrode setup provided stable signal compared to two electrode setup. Considering the development of a potential transdermal ethanol sensor, the ethanol exposed area of the working electrode was optimized to 1cm²and reference and counter electrode were placed on the other side of the Nafion membrane. For the ethanol measurements in the three electrode system, a fixed potential was applied between working and reference electrode and the change in current due to ethanol concentration was measured between working and counter electrode. To eliminate the interference due to humidity the applied potential for measurement was same as that of the open circuit potential (OCP) of the fuel cell in presence of humidity. Catalysts such as Ni, Cu, Fe and Au were studied, where Ni has better catalytic activity for ethanol oxidation and oxygen reduction [4] providing almost 600, 300 and 3 times greater current response than  Au, Fe and Cu respectively (Figure 1). The sensitivity for the sensor was found 0.062 nA/ppm in vapor phase for this Ni catalyst.

Figure 1: Amperometric responses of fuel cell sensor for ethanol (a) Fe, (b) Au, (c) Ni and (d) Cu catalysts.

Acknowledgements:

This work is funded by the ASSIST NSF ERC and NSF I-Corps Teams.

References:

1. Jeng, K.-T.; Huang, W. M.; Chien, C. C.  and Hsu, N.-Y. 2007. A versatile electrochemical fuel sensor for direct membrane fuel cell applications. Sens Act B: Chem 125:278-283.

2. Jiang, L.; Zhou, Z.; Wang, S.; Liu, J.; Zhao, X.; Sun, G.; Xin, Q. and Zhou, B. 2004. Development of air-breathing direct ethanol fuel cells with PtSn as anode. Prepr Pap-Am Chem Soc, Div Fuel Chem, 49:668-670.

3. Robertson, R.; Vanlaar W. and Simpson, H. 2007. Continuous transdermal alcohol monitoring: A primer for criminal justice professionals. The Traff Inj Resc,ISBN: 978-0-920071-60-1.

4.  Barbosa, A. F. B.; Oliveira, V. L.; Drunen V. and Tremiliosi-Filho, G. 2015. Ethanol electro-oxidation reaction using a polycrystalline nickel electrode in alkaline media: Temperature influence and reaction mechanism. J. of Electroanal Soc, 746: 31-38.