1 Proceedings of FuelCell2006 Fourth International ASME Conference on Fuel Cell Science, Engineering and Technology Irvine, California. June FUELCELL ELECTRICAL CHARACTERIZATION OF A GLUCOSE-FUELED ALKALINE FUEL CELL 1 Eugenia Bubis, 1 Lea Mor, 1 Nissim Sabag, 1 Zeev Rubin, 1 Ury Vaysban, 2 Kas Hemmes, 1 Pinchas Schechner 1 Ort Braude College of Engineering, Karmiel, Israel. 2 Delft University of Technology, Delft, The Netherlands.

2 Experimental Determination of: 1)Quasi-static polarization curves, V(J); 2) Power Density as a function of current density, PD(J) 3) Ohmic internal resistance of the cell, R FC. Experimental Conditions 0.35 M[KOH] to 1.11 M.[Glucose]2 Room Temperature3 0.1 sSampling Time4

3 Procedure FIGURE 2: FUEL CELL VOLTAGE AS A FUNCTION OF TIME DURING THREE CONSECUTIVE CONNECTION-DISCONNECTION CYCLES, [glu] 0 = 0.67M; R L =10.29 , 9.28  8.4 

4 FIGURE 3: FUEL CELL VOLTAGE AS FUNCTION OF TIME DURING A CONNECTION-DISCONNECTION CYCLE. R L =  ; [glu] 0 = 0.67M = c + 0.1s) = d + 0.1s)

5 Polarization Curve for different [glu] 0 Small Values

6 Power Density as Function of Current Density of Various [glu] 0 Low Values Maximun at 0.22 M Competence with non-electrochemical reactions

7 Internal Resistance 1 - Voltage Divider Method Current at V IRC Assuming that only the ohmic resistance can react immediately

8 The current at the disconnection instant is: At the disconnection instant, there is a sudden increase in the cell’s voltage,  V D, caused by the immediate annulment of the ohmic losses 2 – Current Interrupt Method

9 R FC as function of R L computed from the "VOLTAGE DIVIDER“ method [glu] 0 = 0.22 and 0.67 M. Horizontal continuous line indicates the R FCmean

10 Internal Resistance as function of the glucose concentration R FC, 0.35 M KOH = [glu] 0 [  ] R FCmean = R K + R C [glu] 0 [  ] Glucose Concentration dependent term Glucose Concentration independent constant

11 Internal Resistance dependence on Glucose concentration, R C : R FCmean = R K + R C [glu] 0 [  ] [·M-1][·M-1]  ·M -1 ·m R c (1M glucose in 0.35 M KOH) = 2.56  ·m The glucose concentration contributes to the ohmic resistance only in the volume between the two electrodes. As any ohmic resistor:

12 Internal resistance factor independent of the glucose concentration, R K. R FCmean = R K + R C [glu] 0 [  ] R K includes ohmic resistances that don’t depend on glucose concentration, R k = R metallic mesh + R connections + R 0.35M KOH R K = 2.02  > R 0.35M KOH R 0.35M KOH = 0.21  < 2.02  = R K R K Contributes to the ohmic resistance only in the volume between the two electrodes. As any ohmic resistor

13 Conclusions At a [KOH] = 0.35M, the cell reaches peak performance at [glu] 0 = 0.22M The two methods used to measure the internal resistance of the fuel cell, Voltage Divider and Current Interrupt, yield practically identical results Efforts will be directed towards development of practical glucose-fueled AFC, as electricity generators for portable devices Proposed Directions: The effect of temperature on cell performance. Development of nano-tube electro-catalytic electrodes