PdxRu1-X, electro-catalyst in direct alkaline ethanol fuel cells Alixia Farrell; Evans Monyoncho[1]; Elena A. Baranova[1]

[1] Department of Chemical and Biological Engineering, Center for Catalysis Research and Innovation (CCRI) University of Ottawa, Ottawa, ON K1N 6N5, Canada

Direct  Ethanol  fuel  cells  (DEFCs)  are  promising  candidates.  They  have  a  higher  energy  density,  their  materials  are  more  available  and  their  handling  is  easier  than  the  hydrogen  based  fuel  cells.  This  technology  is  not  yet  perfected  due  to  the  inef?icient  electro-­‐oxidation  of  the  ethanol.  The  factors  addressed  by  this  research  is  the  choice  of  electro-­‐catalyst  and  the  concentration  of  ethanol  provided  to  the  reaction.  The  development  of  a  catalyst  that  can  fully  decompose  ethanol  into  water  and  CO2  to  release  the  maximum  of  energy  will  permit  the  ethanol-­‐based  fuel  cell  to  be  a  viable  and  ef?icient  source  of  energy  in  the  future.  

Abstract

Objective Increase  the  current  density  produced  by  the  reaction  while  reducing  the  onset  potential  by  testing  certain  ratios  of  Pd  and  Ru  as  electro-­‐catalyst  and  various  concentrations  of  ethanol  to  be  oxidized.  

Methodology

Results

Catalyst  Mass  of  Pd  on  electrode  

(mg)  ESCA  (cm2)  

Anodic  E  (V)   Anodic  I  (mA  cm-­‐2)  

E  Onset   Ep1   Ep2   Ip   I  at  -­‐0.96  V  Pd/C   0.00461   0.153714   -­‐0.97   -­‐0.659   -­‐-­‐-­‐-­‐-­‐   2.279   0.018834  PdRu/C  50-­‐50   0.00237   0.648762   -­‐1.28   -­‐0.676   -­‐0.897   0.201   0.12142  PdRu/C  80-­‐20   0.00394   0.581447   -­‐1.23   -­‐0.793   -­‐1.066   0.626   0.228561  PdRu/C  90-­‐10   0.00498   0.916623   -­‐1.19   -­‐0.623   -­‐-­‐-­‐-­‐-­‐   1.263   0.21276  PdRu/C  95-­‐5   0.00440   0.19611   -­‐1.21   -­‐0.635   -­‐-­‐-­‐-­‐-­‐   0.568   0.022922  PdRu/C  99-­‐1   0.00455   0.539421   -­‐1.19   -­‐0.65   -­‐-­‐-­‐-­‐-­‐   3.028   0.154533  

Fig.  1:  Method  of  synthesis  

Discussion

Future Work

Acknowledgments

References

•  Electrochemical  Surface  Area  (ECSA)  varies  on  the  preparation  and  application  of  the  catalyst  

•  Electrochemical  activity  is  optimal  at  a  set  potential  of  -­‐0.96  V.  Any  lower  potential    (-­‐1.06  V)  reduces  the  activity  to  almost  no  current  in  the  long  term.  

•  Presence  of  Ru  as  catalyst  enhancer  increases  current  intensity  overall.  Higher  ratios  of  Ru  decrease  onset  potential.  

•  Current  intensity  is  optimized  at  a  PdRu  atomic  ratio  of  90:10  but  PdRu  50:50  has  the  lowest  onset  potential.  

•  Ethanol  concentration  increases  electrochemical  activity  up  to  a  peak  of  1  M  EtOH.  Any  higher  concentration  of  EtOH  decreases  current  intensity.  

Conclusion

0 1000 2000 3000 4000 5000 6000

0.00

0.05

0.10

0.15

0.20

 

 C A s  for  P dxR u

1-­‐x/C  s amples  in  1M  K O H+1M  E tO H  

I/mA  cm

-­‐2

time/s

 P d  P dR u  50-­‐50  P dR u  80-­‐20  P dR u  90-­‐10  P dR u  95-­‐5  P dR u  99-­‐1I/mA  cm-­‐2  at  3000  s

P d -­‐0.018399:1 0.014595:5 0.013590:10 0.023980:20 0.019750:50 0.0171

E  =  -­‐0.96  V

0 1000 2000 3000 4000

0.0

0.2

 

C A s  for  va rious  [E tO H ]  in  1M  K O H  us ing  P d95R u

5/C  a t  E = -­‐0.96V  

I/mA  cm

-­‐2

time/s

 0 .1  M  0.4M  0.6  M  0.8  M  1M  1.5  M  2  M  3  M

I/mAcm2  at  3000s0.1  M 0.002750.4  M 0.02510.6  M 0.04150.8  M 0.03911.0  M 0.06851.5  M 0.06132.0  M 0.04643.0  M 0.0477

-­‐1.6 -­‐1.4 -­‐1.2 -­‐1.0 -­‐0.8 -­‐0.6 -­‐0.4

-­‐0.20

-­‐0.15

-­‐0.10

-­‐0.05

0.00

0.05

0.10

0.15

0.20

0.25

-­‐1.6 -­‐1.4 -­‐1.2 -­‐1.0 -­‐0.8 -­‐0.6 -­‐0.4

-­‐0.4

-­‐0.3

-­‐0.2

-­‐0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

-­‐1.6 -­‐1.4 -­‐1.2 -­‐1.0 -­‐0.8 -­‐0.6 -­‐0.4-­‐0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

 

 

I/mA  cm

-­‐2

E we/V  vs .  MS E  (V )

 K O H  1M  E tO H  IM  K O H  1M

P d50R u50/C

-­‐1.28  V

 

 

I/mA  cm

-­‐2

E we/V  vs .  MS E  (V )

 K O H  1M  E tO H  IM  K O H  1M

-­‐1.23  V

P d80R u

20/C

 

 

I/mA  cm

-­‐2

E we/V  vs .  MS E  (V )

 K O H  1M  E tO H  IM  K O H  1M

P d90R u

10/C

-­‐1.19  V

-­‐1.6 -­‐1.4 -­‐1.2 -­‐1.0 -­‐0.8 -­‐0.6 -­‐0.4

-­‐0.15

-­‐0.10

-­‐0.05

0.00

0.05

0.10

0.15

-­‐1.6 -­‐1.4 -­‐1.2 -­‐1.0 -­‐0.8 -­‐0.6 -­‐0.4-­‐0.6

-­‐0.4

-­‐0.2

0.0

0.2

0.4

0.6

-­‐1.6 -­‐1.4 -­‐1.2 -­‐1.0 -­‐0.8 -­‐0.6 -­‐0.4-­‐1.5

-­‐1.0

-­‐0.5

0.0

0.5

1.0

1.5

 

 P d95R u

5

I/mA  cm

-­‐2

E we/V  vs  MS E  (V )

 C yc le1  C yc le3 0.110  V

 

P d90R u

10

I/mA  cm

-­‐2

E we/V  vs  MS E  (V )

 C yc le1  C yc le3 0.561  V

P d80R u

20

 

I/mA  cm

-­‐2

E we/V  vs  MS E  (V )

 C yc le1  C yc le3

1.196  V

Fig. 6: CAs for PdxRu1-x/C samples in 1M KOH+1M EtOH at E=-0.96V

Fig. 7: CAs for various [EtOH] in 1M KOH using Pd95Ru5/C at E=-0.96V

•  With  highest  consistent  current  intensity  at  a  potential  of  -­‐0.96  V  and  a  low  onset  potential,  Pd90Ru10/C  proves  to  be  one  of  the  most  effective  combination.  Pd80Ru20/C  presents  with  a  high  intensity,  a  lower  onset  potential  and  a  smaller  loading  of  Pd  which  makes  it  cheaper  than  the  Pd90Ru10/C  and  an  equally  viable  option.  

•  1M  is  the  optimal  concentration  of  ethanol  in  the  electrolyte  solution.  

The  next  experiments  will  consist  of  testing  the  impact  of  ionic  conductibility  of  the  electrolyte  by  varying  the  KOH  concentration.  Also,  spectroscopy  will  be  used  during  the  experiment  in  order  to  identify  the  intermediates  products  and  understand  their  impact  on  the  kinetics  of  the  electrochemical  reaction.  

 Fig.  8  :  Direct  Alkaline  Methanol  Fuel  Cell1    

 Fig.  3  :  Two-­‐compartment-­‐cell  made  of  Te?lon  used  for  experimentation  

Experimentations:  •  Cyclicvoltammetry  •  Chronoamperommetry  •  CO  Stripping  

Fig 5: CVs of PdxRu1-x/C in 1M KOH (black curve) and 1M KOH+1M EtOH (red curve)

Fig. 4: CO stripping of PdxRu1-x/C in 1M KOH

Table  1:  Electrochemical  potentials  and  current  intensities  of  PdxRu1-­‐x  catalysts  measured  by  CV  and  CO  Stripping  

Fig.  2:  Method  of  electrode  preparation

(1)Yu,  E.  H.;  Krewer,  U.;  Scott,  K.  Energies  2010,  3,  1499–1528.  (2)Kamarudin,  M.  Z.  F.;  Kamarudin,  S.  K.;  Masdar,  M.  S.;  Daud,  W.  R.  W.  Int.  J.  Hydrog.    Energy  2013,  38,  9438–9453.  (3)  Antolini,  E.;  Gonzalez,  E.  R.  J.  Power  Sources  2010,  195,  3431–3450.  (4)  Ribadeneira,  E.;  Hoyos,  B.  A.  J.  Power  Sources  2008,  180,  238–242.  (5)  Evans M. et al. Effect of Surface Structure on Catalytic Activity of PdxRu1- x/C Nanoparticles for Ethanol Electrooxidation, (To be submitted). 1  “Direct  Methanol  Alkaline  Fuel  Cell  Simple”,  2011,  http://vector.me/search/  engineering,  viewed  on  January  21st  2014.  

This  research  was  supported  by  the  University  of  Ottawa’s  Undergraduate  Research  Opportunity  Program  (UROP).  

Electrolyte

W.E C.E

NO2 CO

Excess Gas

R.E