Effect of hollowgraphitizedspheressupportedPt ... · cluster project, Hollow Graphitized Spheres...
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Effect of hollow graphitized spheres supported Pt cathode catalyst on MEA f i Middl T t DMFC MEA performance ina Middle T emperature DMFC T. Tesfu‐Zeru and J.‐F. Drillet Funded by: BMWi via AiF Period: 01.06.2010 – 28.02.2013 e‐mail: [email protected] In recent years effort has been made in order to develop a middle temperature (100 150 C) Table 1: Summary of max measured power densities in DMFC at 110 C/2bar with O 2 and air Introduction & Motivation In recent years, effort has been made in order to develop a middle temperature (100‐150 C) PEM fuel cell. Therefore, more corrosion‐resistant catalyst supports with mesoporous surface are needed as substitution material i.e. for Vulcan XC72R. In the framework of a research cluster project, Hollow Graphitized Spheres (HGS) material has been synthesized by the group of Prof. Schüth at MPI‐Mülheim Germany (see fig. 1). This has an excellent corrosion resistance and is supposed to slow down agglomeration and depletion of Pt particles. The work investigates the influence of the HGS versus Vulcan as cathode material on the performance of the MEA in a 5 cm² laboratory direct methanol fuel cell (DMFC). Table 1: Summary of max. measured power densities in DMFC at 110 C/2bar with O 2 and air Experimental description of HGS & MEA preparation MEA/Support Cathode cat. loading / mg Pt cm ‐2 Oxygen / mW cm ‐2 Air / mW cm ‐2 MEA5/HGS 1.6 223 110 MEA6/Vulcan 200 105 MEA14 /HGS 2 200 110 MEA15/Vulcan 220 120 MEA9/HGS 3.3 ‐ 55 MEA10/Vulcan 250 178 MEA with low HGS supported Pt catalyst loading exhibits higher performances Pt and Pt‐Ru catalyst: Pt 50 Ru 50 and Pt‐catalysts were prepared by impregnation of H 2 PtCl 6 and RuCl 3 in H 2 O/CH 2 O and CH 2 O, respectively at 80°C on carbon support. Pt particle size is in the range of 4.5 and 4.1 +/‐ 1nm for Pt/HGS and Pt/Vulcan, respectively. Anode & Cathode: Pt‐Ru/Vulcan, Pt/HGS or Pt/Vulcan catalyst was mixed in water/isopropanol with 10%wt Nafion and 20%wt PTFE. The catalyst ink was sprayed with PRISM 450 (USI) device either on -50 0 50 100 mAcm -2 0 08 0.12 0.16 0.20 /Acm -2 Fig. 1: (MPI Mülheim) HGS HGS: ADT and methanol permeation tests MEA with low HGS‐supported Pt catalyst loading exhibits higher performances compared to that of Pt/Vulcan At higher Pt loading than 2mg cm ‐2 , mass transport limitation in MEA with HGS‐ containing cathode is obvious. Toray TGP‐H‐60 or Freudenberg‐CH2315CX190 with a microporous layer (MPL), respectively. MEA: The anode and cathode gas diffusion electrodes were coated with 1mgcm ‐2 Nafion suspension before hot pressing at 130°C and 7bar with the Nafion117 membrane. ADT: Accelerated Degradation Tests (ADT) were carried out at the air electrode by means of cyclic voltammetry at 80°C in N 2 (400 ml min ‐1 ) whereas PtRu/Vulcan was flooded with H 2 (200 ml min ‐1 ). The scan rate was 100 mV/s. MeOH permeation: The cell was polarized in the electrolysis mode by using linear sweep voltammetry technique at 5mV/s. PtRu and Pt 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 -150 -100 i /m U /V MEA9-2.cycle MEA9-1000.cycle MEA10-2.cycle MEA10-1000. cycle 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0.00 0.04 0.08 U /V i MEA9-80°C MEA9-100°C MEA10-80°C MEA10-100°C Fig. 2: Pt/vulcan Fig. 7: (left) ADT and (right) methanol permeation experiments at MEA9 & 10 • No visible H 2 region for the HGS‐supported Pt catalyst. • Increase of H 2 ads./des. peak area after ADT in the case of MEA with Vulcan supported cathode catalyst! • Methanol permeation increases with cell temperature. Fig. 3: Pt/HGS GDL Pt‐Ru/Vulcan Membrane Pt/HGS MPL GDL GDL Pt‐Ru/Vulcan Membrane Pt/Vulcan MPL GDL 02 0,4 0,6 U /V 0,06 0,09 0,12 0,15 0,18 P /Wcm -2 electrode was fed with 1 M MeOH and N 2 , respectively. MEA composition & current‐voltage curves of the MEAs Results Anode: 2 mg Pt cm ‐2 (35%wt) Pt‐Ru/Vulcan Membrane: Nafion117 MEA‐5: Cathode: 1,6 mg Pt cm ‐2 Pt/HGS MEA‐6: Cathode: 1,6 mg Pt cm ‐2 Pt/Vulcan MEA‐9: Cathode: 3,3 mg Pt cm ‐2 Pt/HGS Fig. 3: Pt/HGS SEM images of cross‐sectioned MEA9 & 10 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,2 MEA9 MEA10 At 110°C/2bar air i /Acm -2 0,00 0,03 Fig. 4: MEA9 & MEA10 at 110 C/2bar with air Pt MEA‐10: Cathode: 3,3 mg Pt cm ‐2 Pt/Vulcan MEA‐14: Cathode: 2 mg Pt cm ‐2 Pt/HGS MEA‐15: Cathode: 2 mg Pt cm ‐2 Pt/Vulcan all 30%wt Fig. 7: Cross‐sectional SEM images of (left) MEA9 and (right) MEA10 . Additional area and spot EDX spectra of MEA9 are presented below • Similar thickness of about 200 μm was measured for 3.3 mgcm ‐2 Pt/HGS and Pt/Vulcan cathodes; The thickness of the 2mg Pt cm ‐2 PtRu layer and MPL is about 100 and 50 μm, respectively. • Distribution of particles in HGS reaction layer is inhomogeneous: This could explain 0,4 0,6 0,8 U /V 0,12 0,16 0,20 0,24 P /Wcm 0,3 0,4 0,5 0,6 0 04 0,06 0,08 0,10 0,12 P /W c U /V Fig. 5: MEA5 & MEA6 at 110 C/2bar (left) with oxygen and (right) with air Conclusion the lower performance during DMFC test in comparison to the MEA with the Vulcan‐ based cathode. • The EDX spectra show an almost uniform Pt distribution throughout the reaction layer. A maximal power density of 178 mWcm ‐2 was achieved with a 3.3 mgcm ‐2 Vulcan‐ supported Pt cathode (MEA10) at 110 C and 2 bar. Better cell performances with HGS‐based cathode was observed only for “low” catalyst loading of 1.6 mg Pt cm ‐2 (MEA5). At higher catalyst loading, MEA with Vulcan‐based cathodes exhibit higher power 0,0 0,2 0,4 0,6 0,8 1,0 1,2 0,0 0,2 MEA-5 MEA-6 Bei 110 °C /2bar O 2 i /Acm -2 0,00 0,04 0,08 m -2 0,0 0,2 0,4 0,6 0,8 0,1 0,2 i /Acm -2 MEA 5 MEA 6 At 110 °C / 2 bar air 0,00 0,02 0,04 cm -2 0,4 0,6 0,8 U/V 0 10 0,15 0,20 0,25 P/Wc 0,4 0,6 U/V 0 06 0,08 0,10 0,12 0,14 P /Wc We thank BMWi for financial support, project partners for excellent cooperation and our mechanical workshop for the technical support. Fig. 6: MEA14 & MEA15 at 110°C/2bar (left) with oxygen and (right) with air densities. Inhomogeneous HGS‐based catalyst layer observed by SEM could explain their relative low performances in the DMFC cell. Spraying procedure for HGS‐based inks has to be improved No higher stability for HGS‐based electrodes observed during ADT: Pt particle size has probably to be better fitted to mesoporous surface of HGS. ADT should be optimized for electrodes with catalyst loading > 2 mg Pt cm ‐2 . 0,0 0,2 0,4 0,6 0,8 1,0 1,2 0,0 0,2 i /Acm -2 MEA14 MEA15 at 110°C/2bar O 2 0,00 0,05 0,10 cm -2 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,0 0,2 i /Acm -2 MEA14 MEA15 at 110°C/2bar air 0,00 0,02 0,04 0,06 cm -2
Transcript of Effect of hollowgraphitizedspheressupportedPt ... · cluster project, Hollow Graphitized Spheres...
Effect of hollow graphitized spheres supported Pt cathode catalyst on MEA f i Middl T t DMFCMEA performance in a Middle Temperature DMFC
T. Tesfu‐Zeru and J.‐F. DrilletFunded by: BMWi via AiF
Period: 01.06.2010 – 28.02.2013e‐mail: [email protected]
In recent years effort has been made in order to develop a middle temperature (100 150 C) Table 1: Summary of max measured power densities in DMFC at 110 C/2bar with O2 and air
Introduction & Motivation
In recent years, effort has been made in order to develop a middle temperature (100‐150 C)PEM fuel cell. Therefore, more corrosion‐resistant catalyst supports with mesoporous surfaceare needed as substitution material i.e. for Vulcan XC72R. In the framework of a researchcluster project, Hollow Graphitized Spheres (HGS) material has been synthesized by the groupof Prof. Schüth at MPI‐Mülheim Germany (see fig. 1). This has an excellent corrosionresistance and is supposed to slow down agglomeration and depletion of Pt particles. Thework investigates the influence of the HGS versus Vulcan as cathode material on theperformance of the MEA in a 5 cm² laboratory direct methanol fuel cell (DMFC).
Table 1: Summary of max. measured power densities in DMFC at 110 C/2bar with O2 and air
Experimental description of HGS & MEA preparation
MEA/SupportCathode cat. loading
/ mgPt cm‐2
Oxygen
/ mW cm‐2
Air
/ mW cm‐2
MEA5/HGS1.6
223 110
MEA6/Vulcan 200 105
MEA14 /HGS2
200 110
MEA15/Vulcan 220 120
MEA9/HGS3.3
‐ 55
MEA10/Vulcan 250 178
MEA with low HGS supported Pt catalyst loading exhibits higher performances
Pt and Pt‐Ru catalyst: Pt50Ru50 and Pt‐catalysts were prepared byimpregnation of H2PtCl6 and RuCl3 in H2O/CH2O and CH2O,respectively at 80°C on carbon support. Pt particle size is in therange of 4.5 and 4.1 +/‐ 1nm for Pt/HGS and Pt/Vulcan, respectively.Anode & Cathode: Pt‐Ru/Vulcan, Pt/HGS or Pt/Vulcan catalyst wasmixed in water/isopropanol with 10%wt Nafion and 20%wt PTFE.The catalyst ink was sprayed with PRISM 450 (USI) device either on -50
0
50
100
m
Ac
m-2
0 08
0.12
0.16
0.20
/A
cm
-2
Fig. 1: (MPI Mülheim) HGS
HGS:
ADT and methanol permeation tests
MEA with low HGS‐supported Pt catalyst loading exhibits higher performancescompared to that of Pt/VulcanAt higher Pt loading than 2mg cm‐2, mass transport limitation in MEA with HGS‐containing cathode is obvious.
y p y ( )Toray TGP‐H‐60 or Freudenberg‐CH2315CX190 with a microporouslayer (MPL), respectively.MEA: The anode and cathode gas diffusion electrodes were coatedwith 1mgcm‐2 Nafion suspension before hot pressing at 130°C and7bar with the Nafion117 membrane.ADT: Accelerated Degradation Tests (ADT) were carried out at theair electrode by means of cyclic voltammetry at 80°C in N2 (400 mlmin‐1) whereas PtRu/Vulcan was flooded with H2 (200 ml min‐1). Thescan rate was 100 mV/s.MeOH permeation: The cell was polarized in the electrolysis modeby using linear sweep voltammetry technique at 5mV/s. PtRu and Pt
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
-150
-100i /m
U /V
MEA9-2.cycle MEA9-1000.cycle MEA10-2.cycle MEA10-1000. cycle
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.60.00
0.04
0.08
U /V
i
MEA9-80°C MEA9-100°C MEA10-80°C MEA10-100°C
Fig. 2: Pt/vulcan
Fig. 7: (left) ADT and (right) methanol permeation experiments at MEA9 & 10
• No visible H2 region for the HGS‐supported Pt catalyst.• Increase of H2 ads./des. peak area after ADT in the case of MEA with Vulcansupported cathode catalyst!• Methanol permeation increases with cell temperature.Fig. 3: Pt/HGS
GDL
Pt‐Ru/Vulcan
Membrane
Pt/HGSMPL
GDL
GDL
Pt‐Ru/Vulcan
Membrane
Pt/VulcanMPL
GDL
0 2
0,4
0,6
U /V
0,06
0,09
0,12
0,15
0,18
P /W
cm-2
electrode was fed with 1 M MeOH and N2, respectively.
MEA composition & current‐voltage curves of the MEAs
Results
Anode: 2 mg Pt cm‐2 (35%wt) Pt‐Ru/Vulcan
Membrane: Nafion117
MEA‐5: Cathode: 1,6mgPt cm‐2 Pt/HGS
MEA‐6: Cathode: 1,6mgPt cm‐2 Pt/Vulcan
MEA‐9: Cathode: 3,3mgPt cm‐2 Pt/HGS
Fig. 3: Pt/HGS
SEM images of cross‐sectioned MEA9 & 10
0,0 0,2 0,4 0,6 0,8 1,00,0
0,2
MEA9 MEA10
At 110°C/2bar air
i /Acm-20,00
0,03
,
Fig. 4: MEA9 & MEA10 at 110 C/2bar with air
gPtMEA‐10: Cathode: 3,3mgPt cm
‐2 Pt/Vulcan
MEA‐14: Cathode: 2mgPt cm‐2 Pt/HGS
MEA‐15: Cathode: 2mgPt cm‐2 Pt/Vulcan
all 30%wt
Fig. 7: Cross‐sectional SEM images of (left) MEA9 and (right) MEA10 . Additional areaand spot EDX spectra of MEA9 are presented below
• Similar thickness of about 200 µm was measured for 3.3 mgcm‐2 Pt/HGS andPt/Vulcan cathodes; The thickness of the 2mgPt cm
‐2 PtRu layer and MPL is about 100and 50 µm, respectively.• Distribution of particles in HGS reaction layer is inhomogeneous: This could explain
0,4
0,6
0,8
U /
V
0,12
0,16
0,20
0,24
P /W
cm 0,3
0,4
0,5
0,6
0 04
0,06
0,08
0,10
0,12
P/W
cU /V
Fig. 5: MEA5 & MEA6 at 110 C/2bar (left) with oxygen and (right) with air Conclusion
p y g pthe lower performance during DMFC test in comparison to the MEA with the Vulcan‐based cathode.• The EDX spectra show an almost uniform Pt distribution throughout the reactionlayer.
A maximal power density of 178 mWcm‐2 was achieved with a 3.3 mgcm‐2 Vulcan‐supported Pt cathode (MEA10) at 110 C and 2 bar.
Better cell performances with HGS‐based cathode was observed only for “low”catalyst loading of 1.6 mgPt cm
‐2 (MEA5). At higher catalyst loading, MEA with Vulcan‐based cathodes exhibit higher power
0,0 0,2 0,4 0,6 0,8 1,0 1,20,0
0,2 MEA-5 MEA-6
Bei 110 °C /2bar O2
i /Acm-2
0,00
0,04
0,08
m-2
0,0 0,2 0,4 0,6 0,8
0,1
0,2
i /Acm-2
MEA 5 MEA 6
At 110 °C / 2 bar air 0,00
0,02
0,04
cm-2
0,4
0,6
0,8
U/V
0 10
0,15
0,20
0,25
P/W
c
0,4
0,6
U/V
0 06
0,08
0,10
0,12
0,14
P /W
c
We thank BMWi for financial support, project partners for excellent cooperation and our mechanical workshop for the technical support.
Fig. 6: MEA14 & MEA15 at 110°C/2bar (left) with oxygen and (right) with air
densities. Inhomogeneous HGS‐based catalyst layer observed by SEM could explain their
relative low performances in the DMFC cell. Spraying procedure for HGS‐based inks has to be improved No higher stability for HGS‐based electrodes observed during ADT: Pt particle size
has probably to be better fitted to mesoporous surface of HGS. ADT should be optimized for electrodes with catalyst loading > 2 mgPt cm
‐2.
0,0 0,2 0,4 0,6 0,8 1,0 1,20,0
0,2
i /Acm-2
MEA14 MEA15
at 110°C/2bar O2
0,00
0,05
0,10 cm-2
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,70,0
0,2
i /Acm-2
MEA14 MEA15
at 110°C/2bar air
0,00
0,02
0,04
0,06
cm-2
