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Clean Energy Research at the University of South Carolina
Dr. Ralph E. White, PIJames A. Ritter, co-PI and Presenter
University of South Carolina
May 24, 2005
Project ID #ST9 WhiteThis presentation does not contain any proprietary or confidential information.
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OverviewProject start date June 1, 2004 (1st year project) Project end date November 30, 2005Five co-projects initiated30 Percent complete
Total project fundingDOE share $2,158,370contractor share $539,593$ split nearly equally among the five projects
Timeline
Budget
Project I. Low Temperature Electrolytic Hydrogen Production (Dr. John Weidner) Project II. Development of Complex Metal Hydride Hydrogen Storage Materials (Dr. James Ritter)Project III. Hydrogen Storage Using Chemical Hydrides (Dr. Michael Matthews)Project IV. Diagnostic Tools for Understanding Chemical Stresses and MEA Durability Resulting from Hydrogen Impurities (Dr. John Van Zee) Project V. Durability Study of the Cathode of a Polymer Electrolyte Membrane Fuel Cell (Dr. Ralph White)
Projects
• The most significant hydrogen hazards associated with this project are:• High reactivity of solid chemical
hydrides when exposed to humidified air• Toxicity: Avoid ingestion or contact
with eyes and mucous membranes
• The approach to deal with this hazard is:• Handle hydrides in an inert atmosphere
within a glove box• Use small quantities for laboratory
experiments• Blanket reactor with inert gas
Safety
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Technical Barriers and Targets
DOE Targets:• 2005 – 1.5 kWh/kg (4.5 wt %), 1.2
kWh/L, $6/kWh• 2010 – 2 kWh/kg (6 wt %), 1.5 kWh/L,
$4/kWh• 2015 – 3 kWh/kg (9 wt %), 2.7 kWh/L,
$2/kWhTechnical Barriers:- higher system weight, high volume- high cost of storage- durability of at least 1500 cycles- lower than expected energy efficiency- long refueling time
Hydrogen Storage Fuel CellDOE Targets:• $30/kW for transportation• 5,000 hr lifespan• 40 to 80 oC operating range• electrode performanceTechnical Barriers:• high system weight and volume• high cost• unproven durability• air, thermal and water management
DOE Barriers:• high-temperature, corrosion
resistant materials• chemical reaction data• system design
Nuclear H2 Production
DOE Targets:• improved materials• create reaction database• more efficient system designs
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Project II: Development of Complex Metal Hydride Hydrogen Storage Materials (Dr. James Ritter)
ObjectivesStudy the effect of different metal dopants and coStudy the effect of different metal dopants and co--dopants dopants on dehydrogenation (discharge or desorption) of NaAlHon dehydrogenation (discharge or desorption) of NaAlH44
Study the effect of different carbon materials as a coStudy the effect of different carbon materials as a co--dopant with Ti and Al powder on dehydrogenation dopant with Ti and Al powder on dehydrogenation (discharge or desorption) and hydrogenation (charge or (discharge or desorption) and hydrogenation (charge or adsorption) of NaAlHadsorption) of NaAlH44
Study the effectiveness of a new sonochemical Study the effectiveness of a new sonochemical pretreatment method for improving the dehydrogenation pretreatment method for improving the dehydrogenation and hydrogenation kinetics ofand hydrogenation kinetics of NaAlHNaAlH44
Study the reversibility of LiAlHStudy the reversibility of LiAlH44 and Mg(AlHand Mg(AlH44))22 when doped when doped with Ti under conditions similar to those that are effective with Ti under conditions similar to those that are effective with Tiwith Ti--doped NaAlHdoped NaAlH44
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Approachprepare samples of NaAlH4, LiAlH4 and Mg(AlH4)2 using a conventional wet or new sonochemical doping procedure prior to high energy ball milling
cycle the prepared samples in a unique high pressure cycling facility to obtain qualitative discharge and charge kineticsdischarge the prepared samples in a TGA to obtain quantitative kinetics and capacities under temperature programmed and constant temperature desorption modescharacterize the prepared samples in terms of their dehydrogenation and hydrogenation kinetics, capacity and reversibility
samples possibly doped with Ti, Zr, Fe, Al powder and or various forms of carbon
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0.0
1.0
2.0
3.0
4.0
5.0
50 100 150 200 250Temperature [ oC ]
Des
orbe
d H
2 [ w
t% ] 4 mol% Fe
3 mol% Fe, 1 mol% Zr2 mol% Fe, 2 mol% Zr1 mol% Fe, 3 mol% Zr4 mol% ZrSeries6Series7Series8
A
C
B
Observed
PredictedA 3 mol% Fe, 1 mol% ZrB 2 mol% Fe, 2 mol% ZrC 1 mol% Fe, 3 mol% Zr
Predicted TPD is expected Predicted TPD is expected behavior of a simple behavior of a simple physical mixture, i.e., linear physical mixture, i.e., linear combination, of the two combination, of the two metal dopants.metal dopants.Observed TPD is the actual Observed TPD is the actual synergistic behavior of the synergistic behavior of the two metal dopants.two metal dopants.Observed synergism, Observed synergism, in in most casesmost cases, is , is much bettermuch betterthan 4 mol% than 4 mol% ZrZr alone!alone!Consistent with the Consistent with the ““metalmetal--metal bond polaritymetal bond polarity””concept, in that concept, in that ZrZr and Feand Feare from are from opposite sidesopposite sides of of the periodic table.the periodic table.Ti and Fe exhibit similar Ti and Fe exhibit similar behavior; but not Ti and behavior; but not Ti and ZrZr..
TPD: Synergistic Effects of Co-Dopants, Zrand Fe, on the Dehydrogenation of NaAlH4
Is there a combination of early and late transition metals that could instill superior performance compared to a single metal
dopant like Ti? This supposition is being explored.
J. Wang, A. D. Ebner, R. Zidan, and J. A. Ritter, J. Alloys and Compounds, 391, 245-255 (2005).
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Influence of Different Carbon Materials on Dehydrogenation Influence of Different Carbon Materials on Dehydrogenation and Hydrogenation Rates of Carbonand Hydrogenation Rates of Carbon--Doped and Cycled NaAlHand Cycled NaAlH44
-50
-40
-30
-20
-10
0
10
20
30
40
50
0 20 40 60 80Time (Min)
(P-P
o)/m
ass
(psi
g/g)
SWNT
No Carbon
C-60MWNTAc Carbon
Graphite
DischargePo = 20 psia
ChargePo = 1250 psia
125 oC
At T = 125 oC and P = 1,250 psia charging of Ti
and carbon doped materials occurs within 10 min!
Samples doped with Ti and carbon consistently
showed faster dehydrogenation and
rehydrogenation rates over just Ti-doped samples.
Samples doped with SWNTs and graphite
showed the strongest and weakest effects,
respectively.
All samples doped with 2 mol% Ti and 5 wt% Al and cycled 5 timesAll samples doped with 2 mol% Ti and 5 wt% Al and cycled 5 timesAll samples containing carbon doped with 10 wt%All samples containing carbon doped with 10 wt%
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-50
-40
-30
-20
-10
0
10
20
30
40
50
0 20 40 60 80 100Time, min
(P-P
o)/m
ass,
psi
/g
125 oC
Charge (Po = 1250 psia)
Discharge (Po = 15 psia)
cycle # 1 2 4
cycle # 1 2 4
Influence of Sonochemical Influence of Sonochemical PreTreatmentPreTreatment on Hydrogenation on Hydrogenation and Dehydrogenation Rates During Cyclingand Dehydrogenation Rates During Cycling
Influence of sonochemical PT on both dehydrogenation and
hydrogenation kinetics, is clearly observed. The time for
charging is markedly decreased again by a factor of four, from about 60 to 15 min.
Again, these results may represent the best charge
kinetics to date for a sample of NaAlH4 doped with as
little as 2 mol% Ti.
Ball milled samples of NaAlH4 wet doped and sonochemically doped in decalin with THF, all doped with 2 mol% Ti. Filled symbols correspond to the sonochemically doped sample;
empty symbols correspond to the wet doped sample.
T. Prozorov, J. Wang, A. D. Ebner and J. A. Ritter, J. Alloys and Compounds, submitted (2005).
J. A. Ritter, A. D. Ebner J. Wang, T. Prozorov, Provisional Patent Application, filed February 28, (2005).
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-0.5
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
50 100 150 200 250 300
Temperature (oC)
Des
orbe
d hy
drog
en (w
t%) 1%Ti/Mg(AlH4)2 0cycle
2%Ti/NaAlH4 5cycles
2%Ti/NaAlH4 0cycle
2%Ti/LiAlH4 5cycles1%Ti/Mg(AlH4)2 5cycles
2%Ti/LiAlH4 0cycle
Comparison of 0Comparison of 0thth with 5with 5thth Discharge Cycle of Discharge Cycle of TiTi--Doped NaAlHDoped NaAlH44, LiAlH, LiAlH44 and and Mg(AlHMg(AlH44))22
Five discharge (4 hrs) and charge (8 hrs) cycles carried out between 50
and 1,200 psig at 125 oCfor Na alanate BM 120 min, between 50 and
2,100 psig at 140 oC for Li alanate BM for 20
min, and between 50 and 1,500 psig at 150 oC for Mg alanate BM 15 min.
Rate = 5 Rate = 5 ooCC/min/minJ. Wang, A. D. Ebner and J. A. Ritter,
Adsorption, 11, 811-816 (2005).
Under these conditions, only the Na alanate
system is observed to be reversible! The Li
and Mg alanates systems do not exhibit
any reversibility.
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Future Research DirectionsFY05 – FY06
complete Raman study of Ticomplete Raman study of Ti--doped NaAlHdoped NaAlH4 4 with Dr. Williamswith Dr. Williamscontinue to explore bimetallic and metalcontinue to explore bimetallic and metal--carbon catalyzed alanates carbon catalyzed alanates
continue to explore new sonochemical pretreatment method possiblcontinue to explore new sonochemical pretreatment method possibly y as an alternative to ball milling metalas an alternative to ball milling metal--doped alanates doped alanates continue to work with Dr. continue to work with Dr. AngerhoferAngerhofer at UF on carrying out high at UF on carrying out high field EPR studies with doped alanatesfield EPR studies with doped alanatescontinue to work with Dr. continue to work with Dr. RasolovRasolov at USC on at USC on abab initioinitio studies of studies of TiClTiCl33--NaAlHNaAlH44 clustersclusterscontinue to synthesize and study the reversibility of other metacontinue to synthesize and study the reversibility of other metal doped l doped alanates and alanates and boronatesboronates, and to carry out a thermodynamic analysis to , and to carry out a thermodynamic analysis to explain their inherent stabilityexplain their inherent stability
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Objectives Develop hydrogen storage and delivery technology based on steam + chemical hydrides for automotive fuel cell applications
Project III: Hydrogen Storage Using Chemical Hydrides (Dr. Michael Mathews)
• Evaluate novel steam + solid chemical hydride reaction as basis for on-demand production of hydrogen
• Compare experimental data to FreedomCAR targets– Mass efficiency of reaction (8MAA)– Hydrogen production rate / kinetic data (12MAA)– Analysis of water utilization of reactor and characterization
of hydration characteristics of products (14MAA)– Prototype design development (16 MAA)
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Approach• Hydrolyze chemical hydrides with dry steam, rather
than aqueous catalytic process– Chemically simple reaction– Humid H2 gas product– Hydride reactants and products are dry– Minimal water inventory in the reactor– Autothermal integration: use heat of reaction to produce steam
• Operate reactor at low temperatures (100 OC – 150 OC) and pressures
• Conduct basic research on the reaction to utilize water efficiently and maximize H2 delivery rate– Translate results to prototype design via mathematical model
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Approach
0
1
2
3
4
5
6
0 1 2 3 4 5
Specific Energy (kWh/kg)
Spec
ific
Den
sity
(kW
h/L)
FreedomCAR (2015)
FreedomCAR (2010)
FreedomCAR (2005)
NaAlH4
LiAlH4
NaBH4
LiBH4
Currentsystem
Liquid hydrogenComp. GasNaBH4
Metal hydride
Design system using steam hydrolysis technology so that total system Specific energy & density remain within FreedomCAR bounds.
Gasoline(12 kWh/kg)
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Films of Recrystallized NaBH4 Give Improved Initial Rates• Thin films give
higher initial rates (x= 2-3)
• Yields < 100% are attributed to channeling within reactor and insufficient reactant contact at longer times.
x is an indirect measurement of the efficiency of water utilization of the reaction
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120 140 160 180 200
Time (min)
% H
2 yie
ld
Theoretical rates
x=0 x=4
x=6
NaBH4 Powder
NaBH4 Films
Target (wt%)
Equiv. x
2005 4.5 4
2010 6.0 3
2015 9.0 1
FreedomCar Gravimetric Efficiency
NaBH4 + (2+x)H2O → 4H2 (g)+ NaBO2 ·x H2O
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Water Utilization and Product Characterization
• NaBO2·xH2O product is a dense solid
– Dense by-product causes mass transfer limitation
– Highly hydrated byproducts• Wastes water and decreases
gravimetric efficiency
Unreactedhydride
NaBO2·xH2Oshell
Steam
• Investigate hydration properties of products with Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) – TGA: 17 wt% loss
associated with H2O loss by borate product
– DSC: peak indicates phase transition in products
0
50
100
150
200
30 80 130 180 230 280 330 380Temperature (oC)
Hea
t Flo
w
42
43
44
45
46
47
48
49
50
51
Wei
ght (
mg)
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Future Research DirectionsFY05• Steam/solid NaBH4 system
– Obtain improved gravimetric efficiency of reaction• Liberate H2 wt% > 4.5 by 4/30/2005
– Measure intrinsic kinetic rate of reaction under different operating temperatures, pressures and reactant preparations
• Full flow of H2 in < 10 sec by 10/30/2005– Clarify the effect of particle size on reactant contact and mass transfer– Determine hydration characteristics of products in order to improve
gravimetric efficiency and understand shell formation • Investigate additional solid hydride systems
– Evaluate additional hydrides based on FreedomCAR requirementsFY06• Submit description of prototype system design
– Design will be based on laboratory-scale experiments– Design will be evaluated according to FreedomCar targets such as mass
and volumetric efficiency and startup dynamics
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Project I: Low Temperature Electrolytic Hydrogen Production (Dr. John Weidner)
Objective
Develop a gas phase proton exchange membrane (PEM) electrolyzer to convert
HBr to Br2 and H2SO2 to H2SO4 and H2
ProvideHigher current densities (i.e., small, low cost electrolyzer)Better thermal managementLower voltages (i.e., higher efficiencies)Lower reactant crossover (i.e., reduced posioning)Better control of product purityLower catalyst loadings
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Gas Phase Electrolysis Delivers
0.0
0.5
1.0
1.5
2.0
0 2 4 6 8 10 12 14 16 18 20
Current Density, kA/m2
Vol
tage
, V
Liquid-phase HCl Reaction (Commercial Uhde Process)
Gas-phase HClGas-phase HBr
x Gas Phase SO2 oxidation data 1 atm; 80oC; 0.65 mg Pt/cm2
Westinghouse projection 5-20 atm; 80oC [1]
[1] P.W. Lu et. al., J. Appl. Electrochem., 347 (1981).
■ Westinghouse SO2 oxidation data 1 atm; 50oC; 7 mg Pt/cm2 [1]
Future WorkFY05 – FY06• quantify the relationships among design and operating parameters• integrate electrolyzer information into the system-level Aspen model
developed by SRNL • quantify the extent of sulfur poisoning and attempt to minimize its
affect• decrease current and increase voltage for SO2 oxidation. (Goal: 5
kA/m2 @ 0.6V)• improve water management
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Project IV: Diagnostic Tools for Understanding Chemical Stresses and MEA Durability Resulting from Hydrogen
Impurities (Dr. John Van Zee)Objectives
Develop Predictive Capabilities to Assess Durability and Failures Resulting From H2 Impurities
H2S, NH3 as models for catalysts poisoning and ionomer attackCompare with Computational Fluid Dynamic Models for CO Poisoning
ProvideMethodology for 3-D predictions of poisonsRate constants and mechanisms for poisoning Predictions and verifications of local distribution of poisons Improved tolerance by adjustment of operating conditionsUnderstanding of dosage, concentration, and interaction effects
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Significant Results/ApproachLocal CO coverage distribution on anode catalyst surface at selected points
for 1000 ppm CO; similar distributions are expected for H2S data below.
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 200 400 600 800 1000 1200 1400 1600 1800
Current density (mA/cm 2)
Cel
l vol
tage
(V)
I
IIIII
I
IIIII
Point # I: COavg = 0.75 at Vcell = 0.7 V
Point # II: COavg = 0.6 at Vcell = 0.5 V
0
100
200
300
400
500
600
0 2 4 6 8 10 12 14
Time (h)
Cur
rent
den
sity
(mA
/cm
2 )
96% performance loss
neat H2 5 ppm H2S/H2 CV
22 HSPtPtSH +−→+
H2 →H+ + 2e-
0
100
200
300
400
500
600
0 2 4 6 8 10 12 14
Time (h)
Cur
rent
den
sity
(mA
/cm
2 )
96% performance loss
neat H2 5 ppm H2S/H2 CV
22 HSPtPtSH +−→+
H2 →H+ + 2e-
1/T (K-1)
0.0027 0.0028 0.0029 0.0030 0.0031 0.0032
ln (k
fs P
H2S
)
-6.2
-6.0
-5.8
-5.6
-5.4
-5.2
-5.0
-4.8
-4.6
6653387)T/(
)Pkln( 02Hfs±−=
1d
d
5 ppm H2S at 50C
H2SCO
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Project V: Durability Study of the Cathode of a Polymer Electrolyte Membrane Fuel Cell (Dr. Ralph White)
Motivationkinetics of the O2 reduction reaction (ORR) at the cathode of a PEM fuel cell is usually described by Tafel equation, which predicts a straight line on a plot of the electrode potential versus the logarithm of ORR kinetic current (e.g., E vs. ln Ik).actual ORR kinetics do not follow the Tafel equation because a plot of E vs. ln Ik usually yields a curve, rather than a straight line, with two slopesthis will inevitably lead to errors in the evaluation of the relative importance of other transport phenomena, e.g., O2 diffusion
Objectivesto develop a semi-empirical equation to account for the ORR kinetic current, Ikto evaluate the goodness of using this equation in fitting the Rotating Disk Electrode (RDE) data measured on a catalyst used widely to make a PEM fuel cell
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Goodness of the Tafel Equation in Predicting the ORR Kinetic Current, Ik
Significant ResultsFuture Work
measure the RDE data over a wide range of temperatures, e.g., 40-80 ºCuse the semi-empirical kinetic equation to develop an accurate PEM fuel cell model
Goodness of the Semi-Empirical Model in Predicting the ORR
Kinetic Current, Ik
semi-empirical equation is far superior to the Tafel equationusing the semi-empirical equation in future PEM fuel cell modeling will improve the accuracy in the evaluation of the relative importance of other transport phenomena
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Collaborations
Current• Ragaiy Zidan: SRNL (melt processing
and scale-up)• Chris Williams: USC (Raman
spectroscopy studies)•• VitaliVitali RasolovRasolov: USC (: USC (abab initioinitio studies)studies)•• Alex Alex AngerhoferAngerhofer: UF (EPR studies): UF (EPR studies)Future• potential to interact with or become part
of the Metal Hydride Center of Excellence at SNL
RitterCurrent• William Summers: SRNL (Hybrid
Sulfur Process)Future• Richard Doctor: ANL (Modified Ca-Br
Process)• Michael Simpson: INEEL (Reverse
Deacon Process involving HCl)
Weidner
Future• potential to interact with or become
part of the Chemical Hydrogen Center of Excellence
Matthews
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Publications and Presentations1. J. Wang, A. D. Ebner and J. A. Ritter, “On the Reversibility of Hydrogen Storage in Novel Complex Hydrides,”
Adsorption, 11, 811-816 (2005).2. J. Wang, A. D. Ebner, R. Zidan, and J. A. Ritter, “Synergistic Effects of Co-Dopants on the Dehydrogenation
Kinetics of Sodium Aluminum Hydride,” J. Alloys and Compounds, 391, 245-255 (2005).3. J. Wang, A. D. Ebner, R. Zidan, and J. A. Ritter, “Effect of Graphite on the Dehydrogenation and Hydrogenation
Kinetics of Ti-Doped Sodium Aluminum Hydride,” J. Alloys and Compounds, in press (2005).4. T. Prozorov, J. Wang, A. D. Ebner and J. A. Ritter, “Sonochemical Doping of Ti-Catalyzed Sodium Aluminum
Hydride,” J. Alloys and Compounds, submitted (2005).5. J. Wang, R. C. Petty, A. D. Ebner, T. Prozorov and J. A. Ritter, Low Temperature Performance of Ti-Doped
Sodium Aluminum Hydride with Single Wall Carbon Nanotubes as a Co-Catalyst,” Nanotechnology, submitted (2005).
1. J. Wang, T. Prozorov, A. D. Ebner and J. A. Ritter, “Novel Complex Hydrides for Reversible Hydrogen Storage,”AIChE Annual Meeting, Austin, TX, November 2004.
Publications
Presentations
2. Michael A. Matthews, Thomas A. Davis, and Eyma Y. Marrero-Alfonso, “Hydrogen storage in chemical hydrides”, ACS National Meeting, Philadelphia, PA, August 2004.
3. Michael A. Matthews, Thomas A. Davis, and Eyma Y. Marrero-Alfonso, “Production of hydrogen from chemical hydrides via hydrolysis with steam”, AIChE Annual Meeting, Austin, TX, November 2004.
4. J. W. Weidner, P. Sivasubramanian, R. Ramasamy, C.E. Holland and F. Freire, “Electrochemical Generation of Hydrogen via Thermochemical Cycles,” AIChE, Atlanta, GA, April, 2005.
5. J. W. Weidner, P. Sivasubramanian, and F. Freire, “Electrochemical Conversion of Anhydrous HBr to Br2 for Hydrogen Production,” The Electrochemical Society, Honolulu, HI, October, 2004.
1. R. Zidan, J. A. Ritter, A. D. Ebner, J. Wang and C. E. Holland, “Hydrogen Storage Material and Process Using Graphite Additive With Metal Doped Complex Hydrides, Patent Application, US Patent Application 2005/0032641A1 (2005).
2. J. Ritter, A. D. Ebner, C. H. Holland and T. Prozorov, “Method for Improving the Performance of Metal-Doped Complex Hydrides, Provisional Patent Application, filed February 28 (2005).
Patent Applications
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Thank You!Any
Questions?
