2006 DOE Hydrogen Program

Carbide-Derived Carbons with Tunable Porosity Optimized for Hydrogen Storage

PI’s: John E. Fischer1, Yury Gogotsi2, and Taner Yildirim3

1Department of Materials Science and Eng., University of Pennsylvania, Philadelphia, PA 19104

2Department of Materials Science and Eng., Drexel UniversityPhiladelphia, PA 19104

3National Institute of Standards and Technology, Gaithersburg, MD 20899

04/19/2006 Project ID #ST21This presentation does not contain any proprietary or confidential information

OverviewOverview

Project start: Oct 2004Project end: Sept 200840% Complete

Total project funding (expected)

DOE - $ 1,440 KContractor - $ 370 K

Funding received in FY05$ 300 K

Funding for FY06 (to date)$ 225 K

Timeline

Budget

Barriers & TargetsBarriers we are addressing:

A. System Weight and VolumeF. Lack of Understanding of Hydrogen Physisorption and ChemisorptionQ. Reproducibility of Performance.

Targets: gravimetric and volumetric capacity, operability and cost.

Interactions/ collaborations:Quantachrome, IPNS (Argonne), NIST

ObjectivesObjectivesDevelop and demonstrate efficient, durable and reversible hydrogen storage in carbide-derived carbons (CDC) with tunable nanoporosity (2004-2005).

Determine the optimum pore size for hydrogen storage using experiment and theory (2005-2006).

Identify post-processing strategies and catalytic additives which maximize theperformance of CDC-based hydrogen storage materials, using experiment and theory (2006-2007).

Finalize the design of a CDC-based H2 storage material that meets 2010 DOE performance targets and commercialize it (2007-2008).

ApproachApproachDetermine which parameters are important for H2adsorption

Synthesize CDC with pore size optimized for high H2 adsorption

Increase the volume of optimally sized pores

Increase heat of adsorption for storage at or near 300K

MCn + (1/2)Cl2 MCl(gas) + nCM = metal or metalloid, C = carbide-derived carbon

2 nmSiC 2 nm

Carbide: Porosity = 0 % CDC: Porosity = 57 %

Cl2, F2 ,Br2, I2, HCl, HBr, HI, etc.( 200 - 1200oC)

Over 30 different CDC materials synthesized and evaluated

Precise control over structure and pore size distribution by varying:

• rxn temperature• precursor carbide• synthesis environment• post-treatmentsUniform pore size can

be achieved, an important requirement for studying sorption fundamentals systematically.

Free- standing monoliths can be processed for high volumetric capacity.

Economical: many precursors are cheap; simultaneous production of metal chlorides.

Unique features of CDC

0 1 2 3 4 5 6 70.0

0.1

0.2

0.3

0.4

Por

e vo

lum

e (c

c/nm

/g)

Pore size (nm)0 1 2 3 4 5 6 7

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Por

e vo

lum

e (c

c/nm

/g)

Pore size (nm)

Ti3SiC2-CDC (1200oC): orthorhombic precursor, multiple C-C distancescorrelate with broadbroad PSD

SiC-CDC (1200oC): cubic precursor, uniqueC-C distance conduces to narrownarrow PSD

Methods and Reproducibility

gas adsorption (Ar/CO2/N2/H2): specific surface area (SSA) & pore size small angle x-ray scattering (SAXS): pore size and total pore volumelocal atomic structure from neutron pdfprompt-gamma activation analysis (PGAA): impurities, doping concentrationsmodeling

0.1 1 10 100 1000

0.00

0.45

0.90

1.35

1.80

2.25

2.70

Hyd

roge

n up

take

, wt.%

Log10(Pressure), mm of Hg

Autosorb-1, Drexel University, Sample weight = 51.2 mg

Nova, Quantachrome Corporation, Sample weight = 95.8 mg

Quadrasorb, Quantachrome Corporation, Sample weight = 42 mg

H2 storage results reproduced using different instruments at Drexel, NIST, and Quantachrome, Inc.

Repeat identical syntheses give ± 5% variations in H2 capacity.

400 600 800 1000 12000.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

NLDFT

Temperature (°C)

Rad

ius

of g

yrat

ion

(nm

)

SAXSA

verage pore size (nm)

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

TiC-CDC

TiC-CDC (800 oC)

Lacking direct probes of micropores, the agreement between two indirect methods gives added confidence in the results

Progress / ResultsProgress / Results

0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6 TiC-CDC ZrC-CDC SiC-CDC B4C-CDC

.103

m

2

wt%

.gH

2 wt.%

per

uni

t SS

A,

Pore size, nm

Subnanometer pores are more efficient than large ones for H2 adsorption on carbon surfaces

Subnanometer pores are obtained from fcc TiC, ZrC.

SSA of ~2600 m2/g required for 6 wt% at 1 atm. and 77K.

Large pores decrease the volumetric capacity.

Annealing in hydrogen(open symbols) removes residual Cl2, increasing the pore volume available for storage.

HH22 uptake uptake at 1 atm, 77K

Y. Gogotsi et al. , J. Am. Chem. Soc, 127 (46): 16006-16007 (2005)

Progress / ResultsProgress / Results

[1] J. Jagiello et al., J. Phy. Chem. B, in press (2006)[2] Q. Wang et al., J. Chem. Phys. 110, 577-586 (1999)

Density of gaseous H2 in nano-pores can be higher than density of liquid H2

[1,2]

Extrapolation: CDC with 0.92 cm3/g pore volume (67% porosity) gives 4.5 wt.% H2storage if all pores are < 1 nm, even at 1 atm, where all the pores are not filled. Only ~0.6 cm3/g needed if all pores filled.

Capacity that could be obtained if H2 filled all the sub-nm pores

0.0 0.2 0.4 0.6 0.8 1.01.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Linear fit, y = 4.12x + 0.68y: gravimetric capacity, wt.% H2

x: volume of pores < 1 nm, cm3/gR = 0.91

Gra

vim

etric

cap

acity

, wt.%

H2

Volume of pores below 1 nm, cm3/g

50 55 60 65 70 75 800

2

4

6

8

10

12

14

(abs

olut

e va

lues

, val

id a

t any

con

dtio

ns)

assuming liquid H2 filling all the pores

Max

. H2 s

tora

ge p

ossi

ble,

wt.%

Carbon pore volume, %

assuming solid H2

filling all the pores

**

STRONG CORRELATION BETWEENCAPACITY AND VOLUME OF SMALL PORES

Progress / ResultsProgress / Results

0.0 0.2 0.4 0.6 0.8

1.0

1.5

2.0

2.5

3.0

Gra

vim

etric

cap

acity

, wt.%

H2

Volume of pores above 1 nm, cm3/g

Large pores are much less useful for H2 storage (they are not efficient in terms of surface coverage by H2 atoms; they also degrade volumetric capacity since adsorption is generally limited to a surface monolayer)

CDC with only modest SSA (< 1300 m2/g) but with small pores substantially outperformed others with SSA > 2300 m2/g but having wider pore size distribution (PSD).

No correlation

H2 uptake H2 uptake at 77K, 1 atm

Progress / ResultsProgress / Results

20 40 60 80 100 1205

6

7

8

9

10

11

TiC-CDC@1000oC

TiC-CDC@800oC

SWCNT

Isos

teric

Hea

t of a

dsor

ptio

n, K

J/m

ol

Volume adsorbed, cc/g

MOF [Cu3(BTC)2(H2O)3]

6.2 6.4 6.6 6.8 7.0 7.2 7.41.0

1.2

1.4

1.6

1.8

2.0

2.2

Heat of adsorption, kJ/mol

wt%

.g.1

0-3

m2

H2 w

t.% p

er B

ET

SS

A,

Small pores increase the interaction with H2 (higher heat of adsorption) and thus result in higher H2 coverage of the sorbent surface

CDC demonstrates a stronger interaction with H2 than CNT or MOF

H2 uptake H2 uptake at 1 atm

Progress / ResultsProgress / Results

0.005 0.010 0.015 0.020 0.025 0.030-5

-4

-3

-2

-1

0

1

2

3

4

5400 350 300 250 200 150 100 50

Temperature of sorption measurement, K

0.5 wt.% H2 1.0 wt.% H2 1.5 wt.% H2 2.0 wt.% H2 2.5 wt.% H2 3.0 wt.% H2 3.5 wt.% H2 Linear fit

ln(p

ress

ure)

1/(Temperature of sorption measurement), K-1

Heat of adsorption is independent of temperatureHeat of adsorption is independent of temperature

Since the heat of adsorption does not depend on temperature, values obtained from measurements at 77-87K and low pressure are valid at room temperature and elevated pressures.

Progress / ResultsProgress / Results

0 10 20 30 40 500

1

2

3

4

5

6

7

Abs

olut

e H

2 ads

orpt

ion,

wt%

Pressure, atm

40 K30 K

77 K

300 K

Gravimetric HGravimetric H22 uptake of uptake of purified TiC CDC at high pressures

0 10 20 30 40 500

1

2

3

4

5

6

Exc

ess

H2 a

dsor

ptio

n, w

t%

Pressure, atm

30 K

77 K

300 K

DOE target (2007)

CDC approach 2007 DOE target* Increased pore volume and smaller

pore size needed to boost excess H2capacity.

Small pores allow CDCs to achieve high uptake at moderate pressures

* Data assume material only

Progress / ResultsProgress / ResultsComparison with advanced activated carbonsComparison with advanced activated carbons

0 10 20 30 400.0

0.2

0.4

0.6

Exc

ess

H2 ad

sorti

on, w

t.%

Pressure, atm

TiC CDC,purified

Amoco Carbon(Air Products)

300 K At room temperature CDC demonstrates performance superior to that of activated carbons

High pressure measurements of Amoco Activated Carbon were done by VTI, Inc. 7650 West 26th Ave., Hialeah, FL 33016

Progress / ResultsProgress / Results

0

100

200

300

400

500

600

700

800

TiC-CDCpurified

TiC-CDC800oC, H2 treated

TiC-CDC800oC

TiC-CDC600oC

Vol

ume

adso

rbed

, cm

3 /g

H2 at 60 atm, 77 K Ar at 1 atm, 77 K

TiC-CDC400oC

Filling all the pores with densely packed H2is possible at high pressure (60 atm, 77K)

Larger pore volumeIs required to increase gravimetric uptake.

Progress / ResultsProgress / ResultsVolumetric HVolumetric H22 uptake of CDC at high pressureuptake of CDC at high pressure

0 10 20 30 40 500.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0.050

Exc

ess

H2 a

dsor

ptio

n, k

g/L

Pressure, atm

30 K

77 K

300 K

DOE system target (2007)Ideal volumetric capacity of

CDC approaches 2007 DOE target.

Possibility to produce CDC in monoliths with very small fraction of macropores gives it an advantage over other high SSA H2 storage media in terms of volumetric performance

Volumetric calculations assume a CDC density of 0.84 kg/L, corresponding to the carbon skeleton of cubic TiC with no macroscopic collapse (conformal reaction). Intergranular voids in powdered materials are neglected.

Future WorkFuture WorkIncrease volume of subnanometer pores to 0.9 cm3/g to achieve > 6 wt.% at 77 K

and 40 atm or less, using conventional and novel activation techniques (12/2006). Increase average heat of adsorption to improve H2 storage at temperatures above

77 K, and eventually RT. Set up theoretical models to predict doping candidates (60% done). Synthesize doped CDC and CDC containing catalyst particles for further improved

H2 uptake (03/2007).Synthesize gram quantities of selected CDCs for round-robin testing and

evaluation (09/2006) - fluidized bed reactor (2-20 g/run) designed and under test. Understand in detail, from theory and experiment, the hydrogen-carbon interaction

(09/2007).First-principles molecular dynamics simulations to guide improved storage

dynamics (09/2007).Achieve commercialization and scale-up; seek commercial partner (09/2008).

Near termNear termPush towards 300K operation by increasing the heat of adsorption. We will exploit

unique metal-hydrogen interactions in a structurally-optimized system. So far, theory and modeling of Ti dopants on nanotube and C60 surfaces (Yildirim) show that these structures are too open to avoid metal segregation. On the other hand, CDC with the right pore volume and PSD should be perfect for doping with light transition metals; pores in CDC are zero-D, so Ti can’t migrate from pore to pore.

Develop post-processing strategies to improve utilization of total pore volume for hydrogen storage. First success – annealing in H2 to clean out residual Cl2. Develop new approaches to remove amorphous carbon blocking pores and create additional small pores.

Direct measurements of gravimetric capacity on pelletized CDC powders. Find critical density at which we start losing capacity due to pore collapse, impeded diffusion and/or prohibitively slow sorption/desorption kinetics.

New theoretical approaches to treat noncrystalline systems – direct visualization of carbon collapse inside “vacated” carbide to create pore structure; correlation of pore size/shape with precursor crystal symmetry.

Reverse Monte Carlo analysis of neutron scattering, to help identify pore size and shape.

SummarySummary

Relevance: Adsorption of H2 in porous carbon was evaluated. Parameters governing adsorption investigated.

Approach: A family of novel carbon materials with controllable porosity and microstructure (CDC) synthesized.

Technical Accomplishments and Progress: Excess H2 adsorption over 4.3 wt.% and 0.034 kg (H2)/L was demonstrated in CDC @ (77K, 55 atm). Max heat of H2 adsorption up to 11 kJ/mol (with average values ~ 8 kJ/mol) demonstrated.

Proposed Future Research: Further modification of CDC porosity, microstructure and chemistry for improved H2 uptake.

Prof. John E. Fischerfischer@seas.upenn.edu

(215) 898-6924

PAPERS:1. Tailoring of Nanoscale Porosity in Carbide-Derived Carbons for Hydrogen Storage , Y. Gogotsi , 2. R.K. Dash, G. Yushin, T. Yildirim, G.

Laudisio, J.E. Fischer, J. Am. Chem. Soc. 127, 16006-16007 (2005).2. Molecular and Dissociative Adsorption of Multiple Hydrogens on Titanium-decorated C60, T. Yildirim, J. Iniguez and S. Ciraci, Phy. Rev Letters

(in press).3. Titanium Carbide-Derived Nanoporous Carbon for Energy-Related Applications, R.K. Dash, G. Yushin, G. Laudisio, J. Chmiola, J. E. Fischer, Y.

Gogotsi, Carbon, (in press).4. Titanium-Decorated Carbon Nanotubes as a Potential High-Capacity Hydrogen Storage Medium, T. Yildirim and S. Ciraci, Phy. Rev Letters 94,

175501 (2005).5. Design of Porous Carbon for Efficient Hydrogen Storage , G. Yushin, R.K. Dash, J. Jagiello, J. E. Fischer, Y. Gogotsi, Adv. Funct. Mat.

(submitted).6. Carbide-Derived Carbons: A Comparative Study of Porosity Based on Small-Angle Scattering and Adsorption Isotherms , G. Laudisio, R.K. Dash,

G. Yushin, J.P. Singer, Y. Gogotsi, J.E. Fischer, Langmuir (submitted).

PRESENTATIONS:1. Porous Carbide Derived Carbons (CDC) Optimized for Hydrogen Storage: a SAXS Study; G. Laudisio, R. K. Dash, J. P. Singer, G. Yushin, T.

Yildirim, Y. Gogotsi, J.E. Fischer, invited talk at Fall MRS Symposium, Boston 11-12/2005.2. High Hydrogen Storage in porous Carbide Derived Carbon, G. Laudisio, T. Yildirim, R. K. Dash, G. Yushin, Y. Gogotsi, J.E. Fischer, Fall MRS

Symposium, Boston 11-12/20053. Nanoporous Carbide Derived Carbon with Tunable Pore Size: Synthesis and Energy-Related Applications; Gleb Yushin, John Chmiola, Ranjan K.

Dash, Elisabeth Hoffman, Michel Barsoum, Yury Gogotsi, Giovanna Laudisio and John E. Fischer, invited lecture at the First International Conference on Carbon for Energy Storage and Environmental Protection, Orleans France, October 2-6, 2005.

4. Carbide-deived Carbons with Tailored Porosity Optimized for Hydrogen Storage , Y. Gogotsi, R.K. Dash, G. Yushin, T. Yildirim, G. Laudisio and J.E. Fischer, invited speaker, Hydrogen Storage with Novel Materials, Bad Honnef, Germany, Oct 23-27, 2005.

5. Carbide Derived Carbon Designed for Efficient Hydrogen Storage, R.K. Dash, G. Yushin, G. Laudisio, T. Yildirim, J. Jagiello, J.E. Fischer and Y. Gogotsi, Spring MRS Symposium, San Francisco 4/2006.

6. Tailored nanoscale porosity in carbide-derived carbons: optimization for high capacity hydrogen storage, invited talk at MH2006 (Metal-Hydrogen interactions), Maui (October 1-4, 2006).

Publications and PresentationsPublications and Presentations

Distribution of effortDistribution of effortUniversity of PennsylvaniaSmall angle X-ray scattering (SAXS)Transmission electron microscopy (TEM)Pore volume / pore size designPost-synthesis activation, doping

Drexel UniversityMaterial synthesisStructural characterization (Raman spectroscopy, X-ray diffraction)Porosity analysis using gas sorption techniqueLow pressure (1 atm) hydrogen storage measurements

NISTHigh pressure hydrogen storage measurementsNeutron scattering studiesSimulations using density functional tight binding (DFTB) method

Critical Assumptions and Issues• Achieve gravimetric capacity requirements. We assume this can be done

by enhancements in pore volume. Same applies to MOFs and other cryosorbers. Other solutions outside the scope of our project are to use chemical storage methods, e.g. alanates.

• Achieve volumetric requirements. We assume this can be done by optimizing PSD. MOFs suffer more from this issue than do the various carbons. Chemical storage materials will have no problem meeting volumetric requirements.

• Achieve storage at modest temperatures and pressures, with no significant thermal load on the system. We assume we can accomplish this by enhancing the heat of adsorption and optimizing PSD. MOF’s with bigger pores will always require high pressures. Chemical storage methods all require cooling to dissipate heats of decomposition when the hydrogen is released.

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