Developing and StudDeveloping and StudCatalysts for ProductCatalysts for ProductThrough Water SplittiThrough Water SplittiThrough Water SplittiThrough Water Splitti

Kevin J. Major

and

Sherine O. Obare

Department of hCH OHDepartment of Chemistry and the Nanoscale Science

Program

hCH3OH

CH2O CsepProgram

The University of North Carolina at

sep

nan

North Carolina at Charlotte

ying ying NanoscaleNanoscaletion of Hydrogen tion of Hydrogen inginginging

Pt nanoparticles

e- e-

e- e- ---

--

H2O--

h+ h+

- ---

----

-

H2-

- -

Charged Pt ti l Charged Pth+ h+

h+h+ nanoparticles Charged Pt

nanoparticlesCharge aration inaration in TiO2

noparticles

This This presentation focpresentation focof of nanoscalenanoscale catalystcatalyst

Need for New Methods of H22

Production

TiO

e-

h+

e-

Solvent

TiO2 Investigation of Charge Storage in Pt Nanoparticles

(Solvent)*Pt NP

uses uses on on developmentdevelopmentts for Hts for H22 production.production.

Synthesis and Characterization of M di PtMonodisperse Pt

Nanoparticles

Pt nanoparticles

e-e-

h+

e-

-

-- -----

- ----H2O

H2-

--

- -

H2 Production from Charged Pt

NPsh+

h+ Charged Pt nanoparticles

Toward a hydrogen eToward a hydrogen e

“Water will be the coal of Jules Verne, 1874

“150 M t d d“150 M tons per year neededJ.A. Turner. Science 2004, 3

Taken from: http://www.hydrogenhighway.ca/code/ navigate.asp?Id=220

economy.economy.

f the future.”

d f U S T t ti l ”d for U.S. Transportation alone.”05, 5686

Honda FCX Fuel Cell Car

Recent advances in hRecent advances in hresearch.research.

Taken from: http://www1.eere.energy.gov/hyd

hydrogen productionhydrogen production

drogenandfuelcells/pdfs/doe_h2_production.pdf

Current technology inCurrent technology inproduction.production.

Steam Methane Reforming (SMR

CHCHCH

CO

CH

CO

Water Electrolysisy2H

4O

2H

4O4O4O

n place for hydrogen n place for hydrogen

R)

H + H O → 3H + COH + H O → 3H + COH4(g) + H2O(g) → 3H2(g) + CO(g)

O(g) + H2O(g) → CO2(g) + H2(g)

H4(g) + H2O(g) → 3H2(g) + CO(g)

O(g) + H2O(g) → CO2(g) + H2(g)

2O(l) + 2e- → H2(g) + 2OH-(aq)

OH- O + 2H O + 4e-

2O(l) + 2e- → H2(g) + 2OH-(aq)

OH- O + 2H O + 4e-OH-(aq) → O2(g) + 2H2O(l)+ 4e-OH-(aq) → O2(g) + 2H2O(l)+ 4e-

Steam methane reforSteam methane reforwidely used method iwidely used method i

Accounts for 95% ofhydrogen productionhydrogen productionin the U.S.

Mass production would requirewould require exchange of oilimports for natural

i tgas imports.

rming is the most rming is the most n the U.S.n the U.S.

The water splitting reThe water splitting rep gp gneed for multineed for multi--electroelectro

2H2O(l) → 2H2H2O(l) → 2H

4H+ + 4e

2H O →

4H+ + 4e

2H O →2H2O → 2H2O →

Catalysts must be: Robust

Cheapp

Constructed frocomponents

eaction illustrates the eaction illustrates the on transfer catalysts.on transfer catalysts.

H2(g) + 2O2(g)H2(g) + 2O2(g)

e-→ 2H2

O + 4e-

e-→ 2H2

O + 4e-O2 + 4eO2 + 4e

om sustainable elemental s

Understanding Understanding propepropethe the nanoscalenanoscale is is cruccruc

AA Au nanorods

Au nanospheroids

100 nm100 nm

Hollow SiO2d

Pd l tnanorods nanoclusters

erties erties of of materials materials on on cialcial..

SiO NiSiO2nanowires

Ni nanowires

Ni nanoparticles

Pd bnanoparticles nanocubes

The The challenge challenge of of nannanIs controlling Is controlling the the sizesize

Lx, rxn

Meta

P l diPolydisperse Nanoparticles

oparticleoparticle synthesissynthesise e and and shapeshape..

Lz, rxn

l ions

Polydisperse Nanoparticles

The The need for methodneed for methodmonodispersemonodisperse nanopnanop

L, rxn1

M t l iMetal io

MonodisperseMonodisperse Nanoparticles

s s that that produce produce particlesparticles..

Monodisperse Nanoparticles

L, rxn2

L, rxn3ons

Monodisperse Nanoparticles

ThioethersThioethers have beenhave beeneffective stabilizing effective stabilizing liglig

n found n found to beto begandsgands..

Ethyl Sulfide

Propyl Sulfide

Butyl Sulfide

Hexyl Sulfide

Dodecyl Sulfide

Small thioether stabilSmall thioether stabilwere prepared using were prepared using

Pt(acac)2

n-dodecyl su

h l thphenyl ether

210 °C, 40 min

ized Pt nanoparticles ized Pt nanoparticles a reduction method.a reduction method.

Pt nanoparticles

ulfide

r

Size Controlled Pt Size Controlled Pt NaNaanoparticlesanoparticles..

Characterization of thCharacterization of thnanoparticles.nanoparticles.

(a)

hioether stabilized Pthioether stabilized Pt

15

20

25

ency

(b)

2.0 2.2 2.4 2.6 2.8 3.00

5

10Freq

u

2.0 2.2 2.4 2.6 2.8 3.0Diameter (nm)

u)

(200)

(111)(c)

Inte

nsity

(au (311)

(220)

30 40 50 60 70 80 90 100 2θ (degrees)

Differential Pulse Differential Pulse VoltVoltData for 2.5 nm Pt Data for 2.5 nm Pt NaNa

0 00004

0.00005

0.00003

0.00004

nt (A

)

0.00002

Cur

ren

0.00000

0.00001

-1.0 -0.8 -0.

Potential

tammetrytammetry (DPV) (DPV) anoparticlesanoparticles..

.6 -0.4 -0.2 0.0

(V vs. Ag/AgCl)

Investigation of the Investigation of the chchof Pt of Pt nanoparticlesnanoparticles..

(a) (( ) (

Light energy e-CB

h+Solvent hVB

semiconductornanoparticle

(Solvent)*

nanoparticle

harge storage ability harge storage ability

(b)( )

e-

e-

CB

h+

e-

Solvent

VB

semiconductornanoparticle

Pt Nanoparticles(Solvent)*

nanoparticle

Arguments against elArguments against elnanoparticles.nanoparticles.

- Subramanian, V.; Wolf, E. E.; Kamat, P. V. Journal of the- Wood, A.; Giersig, M.; Mulvaney, P. Journal of Physical C

lectron storage in Pt lectron storage in Pt

Ohmic contact induces i k t f f l tquick transfer of electrons

to the electrolyte.

El t t d illElectrons, once stored, will not discharge due to “electron sink” properties f Ptof Pt

e American Chemical Society 2004, 126, 4943.Chemistry B 2001, 105, 8810.

NanocrystallineNanocrystalline TiOTiO2 2 ((prepared using prepared using a Sola Sol--

((anataseanatase) was ) was --Gel Gel methodmethod..

~ 10 nm diameter particles prepared by hydrolysis of Ti(iOPr)4

Electron Electron trapping trapping andandconduction bandconduction band..

CB 1.0

VB e-e-e-

e-0.6

0.8

(a.u

.)hν

0.4

Abso

rban

ce (

CB e-e-e-e-0.2

A

VB h+h+h+h+ Solvent

Solvent*

0.0

Solvent

d d storage storage in TiOin TiO22

Electron buildup in TiO2 slide

before irradiation after 90 min irradiation

400 600 800

Wavelength (nm)

Electron transfer fromElectron transfer fromnanoparticles.nanoparticles.

Irradiated TiO slide with add

0.6

Irradiated TiO2 slide with add

0 3a.u.

)

(i.) TiO2 af(ii.) +0.1 m(iii ) +0 3 m0.3

bsor

banc

e (a (iii.) +0.3 m(iv.) +0.5 m(v.) +0.7 m

0.0

Ab

400

WavelenWavelen

m TiOm TiO22 to Pt to Pt 22

dition of Pt nanoparticle aliquotsdition of Pt nanoparticle aliquots

fter 90 min irradiationmL PtmL Pt

i.

mL PtmL PtmL Pt

ii

v.

iv.

iii.

ii.

600 800

ngth (nm)ngth (nm)

Capacitance of Pt naCapacitance of Pt nathrough reduction of mthrough reduction of m

noparticles examined noparticles examined methyl viologen.methyl viologen.

Reduction of methyl vReduction of methyl velectrons stored on Pelectrons stored on P

O1.0

TiO2 → Pt NP → Methyl V

0 6

0.8

(a.u

.) (i.) Ti(ii.) T

0.4

0.6

bsor

banc

e ( ( )

(iii.) +(iv.) +

0.2

Ab

400 5000.0

Wa elengWaveleng

viologen using viologen using Pt nanoparticles.Pt nanoparticles.

fViologen electron transfer test

O2 before irradiationTiO2 after 30 min irradiation2

+ 0.5 mL Pt NPs+ 0.5 mL Methyl Viologen

iv.

ii.

600 700 800

iii.

gth (nm)

i.

gth (nm)

Currently TiOCurrently TiO22/Pt H/Pt H22 gg22 22employ Pt doped TiOemploy Pt doped TiO

Abe, R.; Sayama, K.; Arakawa, H. Chemical PhysicsAbe, R.; Sayama, K.; Arakawa, H. Chemical Physics Letters 2003, 371, 360.

- Galinska A ; Walendziewski J Energy & Fuels 2005 19Galinska, A.; Walendziewski, J. Energy & Fuels 2005, 19- Bae, E. Y.; Choi, W. Y.; Park, J. W.; Shin, H. S.; Kim, S. B2004, 108, 14093.- Malinka, E. A.; Kamalov, G. L.; Vodzinskii, S. V.; Melnik, Photobiology a-Chemistry 1995, 90, 153.

Patsoura A ; Kondarides D I ; Verykios X E Applied C- Patsoura, A.; Kondarides, D. I.; Verykios, X. E. Applied C

generating systemsgenerating systems22..

Petkovic, L. M.; Ginosar, D. M.; Rollins, H. W.; Burch, , ; , ; , ; ,K. C.; Pinhero, P. J.; Farrell, H. H. Applied Catalysis a-General 2008, 338, 27.

9 11439, 1143.B.; Lee, J. S. Journal of Physical Chemistry B

V. I.; Zhilina, Z. I. Journal of Photochemistry and

Catalysis B Environmental 2006 64 171Catalysis B-Environmental 2006, 64, 171.

Recent work argues PRecent work argues Pprecursors to colloidaprecursors to colloida

Pt complexes act as Pt complexes act as al Pt.al Pt.

TEM images show colloidalTEM images show colloidalparticle formation after irradiationat λ ≥ 455 nm

- Du, P.; Schneider, J.; Fan, L.; Zhao, W.; Patel, U.; Castellano, F. N.; Eisenberg, R. Journal of the American Chemical Society 2008, 130, 5056.

Pt nanocapacitors usPt nanocapacitors usproduction from wateproduction from wate

Pt nanop

e- e-

e- e- ---

-

- --

---

Chargedh+ h+

h+h+CH3OH

CH O

Chargednanopar

ChargeCH2O Charge separation in

TiO2nanoparticles

sed for hydrogen sed for hydrogen er splitting.er splitting.

articles

- H2O

----

-2

H2-

-

-

d Pt 2d Pt rticles Charged Pt

nanoparticles

Pt nanocapacitors usPt nanocapacitors usproduction from wateproduction from wate

Comparison of Hydrogen Produc

1.0

u.)

0.6

0.8

d to

[0,1

] (a.

u

0.4

(nor

mal

ized

0.0

0.2

Sig

nal

Noticeable peak around 37-38 s

0 50 100 150

time pattributed to presence of hydrogen gas

sed for hydrogen sed for hydrogen er splitting.er splitting.

ction to Pure Hydrogen GC

Pure Hydrogen Production Test

0 200 250 300

(s)

In In summarysummary, , we havewe havecatalysts for hydrogecatalysts for hydroge

Thioether ligands are effallow for the formation of narrow size distribution.

Pt nanoparticles can be as needed.

The discharged electronagents toward methyl violsplitting.

e developed e developed nanoscalenanoscalen production.n production.

fective stabilizers and Pt nanoparticles with a p

charged and discharged

ns are effective reducing ogen and in water-

Acknowledgements.Acknowledgements.

Dr. X. Fan, Michigan , gHRTEM.

Dr. Panee Burckel, UXRDXRD.

University of North CaUniversity of North Ca

Th N ti l S iThe National Science

State University for y

niversity of Toledo for

arolina at Charlottearolina at Charlotte.

F d tie Foundation.