2011 mcfarland iee ucsb solar chemical conversion

8/3/2019 2011 McFarland IEE UCSB Solar Chemical Conversion

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Solar Production of Fuels and Chemicals;is there a cost-effective path forward?

1

Bi Picture

Outline

Solar Energy Conversion: What Works, What Doesnt , and Why

Strategies and Tactics: Potentially Cost-Effective ArtificialPhotosynthetic Processes

Im roved Li ht Absorbers and Electrocatal sts

2

Beyond Water Splitting


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Radiation From Thermonuclear Reactions Has BeenAnd Always Will Be The Most Important Source

Of Energy For The Earth and Human Beings

Societal prosperity through the 19thcentury was powered

by renewable biomass.


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5


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Mtoe/year

20117 billion~ 17 TW

Prosperity + Population Demand

19122 billion people

~ 1 TW

Societal prosperity through the 19thcentury was powered by renewable biomass. Global prosperity in the 20th Century was possible due to the availability of large quantities

of inexpensive fossil hydrocarbon resources.

Global prosperity in the 22ndcentury will depend on availability of enormous quantities ofsustainable energy resources (32+TW) and/or significant unprecedented population control.

The 21st Century Better Figure Out How to Get Us There.

Low cost, solar derived, hydrocarbonfuels have provided unprecedentedopportunities for global egalitarian

prosperity.

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$ 63,000,000,000,000~ $120/GJ

512,000,000,000 GigaJoules

9

Yes, there is a limit on how much we can spend

Society can not spend (for long) more on energy

than the value createdConservation of Money

World GDP 2010 ~ $63 Trillion/y(US/Ger/China/India 14/3.6/6/1.5)

~

World Gross Domestic Product (GDP)

(US/Ger/China/India 3.5/0.6/3.5/0.9)

Absolute Spending Limit (GDP/Energy Use)U.S. $120/GJ Germany $190/GJChina $50/GJ India $50/GJ


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Fraction of U.S. GDP

Max Total Spending on Energy ~ 10-15% of GDP< $5 -15/GJ: the lower the better.

spen on energy

11

Raising the price of energy meansthe money must come from somewhere else.

Decreased Prosperity.

During times of relative economic stability and increasing

world prosperity food and fuel are inexpensive< 10-15% GDP

Food ~ $5 - 15/GJ and Fuel ~ $2 - 15/GJ

Corn $2.00 /bushel $7.90 /GJ

Rice $2.00 /cwt $4.40 /GJ

Oil $85.00 /barrel $13.94 /GJ

Coal $50.00 /ton $1.70 /GJ

Natural

4.00 MMBTU . . .

Gasoline $2.50 /Gallon $20.00 /GJ

Electricity $0.05 /kWhr $14.00 /GJ


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Bad Things Happen WhenFood and/or fuel > $15/GJ

2008Oil @ $150/bbl ~ $24/GJea us e ~

Electricity @ $0.15/kW-hr = $30/GJ

Cause or Effect ?

Here we go again?

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Where do most people (including scientists) think the money

will come from for new sources of sustainable energy?

15

Sustainable = Environmental and Economical

(non-toxic, renewable) (< $5 - 15/GJ)

n1

Annual Net Revenue($)Total Capital($)

(1 discount rate)

nn

year

Production Cost

nProduct Price1

n1

Total Capital($) 1Product Price(1- )

System Output(GJ/y) (1 discount rate)

1~ 8 - 3 for DR~ 10 - 30%, n~10 years

(1 discount rate)

Total Capit

n

year

n

year

Production Cost

Product Price

al($)~ 15($/GJ) (1- ) * 5 ~ 60($ / / )

System Output(GJ/y) y GJ y

16

Energy Production Cost

Energy Product PriceTotal Capital($/Watt) 1.8 *(1 - )


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Science and Engineering have provided society with low costprocesses for economically sustainable energy production.

$0.25 - 1/Watt

$1-3/Watt

Solar Wind Electricity

EnvironmentallyAnd EconomicallySustainably ?

$0.5-1/Watt

2050

~ 30 TWfrom where?

Solar Conversion Processes

200 W/m2 ~ 1 mMoles photons/m2s

Inputs Outputs

18

Output Value - Input Costs - CapX - OpX > 0


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How to use solar radiation ?

Inputs Outputs

19

Utilization of electrochemical potential from electronic excitations (e-,h+) EMF Photovoltaics (e-,h+) EMF, EChem Photosynthesis (e-,h+) EMF, ThermalWind, Hydro, Solar-Thermal

Earth as a conversion system (e-,h+) EMF, Thermal Wind, Hydro (e-,h+) EMF, EChem Photosynthesis

~ 1% Wind

~ 10% Hydro

20

, omass, t e


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Cost-Effective Solar Energy Conversion: Wind and Hydro-Power

21

Why Solar-to-Chemical Photosynthesis Works

m

=0.1%

0.2 J/s-m2

~ - ~ -

22

0.0063 GJ/y-m2

~ $ 0.1/m2 year Revenue

Because, it costs farmers less than $0.1/m2-year to grow biomass,AND only because they dont need to produce very much of it.

~ 200 Watts/person


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Why Solar-to-Electricity Does Not Work

m

~ 10%

20 J/s-m2Electricity Value ~ $15/GJ

23

0.63 GJ/y-m2

~ $ 10/y-m2 Revenue

A modern cell system installed @ $5/Wpeak

Capital Cost ~ $500/m2

Why $500/m2

Its a wild world out there

$$$


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price ($)

per m2

To be cost effective on capital alone, a solar convertermust cost less than ~ $40/m2 for ~10% and less than ~ $400/m2@ =100%

no or an

paint (3 mils) 0.6

plastic (6 mils PE) 1.1

plywood 6.5

astro-turf 8.2

sod lawn 8.6

vinyl flooring 10.8

1" concrete 13.5+ lots of

land.roof tile 64.6

Asphalt road 172.2

Si Solar Cell($5/W) 500.0

Home Construction 1500.0

Only VERY Inexpensive Systems

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2009

27

Google: Grid Parity?

28https://docs.google.com/present/view?id=dfhw7d9z_0gtk9bsgc&pli=1


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Wealthy nations (with low GDP growth) tolerate economicallyunsustainable renewables such as solar cells because

they are balanced by relatively low cost fossil/nuclear/wind

China ~ 3.5 TW

U.S. ~ 3.5 TW Germany~ 0.6 TW

31

Chemical sciences and engineering must create optionsfor massive quantities of sustainable sources

of energy that are affordable by all people

Cost reductions over the last decade

32

are arge y ue to use o ncreas ngnumbers of low wage workers notimproved technology. The majorityof the costs are paid from taxpayersubsidies.


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33

~1780

~1880 Adams&Day, Fritts

Se Solar Cells 1-2% efficiency)

More than

100 years of

Development

No Significant

Cost-Effective

Applications


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C*(e-,h+)

e-

h+

A

D

e-

h+

A-

What about Solar-to-Chemical ? chemical potential

CC

D+

2e- + 2H+ +xCO2 CxH2OzH2O + 2h

+ O2 + 2H

+

ReducingPotential

35

Growth Driven By Unsustainable Economics

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Growth Driven By Unsustainable Economics

Biodiesel

37

Can Man Beat Nature ? Artificial Photosynthesis

G. Ciamician, Science 1912


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Solar Energy, Volume 2, Issue 2, April1958

Semiconductor Photoelectrodes

E

RED

Photocathode

h+

+ +

OX

-

Photoanode

+

h

RED

OX

E

n-type SC


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SuspendedPVplatelets 1981

Hydrogen

Platelets

N-type semiconductorp-typesemiconductor

Ohmiccontact

Platelet

100 + Years of

Photoelectrocatalysis (PEC)Science has provided efficient systemsbut not cost-effective energy production

TiO2 PEC

42

PEC AirPurifier

Mosquito Trap


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Going Forward: Strategies and TacticsHow to do the right thing and get others to pay for it.

Options:1) Scare them into it.2) Keep making promises that are impossible

to keep.3) Create options that, if tough problems are

creatively solved, might ultimately proveeconomically sustainable.

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Is there a cost-effective solarPEC Process that can

make use of the material system?

Find and understand anefficient PEC material system


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ConceptualEngineeringProcessModels

Photoelectrodes = PV ($$) + electrolyzer($$)

Un-biasedPhotoelectrode(s)

Chemically biasedPhotoelectrode(s)

Electrically biasedPhotoelectrode(s)

BottomUpvsTopDown

donotunderestimatetheengineeringDesign a conceptual cost-effective

Solar Chemical Process

Can a material system befound that meets the

minimum requirements ?


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Artificial Photosynthesis

47

~ 10%~ 0.1 %~ 0.1 %

ConceptualEngineeringProcessModels

Photoelectrodes = PV ($$) + electrolyzer($$)

Un-biasedPhotoelectrode(s)

Chemically biasedPhotoelectrode(s)

Electrically biasedPhotoelectrode(s)

-+A

-D

Split Z-SchemeSlurry Photoreactor

Single TankSlurry Photoreactor


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Today,thereisonlyoneknownsystemforsolarfuels

(hydrogen)whichmight makeeconomicsense.

ASSUMES that a stable, =10% slurry material exists

Only slurry-based

James B, Baum G, Perez J, B.K. Technoeconomic Analysis of Photoelectrochemical(PEC) Hydrogen Production. Analysis22201, (2009).

systems might meet basiceconomic targets. $6/GJ

h

Can we do better than Nature?

What structures should we make and calculate

D-

D

A

A-

e-

e-

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Hybrid PEC NanoreactorsLow cost inorganic semiconductor based heterostructures

Our Strategy

Theory New/improved low cost semiconductors Understanding of excitation/separation/

h+

e-

h A-AD-

- , ,Interface charge transfer. RecombinationElectrocatalysis

Synthesis/Experiment

New/improved low cost, high-quality semiconductors Heterostructures Diffusion barrier/encapsulation

AA-Zn2+ Zno -0.76

-0.26V3+ V2+

Approach

h

Maximize Stored SolarChemical Potential

D-

DA

A-

2I-1I2 0.54

D- D

(CnHm)OH(CnHm)O 0.6

2H+ H2 0.00

AgCl Cl-+Ago

0.34

0.22

Cu2+ Cuo

CO2 CH4 0.17

1) Identify cost effective optimal solar absorbingsemiconductor Egap~ 1eV systems with IQE >90%.

h+

e-

H2O2H++1/2O2 1.23

2Br-1Br2 1.07

Fe2+Fe3+ 0.77

2Cl-1Cl2 1.36

2) Select and match best practical redox systems thatcould provide stored energy G ~ 0.9*Egap

3) Maximize selective kinetics (minimize back reaction)

4) Determine means for stabilizing the material in theredox system


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HighThroughputMethodology

Al2O33000

Al2O31500

V800

V1600

SnO24800

4000

1000

La2O3

4000

1000

Y2O3

4000

1000

MgO

4000

1000

SrCO3

Sample: 826962

Theory Guided

0530

0260

0240

0250Eu2O3 Tb4O7 Tm2O3 CeO2

Science279, 837-839 (1998)

Library Design:Diversity in CompositionDiversity in Synthesis

Rapid Synthesis and Processing:Electrochemical DepositionPVD, Ink Jet, Solgel,Parallel vs Rapid SerialSmall vs Large Element Size

High-Throughput Screening:Optical, Chemo-opticalPhotoelectrochemicalGC-MS

Start with a known reasonable host Try to make it better

Make efficient materialmore stable

Bak et. al., Int. J. Hydrogen Energy,vol 27 (2002) 991-1022

ZnnXmO

45

WnXmOp

H2O/H2

O2/H2O

1.23 eV

Cu2O TiO2 Electrolyte

Eabs(eV)

- 4

- 5

- 6

- 7

- 8

- 3

ENHE(eV)

0

+1

+2

+3

- 1

- 2

2.0 eV

3.0 eV

0.30

Cu2O/XOn

0 20 40 60 80 1000

1

2

3

4

1520253035

Photocurrent(A/cm

2)

[Mo]

1V bias

zero bias

J. Combi. Chem. 4(6), 573-578, 2002

4 6 8 10 120.10

0.15

0.20

0.25

Photocurrent(mA/cm

2)

pH

J. Comb. Chem., 7, 264-271, (2005)


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Doped: ZnO

TheScienceofSynthesis

55

J. Comb. Chem., 7, 264-271, (2005)

WO3

15202530354045

rent(A/cm

2) 1V bias

WnXmOp

MoO3

MoO3

W0 2Mo0 8O3

56

0 20 40 60 80 1000

1

2

3

Photocur

[Mo]

zero bias

J. Combi. Chem. 4(6), 573-578, 20025 00 5 50 6 00 6 50 7 00 7 50 8 00 8 50 9 00 9 50 1 00 0 10 50 1 10 0

W0.2Mo0.8O3

W0.3

Mo0.7

O3

W0.5

Mo0.5

O3

W0.7

Mo0.3

O3

W0.8

Mo0.2

O3

WO3

Intensity(a.u.)

Raman Shift (cm-1)

20 22 24 26 28 30

. .

W0.5Mo0.5O3

W0.8Mo0.2O3

WO3

Intensity(a.u.)

2


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In spite of decades of research, there is no evidence thatwide gap oxides (TiO2, WO3, ZnO, ) can be modified to serveas efficient solar absorbing hosts. Fe ? Cu ?

Fe2O3

n-Type Indirect Bandgap 2 - 2.2 eV

40% solar spectrum absorbed

Globally scalable

Abundant, inexpensive

Non-toxic

Photo-stable against corrosion

Mott Insulator (Poor carrier transport )

Anisotropic conductivity Low electrocatalytic activity

TheoryGuidedExperimentationUndoped Fe3+

Fe2O3 Pt4+ doped Cr+3 doped Al+3 doped

58

Flat Conduction band large effective mass, poor conductivity.1) Majority Carrier Donor Concentration (traditional doping)2) Create Impurity bands which have smaller mass3) Break C-T Mott Insulator, spin forbidden electron transport

U=5.7eV12Fe+18O


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CharacterizationofsubstitutedFe2O3

Bg=2.1 eV

J. Phys Chem C. 20(12),3803, (2008)

Chem. Mater., 20, 38033805, (2008)

Energy Env. Sci. 4,1020, (2011) 1%Ti

Optical properties show little change with dopants Higher valence dopants (n-dope) helps Isovalant substitutions with large cation size differences (strain) helps

De l a f o ss i t e s (Cu M X 2)

Cu+

Theoretical bandgap

Direct: 3.0 eV

Indirect: 2.1 eV

Experimental bandgap: 1.3 eV

2r

In general, poor efficiency.


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Phosphides(start with an efficient material and make it more stable)

Easytomake(fromlibrariesofoxides) MxOy +H3PO4 ; H2 at900C

.

Easy to break Zn3P2 + 6H2O 2PH3 + 3Zn(OH)2

Strategy -> keep

H+

Na6 [HxMyOz] + NH4HPO4MPOx + NH4OH +NaOH +H2O

H2 at 900 C

FeP InP Zn3P2 NixPy WP MoP

t em sa e

Sulfides (SnS)

ElectrodepositedFilm powder


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Identification of efficient, stable, cost effective solarabsorbing materials remains

the #1 challenge for solar energy PEC

Work to date with all oxides has been discouraging.

- ,enough. The common wide gap oxide semiconductors (TiO2, ZnO, WO3)will not work as absorbers for solar fuel applications.

- Iron oxides are intrinsically poor candidates for solar PEC applications

TiO2

63

and in spite of attempts to improve their properties they remain far tooinefficient by 10-100x.

Sulfides and Phosphides Deserve More Attention

Dont forget Si !

Silicon

Fe2O3 Last oxide hope CuxO

TheoryGuidedIdentificationofActive,Stable,

andSelective

Electrocatalysts

h+

e-

h D

D-2H+

HIn situ membrane


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65

Pt-Au Alloy Nanoparticles for ORR

Slope ~ ne

66


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Co/AuFe/Ni

Bimetallic OER Electrocataysts

CoAu

67

Electrochem.Com. 11 (2009) 11501153

u

Choice of the electrocatalyst assumes you know the reaction you want.

2H+ H2AA-

What is the best form of the chemical potential product?

H2 fast, separable, easily reacted (H2+ CO2CH4)

1) High efficiency, cost-effective absorbers, Egap~ 1eV.2) Identify stable redox chemistry that can be integrated into a major

chemical cycle.

10

12

14

16

18

Zero BiasNaOHGlycerolErythritolXylitol

(%)

D- D

(CnHm)OH(CnHm)O2 electrodes 1 sun

Ti Doped Fe2O3

H2S2H++ S

2HBr2H++ Br2

Avoid zero value products

350 400 450 500 550 600

0

2

4

6

8IPCE

Wavelength (nm)

H2O2H++1/2 O2

2HCl2H++ Cl2

Get over water splitting!


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The formation of adsorbed OOH is limitingand only at high electrode potential is thisstep downhill in free energy. The processtakes place on an oxidized surface.Ox en evolution should start at E>1.8 V

69

Functional Nanoparticulate Heterostructures

Fe2O3@ZrO2

7010 nm


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Hybrid PEC NanoreactorsLow cost inorganic semiconductor based

heterostructures

Al2O3

Absorber

Ag

(OhmicContact)

h+

e

Oxidizing

reactant

Reduced

product

AuorPt(Schottkycontact)

Reducing

agent

Oxidized

product

Mubeen J. HussainiFrancesca Toma

Martin MoscovitsGalen Stucky

NiO

AAb

Electrodeposited Heterojunction in Porous Alumina

CdSe

Au

TiO2

l2O3

sorber

Mubeen J. HussainiFrancesca TomaMartin MoscovitsGalen Stucky


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Large Scale, Cost Effective Processes Are Typically Integrated

Large Scale, Cost Effective Processes Are Typically Integrated

Process Alternative: CnHmOz H2+ CO2

(CnHm)OH + h+(CnHm)O + H

+

2e- + 2H+ H2

2

Biomass orWastewater

CO2

X-ols

CatalystRegeneration

Reactor SeparationTreatmentSeparation

~ 1 kg/person/day organic waste (~ 1 TW )


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2e- + 2H+ H22Br-1Br2

Large Scale, Cost Effective Processes Are Typically IntegratedExample Process Alternative: 2HBr H2+ Br2

Biomass

Regeneration

O2 + HBr Br2 + H2O

Water Air

HBrBr2

Activation

CH4 + Br2 CH3-Br + HBr

Coupling

CH3-Br Gasoline + HBrBioMethane Gasoline


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77

Net Reaction: 8CH4 + (16/ C8H16 + 8H2 (Ideal)

Summary

Todaytherearenosignificant,costeffective,manmadesolarconversionprocessesbecausenoefficient,stable,scalable,andcosteffectiveabsorbingmaterialsystemisknown.

Recentadvancesintheory,complexsurfaces,andsynthesisofnovelmaterialsmayhavesignificantimpactifdirectedwisely.

Watersplittingmayormaynoteverbecosteffective,buttherearepotentiallymanyothersolartochemicalconversionsthatmightbemorecosteffectiveandultimatelymoreusefultomankind. Thesystemmatters,manycanneverwork.

Fundamentallyproductionofchemicalfuelsfromsolarenergyatlessthan$15/GJispossible,practicallyitisveryverydifficult.

Thinkoutsidetheboxorwewillnotsucceed


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an ou

Collaborators: Alan Kleiman, Yong-Sheng Hu, PengZhang, Nirala Singh, Galen Stucky, Eric McFarland

2011 mcfarland iee ucsb solar chemical conversion

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