Artificial Photosynthesis:The Future Of Renewable Fuels And Chemicals

Rich Masel1, Brian Rosen2, Amin Salehi-Khojin1, Wei Zhu2

1Dioxide Materials 2UIUC

This work was supported by Dioxide Materials and the U.S. Department of Energy under grant DE-SC0004453. Any opinions, findings, and conclusions or recommendations expressed in this manuscript are those of the authors and do not necessarily reflect the views of the Department Of Energy.

• Independent R&D company founded July 2009• Focus: Nanotechnology to solve big problems

(e.g. global warming)

• Patents pending – CO2 remediation, energy conservation, indoor air quality control

• Presently one Fortune 500 licensee

About Dioxide Materials

• Introduction of artificial photosynthesis– Why it is the future of renewable fuels and chemicals

• Description of three different processes• Photochemical water splitting• Hydrogen electrolysis

• CO2 electrolysis

– Why CO2 electrolysis is preferred

• Discussion about Dioxide Material’s recent advances in CO2 electrolysis

CO2 Remediation via Artificial Photosynthesis

Today’s Agenda

Artificial Photosynthesis: An Alternate Route to Renewable Fuels and Chemicals

Biofuels

• Use photosynthesis to convert CO2 plus water and sunlight into biomass

• Use chemical or biological processes to convert biomass into fuels

Biofuels Versus Artificial Photosynthesis

Artificial Photosynthesis

• Converts sunlight and wind into electricity

• Uses electricity and chemical processes to convert CO2 and water into fuels

Biofuels Versus Artificial Photosynthesis

Biofuels

• Technology works today• Economically feasible

– Tax subsidy

But

• Competes with food supply• Energy inefficient

– Corn only 1% efficient in converting sunlight into biomass – 0.04% to kernels

Artificial Photosynthesis

• Technology works today• No competition with food supply• Potential for high energy efficiency

But

• Not economically feasible today• Energy efficiency unproven

Process Comparison

Potential Energy Efficiencies

Efficiencies Biofuels Artificial Photosynthesis

Solar collection 0.2-2% (corn 1% to cellulose)

10-35% (solar cells)

Transportation

25-75% of energy used in planting, fertilizing,

harvesting, and transporting crops

Electricity loses5% of energy during transmission across

country

Present process 5% <1%

Potential process 36% 36%

Potential overall 0.3% 8%

Artificial Photosynthesis is the Future of Renewable Fuels and Chemicals

• At maximum efficiency (converting cellulose) biotechnology would need 3,000,000 km2 of arable land to meet U.S. fuels and chemicals needs– Not enough unused arable land in U.S. to meet needs

• Solar collectors need 200,000 km2 – Desert land & offshore wind sufficient

• Technology exists to produce hydrocarbons

There is no other choice

There are Three Types of Artificial Photosynthesis Processes

• Photochemical water splitting3H2O +h →3H2 + 1.5 O2

3H2 + CO2 → (CH2)x

• Water electrolysis3H2O →3H2 + 1.5 O2

3H2 + CO2 → (CH2)x +2H2O

• CO2 electrolysis2CO2 →2CO + O2

2CO + H2O → (CH2)x + CO2

Artificial Photosynthesis Processes

Photochemical Water SplittingMay Never Be Practical

• At 10% energy efficiency, 100,000 bbl/day plant covers 670 km2

– About the size of NYC

• 3,000 mi of glass pipe– containing a stoichiometric

mixture of H2 and O2

2H2O +h →2H2 + O2

Explosion Hazard?

Electrolysis is a Better Alternative

4-6 GW

95% efficient

100,000 bbl/day of fuel

Electrolyzer5-10x chlor-alkalai

Simplest Process:Hydrogen Electrolysis + Fischer Tropsch

3H2O → 3H2 + 1.5 O2 Reverse water gas shift:H2 + CO2 → H2O + CO

Fischer Tropsch2H2 + CO → H2O + (CH2)X

Electrolyzer

Hydrogen Electrolysis Process Economics

+NERL Report: J. Levene, B. Kroposki, and G. Sverdrup Wind Energy andProduction of Hydrogen and Electricity — Opportunities for Renewable Hydrogen

Assumption• Wind-generated electricity • Net hydrogen cost of

$4.03/kg today, droppingto $2.33/kg in 2030+

$2.00 $2.50 $3.00 $3.50 $4.00 $4.50 $5.00

2010 2020 2030Hyd

roge

n Co

st, $

/gal

fuel

CO2 Electrolysis is PotentiallyMore Energy Efficient

Water gas shift:2H2O + 2CO → 2H2 + 2CO2

Fischer Tropsch2H2 + CO → H2O + (CH2)X

Combined chemistry:H2O + 2CO → (CH2)X + CO2

2CO2 → 2CO + 1.5 O2

Electrolyzer

How CO2 Electrolysis Works

CO2 + 2e- + H2O → CO + 2 OH-

4 OH- → O2 + H2O + 4e-

CO2 + e- → (CO2)-

(CO2)- + 2H+ + e- → CO + H2O

CO2 + e- → (CO2)-

(CO2-) + H2O + e- → CO + 2OH-

Alkaline conditionsAcidic conditions

electrolyte

anode

cathode

electrolyte

anode

cathode

Ideal Thermodynamic Comparison

0

200

400

600

800

1000

Ener

gy K

j/m

ole

CH2

Reaction Progress

water electrolysis CO₂ Combined cycle

Electrolysis Water gas shift

30% electricity waste

(Title TBD by R. Masel)

0

500

1000

1500

2000En

ergy

Kj/

mol

e CH

2

Reaction Progress

CO₂ Combined cycle Actual Combined

Electrolysis

Water gas shift

Waste 70% of electricity

Ideal

Reaction Progress

Actual

CO2 Electrolysis Also Results in Issue Cathode Overpotential

-1.8-1.6-1.4-1.2

-1-0.8-0.6-0.4-0.2

00.2

Pb Cd Tl Bi In Zn Hg Sn Cu Ag Ga Pd Au

Volta

ge v

s SH

E

Equilibrium

Actual

Wastedenergy

High Energy in (CO2)- Intermediate Production Causes Overpotential

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Reaction Progress

(CO2)-

Free

Ene

rgy

Dioxide Material’s Patent PendingApproach to CO2 Electrolysis Solves

the Overpotential Problem

Dioxide Material’s Approach

Using two catalysts…• Ionic liquid or amine

to catalyze formation of (CO2)-

• Transition metal to catalyze the conversion of (CO2)- to products

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Reaction Progress

(CO2)-

Fre

e E

nerg

yEMIM-(CO2)-

…results in lower net energy loss.

SFG To Verify (CO2)- Formationat Low Overpotentials

Brian A. Rosen, Amin Salehi-Khojin, Prabuddha Mukherjee, Björn Braunschweig, John L. Haan, W. Zhu, Dana D. Dlott, Richard I. Masel, science under review

See Paper 295B12:55 Room 150F

2200 2300 2400 2500

-1.24 Vvs. SHE

-1.04

-0.84

-0.64

-0.44

-0.24

+0.04

+0.24

SF

G in

ten

sity

(a

rb. u

.)

wavenumber / cm-1

Emim-(CO2)-

CO Formation Also Observedat Very Low Potentials

1800 2000 2200 2400

S

FG

inte

nsi

ty (

arb

. u.)

wavenumber / cm-1

-0.25 V

-0.35 V

-0.45 V

-0.55 Vvs. SHE

Brian A. Rosen, Amin Salehi-Khojin, Prabuddha Mukherjee, Björn Braunschweig, John L. Haan, W. Zhu, Dana D. Dlott,Richard I. Masel, science under review

Steady CO Production Observed at 110°C

CO2 + 2e- + H2O → CO + 2 OH-

4 OH- → O2 + H2O + 4e-

Electrolyte with 100 mMol water

Pt anode

Pt cathode

PCO₂ = 1 AtmGC Analysis

Observe CO product with GCTurnover rate = xx/sec at 0.6 V (SHE)Ran for yy hours with no degradation

Dioxide Material’s TechnologySuppresses H2 Formation

CO2 + 2H+ + 2e- → CO + H2O2H+ + 2e- → H2

2H2O → O2 + 4H+ + 4e-

Paper 182EMonday, 4pmRoom 151F

electrolyte

anode

cathode

The Future of Dioxide Material’sPatent Pending Process

• CO2 electrolysis demonstrated at low overpotential– Requires two catalysts

• Lifetime studies needed• Need cell designs to suppress crossover

– (CO2)- concentration high – can cross over to anode

Electrolysis Technology Development Still Needed

• Better cell design to raise efficiency from 70% to 83%• Manufacturing expertise to lower capital cost of

electrolyzer from $740/kW to $300/kW• Government investment

– U.S.D.O.E. spends $500m/yr. on biotech, $50m/yr. on solar water splitting, but has no specific program for electrolyzers. (Dioxide Materials is funded through SBIR.)

Summary

• Artificial photosynthesis is the future of renewable fuels and chemicals– Only alternative that can produce enough renewable

hydrocarbons to meet the U.S. needs

• Two routes make sense– Hydrogen electrolysis + reverse water-gas shift

– CO2 electrolysis

• Dioxide Materials has made a breakthrough in CO2 electrolysis

The People Who Did The WorkCO2 Catalysis, Electrochemistry

CO2 SFG

Prof Dana Dlott

Brian Rosen Wei Zhu

Björn BraunschweigPrabuddha MukherjeeJohn Haan

Amin Salehi-Khojin

Questions

NYC Sized Solar Collector Is Needed

Assume 100,000 barrels/day -1% of US demand5 kw-hr/m2/day solar flux, 5% efficiency solar to gasoline

2km 670m10

kmJ103.6

hrkw

hr)(5%)(5kwdaym

bblJ106

daybbl10

26

2

6

295

770 km2 of land

Also Need to Examine Selectivity

CO2 + 2H+ + 2e- → CO + H2O2H+ + 2e- → H2

2H2O → O2 + 4H+ + 4e-

electrolyte

anode

cathode