Artificial photosynthesis uses electricity from renewable sources like sunlight and wind to convert carbon dioxide and water into renewable fuels and chemicals. Three processes for artificial photosynthesis are discussed: photochemical water splitting, hydrogen electrolysis, and CO2 electrolysis. CO2 electrolysis is identified as the preferred method as it has the potential to be more energy efficient. However, challenges with cathode overpotential during CO2 electrolysis must still be addressed. Dioxide Materials' approach uses two catalysts - an ionic liquid or amine and a transition metal - which is shown to lower energy losses during CO2 electrolysis by facilitating the intermediate formation of (CO2)-.

1. 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.

2. About Dioxide Materials
• 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

3. Today’s Agenda
CO2 Remediation via Artificial Photosynthesis
• 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

4. Artificial Photosynthesis: An Alternate
Route to Renewable Fuels and Chemicals

5. Biofuels Versus Artificial Photosynthesis
Biofuels
• Use photosynthesis to convert
CO2 plus water and sunlight
into biomass
• Use chemical or biological
processes to convert biomass
into fuels

6. Biofuels Versus Artificial Photosynthesis
Artificial Photosynthesis
• Converts sunlight and wind
into electricity
• Uses electricity and chemical
processes to convert CO2
and water into fuels

7. Process Comparison
Biofuels Artificial Photosynthesis
• Technology works today • Technology works today
• Economically feasible • No competition with food supply
– Tax subsidy • Potential for high energy efficiency
But
But
• Competes with food supply
• Energy inefficient • Not economically feasible today
– Corn only 1% efficient in • Energy efficiency unproven
converting sunlight into
biomass – 0.04% to kernels

8. Potential Energy Efficiencies
Artificial
Efficiencies Biofuels
Photosynthesis
0.2-2% 10-35%
Solar collection
(corn 1% to cellulose) (solar cells)
25-75% of energy used Electricity loses
in planting, fertilizing, 5%of energy during
Transportation
harvesting, and transmission across
transporting crops country
Present process 5% <1%
Potential process 36% 36%
Potential overall 0.3% 8%

9. Artificial Photosynthesis is the Future of
Renewable Fuels and Chemicals
There is no other choice
• 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

10. There are Three Types of Artificial
Photosynthesis Processes

11. Artificial Photosynthesis Processes
• Photochemical water splitting
3H2O +h →3H2 + 1.5 O2
3H2 + CO2→ (CH2)x
• Water electrolysis
3H2O →3H2 + 1.5 O2
3H2 + CO2→ (CH2)x +2H2O
• CO2 electrolysis
2CO2→2CO + O2
2CO + H2O → (CH2)x + CO2

12. Photochemical Water Splitting
May Never Be Practical
• At 10% energy
2H2O +h →2H2 + O2
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
Explosion Hazard?

13. Electrolysis is a Better Alternative
4-6 GW Electrolyzer
5-10x chlor-alkalai
95% efficient
100,000 bbl/
day of fuel

14. Simplest Process:
Hydrogen Electrolysis + Fischer Tropsch
Electrolyzer
3H2O → 3H2 + 1.5 O2 Reverse water gas shift:
H2 + CO2→ H2O + CO
Fischer Tropsch
2H2 + CO → H2O + (CH2)X

15. Hydrogen Electrolysis Process Economics
Assumption $5.00
• Wind-generated electricity $4.50
Hydrogen Cost, $/gal fuel
• Net hydrogen cost of $4.00
$4.03/kg today, dropping $3.50
to $2.33/kg in 2030+ $3.00
$2.50
$2.00
2010 2020 2030
+NERL Report: J. Levene, B. Kroposki, and G. Sverdrup Wind Energy and
Production of Hydrogen and Electricity — Opportunities for Renewable Hydrogen

16. CO2 Electrolysis is Potentially
More Energy Efficient
Electrolyzer
2CO2→ 2CO + 1.5 O2 Water gas shift:
2H2O + 2CO → 2H2 + 2CO2
Fischer Tropsch
2H2 + CO → H2O + (CH2)X
Combined chemistry:
H2O + 2CO → (CH2)X + CO2

17. How CO2 Electrolysis Works
Acidic conditions Alkaline conditions
CO2 + e- → (CO2)-
(CO2)- + 2H+ + e- → CO + H2O CO2 + 2e- + H2O → CO + 2 OH-
cathode cathode
electrolyte electrolyte
anode anode
CO2 + e- → (CO2)- 4 OH- → O2 + H2O + 4e-
(CO2-) + H2O + e- → CO + 2OH-

18. Ideal Thermodynamic Comparison
1000
30% electricity
800 waste
Energy Kj/mole CH2
600
400
Electrolysis Water gas shift
200
water electrolysis CO₂ Combined cycle
0
Reaction Progress

19. (Title TBD by R. Masel)
2000
Water
gas shift
1500
Energy Kj/mole CH2
Waste 70% of
electricity
1000 Electrolysis
500
CO₂ Combined cycle
Ideal Actual Combined
Actual
0
Reaction Progress
Reaction Progress

20. CO2 Electrolysis Also Results in Issue
Cathode Overpotential
-1.8
-1.6
-1.4
-1.2 Actual
Voltage vs SHE
-1
-0.8 Wasted
-0.6
energy
-0.4
Equilibrium
-0.2
0 Pb Cd Tl Bi In Zn Hg Sn Cu Ag Ga Pd Au
0.2

21. High Energy in (CO2)- Intermediate
Production Causes Overpotential
1.2
1
(CO2)-
Free Energy 0.8
0.6
0.4
0.2
0
-0.2
Reaction Progress

22. Dioxide Material’s Patent Pending
Approach to CO2 Electrolysis Solves
the Overpotential Problem

23. Dioxide Material’s Approach
Using two catalysts… …results in lower
• Ionic liquid or amine net energy loss.
to catalyze formation 1.2
of (CO2)- 1 (CO2)-
• Transition metal to
Free Energy
0.8
catalyze the 0.6
conversion of (CO2)- 0.4
to products
0.2
0 EMIM-(CO2)-
-0.2
Reaction Progress

24. SFG To Verify (CO2)- Formation
at Low Overpotentials
Emim-(CO2)-
-1.24 V
vs. SHE
-1.04
SFG intensity (arb. u.)
Brian A. Rosen, Amin Salehi-
-0.84
Khojin, PrabuddhaMukherjee, BjörnBraunschweig, Joh
-0.64
n L. Haan, W. Zhu, Dana D. Dlott, Richard I.
Masel, science under review
-0.44
-0.24 See Paper 295B
+0.04
12:55 Room 150F
+0.24
2200 2300 2400 2500
-1
wavenumber / cm

25. CO Formation Also Observed
at Very Low Potentials
-0.55 V
vs. SHE
SFG intensity (arb. u.)
-0.45 V
Brian A. Rosen, Amin Salehi-
Khojin, PrabuddhaMukherjee, BjörnBraunsch
weig, John L. Haan, W. Zhu, Dana D. Dlott,
-0.35 V Richard I. Masel, science under review
-0.25 V
1800 2000 2200 2400
-1
wavenumber / cm

26. Steady CO Production Observed at 110 C
GC Analysis
PCO₂ = 1 Atm
CO2 + 2e- + H2O → CO + 2 OH-
Pt cathode
Electrolyte with 100 mMol water
Pt anode
4 OH- → O2 + H2O + 4e-
Observe CO product with GC
Turnover rate = xx/sec at 0.6 V (SHE)
Ran for yy hours with no degradation

27. Dioxide Material’s Technology
Suppresses H2 Formation
CO2 + 2H+ + 2e- → CO + H2O
2H+ + 2e- → H2
cathode
Paper 182E
electrolyte Monday, 4pm
anode Room 151F
2H2O → O2 + 4H+ + 4e-

28. The Future of Dioxide Material’s
Patent 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

29. 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.)

30. 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

31. The People Who Did The Work
CO2 Catalysis, Electrochemistry
Brian Rosen Amin Salehi-Khojin Wei Zhu
CO2 SFG
John Haan PrabuddhaMukherjee BjörnBraunschweig Prof Dana Dlott

32. Questions

33. NYC Sized Solar Collector Is Needed
Assume 100,000 barrels/day -1% of US demand
5 kw-hr/m2/day solar flux, 5% efficiency solar to gasoline
5 9 2
10 bbl 6 10 J m day
day bbl (5%)(5kw hr)
2
kw hr km 2
6 6 2
670 km
3.6 10 J 10 m
770 km2 of land

34. Also Need to Examine Selectivity
CO2 + 2H+ + 2e- → CO + H2O
2H+ + 2e- → H2
cathode
electrolyte
anode
2H2O → O2 + 4H+ + 4e-