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