Electrolytic Extraction of Carbon from Carbon
Dioxide in Molten Salts and Applications
George Z. Chen
Energy and Sustainability Research Division,
Department of Chemical and Environmental Engineering,
Faculty of Engineering, University of Nottingham
george.chen@nottingham.ac.uk
http://inhabitat.com/los-alamos-laboratory-harvestsfuel-from-air/
http://www.sciencedaily.co
m/releases/2008/01/0801
03135757.htm
..... but the CO2
gas is not visible,
and the white
"smoke" in the
pictures is most
likely steam .....
Molten Salts Electrolysis for
CO2 Capture and Utilisation
Solar Electrolyser
CO2
-
O2
molten salt
bath
conc. solar
heat (CSH)
+
Si solar
panel (PV)
solar dish
(parabolic)
+
Principle:
Using solar energy devices to
provide the electricity and heat for
electrolysis of CO2 (and H2O)
absorbed in the molten salt into
solid carbon (or hydrocarbons) and
O2 gas.
CO2 = C + O2
U = 1.024 V (673 K)
CO2 + 2H2O = CH4 + 2O2
U = 1.037 V (673 K)
Energy storage density:
Carbon powder (Apparent density
of packed carbon powder: 0.792 g/mL)
electricity
Chen GZ, A Feasibility Study of Solar-Electrochemical Cells
for Capturing Atmospheric Carbon, The Royal Society 2007
Brian Mercer Feasibility Award, (2006)
25.97 MJ/L (7.21 kWh/L)
Methanol (Density: 0.792 g/mL)
16.71 MJ/L (4.64 kWh/L)
Utilisation of Solar Energy for
CO2 → C + O2
Energy consumption: < 40 Wh/kg-C
850 oC, 4 V, 2hrs
Li-K-CaCl2 + CaCO3
Output adjustable battery stack (Powergorilla, up to 12 V)
AO Oluwagbemiga, M. Mohammed, MEng Research and Development Project, Univ. Nottingham (2010).
CO2 → C + O2
Simple Reactor & Fast Process
Ni 5 mm rod cathode, Graphite anode, CO2 atmosphere, 520 oC,
0.30CaCl2-0.17CaCO3-0.43LiCl-0.10KCl
0.4
N2: 100 mL/min
CO2: 100 mL/min
Current (A)
0.35
0.3
0.25
0.2
N2: 200 mL/min
2.0 V, C.E.: >80 %;
E.C.: <22 kWh/kg-C
0.15
0.1
1.5 V
1.8 V
2.0 V
0.05
39 kJ g-CO2
0
0
20
40
60
80
100
120
4.0 V, 579 oC
–1C.E.: >80 %; E.C.: <45 kWh/kg-C
140
Time (min)
1.0 ~ 2.5 V
CO2
gas in
CO2
gas out
SnO2
anode
> 15000 A/m2
Mild steel
cathode
> 1 kg/m2h
CO2 environment
Furnace
Molten salt
10 mm
N2 / CO2 flow rate (mL/min, L to R):
200:0; 150:50, 100:100, 50:150, 0:200
CO2 → C + O2
Direct Carbon Fuel Cells
Electro-oxidation,150 mA, 599 °C, CO2
(3) CO32- → CO2 + ½O2 + 2e-
Pt wire WE, 10 mV/s, 599 °C, CO2
(1)
(2)
(3)
2O2- → O2+ 4e ??
(2) C + 2CO32- → 3CO2 + 4e(1) C + 2O2- → CO2 + 4e-
Electro-deposition: -2.77 V.
WE: 5 mm dia. mild steel rod;
CE: 10 mm dia. graphite rod;
RE: Ag/AgCl (Al2O3 membrane)
MS: Li2CO3-Na2CO3
(mol ratio: 52:48).
After electro-deposition.
At the end of (2).
CO2 → C + O2
Seasonal Energy Storage
Current efficiency > 90%
Direct Use in Supercapacitors
Die-pressed 13 mm dia. pellets
30 mg pellets thickness : 0.24 mm
50 mg pellets thickness : 0.35 mm
Electrolysis: 5 V, 540 oC
Electrolyte: 3 M KCl;
Current collector: Ti foils
10 mV/s
Cs up to 185 F/g
Symmetrical sandwich cell
Cell voltage (V)
Costs of different types of carbon
Type of carbon
Cost ($ kg-C-1)
Coal
0.1 - 0.3
General purpose Carbon from CO2
activated carbon
(This work)
0.5 - 3
3-5
Supercapacitor grade
activated carbon
Carbon nanotubes
and graphenes
20 - 40
200 - 400
Data shown here are the authors’ own knowledge gained in various research projects.
CO2 → C + O2
Carburisation of Metals
Surface hardening is an
economical way to enhance
performance of mild steels.
o Camshaft
o Self drill screw
o Chains
o Gearbox
o Lock shackles
o Hoist rings
o Gear
Carburised metal is difficult to machine.
Carburisation is carried out after the metal has been shaped.
Acknowledgement
Manager
2013 in Nottingham
This presentation contains contributions from the author’s past and present students and
assistants (as shown here). The work received funding from the Royal Society (20072008), EPSRC –DTA (2010-2013), and University of Nottingham (2011-2015).
Perception of CO2:
Increasing Concentration
http://en.wikipedia.org/wiki/File:Mauna_Loa_Carbon_Dioxide-en.svg
Contribution to the greenhouse effect,
and hence the climate change.
Perception of CO2:
CCS and Consequences?
CCS: Carbon capture & storage.
http://www.nottingham.ac.uk/ciccs/
Various rocks (basalt, caprock and
sandstone) changed compositions
& structures in CO2 saturated water
under mild hydrothermal conditions.
Secondary phase (CuO) formation in
caprock after hydrothermal reaction with
CO2 saturated water for 2 days at 80 oC.
Zhao, Large, Chen, Unpublished work,
Univ. Nottingham, 2010.
Perception of CO2:
A Rare Resource
http://confusedbytheworld.com/deforestation-101-continued/
N2
O2
Ar
CO2
Selected gases in air
Nature does not store the CO2 gas, but utilises solar energy to capture and
convert it to O2 gas and biomass (materials, foods, and chemical energy).
Photosynthesis: 6CO2 + 6H2O + hv → C6H12O6 + 6O2
This natural process is slow and needs water
(growth & processing difficulties).
CO2 → C + O2
Low Burning Temperature
650 oC
350 oC
Pellet of electrolytic carbon
Low oxidation onset (combustion) temperatures
are due to products containing nanostructures,
and metallic residuals (e.g. Fe, Cu, K).
Ignition in air
Self-sustained combustion
in air