V vs. Ag/AgCl electrode No clathrates V vs. Ag/AgCl ...
Transcript of V vs. Ag/AgCl electrode No clathrates V vs. Ag/AgCl ...
Daniel DeCiccio*$, Francisco Schunk*, Steven Ahn$, Sugat Sen$, Tayhas Palmore$, Christoph Rose-Petruck*
*Department of Chemistry, Brown University, $ School of Engineering, Brown University
Introduction
We aim to develop new technology that captures and converts carbon
dioxide (CO2) into valuable products such as ethylene. Currently, the
chemical industry uses oil, a non-sustainable carbon source, to
makes billions of pounds of these products. The replacement of oil by
CO2 as a carbon source is a promising alternative because of the
great abundance of CO2.
We attacked the problem in a new way by first capturing the CO2 in
clathrate hydrates and then reducing the CO2 electrochemically. By
first using clathrates to capture and sequester carbon dioxide we
created the first processes for capturing and converting carbon
dioxide into hydrocarbons. We are the first group to both capture and
convert the carbon dioxide.
Water-solvated gases with molecular diameters between 0.35nm and
0.75nm can transform into inclusion compounds under suitable
thermodynamic conditions. Gas solute molecules occupy sites in
aqueous cage structures formed by the water molecules. The guest
molecules do not chemically bind to the water molecules but stabilize
the clathrates cages. These inclusion compounds are known as
clathrate hydrates. Clathrate hydrates allow the storage of huge
volumes of gas, up to more than an order of magnitude more than
would usually be soluble in a solution.
Clathrates usually form at high pressure and low temperature. The
pressure required to form clathrate hydrates can be reduced by
adding solute molecules, such as tetrahydrofuran, to the liquid water.
The clathrates form a slushy like solution which can selectively uptake
different gasses based on the temperature we set the reactor to.
Experimental
Conclusion
We use a copper foam working electrode (cathode) to increase surface
area available to reduce CO2.
Clathrate Hydrates of Natural Gases, E. D. Sloan, 2 ed. (Jr. Marcel
Dekker, Inc, New York, 1998).
Conversion of Carbon Dioxide into
Hydrocarbons using Clathrates Hydrates
References
We Performed cyclic voltammetry to characterize the electrochemical
properties of the copper foam and chronopotentiometry to reduce the CO2.
Gaseous products were quantified with gas chromatograph and liquid
products with gas chromatography
Clathrate Hydrates
Custom Batch Reactor
Clathrate Slurry
Electrochemical Cell
Electron micrographs of copper foam electrodes
We built a custom batch reactor to make up to 2L of clathrate slurry at
a time. The reactor is chilled and under constant slight positive CO2
pressure. The Clathrate hydrates are then loaded into an electrochemical
cell to perform electrolysis.
Manometer
showing
positive
pressure
Cyclic Voltammogram of
copper foam showing the
onset potential where the
bottom part of the curve
begins to drop at ~-1.0V
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
110%
120%
-1.8 -1.7 -1.6 -1.5 -1.4 -1.3 -1.2 -1.1 -1 -0.9
Fara
dai
c Ef
fici
ency
(%
)
V vs. Ag/AgCl electrode
With clathratesTotalH2COHCOOH
0%
1%
2%
3%
-1.8 -1.7 -1.6 -1.5 -1.4 -1.3 -1.2 -1.1 -1 -0.9
Fara
dai
c Ef
fici
ency
(%
)
V vs. Ag/AgCl electrode
With clathratesCH4
C2H4
C2H6
C3H6
C3H8
C4H8 ?
C4H10 ?
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
110%
120%
-1.8 -1.7 -1.6 -1.5 -1.4 -1.3 -1.2 -1.1 -1 -0.9
Fara
dai
c Ef
fici
ency
(%
)
V vs. Ag/AgCl electrode
No clathratesTotal
H2
CO
HCOOH
0%
1%
2%
3%
-1.8 -1.7 -1.6 -1.5 -1.4 -1.3 -1.2 -1.1 -1 -0.9
Fara
dai
c Ef
fici
ency
(%
)
V vs. Ag/AgCl electrode
No clathratesCH4
C2H4
C2H6
C3H6
C3H8
C4H8 ?
C4H10 ?
When clathrate hydrates were used as a source of carbon dioxide, we
saw
Greater carbon monoxide production at -1V vs Ag/AgCl, 70% vs
10%
Greater formic acid production at -1.3 and -1.7V vs Ag/AgCl
Less hydrogen production at all potentials
We demonstrated the first use of
clathrate hydrates as a gas supply to an
electrochemical reaction. This is the
first work to incorporate both carbon
capture and conversion technology into
one overall process.
This is a first step to creating an
artificial carbon cycle in which carbon
dioxide may be captured and converted
into usable products such as formic
acid and carbon monoxide
We have begun investigating the use of
clathrate hydrates with a variety of other
catalysts.
Results