Carbon dioxide and the splitting of water

Carbon dioxide and the splitting of water

Unique Global Possibilities has developed a process to utilize carbon dioxide emissions from fossil fuel combustion to efficiently produce energy which can be stored.

The process utilizes carbon dioxide to split water molecules into hydrogen ions (protons) and hydroxide ions.  The hydroxide ions react with carbon dioxide to produce bicarbonate.  The hydrogen ions are converted to hydrogen gas at a cathode at very low voltage.  The bicarbonate ions are converted to oxygen gas at an anode at slightly higher voltage.  In both cases, the power required is considerably less than the power required for the standard electrical splitting (electrolysis) of water.  That is, there is a decrease in the power needed to produce hydrogen.

A comparison of relative hydrogen production from water per se and from a carbon dioxide/water mixture is shown below.









Using the process developed by Unique Global Possibilities, hydrogen gas can be produced at a cathode during periods (of electricity production) when excess renewable energy is available.  The stored hydrogen can then be utilized elsewhere or combusted during periods when renewable energy is no longer available.

Alternatively, the hydrogen produced can be reacted with carbon dioxide emissions from fossil fuel combustion using the well known Sabatier (methanation) reaction to produce methane.  The methane produced can be stored for use elsewhere or combusted on-site to create a ‘semi-closed’ chemical loop for further energy (electricity) production in those systems that utilize methane.  View a poster presentation of methane as a renewable energy source.

Methane as a renewable energy source

In addition, the hydrogen produced can be added directly to existing natural gas (or methane) transmissions systems. This would be beneficial if relatively small reductions in carbon dioxide emissions are required by law or public policy - say, five to twenty per cent carbon dioxide reduction.  The natural gas (or methane) transmission system could be injected with hydrogen to a concentration that decreases total carbon dioxide emissions by the relevant small percentage.  Once again, a ‘semi-closed’ loop is formed.  Blending hydrogen gas with natural gas (or methane) is a well documented procedure utilized in many parts of the world - for example in Honolulu, Hawaii, methane gas is delivered with significant hydrogen blends.  View a Technical Report from the US Department of Energy on blending hydrogen into natural gas (methane) pipeline networks.

The bicarbonate formed when hydroxide ions react with carbon dioxide in water appears to be a loose attraction between carbon dioxide and hydroxide.  In other words, carbon dioxide in water may be interpreted possibly as an hydroxide ion carrier.  Alternatively, the hydroxide ions formed by the reaction of carbon dioxide with water may migrate to the (positive) anode as hydroxide ion entities per se.  If carbon dioxide is an hydroxide ion carrier, or hydroxide ions per se migrate to the anode, the problem of the reaction overpotential for the oxidation of water to oxygen at the anode has been largely overcome.  Hydroxide ions require only a fraction of the power to produce oxygen gas compared to the power required for the electrolysis of water to produce oxygen gas.


VOLTAGE

(At < 0.01 amps)

WATER

CARBON DIOXIDE / WATER MIXTURE

Relative hydrogen

at cathode

Relative hydrogen

at cathode

1 volt

0

400

1.3 volts

10

530

5 volts

50

1,450

10 volts

320

2,550

20 volts

1,080

3,970

30 volts

2,980

4,960

Methane as a renewable energy source.jpg

The hydroxide ion per se is a relatively strong electron donor.  The oxidation of hydroxide ions to produce oxygen at an anode can be represented by:

Anode (oxidation)

4OH-O + 2HO + 4e-        E = -0.40V


Proton

[Positive charge]

Hydroxide ion

[Negative charge]

Carbon dioxide

Carbon dioxide

Water

+

-

MEDICAL RESEARCH

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© 2013 Unique Global Possibilities, Inc.

Electrolysis of water

The Sabatier reaction

COMMERCIAL ENERGY RESEARCH