Researchers Develop Lithium-Water Electrochemical Cell for the Controlled Generation of H2 and Electricity
14 May 2010
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| Schematic representation and operating principles of the lithium–water electrochemical cell used for hydrogen generation: (1) external circuit and (2) inside of lithium–water electrochemical cell. Source: Wang et al. Click to enlarge. |
Scientists from the Energy Technology Research Institute, AIST in Tsukuba, Japan, have developed a lithium-water electrochemical cell for the controlled generation of hydrogen and electricity. The researchers, headed by Haoshen Zhou, foresee the use of this process in fuel cells for mobile applications. A paper on their work was published in the journal ChemSusChem.
Although direct chemical reactions between water and certain metals—alkali metals including lithium, sodium and others—can produce a large amount of hydrogen in a short time, these reactions are too intense to be controlled. (E.g., the high-school chemistry demonstration of the violent reaction between sodium and water.)
In the present work, the intense direct chemical reaction between lithium and water is transformed into a controllable electrochemical reaction in a lithium–water electrochemical cell, through which the controllable generation of hydrogen is achieved easily.
—Wang et al.
The closed fuel cell system developed by Dr. Zhou and his team has two compartments separated by a water stable lithium super-ionic conductor glass film (LISICON). One compartment contains a metallic lithium electrode (anode) in an organic solvent (1m LiClO4 in ethylene carbonate/dimethyl carbonate), while the other contains an aqueous electrolyte solution (LiNO3/H2O) with a carbon-based hydrogen generation electrode (cathode).
On discharge, the metallic lithium (anode) is converted into lithium ions and the generated lithium ions diffuse from the organic solution across the LISICON film to the aqueous solution. Simultaneously, hydrogen gas is generated on the cathode. During this process, electrons pass around the external circuit, forming the current.
Only lithium ions can pass across the LISICON film. The rate of both half reactions within the lithium–water electrochemical cell can be controlled by the current, indicating a controllable hydrogen generation.
Another attractive aspect of this technology is that lithium metal can be produced from salt solutions (e.g., sea water) by using sunlight. In other words, energy from the sun can be “stored” in the metal, and then be used on demand by reacting the lithium in the fuel cell. Recharging the battery would be a matter of replacing the lithium metal cell.
Hydrogen generation from the lithium–water cell suffers from several weaknesses at this early stage, according to the researchers:
- The hydrogen production rate is still limited by the internal resistance of the lithium–water cell. The conductivity of the solid-state electrolyte film (LISICON) needs to be improved in future studies.
- Good mechanical strength is also demanded from the LISICON film.
- The LiOH concentration in the lithium–water cell is increased gradually during the hydrogen generation process. The inherent low solubility of LiOH and the reaction of LiOH with traces of CO2 may also limit the hydrogen production and the performance of the lithium–water electrochemical cell; this issue requires further studies.
Nevertheless, they note that hydrogen generation by the lithium–water electrochemical cell is controllable, and may be directly applied for energy conversion devices. The researchers suggest the establishment of a new possible route for hydrogen generation: lithium–metal production using solar energy and controllable hydrogen generation from lithium–water electrochemical cells.
Lithium, which is already widely used in various lithium ion batteries and will also be applied in the lithium-air fuel cell and this lithium-water/hydrogen/fuel cell system in the future, may lead humanity to enter a new sustainable lithium society, based on smart grid systems of lithium energy networks.
—Haoshen Zhou
Resources
Yonggang Wang, Huiqiao Li, Ping He, Haoshen Zhou (2010) Controllable Hydrogen Generation from Water. ChemSusChem 2010, 3, No. 5, 571-574 doi: 10.1002/cssc.201000049
Yet another approach to a new era of energy independence. Residential Power Units will dramatically reduce the demand on centralized power systems. This will save vast sums of public funds spent on big hydro, nuke and coal fired central power plants. By building and installing RPUs in residences and small businesses across North America, we will reduce the high cost of conventional power generation and increase our energy efficiency.
This approach seems a bit distant for commercialization, but an interesting direction to take - H2 and electricity from a single system.
Posted by: sulleny | 17 May 2010 at 03:10 PM
This seems like something between a primary and secondary cell. You replace the material inside and reuse the cell. This could work, if you had a fuel cell car to use the H2 and the facilities to change the cells.
Posted by: SJC | 18 May 2010 at 12:05 PM
Another example of scientists trying to get publicity and money for their work by ignoring both scientific and economic reality. There exists now no easy economic way of producing lithium metal from sea water. There is also no easy economic way of collecting solar energy for this purpose. Zinc air cells are easier to construct and operate in any case if the metal is to be recycled. Just announce that hydrogen is produced and you can get more money because people don't know that it would be more efficient to produce electricy directly rather than hydrogen from the energy in the lithium-metal-air combination, and hydrogen is the perfect!!! fuel because it does not produce CO2 but it does produce the much more prevalent greenhouse gas H20 which is responsible for much if not most of the greenhouse effect. I will not attempt to justify for any reason that the release of CO2 does not increase the temperature of the earth, but I will deny totally that the existence a large and increasing human race is threatened by more CO2 in the air. The rest of the life forms on earth are far more threatened by the existence of the human race than by any green house effect of CO2. In fact the present attemps to reduce CO2 with biofuels is devastating large tracts of natural forests and grass lands and the animals that lived in that ecology. Uranium the weight of a nickel and about one third the volume will power a hundred watt lightbulb for forty years. For portable power, neptunium 237 can be transformed into Plutonium 238 in a nuclear reactor. A hydrogen fusion reactor that operates by the fusion of deuterium would produce lots of neutrons for this purpose but no one knows yet how to build such an operating device except in fifty years from the present. Jam tomorrow just no jam today.
Plutonium 238 cannot make a bomb and is far less poisonous than nicotine. A kilogram of plutonium 238 could be used to generate 100 watts of electricity or more with a small Stirling engine. Four hundred watts of heat would be produced. After about ninety years only 500grams of plutonium would remain and would be producing only 50 watts of electricity. A soft drink can could protect you from almost all of its nuclear radiation but the can would be glowing hot. Fifty kilograms of plutonium 238 could make an automobile that could run continuously without stop. Talk about the limited range of electric cars?? A few billionaires could own such cars and France and Russia should go into the business of making them and the fuel. Ten kilograms would power a small house. The modern uranium centrifuges could be modified to extract plutonium 238 from existing spent fuel rods for billionaires cars at great cost. In the meantime people in France can drive TH!NK cars with ZEBRA batteries and also drive on nuclear power. ..HG..
Posted by: Henry Gibson | 03 June 2010 at 09:28 AM