Alkaline fuel cell

Details Alkaline fuel cell Alkaline fuel cell

2000-03-13

2002-09-10

Ryan, Patrick (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C429S010000, C429S047000, C429S218200, C429S010000, C420S900000

Reexamination Certificate

active

06447942

ABSTRACT:

FIELD OF THE INVENTION
The instant invention relates to fuel cells and more specifically to Ovonic instant startup alkaline fuel cells. The present fuel cells utilize electrodes which solve the major barriers present in modern fuel cell technology, using materials which contain no costly noble metals and operate at ambient temperatures. Particularly, the instant startup fuel cells of the instant invention contain anodes which are formed from hydrogen storage materials. The hydrogen storage materials not only store hydrogen, but also have excellent catalytic activity for the formation of atomic hydrogen from molecular hydrogen and also have superior catalytic activity toward the formation of water from hydrogen ions and hydroxyl ions. In addition to having outstanding catalytic capabilities, the materials also have superior corrosion resistance toward the alkaline electrolyte of the fuel cell. These features uniquely allow the present fuel cells to start up instantly, be used in a broad range of temperatures (−20 to 150° C.),and to accept recaptured energy by operating in reverse as an electrolyzer, thus, eliminating the need for an external heating element or battery. In this manner, the instant inventors have provided a new generation of fuel cells that rectifies the problems that have plagued the technology since its inception.
BACKGROUND OF THE INVENTION
The instant application for the first time discloses fuel cells that overcome the major deterrents to the widespread utilization of such fuel cells. Namely, the instant inventors have solved the major barriers present in modern fuel cell technology, using materials which contain no costly noble metals in the electrodes thereof. These barriers include: hydrogen storage capabilities, requisite catalytic activity, ionic conductivity, corrosion resistance, and increased resistance toward the poisoning effect of different gases. Additionally these materials must be low cost, containing no noble metals, so that fuel cells can be widely utilized. The anodes that are present in the fuel cells have inherent catalytic properties and hydrogen storage capacity (allowing for instant startup) using active materials which contain no noble metals. The fuel cells are capable of instantaneous startup and can store recaptured energy from processes such as regenerative braking. The materials are robust and poison resistant. The electrodes are easy to produce, by proven low cost production techniques, such as those presently employed in the production of Ovonic Ni-MH batteries. Carbon is eliminated from the anode, where in the prior art it tends to be oxidized to carbon dioxide, thus helping to eliminating the carbonate poisoning of the fuel cell electrolyte. The hydrogen storage materials of the anode are dense enough to block carbon dioxide from entering the electrolyte via the hydrogen fuel stream, but allow hydrogen to pass, acting as a hydrogen pump. The instant fuel cells have increased efficiency and power availability (higher voltage and current) and a dramatic improvement in operating temperature range (from −20 to 150° C.) The fuel cell system of the instant invention allows for widespread utilization of fuel cells in all sectors of the energy production/consumption market, thereby further fostering the realization of a hydrogen based economy. An infrastructure for such a hydrogen based economy is disclosed in U.S. application Ser. No. 09/444,810, entitled “A Hydrogen-based Ecosystem” filed on Nov. 22, 1999 for Ovshinsky, et al. (the '810 application), which is hereby incorporated by reference. This infrastructure, in turn, is made possible by hydrogen storage alloys that have surmounted the chemical, physical, electronic and catalytic barriers that have heretofore been considered insoluble. These alloys are fully described in copending U.S. patent application Ser. No. 09/435,497, entitled “High Storage Capacity Alloys Enabling a Hydrogen-based Ecosystem” , filed on Nov. 6, 1999 for Ovshinsky et al. (the '497 application), which is hereby incorporated by reference.
As the world's population expands and its economy increases, the atmospheric concentrations of carbon dioxide are warming the earth causing climate change. However, the global energy system is moving steadily away from the carbon-rich fuels whose combustion produces the harmful gas. Experts say atmospheric levels of carbon dioxide may be double that of the pre-industrial era by the end of the next century, but they also say the levels would be much higher except for a trend toward lower-carbon fuels that has been going on for more than 100 years. Furthermore, fossil fuels cause pollution and are a causative factor in the strategic military struggles between nations. Furthermore, fluctuating energy costs are a source of economic instability worldwide.
In the United States, it is estimated, that the trend toward lower-carbon fuels combined with greater energy efficiency has, since 1950, reduced by about half the amount of carbon spewed out for each unit of economic production. Thus, the decarbonization of the energy system is the single most important fact to emerge from the last 20 years of analysis of the system. It had been predicted that this evolution will produce a carbon-free energy system by the end of the 21
st
century. The present invention is another product which is essential to shortening that period to a matter of years. In the near term, hydrogen will be used in fuel cells for cars, trucks and industrial plants, just as it already provides power for orbiting spacecraft. But, with the problems of storage and infrastructure solved (see the '810 and '497 applications), hydrogen will also provide a general carbon-free fuel to cover all fuel needs.
A dramatic shift has now occurred, in which the problems of global warming and climate change are now acknowledged and efforts are being made to solve them. Therefore, it is very encouraging that some of the world's biggest petroleum companies now state that they want to help solve these problems. A number of American utilities vow to find ways to reduce the harm done to the atmosphere by their power plants. DuPont, the world's biggest chemicals firm, even declared that it would voluntarily reduce its emissions of greenhouse gases to 35% of their level in 1990 within a decade. The automotive industry, which is a substantial contributor to emissions of greenhouse gases and other pollutants (despite its vehicular specific reductions in emissions), has now realized that change is necessary as evidenced by their electric and hybrid vehicles.
Hydrogen is the “ultimate fuel.” In fact, it is considered to be “THE” fuel for the future. Hydrogen is the most plentiful element in the universe (over 95%). Hydrogen can provide an inexhaustible, clean source of energy for our planet which can be produced by various processes. Utilizing the inventions of subject assignee, the hydrogen can be stored and transported in solid state form in trucks, trains, boats, barges, etc. (see the '810 and '497 applications).
A fuel cell is an energy-conversion device that directly converts the energy of a supplied gas into an electric energy. Researchers have been actively studying fuel cells to utilize the fuel cell's potential high energy-generation efficiency. The base unit of the fuel cell is a cell having a cathode, an anode, and an appropriate electrolyte. Fuel cells have many potential applications such as supplying power for transportation vehicles, replacing steam turbines and power supply applications of all sorts. Despite their seeming simplicity, many problems have prevented the widespread usage of fuel cells.
Presently most of the fuel cell R & D focus is on P.E.M. (Proton Exchange Membrane) fuel cells. The P.E.M. fuel cell suffers from relatively low conversion efficiency and has many other disadvantages. For instance, the electrolyte for the system is acidic. Thus, noble metal catalysts are the only useful active materials for the electrodes of the system. Unfortunately, not

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