High rate electrochemical devices

Abstract

A device and system useful for highly efficient chemical and electrochemical reactions is described. The device comprises a preferably porous electrode and a plurality of suspended nanoparticles diffused within the void volume of the electrode when used within an electrolyte. The device is suitable within a system having a first and second chamber preferably positioned vertically or in other special arrangements with respect to each other, and each chamber containing an electrode and electrolyte with suspended nanoparticles therein. When reactive metal particles are diffused into the electrode structure and suspended in electrolyte by gasses, a fluidized bed is established. The reaction efficiency is increased and products can be produced at a higher rate. When an electrolysis device can be operated such that incoming reactants and outgoing products enter and exit from opposite faces of an electrode, reaction rate and efficiency are improved. Ideally, this device and system can be used to rapidly produce significant quantities of high purity hydrogen gas with minimal electricity cost.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of application Ser. No. 11 / 716,375, filed on Mar. 9, 2007.BACKGROUND OF THE INVENTION[0002]1. Technical Field[0003]The inventions disclosed herein generally relate to improved electrochemical systems and their use and, in particular, to water electrolysis devices for the production of high purity hydrogen and oxygen, and catalysts for these devices which promote increased electrical and cost efficiency, and methods of using such devices and for the production of hydrogen and oxygen.[0004]2. Related Art[0005]Hydrogen is a renewable fuel that produces zero emissions when used in a fuel cell. In 2005, the Department of Energy (DoE) developed a new hydrogen cost goal and methodology, namely to achieve $2.00-3.00 / gasoline U.S. gallon equivalent (gge, delivered, untaxed, by 2015), independent of the pathway used to produce and deliver hydrogen. The principal method to produce hydrogen is by stream refo...

AI Technical Summary

Benefits of technology

[0011]When immersed within an electrolyte, the metal particles can float freely and can substantially infuse into the porous / reticulate metal plate to create an electrode with extremely high surface area.

[0012]The electrodes in this invention can be applied to a variety of devices, including a hydrogen generation electrode in a water electrolyzer system. In such an embodiment, the electrode can function as a fluidized bed. At least one advantage is that the electrode can be operated at currents (rates) exceeding 1 A / cm2 and efficiencies in excess of 65% (measured by voltammetric or galvanometric electrochemical testing.), which in turn means that large amounts of hydrogen can be produced using less electricity. Typical electrodes have a far lower surface area and thus cannot operate at rates significant enough to produce large quantities of hydrogen. Other advantages may include, depending upon the configuration, circumstances, and environment, the ability to scale the electrode to a wide variety of sizes, a high rate of hydrogen production, and the ability to minimize agglomeration by using nano-sized particles. The fluidized bed reactor of the invention preferably produces from about 0.1 to about 3, more preferably from about 1 to about 3 gge / hr / m2 of hydrogen. A gge is a “U.S. gallon of gasoline equivalent”

[0015]The reaction efficiency may be enhanced depending on the metal nanoparticles chosen. Efficiencies of at least 75%, preferably at least 85% may be achieved. Preferably, the plurality of reactive metal particles have an oxide shell. The reactive particles preferably comprise a metal selected from the group consisting of metals from groups 3-16, lanthanides, combinations thereof, and alloys thereof, and most preferably the metal nanoparticles are nickel, iron, combinations thereof, and alloys thereof.

[0017]Preferably, the generated anode and cathode gasses flow through the container in a manner that suspends the nanoparticles within the fluid, creating a fluidized bed. Most preferably, the bed is fluidized by the reaction products. At least some advantages of this configuration include, (i) elimination of pumps via direct extraction of gasses from the container, such as via upper vents, and the self propagating nature of the fluidized bed, (ii) ease of keeping hydrogen and oxygen gasses separated, (iii) ease of controlling temperature and pressure, (iv) simple design, and (v) less expensive per unit of hydrogen produced, to name a few.

[0019]In another aspect of the invention, a new electrochemical device is provided, preferably a water electrolysis device. Unlike traditional electrolyzers, such as that shown in FIG. 1, one embodiment of the inventive electrochemical device system may be oriented horizontally rather than vertically. With such an arrangement, electrolyte may be moved through a lower chamber, with oxygen being generated on a lower electrode. A deflector is preferably placed in the electrolyte stream to ensure removal of all generated oxygen from the system. Oxygen may be scrubbed from the electrolyte before it is circulated back into the system. In at least one embodiment, water generated from the reaction can move through a separator membrane to the upper chamber. An upper chamber electrode produces hydrogen gas. Because hydrogen gas is less dense than the electrolyte, the hydrogen may bubble upwards and can then be removed from the system. Preferably, a fluidized bed is established in the upper chamber employing catalytic nanoparticles. Contemporaneously, hydroxyl ions (OH—) are generated and may move downwardly through the separator for consumption at the lower chamber electrode. At least some advantages include, depending upon the configuration, circumstances, and environment, (i) that only half of the system may need pumping (unless the device is oriented on an angle, in which case no pumping may be necessary) whereas traditional systems need total pumping; (ii) half the pumping means half the parasitic losses; (iii) there is no need for a gas separator in the upper chamber; gas freely moves upward because it is less dense, and (iv) ions move from the bottom of the electrode while hydrogen escapes from the top, which gives a lower ionic resistance.

Problems solved by technology

Typical electrodes have a far lower surface area and thus cannot operate at rates significant enough to produce large quantities of hydrogen.

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