Abstract:
A device and method is provided for increasing production of hydrogen during electrolysis. Initially, one of the vibrational modes of an electrolytic fluid is determined. A laser is then tuned to a wavelength near the selected vibrational mode. The tuned laser is then applied to the electrolytic fluid during electrolysis. The application of the laser with a wavelength near the wavelength of a specific vibrational mode of the electrolytic fluid causes an increase in the rate of production of hydrogen, when compared to electrolysis alone. The specific vibrational mode may correspond to a mode that stretches the inter-atomic bonds of hydrogen in the electrolytic fluid.

Description:
FIELD 
       [0001]    The present invention relates to a method for increasing hydrogen production during electrolysis. The invention increases hydrogen production by applying radiation having a wavelength that corresponds with the absorption wavelengths of the vibrational modes of the electrolytic solution. 
       BACKGROUND 
       [0002]    It is well known that our current economy relies on high energy density fuels to produce electricity and operate vehicles. Generally, these high energy density fuels are petroleum derivatives such as gasoline, natural gas, and oil of various grades. It is also well known that the supply of fossil fuels is limited. Furthermore, combustion of fossil fuels produces greenhouse gases which affect the climate. Thus, there exists a need for production of alternative fuels that are sustainable and environmentally benign. 
         [0003]    A second problem exists with alternative electrical production methods, such as hydroelectric and wind power. Often the facilities that produce alternative electricity are remote from the areas that use the electricity. This remoteness requires an extensive array of power transmission lines that is expensive to install and maintain. Thus, a need exists to transform this electricity into a fuel that may be transported in a less expensive manner than by power transmission lines. 
         [0004]    Hydrogen has long been considered a possible alternative to fossil fuels. Hydrogen may be produced by electrolysis, essentially converting electric power to hydrogen gas. The hydrogen gas may then be compressed or liquefied, creating a higher energy density fuel. Hydrogen may be transported either through pipelines or by tanker trucks. Hydrogen is a transportable, relatively clean and sustainable fuel. Unfortunately hydrogen is not readily available in nature. 
         [0005]    Molecular hydrogen must be produced from other molecules such as water and methane. A variety of hydrogen production methods have been used. The most common method of hydrogen production involves applying an electrical current through an electrolytic solution. Generally, the electrolytic solution is an elemental salt dissolved in water. Known hydrogen production techniques such as electrolysis and steam reforming require the application of energy to separate hydrogen-bearing molecules into products that include molecular hydrogen. Thus, there exists a need for more rapid and efficient methods of producing hydrogen. 
         [0006]    Some methods attempt to produce hydrogen by applying only sunlight to photosensitive semiconductor electrodes in an electrolytic solution, generally of water and an elemental salt. Examples of this include U.S. Pat. Nos. 3,925,212; 4,011,149; 4,090,933 and 4,501,804. As sunlight is applied to the photosensitive semiconductor electrodes, a voltage difference is produced causing hydrogen to be produced. However, these methods are generally slow, produce relatively little hydrogen and operate only when there is sufficient sunlight. 
         [0007]    A second group of patents attempts to produce hydrogen by application of solar power only. Examples of this are U.S. Pat. Nos. 6,669,827 and 4,342,738. These methods may apply solar power directly or divide it into ultraviolet and infrared radiation. U.S. Pat. No. 6,669,827 suggests the use of ultraviolet radiation as the source for photolysis using light, but not electricity. U.S. Pat. No. 4,342,738 suggests separating sunlight into ultraviolet and infrared radiation. Hydrogen is produced by using IR to heat water and UV to irradiate the resulting steam. Metals and salts may be added to act as catalysts. Neither of these patents suggest using radiation in combination with electrolysis 
         [0008]    A third set of applications attempt to match the wavelength of solar radiation to the wavelength of the electrolytic fluid by use of filters, lenses and mirrors. Examples of this are U.S. Pat. No. 4,171,251; and U.S. Patent Application 2007/0272541. U.S. Pat. No. 4,171,251suggests using light with a wavelength of 9.2 to 10.8 μm. It does not suggest combining photodissociation (photolysis) with electrolysis to produce hydrogen. 
         [0009]    U.S. Patent Application 2007/0272541 describes irradiating water with infrared radiation from sunlight to produce hydrogen. Specifically, the application suggests the portion of sunlight having a wavelength of 2.8 to 3.2 μm. This wavelength is suggested because it corresponds with an absorption wavelength of water. However, this application suggests using only amplified sunlight in this wavelength range for the production of hydrogen. Most of the sunlight in this wavelength range is absorbed by water in the atmosphere. The result is that only a minimal amount of hydrogen is produced and only when the sun is sufficiently intense. Additionally, the Application does not suggest radiation from sunlight in combination with electrolysis to produce hydrogen. 
         [0010]    A method of hydrogen production is needed that produces large amounts of hydrogen in as rapid and efficient a manner as possible. 
       SUMMARY 
       [0011]    In one aspect of the present invention, a method is disclosed whereby hydrogen is produced by electrolysis through an electrolytic solution containing hydrogen. Hydrogen production is increased by irradiating the electrolytic solution with a laser. The laser is optimized by determining the vibrational modes of the electrolytic solution and tuning the wavelength of the laser to a wavelength near one of the vibrational modes. The vibrational modes may be identified by examining the absorption bands of a given electrolytic solution. 
         [0012]    The result of irradiating the electrolytic solution during electrolysis using a laser beam with an optimized wavelength is an increase in the rate of production of hydrogen when compared to electrolysis using the same electrolytic solution without irradiation. 
         [0013]    In a second aspect of the present invention, an invention is disclosed whereby hydrogen is produced by electrolysis through an aqueous electrolytic solution. The hydrogen production is increased by irradiating the electrolytic solution with a laser. The wavelength of the laser is optimized by adjusting the wavelength of the laser near that of a vibrational mode of the electrolytic fluid. The produced hydrogen then passes through a semi-permeable membrane and is trapped in a collection tank. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  shows an example of a test fixture using the current invention. 
           [0015]      FIG. 2  is a graph showing wavelength versus spectral irradiance for water. The dips in the direct+circumsolar curve describe the absorption bands of atmospheric constituents including water. 
           [0016]      FIG. 3  is a table showing the wavelengths of the various vibrational modes for water. 
           [0017]      FIG. 4  shows the rate of hydrogen production when an electrolytic fluid (3.0V 40 ml solution; 0.250 M) is used for electrolysis. The rate of hydrogen production is indicated by the change in height of the fluid level in the manometer. The manometer fluid level rises as the accumulation of hydrogen in the electrolytic cell causes cell pressure to increase. The rate of hydrogen production is greater when the electrolytic solution is irradiated with a laser. 
           [0018]      FIG. 5  shows the rate of hydrogen production when an electrolytic fluid (4.0V 40 ml solution; 0.250M) is used for electrolysis. The rate of hydrogen production is indicated by the change in height of the fluid level in the manometer. The manometer fluid level rises as the accumulation of hydrogen in the electrolytic cell causes cell pressure to increase. The rate of hydrogen production increases when the electrolytic solution is irradiated with a laser. 
           [0019]      FIG. 6  shows the average hydrogen production rate as a function of voltage for a 40 ml, 0.25 Molar solution with and without irradiation by a laser. 
           [0020]      FIG. 7  shows the hydrogen production rate increase as a function of voltage for a 40 ml, 0.25 Molar solution irradiated by a laser. 
           [0021]      FIG. 8  shows a hydrogen generator producing hydrogen gas according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]      FIG. 1  depicts a test system employing an embodiment of the present invention. Reaction vessel  10  holds electrolytic fluid  20 . Cathode  30  and anode  40  are submersed in electrolytic fluid  20 . Cathode  30  and anode  40  are electrically connected by cathode lead  35  and anode lead  45 , respectively through a DC power supply (not shown). Stopper  50  prevents produced hydrogen gas  80  from escaping to the atmosphere. Cathode lead  35 , anode lead  45 , and manometer  60  pass through stopper  50  in such a manner as to prevent hydrogen gas  80  from escaping the test system. The bottom of the manometer tube is below the electrodes to prevent hydrogen gas from entering the manometer  60 . Laser  70  irradiates electrolytic fluid  20  near cathode  30 . 
         [0023]    Electrolytic fluid  20  is selected to have high hydrogen content as well as an appropriate conductor to optimize hydrogen gas production when a voltage is applied between anode  40  and cathode  30 . Electrolytic fluids and the conductors dissolved therein are well known in the art and generally consist of an acid or water and an elemental salt. 
         [0024]    Reaction vessel  10  is selected to allow as much energy as possible to pass from laser  70  to electrolytic fluid  20 . Such vessels are well known in the art. Selection of such a vessel may be based on the wavelength of light of the laser and the absorption bands or vibrational modes of the electrolytic fluid selected. 
         [0025]    In use of the test fixture in  FIG. 1 , electrolytic fluid  20  is held in reaction vessel  10 . Anode lead  45 , cathode lead  35  and manometer  60  pass through stopper  50  in such a way as to prevent leakage of hydrogen gas  80 . Stopper  50  is secured to reaction vessel  10  in such a way as to prevent leakage of hydrogen gas  80  into the atmosphere. The produced hydrogen gas  80  accumulates at the top of the reaction vessel  10  where it is trapped as a gas phase by the stopper  50 . The accumulation of hydrogen gas  80  increases pressure on the electrolytic fluid  20  in the cell. The increase in pressure is transmitted through the electrolytic fluid  20  and causes the electrolytic fluid  20  in the manometer  60  to rise. 
         [0026]    Anode  40  and cathode  30  are submerged in electrolytic fluid  20 . A potential difference (voltage) is established between anode  40  and cathode  30  using the DC power supply attached to anode lead  45  and cathode lead  35 . The potential difference between anode  40  and cathode  30  creates electrolysis in electrolytic fluid  20  and results in the production of hydrogen gas  80 . Production of hydrogen gas  80  increases the pressure in the reaction vessel  10 , resulting in a rise in the fluid level of the manometer  60 . 
         [0027]    Laser  70  is matched to a wavelength near that of a vibrational mode of the electrolytic fluid  20 . The absorption bands aid in predicting the vibrational modes of the electrolytic fluid  20  (as shown for water in  FIGS. 2 and 3 , for example). The vibrational modes correspond to the bending or stretch modes of inter atomic bonds within the electrolytic fluid  20 . Laser  70  irradiates electrolytic fluid  20  during electrolysis, increasing the rate of production of hydrogen gas  80  for a given voltage. The rate of production of hydrogen gas  80  is measured by recording the rate at which the fluid level rises in the manometer  60 . 
         [0028]      FIGS. 4-7  show the increase in the rate of production of hydrogen using a test fixture as described above. 
         [0029]    It is contemplated that a wide variety of electrolytic fluids may be selected within the scope of the invention, as many are known in the art. Electrolytic fluid or electrolytic liquid is used as a general term and is intended to include hydrogen bearing materials in any state; including liquids, gels, and solids. Additionally, it is contemplated within the scope of the invention that as the electrolytic fluid is varied, the wavelength of the laser may be varied accordingly. The basis for varying the wavelength of the laser may include, among other considerations, the absorption bands and the vibration mode of the electrolytic fluid. 
         [0030]    In testing the invention of  FIG. 1 , an aqueous solution of water and Epsom salt was selected as the electrolytic fluid  20 . Tests were performed for an electrolytic fluid  20  that consisted of 40 ml of a 0.25 Molar solution. 
         [0031]    The optimum wavelength for operation of the laser depends on the absorption of radiation by the electrolytic solution. In this example, water is used as the base of the electrolytic fluid. The absorption bands are due to the absorption of light by a molecule in a frequency range that transfers photon energy to the molecule if the frequency of the photon matches the frequency of the vibrational and rotational modes of the molecule. The photon energy excites the molecule by increasing the rotation or vibration of the molecule. The band of frequencies that can be affected by the laser beam is broadened by thermal motion of the molecule and collisions with other molecules. The process described here focuses on exciting the vibrational modes that correspond to the stretching of the bond between hydrogen and oxygen in water. This excitation can appear as a heating effect since it increases the motion of the water molecule. The difference between using a conventional heat source (such as a hot plate, oven, or solar heater) to heat the electrolytic cell and using the laser is that the laser beam energy is more efficient at increasing the specific vibrational energy of the H—O bond, while a heat source will distribute the same energy across several modes, including vibration, rotation, and translation. The laser beam is more efficient than a conventional heat source at providing energy where it can directly affect the H—O bond. Optimiztion of the radiation wavelength could be determined for any hydrogen bearing fluid and used to improve the rate of hydrogen production through electrolysis for a given voltage. 
         [0032]      FIG. 2  shows the various wavelengths of the absorption bands of water.  FIG. 3  describes the vibrational modes of water.  FIG. 2  shows a range of 2.5-3.25 μm for one of the absorption bands of water.  FIG. 3  shows a symmetric stretch mode of 2.734 μm and an asymmetric stretch mode of 2.662 μm as the vibrational modes of water. Based on these figures and the selection of water and Epsom salt as the electrolytic fluid  20 , an operational range for the laser was determined to be in the infrared range, approximately 2.5 to 3.25 μm. 
         [0033]    An erbium-YAG (yttrium-aluminum-gadolinium) laser was selected as laser  70 . Erbium-YAG lasers operate at approximately 2.94 μm. Pyrex glass was selected as the reaction vessel  10 . Pyrex glass is transparent to infrared radiation within the wavelength range produced by the Erbium-YAG laser. 
         [0034]      FIG. 4  shows an increase in hydrogen production versus time (for 40 ml of 0.25 Molar electrolytic solution  20  with 3 Volts applied between anode  40  and cathode  30 ) with the test system of  FIG. 1  operated as described above. The increase in production rate is shown by the more rapid increase in height of the electrolytic fluid  20  level in the manometer  60 . 
         [0035]      FIG. 5  shows an increase in hydrogen production rate versus time (for 40 ml of 0.25 Molar electrolytic solution  20  with 4 Volts applied between anode  40  and cathode  30 ) with the test system of  FIG. 1  operated as described above. 
         [0036]      FIG. 6  shows the average increase in the hydrogen production rate as a function of voltage applied between anode  40  and cathode  30  (for 40 ml of 0.25 Molar electrolytic solution  20 ) with the test system of  FIG. 1  operated as described above. 
         [0037]      FIG. 7  shows the percentage increase of hydrogen production rate as a function of voltage applied between anode  40  and cathode  30  (for 40 ml of 0.25 Molar electrolytic solution  20 ) with the test system of  FIG. 1  operated as described above. 
         [0038]      FIG. 8  depicts a hydrogen generation system employing an embodiment of the present invention. Reaction vessel  10  holds electrolytic fluid  20 . Cathode  30  and anode  40  are submerged in electrolytic fluid  20 . Cathode  30  and anode  40  are electrically connected by cathode lead  35  and anode lead  40 , respectively. Cathode lead  35  and anode lead  45  carry electricity, creating a potential difference between cathode  30  and anode  40 . Gas separator  90  is a semi-permeable membrane that allows only hydrogen gas  80  to pass into pipe  100  and hydrogen collection tank  110 . 
         [0039]    Electrolytic fluid  20  is selected to have high hydrogen content as well as an appropriate conductor to optimize hydrogen production when a voltage is applied between anode  40  and cathode  30 . Reaction vessel  10  is selected to allow as much energy as possible to pass from laser  70  to electrolytic fluid  20 . Reaction vessel  10  may be made entirely of a material that is transparent to the wavelength of the laser beam or alternatively use a window that is transparent to the laser beam. 
         [0040]    In the use of the hydrogen generator of  FIG. 8 , electrolytic fluid  20  is held in reaction vessel  10 . Anode  40  and cathode  30  are submerged in electrolytic fluid  20 . Cathode lead  35  and anode lead  45  are attached to a power supply which is used to create a potential difference between cathode  30  and anode  40 . The potential difference between anode  40  and cathode  30  enables electrolysis to occur in electrolytic fluid  20  and results in the production of hydrogen gas  80 . Laser  70  irradiates electrolytic fluid  20  during electrolysis, increasing the rate of production of hydrogen gas  80 . 
         [0041]    Hydrogen gas  80  passes through gas separator  90  while other elements are prevented from passing through. Hydrogen gas  80  then passes into pipe  100  and hydrogen collection tank  110 . The purified hydrogen gas  120  that accumulates in the hydrogen collection tank  110  may be removed to a separate holding facility (not shown). 
         [0042]    Although the present invention has been described in detail, it will be apparent to those skilled in the art that many embodiments taking a variety of specific forms and reflecting changes, substitutions and alterations can be made without departing from the spirit and scope of the invention. The described embodiments illustrate the scope of the claims but do not restrict the scope of the claims.