Abstract:
The present invention relates to a diaphragm type electrolytic cell and process of production of commercial quantities of hydrogen from the electrolysis of water. The utilization of both alkaline and acidic electrolyte solutions within the electrolytic cell assists to increase the production of hydrogen and oxygen. Additionally, the efficiency of the electrolytic cell is increased due to the elimination of unwanted side reactions.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a diaphragm type electrolytic cell and process of production of commercial quantities of hydrogen from the electrolysis of water. 
       BACKGROUND ART 
       [0002]    There is an increased demand for clean and renewable energy sources to negate the adverse effects of utilizing hydrocarbon fuels and the release of carbon into the atmosphere. Hydrogen production is one such proposed solution as it is a clean fuel, producing only water when consumed. 
         [0003]    However, currently the majority of hydrogen, approximately 90%, is industrially produced from the gasification of fossil fuels such as natural gas, oil and coal. However, these processes still lead to the emission of carbon dioxides. Therefore, as hydrogen is not generally obtained from carbon oxide free sources, it is not carbon neutral energy source. 
         [0004]    Accordingly, there is a growing and renewed interest and need for the production of hydrogen through the electrolysis of water. The production of hydrogen through the electrolysis of water using diaphragm cells is well known. The use of diaphragm cells for the commercial production of hydrogen and oxygen, such as the Knowles and Stuart cells is well established. However, the disadvantage of these conventional diaphragm cells resides in the production of low energy efficiency and low capacity, with approximately 65% energy efficiency in the Knowles cell and approximately 55% in a Stuart cell. 
         [0005]      FIG. 1  illustrates a conventional diaphragm cell in water electrolysis where the standard electrode potential E°=1.229 volts and the electrolyte is the same in both the anode cell and cathode cell. However, the diaphragm in such conventional cells remains particularly problematic, wherein it increases impedance and agitation of the electrolyte to reduce over-voltage becomes difficult. The diaphragm must enable electrons to pass through with minimal resistance but must prevent mixing of oxygen and hydrogen produced at the anode and cathode respectively. 
         [0006]    In U.S. Pat. No. 7,326,329 and related United Kingdom Patent GB2409865 and Australian Patent 2004237840 titled “Commercial Production of Hydrogen from Water”, there is proposed a process for the production of hydrogen from the unipolar electrolysis of water, wherein more hydrogen is produced from the same energy to produce 1 mol of hydrogen from the electrolysis of water. 
         [0007]    U.S. Pat. No. 6,475,653 titled “Non-diffusion Fuel Cell and a Process of Using a Fuel Cell” attempts to address the recognized problematic issues with the diaphragm in electrolytic cells, wherein there is disclosed a more efficient hydrogen fuel cell that operates without a diaphragm or membrane. This allows clean electrical energy and transport energy to be derived from renewable energy such as solar and wind. 
         [0008]    Accordingly, it is an object of the present invention to provide an improved diaphragm electrolytic cell and an improved process of production of hydrogen from the electrolysis of water. 
         [0009]    The present invention provides higher rate of hydrogen production from the electrolysis of water using the structure of the conventional diaphragm type electrolytic cell, wherein a diaphragm is positioned between the anode and cathode or an electrolytic membrane or a salt bridge or semi-conductor or conductor between the anode and cathode. However, instead of utilizing the same electrolyte in both the anode cell and cathode cell, as that disclosed in U.S. Pat. No. 7,326,329, an acid electrolyte is passed through the cathode cell while an alkaline electrolyte is passed through the anode cell. Utilizing the Latimer equations, the standard electrode potential E° becomes −0.401 volts, compared to that of the conventional diaphragm cell where the standard electrode potential E°=1.229 volts to produce hydrogen and oxygen from the electrolysis of water. 
         [0010]    Notably, the efficiency of the electrolytic cell of the present invention is improved as only one of the electrodes of the cell is connected to the power supply. Advantageously, this eliminates any unwanted side reactions at the cathode and anode such as the production of oxygen and hydrogen respectively. Therefore, the efficiency of the electrolytic cell is improved. 
         [0011]    A further advantage of the present invention resides in the utilization of the acidic and alkaline electrolytes of the cell to produce hydrogen and oxygen. The acid electrolyte exiting the cathode cell, which contains an excess of OH −  ions that makes the acid electrolyte negative in electrical charge. Additionally, the alkaline electrolyte exiting the anode cell contains an excess of H +  ions that makes the alkaline electrolyte electrically positive. These two electrolytes are passed through another set of electrolytic cells with a diaphragm type structure, wherein the electrolytes will tend to neutralize each other resulting in a current flow. According to Faraday&#39;s Law, this will result the production of hydrogen and oxygen. 
         [0012]    Other objects and advantages of the present invention will become apparent from the following description, taking in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed. 
       SUMMARY OF THE INVENTION 
       [0013]    According to the present invention, although this should not be seen as limiting the invention in any way, there is proposed an electrolytic cell comprising:
       at least one anode compartment housing an anode electrode and alkaline electrolyte;   at least one cathode compartment housing a cathode electrode and acidic electrolyte;   at least one partition member separating the anode and cathode compartments;   a power source connected to either the anode electrode or cathode electrode; and   a modulator connected to the power source;
 
wherein the power source is activated, a pulsing current is applied to the anode electrode or cathode electrode through the modulator, such that the modulator generates and delivers the current in the form of at least one current pulse to the anode electrode or cathode electrode, thereby minimizing the onset of polarization and increasing the efficiency of the electrolytic cell.
       
 
         [0019]    Preferably, a base member is connected to the anode electrode. 
         [0020]    Preferably, the base member is comprised of the same material or coating as the anode electrode. 
         [0021]    Preferably, a base member is connected to the cathode electrode. 
         [0022]    Preferably, the base member is comprised of the same material or coating as the cathode electrode. 
         [0023]    Preferably, a conducting member extends between and connects the anode and cathode compartments. 
         [0024]    Preferably, the conducting member is selected from a group consisting of a salt bridge, semi-conductor or conductor member. 
         [0025]    Preferably, the partition separating the anode and cathode compartments is a porous diaphragm. 
         [0026]    Preferably, the partition separating the anode and cathode compartments is an electrolytic member. 
         [0027]    Preferably, the current pulse is applied at range between 1000 Hz to 20,000 Hz. 
         [0028]    Preferably, the anode and cathode electrodes are comprised of a porous material. 
         [0029]    Preferably, the anode and cathode electrodes are comprised of titanium mesh. 
         [0030]    Preferably, the anode and cathode electrodes are coated with a catalyst to promote oxidation and reduction respectively. 
         [0031]    Preferably, the catalyst is selected from a group consisting of platinum, platinum oxides, ruthenium, iridium, nickel, cobalt, molybdenum, alloys or oxides of these precious metals and base metals. 
         [0032]    Preferably, the anode and cathode compartment further houses a plurality of non-conductive members to facilitate the movement and flow of the alkaline electrolyte through the porous mesh structure of the anode and cathode electrodes. 
         [0033]    Preferably, the plurality of non-conductive members is comprised of plastic baffles. 
         [0034]    Preferably, the modulator generates and delivers the current in the form of a series of current pulses to the anode or cathode electrodes. 
         [0035]    Preferably, the power source is a DC power source at applies a DC current to the modulator. 
         [0036]    In an alternative form of the invention, there is proposed a process of production of hydrogen from the electrolysis of water using an electrolytic cell comprising the steps of:
       a. passing an alkaline electrolyte through an anode compartment housing an anode electrode to produce oxygen, wherein the anode electrode is connected to a power source;   b. passing an acidic electrolyte through a cathode compartment housing a cathode electrode to produce hydrogen, wherein the cathode is connected to the power source;   c. a base member connected to the anode and cathode electrodes;   d. the anode and cathode compartments are connected a semi-conductor or conductor member that extends between and connects the anode and cathode compartments;   e. connecting a modulator to the power source; and   f. activating the power source to apply a current to the anode electrode or cathode electrode through the modulator, such that the modulator generates and delivers the current in the form of at least one current pulse to the anode electrode or cathode electrode, thereby minimizing the onset of polarization and increasing the efficiency of the electrolytic cell.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]    For a better understanding of the present invention and associated method of use, it will now be described with respect to the preferred embodiment which shall be described herein with reference to the accompanying drawings wherein: 
           [0044]      FIG. 1  illustrates a conventional diaphragm cell used in the electrolysis of water where the standard electrode potential E°=1.229 volts and the electrolyte is the same in both the anode compartment and cathode compartment; 
           [0045]      FIG. 2  illustrates a basic electrolytic cell disclosed in U.S. Pat. No. 7,326,329; 
           [0046]      FIG. 3A  illustrates one embodiment of the electrolytic cell of the present invention utilizing a conventional diaphragm to separate the anode and cathode compartment; 
           [0047]      FIG. 3B  illustrates a further embodiment of the electrolytic cell of the present invention utilizing an electrolytic membrane to separate the anode and cathode compartment instead of the diaphragm; 
           [0048]      FIG. 3C  illustrates a further embodiment of the electrolytic cell of the present invention, utilizing the same structure as the diaphragm cell of  FIG. 3A  but wherein the anode and cathode compartment is separated by a non-conducting partition; 
           [0049]      FIG. 4A  is a plan view of the electrolytic system of the present invention having an electrolytic section and a neutralization section; 
           [0050]      FIG. 4B  is a cross sectional view of the electrolytic section of  FIG. 4A ; 
           [0051]      FIG. 4C  is a cross sectional view of the neutralization cell of  FIG. 4A ; 
           [0052]      FIG. 5A  illustrates a cross sectional view of a further embodiment of the electrolytic cell of the present invention wherein multiple electrolytic cells are structured together to produce a higher capacity system; and 
           [0053]      FIG. 5B  illustrates a plan view of the multiple electrolytic cells. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0054]      FIG. 1  illustrates a conventional diaphragm cell  1  used in the electrolysis of water, wherein the standard electrode potential E°=1.229 volts. The cell  1  comprises of an anode compartment  3  and a cathode compartment  5 . A diaphragm  7  separates the anode  3  and cathode  5  compartments. 
         [0055]    The anode compartment  3  contains and houses an anode electrode  9  and the cathode compartment  5  contains and houses a cathode electrode  11 . The electrolyte solution  13  in both the anode  3  and cathode  5  compartments is the same. 
         [0056]    Both the anode  9  and cathode  11  electrodes are connected to a power source  15 , being a DC power source. 
         [0057]    However, as outlined above the shortcoming with this type of conventional diaphragm cell  1  resides in the diaphragm  7 , wherein it increases impedance and makes it difficult to agitate the electrolyte solution  11  to reduce over-voltage at the anode  9  and cathode  11  electrodes. The diaphragm  7  must allow electrons to pass through, as indicated at arrows A and B with the least resistance whilst preventing the mixing of the oxygen produced at the anode electrode  9  with the hydrogen produced at the cathode electrode  11 . 
         [0058]      FIG. 2  illustrates the basic electrolytic cell  17  set up for the unipolar electrolysis of water disclosed in U.S. Pat. No. 7,326,329. Here two separate circuits are formed, one being of a primary circuit comprising a primary anode cell  19   a  and a primary cathode cell  19   b,  and a secondary circuit comprising a secondary anode cell  21   a  and a secondary cathode cell  21   b.  The primary circuit consists of an alkaline electrolyte  23  and the secondary circuit consists of an acidic electrolyte  25 . The standard electrode potential E° in the primary anode cell  19   a  to produce hydrogen and oxygen is −0.401 volts. There is greater hydrogen production in the secondary cathode cell  21   b.    
         [0059]    The positive terminal of a DC power source  15  is connected to the anode electrode  27  of the primary anode cell  19   a  and the negative terminal is connected to the cathode electrode  29  of the primary cathode cell  19   b.  The solution electrodes electrically connect the alkaline electrolyte  23  of the primary anode cell  19   a  to the acidic electrolyte  25  of the primary cathode cell  19   b.  At the primary anode cell  19   a,  the following reaction occurs: 
         [0000]      2OH − −2e − →H 2 O+½O 2  
 
         [0060]    The alkaline electrolyte  29  exiting from the primary anode cell  19   a  contains excess hydrogen ions so that this electrolyte  29  is positively charged. At the primary cathode cell  19   b  containing the acidic electrolyte  25 , the following reaction occurs: 
         [0000]      2H + +2e − →H 2  
 
         [0061]    The acidic electrolyte  31  exiting from the primary cathode cell  19   b  has excess hydroxyl ions so that this electrolyte  31  is negatively charged. 
         [0062]    When the alkaline electrolyte  29  and acidic electrolyte  31  are passed through the secondary circuit comprising of the secondary anode cell  21   a  and a secondary cathode cell  21   b,  the electrolytes  29 ,  31  are discharged, causing current to flow from the secondary anode cell  21   a  to the secondary cathode cell  21   b  through a conductor  33 . This results in further production oxygen from the secondary anode cell  21   a  and hydrogen from the secondary cathode cell  21   b.  The neutralized electrolytes  35  and  37  are recycled to the respective primary anode cell  19   a  and primary cathode cell  19   b.    
         [0063]      FIGS. 3A to 3C  illustrate differing embodiments of the electrolytic cell  39  of the present invention. 
         [0064]      FIG. 3A  illustrates an embodiment of the electrolytic cell  39  utilizing a conventional diaphragm cell formed of an anode compartment  41  and a cathode compartment  43 , separated by a diaphragm  45 . The anode compartment  41  houses an anode electrode  47  and an alkaline electrolyte solution  49  flows through the anode compartment  41 . The cathode compartment  43  houses a cathode electrode  51  and an acidic electrolyte solution  53  flows through the cathode compartment  43 . The anode  47  and cathode  51  electrodes are connected to a power source  55 . The power source  55  being a DC power supply. 
         [0065]    A modulator  57  is connected to the DC power source  55  and serves to generate and deliver the current from the DC power source  55  to the anode  47  or cathode  51  electrodes in the form of at least one current pulse. The modulator  57  is adapted to generate and deliver the current in a series of current pulses to the anode  47  or cathode  51  electrodes. 
         [0066]    The modulator  57  is a major and advantageous feature of the present invention. In applying a current pulse or series of current pulses to either the anode  47  or cathode  51  electrodes, this advantageously minimizes the onset of polarization in the electrolytic cell  39  and therefore minimizes the adverse affect on the efficiency of the electrolytic cell  39 . 
         [0067]    The current pulse is applied to either the anode  47  or cathode  51  electrodes at a range of  1000  to  20 , 000  Hertz and the standard electrode potential is E o =−0.401 volts. 
         [0068]      FIG. 3B  illustrates a further embodiment of the electrolytic cell  39 , however in place of the diaphragm  45  as in  FIG. 3A , an electrolytic membrane  59  separates the anode compartment  41  and a cathode compartment  43 . 
         [0069]      FIG. 3C  illustrates further embodiment of the electrolytic cell  39 . A non-conductor wall  61  separates the anode compartment  41  and a cathode compartment  43 . 
         [0070]    Obviously for any electrolytic cell to function properly, there must be a complete electrical circuit. In the embodiment illustrated in  FIG. 3C , the circuit is completed through use of a conducting member  63  comprising of either a salt bridge, a semi-conductor plate or a conductor plate. It is readily appreciated that the conducting member  63  may comprise of any suitable member or means known within the art that will enable and maintain sufficient contact between the anode compartment  41  and a cathode compartment  43 . 
         [0071]    Further, the anode  47  and cathode  51  electrodes are connected to a base member  65 . In the illustrated embodiment, the base member  65  is flat plate attached to the bottom of the anode  47  and cathode  51  electrodes. This base member  65  comprises of the same material or coating as the respective anode  47  and cathode  51  electrodes to which it is attached. 
         [0072]    The current flow through the electrolytic cell  39  of  FIG. 3C  is such that the current flows from the DC power source  55 , to the modulator  57 , to the cathode electrode  51 , to the base member  65  attached to the cathode electrode  51 , through conducting member  63  comprising of either a salt bridge, semi-conductor or conductor plate, to the base member  65  attached to the anode electrode  47 , to the anode electrode  47 , back to the DC power source  55 . 
         [0073]    The electrolytic cell  39  illustrated in  FIG. 3C  is the preferred embodiment of the present invention as it offers several advantages including:
       a. The least resistance or impedance;   b. The materials exposed to the alkaline and acidic electrolytes can be selected to withstand high and low pH of the respective electrolytes; and   c. It offers the highest possible capacity for commercial operation and production of hydrogen.       
 
         [0077]    It would be readily appreciated that any number of anode  47  and cathode  51  electrodes can be attached to the base member  63  in the electrolytic cell  39  illustrated in  FIG. 3C , so as to increase the capacity of the electrolytic cell  39  and system. 
         [0078]      FIG. 4A  is a plan view of an electrolytic cell of the present invention, utilizing two electrolytic cells, a first electrolytic cell  67  and a second electrolytic cell  71 , each having an anode compartment  41 ,  73  and a cathode compartment  43 ,  75  separated by a diaphragm  45 . A first electrolytic cell  67  serves as the electrolytic section where electric power is applied. The first electrolytic cell  67  comprises of an anode electrode  47  and a cathode electrode  51 . The anode  47  and cathode  51  electrodes are formed of a porous material such as expanded mesh or similar construction. 
         [0079]    Each of the anode compartments  41 ,  73  and a cathode compartments  43 ,  75  further comprise and house a plurality of non-conductive members  69 . The non-conductive members  69  being a plurality of plastic baffles. 
         [0080]    The non-conductive members  69  assist to facilitate the movement and flow of the alkaline  49 ,  83  and acidic  53 ,  81  electrolyte solutions throughout the anode compartments  41 ,  73  and a cathode compartments  43 ,  75 . The non-conductive members  69  force the alkaline  49 ,  83  and acidic  53 ,  81  electrolyte solutions in and out of the porous mesh structures of anode electrodes  47 ,  77  and a cathode electrodes  51 ,  79 . 
         [0081]    The anode electrodes  47 ,  77  and cathode electrodes  51 ,  79  for example, can be formed from titanium mesh. Further, the anode electrodes  47 ,  77  and a cathode electrodes  51 ,  79  may be coated with a suitable catalyst to favour the reaction that is desired at the respective anode electrodes  47 ,  77  and a cathode electrodes  51 ,  79 . 
         [0082]    For example, the anode electrodes  47 ,  77  that produce oxygen, can be coated with a catalyst made form oxides of ruthenium and iridium or platinum or mixtures. Similarly, the cathode electrodes  51 ,  79  may be coated with a catalyst having different ratios of the platinum group oxides. 
         [0083]    A second electrolytic cell  71  serves as a neutralization section, comprising of an anode compartment  73  and a cathode compartment  75  and houses an anode electrode  77  and a cathode electrode  79 , respectively. The second electrolytic cell  71  allows the neutralization of the negatively charged acidic electrolyte solution  81  and the positively charged alkaline electrolyte solution  83 , exiting from the first electrolytic cell  67 . As a result, current flows between the anode electrode  77  and the cathode electrode  79  and according to Faraday&#39;s Law, chemical reactions occur at the anode electrode  77  and the cathode electrode  79 . 
         [0084]    The current flows in the first electrolytic cell  67  of  FIG. 4A  are shown in  FIG. 4B , which is a cross section of the first electrolytic cell  67 . The current flows from the DC source  55  to the anode electrode  47 , through the diaphragm  45  and then to the cathode electrode  51  to the DC power source  55 . 
         [0085]      FIG. 4C  is a cross section of the second electrolytic cell  71 , being the neutralization cell and depicts the formation of hydrogen at the cathode electrode  79 , while oxygen is produced at the anode electrode  77 , according to the chemical formulas shown. 
         [0086]    The acidic electrolyte solution  81  exiting from the cathode compartment  43  of the first electrolytic cell  67  is fed into the inlet  85  of the anode compartment  73  of the second electrolytic cell  71 . The alkaline electrolyte solution  83  exiting the anode compartment  41  of the first electrolytic cell  67  is fed to the rear inlet  87  of the cathode compartment  75  of the second electrolytic cell  71 . 
         [0087]    This set up will allow a better operation of the second electrolytic cell  71  as the potential difference of the alkaline  83  and acidic  81  electrolyte solutions is evened up rather than the strongest electrolyte solutions neutralizing each other and resulting in the weakened electrolyte solutions towards the end of the second electrolytic cell  71  having reduced potential to neutralize each other. 
         [0088]      FIGS. 4A to 4C  illustrate the process of electrolyzing water for increased hydrogen production. Electric power, through a DC power source  55  is applied through a modulator  57  to the anode electrode  47  housed within the anode compartment  41  of the first electrolytic cell  67 , which contains the alkaline electrolyte solution  49  and to the cathode electrode  51  housed within the cathode compartment  43 , which contains the acidic electrolyte solution  53 , with a membrane or diaphragm  45  separating between the anode  47  and cathode  51  electrodes. The anode  47  and cathode  51  electrodes are made of titanium mesh as an example and coated with a catalyst such as platinum, platinum group oxides or metals such as nickel, cobalt, molybdenum or alloys or oxides of these precious and base metals. 
         [0089]    Each of the anode compartments  41 ,  73  and a cathode compartments  43 ,  75  comprise of a plurality of non-conductive members  69 , being a plurality of plastic baffles. These non-conductive members  69  are used to guide the alkaline  49 ,  83  and acidic  53 ,  81  electrolyte solutions, in and out of the anode electrodes  47 ,  77  and a cathode electrodes  51 ,  79 , as the electrolyte solutions move from one end to the other in the respective anode compartments  41 ,  73  and a cathode compartments  43 ,  75 . 
         [0090]    It is readily appreciated that there may be more than  1  set of anode electrodes  47 ,  77  and a cathode electrodes  51 ,  79  utilized in the first electrolytic  67  and second electrolytic  71  cells of the present invention. The electrolytic membrane  59  is commercially available and the diaphragm  45  may be made from an acid and alkali resistant material such as Teflon or polyurethane. 
         [0091]    The pressure in the first electrolytic  67  and second electrolytic  71  cells may range from atmospheric up to  20  atmospheres and the temperature may range from 15° C. up to 200° C. The electrolyte solutions utilized in the first electrolytic  67  and second electrolytic  71  cells may include an inorganic acid and base, or weaker acid such as boric acid and weaker alkaline such as ammonia. 
         [0092]    The electrolyte solutions  49 ,  53  exiting the first electrolytic cell  67  are positively and negatively charged and these charged electrolyte solutions  49 ,  53  are passed through the second electrolytic cell  71  where the electrolyte  49 ,  53  are short circuited leading the current flowing as shown in  FIG. 4 . Faraday&#39;s law provides that when current flows, substances are produced at the anode  77  and cathode  79  electrodes. In this case, hydrogen is produced at the anode  77  electrodes and oxygen is produced at the  79  cathode electrodes. 
         [0093]    This increases the production of hydrogen so that theoretically, based on the voltage of 0.4012 volts at the first electrolytic cell  67 , 2 moles of hydrogen are produced by applying only 0.401 volts at the primacy electrolytic cell  67 . By calculation theoretically, 6.13 times more hydrogen is produced for the same energy used to produce 1 mol of hydrogen using the conventional electrolytic cell, in either alkaline electrolyte or acid electrolyte. 
         [0094]      FIG. 5A  illustrates a cross sectional view of a further embodiment of the electrolytic cell of the present invention wherein multiple electrolytic cells  67  are structured together to produce a higher capacity system.  FIG. 5B  illustrates the plan view of the multiple electrolytic cells  67 . 
         [0095]    The electrolytic cells  67  could operate at atmospheric pressure or a moderate pressure no higher than 20 bars and a temperature no higher than 200° C. 
         [0096]    The preferred embodiment of the present invention is illustrated in  FIG. 3C , wherein the configuration offers a high capacity. In this embodiment the complete electrical circuit is made possible by the base member  65  connected to anode  47  and cathode  51  electrodes and a conducting member  63  in the form of either a salt bridge, a semi-conductor plate or a conductor plate, located at the bottom of the anode  41  and cathode  43  compartments of the electrolytic cell  67 .