Patent Application
20160122886
Embodiments of the present invention relate generally to electrode compositions, apparatuses and methods for removing nitrogen oxide.
Nitrogen oxide (NOx, including NO and/or NO2) is undesirable for the environment and thus industry has considered and implemented various techniques to reduce NOx emissions. Some approaches have been proposed to electrochemically reduce nitrogen oxide. However, currently available electrode compositions, apparatuses and methods still need improvements.
Therefore, it is desirable to provide new electrode compositions, apparatuses and methods for removing nitrogen oxide.
In one aspect, embodiments of the invention relate to an electrode composition for removing nitrogen oxide, comprising: a catalytic material and an adsorption material, wherein the adsorption material is a perovskite material of formula AaBbO3-δ, wherein 0.9<a≦1.2; 0.9<b≦1.2; −0.5<δ<0.5; A comprises a first element and optionally a second element, the first element is selected from calcium (Ca), strontium (Sr), barium (Ba), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and any combination thereof, the second element is selected from yttrium (Y), bismuth (Bi), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and any combination thereof; and B is selected from silver (Ag), gold (Au), cadmium (Cd), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), dysprosium (Dy), erbium (Er), europium (Eu), ferrum (Fe), gallium (Ga), gadolinium (Gd), hafnium (Hf), holmium (Ho), indium (In), iridium (Ir), lanthanum (La), lutetium (Lu), manganese (Mn), molybdenum (Mo), niobium (Nb), neodymium (Nd), nickel (Ni), osmium (Os), palladium (Pd), promethium (Pm), praseodymium (Pr), platinum (Pt), rhenium (Re), rhodium (Rh), ruthenium (Ru), antimony (Sb), scandium (Sc), samarium (Sm), tin (Sn), tantalum (Ta), terbium (Tb), technetium (Tc), titanium (Ti), thulium (Tm), vanadium (V), tungsten (W), yttrium (Y), ytterbium (Yb), zinc (Zn), zirconium (Zr), and any combination thereof.
In another aspect, embodiments of the invention relate to an apparatus for removing nitrogen oxide, comprising: a gas source for providing a gas stream comprising nitrogen oxide; and a device in fluid communication with the gas source and comprising: a first electrode; an opposite second electrode comprising a catalytic material and an adsorption material, wherein the adsorption material is a perovskite material of formula AaBbO3-δ, wherein 0.9<a≦1.2, 0.9<b≦1.2, −0.5<δ<0.5, A comprises a first element and optionally a second element, the first element is selected from calcium (Ca), strontium (Sr), barium (Ba), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and any combination thereof, the second element is selected from yttrium (Y), bismuth (Bi), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and any combination thereof, and B is selected from silver (Ag), gold (Au), cadmium (Cd), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), dysprosium (Dy), erbium (Er), europium (Eu), ferrum (Fe), gallium (Ga), gadolinium (Gd), hafnium (Hf), holmium (Ho), indium (In), iridium (Ir), lanthanum (La), lutetium (Lu), manganese (Mn), molybdenum (Mo), niobium (Nb), neodymium (Nd), nickel (Ni), osmium (Os), palladium (Pd), promethium (Pm), praseodymium (Pr), platinum (Pt), rhenium (Re), rhodium (Rh), ruthenium (Ru), antimony (Sb), scandium (Sc), samarium (Sm), tin (Sn), tantalum (Ta), terbium (Tb), technetium (Tc), titanium (Ti), thulium (Tm), vanadium (V), tungsten (W), yttrium (Y), ytterbium (Yb), zinc (Zn), zirconium (Zr), and any combination thereof; an electrolyte (103, 203, 303, 403) between the first and the second electrodes; and a power supply (104, 204, 304, 404) for applying an electrical current to the first and the second electrodes to remove nitrogen oxide.
In yet another aspect, embodiments of the invention relate to a method for removing nitrogen oxide, comprising: contacting a gas stream comprising nitrogen oxide with a device, the device comprising: a first electrode; an opposite second electrode comprising a catalytic material and an adsorption material; an electrolyte between the first and the second electrodes; and, a power supply; and applying an electrical current from the power supply to the first and the second electrodes to remove nitrogen oxide; wherein the adsorption material is a perovskite material of formula AaBbO3-δ, wherein 0.9<a≦1.2; 0.9<b≦1.2; −0.5<δ<0.5; A comprises a first element and optionally a second element, the first element is selected from calcium (Ca), strontium (Sr), barium (Ba), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and any combination thereof, and the second element is selected from yttrium (Y), bismuth (Bi), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and any combination thereof and B is selected from silver (Ag), gold (Au), cadmium (Cd), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), dysprosium (Dy), erbium (Er), europium (Eu), ferrum (Fe), gallium (Ga), gadolinium (Gd), hafnium (Hf), holmium (Ho), indium (In), iridium (Ir), lanthanum (La), lutetium (Lu), manganese (Mn), molybdenum (Mo), niobium (Nb), neodymium (Nd), nickel (Ni), osmium (Os), palladium (Pd), promethium (Pm), praseodymium (Pr), platinum (Pt), rhenium (Re), rhodium (Rh), ruthenium (Ru), antimony (Sb), scandium (Sc), samarium (Sm), tin (Sn), tantalum (Ta), terbium (Tb), technetium (Tc), titanium (Ti), thulium (Tm), vanadium (V), tungsten (W), yttrium (Y), ytterbium (Yb), zinc (Zn), zirconium (Zr), and any combination thereof.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, wherein:
Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms “first”, “second”, and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The use of “including”, “comprising” or “having” and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.
In the specification and the claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Moreover, the suffix “(s)” as used herein is usually intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term.
As used herein, the term “or” is not meant to be exclusive and refers to at least one of the referenced components (for example, a material) being present and includes instances in which a combination of the referenced components may be present, unless the context clearly dictates otherwise.
Reference throughout the specification to “some embodiments”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the invention is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described inventive features may be combined in any suitable manner in the various embodiments.
Embodiments of the present invention relate to electrode compositions, apparatuses and methods for removing nitrogen oxide.
As used herein the term “nitrogen oxide” or the like refers to a gas comprising molecules including both oxygen and nitrogen, for example, nitrogen monoxide, nitrogen dioxide, or a combination thereof.
Please refer to
The gas stream comprising nitrogen oxide may be from a variety of gas sources. In some embodiments, the gas sources are exhaust gas sources from gas turbines, internal combustion engines, or combustion devices. In some embodiments, the gas source comprises a conduit, a channel, or a tube for the passage of the gas stream. In some embodiments, besides nitrogen oxide, the gas stream 12, 22, 32, 42 comprises other gases, such as oxygen.
In some embodiments, the device 100, 200, 300, 400 includes a first electrode 101, 201, 301, 401, an opposite second electrode 102, 202, 302, 402, an electrolyte 103, 203, 303, 403 between the first and the second electrodes, and a power supply 104, 204, 304, 404 for applying an electrical current from the power supply 104, 204, 304, 404 to the first and the second electrodes to remove nitrogen oxide. In some embodiments, the powder supply 104, 204, 304, 404 has a controller 114, 214, 314, 414 for controlling the electrical current.
In some embodiments, nitrogen oxide can be directly decomposed in the device 100, 200, 300, 400 before an electrical current is applied. When a gas stream 12, 22, 32, 42 comprising nitrogen oxide is contacted with the device 100, 200, 300, 400, nitrogen oxide is removed in the second electrode 102, 202, 302, 402 in a reaction such as: NO=½N2+½O2.
However, as can be seen from examples described hereafter, when the electrical current is applied, besides the direct decomposition of NO described above, nitrogen oxide is removed in the cathode in an electrochemical reaction of NO+2e→½N2+O2-. The oxygen ions produced thereby travel from the cathode through the electrolyte into the anode to be oxidized into oxygen in a reaction of O2--2e→½O2. A total reaction in the device is: NO=½N2+½O2. The removal rate of nitrogen oxide is increased.
The removal of nitrogen oxide may be at any suitable temperature. In some embodiments, the step of applying the electrical current is at a temperature in a range from about 300° C. to about 1000° C.
The electrical current may be any electrical current that can be used to decompose nitrogen oxide at a conversion rate higher than that of before an electrical current is applied. In some embodiments, the electrical current is direct current. In some embodiments, the electrical current is applied by jumping to the designed value directly. In some embodiments, the electrical current is applied by sweeping to the designed value slowly.
The controller 114, 214, 314, 414 may be any mechanism that controls the on and off and/or increasing and decreasing of the electrical current. In some embodiments, the controller is a switch for turning on and off the electrical current.
In some embodiments, the first electrode 101, 201, 301, 401 is an anode. The anode may include any material that catalyzes the oxidization of oxygen ions to oxygen, and any other materials that can be used in the anode. In some embodiments, the anode comprises a manganite, such as lanthanum strontium manganite (LSM), a non-limiting exemplary composition of which includes (La0.8Sr0.2)0.95MnO3; a combination of platinum and yttria stabilized zirconia; a combination of platinum and gadolinium-doped ceria; or any combination thereof.
In some embodiments, the second electrode 102, 202, 302, 402 is a cathode. Besides the catalytic material and the adsorption material, the electrode composition of the second electrode 102, 202, 302, 402 may have any other materials that can be used in the cathode. As can be seen from examples incorporated hereafter, the adsorption material according to embodiments of the present invention significantly improved the removal rate of nitrogen oxide.
The catalytic material may be any material that catalyzes the decomposition of nitrogen oxide. In some embodiments, the catalytic material comprises a manganite, such as lanthanum strontium nickel manganite (LSNM), an exemplary composition of which includes, but is not limited to, La0.6Sr0.4Ni0.3Mn0.7O3; nickel oxide (NiO); a combination of LSNM and gadolinium doped ceria (GDC, e.g., Gd0.1Ce0.9O1.95); a combination of LSNM and scandia stabilized zirconia (SSZ, e.g., Zr0.89Sc0.1Ce0.01O2-x); a combination of LSNM, NiO and SSZ; a combination of NiO and SSZ; a combination of platinum with yttria-stabilized zirconia; a combination of platinum with GDC; or any combination thereof.
The adsorption material adsorbs nitrogen oxide. As used herein the term “perovskite material” or any variation thereof refers to but is not limited to any material having an ABO3 perovskite structure and being of formula AaBbO3-δ, wherein 0.9<a≦1.2; 0.9<b≦1.2; −0.5<δ<0.5; A comprises a first element and optionally a second element, the first element is selected from calcium (Ca), strontium (Sr), barium (Ba), lithium (Li), sodium (Na), potassium (K), rubidium (Rb) and any combination thereof, the second element is selected from yttrium (Y), bismuth (Bi), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and any combination thereof; and B is selected from silver (Ag), gold (Au), cadmium (Cd), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), dysprosium (Dy), erbium (Er), europium (Eu), ferrum (Fe), gallium (Ga), gadolinium (Gd), hafnium (Hf), holmium (Ho), indium (In), iridium (Ir), lanthanum (La), lutetium (Lu), manganese (Mn), molybdenum (Mo), niobium (Nb), neodymium (Nd), nickel (Ni), osmium (Os), palladium (Pd), promethium (Pm), praseodymium (Pr), platinum (Pt), rhenium (Re), rhodium (Rh), ruthenium (Ru), antimony (Sb), scandium (Sc), samarium (Sm), tin (Sn), tantalum (Ta), terbium (Tb), technetium (Tc), titanium (Ti), thulium (Tm), vanadium (V), tungsten (W), yttrium (Y), ytterbium (Yb), zinc (Zn), zirconium (Zr), and any combination thereof.
In some embodiments, the perovskite material may be of formula n(AaBbO3-δ), in which n=2, 3, 4, 8, and etc., and the formula AaBbO3-δ is the simplified form thereof.
In some embodiments, in the ABO3 perovskite structure, A cations are surrounded by twelve anions in cubo-octahedral coordination, B cations are surrounded by six anions in octahedral coordination and oxygen anions are coordinated by two B cations and four A cations. In some embodiments, the ABO3 perovskite structure is built from corner-sharing BO6 octahedra. In some embodiments, the ABO3 perovskite structure includes distorted derivatives. The distortions may be due to rotation or tilting of regular, rigid octahedra or due to the presence of distorted BO6 octahedra. In some embodiments, the ABO3 perovskite structure is cubic. In some embodiments, the ABO3 perovskite structure is hexagonal.
In some embodiments, A only comprises the first element. In some embodiments, A comprises a combination of the first element and the second element.
In some embodiments, the first element is selected from potassium (K), barium (Ba), strontium (Sr), and any combination thereof.
The second element may be a single element or a combination of elements selected from yttrium (Y), bismuth (Bi), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).
Likewise, B may be a single element or a combination of elements selected from silver (Ag), gold (Au), cadmium (Cd), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), dysprosium (Dy), erbium (Er), europium (Eu), ferrum (Fe), gallium (Ga), gadolinium (Gd), hafnium (Hf), holmium (Ho), indium (In), iridium (Ir), lanthanum (La), lutetium (Lu), manganese (Mn), molybdenum (Mo), niobium (Nb), neodymium (Nd), nickel (Ni), osmium (Os), palladium (Pd), promethium (Pm), praseodymium (Pr), platinum (Pt), rhenium (Re), rhodium (Rh), ruthenium (Ru), antimony (Sb), scandium (Sc), samarium (Sm), tin (Sn), tantalum (Ta), terbium (Tb), technetium (Tc), titanium (Ti), thulium (Tm), vanadium (V), tungsten (W), yttrium (Y), ytterbium (Yb), zinc (Zn), and zirconium (Zr). In some embodiments, B is selected from yttrium (Y), cobalt (Co), cerium (Ce), zirconium (Zr), ferrum (Fe), and any combination thereof.
In some embodiments, the perovskite material comprises BaZr0.1Ce0.7Y0.2O3, Ba0.5Sr0.5Co0.8Fe0.2O3, Ba0.5Sr0.4K0.1Co0.8Fe0.2O3, Ba0.9K0.1Zr0.3Ce0.5Co0.1Y0.1O3, or any combination thereof. For example, for BaZr0.1Ce0.7Y0.2O3, A is Ba, a=1, B is a combination of Zr, Ce and Y, b=1, and δ=0. For Ba0.5Sr0.5Co0.8Fe0.2O3, A is a combination of Ba and Sr, a=1, B is a combination of Co and Fe, b=1, and δ=0. For Ba0.5Sr0.4K0.1Co0.8Fe0.2O3, A is a combination of Ba, Sr and K, a=1, B is a combination of Co and Fe, b=1, and δ=0. For Ba0.9K0.1Zr0.3Ce0.5Co0.1Y0.1O3, A is a combination of Ba and K, a=1, B is a combination of Zr, Ce, Co and Y, b=1, and δ=0.
In some embodiments, as is shown in
In some embodiments, the apparatus comprises a current collector (not shown). The current collector may be made of any electrically conductive materials such as metals or metal alloys and be in any forms suitable for use in supplying or withdrawing electrical current from the electrodes. In some embodiments, the current collector is made of nickel. In some embodiments, the current collector is in the form of mesh, porous film, foam, or any combination thereof. In some embodiments, the current collector is nickel foam. In some embodiments, a porosity of a porous metallic current collector is in a range from about 25% to about 99%.
In some embodiments, the current collector is a mechanical support for the first and the second electrodes.
In some embodiments, the current collector is disposed over the second electrode, either directly, or with one or more intermediate layers therebetween.
The electrolyte may include any material that has a suitable level of oxygen ion conductivity and any other suitable material. In some embodiments, the electrolyte comprises GDC, such as Gd0.1Ce0.9O1.95; SSZ, such as Zr0.89Sc0.1Ce0.01O2-x; oxide materials from the barium-zirconium-cerium-yttrium (BZCY) family, such as BaZr0.7Ce0.2Y0.1O3; or any combination thereof. In some embodiments, the electrolyte includes bismuth oxide, zeolite, alumina, silica, aluminum nitride, SiC, nickel oxide, iron oxide, copper oxide, calcium oxide, magnesium oxide, zinc oxide, aluminum, yttria stabilized zirconia, scandia stabilized zirconia, perovskite oxides, lanthanum strontium calcium manganese, lanthanum silicate, Nd9.33(SiO4)6O2, AlPO4, B2O3, and R2O (R stands for an alkaline metal), AlPO4—B2O3—R2O glass which carries out the main component of Na and the K, porous SiO2—P2O5 system glass, Y addition BaZrO3, Y addition SrZrO3 and Y addition SrTiO3, strontium doping lanthanum manganite, a lanthanum strontium cobalt iron oxide (La—Sr—Co—Fe system perovskite type oxide), a La—Sr—Mn—Fe system perovskite type oxide, a Ba—Sr—Mn—Fe system perovskite type oxide, or any combination thereof.
A dense electrolyte is preferred for mitigating the mixing of the gases of the cathode and the anode and reducing the ohmic resistance of the electrolyte. Low ohmic resistance is preferred for energy saving in the NOx removal process.
Each of the electrode, the electrolyte, the current collector, and the adsorption layer may be a single layer or comprise more than one layer depending on the needed flexibility, gas diffusion capability, and porosity. Multiple layers may be the same as or different from each other and connected in suitable ways. In each single layer, the composition may be the same or different through at least one dimension thereof.
The apparatus may be of any configuration suitable for removing nitrogen oxide. In some embodiments, as is shown in
The device described herein may be prepared by providing a current collector and applying sequentially different layers on both sides thereof, or providing any of other layers and laminating different layers on either/both sides thereof. The layers may be formed/applied/laminated by any suitable means such as extruding, dip coating, spraying and printing.
The following examples are included to provide additional guidance to those of ordinary skill in the art in practicing the claimed invention. These examples do not limit the invention as defined in the appended claims.
La2O3, SrCO3, Mn(AC)2.4H2O and NiO were ball milled in EtOH and calcined at 1300° C. for 8 hours to prepare La0.6Sr0.4Ni0.3Mn0.7O3. X-ray diffraction (XRD) analyses confirmed that a pure phase of La0.6Sr0.4Ni0.3Mn0.7O3 was obtained.
The BaZr0.1Ce0.7Y0.2O3 powder was prepared by solid-state reaction method. Stoichiometric amounts of high-purity barium carbonate, zirconium oxide, yttrium oxide, and cerium oxide powders (all from sinopharm chemical reagent Co., Ltd. (SCRC), Shanghai, China) were mixed in ethanol and ball-milled for about 16 hours. The resultant mixtures were then dried and calcined at about 1450° C. in air for about 6 hours to form the BaZr0.1Ce0.7Y0.2O3 powder. The calcined powder was mixed with alcohol and was ball milled for about 16 hours. After the alcohol was dried, fine BaZr0.1Ce0.7Y0.2O3 powder (d50=1.5 micron) was prepared.
BaZr0.1Ce0.7Y0.2O3 powder and carbon black were respectively put into a thermo gravimetric analyzer (TGA) in a 200 ml/min gas stream comprising 100 ppm NO and 16% O2, and balanced with N2. The temperature ramped up at 5° C./min to 850° C. A mass spectrometer (HPR20, Hiden Analytical, Warrington, UK) was coupled with the TGA to monitor NO/NO2 in the exhaust from the TGA. The intensity of NO signals (arbitrary unit) at different temperatures in the exhaust from the TGA respectively with BaZr0.1Ce0.7Y0.2O3 powder and carbon black are shown in
Ba0.5Sr0.5Co0.8Fe0.2O3 powder, Ba0.5Sr0.4K0.1Co0.8Fe0.2O3 powder and Ba0.9K0.1Zr0.3Co0.5Co0.1Y0.1O3 powder were prepared in similar ways as that of BaZr0.1Ce0.7Y0.2O3 powder described in example 2.
Ba0.5Sr0.5Co0.8Fe0.2O3 powder, Ba0.5Sr0.4K0.1Co0.8Fe0.2O3 powder, and Ba0.9K0.1Zr0.3Ce0.5Co0.1N0.1O3 powder (20 mg) were respectively mixed with 2 mg carbon black and put into a thermo gravimetric analyzer (TGA) in a 200 ml/min gas stream comprising 100 ppm NO and 16% O2, and balanced with N2. The temperature ramped up at 5° C./min to 850° C. A mass spectrometer (HPR20, Hiden Analytical, Warrington, UK) was coupled with the TGA to monitor NO/NO2 in the exhaust stream from the TGA. The intensities of NO signals at different temperatures in the exhaust streams from the TGA with the mixtures of carbon black respectively with Ba0.5Sr0.5Co0.8Fe0.2O3 powder, Ba0.5Sr0.4K0.1Co0.8Fe0.2O3 powder, and Ba0.9K0.1Zr0.3Ce0.5Co0.1N0.1O3 powder are shown in
Three 7.5 cm long one-end open (La0.8Sr0.2)0.95MnO3 tubes were fabricated by extruding. The outer diameter of each tube was about 1 cm, and the inner diameter was about 0.7 cm.
A dense Zr0.89Sc0.1Ce0.01O2-x electrolyte film was coated on each (La0.8Sr0.2)0.95MnO3 tube and was co-sintered with the (La0.8Sr0.2)0.95MnO3 tube at 1250° C.
A layer of La0.6Sr0.4Ni0.3Mn0.7O3, BaZr0.1Ce0.7Y0.2O3 and Zr0.89Sc0.1Ce0.01O2-x (La0.6Sr0.4Ni0.3Mn0.7O3—BaZr0.1Ce0.7Y0.2O3—Zr0.89Sc0.1Ce0.01O2-x layer, 40 wt %, 30 wt %, and 30 wt %), a layer of La0.6Sr0.4Ni0.3Mn0.7O3 and Zr0.89Sc0.1Ce0.01O2-x (La0.6Sr0.4Ni0.3Mn0.7O3—Zr0.89Sc0.1Ce0.01O2-x layer, 50 wt % ratio) and a layer of BaZr0.1Ce0.7Y0.2O3 and Zr0.89Sc0.1Ce0.01O2-x (BaZr0.1Ce0.7Y0.2O3—Zr0.89Sc0.1Ce0.01O2-x layer, 50 wt % ratio) were respectively deposited on the Zr0.89Sc0.1Ce0.01O2-x electrolyte films and sintered at around 900° C. to 1100° C. to obtain three reactors. The active area of each of the La0.6Sr0.4Ni0.3Mn0.7O3—BaZr0.1Ce0.7Y0.2O3 layer, the La0.6Sr0.4Ni0.3Mn0.7O3 layer and the BaZr0.1Ce0.7Y0.2O3 layer was about 10 cm2.
A layer of porous platinum paste was applied to each of the La0.6Sr0.4Ni0.3Mn0.7O3—BaZr0.1Ce0.7Y0.2O3—Zr0.89Sc0.1Ce0.01O2-x layer, the La0.6Sr0.4Ni0.3Mn0.7O3—Zr0.89Sc0.1Ce0.01O2-x layer and the BaZr0.1Ce0.7Y0.2O3—Zr0.89Sc0.1Ce0.01O2-x layer to form a porous metallic current collector of each reactor.
The reactors were each put inside an alumina tube. The inner diameter of the alumina tube was about 2 cm. A gas stream (20 ppm NO balanced with He, 200 ml/min; or 20 ppm NO and 2,000 ppm O2 balanced with He, 200 ml/min) was fed into the alumina tube passing through the outer surface of the reactor at a temperature of 600° C. Direct current (DC) was applied on each reactor for about 900 minutes and increased from 0 to 50 mA for the gas stream without oxygen or to 200 mA for the gas stream with oxygen.
The La0.6Sr0.4Ni0.3Mn0.7O3—BaZr0.1Ce0.7Y0.2O3—Zr0.89Sc0.1Ce0.01O2-x layer, the La0.6Sr0.4Ni0.3Mn0.7O3—Zr0.89Sc0.1Ce0.01O2-x layer and the BaZr0.1Ce0.7Y0.2O3—Zr0.89Sc0.1Ce0.01O2-x layer were assigned as cathodes, where the direct decomposition of NO and electrochemical NO reduction took place. The (La0.8Sr0.2)0.95MnO3 layer was the anode, where the oxidation of oxygen ions took place. The corresponding voltage between anode and cathode was in the range of from 1 V to 1.5 V. Gas chromatography equipped with a PQ column and a RAE7800 gas sensor were used to detect NO and NO2 in the exhaust stream from the reactors with an accuracy of 1 ppm and 0.1 ppm, respectively. NO2 was not detected. The NO removal rate (conversion percentage) was calculated using the following formula: (NO volume in the gas stream-NO volume in the exhaust stream)/NO volume in the gas stream×100%.
It can be seen from
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201410605175.5 | Oct 2014 | CN | national |
