Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B13/00—Diaphragms; Spacing elements
  • C25B13/04—Diaphragms; Spacing elements characterised by the material
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
  • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
  • C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
  • H01M8/124—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte
  • H01M8/1246—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B15/00—Operating or servicing cells
  • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
  • H01M2008/1293—Fuel cells with solid oxide electrolytes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/10—Process efficiency
  • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• a number of chemical reactions form water, oftentimes as a secondary product when producing a more highly valued material.
• the water formed during solution-phase and gas-phase chemical reactions sometimes may be contaminated with small amounts of various chemical byproducts, so it may not be suitable for direct use without additional purification. In addition, isolation of the water may be problematic in some instances.
• Electrochemical reactions may have the capability to form higher purity water that may be readily isolated.
• Fuel cells for example, form water as a byproduct of generating electricity via an electrochemical reaction between molecular oxygen and molecular hydrogen or other suitable fuel. Since the purpose of fuel cells is to produce electricity, not form water, the reaction efficiency for forming water is generally rather poor.
• Other electrochemical processes similarly are not presently optimized for producing and isolating clean water as a primary product.
• FIGS. 1A and IB show illustrative cross-sectional diagrams of traditional fuel cells and their manner of operation.
• FIGS. 2A and 2B show illustrative cross-sectional diagrams of electrochemical cells featuring a mixed ionically and electronically conductive membrane and their manner of operation.
• FIG. 3 shows a diagram of an illustrative electrochemical cell formed in a tubular configuration .
• FIG. 4 shows a diagram of an illustrative electrochemical water generation system configured to extract waste heat and to return at least a portion of the waste heat to the mixed ionically and electronically conductive membrane.
• the present disclosure generally describes systems for generating water and, more specifically, electrochemical systems and methods for generating water at high-energy efficiencies.
• FIGS. 1A and IB show illustrative cross-sectional diagrams of traditional fuel cells and their manner of operation.
• Each traditional fuel cell features an ion- conductive membrane separating a cathode and an anode.
• the ion-conductive membrane may be an oxygen ion-conductive membrane or a proton-conductive membrane.
• the ion-conductive membrane is held at an elevated temperature to maintain ionic mobility at or above a desired threshold value.
• the operational principles of the fuel cell change slightly, as explained further in reference to FIGS. 1A and IB.
• fuel cell 100 comprises cathode 102 and anode 104, which are separated by ionically conductive membrane 106 interposed in between.
• ionically conductive membrane 106 is an oxygen ion- conductive membrane.
• a molecular oxygen-containing gas or air is supplied to cathode 102, whereupon oxide ions are formed via reduction of molecular oxygen.
• the oxide ions migrate through ionically conductive membrane 106 (oxygen ion- conductive membrane) toward anode 104.
• the oxide ions react with molecular hydrogen or a hydrogen-containing gas to oxidize the molecular hydrogen or hydrogen-containing gas to form water and potentially other gaseous products.
• Water is the sole product formed when molecular hydrogen is supplied to anode 104. If a hydrocarbon is instead supplied to anode 104, carbon dioxide is produced concurrently with the water. Electrons released from the oxidation reaction travel through external circuit 108, which establishes electrical communication between cathode 102 and anode 104.
• Fuel cell 101 differs from fuel cell 100 in that ionically conductive membrane 106 is a proton-conductive membrane in fuel cell 101.
• molecular hydrogen or a hydrogen-containing gas is again supplied to anode 104.
• Oxidation of the molecular hydrogen or hydrogen- containing gas takes place in anode 104 to generate protons.
• carbon dioxide is also produced concurrently with the protons.
• the protons generated at anode 104 migrate through ionically conductive membrane 106 (proton-conductive membrane) toward cathode 102, whereupon they react with molecular oxygen to form water. Electrons released from the oxidation reaction in anode 104 again travel through external circuit 108.
• fuel cells 100 and 101 provide electrical power in the form of a current through external circuit 108.
• water may be formed as a byproduct in either fuel cell configuration, the primary purpose of fuel cells 100 and 101 is to generate electrical power, not form water.
• the system components, including ionically conductive membrane 106, are optimized for electricity production rather than water production. As a result, the water production may be rather inefficient with respect to the amounts of molecular oxygen and molecular hydrogen that are supplied.
• the present disclosure employs mixed ionically and electronically conductive membranes within an electrochemical cell architecture that may or may not employ an external circuit.
• the term "mixed ionically and electronically conductive membrane” refers to a membrane material capable of transferring both ions and free electrons (or electron holes). All of the free electrons produced in an electrochemical reaction need not necessarily flow across a mixed ionically and electronically conductive membrane in the presence of an external circuit. Instead, a first portion of the free electrons may travel between the anode and the cathode in the external electrical circuit, and a second portion of the free electrons may travel across the mixed ionically and electronically conductive membrane.
• Up to 100% of the free electrons may travel across the mixed ionically and electronically conductive membrane when an external circuit is present. In the absence of an external electrical circuit, all of the free electrons or electron holes may travel between the anode and the cathode across the mixed ionically and electronically conductive membrane.
• a mixed ionically and electronically conductive membrane may be fully dense (>95% of the theoretical density and/or ⁇ 5% porosity) and not allow gaseous materials, such as molecular oxygen, air, hydrogen gas (molecular hydrogen), or gaseous hydrocarbons to pass through in un-ionized form .
• gaseous materials such as molecular oxygen, air, hydrogen gas (molecular hydrogen), or gaseous hydrocarbons to pass through in un-ionized form .
• At least a majority of the pores that are present in the mixed ionically and electronically conductive membrane may be closed pores, so as to minimize the risk of gas mixing within the membrane.
• substantially all of the mass transport taking place through a mixed ionically and electronically conductive membrane occurs in the form of ionic transport.
• FIGS. 2A and 2B show illustrative cross-sectional diagrams of electrochemical cells 200 and 201, corresponding to fuel cells 100 and 101 shown in FIGS. 1A and IB, except for the substitution of mixed ionically and electronically conductive membrane therein 206.
• the structural details in FIGS. 2A and 2B are similar to those of FIGS. 1A and IB, and common reference characters are used to denote features having like functionality.
• the electrons (or electron holes) being conveyed across mixed ionically and electronically conductive membrane 206 are also shown in FIGS. 2A and 2B.
• the direction of electron flow through mixed ionically and electronically conductive membrane 206 is from anode 104 to cathode 102 in both cell configurations. Electron hole flow is in the opposite direction (not shown). Depending upon whether external circuit 108 is present, all or a portion of the electrons may flow through mixed ionically and electronically conductive membrane 206.
• the present disclosure appreciates that while mixed ionically and electronically conductive membranes may lower the electrical current attainable from an electrochemical cell, if an external circuit is even present, such membranes may provide significant advantages from a water generation standpoint. Namely, the electrons travelling across the mixed ionically and electronically conductive membrane may make water generation more efficient by promoting a catalytic reaction at the interface between the mixed ionically and electronically conductive membrane and at least one of the cathode or the anode. That is, the electrons passing through the mixed ionically and electronically conductive membrane may be positioned in a location where they may more effectively promote a catalytic chemical reaction to generate water within the cathode or the anode. As a further advantage, the materials of at least some mixed ionically and electronically conductive membranes may be incorporated within the cathode or the anode to promote better matching of thermal expansion coefficients, thereby disfavoring structural delamination under operational heating.
• the water produced from electrochemical cells featuring a mixed ionically and electronically conductive membrane may be produced in the form of steam. Condensation of the steam provides waste heat that must be addressed in some manner.
• at least a portion of the waste heat withdrawn from the steam may be recycled to the mixed ionically and electronically conductive membrane to improve the overall energy efficiency of the electrochemical reactions for forming water.
• waste heat from the steam may be supplied to other waste heat conversion processes and/or waste heat from other sources may be supplied to the mixed ionically and electronically conductive membrane.
• an electrical current may be produced and used to power a load connected thereto.
• the electrical power may be stored in a suitable energy storage device.
• electrochemical cells featuring a mixed ionically and electronically conductive membrane may provide a relatively simple system for generating water, particularly if the optional external circuit is not present.
• Moving parts of such water generation systems may be limited to auxiliary components, thereby providing long operational lifetimes.
• efficiencies may be realized in the water generation systems by recycling waste heat withdrawn from the steam generated during their operation. Alternately, the waste heat can be redirected to other applications in need of a source of thermal energy. Efficiencies that are much greater than conventional methods of water production, such as desalination, may be realized.
• the electrochemical water generation systems comprise at least one electrochemical cell, which comprises: a first electrode and a second electrode, optionally in electrical communication via an external circuit, a mixed ionically and electronically conductive membrane interposed between and in contact with the first electrode and the second electrode, a hydrogen-containing gas supply in fluid communication with one of the first electrode and the second electrode, a molecular oxygen-containing gas supply in fluid communication with the other of the first electrode and the second electrode, and a first gas outlet extending from the first electrode and a second gas outlet extending from the second electrode.
• the external electrical circuit may be omitted, in which case the flow of electrons or electron holes occurs exclusively through the mixed ionically and electronically conductive membrane. In other embodiments, the external electrical circuit may be present, in which case a portion of the electrons may or may not flow through the external electrical circuit.
• the molecular oxygen-containing gas supply may contain or be configured to supply substantially pure molecular oxygen (0 2 gas), in some embodiments.
• the molecular oxygen-containing gas supply may contain or be configured to supply air, which comprises approximately 21% molecular oxygen in combination with approximately 78% nitrogen, 1% argon, and less than 1% carbon dioxide and other gases.
• Other gaseous mixtures comprising molecular oxygen, including air mixtures with other gases, may also be suitably present within the molecular oxygen-containing gas supply in alternative embodiments of the present disclosure.
• the molecular oxygen-containing gas supply may contain or be configured to supply air or oxygen gas to the first electrode or the second electrode.
• the hydrogen-containing gas supply may contain or be configured to supply any gas or gas mixture comprising molecular hydrogen (hydrogen gas) and/or one or more compounds comprising chemically bonded hydrogen.
• the hydrogen- containing gas supply may contain or be configured to supply at least one of hydrogen gas, a hydrocarbon gas, or ammonia gas to the first electrode or the second electrode.
• hydrogen sulfide H 2 S
• Hydrocarbon gases for example, may be scrubbed to remove hydrogen sulfide and other sulfur-containing compounds before being introduced as a feed in the systems and methods of the present disclosure.
• hydrocarbon refers to any compound containing hydrogen bound to carbon, including both saturated and/or unsaturated hydrocarbons, as well as those containing heteroatom substitution.
• suitable hydrocarbon gases may include, for example, methane, ethane, propane, butane, ethylene, propylene, acetylene, or the like.
• natural gas may be supplied as an electrochemical cell for purposes of generating water.
• suitable mixed ionically and electronically conductive membranes may include materials such as, for example, defect AB0 3 - d perovskites (0 ⁇ d ⁇ l), doped ⁇ -bismuth oxide (5-Bi 2 0 3 ), and doped cerium oxide (Ce0 2 ), which may be in a mixed phase. Combinations of these materials may also be present in a mixed ionically and electronically conductive membrane. Dopants for 5-Bi 2 0 3 and Ce0 2 may be present in a non-zero amount up to about 35 atomic percent.
• the defect AB0 3 _ d perovskites may be either an oxygen ion conductor or a proton conductor. Doped ⁇ -bismuth oxide and doped cerium oxide are oxide ion conductors. Suitable defect AB0 3 _ d perovskites may include those in which A is selected from the group consisting of Ba, Fe, La, Ce and Sr, and B is selected from the group consisting of Zr, Cu, Fe and Co. Variables A and B need not necessarily represent a single atom, and mixtures of the choices of A and/or B may be selected that maintain charge neutrality and the desired type of ionic conduction.
• a barium cerate zironate perovskite-type species may be present in the mixed ionically and electronically conductive membrane.
• Additional materials or doped variants thereof that may suitably comprise a mixed ionically and electronically conductive membrane of the present disclosure include, for example, SrTi0 3 , Ti0 2 , (La,Ba,Sr)(Mn,Fe,Co)0 3 _ d (0 ⁇ d ⁇ l), La 2 Cu0 4+d (0 ⁇ d ⁇ 0.5), LiFeP0 4 and LiMnP0 4 .
• the above mixed ionically and electronically conductive membrane may comprise a single-phase material .
• the mixed ionically and electronically conductive membrane may comprise a mixed-phase and/or multiphase material comprising two or more distinct phases or materials.
• Ce0 2 or doped Ce0 2 for example, that has been exposed to high temperatures and a reducing atmosphere may form Ce0 2 _ x structures in a mixed phase that is a mixed ionic and electronic conductor.
• the mixed ionically and electronically conductive membrane may comprise a composite material having two or more distinct phases.
• such composite materials may comprise an ionically conducting phase and an electronically conducting phase.
• the electronically conducting phase may comprise a rare earth doped strontium titanate, other doped perovskite, or a metallic phase such as silver.
• the mixed ionically and electronically conductive membranes are believed to transport oxygen ions or protons from a location of high chemical potential to a location of lower chemical potential, which is proportional to the partial pressures upon each side of the mixed ionically and electronically conductive membrane.
• Oxygen ion transport is believed to take place by a vacancy mechanism .
• Proton transport is believed to take place by association with water to form hydroxide ions, which are transportable across the mixed ionically and electronically conductive membrane.
• the electromotive force (EMF) is therefore dependent upon the oxygen partial pressures at the anode and the cathode.
• the oxygen partial pressure at the anode is given by Formula 3
• K (0X) is the equilibrium constant for the oxidation reaction described above
• PH 2 is the hydrogen gas partial pressure
• PH 2 O is the water partial pressure
• multiple electrochemical cells may be connected in series and/or in parallel to form an electrochemical stack.
• Suitable electrochemical stack configurations are not considered to be particularly limited, either in the number of individual cells or in the specific stack design.
• the first electrode may be the cathode and the molecular oxygen-containing gas supply may be in fluid communication with the cathode
• the second electrode may be an anode and the hydrogen-containing gas supply may be in fluid communication with the anode
• the mixed ionically and electronically conductive membrane may comprise an oxygen ion-conductive membrane.
• the first electrode may be the cathode and the molecular oxygen- containing gas supply may be in fluid communication with the cathode
• the second electrode may be an anode and the hydrogen-containing gas supply may be in fluid communication with the anode
• the mixed ionically and electronically conductive membrane may comprise a proton-conductive membrane.
• FIG. 2B Such a cell configuration is shown in FIG. 2B.
• FIGS. 2A and 2B have shown cathode 102 and anode 104 disposed in a planar configuration, with mixed ionically and electronically conductive membrane 206 interposed in between, it is to be appreciated that other cell configurations also lie within the scope of the present disclosure.
• cathode 102, anode 104, and mixed ionically and electronically conductive membrane 206 may be disposed in a tubular configuration, in which these elements collectively comprise the wall of the tube.
• FIG. 3 shows a diagram of an illustrative electrochemical cell configuration in which cathode 102, anode 104 and mixed ionically and electronically conductive membrane 206 are arranged in a tubular configuration within electrochemical cell 300.
• Passage 302 extends within the interior of electrochemical cell 302.
• a hydrogen-containing gas ⁇ e.g., hydrogen gas or a hydrocarbon
• a molecular oxygen-containing gas may be located within exterior space 304 adjacent to cathode 102 and supply molecular oxygen thereto.
• the positions of cathode 102 and anode 104 may be reversed, in which case molecular oxygen-containing gas may instead circulate through passage 302 and hydrogen-containing gas may be located in exterior space 304.
• no external circuit is shown in FIG. 3.
• Tubular electrochemical cells such as that shown in FIG. 3, may be fabricated using extrusion and coating techniques.
• an anode slurry may be prepared comprising electrolyte powder and cellulose as the binder.
• the anode components may be mixed with water using an industrial mixer for 1-2 hours and left to age overnight.
• a vacuum may be placed over the anode slurry to allow for removal of excess air.
• Anode tubes may be extruded from the anode slurry using a ram extruder and a custom made die. The anode tubes may be allowed to dry, cut to a desired length, dip- coated in an electrolyte slurry and allowed to dry.
• the electrolyte slurry may be mixed with organic ingredients such as binder (polyvinyl butyral), dispersant (fish oil) and solvents (toluene and ethanol).
• binder polyvinyl butyral
• dispersant fish oil
• solvents toluene and ethanol
• the desired electrolyte thickness may be achieved through multiple electrolyte coatings.
• the tubes may be sintered at 1200-1450°C for 6-18 hours in air.
• the electrolyte-coated anode tubes may be dip-coated in a cathode slurry containing organic ingredients similar with those of the electrolyte slurry.
• the cathode dip-coated tubes may be dried in air and sintered at 800-1000°C for 1-6 hours in air to complete the tubular cell fabrication.
• Suitable materials for forming the cathode and/or the anode may be catalytically active toward promoting water formation (specifically toward generating oxygen ions or protons), according to some embodiments.
• the mixed ionically and electronically conductive membrane comprises an oxygen ion-conductive material
• the anode may comprise a catalytically active material to promote water formation therein.
• the cathode may comprise a catalytically active material to promote water formation.
• both the cathode and the anode may comprise suitable catalytically active materials to more effectively promote water formation in one of the electrodes, depending upon whether an oxygen ion-conductive membrane or a proton-conductive membrane is present.
• suitable materials that may be present, particularly in the electrode where water is being formed may include, for example, Ni, Ce, Co, Fe, Cu, Zn, Sc, Ti, V, Cr, Mn, or any oxide thereof.
• the anode may comprise one or more of these materials.
• the material(s) comprising the mixed ionically and electronically conductive membrane may also be present in at least a portion of the cathode and/or the anode.
• the electrochemical reaction to generate water releases electrons, a portion of which may flow as a current through the external circuit and a portion of which may travel through the mixed ionically and electronically conductive membrane.
• Application of additional electrical current may be advantageous, however, to promote more efficient formation of the ionic species in either electrode.
• the current generated from the electrochemical reaction to form water may be supplied to a load in electrical communication with the external circuit.
• the electrochemical water generation systems described herein may comprise a heat exchanger in thermal communication with at least one of the first gas outlet and the second gas outlet.
• the heat exchanger may be configured to withdraw waste heat from steam produced in the first electrode or the second electrode.
• the heat exchanger may be in thermal communication with the gas outlet extending from either the cathode or the anode.
• the heat exchanger may be in thermal communication with the second gas outlet, and the second gas outlet may be configured to withdraw steam from the second electrode (anode).
• the heat exchanger may be in thermal communication with the first gas outlet, and the first gas outlet may be configured to withdraw steam from the first electrode (cathode).
• Suitable heat exchangers for use in the present disclosure may be configured to withdraw excess heat from a fluid, particularly steam .
• the excess heat from the steam may be withdrawn by directly contacting the steam with a component of the heat exchanger, or the heat exchanger may be in thermal communication with a conduit through which the steam is travelling.
• the heat exchanger may be configured to supply waste heat extracted from at least one of the first gas outlet and the second gas outlet to the mixed ionically and electronically conductive membrane. Returning the waste heat from the steam to the mixed ionically and electronically conductive membrane may lead to more efficient operation of the electrochemical water generation systems.
• Direct conversion of the chemical energy to the products and electrical energy is not limited by the Carnot cycle efficiency. Hence, cell efficiencies are greater than those in desalination plants. Chemical efficiencies between 50-60% may be possible. If waste heat is returned to the mixed ionically and electronically conductive membrane, an overall system efficiency of up to 80- 90% or even greater may be realizable.
• Heat exchangers suitable for use in the embodiments herein are not considered to be particularly limited.
• Illustrative heat exchangers that may be suitable for use in the various embodiments of the present disclosure include, for example, shell and tube heat exchangers, plate heat exchangers, plate and shell heat exchangers, plate fin heat exchangers, microchannel heat exchangers, heat pipes, or direct contact heat exchangers.
• Choice of a suitable heat exchanger may be application-specific, particularly depending upon whether or not the waste heat is recycled to the mixed ionically and electronically conductive membrane. If the waste heat is not recycled to the mixed ionically and electronically conductive membrane, the waste heat may be utilized in other applications in need of excess thermal energy. In illustrative embodiments, the waste heat may be supplied to promote chemical reactions such as desalination, and heating or cooling applications.
• FIG. 4 shows a diagram of an illustrative electrochemical water generation system 400 configured to extract waste heat from a gas outlet and to return at least a portion of the waste heat to the mixed ionically and electronically conductive membrane.
• molecular oxygen or air
• hydrogen gas or a hydrocarbon
• conduit 404 adjacent to anode 104 such that the hydrogen gas (or hydrocarbon) can diffuse into porosity within anode 104.
• Water produced in anode 104 exits from conduit 404 in the form of steam through gas outlet 406. Upon exiting gas outlet 406, the steam may condense as liquid water and be collected (collection apparatus not shown).
• external circuit 108 is optional in electrochemical water generation system 400.
• Heat exchanger 408 is in thermal communication with gas outlet 406. Heat exchanger 408 may collect waste heat from the steam within gas outlet 406 to facilitate its condensation into liquid water. According to some embodiments, the waste heat accumulated in heat exchanger 408 may then be returned to mixed ionically and electronically conductive membrane 206 via thermal conduit 410 to facilitate ionic conductivity therein. It is to be appreciated that other heat sources, including other sources of waste heat, may be in thermal communication with mixed ionically and electronically conductive membrane 206 in addition to or as an alternative to that provided from heat exchanger 408. For example, in alternative embodiments, the waste heat output of a power plant, gas turbine or other heat source may be in thermal communication with mixed ionically and electronically conductive membrane 206 to improve the overall energy efficiency.
• FIG. 4 has shown an electrochemical water generation system 400 utilizing an oxygen ion-conductive membrane, it is to be appreciated that a proton-conductive membrane may be utilized in alternative embodiments.
• heat exchanger 408 may be in thermal communication with gas outlet 412 of conduit 402 in order to withdraw waste heat produced in cathode 102 in this cell configuration.
• this alternative cell configuration is not shown in further detail in the drawings.
• electrochemical water generation systems disclosed herein may comprise at least one electrochemical cell comprising : a cathode and an anode, optionally in electrical communication via an external circuit; a mixed ionically and electronically conductive membrane interposed between and in contact with the cathode and the anode, the mixed ionically and electronically conductive membrane comprising an oxygen ion- conductive material; a hydrogen-containing gas supply in fluid communication with the anode; a molecular oxygen-containing gas supply in fluid communication with the cathode; a gas outlet extending from the anode; and a heat exchanger in thermal communication with the gas outlet.
• the heat exchanger may be configured to supply waste heat extracted from the gas outlet to the mixed ionically and electronically conductive membrane.
• electrochemical water generation systems disclosed herein may comprise at least one electrochemical cell comprising : a cathode and an anode, optionally in electrical communication via an external circuit; a mixed ionically and electronically conductive membrane interposed between and in contact with the cathode and the anode, the mixed ionically and electronically conductive membrane comprising a proton-conductive material; a hydrogen-containing gas supply in fluid communication with the anode; a molecular oxygen-containing gas supply in fluid communication with the cathode; a gas outlet extending from the cathode; and a heat exchanger in thermal communication with the gas outlet.
• the heat exchanger may be configured to supply waste heat extracted from the gas outlet to the mixed ionically and electronically conductive membrane.
• the present disclosure provides methods for electrochemically forming water.
• the methods may comprise : supplying a molecular oxygen- containing gas to a first electrode of an electrochemical cell and a hydrogen- containing gas to a second electrode of an electrochemical cell having a mixed ionically and electronically conductive membrane interposed between and in contact with the first electrode and the second electrode, the first electrode and the second electrode optionally being in electrical communication via an external circuit; heating the mixed ionically and electronically conductive membrane to a temperature at or above that needed to maintain ionic mobility in the mixed ionically and electronically conductive membrane at or above a predetermined level; generating an ionic species from the molecular oxygen-containing gas or the hydrogen-containing gas in one of the first electrode or the second electrode; migrating the ionic species across the mixed ionically and electronically conductive membrane to the other of the first electrode or the second electrode; after migrating across the mixed ionically and electronically conductive membrane
• the mixed ionically and electronically conductive membrane may comprise an oxygen ion-conductive membrane or a proton- conductive membrane, and the steam may be withdrawn from either the first electrode or the second electrode depending upon which type of ionically and electronically conductive membrane is present, as discussed in further detail herein.
• the methods of the present disclosure may comprise interacting the steam with a heat exchanger in thermal communication with a gas outlet containing the steam to withdraw waste heat, and supplying the waste heat to the mixed ionically and electronically conductive membrane. Withdrawal of waste heat from the steam may affect condensation of the steam into liquid water, according to some embodiments.
• the methods of the present disclosure may still further comprise collecting the liquid water, such as in a suitable container. The collected water may be potable and used for drinking purposes, or it may be used for conducting one or more secondary reactions, according to some embodiments.
• the temperature needed to maintain ionic mobility at a predetermined level in the mixed ionically and electronically conductive membrane may vary depending upon the chosen membrane material. Moreover, the chosen degree of ionic mobility may vary depending upon the desired rate of water generation. In more specific embodiments, the temperature needed to maintain ionic mobility may range between about 300°C and about 1000°C, or between about 300°C and about 800°C, or between about 300°C and about 700°C, or between about 300°C and about 400°C, or between about 400°C and about 500°C, or between about 500°C and about 500°C, or between about 600°C and about 700°C Temperatures within a suitable range to maintain ionic mobility at a desired level may also promote correspondingly high current density values within the electrochemical cell.
• Temperatures for proton-conductive membranes may, in some embodiments, be kept below about 700°C to maintain a partial pressure of water to promote proton transport, whereas oxygen ion-conductive membranes may be suitably operated at temperatures up to about 1000°C, according to other embodiments. Electrochemical reaction kinetics may also affect the observed current density values.
• Embodiments disclosed herein include:
• A. Electrochemical water generation systems comprising : at least one electrochemical cell comprising : a first electrode and a second electrode, optionally in electrical communication via an external circuit; a mixed ionically and electronically conductive membrane interposed between and in contact with the first electrode and the second electrode; a hydrogen-containing gas supply in fluid communication with one of the first electrode and the second electrode; a molecular oxygen-containing gas supply in fluid communication with the other of the first electrode and the second electrode; and a first gas outlet extending from the first electrode and a second gas outlet extending from the second electrode.
• the systems comprise: at least one electrochemical cell comprising : a cathode and an anode, optionally in electrical communication via an external circuit; a mixed ionically and electronically conductive membrane interposed between and in contact with the cathode and the anode, the mixed ionically and electronically conductive membrane comprising an oxygen ion-conductive material; a hydrogen-containing gas supply in fluid communication with the anode; a molecular oxygen-containing gas supply in fluid communication with the cathode; a gas outlet extending from the anode; and a heat exchanger in thermal communication with the gas outlet.
• Methods for producing water using a mixed ionically and electronically conductive membrane comprise: supplying a molecular oxygen-containing gas to a first electrode of an electrochemical cell and a hydrogen-containing gas to a second electrode of an electrochemical cell; wherein a mixed ionically and electronically conductive membrane is interposed between and in contact with the first electrode and the second electrode; and wherein the first electrode and the second electrode are optionally in electrical communication via an external circuit; heating the mixed ionically and electronically conductive membrane to a temperature at or above that needed to maintain ionic mobility in the mixed ionically and electronically conductive membrane at or above a predetermined level; generating an ionic species from the molecular oxygen-containing gas or the hydrogen-containing gas in one of the first electrode or the second electrode; migrating the ionic species across the mixed ionically and electronically conductive membrane to the other of the first electrode or the second electrode; after migrating across the mixed ionically and electronically conductive membrane, reacting the ionic
• Element 1 wherein the system further comprises: a heat exchanger in thermal communication with at least one of the first gas outlet and the second gas outlet.
• Element 2 wherein the heat exchanger is configured to supply waste heat extracted from at least one of the first gas outlet and the second gas outlet to the mixed ionically and electronically conductive membrane.
• Element 3 wherein the first electrode is a cathode and the molecular oxygen-containing gas supply is in fluid communication with the cathode, the second electrode is an anode and the hydrogen-containing gas supply is in fluid communication with the anode, and the mixed ionically and electronically conductive membrane comprises an oxygen ion-conductive membrane.
• Element 4 wherein the oxygen ion-conductive membrane comprises at least one material selected from the group consisting of a defect AB0 3 _ d perovskite (0,d ⁇ . l), doped 5-Bi 2 0 3 , and doped, mixed-phase cerium oxide; wherein A is selected from the group consisting of Ba, Fe, La, Ce, and Sr, and B is selected from the group consisting of Zr, Cu, Fe and Co.
• Element 5 wherein the heat exchanger is in thermal communication with the second gas outlet, and the second gas outlet is configured to withdraw steam from the second electrode.
• Element 6 wherein the first electrode is a cathode and the molecular oxygen-containing gas supply is in fluid communication with the cathode, the second electrode is an anode and the hydrogen-containing gas supply is in fluid communication with the anode, and the mixed ionically and electronically conductive membrane comprises a proton-conductive membrane.
• Element 7 wherein the heat exchanger is in thermal communication with the first gas outlet, and the first gas outlet is configured to withdraw steam from the first electrode.
• Element 8 wherein the molecular oxygen-containing gas supply is configured to supply air or oxygen gas to the first electrode or the second electrode.
• Element 9 wherein the hydrogen-containing gas supply is configured to supply at least one of hydrogen gas, a hydrocarbon gas, or ammonia gas to the first electrode or the second electrode.
• Element 10 wherein the mixed ionically and electronically conductive membrane comprises a single-phase material.
• Element 11 wherein the heat exchanger is configured to supply waste heat extracted from the gas outlet to the mixed ionically and electronically conductive membrane.
• Element 12 wherein the method further comprises: interacting the steam with a heat exchanger in thermal communication with a gas outlet containing the steam to withdraw waste heat; and supplying the waste heat to the mixed ionically and electronically conductive membrane.
• Element 13 wherein the temperature needed to maintain ionic mobility at or above a predetermined level ranges between about 300°C and about 1000°C.
• Element 14 wherein at least one of the first electrode or the second electrode comprises a material that is catalytically active toward reacting the ionic species to form water.
• exemplary combinations applicable to A, B, and C include : The system of A in combination with elements 1 and 2; 1- 3; 1 and 3; 1, 3 and 4; 1-4; 1 and 5; 1 and 6; 1, 2 and 5; 1, 2 and 6; 1, 6 and 7; 1, 2, 6 and 7; 1 and 8; 1 and 9; 3 and 4; 3 and 5; 3-5; 3, 4, and 8; 3 and 8; 3 and 9; 3, 4 and 9; 6 and 7; 6 and 8; 6-8; 6, 7 and 9; 6 and 9; 8 and 9; 1 and 14; 1, 2 and 14; 1, 3 and 14; 1, 5 and 14; 3 and 14; 3, 4 and 14; 3, 5 and 14; 3, 8 and 14; 3, 9 and 14; 6 and 14; 6, 7 and 14; 6, 8 and 14; 8 and 14; and 9 and 14.
• the system of B in combination with elements 4 and 8; 4 and 11; 4, 8 and 9; 4 and 9; 8 and 11; 9 and 11; 4 and 14; 4, 8 and 14; 4, 11 and 14; 4, 8, 9 and 14; 4, 9 and 14; 8 and 14; 9 and 14; 8, 11 and 14; 9, 11 and 14; and 11 and 14.
• the method of C in combination with elements 3 and 12; 3, 4 and 12; 6 and 12; 6 and 13; 6 and 14; 3, 4 and 14; 3 and 14; 8 and 14; 9 and 14; 8, 9 and 14; 8 and 13; and 9 and 13.
• the phrase "at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (i.e., each item).
• the phrase "at least one of” allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items.
• the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C.

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• 2018
  • 2018-06-20 US US16/013,462 patent/US20180363150A1/en not_active Abandoned
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