Patent Grant
12146233
The disclosure relates generally to methods and systems of carbonaceous material production. More specifically, the disclosure relates to electrochemical cells including tunable catalysts, carbon dioxide hydrogenation systems including the tunable catalysts, and methods of utilizing the tunable catalysts for selective carbon dioxide hydrogenation.
As the global energy demand has increased, the combustion of fossil fuels has, as well. As a result, unprecedented amounts of carbon dioxide (CO2) emissions have been released into the atmosphere, and the emissions rate continues to escalate. Concern regarding the potential negative consequences of these increasing emissions (e.g., climate change effects) has driven efforts to reduce atmospheric CO2 levels through CO2 capture, sequestration, and/or utilization.
In the utilization category, a promising approach for reducing CO2 emissions involves chemical synthesis. Through chemical synthesis, CO2 emissions may be converted into many desirable products, such as valuable carbonaceous materials and hydrocarbons (e.g., carbon monoxide and methane). However, unless these commodity chemicals are efficiently produced, CO2 conversion is not profitable and, thus, not commercially feasible.
Some processes have focused on electrochemical CO2 conversion because it is one of the more efficient pathways to produce multiple commodity chemicals from CO2 emissions. One of these electrochemical conversion techniques is called hydrogenation (e.g., electrohydrogenation). By reacting CO2 with hydrogen gas (H2) in the presence of at least one catalyst, the CO2 is hydrogenated, and chemicals such as carbon monoxide and methane may be produced. The carbon monoxide and methane may then be converted into additional commodity chemicals (e.g., formic acid, formaldehyde, methanol, other alcohols, formates, carboxylic acids, esters, methylated amines, formamides, aldehydes, etc.) through conventional reaction mechanisms.
However, such conventional electrochemical methods have not sufficiently addressed the needs of the industry because they are energy intensive (e.g., generating more CO2 than is consumed to produce the desirable product) and/or prohibitively expensive (e.g., employing costly catalytic materials to effectuate desirable reaction kinetics). Furthermore, the conventional electrochemical methods have not met the industry need of producing specific commodity chemicals and specific concentrations of commodity chemicals while reducing the amount of unwanted byproducts. For example, an industry may desire a single chemical from the conversion process or a mixture of chemicals with a specific ratio. To achieve this, the development of several compositions of catalysts and a complete redesign of electrolytic systems have been needed. However, this dramatically increases the cost of the electrolytic systems and decreases its efficiency.
A method of hydrogenating carbon dioxide is disclosed and comprises forming a tunable catalyst comprising at least one metal comprising a size within a range of from a single atom to about 999 nanometers and formulated to produce one or more carbon-containing compound. An electrochemical cell comprising a positive electrode, a negative electrode comprising the tunable catalyst, and an electrolyte between the positive electrode and the negative electrode is formed. Carbon dioxide is introduced to the negative electrode of the electrochemical cell and a potential difference is applied between the positive electrode and the negative electrode of the electrochemical cell to selectively hydrogenate the carbon dioxide. The hydrogen ions are diffused through the electrochemical cell. The carbon dioxide at the negative electrode is hydrogenated to selectively form carbon monoxide, methane, or a desired ratio of carbon monoxide and methane.
An electrochemical cell is also disclosed and comprises a positive electrode, a negative electrode, and an electrolyte between the positive electrode and the negative electrode. The negative electrode comprises a tunable catalyst formulated to selectively hydrogenate carbon dioxide. The tunable catalyst comprises at least one metal comprising a size within a range of from a single atom to about 999 nanometers and formulated to produce one or more specific carbonaceous product.
A carbon dioxide hydrogenation system is also disclosed and comprises a hydrogen source, a carbon dioxide source, and one or more electrochemical apparatus in fluid communication with the hydrogen source and the carbon dioxide source. The electrochemical apparatus comprises a housing structure configured and positioned to receive a hydrogen stream from the hydrogen source and a carbon dioxide stream from the carbon dioxide source. One or more electrochemical cells are within the housing structure. The electrochemical cell comprises a positive electrode and a negative electrode within the housing structure, and an electrolyte between the positive electrode and the negative electrode. The negative electrode comprises a tunable catalyst comprising a size within a range of from a single atom to about 999 nanometers. The tunable catalyst is formulated to selectively produce one or more carbon-containing compound.
While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the disclosure, various features and advantages of this disclosure may be more readily ascertained from the following description of example embodiments provided with reference to the accompanying drawings, in which:
Carbon dioxide hydrogenation systems and electrochemical cells including tunable catalysts are disclosed, as are methods of using the tunable catalysts in the carbon dioxide hydrogenation systems and the electrochemical cells. The carbon dioxide hydrogenation system according to embodiments of the disclosure is used to selectively form one or more carbonaceous product from carbon dioxide by appropriate selection of the tunable catalyst. The carbonaceous product is selectively formed by tailoring electrocatalytic properties of the tunable catalyst. The tunable catalyst is a supported metal catalyst, such as a metal-metal oxide catalyst. By controlling bonding features between metal components and oxygen components of the tunable catalyst, the tunable catalyst is formulated and configured to selectively form a desired product or a combination of products at a desired ratio from the carbon dioxide. The bonding status between the metal components and the oxygen components may be altered to tailor the electrochemical behavior of the tunable catalyst. Electrocatalytic activity of the tunable catalyst is tailored to selectively produce one or more desired carbonaceous products from the carbon dioxide in the carbon dioxide hydrogenation system. The carbonaceous product or carbonaceous products may be used as a source to produce a commodity chemical. The carbon dioxide hydrogenation system according to embodiments of the disclosure is configured to electrohydrogenate the carbon dioxide at an intermediate temperature, such as at a temperature of from about 300° C. to about 500° C.
The tunable catalyst may include the metal-metal oxide catalyst that includes a metal support component and a metal oxide component. Hybridization between oxygen orbitals and metal orbitals of the tunable catalyst is controlled to produce a desired bonding status, which corresponds to the extent of bonding between metal-metal or metal-oxygen components of the tunable catalyst. The metal-oxygen hybridization within the tunable catalyst may be controlled to alter the tunable catalyst's surface chemical environment, enabling stabilization of specific transition states and control of species' movements to and from active sites during electrocatalysis. The interactions (e.g., bonding) between the metal and the oxygen components may be controlled to determine the metal-oxygen hybridization. As hybridization between the oxygen orbitals and the metal orbitals increases, one of the desired products may be selectively formed by the carbon dioxide hydrogenation process. Conversely, as hybridization between the oxygen orbitals and the metal orbitals decreases, a different desired product may be selectively formed by the carbon dioxide hydrogenation process. Alternatively, a combination of desired products may be formed by further adjusting the hybridization between the oxygen orbitals and metal orbitals. The combination of desired products may be formed at a desired ratio depending on an intended application (e.g., intended use) of the desired products, such as a source (e.g., feedstream) to produce a commodity chemical. A process window for selectively forming the desired product(s) may, therefore, be widened by altering the hybridization between the oxygen orbitals and the metal orbitals. Size (e.g., particle size) of the metal component also affects the hybridization between the oxygen orbitals and metal orbitals and may be controlled to tailor the electrocatalytic activity and selective formation of the carbonaceous product. The size of the metal may be controlled to tailor the selectivity of the carbon dioxide hydrogenation process.
Since the selectivity of the tunable catalyst is controllable by metal-oxygen hybridization or size of the metal, a single composition (e.g., a single chemical composition) of the tunable catalyst may be used in the carbon dioxide hydrogenation system and carbon dioxide hydrogenation process to achieve the desired selectivity of the carbonaceous product. Since a single carbonaceous product or a combination of carbonaceous products at a desired ratio may be formed using the carbon dioxide hydrogenation system according to embodiments of the disclosure, no separation acts are utilized to produce the desired product(s). The electrocatalytic activity of the tunable catalyst may be tailored to selectively produce, for example, carbon monoxide, methane, or a combination thereof from carbon dioxide in the carbon dioxide hydrogenation system. In contrast, conventional carbon dioxide hydrogenation systems and processes use multiple, different catalysts (catalysts of multiple chemical compositions) to produce different carbonaceous products and require separation processes to be conducted to produce the desired product. Alternatively, the conventional carbon dioxide hydrogenation systems must be redesigned to produce the desired carbonaceous products.
The following description provides specific details, such as material compositions and processing conditions (e.g., temperatures, pressures, flow rates, etc.) in order to provide a thorough description of embodiments of the disclosure. However, a person of ordinary skill in the art will understand that the embodiments of the disclosure may be practiced without necessarily employing these specific details. Indeed, the embodiments of the disclosure may be practiced in conjunction with conventional systems and methods employed in the industry. In addition, only those process components and acts necessary to understand the embodiments of the disclosure are described in detail below. A person of ordinary skill in the art will understand that some process components (e.g., pipelines, line filters, valves, temperature detectors, flow detectors, pressure detectors, and the like) are inherently disclosed herein and that adding various conventional process components and acts would be in accord with the disclosure. In addition, the drawings accompanying the disclosure are for illustrative purposes only, and are not meant to be actual views of any particular material, device, or system.
As used herein, spatially relative terms, such as “beneath,” “below,” “lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,” “left,” “right,” and the like, may be used for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the figure. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation depicted in the figure. For example, if materials in the figure are inverted, elements described as “below” or “beneath” or “under” or “on bottom of” other elements or features would then be oriented “above” or “on top of” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below, depending on the context in which the term is used, which will be evident to one of ordinary skill in the art. The materials may be otherwise oriented (e.g., rotated 90 degrees, inverted, flipped) and the spatially relative descriptors used herein interpreted accordingly.
As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
As used herein, “and/or” includes any and all combinations of one or more of the associated listed items.
As used herein, the term “carbonaceous product” means and includes a carbon-containing compound that includes one carbon (C1) atom.
As used herein, the term “configured” refers to a size, shape, material composition, material distribution, and arrangement of one or more of at least one apparatus facilitating operation of one or more of the structure and the apparatus in a pre-determined way.
As used herein, the terms “selectively form” or “selectively produce,” or grammatical equivalents thereof, refer to forming one carbonaceous product preferentially to another carbonaceous product. The selectively formed carbonaceous product may be formed at greater than or equal to about 51%, while the other carbonaceous product is formed at less than or equal to about 49%. The selectively formed carbonaceous product may, for example, be formed at greater than or equal to about 60%, greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, or greater than or equal to about 95%.
As used herein, the term “substantially” in reference to a given parameter, property, or condition means and includes to a degree that one skilled in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances. For example, a parameter that is substantially met may be at least about 90% met, at least about 95% met, or even at least about 99% met.
As used herein, the term “substantially all” means and includes greater than about 95%, such as greater than about 99%.
As used herein, the terms “about” and “approximately” in reference to a numerical value for a particular parameter are inclusive of the numerical value and a degree of variance from the numerical value that one of ordinary skill in the art would understand is within acceptable tolerances for the particular parameter. For example, “about” in reference to a numerical value may include additional numerical values within a range of from 90.0 percent to 110.0 percent of the numerical value, such as within a range of from 95.0 percent to 105.0 percent of the numerical value, within a range of from 97.5 percent to 102.5 percent of the numerical value, within a range of from 99.0 percent to 101.0 percent of the numerical value, within a range of from 99.5 percent to 100.5 percent of the numerical value, or within a range of from 99.9 percent to 100.1 percent of the numerical value.
As used herein, the terms “comprising,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method acts, but also include the more restrictive terms “consisting of” and “consisting essentially of” and grammatical equivalents thereof.
As used herein, the term “may” with respect to a material, structure, feature or method act indicates that such is contemplated for use in implementation of embodiments of the disclosure and such term is used in preference to the more restrictive term “is” so as to avoid any implication that other, compatible materials, structures, features and methods usable in combination therewith should or must be excluded.
As used herein, the terms “catalyst material” and “catalyst” and their grammatical equivalents each mean and include a material formulated to promote one or more reactions, resulting in the formation of a product.
As used herein, the term “negative electrode” and grammatical equivalents means and includes an electrode having a relatively lower electrode potential in an electrochemical cell (e.g., lower than the electrode potential in a positive electrode therein).
Conversely, as used herein, the term “positive electrode” and grammatical equivalents means and includes an electrode having a relatively higher electrode potential in an electrochemical cell (e.g., higher than the electrode potential in a negative electrode therein).
As used herein, the term “electrolyte” and grammatical equivalents means and includes an ionic conductor, which can be in a solid state, a liquid state, or a gaseous state (e.g., plasma).
As used herein, the term “tunable catalyst” and grammatical equivalents means and includes catalysts that may be tailored by adjusting (e.g., increasing, decreasing) the extent of metal and oxygen hybridization and/or size of at least one of the catalyst materials to selectively produce a desired carbonaceous product(s).
The tunable catalyst may be a supported metal catalyst, such as the metal-metal oxide catalyst. The metal (e.g., the metal support) of the metal-metal oxide catalyst may be a transition metal, such as iron, cobalt, nickel, copper, ruthenium, rhodium, palladium, silver, iridium, platinum, or gold. The size (e.g., the particle size) of the metal may range from an atomic size to a nanoparticle size, such as from about 1 angstrom (Å) to about 999 nanometers (nm). The particle size distribution may include a mean particle size within a range of from about 1 Å to about 999 nm. By way of example only, the size of the metal may include a single atom (SA), nanoclusters (NC), or nanoparticles (NP). The nanoclusters include from 2 metal atoms to 100 metal atoms, such as from 5 metal atoms to 20 metal atoms, from 10 metal atoms to 40 metal atoms, from 20 metal atoms to 50 metal atoms, from 30 metal atoms to 60 metal atoms, from 40 metal atoms to 70 metal atoms, from 50 metal atoms to 80 metal atoms, from 60 metal atoms to 90 metal atoms, or from 70 metal atoms to 100 metal atoms, with a particle size range from about 0.1 nm to about 1 nm. The nanoparticles may exhibit a particle size from about 1 nm to about 999 nm, such as from about 1 nm to about 500 nm, from about 1 nm to about 100 nm, from about 1 nm to about 20 nm, from about 1 nm to about 10 nm, from about 1 nm to about 5 nm, from about 1 nm to about 4 nm, or from about 2 nm to about 5 nm. In some embodiments, the metal of the metal-metal oxide catalyst is iridium. While examples herein may describe using iridium as the metal of the tunable catalyst, other transition metals may be used.
The metal oxide of the metal-metal oxide catalyst may be an oxide of a lanthanide element, such as a doped oxide of the lanthanide element where a dopant of the doped metal may include a different lanthanide element. The metal oxide of the tunable catalyst may include, but is not limited to, a supported metal ceria based catalyst, such as a supported metal samarium doped ceria (SDC) catalyst. While examples herein may describe using SDC as the metal oxide of the tunable catalyst, other catalysts (e.g., other metal oxide catalysts) formulated to convert carbon dioxide to carbonaceous products, such as to carbon monoxide or to methane, may be used. The tunable catalyst may comprise a ceria- and iridium-based (e.g., SDC/Ir) catalyst.
The tunable catalyst may be formed with the metal oxide component as single atoms, as nanoclusters, or as nanoparticles. Particles of the metal oxide may be variable in size. In other words, the metal oxide may be formed at a variety of sizes. The tunable catalyst may be formed by conventional techniques or by a complexing agent tailoring method described in application Ser. No. 17/445,687 entitled “METHODS OF FORMING METAL NANOMATERIALS,” the disclosure of which application is incorporated by reference herein in its entirety.
If, for example, the tunable catalyst includes increased hybridization between the oxygen orbitals and the metal orbitals, the tunable catalyst may function as a so-called “ionic metal” that exhibits favorable kinetics for the formation of CO in the carbon dioxide hydrogenation system. If, however, the tunable catalyst includes decreased hybridization between the oxygen orbitals and the metal orbitals, the tunable catalyst may function as a so-called “metallic metal” that exhibits favorable kinetics for the formation of CH4 in the carbon dioxide hydrogenation system. Additionally, if, for example, the metal is dispersed in the tunable catalyst as nanoparticles, the metal may maintain metallic properties and selectively form CH4. If, however, the metal is dispersed as single atoms, the metal may exhibit ionic properties and selectively form CO. The size of the metal (e.g., the particle size) may range from angstroms to microns, and more specifically, from single atoms to nanoparticle sizes.
The one or more product to be produced by the tunable catalyst may be a one carbon (C1) product, such as carbon monoxide (CO), methane (CH4), methanol (CH3OH), methylene (CH2) or a combination thereof. In some embodiments, carbon monoxide is selectively formed using the tunable catalyst in the carbon dioxide hydrogenation system. In other embodiments, methane is selectively formed using the tunable catalyst in the carbon dioxide hydrogenation system. In yet other embodiments, a combination of carbon monoxide and methane at a desired ratio is formed using the tunable catalyst in the carbon dioxide hydrogenation system.
The tunable catalyst may, for example, be a Sm2O3-doped CeO2 (SDC) supported Ir (SDC/Ir) catalyst that exhibits different iridium particle sizes. By way of example only, the iridium in the SDC/Ir catalyst may be a single atom, nanoclusters, or nanoparticles. Iridium-oxygen hybridization within the SDC/Ir catalyst is tailored by adjusting (e.g., increasing, decreasing) the particle size of the iridium of the SDC/Ir catalyst. The particle size (e.g., the Ir particle size) may range from angstroms to microns, and more specifically, from a single-atom (SA) size to a nanoparticle size. In accordance with embodiments of the disclosure, the Ir particles are of a particle size distribution in the range of from about 1 Å to about 1 μm. More specifically, the particle size distribution includes a mean particle size within a range of from about 1 Å to about 999 nm. The SDC/Ir catalyst may be used to selectively produce carbon-containing compounds, such as carbon monoxide (CO) or a hydrocarbon material (e.g., methane (CH4)). The SDC/Ir catalyst may be formed by conventional techniques or by methods described in application Ser. No. 17/445,687 entitled “METHODS OF FORMING METAL NANOMATERIALS.”
The iridium-oxygen hybridization within the tunable catalyst may be tuned to alter the catalyst's surface chemical environment, enabling the stabilization of specific transition states (*+CO, *COH, *HCO, where “*” represent an active site) and control of species' movements to and from active sites during electrocatalysis. As a result, the catalyst may be used in an electrochemical cell (e.g., a protonic ceramic CO2 electrolyzer) that operates with a high selectivity, such as a selectivity of greater than about 90% (e.g., greater than about 95%) towards the desired product at an intermediate temperature (e.g., from about 300° C. to about 500° C.), at a low overpotential, and at ambient pressure. The tunable catalyst may also be used in systems performing CO2 electrohydrogenation in tandem with light-alkane electrodehydrogenation and, consequently, the system may upgrade different carbon-containing compounds in a single act, significantly enhancing the efficiency, profitability, and commercial feasibility of CO2 conversion systems. For example, CO2 electrohydrogenation may be coupled with light-alkane electrodehydrogenation, such as ethane electrodehydrogenation.
The tunable catalysts, systems, and methods according to embodiments of the disclosure may reduce one or more of the time (e.g., processing acts), costs (e.g., material costs), and energy (e.g., thermal energy, electrical energy, etc.) used to produce the one or more carbonaceous products from CO2 (e.g., carbon monoxide and/or methane) relative to conventional methods, catalysts, systems, and apparatuses of producing the carbonaceous products. Accordingly, the tunable catalysts, systems, and methods according to embodiments of the disclosure may be more efficient, durable, and reliable than conventional methods, conventional systems, and conventional apparatuses.
The tunable catalyst according to embodiments of the disclosure is advantageous over conventional catalysts because the tunable catalyst may greatly improve the production rate and energy efficiency of the electrochemical cell containing the tunable catalyst and/or the carbon dioxide hydrogenation system containing the tunable catalyst without sacrificing the carbon dioxide conversion rate. For example, the tunable catalyst of the disclosure may selectively produce the desired carbonaceous product or desired carbonaceous products at the desired ratio while reducing the amount of unwanted byproducts. The tunable catalyst according to embodiments of the disclosure may also be advantageous over conventional catalysts because the tunable catalyst may be operated at intermediate temperatures, such as from about 300° C. to about 500° C., and at ambient pressures. Therefore, the tunable catalyst may be utilized in on-site CO2 conversion. Further, the tunable catalyst according to embodiments of the disclosure is cost-effective because the tunable catalyst may be tailored to selectively produce specific concentrations of the carbonaceous product(s) without redesigning the carbon dioxide hydrogenation system to produce these different concentrations. Additionally, the tunable catalyst according to embodiments of the disclosure is easily implemented and operated, since a single composition of the tunable catalyst may be tailored to selectively produce the desired carbonaceous product by altering the size of the metal within the tunable catalyst. As a result, no further separation process is utilized to produce the desired carbonaceous product. Since the electrocatalytic behavior of the tunable catalyst according to embodiments of the disclosure is tunable, the tunable catalyst may be used in various industries that utilize different carbonaceous products. The resulting carbonaceous product, such as CO, CH4, or a combination thereof, may be used as a source to produce a commodity chemical. The commodity chemical may include, but is not limited to, formic acid, formaldehyde, methanol, a formate, a methylated amine, an alcohol other than methanol, a carboxylic acid, a formamide, an aldehyde, or other commercially valuable commodity chemical.
Embodiments of the disclosure will now be described with reference to
Referring now to
To further understand the electronic properties at the SDC/IrN interface, the plane-averaged charge density difference along the z-direction was analyzed.
To gain a better understanding of this effect, projected density of states (PDOS) calculations 136, 138 were performed to detail the evolution of electronic orbitals. The PDOS calculations 136, 138 revealed that the p-d interaction between O 2p and Ir 5d orbitals pushes the band center of O 2p to lower energies as the number N increases, as shown in 136. This may lead to a significant impact on the charge transfer steps during catalysis, as the highest occupied molecular orbitals are usually dominated by the O 2p orbitals. In many cases, the catalytic activity may be dictated by the position of the O 2p band center relative to the Fermi level (EF). A proportional relationship between the value of EO2p-EF and the catalytic activity towards oxygen-containing species has been found, indicating that a low value of EO2p-EF is beneficial for CO generation. As for Ir 5d orbitals, the PDOS of Ir atoms on Ir (111) and IrO2 (100) surfaces were calculated for reference, as shown in 138. The band center energy of a single Ir atom on an SDC surface is quite close to that in an IrO2 lattice, indicating ionic features in single-atom (SA) Ir. On the other hand, the band center of Ir15 increases and gets closer to that of metal Ir, indicating metallic features in larger Ir clusters. The PDOS calculations 136, 138 reveal that the electronic properties of Ir clusters evolve from ionic to metallic character with increasing atomic numbers, which may be exploited to tune the catalytic behavior of the materials.
Referring now to
In light of these findings, large cluster nanoparticulate Ir (NP Ir) and small cluster Ir (atomic Ir, which is a mixture of single-atom Ir and nanoclustered Ir) were introduced onto SDC surfaces to modulate the local configurations of Ir—Ir and Ir—O bonding features, respectively. Referring now to
Followed by calcination in air, Ir atoms may be incorporated into an SDC lattice at the atomic level, forming an ordered solid solution (SDCIr_SG), which was formed by a sol gel process. Upon reduction in H2, Ir cations may be exsolved as nanoclusters (NCs) and as stabilized single-atoms (SAs) on an SDC surface to produce an SDCIr-O catalyst that largely features Ir—O bonding character with considerable Ir—O hybridization. Because the hydrolysis rate of Ir4+ is much slower than those of Sm3+ and Ce3+, low concentrations of the complexing agent may be used to decrease the dispersity of Ir atoms, resulting in a disordered solid solution (SDCIr). This approach may be used to synthesize an SDCIr-Ir catalyst that largely features Ir—Ir bonding character with low-level Ir—O hybridization. These tunable catalysts were characterized to gain insight into their respective properties.
Referring now to
The Ir atomic arrangement of the tunable catalysts of the disclosure was further investigated through in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) using CO as a probe, as shown in
The characterization results from the three complementary spectroscopic techniques discussed above strongly support the conclusion that tunable catalysts comprised of Ir—O and having considerable Ir—O hybridization is the major arrangement in SDCIr-O tunable catalysts, while tunable catalysts comprised of Ir—Ir and having minimal Ir—O hybridization is the major arrangement in SDCIr-Ir tunable catalysts. Thus, tunable catalysts with diverse metal-oxygen hybridization may be synthesized in accordance with embodiments of the disclosure.
Using the tunable catalysts according to embodiments of the disclosure, an electrocatalytic study may characterize the activity and selectivity of the catalysts during CO2 hydrogenation (e.g., electrohydrogenation), as shown in
Also during the electrochemical measurements, CO2 is electrolyzed and hydrogenated in the cathode (e.g., PBM-BZY/X, where X represents the SDC/Ir tunable catalyst) according to the following equations:
Because the electrochemical cells share identical components aside from the infiltrated SDC/Ir catalysts, the difference in catalytic performance may be attributed to the nature of the SDC/Ir catalysts. The catalytic behavior of SDCIr-O and SDCIr-Ir tunable catalysts may thus be compared utilizing these electrochemical cells.
Still referring to
To assess whether tuning of the metal-oxygen hybridization may help produce hydrocarbons as predicted from the DFT calculations previously discussed, the CO2 reduction of different hydrocarbon products were analyzed via gas chromatography-mass spectrometry, as shown in
To understand how SDC/Ir catalysts may impact the selectivity, operando DRIFTS measurements were performed as shown in
CO2+C2H6→CO+H2O+C2H4, and
CO2+4C2H6→CH4+2H2O+4C2H4.
The graph 236 of the thermodynamic calculations indicates that C2H6 dehydrogenation may proceed at the temperature that CO2 hydrogenation occurs with reasonable electrical energy input. For example, at about 400° C. and about 1 bar, the bias potentials are about 0.223 V for the coproduction of CO and C2H4, and about 0.348 V for the coproduction of CH4 and C2H4, respectively, as shown in the graph 236. Although utilizing H2 directly as a proton source may greatly reduce energy input and may even produce a small amount of electricity, industrial H2 production is an energy-intensive process and emits a significant amount of greenhouse gases; thus, using a high energy carrier proton source (e.g., C2H6) within the electrochemical cell may be advantageous. Moreover, the required energies calculated for the reactions shown in graph 236 are even lower than those for water splitting and CO2 splitting (both of them are above 1 V at 400° C. and 1 bar), suggesting that valuable CO2 conversion products may be obtained from different carbon resources in single step electrochemical cells (e.g., protonic ceramic electrolyzers).
Referring to
Embodiments of the disclosure will now be described with reference to
The electrolyte 264 may be formed of and include at least one electrolyte material exhibiting an ionic conductivity (e.g., H+ conductivity) greater than or equal to about 10−2 S/cm (e.g., within a range of from about 10−2 S/cm to about 1 S/cm) at one or more temperatures within a range of from about 150° C. to about 650° C. (e.g., from about 300° C. to about 500° C.). In addition, the electrolyte material may be formulated to remain substantially adhered (e.g., laminated) to the positive electrode 260 and the negative electrode 268 at relatively high current densities, such as at current densities greater than or equal to about 0.1 amperes per square centimeter (A/cm2) (e.g., greater than or equal to about 0.5 A/cm2, greater than or equal to about 1.0 A/cm2, greater than or equal to about 2.0 A/cm2, etc.). For example, the electrolyte 264 may comprise one or more of a perovskite material, a solid acid material, a polybenzimidazole (PBI) material, and a BZCYYb material (e.g., BaZr0.1Ce0.7Y0.1Yb0.1O3−δ). The material composition of the electrolyte 264 may provide the electrolyte 264 with enhanced ionic conductivity at a temperature within the range of from about 150° C. to about 650° C. as compared to conventional electrolytes (e.g., membranes employing conventional electrolyte materials, such as yttria-stabilized zirconia (YSZ)) of conventional electrochemical cells.
In some embodiments, the electrolyte 264 is formed of and includes at least one perovskite material having an operational temperature (e.g., a temperature at which the H+ conductivity of the perovskite material is greater than or equal to about 10−2 S/cm, such as within a range of from about 10−2 S/cm to about 10−1 S/cm) within a range of from about 350° C. to about 650° C. As a non-limiting example, the electrolyte 264 may comprise one or more of a yttrium- and ytterbium-doped barium-zirconate-cerate (BZCYYb), a yttrium- and ytterbium-doped barium-strontium-niobate (BSNYYb), doped barium-cerate (BaCeO3) (e.g., yttrium-doped BaCeO3 (BCY)), doped barium-zirconate (BaZrO3) (e.g., yttrium-doped BaCeO3 (BZY)), barium-yttrium-stannate (Ba2(YSn)O5.5); and barium-calcium-niobate (Ba3(CaNb2)O9). In some embodiments, the electrolyte 264 comprises BZCYYb (e.g., BaZr0.1Ce0.7Y0.1Yb0.1O3−δ and BaZr0.4Ce0.4Y0.1Yb0.1O3−δ).
As a non-limiting example, the negative electrode 268 may be comprised of a PrBaMn2O5+δ+BaZr0.7Y0.3O3−δ (PBM-BZY) cathode. As another non-limiting example, the anode 260 may be comprised of a Ni+BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (Ni—BZCYYb) anode. Further, one or more of the positive electrode 260 and the negative electrode 268 may include at least one additional catalyst material thereon, thereover, and/or therein. For example, an additional catalyst material may be included on, over, and/or within the material of the positive electrode 260 to accelerate reaction rates within the positive electrode 260 to produce H+ and e− from H2(g). As another example, a catalyst material may be included on, over, and/or within the material of the negative electrode 268 to accelerate reaction rates within the negative electrode 268 to produce a desired product from H+, e−, and one or more of CO2, CO2 hydrogenation product(s), and reaction product(s) of CO2 and/or CO2 hydrogenation product(s) and one or more other materials (e.g., CO and/or CH4). As described throughout the disclosure, the catalyst material of the negative electrode 268 may comprise Sm2O3-doped-CeO2 (SDC) supported Ir (SDC/Ir) tunable catalysts produced in different particle size ranges. The particle sizes (e.g., the Ir particle sizes) may range from angstroms to microns, and more specifically, from single-atom sizes to nanoparticle sizes. The SDC/Ir tunable catalysts may be introduced into the negative electrode 268 by infiltration and annealing to ensure a high uniformity on the cathodic (e.g., PBM-BZY) scaffold.
In additional embodiments, nano-sized (e.g., having a cross-sectional width or diameter less than about one (1) μm, such as less than or equal to about 100 nanometers (nm), less than or equal to about 20 nm, or less than or equal to about 10 nm) particles (e.g., Ir particles) may be provided on, over, and/or within the negative electrode 268 to promote reaction rates therein.
The positive electrode 260 and the negative electrode 268 may individually exhibit any desired dimensions (e.g., length, width, thickness) and any desired shape (e.g., a cubic shape, cuboidal shape, a tubular shape, a tubular spiral shape, a spherical shape, a semi-spherical shape, a cylindrical shape, a semi-cylindrical shape, a conical shape, a triangular prismatic shape, a truncated version of one or more of the foregoing, and irregular shape) as are conventionally known in the art. For example, the dimensions and the shapes of the positive electrode 260 and the negative electrode 268 may be selected relative to the dimensions and the shape of the electrolyte 264 such that the electrolyte 264 substantially intervenes between opposing surfaces of the positive electrode 260 and the negative electrode 268.
The electrochemical cell 256, including the positive electrode 260, the electrolyte 264, and the negative electrode 268, may be formed through conventional processes (e.g., rolling processes, milling processes, shaping processes, pressing processes, consolidation processes, etc.), which are not described in detail herein. The catalysts included thereon may be formed in accordance with methods of the disclosure. The electrochemical cell 256 may further be utilized as the electrochemical cell 278 described below in
During use and operation, the CO2 hydrogenation system 270 directs the H2 stream 292 (e.g., a gaseous H2 stream) from the H2 source 272 into the electrochemical apparatus 276 to interact with the positive electrode 280 of the electrochemical cell 278. Various hydrogen sources may be used, such as a substantially pure H2 stream, a diluted H2 stream, water, or a hydrocarbon stream. The H2 stream 292 may pass through electrolytes and/or membranes 232 that typically conduct protons. A potential difference (e.g., voltage) is applied between the positive electrode 280 and the negative electrode 284 of the electrochemical cell 278 by the power source 288 so that as the H2 interacts with the positive electrode 280, H atoms of the H2 source release their electrons (e−) and the generated H+ ions permeate (e.g., diffuse) across the electrolyte 282 to the negative electrode 284. At the negative electrode 284, the generated H+ exiting the electrolyte 282 reacts with CO2 delivered into the electrochemical apparatus 276 from the CO2 stream 296 directed from the CO2 source 274, e− received from the power source 288, and, optionally, one or more other materials (e.g., CO2 hydrogenation products previously formed through reactions between H+, e−, and one or more of CO2 and other CO2 hydrogenation products; reaction products of CO2 and one or more of CO2 hydrogenation products and other molecules delivered to the negative electrode 284 side of the electrochemical cell 278; etc.) to form one or more desirable products (e.g., CO and/or CH4) that then exit the electrochemical apparatus 276 as a product stream 298. By way of example only, the product stream 298 may comprise, consist of, or consist essentially of CO depending on the tunable catalyst used in the negative electrode 284. Alternatively, the product stream 298 may comprise, consist of, or consist essentially of CH4 depending on the tunable catalyst used in the negative electrode 284. The product stream 298 may, alternatively, comprise, consist of, or consist essentially of CO and CH4 at a desired ratio depending on the tunable catalyst used in the negative electrode 284.
As a non-limiting example, the positive electrode 280 (e.g., the Ni—BZCYYb anode of the disclosure) may release electrons from H2 according to the following equation:
As another non-limiting example, CO2 may be electrolyzed and hydrogenated in the negative electrode 284 (e.g., the PBM-BZY/X cathode of the disclosure, where X represents an SDC/Ir tunable catalyst of the disclosure) according to the following equations:
While specific materials for the positive electrode 260, 280, the negative electrode 268, 284, and the electrolyte 264, 282 are described herein, other materials may be used.
The carbonaceous products that may be synthesized (e.g., produced) using the CO2 hydrogenation system 270 according to embodiments of the disclosure are not limited to carbon monoxide, methane, or a combination of carbon monoxide and methane. Rather, it will be readily apparent to one of ordinary skill in the art that the methods and systems described herein may be used to synthesize a wide variety of products through hydrogenation of one or more of CO2, CO2 hydrogenation products, and derivatives of CO2 hydrogenation products. As a non-limiting example, the CO2 hydrogenation system 270 may be used to form one or more of formic acid, formaldehyde, methanol, a formate, a methylated amine, an alcohol other than methanol, a carboxylic acid, a formamide, and an aldehyde, which have the general chemical structures shown below:
where each R may individually be hydrogen; a substituted or unsubstituted alkyl group (e.g., linear, branched, or cyclic) containing from 1 carbon atom to 10 carbon atoms; or a substituted or unsubstituted aryl group or heteroaryl group. If a group is substituted, the substituent may be an alkyl, alkenyl, alkynyl, alkyl halide, aryl, aryl halide, heteroaryl, non-aromatic ring, Si(alkyl)3, Si(alkoxy)3, alkoxy, amino, ester, amide, thioether, alkylcarbonate, or thioester group.
The H2 stream 292 exiting the H2 source 272 may exhibit any pressure and any flow rate facilitating the hydrogenation of one or more of CO2 from the CO2 stream 296, CO2 hydrogenation products, and/or derivatives of CO2 hydrogenation products (e.g., reaction products of CO2 hydrogenation products and other molecules) within the electrochemical apparatus 276 to synthesize one or more desired products (e.g., one or more commodity chemicals, such as one or more of carbon monoxide, methane, formic acid, formaldehyde, an alcohol, a formate, a methylated amine, a carboxylic acid, a formamide, an aldehyde, etc.). One or more apparatuses (e.g., pumps, compressors, expanders, mass flow control devices, etc.) may be employed within the CO2 hydrogenation system 270 to adjust the pressure(s) and/or flow rate(s) of the H2 stream 292 exiting the H2 source 272.
The CO2 stream 296 entering the electrochemical apparatus 276 may be formed of and include CO2. The CO2 may be present in the CO2 stream 296 in one or more of gaseous phase and a liquid phase. The phase(s) of the CO2 (and, hence, a temperature and a pressure of the CO2 stream 296) may at least partially depend on the operating temperature of the electrochemical cell 278 of the electrochemical apparatus 276. For example, at operating temperatures less than or equal to about 250° C. (e.g., within a range of from about 150° C. to about 250° C.), the CO2 may be present in the CO2 stream 296 in a liquid phase (e.g., CO2 dissolved in an ionic liquid), a gaseous phase, or combination thereof. As another example, at operating temperatures greater than about 250° C. (e.g., greater than about 250° C. and less than or equal to about 650°), the CO2 may be present in the CO2 stream 296 in a gaseous phase. The CO2 stream 296 may only include CO2, or may include CO2 and one or more other materials (e.g., inert materials, materials to be reacted with CO2 hydrogenation products to form desired products, etc.). In some embodiments, the CO2 stream 296 is substantially free of materials other than CO2. One or more apparatuses (e.g., heat exchangers, pumps, compressors, expanders, mass flow control devices, etc.) may be employed within the CO2 hydrogenation system 270 to adjust one or more of the temperature, pressure, and flow rate of the CO2 stream 296 delivered into the electrochemical apparatus 276.
The heating apparatus 290, if present, may comprise at least one apparatus (e.g., one or more of a combustion heater, an electrical resistance heater, an inductive heater, and an electromagnetic heater) configured and operated to heat one or more of the H2 stream 292, the CO2 stream 296, and at least a portion of the electrochemical apparatus 276 to an operating temperature of the electrochemical apparatus 276. The operating temperature of the electrochemical apparatus 276 may at least partially depend on a material composition of the electrolyte 282 of the electrochemical cell 278 thereof. In some embodiments, the heating apparatus 290 heats one or more of the H2 stream 292, the CO2 stream 296, and at least a portion of the electrochemical apparatus 276 to a temperature within a range of from about 150° C. to about 650° C. (e.g., from about 300° C. to about 500° C.). In additional embodiments, such as in embodiments wherein a temperature of the gaseous H2 stream 292 exiting the H2 source 272 is already within the operating temperature range of the electrochemical cell 278 of the electrochemical apparatus 276, the heating apparatus 290 may be omitted (e.g., absent) from the CO2 hydrogenation system 270.
Still referring to
The housing structure 286 may at least partially define at least one internal chamber 300 at least partially surrounding the electrochemical cell 278. The electrochemical cell 278 may serve as a boundary between a first region 302 (e.g., an anodic region) of the internal chamber 300 configured and positioned to receive the H2 stream 292 and to direct the gaseous H2O stream 124 from the electrochemical apparatus 276, and a second region 304 (e.g., a cathodic region) of the internal chamber 300 configured and positioned receive the CO2 stream 296 and to direct the product stream 298 from the electrochemical apparatus 276. The H2 stream 292 may be substantially limited to the first region 302 of the internal chamber 300 by the configurations and positions of the housing structure 286 and the electrochemical cell 278, such that the second region 304 of the internal chamber 300 is substantially free of H2. Accordingly, the positive electrode 280 may be exposed to the H2 from the H2 stream 292 without exposing the negative electrode 284 to the H2 from the H2 stream 292. Keeping the second region 304 of the internal chamber 300 substantially free of the H2 may circumvent at least some additional processing of the CO2 hydrogenation products (and/or derivatives thereof) that may otherwise be necessary if the H2 was provided within the second region 304 of the internal chamber 300.
As shown in
Although the electrochemical apparatus 276 is depicted as including a single (i.e., only one) electrochemical cell 278 in
In addition, although the CO2 hydrogenation system 270 is depicted as including a single (i.e., only one) electrochemical apparatus 276 in
By tuning the hybridization between metal and oxygen orbital states (e.g., Ir and O orbital states), the transportation of species to and from catalytically active sites and the stabilization of specific transition states (e.g., *+CO, *COH and *HCO) may be effectively controlled to tailor the catalytic selectivity of the tunable catalyst. Thus, the precise control of a material's surface chemical environment may enable tailoring of the tunable catalyst's catalytic behavior in the electrochemical process. The tunable catalyst may be used in electrochemical cells and carbon dioxide hydrogenation systems, such as protonic ceramic electrolyzers, to enable on-site CO2 reduction. The methods (e.g., the method 246 of CO2 hydrogenation, etc.), products (e.g., the tunable catalysts comprised of Sm2O3-doped-CeO2 (SDC) supported Ir (SDC/Ir) produced in different particle size ranges), systems (e.g., the CO2 hydrogenation system 270), and apparatuses (e.g., the electrochemical apparatus 276, including the electrochemical cell 278 thereof, as well as the electrochemical cell 256) of embodiments of the disclosure facilitate simple and efficient CO2 hydrogenation using CO2 electrochemical cells at intermediate temperatures, such as temperatures within a range from about 300° C. to about 650° C. (e.g., from about 300° C. to about 500° C.).
While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, the disclosure is not limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the following appended claims and their legal equivalent. For example, elements and features disclosed in relation to one embodiment may be combined with elements and features disclosed in relation to other embodiments of the disclosure.
This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 62/706,510, filed Aug. 21, 2020, the disclosure of which is hereby incorporated herein in its entirety by this reference.
This invention was made with government support under Contract Number DE-AC07-05ID14517 awarded by the United States Department of Energy. The government has certain rights in the invention.
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| Number | Date | Country | |
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| 20220056596 A1 | Feb 2022 | US |
| Number | Date | Country | |
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| 62706510 | Aug 2020 | US |
