Oxygen-Selective Anode

Abstract

The present disclosure relates to oxygen-selective anodes and methods for their use. Provided herein are methods and systems for the immobilization of CO as solid and aqueous carbonate and bicarbonate species while inhibiting chloride ion oxidation reactions via 1) upstream strategies, such as using oxygen evolution reaction (OER)-selective anodes, and / or 2) downstream strategies, such as chlorine removal processes. An exemplary simplified flow diagram is shown in Figure 1, with detailed strategies established for the catholyte (alkaline) and anolyte (acidic) sides, respectively.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Application No. 63 / 442,298, filed January 31, 2023, the contents of which are incorporated herein by reference in their entirety.

[0002] Government Support Statement This invention was made with government support under DE-AR0001551 awarded by the U.S. Department of Energy. The government has certain rights in this invention. [Background technology]

[0003] Efficient and cost-effective means of sequestering CO2, such as mineralization, are highly desirable as a key component in addressing global climate change. Alkaline solutions can produce HCO3, either as isolated dissolved species or as a stable solid. - and CO3 2- Although it is known that alkaline solutions react with CO2 sources to produce species, there are many challenges to large-scale CO2 sequestration using alkaline solutions, including the cost of alkalinizing reagents. Alternatively, alkaline solutions can be used for water electrolysis and the resulting H + (acid) and OH - The chlorine evolution reaction (ClER) can be efficiently prepared using the separation of (basic) species into acidic and basic solutions. However, the chlorine evolution reaction (ClER) is advantageously carried out using Cl-containing solutions such as naturally occurring brine or seawater. - The undesired ClER reaction, which occurs in competition with the desired oxygen evolution reaction (OER), hinders the development of such processes for large-scale CO capture and removal. Therefore, there is a need for an electrolytic system for CO capture and removal that mitigates the undesired production of free chlorine species and chlorine gas. Summary of the Invention

[0004] In certain aspects, provided herein are oxygen-selective anodes. In further aspects, provided herein are methods of electrolyzing saline, wherein an oxygen-selective anode (OSA) is used. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 shows a simplified block flow diagram illustrating brine electrolysis as a carbon removal route.

[0006] [Figure 2] 1 shows the acid neutralization capacity (mol H+ / kg solute) of various exemplary deoxidizers of the present disclosure, established based on their chemical composition. Generally, as the acid neutralization capacity increases, a smaller amount (by mass) of solute is used.

[0007] [Figure 3] 1 shows the dechlorination capacity (mol Cl / kg solute) of various dechlorinating agents of the present disclosure, established based on their chemical composition. Generally, as the dechlorination capacity increases, a smaller amount (by mass) of solute is used.

[0008] [Figure 4] FIG. 1 shows a schematic diagram in cross-section of an exemplary flow-through, single-compartment electrolyzer.

[0009] [Figure 5] 5 shows the pH of each of the effluents recorded at various times from the system shown in FIG.

[0010] [Figure 6] 5 shows the chemical composition of precipitated solids from the cathode chamber of the system shown in FIG.

[0011] [Figure 7] 1 shows inorganic carbon (IC, e.g., HCO3 −, CO3 2+) concentration over time by continuously aerating the catholyte and cathode chamber with a 400 ppm CO2 gas mixture.

[0012] [Figure 8] 1 shows the concentration of chlorine in the anolyte over time and (inset) an exemplary Mn oxide coated anode.

[0013] [Figure 9] Figure 1 shows the results of an exemplary continuous stirred reactor experiment using forsterite-olivine at various solid / liquid ratios (50, 125, 250 g / L) with acidified seawater (initial pH = 2) and a hydraulic residence time of 10 minutes.

[0014] [Figure 10] 1 shows an exemplary coating of Ir—Sn MMO (white) on a Ti substrate (grey) with the approximate thickness of the MMO layer indicated.

[0015] [Figure 11] 1 shows an exemplary coating of a Mn oxide outer layer (gray) on top of an Ir—Sn MMO layer (dark gray / black) with the approximate thickness of the Mn oxide layer indicated.

[0016] [Figure 12] 1 shows an exemplary coating of Ir-Ta MMO (white) on a Ti substrate (grey) with the approximate thickness of the MMO layer indicated.

[0017] [Figure 13] FIG. 1 shows an exemplary coating of a Mn oxide outer layer (dark gray, in focus) on an Ir-Ta MMO surface (light gray, out of focus), with the approximate thickness of the Mn oxide layer indicated.

[0018] [Figure 14] 1 shows an exemplary surface morphology of the surface of an Ir—Sn MMO layer.

[0019] [Figure 15] 1 shows an exemplary surface morphology of the surface of an Ir-Ta MMO layer.

[0020] [Figure 16] 1 shows an exemplary surface morphology of the surface of the Mn oxide outer layer.

[0021] [Figure 17] 1 shows an exemplary surface morphology at high magnification of the Mn oxide outer layer.

[0022] [Figure 18] 1 shows an exemplary surface morphology and roughness of the Mn oxide outer layer.

[0023] [Figure 19] 1 shows a schematic diagram of an exemplary arrangement of a Ti substrate, an MMO inner layer, and an Mn oxide outer layer.

[0024] [Figure 20] 1 shows X-ray diffraction (XRD) phase analysis of the Ti substrate, the Ir-Ta MMO inner layer, and the Mn oxide outer layer.

[0025] [Figure 21] 1 shows testing of an exemplary oxygen-selective anode (comprising a TaIrOx MMO layer) of the present disclosure in a representative electrolyzer cell.

[0026] [Figure 22A] 1 shows the accelerated life test (ALT) performance of an exemplary anode based on anode substrate 2 under constant and cyclic voltage conditions. Three distinct stages were revealed by the ALT test, including stabilization (Stage I), stable (Stage II), and linear degradation (Stage III).

[0027] [Figure 22B] The change in ClER selectivity under cyclic voltage loading over 150 hours is shown.

[0028] [Figure 22C]Figure 1 shows the ALT performance of PGM-based anodes with different substrates under constant voltage. The anode with a higher substrate Ir loading (anode substrate 3) showed significantly better performance than anode substrate 2, which had a lower substrate Ir loading.

[0029] [Figure 22D] We demonstrate that the longer duration of stage II, as observed in ClER generation, correlated with the slower degradation rate observed in stage III. ALT experiments were performed in a flow-through electrolytic cell using 0.5 M NaCl as the electrolyte.

[0030] [Figure 23A] 1 shows SEM images of the surface of an exemplary MnOx coated PGM-based electrode (with anode substrate 2) plated with 0.6 M H2SO4 (top) or 2 M H2SO4 (bottom).

[0031] [Figure 23B] Figure 1 shows the ALT performance of MnOx coated PGM-based electrodes (anode substrate 2) plated with either 0.6 M H2SO4 or 2 M H2SO4.

[0032] [Figure 24A] 24A and 24B show ClER selectivity (24A) and cell voltage (24B) obtained from ALT durability experiments of PGM-free electrodes electroplated at various H2SO4 concentrations and various processes. [Figure 24B] 24A and 24B show ClER selectivity (24A) and cell voltage (24B) obtained from ALT durability experiments of PGM-free electrodes electroplated at various H2SO4 concentrations and various processes. DETAILED DESCRIPTION OF THE INVENTION

[0033] Electrochemical brine alkalinization is a transformative approach for CO2 removal. For example, seawater electrolysis-mediated carbon fixation can address (i) the ocean-atmosphere equilibrium of gas-phase and dissolved CO2 (e.g., about 2 mM dissolved inorganic carbon (DIC)), and (ii) the large abundance of divalent alkali cations in seawater (e.g., 55 mM Mg 2+ or 10.5 mM Ca 2+ ). These attributes can be exploited to electrochemically force carbonate and hydroxide mineral formation (e.g., Ca-, Mg-carbonates, hydroxides, and their variants), which consume dissolved CO2 and absorb additional atmospheric CO2 as carbonates / bicarbonates. Electroalkalinization does not require expensive alkaline additives (e.g., NaOH) but instead generates hydroxide ions (OH - ), which can be affected by electrochemical pH swings in brine near the flow-through electrode surface, promoting heterogeneous and homogeneous nucleation and growth of carbonate and hydroxide mineral precipitates. However, brine electrolysis typically involves oxidation of chloride ions and the formation of free chlorine species (e.g., Cl, ClO) on the anode. - Chlorine oxidation is generally harmful and should be suppressed unless these species can be recovered prior to discharge of the electrolyzer effluent. Provided herein are methods and systems for the immobilization of CO as solid and aqueous carbonate and bicarbonate species while inhibiting chloride ion oxidation reactions via 1) upstream strategies, such as using oxygen evolution reaction (OER)-selective anodes, and / or 2) downstream strategies, such as chlorine removal processes. An exemplary simplified flow diagram is shown in FIG. 1, with detailed strategies established for the catholyte (alkaline) and anolyte (acidic) sides, respectively.

[0034] Direct seawater electrolysis selective to unwanted ClER has been attempted and reported for many years. In summary, ClER suppression is generally enabled by designing anode catalysts along two routes: 1) low overpotential anodes that can operate below the ClER kick-off potential, and 2) anodes that can evaporate Cl from the water-splitting surface. - Cl that shields -Interrupting anode.

[0035] The low overpotential anode takes advantage of the fact that the ClER (Equation 1) requires a slightly higher thermodynamic (TD) potential than the desired OER (Equation 2). [ka]

[0036] Seawater Cl - At high concentrations (approximately 0.5 M), the TD potentials of ClER and OER show a gap of approximately 0.2-0.3 V at acidic pHs between 0 and 3. This gap is maximized to approximately 0.48 V at pHs above 7.5. Metal oxide electrocatalysts that exhibit promising overpotentials have been developed, but such pathways are limited to low current densities (i.e., 10 A / m 2 The overpotential of PGM catalysts (platinum group metals, e.g., IrOx) is limited only by the acidity (<0.3 V) and neutral to alkaline pH. Most metal oxides are unstable when used in acidic conditions. Additionally, the overpotential of even PGM catalysts (platinum group metals, e.g., IrOx) is too high to enable OER selectivity due to the potential gap being reduced to less than 0.3 V.

[0037] Alternatively, Cl - The blocking anode is protected by a double layer coating, e.g., by Cl - The blocking is achieved by overlaying the OER catalyst layer. - The barrier outer layer is typically a barrier to water, oxygen, and cationic species (Na + , H + etc.) through the outer layer to the active layer underneath, while negatively charged Cl - Many anodes have been demonstrated to have high OER selectivity, most of which are made of manganese oxide (MnOx) and Cl - Others contain a barrier coating layer similar to MnOx. - Nafion or Si- and Ni-hydroxides are used to act as a barrier. [Table 1-1] [Table 1-2]

[0038] Cl - While the compatibility of the blocking layer and OER catalyst layer is important, the durability and overpotential of the anode are based on the underlying OER catalyst. As shown in Table 1, the most durable anodes generally rely on heavy loadings of IrOx, which can durably withstand acidic and chlorinated environments. For example, either pure IrO2 or an IrO2 content of over 80 at.% (over 90 wt.%) is required to ensure anode life. However, tightening global Ir production and prices pose a barrier to the large-scale production and use of these anodes. Therefore, there is a strong incentive to replace Ir (and PGMs in general) with cheaper and more abundant elements while maintaining durability in both the chlorinated and acidic environments found in PGM-based electrodes. Several PGM-free metal oxides have been investigated that can withstand acidic environments but exhibit poor durability in high-chlorine environments (Table 2). [Table 2]

[0039] Cl in solution - The presence of Cl is clearly detrimental and causes degradation of the PGM-free oxide catalyst, thus resulting in a substantially reduced lifespan. - The addition of a barrier outer layer (e.g., coating) prevents the PGM-free catalyst from - This can provide protection from corrosion, allowing for longer life and / or better performance.

[0040] Therefore, anodes with dual layer coatings can solve these OER selectivity and stability challenges. The electrodes of this disclosure are described in two categories: PGM-based electrodes and PGM-free electrodes.

[0041] PGM-based electrodes To achieve an IrOx-based OER-selective anode, literature sources report IrO loadings greater than 80%, which are expensive and therefore difficult to commercialize. Therefore, in certain embodiments, the oxygen-selective anode of the present disclosure includes a TaIr-oxide (TaIrOx doped with Ru, Sn, and Zn oxides, see Table 3) coated electrode containing a Ti core (e.g., a Ti plate or Ti mesh, Table 3). A manganese oxide (MnOx) layer was applied to achieve OER selectivity, for example, according to the procedure of Example 3. Three TaIrOx-coated substrates with unique compositions and low Ir loadings were fabricated and analyzed. The results of these analyses are shown in Table 3. [Table 3]

[0042] The MnOx-coated anode 1 (17.8 at% IrO2 loading) was tested in an exemplary flow-through electrolyzer using simulated seawater (Instant Ocean Seawater (IOSW)). ClER selectivity was determined by measuring the free chlorine concentration in the anolyte effluent using a UV-vis spectrometer. At operating current densities (e.g., 300 A / m 2 ), the ClER selectivity remains below 3% (i.e., >97% OER) under cyclic voltage conditions. No significant signs of degradation were observed over the test period, and the cell voltage remained unchanged, highlighting the stability of the TaIrSnOx layer.

[0043] Accelerated Life Testing (ALT) More typical operating current densities (300A / m 2 ) compared to a higher current density (1000A / m 2 Accelerated life testing was performed by applying the ALT (Area 1). Importantly, a well-established equation (Equation 3) can be used to estimate the service life using the duration measured in ALT: [ka] During the ceremony, J. ALT is the current density used in the accelerated life test (e.g., 1000 A / m 2 ) and J op is the operating current density (e.g., 300 A / m 2 ) and the exponent of 1.7 is an empirical constant. Thus, equation 4 yields: Predicted lifespan = 7.74 x ALT lifespan (4)

[0044] The ALT was used to investigate the effect of cyclic or constant voltage loading conditions on predicted lifetime (Figure 22A). Interestingly, three phases are typically observed in the ALT. ClER selectivity declines in the first 24-48 hours (phase I), typically due to the addition of ions (H + , Na + The cell potential decrease (Figure 22B) is likely due to the hydrolysis and stabilization of MnOx in the oxidized environment. The low ClER selectivity is maintained for a short period (phase II) and then increases at a steady rate (phase III). As observed, phase I is generally similar for all experiments, while phases II-III characterize the electrode's durability and depend on the specific composition of the electrode. For example, when the anode was subjected to cyclic voltage loading, the duration of phase II was shorter and the degradation rate in phase III was faster. In particular, cyclic loading induced a significant reduction in lifetime (approximately 40%), and the selectivity failure was preceded by a gradual spike in ClER selectivity after every voltage cycle (see Figure 22B), which appeared to interfere with the stabilization of MnOx. Turning the current on and off caused the anode surface to be exposed to H + Enrichment from Na + The switch to a Na-rich ionic environment led to a structural change of MnOx between its hydrogenated and Na-rich forms. This likely resulted in structural damage to the MnOx layer, resulting in a shortened lifetime. Failure analysis at the end of each experiment revealed that the degraded MnOx layer was responsible for the loss of ClER selectivity.

[0045] Furthermore, substrate dissolution can also cause MnOx segregation and loss of OER selectivity. Although it is slow, dissolution of even a few atomic layers of TaIrOx can induce delamination between the two layers. In addition, cyclic loading also promotes the reconstruction of the substrate's crystalline structure, leading to accelerated delamination between the TaIrOx and MnOx layers. Therefore, substrate regeneration becomes more important to alleviate the delamination problem and extend the OER selectivity lifetime.

[0046] The second set of ALTs aimed to evaluate the effect of substrate IrO loading. Tests were conducted on TaIrOx substrates from Anode 2 (24.8 at% IrO) and Anode 3 (62.4 at% IrO) under potentiostatic conditions. As shown in Figures 22C and 2D, a higher IrO content in Anode 3 not only extended the duration of Stage II but also reduced the degradation rate observed in Stage III.

[0047] In certain embodiments, the MMO layer comprises Ta, Ir, and O. In certain embodiments, the first metal oxide comprises Ta and the second metal oxide comprises Ir. In some embodiments, the MMO layer comprises Sn, Ir, and O. In certain embodiments, the first metal oxide comprises Sn and the second metal oxide comprises Ir. In some embodiments, the MMO layer comprises Co, Mn, and O. In certain embodiments, the first metal oxide is Co and the second metal oxide is Mn. In certain embodiments, the MMO layer further comprises a dopant selected from Ta, Co, and Nb, or a combination thereof.

[0048] In certain embodiments, the MMO layer comprises about 5 atomic percent (at.%) Ir to about 65 at.% Ir. In further embodiments, the MMO layer comprises about 15 at.% Ir to about 30 at.% Ir. In certain preferred embodiments, the MMO layer comprises about 5.77 at.% Ir. In other preferred embodiments, the MMO layer comprises about 7.03 at.% Ir. In some embodiments, the MMO layer comprises about 17 at.% Ir to about 65 at.% Ir. In certain preferred embodiments, the MMO layer comprises about 62.4 at.% Ir.

[0049] In some embodiments, the outer layer further comprises an outer layer dopant. In certain embodiments, the outer layer further comprises two or more outer layer dopants. In certain preferred embodiments, each of the outer layer dopants is a transition metal. In some preferred embodiments, the outer layer dopant is selected from a transition metal oxide, a transition metal hydroxide, and a transition metal oxyhydroxide.

[0050] In certain embodiments, an outer layer is coated onto the surface of the MMO layer.

[0051] In some embodiments, the outer layer is coated intermixed (eg, mixed) with the MMO layer.

[0052] In certain embodiments, the MMO layer comprises one or more additional MMO layers. In some embodiments, the MMO layer comprises one additional MMO layer. In certain embodiments, the MMO layer comprises two additional MMO layers. In some embodiments, the MMO layer comprises three additional MMO layers. In certain embodiments, the MMO layer comprises four additional MMO layers. In some embodiments, the MMO layer comprises five additional MMO layers. In certain embodiments, the additional MMO layer(s) comprise an element selected from Groups 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14. In further embodiments, the additional MMO layer(s) comprise a metal oxide comprising Ta, Ru, Ti, Y, Sr, Sn, La, Ce, or Ir. In certain preferred embodiments, the additional MMO layer(s) have a composition as defined herein.

[0053] In certain embodiments, the substrate contacts the MMO layer at a substrate-MMO junction, and the MMO layer contacts the outer layer at an MMO-outer layer junction. In some embodiments, the substrate-MMO junction is substantially flat. In other embodiments, the substrate-MMO junction is substantially rough. In some embodiments, the substrate-MMO junction is a bulk heterojunction. In certain embodiments, the MMO-outer layer junction is substantially flat. In other embodiments, the MMO-outer layer junction is substantially rough. In certain embodiments, the MMO-outer layer junction is a bulk heterojunction.

[0054] In certain preferred embodiments, the outer layer has a surface morphology comprising spheres. In further preferred embodiments, the spheres have diameters in the nanometer range. In other preferred embodiments, the spheres have diameters in the micrometer range. In certain embodiments, the spheres have diameters between 0.01 μm and 10 μm. In certain embodiments, the spheres have a composition defined in this disclosure (e.g., the spheres comprise a mixed metal oxide specified herein). In certain embodiments, the spheres comprise ramsdellite (γ-MnO). In some embodiments, the MMO layer has a surface morphology substantially as shown in FIG. 14. In certain embodiments, the MMO layer has a surface morphology substantially as shown in FIG. 15. In some embodiments, the outer layer has a surface morphology substantially as shown in FIG. 16. In certain embodiments, the spheres have a morphology as shown in FIG. 17. In some embodiments, the spheres have a morphology as shown in FIG. 17. In certain preferred embodiments, the surface morphology of the outer layer increases the surface area of ​​the outer layer by 1× to 100×.

[0055] In certain embodiments, the oxygen-selective anode further includes a tie layer disposed between the MMO layer and the outer layer. In some embodiments, the tie layer includes a copolymer including at least one unit of a first monomer and at least one unit of a second monomer, where the first monomer is tetrafluoroethylene and the second monomer is a sulfonated perfluorovinyl ether. In certain embodiments, the tie layer includes a sulfonated tetrafluoroethylene copolymer. In some embodiments, the tie layer includes a compound having CAS Registry Number 66796-30-3.

[0056] In one particular embodiment, the MMO layer comprises Ta, Ir, and O, and the oxygen-selective anode has a current of about 300 A / m 2 In some embodiments, the MMO layer comprises Ta, Ir, and O, and the oxygen-selective anode has a lifetime of about 7353 hours.

[0057] In certain embodiments, the oxygen-selective anode has a selectivity for the OER of greater than about 97%. In some embodiments, the oxygen-selective anode has a selectivity for the OER of about 97% to about 99%. In preferred embodiments, the oxygen-selective anode has a selectivity for the OER of greater than about 99%.

[0058] In certain embodiments, the outer layer has a surface with an average areal roughness (Sa) of about 1 μm to about 10 μm. In further embodiments, the outer layer preferably has a surface with an average areal roughness (Sa) of about 1.27 μm, about 2 μm, about 4 μm, or about 10 μm.

[0059] In certain embodiments, the outer layer has a surface that is substantially flat (e.g., uniform). In further embodiments, the outer layer has a surface with an average areal roughness (Sa) of 0 μm to about 1 μm. In further embodiments, the outer layer has a surface with an average areal roughness (Sa) of about 0.1 μm, about 0.2 μm, about 0.5 μm, or about 1 μm.

[0060] In certain embodiments, the substrate is solid (e.g., non-porous). In other embodiments, the substrate is porous. In some embodiments, the substrate is a plate, a mesh, a felt, a foam, a fiber, and a particle, or a combination thereof. In some embodiments, the substrate is a plate. In certain embodiments, the substrate is a mesh. In some embodiments, the substrate is a felt. In some embodiments, the substrate is a foam. In some embodiments, the substrate is a fiber. In some embodiments, the substrate is a particle. In some embodiments, the substrate is a combination of a plate, a mesh, a felt, a foam, a fiber, or a particle.

[0061] PGM-free anode Despite the long life of PGM-based electrodes, PGM metals have low abundance in the Earth's crust, and Ir is the rarest of the PGMs. Therefore, PGM-free anodes are desirable to complement PGM-based electrodes.

[0062] As shown by Table 2, Co and Mn-based catalysts have been identified as durable catalytic components that can be used in acidic environments. Thus, the PGM-free anodes described herein also employ the bilayer structure successfully used in the PGM-based electrodes described above, but the TaIrOx-based OER catalyst layer is replaced with, for example, a CoMnOx catalyst. As shown in Figure 24A, two processes have been attempted to fabricate PGM-free anodes, the main difference being the use of a CoMnOx catalyst and a Cl - The barrier layer was tested with or without the addition of Nafion as a binder. In addition, two different MnOx morphologies were tested, which were imparted by varying the H2SO4 concentration used in the electroplating process, as discussed above and in Example 5 (see also Figure 23A).

[0063] Preliminary durability tests of PGM-free anodes were performed at 150A / m 2 This was done under lower current densities than the CoMnOx and most similar transition metal (e.g., Ni, Fe) oxides, because they undergo redox reactions at higher anodic potentials, leading to catalyst decomposition. For example, solid MnO2 reacts with soluble permanganate ions (MnO4 - ) can be oxidized to Cl - Even in environments that do not contain PGM-free catalysts, PGM-free catalysts typically outperform PGM catalysts (1000 A / m 2 The current density is one order of magnitude lower than that of the conventional ferroelectric capacitors (100 A / m 2 (see below).

[0064] The degradation behavior of PGM-free anodes differs from that of PGM-based anodes. For anodes fabricated by Process A, which has a lower H2SO4 concentration during electroplating, the evolution of ClER selectivity showed an initial steady state and then increased exponentially (Figure 24A). A similar trend was observed in the evolution of cell voltage (Figure 24A), where a steep increase in cell voltage indicates deactivation of the CoMnOx catalyst. Notably, while ClER selectivity increased at a fairly early stage, the cell voltage remained stable up to 600 hours, suggesting that CoMnOx deactivation was due to ClER induced by a damaged MnOx layer. - These results suggest that the degradation of the MnOx layer is likely caused by free chlorine species and free chlorine species. Therefore, it is important to improve the integrity of the MnOx layer so that it can better protect the underlying CoMnOx. Preliminary results indicate that modifying the concentration of acid in the electroplating precursor results in a MnOx layer that is much more compatible with CoMnOx, resulting in significantly lower ClER selectivity (less than 1%, see Figures 24A and 24B, sample Process A). The cell voltage of the same sample was measured for over 800 hours without any signs of CoMnOx deactivation. In addition, adding Nafion as a binder (Process B) slightly improved stability, but ClER selectivity was on the same order as Process A. The sharp increase in ClER selectivity at over 600 hours also led to an increase in cell potential, as shown in Figure 24B.

[0065] In certain embodiments, the MMO layer comprises Co, Mo, Sn, and O. In some embodiments, the first metal oxide comprises Co, the second metal oxide comprises Mo, and the third metal oxide comprises Sn.

[0066] In some embodiments, the outer layer further comprises an outer layer dopant. In certain embodiments, the outer layer further comprises two or more outer layer dopants. In certain preferred embodiments, each of the outer layer dopants is a transition metal. In some preferred embodiments, the outer layer dopant is selected from a transition metal oxide, a transition metal hydroxide, and a transition metal oxyhydroxide.

[0067] In certain embodiments, an outer layer is coated onto the surface of the MMO layer.

[0068] In some embodiments, the outer layer is coated intermixed (eg, mixed) with the MMO layer.

[0069] In certain embodiments, the MMO layer comprises one or more additional MMO layers. In some embodiments, the MMO layer comprises one additional MMO layer. In certain embodiments, the MMO layer comprises two additional MMO layers. In some embodiments, the MMO layer comprises three additional MMO layers. In certain embodiments, the MMO layer comprises four additional MMO layers. In some embodiments, the MMO layer comprises five additional MMO layers. In certain embodiments, the additional MMO layer(s) comprise an element selected from Groups 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14. In further embodiments, the additional MMO layer(s) comprise a metal oxide comprising Ta, Ru, Ti, Y, Sr, Sn, La, Ce, or Ir. In certain preferred embodiments, the additional MMO layer(s) have a composition as defined herein.

[0070] In certain embodiments, the substrate contacts the MMO layer at a substrate-MMO junction, and the MMO layer contacts the outer layer at an MMO-outer layer junction. In some embodiments, the substrate-MMO junction is substantially flat. In other embodiments, the substrate-MMO junction is substantially rough. In some embodiments, the substrate-MMO junction is a bulk heterojunction. In certain embodiments, the MMO-outer layer junction is substantially flat. In other embodiments, the MMO-outer layer junction is substantially rough. In certain embodiments, the MMO-outer layer junction is a bulk heterojunction.

[0071] In certain preferred embodiments, the outer layer has a surface morphology comprising spheres. In further preferred embodiments, the spheres have diameters in the nanometer range. In other preferred embodiments, the spheres have diameters in the micrometer range. In certain embodiments, the spheres have diameters between 0.01 μm and 10 μm. In certain embodiments, the spheres have a composition defined in this disclosure (e.g., the spheres comprise a mixed metal oxide specified herein). In certain embodiments, the spheres comprise ramsdellite (γ-MnO). In some embodiments, the MMO layer has a surface morphology substantially as shown in FIG. 14. In certain embodiments, the MMO layer has a surface morphology substantially as shown in FIG. 15. In some embodiments, the outer layer has a surface morphology substantially as shown in FIG. 16. In certain embodiments, the spheres have a morphology as shown in FIG. 17. In some embodiments, the spheres have a morphology as shown in FIG. 17. In certain preferred embodiments, the surface morphology of the outer layer increases the surface area of ​​the outer layer by 1× to 100×.

[0072] In certain embodiments, the oxygen-selective anode further includes a tie layer disposed between the MMO layer and the outer layer. In some embodiments, the tie layer includes a copolymer including at least one unit of a first monomer and at least one unit of a second monomer, where the first monomer is tetrafluoroethylene and the second monomer is a sulfonated perfluorovinyl ether. In certain embodiments, the tie layer includes a sulfonated tetrafluoroethylene copolymer. In some embodiments, the tie layer includes a compound having CAS Registry Number 66796-30-3.

[0073] In one particular embodiment, the MMO layer comprises Co, Mn, and O, and the oxygen-selective anode has a current of about 150 A / m 2 In some embodiments, the MMO layer comprises Co, Mn, and O, and the oxygen-selective anode has a lifetime of about 300 hours to greater than 1000 hours measured at a current density of about 300 A / m 2 The measured lifetime is approximately 500 hours at an operating current density of 1000 Ω / s.

[0074] In certain embodiments, the oxygen-selective anode has a selectivity for the OER of greater than about 97%. In some embodiments, the oxygen-selective anode has a selectivity for the OER of about 97 to about 99%. In preferred embodiments, the oxygen-selective anode has a selectivity for the OER of greater than about 99%.

[0075] In certain embodiments, the outer layer has a surface with an average areal roughness (Sa) of about 1 μm to about 10 μm. In further embodiments, the outer layer preferably has a surface with an average areal roughness (Sa) of about 1.27 μm, about 2 μm, about 4 μm, or about 10 μm.

[0076] In certain embodiments, the outer layer has a surface that is substantially flat (e.g., uniform). In further embodiments, the outer layer has a surface with an average areal roughness (Sa) of about 0 μm to about 1 μm. In further embodiments, the outer layer has a surface with an average areal roughness (Sa) of about 0.1 μm, about 0.2 μm, about 0.5 μm, or about 1 μm.

[0077] In certain embodiments, the substrate is solid (e.g., non-porous). In other embodiments, the substrate is porous. In some embodiments, the substrate is a plate, a mesh, a felt, a foam, a fiber, and a particle, or a combination thereof. In some embodiments, the substrate is a plate. In certain embodiments, the substrate is a mesh. In some embodiments, the substrate is a felt. In some embodiments, the substrate is a foam. In some embodiments, the substrate is a fiber. In some embodiments, the substrate is a particle. In some embodiments, the substrate is a combination of a plate, a mesh, a felt, a foam, a fiber, or a particle.

[0078] Mineralization and removal of CO2 using alkaline solutions Saltwater (e.g., seawater) alkalinization is achieved by using alkalinity (e.g., OH) generated locally at the cathode as a result of the hydrogen evolution reaction (HER).- It can be induced at an overpotential (e.g., 0.5 V or less) resulting in the formation of a cation (ion). [ka]

[0079] This reaction not only produces hydrogen, which can be collected as a clean fuel, but also produces alkalinity that can react with atmospheric or concentrated CO2 (e.g., 400 ppm to 100%). [ka]

[0080] Alternatively, multivalent cations (e.g., Ca 2+ , Mg 2+ ) in combination with CO2 creates an alkaline (OH - ions) overcome the barrier to Ca- and Mg-based mineral precipitation. The net reaction of calcium and magnesium ions is: [ka]

[0081] In many cases, CO2 is captured in solid carbonate and / or hydroxycarbonate form. On the other hand, calcium and magnesium carbonate precipitation may be kinetically limited at low DIC concentrations (e.g., less than 10 mM), and therefore alkalinity may also force hydroxide precipitation according to the following reaction: [ka] Its dissolution in water (e.g., seawater) also results in HCO3 - / CO3 2-ions, resulting in the reduction of atmospheric or concentrated CO2 (400 ppm to 100%) (as shown in Reactions 6-7). Strategies and conditions (e.g., direct hydroxide carbonation) for the formation of calcium and magnesium carbonates and hydroxycarbonates, e.g., calcite (CaCO3), aragonite (CaCO3), nesquehonite (MgCO3·3H2O), and hydromagnesite (Mg5(CO3)4(OH)2·4H2O), can also be utilized, thereby resulting in solid CO2 mineralization. In other embodiments, carbon is released from the solution (i.e., HCO3 - / CO3 2- ion) form, thereby making it less alkaline (OH - ) is required for every mole of CO2 mineralized. These conditions can be achieved by equilibrating alkalized brine with air (i.e., 400 ppm CO2) or a concentrated CO2 stream (400 ppm to 100%), resulting in two extreme cases: (1) production of solid carbonate / hydroxycarbonate (i.e., 100% solid CO2 sequestration), and (2) aqueous CO2 sequestration. Following the former, 1 mole of CO2 is converted to 2 moles of hydroxyl ions (OH - ) to produce 1 mol of CaCO3, MgCO3, or other alkali metal (e.g., Na, K, etc.) carbonate. In the latter case, every 1 mol of hydroxide ion (OH-) results in the absorption of 1-2 mol of CO2, resulting in the formation of aqueous HCO3 - / CO3 2- CO2 fixation can be carried out by using carbonation reactors or by deploying alkaline products (solids and solutions) on land and / or at sea that allow for the reduction of atmospheric CO2. In either case, the products from CO2 fixation should fall within the two extremes and result in a combination of solid and aqueous carbonate species.

[0082] Treatment of the anode products Meanwhile, acid is produced at the anode from the oxygen evolution reaction (OER). [ka]

[0083] In the case of salt water electrolysis (containing NaCl), the chlorine evolution reaction (ClER) occurs: [ka] competes with OER at the anode, and although OER is thermodynamically more favorable (i.e., OER begins at a lower potential), ClER is kinetically faster because less electron transfer is involved. On a large scale, Cl evolution and the generation of free chlorine species (e.g., Cl, ClO) - The formation of HClO, etc. is generally harmful and should be suppressed.

[0084] In certain embodiments, manganese oxide-based (MnOx-) anodes are used to inhibit chlorine evolution and achieve ClER efficiencies of less than 25% and OER efficiencies of at least 75%. Generally, the manganese oxide-based anodes of the present disclosure can be doped or functionalized with other transition metals (e.g., Ir, Ta, Ru, Pd, Sn, Pb, Mn, Co, Fe, Mo, Sn, W, Cr, Ni, or Ti) for enhanced selectivity and durability, which can be present as oxides, hydroxides, oxyhydroxides, or any combination thereof. Additionally, manganese oxide-based (MnOx-) catalysts can be directly coated (e.g., via electroplating, electrodeposition, sol-gel coating, chemical / physical vapor deposition, sintering, etc.) onto conductive or semiconductive substrates (e.g., metals, metal oxides, metal silicates, metal carbonates, metal phosphides, metal sulfides, metal selenides, graphite, graphene, carbon nanotubes, glassy carbon, or any combination thereof). In other embodiments, the MnOx-catalyst is mixed with or coated on other catalysts, for example, transition metals such as Ir, Ta, Ru, Pd, Sn, Pb, Mn, Co, Fe, Mo, Sn, W, Cr, Ni, or Ti, oxides, hydroxides, oxyhydroxides, or any combination thereof, to promote anode stability and conductivity.

[0085] In certain embodiments, the use of an OER-selective anode results in the production of a molar equivalent of acid in proportion to the amount of chlorine avoided. Therefore, the use of a thicker porous separator between the anode cell and cathode cell performing seawater electrolysis may be necessary compared to a chlorine-generating system. In certain embodiments, the porous separator is an acid-resistant, hydrophilic ceramic (e.g., aluminum oxide, zirconium oxide, silicon dioxide, asbestos, hydrous aluminum phyllosilicate, clay, or any combination thereof), polymer (e.g., cellulose, polyvinyl chloride, organic rubber, polyolefin, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, epoxy resin, silicone, or any combination thereof), or ceramic-polymer composite separator. The separator material can be used as is or can be treated to enhance surface hydrophilicity. The median pore size of the separator can range from 10 nm to 500 μm, and the thickness can range from 100 μm to 5 mm.

[0086] With ClER minimized upstream by an OER-selective anode, the remaining chlorine and acid species in the anolyte effluent can be further neutralized and / or removed (e.g., by downstream dechlorination and deoxidation). In certain embodiments, based on a conservatively estimated OER efficiency of 90%, 1.1 to 2.3 kmoles of Cl (or hydrolyzed free chlorine species: HClO and ClO) can be removed. -Over 20–41 kmol of H+ (in the acidified anolyte) is produced for every ton of CO2 mineralized as bicarbonate / carbonate, accompanied by the presence of HCl. External sources of inexpensive, abundant, and relatively reactive materials can be used to re-alkalinize the anolyte, provided that the cathode alkalinity is fully utilized for CO2 mineralization. Furthermore, once the anolyte is neutralized to a pH above 6, the evolved Cl2 can be retained / reabsorbed as a hydrolytic species, enabling an in-solution dechlorination approach. There is a wide range of mineral mixtures (e.g., rock, industrial waste) that can be used as neutralizing and, optionally, further alkalizing reagents. The selection of the neutralizing solute is based on two material parameters: a) acid-neutralizing capacity, established by elemental composition, and b) the material's dissolution rate, which is primarily governed by solution pH. Exemplary reagents are listed in Table S1 and shown in Figures 2 and 3. The acid neutralization capacities of exemplary reagents span the order of magnitude (5-50 mol H+ / kg), and some of these reagents are abundantly available in granular form (e.g., the fly ash reservoir in the United States alone holds over 3 billion tons of residual material). In addition, common marine alkalizing minerals (e.g., those listed in Table S1) can be used to treat acidic anolyte.

[0087] Chlorine and its hydrolyzed species (e.g., HClO, ClO - Due to the strong oxidizing properties of chlorine, free chlorine species find applications in wastewater / gas treatment, etc. Chlorinated anolytes have been used in 1) preventing biofouling of filtration membranes (e.g., hypochlorite shock), 2) mixing with wastewater to purify organic and inorganic matter (e.g., cyanide, arsenic, heavy metals), and 3) scrubbing flue gas to remove harmful H2S and SO2. x It can be dechlorinated through many waste treatment processes, such as by oxidizing (e.g., SO2) and NOx (e.g., NO, NO2) gases. Additionally, ferrous iron (Fe) naturally present in minerals / rocks used for acid neutralization can be dechlorinated. 2+) or other low-valent metal species (e.g., Mn, Ni, Cr, Ti, etc., or any combination thereof) can also effectively reduce chlorine to chlorides, providing a co-deoxidation and dechlorination pathway. Similarly, solid industrial wastes such as copper slag are enriched in ferrous species (e.g., fayalite) and alkali metal oxides, which can potentially neutralize acidity while reducing free chlorine (see Figure 3).

[0088] Modifications to the System of the Present Disclosure Naturally enhanced aeration or surface area enhancement of the catholyte can be achieved by placing the catholyte and produced hydroxides in the ocean or on land to ensure effective mixing and CO2 equilibration. When released into the ocean, the catholyte can function as a seawater alkalinizing reagent to promote atmospheric CO2 reduction and combat ocean acidification. In certain embodiments, catholyte carbonation can be carried out in a separate carbonation unit or alkaline process chamber using atmospheric or more concentrated CO2 streams. As shown in Figures 5 and 6, exemplary results indicate that aeration of the catholyte and precipitate results in CO2 mineralization as both solid and aqueous species, even at CO2 concentrations as low as 400 ppm (atmospheric).

[0089] definition Unless otherwise defined herein, scientific and technical terms used in this application shall have the meanings commonly understood by those of ordinary skill in the art. Generally, the nomenclature used in connection with and techniques of chemistry, chemical engineering, electrical engineering, and civil engineering described herein are those well known and commonly used in the art.

[0090] The methods and techniques of the present disclosure are generally carried out according to conventional methods well known in the art and as described in various general and more specific references cited and discussed throughout the specification, unless otherwise indicated.

[0091] Chemical terms used herein, unless otherwise defined herein, are used in accordance with conventional usage in the art, as exemplified in "The McGraw-Hill Dictionary of Chemical Terms," ​​Parker S., Ed., McGraw-Hill, San Francisco, CA (1985).

[0092] All publications, patents, and published patent applications mentioned in this application are specifically incorporated herein by reference. In case of conflict, the present specification, including its specific definitions, will control.

[0093] As used herein, the term "optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes cases where the event or circumstance occurs and cases where it does not occur. For example, "optionally substituted alkyl" refers to an alkyl that can be substituted, just as when the alkyl is unsubstituted.

[0094] As used herein, the terms "olivine" and "olivine rock" may refer to at least one of olivines containing Mg, Fe, and SiO4, as well as any of the various members of the "olivine family," including olivine, tefloid, monticellite, larnite, and kirschsteinite. The above olivine species may further contain other elements, such as Mg, Fe, Mn, Al, Ti, Ca, Cr, Ni, Co, and the like. Olivine may be found in mafic and ultramafic igneous rocks.

[0095] As used herein, the terms "deacidifying," "deacidify," and "deacidification" refer to a process that results in an increase in the pH of an aqueous solution.

[0096] As used herein, "deoxidizing composition" refers to a composition that deoxidizes a substrate. Deoxidizing compositions include alkaline rocks and minerals containing carbonates, hydroxides, oxides, and / or silicates. As a non-limiting example, olivine rock may be used as a deoxidizing composition in certain embodiments to deoxidize solutions having a low pH.

[0097] As used herein, "free chlorine species" may refer to any compound that contains or can generate chlorine atoms having an oxidation state of 0 or greater. As non-limiting examples, free chlorine species of the present disclosure include Cl, ClO, - , and HClO.

[0098] As used herein, the terms "dechlorinate" and "dechlorination" refer to a process that results in the removal of Cl-containing compounds or ions from a substrate, such as an aqueous solution. In a preferred embodiment, by way of non-limiting example, dechlorination involves the removal of free chlorine species (e.g., Cl, ClO) using a dechlorination composition. - , HClO, etc.) - ) including chemical conversion to

[0099] As used herein, the term "dechlorinating composition" refers to a composition that promotes the chemical conversion of free chlorine species to chlorides.

[0100] As used herein, the term "deacidifying and dechlorinating composition" refers to a composition that advantageously deacidifies (e.g., induces an increase in the pH of) and dechlorinates (e.g., promotes the chemical conversion of free chlorine species to chlorides) aqueous solutions.

[0101] As used herein, the term "reducing species" refers to a chemical species that can interact with another chemical species and transfer at least one valence electron to the chemical species, thereby reducing the chemical species. Reducing species can include, but are not limited to, low-valent metal species.

[0102] As used herein, the term "low-valent metal species" refers to a chemical species that exists in a formal oxidation state that is less (i.e., lower) than at least one of the most common naturally occurring non-zero oxidation states. As a non-limiting example, low-valent metal species described herein include Fe 0 , Fe 2+ , Mn 0 , Mn 3+ , Mn 4+ , Ni 0 , Ni + , and Ni 3+ may include:

[0103] As used herein, the term "alkalinizing" refers to the process of increasing the pH of a given solution, e.g., the process of alkalizing a first solution to prepare an alkaline solution having a higher pH.

[0104] As used herein, the terms "acidifying" or "acidification" refer to the process of decreasing the pH of a given solution. A given solution may be at any starting pH before undergoing acidification; for example, a solution may already have a pH of less than 7 before the step of acidifying the solution is performed.

[0105] As used herein, the term "ionic communication" refers to the ability of ions to flow freely between two objects or between regions of an object, e.g., between the cathode and anode chambers of an electrochemical cell, according to a local chemical gradient. Non-limiting examples of such gradients include the flow of ions from an area of ​​higher potential to a lower potential, from a high ion concentration to a low ion concentration, and from a high chemical potential to a low chemical potential. In certain embodiments, two objects or regions may be physically separated (e.g., not in fluid communication) by a semi-permeable barrier but still be in ionic communication, e.g., by ion diffusion or transport through the barrier.

[0106] The term "homogeneous," as used herein to describe a surface, refers to a substantially flat or featureless surface, e.g., a surface having a low average areal roughness (Sa). For example, a homogeneous surface of the present disclosure may have an average areal roughness (Sa) of about 1.2 μm.

[0107] The term "particle," when used herein to describe a surface, refers to a surface having particles (e.g., spheres) dispersed thereon and / or adhered thereto, such that the surface comprises the particles. For example, certain particle surfaces of the present disclosure consist essentially of MnOx spheres. The particle surfaces of the present disclosure will be rougher (e.g., have a higher average areal roughness, Sa) than the homogeneous surfaces of the present disclosure.

[0108] As used herein, the terms "average areal roughness" and "Sa" refer to a three-dimensional roughness measurement that represents the average roughness across a measurement area. The value of Sa is the arithmetic mean of the distance of each of a set of points in a sample measurement (e.g., points on an anode surface) from a "mean plane" that represents the average plane of all points in the measurement. A higher Sa value indicates that the surface is "rougher" or has a greater average absolute distance from the mean plane. Conversely, a lower Sa value indicates that the surface is "less rough" or flatter. [Example]

[0109] The invention will now be generally described, but will be more readily understood by reference to the following examples, which are included solely for the purpose of illustrating certain aspects and embodiments of the invention and are not intended to be limiting thereof.

[0110] Example 1: Exemplary Deoxidizers [Table S1-1] [Table S1-2]

[0111] Example 2: Results of an Exemplary CO2 Removal System An exemplary two-chamber flow-through reactor (e.g., FIG. 4) was used with a porous diaphragm used to separate the anolyte and catholyte. Seawater was used to flow through the anolyte and catholyte chambers. A 316 stainless steel mesh was used as the cathode, while a MnOx-coated titanium anode of the present disclosure was used as the anode. In the aforementioned setup, the flow rates of the catholyte and anolyte were identical and controlled by a peristaltic pump. By applying a voltage to the electrode pair, the catholyte pH was maintained above 10, and the anolyte pH was below 2 (FIG. 5).

[0112] Regarding anolyte treatment, the use of manganese oxide-coated anodes (Figure 8, inset) significantly reduced chlorine oxidation during the electrolysis process to approximately 99% (Figure 8). The remaining free chlorine species (less than 100 ppm) can be easily dechlorinated by the aforementioned approach or by using commercially available reagents (e.g., activated carbon, SO2, sulfite, etc.), ensuring that large-scale carbon removal processes do not generate oxidized chlorine species. In addition, Figure 9 shows exemplary results of neutralizing anolyte acidity using olivine rock (forsterite). More than 99% of the acidity (H+) was neutralized even at a low solids loading (50 g / L) under a 10-minute hydraulic retention time.

[0113] Example 3: Synthesis of an exemplary oxygen-selective anode Exemplary OER selective anodes (shown in Figures 10-16) were fabricated by depositing a mixture of Mn, Mo, and Sn oxides onto a titanium metal substrate coated with a layer of mixed metal oxide (MMO). The MMO interlayer consisted of a mixture of IrO2 and SnO2 (i.e., Ir-Sn MMO, see Figures 10 and 14) or a mixture of IrO2 and Ta2O5 (i.e., Ir-Ta MMO, see Figures 12 and 15). The Ir-Sn MMO- or Ir-Ta MMO-coated titanium substrate was then placed in an electrodeposition bath solution containing H2SO4, MnSO4, Na2MoO4, and SnCl4. A Pt-coated titanium mesh was also placed in the bath as the cathode, and a porous hydrophilic PVDF or porous ceramic separator / diaphragm was placed between the MMO-coated Ti (anode) and the Pt-coated Ti (cathode). The bath was then heated to 90°C and the MMO-coated Ti was anodically polarized at 600 A / m for 30 min. 2 A current density of 1000 kJ / cm was achieved. The electrodeposition procedure was repeated as necessary, with the bath solution replaced between each time. This procedure generally results in a MnO coating of approximately 0.1 μm to approximately 50 μm thick growing on top of the MMO coating (see Figures 11, 13, and 16-20). X-ray diffraction (XRD) characterization (Figure 20) indicates that the MnO coating is composed of ramsdellite (γ-MnO), while the Ir-Ta layer has a rutile structure. High-resolution SEM image characterization (Figure 17) indicates that the ramsdellite (γ-MnO) is in the form of microspheres with diameters ranging from 0.79 to 2.3 μm. As shown in Figure 18, the γ-MnO microspheres contribute to an approximately 1.5-fold increase in surface area compared to the geometric surface area. The γ-MnO spheres feature a nanostructured surface that increases the electrode-electrolyte contact area.

[0114] Example 4: Synthesis of an exemplary oxygen-selective anode An exemplary OER selective anode (shown in Figures 10-16) was fabricated by depositing Mn oxide onto a titanium metal substrate coated with a layer of mixed metal oxide (MMO). The MMO interlayer consisted of a mixture of IrO2, SnO2, and Ta2O5 (i.e., Ir-Ta MMO, see Figures 12 and 15). The Ir-Ta-Sn MMO-coated titanium substrate was then placed in an electrodeposition bath solution containing H2SO4 and MnSO4. A Pt-coated titanium mesh was also placed in the bath as a cathode, and a porous hydrophilic PVDF or porous ceramic separator / diaphragm was placed between the MMO-coated Ti (anode) and the Pt-coated Ti (cathode). The bath was then heated to 90°C, and the MMO-coated Ti was anodically polarized at 600 A / m for 30 minutes. 2 A current density of 1000 μm was achieved. The electrodeposition procedure was repeated as necessary, with the bath solution replaced between each time. This procedure generally results in a MnO coating of approximately 0.1 μm to approximately 50 μm thick growing on top of the MMO coating (see Figures 11, 13, and 16-20). X-ray diffraction (XRD) characterization (Figure 20) indicates that the MnO coating is composed of ramsdellite (γ-MnO), while the Ir-Ta-Sn layer has a rutile structure. High-resolution SEM image characterization (Figure 17) indicates that the ramsdellite (γ-MnO) is in the form of microspheres with diameters ranging from 0.79 to 2.3 μm. As shown in Figure 18, the γ-MnO microspheres contribute to an approximately 1.5-fold increase in surface area compared to the geometric surface area. The γ-MnO spheres feature a nanostructured surface that increases the electrode-electrolyte contact area. When using a low H2SO4 concentration in the plating bath (e.g., 0.1 to approximately 1.9 M), nanostructured γ-MnO2 spheres dominate the surface, while a plating bath with a high H2SO4 concentration (approximately 2 M to approximately 6 M, up to approximately 18 M) promotes a flatter (homogeneous) MnOx coating surface (Figure 23A).

[0115] Example 5: ALT Testing of Exemplary Anodes with Various Morphologies ALT experiments were conducted to observe the effect of varying the H2SO4 content in the electroplating precursor on the composition and morphology of the MnOx coating. A series of selected H2SO4 concentrations, ranging from approximately 0.1 to approximately 18 M, were tested in the plating bath. The resulting ALT and predicted life values ​​were discretized into the following categories: ALT life: + (100 h - 300 h), ++ (300 h - 600 h), +++ (600 h - 900 h), and ++++ (900 h - 1200 h); predicted life: * (1000 h - 3000 h), ** (3000 h - 5000 h), *** (5000 h - 7000 h), and **** (7000 h - 9000 h). Exemplary results are provided in Table 4 for anodes with a substantially flat (homogeneous) surface prepared by plating with a higher H2SO4 concentration, and anodes with a fine-grained surface prepared by plating with a lower H2SO4 concentration. While lower H2SO4 concentrations result in a fine-grained MnOx coating morphology, higher H2SO4 plating bath concentrations promote a more homogeneous appearance (Figure 23A). Preliminary ALT experiments showed that the two coatings behaved very similarly up to approximately 200 hours (including the onset of Stages I, II, and III), but the anode with the fine-grained coating exhibited a slower degradation rate toward the end of Stage III. Given an (arbitrary) threshold of 5% ClER selectivity, ALT lifetimes were determined as + for cyclic and constant voltage conditions, respectively, resulting in predicted lifetimes in the * category. The combination of a homogeneous MnOx layer with Substrate 3 provided the best performance in accelerated lifetime tests.

[0116] The ALT (experimental) and predicted lifetimes of the tested electrodes are shown in Table S5. [Table S5]

[0117] Incorporation by Reference All publications and patents mentioned herein are incorporated by reference in their entirety as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. In case of conflict, the present application, including definitions herein, will control.

[0118] equivalent While specific embodiments of the subject disclosure have been discussed, the foregoing specification is illustrative and not restrictive. Many variations of the present disclosure will become apparent to those skilled in the art upon review of this specification and the following claims. The full scope of the disclosure should be determined by reference to the claims, along with their full scope of equivalents, and the specification, along with such variations.

Claims

1. an oxygen-selective anode, A substrate; a mixed metal oxide (MMO) layer disposed on the substrate; an outer layer disposed on the MMO layer; the substrate comprises a conductive or semiconductive material; the MMO layer comprises at least one element selected from elements of groups 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14; The oxygen-selective anode, wherein the outer layer comprises manganese and oxygen.

2. 10. The oxygen-selective anode of claim 1, wherein the substrate is electrically conductive.

3. 10. The oxygen-selective anode of claim 1, wherein the substrate is semiconductive.

4. The oxygen-selective anode of any one of claims 1 to 3, wherein the substrate comprises a metal.

5. 10. The oxygen-selective anode of any preceding claim, wherein the substrate is selected from metal oxides, metal silicates, metal carbonates, metal phosphides, metal sulfides, and metal selenides, or combinations thereof.

6. 10. The oxygen-selective anode of any preceding claim, wherein the substrate comprises an element selected from titanium, magnesium, and Pt.

7. 4. The oxygen-selective anode of claim 1 or 3, wherein the substrate is carbon-based.

8. 8. The oxygen-selective anode of claim 7, wherein the substrate is selected from graphite, graphene, carbon nanotubes, and glassy carbon.

9. 10. The oxygen-selective anode of any preceding claim, wherein the MMO layer comprises a first metal oxide comprising Pt, Pd, Rh, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Hf, W, Re, Os, Au, Ta, Ru, Ti, Y, Sr, Sn, La, Ce, or Ir.

10. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Pt.

11. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Pd.

12. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Rh.

13. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising V.

14. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Cr.

15. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Mn.

16. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Fe.

17. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Co.

18. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Ni.

19. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Cu.

20. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Zn.

21. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Zr.

22. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Nb.

23. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Mo.

24. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Hf.

25. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising W.

26. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Re.

27. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Os.

28. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Au.

29. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Ta.

30. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Ru.

31. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Ti.

32. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Y.

33. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Sr.

34. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Sn.

35. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising La.

36. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Ce.

37. 10. The oxygen-selective anode of claim 9, wherein the MMO layer comprises a first metal oxide comprising Ir.

38. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Pt, Pd, Rh, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Hf, W, Re, Os, Au, Ta, Ru, Ti, Y, Sr, Sn, La, Ce, or Ir.

39. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Pt.

40. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Pd.

41. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Rh.

42. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising V.

43. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Cr.

44. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Mn.

45. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Fe.

46. 38. The oxygen-selective anode of claim 9, wherein the MMO layer further comprises a second metal oxide comprising Co.

47. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Ni.

48. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Cu.

49. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Zn.

50. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Zr.

51. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Nb.

52. 38. The oxygen-selective anode of claim 9, wherein the MMO layer further comprises a second metal oxide comprising Mo.

53. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Hf.

54. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising W.

55. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Re.

56. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Os.

57. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Au.

58. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Ta.

59. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Ru.

60. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Ti.

61. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Y.

62. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Sr.

63. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Sn.

64. 38. The oxygen-selective anode of claim 9, wherein the MMO layer further comprises a second metal oxide comprising La.

65. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Ce.

66. 38. The oxygen-selective anode of any one of claims 9 to 37, wherein the MMO layer further comprises a second metal oxide comprising Ir.

67. The oxygen-selective anode of any one of claims 1 to 8, wherein the MMO layer comprises Ta, Ir, and O.

68. 39. The oxygen-selective anode of claim 38, wherein the first metal oxide comprises Ta and the second metal oxide comprises Ir.

69. The oxygen-selective anode of any one of claims 1 to 8, wherein the MMO layer comprises Sn, Ir, and O.

70. 39. The oxygen-selective anode of claim 38, wherein the first metal oxide comprises Sn and the second metal oxide comprises Ir.

71. The oxygen-selective anode of any one of claims 1 to 8, wherein the MMO layer comprises Ta, Ru, and O.

72. 39. The oxygen-selective anode of claim 38, wherein the first metal oxide comprises Ta and the second metal oxide comprises Ru.

73. The oxygen-selective anode of any one of claims 1 to 8, wherein the MMO layer comprises Sn, Ru, and O.

74. 39. The oxygen-selective anode of claim 38, wherein the first metal oxide comprises Sn and the second metal oxide comprises Ru.

75. The oxygen-selective anode of any one of claims 1 to 8, wherein the MMO layer comprises Co, Mn, and O.

76. 39. The oxygen-selective anode of claim 38, wherein the first metal oxide is Co and the second metal oxide is Mn.

77. 77. The oxygen-selective anode of any one of claims 1 to 76, further comprising a dopant selected from Ti, Mo, Ru, W, Sr, Sn, Mn, Ta, Co, and Nb, or combinations thereof.

78. 78. The oxygen-selective anode of any one of claims 9 to 77, wherein the MMO layer comprises a third metal oxide comprising Pt, Pd, Rh, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Hf, W, Re, Os, Au, Ta, Ru, Ti, Y, Sr, Sn, La, Ce, or Ir.

79. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Pt.

80. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Pd.

81. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Rh.

82. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising V.

83. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Cr.

84. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Mn.

85. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Fe.

86. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Co.

87. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Ni.

88. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Cu.

89. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Zn.

90. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Zr.

91. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Nb.

92. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Mo.

93. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Hf.

94. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising W.

95. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Re.

96. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Os.

97. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Au.

98. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Ta.

99. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Ru.

100. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Ti.

101. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Y.

102. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Sr.

103. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Sn.

104. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising La.

105. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Ce.

106. 79. The oxygen-selective anode of any one of claims 9 to 78, wherein the MMO layer further comprises a third metal oxide comprising Ir.

107. The oxygen-selective anode of any one of claims 1 to 8, wherein the MMO layer comprises Co, Mo, Sn, and O.

108. 79. The oxygen-selective anode of claim 78, wherein the first metal oxide comprises Co, the second metal oxide comprises Mo, and the third metal oxide comprises Sn.

109. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 10 mol% of the first metal oxide.

110. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 20 mol% of the first metal oxide.

111. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 30 mol% of the first metal oxide.

112. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 40 mol% of the first metal oxide.

113. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 50 mol% of the first metal oxide.

114. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 60 mol% of the first metal oxide.

115. 115. The oxygen-selective anode of any one of claims 38 to 114, wherein the MMO layer comprises about 0.5 mol% of the second metal oxide.

116. 115. The oxygen-selective anode of any one of claims 38 to 114, wherein the MMO layer comprises about 1.0 mol% of the second metal oxide.

117. 115. The oxygen-selective anode of any one of claims 38 to 114, wherein the MMO layer comprises about 1.5 mol% of the second metal oxide.

118. 115. The oxygen-selective anode of any one of claims 38 to 114, wherein the MMO layer comprises about 2.0 mol% of the second metal oxide.

119. 115. The oxygen-selective anode of any one of claims 38 to 114, wherein the MMO layer comprises about 2.5 mol% of the second metal oxide.

120. 115. The oxygen-selective anode of any one of claims 38 to 114, wherein the MMO layer comprises about 3.0 mol% of the second metal oxide.

121. 121. The oxygen-selective anode of any one of claims 78 to 120, wherein the MMO layer comprises about 0.001 mol% of the third metal oxide.

122. 121. The oxygen-selective anode of any one of claims 78 to 120, wherein the MMO layer comprises about 0.002 mol% of the third metal oxide.

123. 121. The oxygen-selective anode of any one of claims 78 to 120, wherein the MMO layer comprises about 0.003 mol% of the third metal oxide.

124. 121. The oxygen-selective anode of any one of claims 78 to 120, wherein the MMO layer comprises about 0.004 mol% of the third metal oxide.

125. 121. The oxygen-selective anode of any one of claims 78 to 120, wherein the MMO layer comprises about 0.005 mol% of the third metal oxide.

126. 121. The oxygen-selective anode of any one of claims 78 to 120, wherein the MMO layer comprises about 0.006 mol% of the third metal oxide.

127. 121. The oxygen-selective anode of any one of claims 78 to 120, wherein the MMO layer comprises about 0.007 mol% of the third metal oxide.

128. 121. The oxygen-selective anode of any one of claims 78 to 120, wherein the MMO layer comprises about 0.008 mol% of the third metal oxide.

129. 129. The oxygen-selective anode of any one of claims 9 to 128, wherein the MMO layer comprises about 10 mol % oxygen.

130. 129. The oxygen-selective anode of any one of claims 9 to 128, wherein the MMO layer comprises about 20 mol% oxygen.

131. 129. The oxygen-selective anode of any one of claims 9 to 128, wherein the MMO layer comprises about 30 mol% oxygen.

132. 129. The oxygen-selective anode of any one of claims 9 to 128, wherein the MMO layer comprises about 40 mol% oxygen.

133. 129. The oxygen-selective anode of any one of claims 9 to 128, wherein the MMO layer comprises about 50 mol % oxygen.

134. 129. The oxygen-selective anode of any one of claims 9 to 128, wherein the MMO layer comprises about 60 mol% oxygen.

135. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 10% by weight of the first metal oxide.

136. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 20% by weight of the first metal oxide.

137. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 30% by weight of the first metal oxide.

138. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 40% by weight of the first metal oxide.

139. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 50% by weight of the first metal oxide.

140. 109. The oxygen-selective anode of any one of claims 9 to 108, wherein the MMO layer comprises about 60% by weight of the first metal oxide.

141. 141. The oxygen-selective anode of any one of claims 38 to 140, wherein the MMO layer comprises about 0.5 wt% of the second metal oxide.

142. 141. The oxygen-selective anode of any one of claims 38 to 140, wherein the MMO layer comprises about 1.0 wt% of the second metal oxide.

143. 141. The oxygen-selective anode of any one of claims 38 to 140, wherein the MMO layer comprises about 1.5 wt% of the second metal oxide.

144. 141. The oxygen-selective anode of any one of claims 38 to 140, wherein the MMO layer comprises about 2.0 wt% of the second metal oxide.

145. 141. The oxygen-selective anode of any one of claims 38 to 140, wherein the MMO layer comprises about 2.5 wt% of the second metal oxide.

146. 141. The oxygen-selective anode of any one of claims 38 to 140, wherein the MMO layer comprises about 3.0 wt% of the second metal oxide.

147. 141. The oxygen-selective anode of any one of claims 78 to 140, wherein the MMO layer comprises about 0.001 wt% of the third metal oxide.

148. 141. The oxygen-selective anode of any one of claims 78 to 140, wherein the MMO layer comprises about 0.002 wt% of the third metal oxide.

149. 141. The oxygen-selective anode of any one of claims 78 to 140, wherein the MMO layer comprises about 0.003 wt% of the third metal oxide.

150. 141. The oxygen-selective anode of any one of claims 78 to 140, wherein the MMO layer comprises about 0.004 wt% of the third metal oxide.

151. 141. The oxygen-selective anode of any one of claims 78 to 140, wherein the MMO layer comprises about 0.005 wt% of the third metal oxide.

152. 141. The oxygen-selective anode of any one of claims 78 to 140, wherein the MMO layer comprises about 0.006 wt% of the third metal oxide.

153. 141. The oxygen-selective anode of any one of claims 78 to 140, wherein the MMO layer comprises about 0.007 wt% of the third metal oxide.

154. 141. The oxygen-selective anode of any one of claims 78 to 140, wherein the MMO layer comprises about 0.008 wt% of the third metal oxide.

155. 155. The oxygen-selective anode of any one of claims 1 to 154, wherein the MMO layer comprises about 10% oxygen by weight.

156. 156. The oxygen-selective anode of any one of claims 1 to 155, wherein the MMO layer comprises about 20% oxygen by weight.

157. 156. The oxygen-selective anode of any one of paragraphs 1 to 155, wherein the MMO layer comprises about 30% oxygen by weight.

158. 156. The oxygen-selective anode of any one of claims 1 to 155, wherein the MMO layer comprises about 40% oxygen by weight.

159. 156. The oxygen-selective anode of any one of claims 1 to 155, wherein the MMO layer comprises about 50% oxygen by weight.

160. 156. The oxygen-selective anode of any one of claims 1 to 155, wherein the MMO layer comprises about 60% oxygen by weight.

161. 161. The oxygen-selective anode of any one of claims 1 to 160, wherein the MMO layer comprises between about 5 atomic percent (at. %) Ir and about 65 at. % Ir.

162. 162. The oxygen-selective anode of any one of claims 1 to 161, wherein the MMO layer comprises between about 15 at. % Ir and about 30 at. % Ir.

163. 162. The oxygen-selective anode of any one of claims 1 to 161, wherein the MMO layer comprises about 5.77 at. % Ir.

164. 162. The oxygen-selective anode of any one of claims 1 to 161, wherein the MMO layer comprises about 7.03 at. % Ir.

165. 162. The oxygen-selective anode of any one of claims 1 to 161, wherein the MMO layer comprises from about 17 at. % Ir to about 65 at. % Ir.

166. 166. The oxygen-selective anode of any one of claims 1 to 161 and 165, wherein the MMO layer comprises about 62.4 at. % Ir.

167. 167. The oxygen-selective anode of any one of claims 1 to 166, wherein the outer layer has a thickness of from about 0.1 μm to about 500 μm.

168. 168. The oxygen-selective anode of any one of claims 1 to 167, wherein the outer layer has a thickness of about 5 μm.

169. 168. The oxygen-selective anode of any one of claims 1 to 167, wherein the outer layer has a thickness of about 10 μm.

170. 168. The oxygen-selective anode of any one of claims 1 to 167, wherein the outer layer has a thickness of about 20 μm.

171. 168. The oxygen-selective anode of any one of claims 1 to 167, wherein the outer layer has a thickness of about 30 μm.

172. 168. The oxygen-selective anode of any one of claims 1 to 167, wherein the outer layer has a thickness of about 40 μm.

173. 168. The oxygen-selective anode of any one of claims 1 to 167, wherein the outer layer has a thickness of about 50 μm.

174. 174. The oxygen-selective anode of any one of claims 1 to 173, wherein the MMO layer has a thickness of from about 0.1 μm to about 500 μm.

175. 174. The oxygen-selective anode of any one of claims 1 to 173, wherein the MMO layer has a thickness of from about 0.1 μm to about 100 μm.

176. 174. The oxygen-selective anode of any one of claims 1 to 173, wherein the MMO layer has a thickness of from about 0.1 μm to about 50 μm.

177. 174. The oxygen-selective anode of any one of claims 1 to 173, wherein the MMO layer has a thickness of from about 0.1 μm to about 20 μm.

178. 174. The oxygen-selective anode of any one of claims 1 to 173, wherein the MMO layer has a thickness of from about 5 μm to about 20 μm.

179. 174. The oxygen-selective anode of any one of claims 1 to 173, wherein the MMO layer has a thickness of from about 10 μm to about 20 μm.

180. 174. The oxygen-selective anode of any one of claims 1 to 173, wherein the MMO layer has a thickness of from about 10 μm to about 15 μm.

181. 174. The oxygen-selective anode of any one of claims 1 to 173, wherein the MMO layer has a thickness of from about 5 μm to about 15 μm.

182. 10. The oxygen-selective anode of any preceding claim, wherein the outer layer comprises Mn.

183. 10. The oxygen-selective anode of any preceding claim, wherein the outer layer comprises Mo.

184. 10. The oxygen-selective anode of any preceding claim, wherein the outer layer comprises Ta.

185. 10. The oxygen-selective anode of claim 1, wherein the outer layer comprises La.

186. 10. The oxygen-selective anode of any preceding claim, wherein the outer layer comprises Ce.

187. 10. The oxygen-selective anode of any preceding claim, wherein the outer layer comprises Sn.

188. 10. The oxygen-selective anode of claim 1, wherein the outer layer further comprises an outer layer dopant.

189. 10. The oxygen-selective anode of any preceding claim, wherein the outer layer further comprises two or more outer layer dopants.

190. 190. The oxygen-selective anode of claim 188 or 189, wherein each of the outer layer dopants is a transition metal.

191. 191. The oxygen-selective anode of any one of claims 188 to 190, wherein the outer layer dopant is selected from transition metal oxides, transition metal hydroxides, and transition metal oxyhydroxides.

192. 10. The oxygen-selective anode of any preceding claim, wherein the outer layer is coated on the surface of the MMO layer.

193. 10. The oxygen-selective anode of any preceding claim, wherein the outer layer is coated intermixed (e.g., mixed) with the MMO layer.

194. 10. The oxygen-selective anode according to any preceding claim, wherein the MMO layer comprises one or more additional MMO layers.

195. 195. The oxygen-selective anode of claim 194, wherein the MMO layer comprises one additional MMO layer.

196. 195. The oxygen-selective anode of claim 194, wherein the MMO layer comprises two additional MMO layers.

197. 195. The oxygen-selective anode of claim 194, wherein the MMO layer comprises three additional MMO layers.

198. 195. The oxygen-selective anode of claim 194, wherein the MMO layer comprises four additional MMO layers.

199. 195. The oxygen-selective anode of claim 194, wherein the MMO layer comprises five additional MMO layers.

200. 200. The oxygen-selective anode of any one of claims 194 to 199, wherein the additional MMO layer(s) comprise an element selected from groups 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14.

201. 201. The oxygen-selective anode of any one of claims 194 to 200, wherein the additional MMO layer(s) comprise a metal oxide comprising Ta, Ru, Ti, Y, Sr, Sn, La, Ce, or Ir.

202. 202. The oxygen-selective anode of any one of claims 194 to 201, wherein the additional MMO layer(s) have a composition according to any one of claims 9 to 162.

203. 10. The oxygen-selective anode of any preceding claim, wherein the substrate is in contact with the MMO layer at a substrate-MMO junction and the MMO layer is in contact with the outer layer at an MMO-outer layer junction.

204. 204. The oxygen-selective anode of claim 203, wherein the substrate-MMO junction is substantially planar.

205. 204. The oxygen-selective anode of claim 203, wherein the substrate-MMO bond is substantially rough.

206. 204. The oxygen-selective anode of claim 203, wherein the substrate-MMO junction is a bulk heterojunction.

207. 204. The oxygen-selective anode of claim 203, wherein the MMO-outer layer junction is substantially flat.

208. 204. The oxygen-selective anode of claim 203, wherein the MMO-outer layer bond is substantially rough.

209. 204. The oxygen-selective anode of claim 203, wherein the MMO-outer layer junction is a bulk heterojunction.

210. 10. The oxygen-selective anode of any preceding claim, wherein the outer layer has a surface morphology comprising spheres.

211. 211. The oxygen-selective anode of claim 210, wherein the spheres have diameters in the nanometer range.

212. 211. The oxygen-selective anode of claim 210, wherein the spheres have diameters in the micrometer range.

213. 211. The oxygen-selective anode of claim 210, wherein the spheres have a diameter of 0.01 μm to 10 μm.

214. 214. The oxygen-selective anode of any one of claims 210-213, wherein the spheres have a composition according to any one of claims 9-162 (eg, the spheres comprise a mixed metal oxide).

215. The spheres are made of ramsdellite (γ-MnO ２ 215. The oxygen-selective anode of any one of claims 210 to 214, comprising:

216. 216. The oxygen-selective anode of any one of claims 210 to 215, wherein the MMO layer has a surface morphology substantially as shown in Figure 14.

217. 216. The oxygen-selective anode of any one of claims 210 to 215, wherein the MMO layer has a surface morphology substantially as shown in Figure 15.

218. 216. The oxygen-selective anode of any one of claims 210 to 215, wherein the outer layer has a surface morphology substantially as shown in Figure 16.

219. 216. The oxygen-selective anode of any one of claims 210 to 215, wherein the spheres have the morphology shown in Figure 17.

220. 216. The oxygen-selective anode of any one of claims 210 to 215, wherein the spheres have the morphology shown in Figure 17.

221. 221. The oxygen-selective anode of any one of claims 210 to 220, wherein the surface morphology of the outer layer increases the surface area of ​​the outer layer by between 1 and 100 times.

222. 222. The oxygen-selective anode of any one of claims 1 to 221, wherein the outer layer has a surface with an average areal roughness (Sa) of from about 1 μm to about 10 μm.

223. 223. The oxygen-selective anode of any one of claims 1 to 222, wherein the outer layer has a surface with an average areal roughness (Sa) of about 1.27 μm, about 2 μm, about 4 μm, or about 10 μm.

224. The oxygen-selective anode of any one of claims 1 to 203, wherein the outer layer has a surface that is substantially flat (eg, uniform).

225. 225. The oxygen-selective anode of any one of claims 1 to 203 and 224, wherein the outer layer has a surface with an average areal roughness (Sa) of from about 0 μm to about 1 μm.

226. 226. The oxygen-selective anode of any one of claims 1-203, 224, and 225, wherein the outer layer has a surface with an average areal roughness (Sa) of about 0.1 μm, about 0.2 μm, about 0.5 μm, or about 1 μm.

227. The oxygen-selective anode of any one of claims 1 to 226, wherein the substrate is solid (eg, non-porous).

228. The oxygen-selective anode of any one of claims 1 to 226, wherein the substrate is porous.

229. The oxygen-selective anode of any one of claims 1 to 228, wherein the substrate is a plate, mesh, felt, foam, fiber, or particle, or a combination thereof.

230. 230. The oxygen-selective anode of any one of claims 1 to 229, wherein the substrate is a plate, mesh, felt, foam, fiber, or particle, or a combination thereof.

231. 230. A method for acidifying an aqueous solution, comprising contacting the aqueous solution with an oxygen-selective anode according to any one of claims 1 to 230, thereby producing H ＋ and / or H ３ O ＋ ions and O ２ forming a

232. CO ２ 1. A method for isolating a (a) in a first cathode chamber; (i) alkalizing the first solution by contacting the first solution with a cathode disposed within the first cathode chamber, thereby forming an alkaline solution and H ２ wherein the first solution comprises water and divalent alkaline earth ions; (ii) dissolving the alkaline solution in CO ２ a source of ionic compounds, thereby forming a carbonate solution containing a mixture of ionic compounds, wherein the ionic compounds are CO ３ ２－ or HCO ３ － performing an alkaline process comprising: (b) in the first anode chamber; (i) acidifying the second solution containing chloride ions by contacting the second solution with an oxygen-selective anode according to any one of claims 1 to 230 disposed in the first anode chamber, thereby forming an acidic solution; and (ii) deacidifying the acidic solution by contacting the acidic solution with a deacidifying agent, thereby forming a deacidified solution; (c) dechlorinating the acidic or deacidified solution by contacting the acidic or deacidified solution with a dechlorinating agent; the first anode chamber and the second anode chamber are in ionic communication; The above method, wherein the acidic process and the alkaline process are carried out simultaneously or sequentially.

233. 233. The method of claim 232, wherein the alkaline process and the acidic process are carried out simultaneously.

234. 234. The method of claim 232 or 233, wherein the deoxidizing agent is selected from periclase, lime, lime kiln dust, forsterite, olivine, larnite, serpentinite, basalt, stainless steel slag, peridotite, lizardite (serpentine), ladle slag, blast furnace slag, diopside, air-cooled blast furnace slag, wollastonite, basic oxygen furnace slag, brownmillerite, mixed electric arc furnace slag, cement kiln dust, talc, electric arc furnace slag, Class C fly ash, recovered Class C fly ash, anorthite, trona-enriched fly ash, bytunite, gabbro, anorthosite, albite, and Class F fly ash.

235. 235. The method of any one of claims 232 to 234, wherein the dechlorinating agent is selected from hydrogen sulfide, sulfur dioxide, sulfite, copper slag, faiite, ferrosilite, magnetite, antigotite, periclase, lime, lime kiln dust, forsterite, olivine, larnite, serpentinite, basalt, stainless steel slag, peridotite, lizardite (serpentine), ladle slag, blast furnace slag, diopside, cooled blast furnace slag, wollastonite, basic oxygen furnace slag, brownmillerite, mixed electric arc furnace slag, cement kiln dust, talc, electric arc furnace slag, Class C fly ash, recovered Class C fly ash, anorthite, trona-enriched fly ash, bytunite, gabbro, anorthosite, albite, and Class F fly ash.

236. 236. The method of any one of claims 232 to 235, wherein the scavenger is the dechlorinating agent.

237. The CO ２ The source is from about 400 ppm to about 100% CO ２ , preferably about 400 ppm.

238. The CO ２ The method of any one of claims 232 to 237, wherein the source is ambient air.

239. The CO ２ The sources include gas effluents from industrial processes (e.g., oil and gas production, power generation, cement production, or steel production), and concentrated CO from direct air capture processes. ２ (e.g., near-pure or pure CO ２ ) or higher CO than ambient air. ２ The method of any one of claims 232 to 238, having a concentration.

240. 240. The method of any one of claims 232 to 239, wherein the first solution is selected from seawater, desalinated brine, industrial brine, and natural brine.

241. 241. The method of any one of claims 232 to 240, wherein the second solution is selected from seawater, desalinated brine, industrial brine, and natural brine.

242. 242. The method of any one of claims 232 to 241, wherein the first solution and the second solution are derived from the same source solution.

243. 243. The method of any one of claims 232 to 242, wherein the alkaline process and the acidic process occur in a space separated by a semi-permeable barrier having a plurality of pores.

244. 244. The method of claim 243, wherein the semi-permeable barrier is a semi-permeable membrane (e.g., an ion exchange material (e.g., Nafion), a hydrophilic ceramic membrane or plate (e.g., aluminum oxide, zirconium oxide, silicon dioxide, asbestos, hydrous aluminum phyllosilicate, clay, or any combination thereof), a polymer (e.g., cellulose, polyvinyl chloride, organic rubber, polyolefin, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, epoxy resin, silicone, or any combination thereof), or a ceramic-polymer composite).

245. 245. The method of claim 244, wherein the semi-permeable membrane is selected from an ion exchange membrane, a hydrophilic ceramic membrane, an organic polymer membrane, or a ceramic-polymer composite membrane.

246. 245. The method of claim 244, wherein the semi-permeable membrane is a ceramic membrane.

247. 247. The method of claim 246, wherein the ceramic film comprises at least one of aluminum oxide, zirconium oxide, silicon dioxide, asbestos, hydrous aluminum phyllosilicate, and clay.

248. 245. The method of claim 244, wherein the semi-permeable membrane is an organic polymer membrane.

249. 249. The method of claim 248, wherein the organic polymer membrane comprises at least one of perfluorosulfonic acid, Nafion, cellulose, polyvinyl chloride, organic rubber, polyolefin, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, epoxy resin, and silicone.

250. The organic polymer film is at least one of aluminum oxide, zirconium oxide, silicon dioxide, asbestos, hydrous aluminum phyllosilicate, and clay; and at least one of perfluorosulfonic acid, Nafion™, cellulose, polyvinyl chloride, organic rubber, polyolefin, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, epoxy resin, and silicone.

251. 251. The method of any one of claims 244 to 250, wherein the semi-permeable barrier has been treated to enhance surface hydrophilicity.

252. 252. The method of any one of claims 243 to 251, wherein the plurality of pores have a median pore diameter of from about 0.1 nm to about 500 nm.

253. 253. The method of any one of claims 246 to 252, wherein the semi-permeable barrier has a thickness of from about 50 μm to about 5 mm.

254. 254. The method of any one of claims 232 to 253, wherein the alkaline solution has a pH of from about 7 to about 14.

255. 255. The method of claim 254, wherein the alkaline solution has a pH of about 10 to about 11.

256. 255. The method of claim 254, wherein the alkaline solution has a pH of about 10.

5.

257. 257. The method of any one of claims 232 to 256, wherein the acidic solution has a pH of from about 0.1 to about 7.

258. 258. The method of claim 257, wherein the acidic solution has a pH of about 0.5 to 1.

5.

259. 259. The method of claim 258, wherein the acidic solution has a pH of about 1.

260. 1. An electrochemical cell comprising: (a) cathode, Cathode gas outlet, a first solution inlet; and an alkaline solution outlet; a cathode chamber, the cathode being disposed within the cathode chamber and coupled to a power source; (b) The anode of any one of claims 1 to 230. Anode gas outlet, a second solution inlet; and an acid solution outlet; the anode chamber, the anode disposed within the anode chamber and coupled to a power source.

261. The deoxidation chamber further comprises: Acid solution inlet, deacidification solution outlet, a deoxidizer chamber including a deoxidizer; 261. The system of claim 260, wherein the deoxidizer is disposed within the deoxidizer chamber, and the acid solution inlet of the deoxidizer chamber is connected to the acid solution outlet.

262. chlorinated solution inlet, dechlorination solution outlet, a dechlorination chamber containing a dechlorinating agent; 262. The system of claim 260 or 261, wherein the dechlorinating agent is disposed within the dechlorinating chamber and the chlorinating solution inlet is connected to the deacidifying solution outlet or the acidifying solution outlet.

263. 263. The system of any one of claims 263 to 262, wherein the alkaline process chamber and the acidic process chamber are separated by a separator.

264. 264. The system of claim 263, wherein the separator is a semi-permeable barrier having a plurality of pores, such as a semi-permeable membrane (e.g., an ion exchange material (e.g., Nafion, perfluorosulfonic acid (PFSA)), a hydrophilic ceramic membrane or plate (e.g., aluminum oxide, zirconium oxide, silicon dioxide, asbestos, hydrous aluminum phyllosilicate, clay, or any combination thereof), a polymer (e.g., cellulose, polyvinyl chloride, organic rubber, polyolefin, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, epoxy resin, silicone, or any combination thereof), or a ceramic-polymer composite).

265. 265. The system of claim 264, wherein the semi-permeable barrier is selected from an ion exchange membrane, a hydrophilic ceramic membrane, an organic polymer membrane, or a ceramic-polymer composite membrane.

266. The system of claim 265, wherein the semi-permeable barrier is a ceramic membrane.

267. 267. The system of claim 266, wherein the ceramic film comprises at least one of aluminum oxide, zirconium oxide, silicon dioxide, asbestos, hydrous aluminum phyllosilicate, and clay.

268. The system of claim 265, wherein the semi-permeable barrier is an organic polymer membrane.

269. The system of claim 268, wherein the organic polymer membrane comprises at least one of perfluorosulfonic acid, Nafion, cellulose, polyvinyl chloride, organic rubber, polyolefin, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, epoxy resin, and silicone.

270. The organic polymer film is at least one of aluminum oxide, zirconium oxide, silicon dioxide, asbestos, hydrous aluminum phyllosilicate, and clay; The system of claim 269, comprising at least one of perfluorosulfonic acid, Nafion™, cellulose, polyvinyl chloride, organic rubber, polyolefin, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, epoxy resin, and silicone.

271. 271. The system of any one of claims 260 to 270, wherein the semi-permeable barrier is treated to enhance surface hydrophilicity.

272. 272. The system of any one of claims 260 to 271, wherein the plurality of pores have a median pore diameter of about 1 nm to about 500 nm.

273. 273. The method of any one of claims 260 to 272, wherein the semi-permeable barrier has a thickness of from about 50 μm to about 5 mm.

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