Improving H+ conductivity in fuel cell electrolyzers

Abstract

The doped silica layer on the substrate includes a substrate and a doped silica layer having a thickness of 5 to 1000 nm and a dopant:silicon atomic ratio of 0.5:99.5 to 15:85. The dopant is preferably P. +5 The present invention includes an electrolytic cell containing a doped silica layer and a method for using the electrolytic cell to electrolyze water to produce hydrogen. The doped silica can be made by applying a silica layer by atomic layer deposition (ALD) and treating the silica layer with phosphorus gas in which phosphorus is in the +3 valence state.

Description

[Technical Field]

[0001] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 445,710, filed February 14, 2023.

[0002] Introduction H2 is a versatile, carbon-free energy carrier that promises to be an essential component of a clean energy future. Hydrogen fuel is of great importance today, currently accounting for approximately 1.5% of global energy use. Unfortunately, over 95% of H2 production comes from highly polluting oil and coal, or grey (methane) sources. Currently, the cost of green H2 from electrolysis is not competitive with fossil fuel sources. One way to reduce the cost is to increase the efficiency of polymer electrolyte membrane (PEM) electrolyzers by reducing the ohmic overpotential required for the cell. In this study, we investigated the membrane thickness (see Han, et al., Int. J. Hydrogen Energy, 40, 2015) and the H + A method to reduce the ohmic overpotential, which is determined in part by conductivity, is realized by replacing Nafion with an ultrathin proton-conducting oxide membrane (POM) deposited by ALD (atomic layer deposition). SiO2 ALD membranes, deposited by a proprietary catalytic process, have been synthesized and tested at various temperatures and thicknesses. + The conductivity and gas permeability (H2) of these SiO2 films were measured. + The transmittance was very low, so H + Dopants were investigated to increase the transmittance. -3 Using two new ALD precursors for doping, phosphoric acid, PO4 -3species were doped into SiO2 ALD films. For background information, see Henderick, L., et al., Appl. Phys. Rev. 9, 011310, 2022. X-ray photoelectron spectroscopy (XPS) showed that both precursors were incorporated into the growing SiO2 film, but H2O, O2, or O3 did not grow P2O3 or P2O5 monoliths. PO4 -3 The highest uptake rate was observed in PO4 -3 This was an ABC-type ALD sequence in which no additional oxidant was present in the precursor. x : The RI also decreased with the SiO2 film. -3 By adding H + The ABC-type ALD process was carried out in an acidic solution using a rotating disk electrode at room temperature, with a concentration of 2.1 × 10 -11 to 1.8 x 10 -10 cm 2 / s, an improvement of almost an order of magnitude. -3 When this is added, the H2 transmittance also increases to 5.1 x 10 -10 to 1.1 x 10 -10 cm 2 / s, an almost five-fold improvement. Importantly, the ALD POM membranes have the potential to be directly coated with high surface area porous transport or gas diffusion layers for integration into current PEM electrolyzer cells, potentially further improving efficiency. This work will enable the construction of complete electrolyzers employing new ultrathin ceramic membranes suitable for green H2 production.

[0003] Water electrolysis using renewable energy is an attractive approach to producing carbon-free, energy-dense hydrogen (H2) fuel, which promises to be a key enabler for industrial decarbonization. Globally, H2 usage is currently less than 1 million tons per year, but is projected to increase to 7 million tons per year by 2030. In the United States, McKinsey & Co. predicts that H2 revenues will reach $140 billion annually by 2030, supporting approximately 700,000 jobs. However, large-scale deployment of so-called green hydrogen produced by electrolysis is hindered by its relatively high levelized cost of hydrogen (LCOH, $3–8 / kg H2) compared to "blue H2" produced from CO2-emitting steam methane reforming (SMR), which costs $0.70–2.10 / kg H2. Currently, electricity costs are the most significant cost driver affecting LCOH from water electrolysis, creating a need for increased energy efficiency in electrolyzers. Fortunately, declining electricity prices from solar and wind power are helping to reduce the contribution of electricity costs to LCOH. However, the availability of low-cost electricity (<2¢ / kWh) from these variable renewable energy (VRE) generators is generally less than 45%. As a result, electrolyzers operating in regions with high VRE penetration are expected to malfunction due to low capacity factors, creating a second urgent need: reducing electrolyzer capital expenditures (CAPEX). While electrolyzer CAPEX is already declining thanks to economies of scale as the industry grows, more rapid CAPEX declines are needed through manufacturing advances and improved electrolyzer performance (i.e., higher current density and / or efficiency). While the exact performance and CAPEX targets for electrolyzers competing with SMRs will depend heavily on the price and availability of electricity, it is generally understood that for green hydrogen to reach levels comparable to blue H2 in the next 5–10 years, next-generation water electrolyzers capable of operating at much higher current densities and energy efficiencies will be required.

[0004] The electrolyzer industry is currently dominated by two technologies: alkaline electrolyzers and polymer electrolyte membrane (PEM) electrolyzers. Alkaline electrolyzers typically use approximately 30% by weight KOH (aqueous) as the electrolyte and operate at current densities of 0.1-0.4 A / cm2, with HHV stack efficiencies of 75-80%. PEM electrolyzers use a thin Nafion solid electrolyte membrane sandwiched between porous anode and cathode layers. The so-called "zero gap" geometry and active water management of PEM electrolyzers significantly reduces ionic resistance, allowing them to operate at 1-2 A / cm2 with efficiencies comparable to alkaline electrolyzers. 2 While more mature alkaline technologies are expected to remain important in the near term, the majority of R&D efforts are focused on current densities above 2 A / cm. 2 The ability to operate at low temperatures and the potential to operate at even higher current densities has led to a move to advance the PEM electrolyzer concept as a future technology. However, the gap between the electrodes in these "zero gap" PEM electrolyzers is not actually zero, and the Nafion membrane typically has a thickness of 125-250 um. While this may seem small, the ohmic resistance associated with ion transport across the membrane increases at high current densities (>2 A / cm). 2 ) is the primary loss mechanism. Researchers have attempted to reduce these losses by using thinner Nafion membranes, but success has been limited due to reduced manufacturing yields and mechanical failure associated with the swelling and creep phenomena inherent in many polymer membranes, such as Nafion, when in contact with water. Furthermore, it is well known that Nafion's proton conductivity decreases with membrane thickness, and gas permeability (H2 / O2) tends to increase. Even with advances in development, achieving membrane thicknesses much thinner than 50 microns appears difficult. While such efforts are worth pursuing, they are unlikely to result in significant changes in electrolyzer performance. Here, we consider membranes 2 to 4 orders of magnitude thinner than Nafion and membranes with a current density of 5 A / cm. 2 A class of membrane materials and a method for fabricating PEM electrolyzers capable of reducing ionic resistance to less than 0.2 V at these current densities are described.

[0005] To overcome the limitations of conventional polymer membranes such as Nafion, we use proton-conducting (SiOx) membranes, which are essentially silicon dioxide, although the stoichiometry can be slightly altered by dopants. While SiOx materials have long been known to conduct protons (H+), their conductivity at low temperatures is lower than that of Nafion, and therefore they have not been considered as a membrane material for conventional catalyst-coated membranes (CCMs). Fortunately, the reduced H+ conductivity is not an issue if the membrane can be made very thin while still providing a sufficient barrier to gas permeation. We have demonstrated that the use of ultrathin continuous oxide membranes, 2–4 orders of magnitude thinner than those used in Nafion for PEM electrolyzers, can reduce membrane resistance by >80%. Thin oxide membranes offer (i) higher density, which can suppress gas crossover (through pores), (ii) higher mechanical strength and deformation resistance compared to polymers, and (iii) thinner thicknesses are possible due to recent advances in rapid atomic layer deposition (ALD) fabrication techniques, which can deposit conformal oxide coatings on rough surfaces at nano- to micron-scale with high throughput. Oxide-based membranes are widely used in high-temperature solid oxide fuel cells and electrolyzers, but at low temperatures (up to 5 A / cm 2 There are no reports on oxide-based membranes for electrolyzers (<0.2 V at current densities of 1.7 A / cm). In Table 1, the operation of PEM and POM electrolyzers is shown. 2 "Standard" current density (i) and i = 4.25 A / cm 2Two operating modes at high current densities are considered. Next, using a one-dimensional (1D) electrolyzer model that assumes constant temperature and kinetic overpotential losses between the two types of electrolyzers, we calculated the increase in electrolyzer efficiency (ηE), and the results are shown in the last column of Table 1. As expected, reducing membrane resistance leads to efficiency gains in both cases, but the greatest benefit is achieved at high current densities, where membrane ohmic losses typically dominate polarization behavior. The high-current-density (i.e., high-capacity) operating mode is most attractive for a renewable energy future where low-cost electricity can be supplied from wind and / or solar (e.g., 2¢ / kWh based on the DOE Sunshot target for 2030), but is only available 30–40% of the time. These efficiency gains at high current densities reduce electrolyzer stack costs from the current approximately $400 / kW to approximately $70 / kW. This stack cost reduction is consistent with the DOE's Energy Earthshot initiative, which aims to achieve LCOH of $1 / kg H2 by 2031. Achieving $1 / kg H2 would be transformative in that H2 from water electrolysis would undercut H2 from SMR and become directly competitive with gasoline prices at the pump. [Table 1] Summary of the Invention

[0006] In one aspect, the present invention provides an electrolytic cell comprising an anode, a cathode, and a doped silica electrolyte layer, the anode and cathode being separated by 1 μm or less, the anode and cathode being separated by a doped silica electrolyte layer, the doped silica electrolyte layer having a thickness of 5 to 1000 nm, a dopant:silicon atomic ratio of 0.5:99.5 to 15:85, and an H+ permeability (cm 2 / s) ≥ 5 × 10 -11 The anode and cathode may be any anode or cathode known in the art, and are typically plate-shaped, with the anode typically having a catalyst such as Pt, and common materials include carbon paper.

[0007] The electrolytic cell may be further characterized by any one or combination of the following: the doped silica electrolyte layer has a thickness in the range of 5-500, 5-200, 5-100, 10-1000, 10-500, 10-200, or 10-100 nm; the doped silica electrolyte layer has a dopant:silicon atomic ratio of 1:99-15:85, or 1:99-10:90, or 1:99-5:95; and the doped silica electrolyte layer has a dopant:silicon atomic ratio of ≥ 1 x 10 -10 , or 5 × 10 -11 ~5×10 -10 range, or 5×10 -11 ~2×10 -10 cm 2 / s, and the dopant is P +5 is.

[0008] In another aspect, the present invention provides a doped silica layer on a substrate, comprising: a substrate; and a doped silica layer having a thickness of 5 to 1000 nm and a dopant:silicon atomic ratio of 0.5:99.5 to 15:85, wherein the dopant is P. +5 is.

[0009] The doped silica layer on the substrate can be further characterized by one or any combination of the following: the layer has a thickness in the range of 5-500, 5-200, 5-100, 10-1000, 10-500, 10-200, or 10-100 nm; the layer has a dopant:silicon atomic ratio of 1:99-15:85, or 1:99-10:90, or 1:99-5:95; and the layer has a dopant:silicon atomic ratio of ≥ 1 × 10 -10 , or 5 × 10 -11 ~5×10 -10 range, or 5×10 -11 ~2×10 -10 cm 2 / s, and the substrate includes a cathode, an anode, or glass.

[0010] In a further aspect, the present invention provides a method for producing a doped silica layer on a substrate, the method comprising providing a substrate, applying a silica layer to the substrate by CRISP ALD, and treating the silica layer with phosphorus gas in which phosphorus is in the +3 oxidation state. In some embodiments, the phosphorus gas comprises trialkoxy phosphite or trimethoxy phosphite. The method can include, for example, 5 to 30 cycles of CRISP ALD followed by 1 to 5 cycles of phosphorus gas treatment. To form thicker layers, multiple cycles can be included to form thicker layers, with one cycle comprising 5 to 30 cycles of CRISP ALD followed by 1 to 5 cycles of phosphorus gas treatment.

[0011] The present invention includes a method for electrolyzing water in which protons pass through a membrane to form dihydrogen. In another aspect, the present invention includes an optical device that utilizes an inventive coating. The present invention allows for the RI (refractive index) to be altered.

[0012] The present invention is further described in the following examples. In some preferred embodiments, the invention can be further characterized by any statement selected from the examples, such as within ±20% (or within ±10%) of any value in the examples, tables, or figures, although the scope of the invention in its broader aspects is not intended to be limited by these examples.

[0013] As in standard patent terminology, the term "comprising" means "including" and does not exclude additional elements. Any aspect of the invention described in conjunction with the term "comprising" also includes narrower embodiments in which the term "comprising" is replaced with the narrower terms "consisting essentially of" or "consisting of." As used herein, the terms "includes" or "including" should not be read as limiting the invention, but rather as listing exemplary elements. As in standard terminology, a "system" includes the apparatus and materials (e.g., reactants and products) and conditions within the apparatus. All ranges are inclusive and combinable. For example, if a range of "1 to 5" is recited, the recited range should be interpreted as including "1 to 4," "1 to 3," "1 to 2," "1 to 2 and 4 to 5," "1 to 3 and 5," "2 to 5," any of 1, 2, 3, 4, or 5 alone, etc. [Brief explanation of the drawings]

[0014] [Figure 1] 1 shows a plot of resistive drop versus film thickness. [Figure 2] The polarization curve of a typical PEM electrolyzer is shown. [Figure 3] Percent difference between the thickness of ALD POx-doped SiO2 films and "standard" undoped SiO2 ALD films as a percentage of the number of POx cycles in the total number of cycles for films produced using the super-cycle ALD scheme (#POx cycles / (#POx cycles + #SiOx cycles)). Data points are shown for films made using HO (dark blue circle) and O3 (orange circle) as complementary precursors used in conjunction with the dopant, phosphite, precursor. [Figure 4]1 is a bar graph of the percent difference between ALD POx-doped SiO2 film thickness and "standard" undoped SiO2 ALD film thickness as a percentage of the number of POx cycles in the total number of cycles for films produced using the super-cycle ALD scheme (#POx cycles / (#POx cycles + #SiOx cycles)). Positive numbers indicate an increase in thickness over the standard, and negative numbers indicate thinner films. This graph shows only the 20:2 ratio to highlight the differences between the four processes. [Figure 5] 1 is a bar graph comparing GPC at 80 nm on Si for four POx-doped SiOx processes. [Figure 6] XPS P content and H+ transmittance of four POx-doped SiOx processes. [Figure 7] Various data for P-doped silica films are shown. Samples containing at least 0.5 atomic % P showed a 10-fold improvement in pH compared to undoped silica. The P (atomic %) values ​​from XPS were 0.92, 0, 0.63, 0.02, and 0 for samples 1–5, respectively. [Figure 8] The plateau from the rotating disk electrode measurement and the calculated H+ permeability are shown. [Figure 9] 1 shows plots of transmittance for various doped samples. DETAILED DESCRIPTION OF THE INVENTION

[0015] The object of the present invention is to xThe goal is to controllably incorporate ALD chemistry to enhance H+ conductivity in ultrathin electrolytic bath films. Catalysis for the induced surface processing atomic layer deposition (CRISP ALD) process is a known process described in patents such as U.S. Pat. No. 7,250,083, which is incorporated herein as if reproduced in its entirety. A typical CRISP method for treating a solid film on a substrate includes introducing multiple catalytic reactants into a reaction chamber containing the solid film, where the catalytic reactants react in a sequential, non-saturating catalytic reaction that produces volatile by-products and intermediate reactive molecular fragments, whereby the intermediate reactive molecular fragments react with the solid film in fragment-film reactions, and further includes controlling the temperature of the conversion coating to control the treatment. In certain embodiments, the intermediate reactive molecular fragments include hydrogen, which is incorporated into the conversion coating during the fragment-film reactions. In other embodiments, the intermediate reactive molecular fragments include hydrogen atoms, which improve the interface between the solid film and the substrate. In an example of film treatment using the CRISP method, the intermediate reactive molecular fragments contain P dopant atoms, which are incorporated into the conversion coating during the fragment-film reaction.

[0016] The method used was a BEMAS / CRISP SiO2 ALD process modified by doping. First tests investigated the ability of different chemicals to incorporate into the growing SiO2 film, then PO xThe effect of doping on H+ conductivity and H2 / O2 permeability was characterized. Reactive precursors included bis(ethylmethylamino)silane (BEMAS), (H3Si)2NSiH2NEt2 (Orthrus), and bis(diisopropylamino)disilane (BDIPADS). Samples were sent for X-ray reflectivity (XRR) and X-ray photoelectron spectroscopy (XPS) measurements and further characterization (H+ conductivity, O2 / H2 gas permeability, SEM). The initial chemistries studied were trimethyl phosphite (P(OMe)3) and triethyl phosphite (P(OEt)3). During development, H2O, O3, and no conversion step were explored. For example, 20 cycles of the BEMAS / CRISP SiO2 process were performed, followed by two cycles of the P(OMe)3 / H2O process. The 22-super cycle system was run five times and the thickness was checked by comparing it with another wafer with the same total number of cycles (100 cycles) of SiO2. If the thickness was thicker or thinner than expected, the PO x It was preliminarily assumed that there was some incorporation of P or some ligand influence. The goal was to be able to controllably integrate P from 1-15% (atomic %). Additionally, more traditional P-doping ALD precursors such as diethyl phosphoramidate (DEPA) and trimethyl phosphate (TMPO) were also tested. All tests in this project were performed at a wafer temperature of 250 °C.

[0017] Thinner films have lower H+ permeability than Nafion. As the overall thickness decreases, H+ permeability decreases, but efficiency remains high. Figure 1 shows the ohmic drop versus film thickness under different H+ permeability / conductivity. It should be noted that ohmic drop is the largest cause of efficiency loss in electrolyzers, preventing higher current densities from being achieved (higher current densities also improve efficiency). POx doping improves the H+ conductivity of our undoped ALD films by at least 5 times at film thicknesses of 10–100 nm without sacrificing the gas permeability of the film.

[0018] Before deposition on the Pt sample, PO xPrecursors were screened in two ways. First, a conventional ALD cycle consisting of a P precursor and an oxygen source was periodically added to the supercycle to determine the effect on GPC compared to undoped SiO2 (BEMAS / CRISP) films deposited on separate wafers. Furthermore, P precursors were added to the BEMAS / CRISP process without a conversion step before and after the CRISP step, and the thickness was compared to that of an undoped SiO2 monolith. Reactions between BEMAS and both phosphite precursors were tested, but no reaction was found to occur. The deposition temperature for all films was maintained at 250 °C. Thickness during development was investigated using a single-wavelength (633 nm) Stokes meter ellipsometer with a fixed refractive index (RI) of 1.44. For thicker films >80 nm, spectroscopic ellipsometry (SE) at a fixed angle (75°) was used to determine thickness, RI, and extinction coefficient (k). The cos(2Ψ) and sin(2Ψ)cos(Δ) were modeled from data generated using a dual light source (combined deuterium and halogen sources) and a Si-based array detector in the 225-1000 nm range. Regression analysis was performed via a Levenberg-Marquardt fitting algorithm employing variance methods (Cauchy, Exponential, Sellmeier, and Tauc-Lorentz), and the model was fitted to the wavelength range of 250-1000 nm. Growth per cycle (GPC), RI, and k for the two ALD processes deposited on all samples are shown in Table 2 below. It should be noted that the goodness of fit (GOF) is a term that measures the accuracy of the model relative to the raw data. A value greater than 0.96 is considered an accurate fit. [Table 2]

[0019] Differences in thickness were observed in both the P(OEt)3 and P(OMe)3 systems using H2O and O3. At lower thicknesses, the difference in thickness between SiO2 and PO3 is shown in Figure 3. x The thickness increase with respect to the ratio is PO for the P(OMe)3 / H2O process. xIt was observed that the SiO2 / PO3 process showed a decrease with increasing cycles and remained relatively flat for the P(OEt)3 / O3 process. x At the 20:2 cycle ratio (deposited as 9% points in Figure 3), the P(OEt)3 / H2O process showed less change than the P(OMe)3 / H2O process, and the P(OEt)3 / O3 process showed no statistically significant thickness change, as shown in Figure 3. The same data at a 10:1 ratio is shown as a bar graph in Figure 4. Comparing all four processes, the P(OMe)3 / H2O process showed the greatest thickness increase, while the P(OEt)3 / O3 process had essentially the same film thickness. The P(OMe)3 / O3 and P(OEt)3 / H2O processes showed virtually the same thickness increase. Interestingly, when thicker monolith samples were deposited, the GPC for the entire stack was lower than for the SiO2 monolith. This suggests an inappropriate model fitting thinner films, or a PO2 monolith. x The dynamic behavior of uptake (e.g., H-OEt or H-OMe by-products may cause inhibition, as observed by Elam and colleagues) 1 ) could be the cause. However, when comparing the GPC of the SiO2 cycle alone with the baseline, as shown in Figure 5, both processes using HO as a co-reactant have higher GPCs than the baseline, while both ABC-type ALD processes (BEMAS / CRISP / P(OR)3) have lower GPCs. These data strongly suggest that the GPC of POx is lower than that of SiO2, but the other hypotheses mentioned above cannot be ruled out. In all tests, the RI of the POx-doped films was lower than that of the monolith. Again, the P(OMe)3 / HO process showed the greatest decrease in RI, while the two P(OEt)3 processes showed the least change. The ability of SiO2 to lower the RI may have implications for optical fields and SiO2-based lasers. Based on these data, it was decided to further investigate the 10:1 cycle ratio of each phosphite using HO. Approximately 80 nm thick films were deposited on Si and subjected to further analysis (XPS, Raman, XRR, and XRD). 1 Yanguas-Gil, A., Peterson, KE, Elam, JW, Chem. Mater. 2011, 23, 4295-4297 and Yanguas-Gil, A., Libera, JA, Elam, JW, Chem. Mater. 2013, 25, 4849-4860.

[0020] Both phosphites were introduced into the BEMAS / CRISP process along with the conversion half cycle (HO or O) both before and after the CRISP conversion step (see Table 3). The data show that adding either phosphite precursor after BEMAS (before the CRISP conversion step) did not result in any appreciable change from the baseline BEMAS / CRISP process. Neither the GPC nor the RI were significantly different from the bulk ALD SiO deposited with BEMAS / CRISP. This result is somewhat expected, given that the two precursors (BEMAS / phosphite) do not react with each other and the GPC of the BEMAS / CRISP process is very high. Conversely, administering either precursor after the CRISP step (before BEMAS) clearly decreased the GPC and RI. Here, the GPC decreased slightly more in the P(OEt) process, while the RI decreased more in the P(OMe) process. To further test the BEMAS / CRISP / phosphite process, thick films (approximately 80 nm) were deposited on Si and sent for further analysis (XPS, Raman, XRR, and XRD). [Table 3]

[0021] As mentioned above, all identified processes were also deposited on Pt-on-Si wafers to perform additional analytical measurements, such as H+ and H2 / O2 conductivity. Prior to introduction into the chamber, Pt-on-Si samples on 4-inch wafers were cut in half and sonicated in IPA for 5–10 minutes, then transferred to DI water and dried with compressed N2 air in a clean room. All Pt-on-Si half-4-inch wafers were run on 8-inch carrier wafers. Prior to ALD, all samples were exposed to O3 at the deposition temperature for 30 seconds and degassed for 5 minutes. To promote nucleation, all Pt-on-Si samples were subjected to 10 cycles of double the amount of BEMAS / CRISP, with the purge time for each half cycle doubled. While this was not necessary and was observed not to dramatically affect nucleation behavior, all previous tests on Si wafers were routinely performed with a nucleation layer of 10 BEMAS / CRISP layers. Most sample runs proceeded without issue. No obvious color change was observed for the 12-15 nm Pt samples. Thicker samples on Si were clearly different in color from uncoated Si. After deposition, all thin Pt on Si (5 total) and thick samples on Si wafers (4 total) were packaged separately in 4-inch wafer carriers for Pt and 2-inch wafer carriers for Si wafers for further testing.

[0022] The H+ permeability test results showed improved permeability for ABC-type ALD films using both precursors, as shown in Figure 6.

[0023] Interestingly, only the P(OMe)3 / H2O sample showed a slight increase in transmittance, while the P(OEt)3 / H2O sample showed no significant difference from the baseline. The best-performing film was the BEMAS / CRISP / P(OMe)3 film, which showed an almost order of magnitude increase in H+ transmittance compared to the baseline SiO2 film. The BEMAS / CRISP / P(OEt)3 film showed a 2.5-fold increase in H+ transmittance, while the P(OMe)3 / H2O film showed a 2-fold increase in H+ transmittance.

[0024] These data show that P(5+)(PO3 -1 This is supported by XPS measurements showing a high P content (no other P species were observed) in the P(OEt)3 / H2O process, but not in the P(OEt)3 / H2O process. There is a correlation between P% and H+ permeability, at least between each precursor. For example, the H+ permeability of the two P(OMe)3 samples is directly related to P content, whereas the P(OEt)3 sample exhibited the highest P% but only moderate H+ permeability.

[0025] H + Permeability is measured in an acidic solution of H2SO4 / Na2SO4 at room temperature with a three-electrode setup using a rotating disk electrode for the sample (this minimizes bubble formation on the electrode, resulting in more reliable results), a carbon rod for the counter electrode, and Ag / AgCl for the reference electrode (the concentration varies depending on the type of measurement, but values ​​can range from 5 to 500 mM). The disk can rotate at 5 to 1000 rpm (revolutions per minute), while the potential is swept from negative to positive potentials, preferably at a rate of 50 mV / s (but can vary from 1 to 500 mV / s) (relative to the reversible hydrogen electrode, RHE). H migrates across the membrane. + The current density, which is related to the amount of H passing through the membrane, is measured and a plateau is found. The more negative the plateau current density, the greater the amount of H passing through the membrane. + Figure 8 illustrates this last point by plotting the plateau and the calculated H + The transmittance is shown.

[0026] A general description of atomic layer or molecular layer deposition Atomic layer deposition techniques allow the deposition of coatings from about 0.1 to about 5 angstroms thick per reaction cycle, providing a means of very fine control over surface coverage or coating thickness. Thicker coatings can be prepared by repeating the reaction sequence to sequentially deposit additional layers of coating material until the desired coating thickness is achieved.

[0027] Coatings are deposited using atomic layer deposition (ALD) or molecular layer deposition (MLD) processes. In ALD / MLD processes, the coating formation reaction is carried out as a series of (typically) two half-reactions. In each of these half-reactions, a single reagent (precursor) is introduced into contact with the substrate surface. The conditions are such that the reagent is in gas form. In most cases, the reagent reacts with functional groups on the particle's surface and becomes bonded to the particle. Because the reagent is a gas, it penetrates pores within the substrate and deposits on the inner surfaces of the pores and the outer surface of the substrate. The precursor is designed to react with the surface at all available surface sites, but not with itself. In this way, the first reaction occurs, forming a single monolayer or submonolayer, creating new surface functionality. The excess reagent is then removed, helping to prevent the growth of undesired, larger inclusions in the coating material. Each of the remaining half-reactions is then carried out in sequence, each time introducing the first reagent, allowing it to react with the particle's surface, and removing the excess reagent before introducing the next reagent. Typically, an inert carrier gas is used to introduce the reagents, and the reaction chamber is typically swept with the carrier gas between successive reagent introductions to help remove excess reagents and gaseous reaction products. A vacuum can be swept during and between successive reagent dispenses to further remove excess reagents and gaseous reaction products.

[0028] After exposure to the first precursor, the surface is exposed to a second precursor, typically dispersed in an inert carrier gas. This precursor is designed to react with the functional groups deposited in the first reaction step. This reaction occurs until all available surface sites have reacted. The second precursor also does not react with itself. Any excess second precursor is removed in an optional inert gas purge step. If the gases are properly metered, the purge step may not be necessary. This can be at least a four-step process (precursor 1, purge, precursor 2, purge) to deposit one monolayer of the growing film. This does not mean only a single precursor, as some ALD and MLD processes use multiple reactants in one step, such as APTES / H2O / O3 to deposit SiO2. This process is repeated as many times as necessary to create the desired film thickness. ALD / MLD processes can begin with a "linker" agent or pretreatment gas (such as ozone) that promotes covalent bonding to the surface, or can be terminated with hydrophobic, hydrophilic, or purpose-designed terminators.

[0029] Reaction conditions are selected to satisfy three main criteria. The first criterion is that the reagents must be gaseous under the reaction conditions. Therefore, temperature and pressure conditions are selected so that the reactants volatilize before reaction. The second criterion is one of reactivity. Conditions, particularly temperature, are selected so that the desired reaction between the film-forming reagents (or, at the start of the reaction, the initially introduced reagents and the particle surface) occurs at a commercially reasonable rate. The third criterion is that the substrate must be thermally stable, both chemically and physically. The substrate must not decompose or react at the process temperature, except for potential surface functional groups that may react with one of the ALD precursors early in the process. Similarly, the substrate must not melt or soften at the process temperature, so that the physical shape of the substrate, particularly its pore structure, is maintained. The reaction is generally carried out at temperatures between about 270 and 1000 K, preferably between 290 and 450 K, and the specified temperature in each case is below the temperature at which the substrate melts, softens, or decomposes.

[0030] During the sequential administration of reagents, the particles are exposed to conditions sufficient to remove reaction products and unreacted reagents. This can be achieved, for example, by subjecting the particles to about 10 -5 This can be achieved by subjecting the particles to a high vacuum of Torr or higher. Another way to achieve this, which is more readily applicable to industrial applications, is to sweep the particles with an inert purge gas between reaction steps. This purge gas acts as both a fluidizing medium for the particles and a carrier for the reagents.

[0031] Several techniques are useful for monitoring the progress of the reaction. For example, vibrational spectroscopy studies can be performed using transmission Fourier transform infrared techniques. The deposited coating can be examined using in situ spectroscopic ellipsometry. Atomic force microscopy studies can be used to characterize the roughness of the coating relative to the surface roughness of the substrate. X-ray photoelectron spectroscopy and X-ray diffraction can be used to perform depth profiling of the coating and confirm the crystalline structure.

[0032] Aluminum oxide coatings are easily deposited using trimethylaluminum and water as precursors, as shown in reaction sequence A1 / B1. The reactions shown are not balanced and are intended to show only the reactions at the surface of the substrate (i.e., no inter- or intra-layer reactions). Substrate-XH* + Al(CH3)3 = Substrate-X-Al*-CH3 + CH4 (precursor reaction) Substrate-X-Al*-CH3+H2O=Substrate-X--Al-OH*+CH4(A1) Substrate-X-Al-OH*+Al(CH3)3=Substrate-X-Al-OAl*-CH3+CH4(B1)

[0033] In reaction A1 / B1, X is typically oxygen, nitrogen, or sulfur, and the asterisk (*) represents a surface species where the next half-reaction may occur. Aluminum oxide films are formed by alternating reactions A1 and B1 until the desired coating thickness is achieved. Using this reaction sequence, aluminum oxide films tend to grow at a rate of approximately 0.1 nm / cycle.

[0034] Titanium oxide coatings are easily deposited using titanium tetrachloride and water and / or hydrogen peroxide as precursors, as shown in reaction sequence A2 / B2. As mentioned previously, the reactions shown are not balanced and are intended to show only the reactions at the surface of the particles (i.e., there are no inter- or intra-layer reactions). Substrate-XH*+TiCl4 = Substrate-X--Ti*-Cl3+HCl (precursor reaction) Substrate-X--Ti*-Cl3+H2O2=Substrate-XTi*-OH+HCl+Cl2(A2) Substrate-X-Ti*-OH+TiCl4 Substrate-X-Ti-O-Ti*-Cl3+-HCl(B2)

[0035] In reaction A2 / B2, X is typically oxygen, nitrogen, or sulfur, and the asterisk (*) represents a surface species at which the next half-reaction may occur. Titanium oxide films are formed by alternating reactions A2 and B2 until the desired coating thickness is achieved. Titanium oxide films tend to grow at a rate of approximately 0.05-0.1 nm per cycle using this reaction sequence.

[0036] As is known in ALD / MLD processes, the order can be AB, ABC, ABCD, ABCDABABCD, or any desired order, provided the chemical entities react with each other in the desired order. Each of the reactants has at least two reactive moieties (this includes the possibility that the reactants can be modified to have two reactive moieties, such as having a first reactive moiety and a second reactive moiety that are temporarily blocked by a protecting group or require activation for subsequent reaction, such as UV activation). In some preferred embodiments, the reactants have exactly two reactive moieties, as a higher number of reactive groups can result in lower packing density. In some preferred embodiments, the film has at least three repeating units (e.g., ABABAB), or at least 5, or at least 10, or at least 50, sometimes in the range of 2-1000, or 5-100. By "reactive," we mean under typical MLD conditions and within commercially relevant timescales (e.g., at least 50% reacted within 10 hours under appropriate reaction conditions). To control the quality of the film, the reactants can be monoreactive during each step of the MLD process to avoid reacting twice with the surface, and the reactants must not self-react and condense on the surface.

[0037] In some preferred embodiments, the reactive moieties on reactant A may include isocyanates (R-NCO), acrylates, carboxylic acids, esters, epoxides, amides, and amines, as well as combinations thereof. In some preferred embodiments, reactant A includes a diisocyanate, diacrylate, dicarboxylic acid, diester, diamide, or diamine. In some preferred embodiments, the reactive moieties on reactant B include an alcohol or amine, as well as combinations thereof. In some preferred embodiments, reactant B includes a diol, amine alcohol, or diamine.

[0038] In some cases, particularly in MLD, the selected gas-phase reactant reacts only monofunctionally with the substrate or growing polymer chain, i.e., under the reaction conditions, only one group or moiety on the gas-phase reactant can react with the substrate or growing polymer chain. This prevents undesired crosslinking or chain termination that could occur if the gas-phase reactant reacted polyfunctionally. A reactant is considered to react "monofunctionally" if it forms a bond to only one polymer chain during the reaction and does not self-polymerize under the reaction conditions used. As explained more fully below, in certain embodiments of the invention, it is possible to use gas-phase reactants that can react difunctionally with the substrate or growing polymer chain, provided that the gas-phase reactant contains at least one additional functional group. In this aspect of the invention, reactants with exactly two functional groups with approximately equal reactivity are preferably avoided.

[0039] The first class of suitable gas-phase reactants are compounds that have two different reactive groups, one of which is reactive with a functional group on the substrate or polymer chain, and the other of which does not readily react with a functional group on the polymer chain but will react with a functional group provided by a different gas-phase reactant. Examples of reactants in this class are:

[0040] a) Hydroxyl compounds with vinyl or allylic unsaturation. These can react with carboxylic acid, carboxylic acid halide, or siloxane groups to form esters or silicon-oxygen bonds, introducing vinyl or allylic unsaturation into the polymer chain. Alternatively, the unsaturated groups can react with primary amino groups in a Michael reaction to extend the polymer chain and introduce hydroxyl groups into the chain.

[0041] b) Aminoalcohol compounds. Amino groups can react with carboxyl groups, carboxylic acid chlorides, vinyl or allyl groups, or isocyanate groups, for example, to extend the polymer chain and introduce hydroxyl groups into the chain. Alternatively, hydroxyl groups can react with siloxane species to form silicon-oxygen bonds and introduce free primary or secondary amino groups.

[0042] A second class of suitable gas-phase reactants includes a variety of cyclic compounds that can participate in ring-opening reactions, which generate new functional groups that do not readily react with the cyclic compound. Examples of such cyclic compounds include, for example, the following:

[0043] a) Cyclic azasilanes, which can react with hydroxyl groups to form silicon-oxygen bonds and generate free primary or secondary amino groups.

[0044] b) Cyclic carbonates, lactones, and lactams. Carbonates can react with primary or secondary amino groups to form urethane linkages and generate free hydroxyl groups. Lactones and lactams can react with primary or secondary amino groups to form amide linkages and generate free hydroxyl or amino groups, respectively.

[0045] A third class of gas-phase reactants includes compounds containing two different reactive groups. Both reactive groups will react with functional groups on the polymer chain, but one is much more reactive with that functional group. This allows the more reactive group to react with the functional group on the polymer chain, while the less reactive group remains unreacted and available to react with another gas-phase reactant.

[0046] A fourth class of gas-phase reactants includes compounds containing two reactive groups, one of which is blocked or otherwise masked or protected so that it is unavailable for reaction until the blocking, masking, or protecting group is removed. In some cases, the blocking or protecting group can be removed chemically; in other cases, it can be removed by thermal decomposition of the blocking group to produce the underlying reactive group, by irradiating the group with visible or ultraviolet light, or in a photochemical reaction. The unprotected group can be, for example, an amino group, an anhydride group, a hydroxyl group, a carboxylic acid group, a carboxylic acid anhydride group, a carboxylic acid ester group, an isocyanate group, or the like. The protected group can be one that yields any of the above types of functional groups after removal of the protecting group.

[0047] This fourth class of reactants may have hydroxyl groups protected by leaving groups such as benzyl, nitrobenzyl, tetrahydropyranyl, -CHOCH, or similar groups. In these cases, the hydroxyl groups can be deprotected in a variety of ways, including treatment with HCl, ethanol, and, in some cases, radiation. Carboxyl groups may be protected by leaving groups such as -CHSCH, t-butyl, benzyl, dimethylamino, and similar groups. These groups may be deprotected by treatment with species such as trifluoroacetic acid, formic acid, methanol, or water to generate carboxylic acid groups. Amino groups may be protected by groups such as R-OOC-, which can be removed by reaction with trifluoroacetic acid, hydrazine, or ammonia. Isocyanate groups may be protected by carboxylic compounds such as formic acid or acetic acid.

[0048] A fifth class of gas-phase reactants contains a first functional group and a precursor group that can undergo further reaction to produce a second functional group. In such cases, the first functional group reacts to attach to the polymer chain, and then a chemical reaction occurs with the precursor group to produce the second functional group. The first functional group can be any of the types previously mentioned, including siloxane, amino, anhydride, hydroxyl, carboxylic acid, carboxylic anhydride, carboxylic ester, isocyanate, and the like. A wide variety of precursor groups can be present on this type of reactant.

[0049] The precursor groups may not themselves react with polymer chains, but can be converted into functional groups capable of reacting with other gas-phase reactants to propagate the chain. Two notable types of precursor groups are vinyl and / or allylic unsaturation and halogen substitution, particularly chlorine or bromine. Vinyl and allylic unsaturation can be converted into functional groups using various chemical reactions. They can react with ozone or peroxide to form carboxylic acids or aldehydes. They can also react with ammonia or primary amines to produce amines or imines. The halogens can be substituted with various functional groups. They can be reacted with ammonia or primary amines to introduce amino groups, and, if desired, can be reacted with phosgene to produce isocyanate groups.

[0050] Reactants used to convert precursor groups to functional groups or to unmask or deprotect functional groups are introduced in the vapor phase. Excess reactants of this type are typically removed by sweeping a high vacuum through the reaction zone, purging the chamber with a purge gas, or both, before introducing the next reactant. Reaction by-products are removed in the same manner before introducing the next reactant into the reaction zone.

[0051] In some preferred embodiments, at least one or all of the reactants in the MLD repeat unit have a chain length between reactive moieties of 2 to 20 atoms, or 2 to 10 atoms, or 2 to 5 atoms (typically carbon atoms, although hetero groups such as oxygen may be present). In some preferred embodiments, the reactants have linear chains (i.e., no branching) between reactive moieties to increase packing density. In some preferred embodiments, the chains between reactive moieties are non-reactive. However, in some embodiments, there may be moieties within the chain that are capable of crosslinking to adjacent chains. In some embodiments, the capping layer and / or MLD layer at or very near the surface (e.g., within 5 cycles or within 2 cycles of the capping layer or surface) are branched to increase hydrophobicity.

[0052] The inorganic layer applied to the particles in the first step preferably becomes covalently bonded to the substrate. This can occur when the first applied precursor compound reacts with functional groups on the surface of the substrate under the conditions of the atomic layer deposition process. Examples of such functional groups are, for example, hydroxyl, carbonyl, carboxylic acid, carboxylic acid anhydride, carboxylic acid halide, primary or secondary amino.

[0053] Some ALD coatings are aluminum oxide and / or titanium oxide coatings. "Aluminum oxide" is used herein to refer to coatings composed substantially entirely of aluminum and oxygen atoms, regardless of specific stoichiometry. In many cases, aluminum oxide coatings are expected to closely conform to the empirical structure of alumina, i.e., Al2O3, although deviations from this structure are common and can be substantial. "Titanium oxide," as used herein, refers to coatings composed substantially entirely of titanium and oxygen atoms, regardless of specific stoichiometry. In most cases, titanium oxide coatings are expected to closely conform to the empirical structure of titania, i.e., TiO2, although deviations from this structure are common and can be substantial.

[0054] Except for half-reactions within the broader aspects of the present invention, atomic layer deposition processes are characterized by the need for at least two different reactants to form a coating layer. The reactants are introduced individually, sequentially, in the vapor phase into a reaction zone. Excess reactant is removed from the reaction zone before the next reactant is introduced. During the sequential introduction of reagents, reaction by-products are also removed. This procedure ensures that the reaction occurs at the surface of the substrate, not in the vapor phase.

[0055] A purge gas is typically introduced between alternating reactant feeds to further aid in the removal of excess reactants. The carrier gas, usually but not necessarily the same as the purge gas, is generally (but not necessarily) introduced as each reactant is introduced. The carrier gas may perform several functions, including (1) facilitating the removal of excess reactants and reaction by-products, and (2) distributing the reactants through the reaction zone, thereby helping to expose all surfaces to the reactants. The purge gas does not undesirably react with the ALD reactants or the deposited coating or interfere with their interaction at the substrate's surface.

[0056] Temperature and pressure conditions vary depending on the specific reaction system, as gaseous reactants must be supplied. As is known from ALD / MLD processes, the temperature must be high enough to produce the reactants in the gas phase, but not so high that the products are degraded.

[0057] ALD / MLD coatings can include any coating that can be applied by molecular layer deposition or atomic layer deposition. Known coatings that can be applied to core particles of metal or other materials include oxides or mixed oxides (e.g., Al2O3, TiO2, ZnO, ZrO2, SiO2, HfO2, Ta2O5, LiNb x O y ), nitrides (e.g., TiN, TaN, WN, TiYN), sulfides (e.g., ZnS, CdS, SnS, WS, MoS, ZnInS), and phosphides (e.g., GaP, InP, Fe 0.5 Co0.5 Lesser known materials applicable to core particles include transition metals (e.g., of Al, Cu, Co, W, Cr, Fe, Zn, Zr, Pt, Pd), metal fluorides (e.g., AlF3, MgF2, ZnF2), oxyfluorides and oxynitrides of transition metals, lanthanides (Y, YN, La2O3, LaF3, Nb, Dy2O3, Nd, LaB6, La2S3, etc.) in elemental, oxide, fluoride, nitride, boride, or sulfide form, borides (e.g., TiB2), carbides (e.g., B4C, WC), silane, silicides, etc. The coating may include, but is not limited to, polymers (e.g., polyamides, polyethylenes, polyamides, polyureas, polyurethanes), hydrocarbons, polymers or fragments of amino acids or other biologically relevant molecules and polymers, and other materials, fluorinated polymers (e.g., fluorine- or perfluoropolyamides, perfluoropolyethylenes, perfluoropolyamides, perfluoropolyureas, perfluorourethanes, perfluorohydrocarbons). The coating is highly uniform across the particle, preferably varying in thickness by 20% or less, more preferably 10% or less, or 5% or less across the surface of the particle. This high uniformity is a hallmark of ALD / MLD processes.

Claims

1. 1. An electrolytic cell comprising: comprising an anode, a cathode, and a doped silica electrolyte layer; The anode and the cathode are separated by 1 μm or less; the anode and the cathode are separated by the doped silica electrolyte layer; The doped silica electrolyte layer comprises: a thickness of 5 to 1000 nm; a dopant:silicon atomic ratio of 0.5:99.5 to 15:85, and H+ transmittance (cm ２ / s) ≥ 5 × 10 －１１ The electrolytic cell comprising:

2. 10. The electrolytic cell of claim 1, wherein the doped silica electrolyte layer has a thickness in the range of 5 to 500, 5 to 200, 5 to 100, 10 to 1000, 10 to 500, 10 to 200, 10 to 100 nm.

3. 10. An electrolytic cell according to any preceding claim, wherein the doped silica electrolyte layer has a dopant:silicon atomic ratio of from 1:99 to 15:85, or from 1:99 to 10:90, or from 1:99 to 5:

95.

4. The doped silica electrolyte layer has a conductivity of ≥ 1 × 10 －１０ , or 5 x 10 －１１ ~5 x 10 －１０ range, or 5 x 10 －１１ ~2 x 10 －１０ cm ２ 10. An electrolytic cell according to any preceding claim, having an H+ permeability in the range of 0.15 to 1.25 kJ / s.

5. The dopant is P ＋５ Electrolyzer according to any of the preceding claims, wherein

6. A doped silica layer on a substrate, A substrate; a thickness of 5 to 1000 nm; a doped silica layer having a dopant:silicon atomic ratio of 0.5:99.5 to 15:85; The dopant is P ＋５ a doped silica layer on said substrate,

7. 7. The doped silica layer on a substrate according to claim 6, having a thickness in the range of 5 to 500, 5 to 200, 5 to 100, 10 to 1000, 10 to 500, 10 to 200, 10 to 100 nm.

8. A doped silica layer on a substrate according to any of claims 6 to 7, having a dopant:silicon atomic ratio of from 1:99 to 15:85, or from 1:99 to 10:90, or from 1:99 to 5:

95.

9. ≧1×10 －１０ , or 5 x 10 －１１ ~5 x 10 －１０ range, or 5 x 10 －１１ ~2 x 10 －１０ cm ２ 10. A doped silica layer on a substrate according to any of the preceding claims, having an H+ permeability in the range of 100 / s.

10. 10. A doped silica layer on a substrate according to any preceding claim, wherein the substrate comprises a cathode, an anode or glass.

11. 1. A method for producing a doped silica layer on a substrate, comprising: providing the substrate; applying a silica layer by CRISP ALD; treating the silica layer with phosphorus gas in which phosphorus is in the +3 oxidation state.

12. The method of claim 11 , wherein the lingus comprises a trialkoxy phosphite.

13. 12. The method of claim 11, wherein the lingus comprises trimethoxy phosphite.

14. The method according to any one of claims 11 to 13, wherein the CRISP ALD comprises 5 to 30 cycles followed by 1 to 5 cycles of phosphorus gas treatment.

15. 15. The method of claim 14, wherein one cycle comprises 5 to 30 cycles of CRISP ALD followed by 1 to 5 cycles of phosphorus gas treatment, and includes multiple cycles to form thicker layers.

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