Modified cerium oxide loaded noble metal-based catalyst and preparation method thereof
By using a noble metal-based catalyst supported by modified cerium oxide in electrolytic hydrogen production technology, the problem of electrode overpotential increases is solved, catalytic activity and durability are improved, energy consumption and production costs are reduced, and high-efficiency scale is achieved Chemical hydrogen production.
Patent Information
- Application Number
- CN202411980148.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-02-18
AI Technical Summary
In the existing electrolytic hydrogen production technology, the interface reaction energy barrier between the electrode and the electrolyte leads to an increase in overpotential, increasing energy consumption and production costs, and limiting large-scale hydrogen production.
The modified cerium oxide-supported noble metal-based catalyst was prepared by the sol-gel method, and the precious metal nanoparticles were loaded by the alcohol reduction method to enhance the interaction between the support and the active substances, thereby improving catalytic activity.
At lower precious metal loading, the catalyst has excellent hydrogen evolution activity and good durability, reduced overpotential, reduced energy consumption, and its performance is close to commercial 20 wt% Pt/C.
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Figure CN119465248A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of hydrogen production by electrolysis of water, and specifically relates to a modified cerium oxide-loaded noble metal-based catalyst and a preparation method and application thereof. Background Art
[0002] Electrocatalytic water decomposition to produce hydrogen is currently the cleanest method. It uses abundant water as the raw material basis, does not consume or produce any carbon-containing substances, and has the advantages of simple operation process, high yield, and high hydrogen purity. Combined with new energy power generation technologies such as wind power and solar energy, the sustainable development of the "hydrogen economy" can be achieved. The hydrogen evolution reaction occurs at the cathode potential end of the water electrolysis device, and oxygen is generated at the anode end. However, in actual production, the hydrogen evolution reaction rarely starts at its theoretical potential. This is because there is an energy barrier for the interfacial reaction between the electrode and the electrolyte, and more electrical energy needs to be provided to overcome the reaction energy barrier, resulting in excessive production costs and energy consumption, which greatly limits large-scale hydrogen production. Designing and using highly active electrocatalysts to improve electrochemical conversion efficiency and reduce inherent energy barriers are necessary prerequisites for large-scale hydrogen production.
[0003] Ideally, when electrolyzing water, a potential difference of only 1.23V between the anode and cathode is sufficient to start the water splitting reaction to produce hydrogen. However, in the actual process of electrolyzing water to produce hydrogen, a higher voltage is usually required to split the water molecules into hydrogen and oxygen. The additional voltage required is the overpotential. The overpotential of hydrogen evolution at the cathode and oxygen evolution at the anode will lead to an increase in actual energy consumption, which has become a bottleneck restricting the development of water electrolysis in the engineering field. Therefore, it is necessary to reduce the overpotential to make the water splitting reaction more energy-efficient and efficient.
[0004] As the most critical link in the water electrolysis system, the preparation of HER and OER electrodes with high catalyst activity is the key to reducing the high electrode overpotential. Therefore, the research and development of electrocatalytic electrode materials that can reduce the energy consumption of water electrolysis has important theoretical and practical significance. So far, among various electrode materials, Pt electrode has the best catalytic hydrogen evolution activity, but its scarce reserves and high cost limit its large-scale application. Therefore, the development of electrode materials with high hydrogen evolution activity and low precious metal loading is a hot topic in current research.
[0005] In the catalyst system, choosing a suitable carrier material can make the catalytic metal evenly dispersed, reduce the degree of metal nanoparticle agglomeration, and also improve the utilization rate of metal nanoparticles, thereby reducing the precious metal loading. More importantly, there can be special interactions between the carrier and the catalytic metal, which will have a significant impact on the catalytic activity and durability. Mastering the selection and modification technology of reasonable catalyst carrier materials has become an important part of the work of developing high-performance, low-cost energy catalysts.
[0006] Carbon-based carriers are one of the most widely used carrier materials and the most practical type of carrier material in electrocatalytic hydrogen evolution. Currently, carbon materials are usually used as carriers and then modified with other materials to make composite catalysts. Carbon-based carriers have attracted much attention in electrocatalytic research due to their high availability, large specific surface area and environmental friendliness. However, due to the severe electrochemical corrosion of carbon in acidic or alkaline electrolytes, the stability of carbon-based carrier catalysts is generally poor. In order to solve the problems of carbon carriers, a feasible and effective solution is to seek non-carbon carrier materials with good stability and low cost.
[0007] As a rare earth metal oxide with abundant reserves on earth, cerium dioxide (CeO2) exhibits excellent catalytic performance in CO oxidation, water gas conversion, methane activation, water splitting, fuel cells and other energy fields. CeO2 belongs to the cubic fluorite structure, which is a recognized fast ion conductor that allows ions to diffuse rapidly. Such a structure has many octahedral vacancies, so CeO2 is a non-stoichiometric variable valence compound. Even if a large number of oxygen vacancies are formed under oxygen-deficient conditions, it can still maintain the fluorite crystal structure, has good chemical stability, and has excellent oxygen storage and release functions and redox capabilities.
[0008] In recent years, metal oxides have attracted more and more attention in the field of catalysis due to their good physical and chemical properties. The properties of metal oxides can be adjusted or changed by partially replacing their own atoms with foreign atoms of other valence states. Many studies have shown that doping with metal elements or non-metal elements can effectively adjust the band structure and optical band gap of the material, thereby changing its catalytic activity. Summary of the invention
[0009] Based on the above technical knowledge, the inventors of the present invention have provided a modification scheme of cerium oxide and a noble metal-based catalyst made using the same after long-term and extensive research, wherein CeO2 is prepared by a sol-gel method, and then CeO2 is modified by P doping, and finally the noble metal particles are loaded onto P-CeO2 doped with P by an alcohol reduction method. The P-doped CeO2 in the present invention has more oxygen vacancies and more active sites, which enhances the interaction between the carrier and the active substance noble metal, thereby improving the activity of the catalyst.
[0010] To achieve the above object, the present invention adopts the following technical solution: One of the purposes of the present invention is to protect a modified cerium oxide-supported noble metal-based catalyst, which is composed of P-doped 2D-CeO2 as a carrier and noble metal nanoparticles as an active metal component.
[0011] Furthermore, based on the total weight of the catalyst, the content of the noble metal nanoparticles is 0.05-50wt%.
[0012] The second object of the present invention is to protect the preparation method of the modified cerium oxide-supported noble metal-based catalyst, which is to first prepare CeO2 with a two-dimensional morphology by a sol-gel method, then use a pyrolysis phosphate salt to dope the obtained CeO2 with P, and finally load the noble metal nanoparticles X thereon by an alcohol reduction method, thereby obtaining an X / P-CeO2 catalyst; which specifically includes the following steps: 1) The cerium precursor and alkali are added to deionized water respectively, and then stirred for 1-100 minutes respectively, and then ultrasonicated for 1-3 hours to fully disperse them. Then, the obtained alkali solution is slowly added to the cerium precursor solution under stirring conditions. After the addition is completed, stirring is continued for 0.1-10 hours to allow the reaction to proceed fully. The product is then collected by centrifugation, washed with deionized water several times, and freeze-dried to obtain a solid product of 2D-CeO2; 2) pyrolyzing the 2D-CeO2 obtained in step 1) together with a phosphate salt in an oxygen-free environment to obtain P-CeO2; 3) The P-CeO2 obtained in step 2) is dispersed in alcohol, and then the precursor solution of the precious metal X is added, and ultrasonic treatment is performed for 1-2 hours to fully disperse the platinum precursor and P-CeO2. The mixture is then transferred to an oil bath, and after magnetic stirring and reaction, it is naturally cooled to room temperature, centrifuged, washed with deionized water and ethanol, and freeze-dried to obtain an X / P-CeO2 catalyst.
[0013] Furthermore, the precursor of cerium in step 1) is cerium nitrate, cerium chloride, cerium sulfate or cerium oxalate.
[0014] Furthermore, the base in step 1) is NaOH, KOH, ammonia water or Ca(OH)2.
[0015] Furthermore, the mass ratio of the cerium precursor to the base used in step 1) is 1:1-100:1.
[0016] Furthermore, the phosphate salt in step 2) is sodium hypophosphite, ammonium dihydrogen phosphate, potassium dihydrogen phosphate or tripolyphosphate.
[0017] Furthermore, the mass ratio of 2D-CeO2 to phosphite used in step 2) is 4:1-1.5:1.
[0018] Furthermore, the pyrolysis temperature in step 2) is 300-1000°C, and the insulation time is 1-10h.
[0019] Furthermore, the alcohol in step 3) is ethylene glycol, triethylene glycol, or propylene glycol.
[0020] Furthermore, the precursor of the noble metal X in step 3) may be platinum, gold, rhodium, ruthenium, or a nitrate, chloride, sulfate, or sulfite thereof that forms an alloy with a transition metal.
[0021] Furthermore, the reaction temperature in step 3) is 100-200°C and the reaction time is 3-6h.
[0022] The third purpose of the present invention is to protect the application of the modified cerium oxide-supported noble metal-based catalyst in the electrolysis of water to produce hydrogen.
[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention dopes CeO2 with P to increase the oxygen vacancies of CeO2 and provide more active sites, thereby improving the catalytic activity of CeO2.
[0024] (2) The catalyst obtained by the present invention has excellent hydrogen evolution activity at a low loading amount of precious metals and has a high current density of 10 mA / cm 2 The overpotential is 28mV, and after 3000 voltammetric cycle tests, the overpotential can still be maintained at 31mV, which is significantly better than Pt / CeO2 with the same loading amount and close to commercial 20wt% Pt / C. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 Scanning electron microscope (SEM) images of CeO2 (A) and Pt / P-CeO2 (B) prepared in Example 1.
[0026] Figure 2 Transmission electron microscope (TEM) images of Pt / P-CeO2 (A) prepared in Example 1 and Pt / CeO2 (B) prepared in the comparative example.
[0027] Figure 3 The cyclic voltammetric polarization (LSV) curves of the electrode prepared by using the Pt / P-CeO2 catalyst prepared in the examples and comparative examples and the commercial platinum carbon electrode.
[0028] Figure 4 This is the cyclic voltammetry polarization (LSV) curve of the Pt / P-CeO2 catalyst prepared in Example 1 after 3000 endurance scans. DETAILED DESCRIPTION
[0029] A modified cerium oxide-supported noble metal-based catalyst, the preparation of which comprises the following steps: 1) The cerium precursor and the alkali are added to deionized water in a mass ratio of 1:1-100:1, respectively, and then stirred for 1-3 hours, and then ultrasonicated for 1-100 minutes to fully disperse them. Then, under stirring conditions, the obtained alkali solution is slowly added to the cerium precursor solution using a constant pressure dropping funnel. After the addition is completed, stirring is continued for 0.1-10 hours to allow the reaction to proceed fully, and the product is then collected by centrifugation, washed with deionized water several times, and freeze-dried to obtain a solid product of 2D-CeO2; 2) Weigh the 2D-CeO2 and phosphate obtained in step 1) at a mass ratio of 4:1-1.5:1, then spread the phosphate on the front end of the porcelain boat, spread the 2D-CeO2 on the rear end of the porcelain boat, cover the porcelain boat, and put the porcelain boat into a tube furnace, heat it to 300-1000°C in an oxygen-free environment, and keep it warm for 1-10 hours to obtain P-CeO2; 3) The P-CeO2 obtained in step 2) is dispersed in alcohol, and then a precursor solution of the precious metal X is added, and ultrasonic treatment is performed for 1-2 hours to fully disperse the precious metal precursor and P-CeO2, and then the mixture is transferred to a 100-200°C oil bath, and reacted with magnetic stirring for 3-6 hours, and then naturally cooled to room temperature, centrifuged, washed with deionized water and ethanol, and freeze-dried to obtain an X / P-CeO2 catalyst, wherein the content of precious metal nanoparticles is 0.05-50wt%.
[0030] Wherein, the precursor of the cerium is cerium nitrate, cerium chloride, cerium sulfate or cerium oxalate. The alkali is NaOH, KOH, ammonia water or Ca(OH)2. The phosphate salt is sodium hypophosphite, ammonium dihydrogen phosphate, potassium dihydrogen phosphate or tripolyphosphate. The alcohol is ethylene glycol, triethylene glycol, glycerol. The precursor of the precious metal X can be platinum, gold, rhodium, ruthenium or at least one of the nitrates, chlorides, sulfates or sulfites thereof that form an alloy with a transition metal. The transition metal can be copper, manganese, chromium, praseodymium, yttrium, dysprosium, erbium, ytterbium or titanium.
[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0032] Example 1 Preparation of modified cerium oxide carrier P-CeO2 and platinum-supported catalyst Pt / P-CeO2 (1) Preparation of two-dimensional CeO2 nanosheets by sol-gel method: First, 10 g Ce(NO3)3·6H2O and 5 g NaOH were dissolved in 100 mL deionized water, stirred for 1 h, and then ultrasonicated for 10 min to make the dispersion more uniform, thereby obtaining Ce(NO3)3·6H2O solution and NaOH solution; under room temperature magnetic stirring conditions, the NaOH solution was slowly added dropwise to the Ce(NO3)3·6H2O solution using a constant pressure funnel. After the addition was completed, stirring was continued for 1 h to allow the reaction to proceed fully; finally, the obtained reaction solution was separated by centrifuge (11000 rpm, 8 min), the solid product was collected, washed three times with deionized water, and freeze-dried to obtain the finished product.
[0033] (2) The two-dimensional CeO2 nanosheets and sodium hypophosphite obtained in step (1) are weighed in a mass ratio of 3:1, and then the sodium hypophosphite is spread on the front end of a porcelain boat and the CeO2 is spread on the rear end of the porcelain boat. The porcelain boat is covered and placed in a tubular furnace with the front end of the porcelain boat facing the air inlet direction of the tubular furnace and the rear end facing the air outlet direction of the tubular furnace. Nitrogen is passed through the tubular furnace for 30 minutes to remove excess air, and then the mixture is heated to 300°C at a heating rate of 15°C / min under the protection of nitrogen, kept warm for 10 hours, and then cooled to room temperature to obtain P-CeO2.
[0034] (3) Take 30 mg of P-CeO2 prepared in step (2), disperse it in 100 ml of ethylene glycol, and ultrasonicate it in an ultrasonic cleaner for 2 h to disperse the carrier. Then, add 2 ml of 4 mg / L chloroplatinic acid ethylene glycol solution, and ultrasonicate it for 1 h to fully disperse the chloroplatinic acid ethylene glycol solution. Then, transfer the mixture to a 120°C oil bath, react for 3 h under magnetic stirring, and then naturally cool to room temperature, centrifuge, wash with deionized water and ethanol, and freeze-dry to obtain a Pt / P-CeO2 catalyst with a Pt nanoparticle content of 10 wt%.
[0035] Example 2 The difference from Example 1 is that the 10 g Ce(NO3)3·6H2O and 5 g NaOH used in step (1) are replaced with 4.2 g CeCl3 and 7.2 g KOH weighed 7.2 g; the sodium hypophosphite used in step (2) is replaced with ammonium dihydrogen phosphate; the chloroplatinic acid used in step (3) is replaced with ammonium chlororuthenate, and the ethylene glycol used is replaced with triethylene glycol. The remaining operations are the same as in Example 1.
[0036] Example 3 The difference from Example 1 is that Ce(NO3)3·6H2O and NaOH used in step (1) are replaced by Ce2(SO2)3 and Ca(OH)2; the sodium hypophosphite used in step (2) is replaced by potassium dihydrogen phosphate; the chloroplatinic acid used in step (3) is replaced by chlororhodic acid, and the ethylene glycol used is replaced by propylene glycol. The remaining operations are the same as in Example 1.
[0037] Comparative Example The difference from Example 1 is that the two-dimensional CeO2 nanosheets prepared in step (1) are directly used to load the Pt nanoparticles without going through step (2). The relevant operations are the same as those in Example 1.
[0038] Figure 1 The scanning electron microscope (SEM) images of CeO2 (A) and Pt / P-CeO2 (B) prepared in Example 1. It can be seen from the figure that the prepared CeO2 and Pt / P-CeO2 are both two-dimensional sheet structures formed by stacking of energy bands, and the Pt particles are dispersed and loaded in the sheet structure of CeO2.
[0039] Figure 2 Transmission electron microscope (TEM) images of Pt / P-CeO2 (A) prepared in Example 1 and Pt / CeO2 (B) prepared in the comparative example. It can be seen from the figure that the Pt particles are more evenly distributed on the P-doped CeO2, while obvious agglomeration occurs on the CeO2 without P doping.
[0040] The catalysts prepared in the electrochemical workstation embodiments and comparative examples were subjected to electrochemical tests. The electrolyte solution used was a 0.5M H2SO4 solution, the test temperature was room temperature, the test system was a conventional three-electrode system, the graphite rod electrode was the counter electrode, and the saturated AgCl electrode was the reference electrode. All potentials in the test results were adjusted to the potential relative to the reversible hydrogen electrode (vs. RHE). The linear sweep voltammetry (LSV) test scan rate was 5mV / s, and a linear sweep voltammetry (LSV) test was performed. At the same time, as a comparison, the commercialized 20wt% Pt / C was used to perform electrochemical tests under the same test conditions, and the results are shown in FIG. Figure 3 Then, the electrode prepared by using the catalyst of Example 1 was subjected to cyclic voltammetry scanning at a scanning rate of 50 mV / s for 4000 times, and the LSV was tested once every 1000 scans at a scanning rate of 5 mV / s. Figure 4 .
[0041] Depend on Figure 3 It can be seen that the Pt / P-CeO2 prepared in Example 1 has a current density of 10 mA / cm 2The overpotential is 28 mV, which is significantly better than the 51 mV of the Pt / CeO2 catalyst not doped with P, and is also significantly better than the precious metal catalysts prepared in other embodiments. At the same time, its performance is also better than the commercial 20wt% Pt / C.
[0042] from Figure 4 It can be seen that the catalyst obtained in Example 1 has good stability and still has good electrocatalytic hydrogen evolution performance (31 mV) after 3000 endurance scans of the cyclic voltammetry polarization (LSV) curve.
[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes within the meaning and scope of the equivalent elements of the claims be included in the present invention.
[0044] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode includes only one independent technical solution. This narrative method of the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions of each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.
Claims
1. A modified cerium oxide supported noble metal-based catalyst, characterized in that: The platinum-based catalyst is composed of P-doped 2D-CeO2 as a carrier and noble metal nanoparticles as active metal components.
2. The modified cerium oxide-supported noble metal-based catalyst according to claim 1, characterized in that: Based on the total weight of the catalyst, the content of the noble metal nanoparticles is 0.05-50wt%.
3. A method for preparing a modified cerium oxide-supported noble metal-based catalyst as claimed in claim 1, characterized in that: First, two-dimensional CeO2 is prepared by a sol-gel method, then the obtained CeO2 is doped with P by thermally decomposing phosphate salt, and finally precious metal nanoparticles X are loaded thereon by an alcohol reduction method, thereby obtaining an X / P-CeO2 catalyst.
4. The method for preparing a modified cerium oxide-supported noble metal-based catalyst according to claim 3, characterized in that: The steps include: 1) The cerium precursor and the alkali are added to deionized water respectively, and then stirred for 1-100 minutes respectively, and then ultrasonicated for 1-3 hours to fully disperse them. Then, the obtained alkali solution is slowly added to the cerium precursor solution under stirring conditions. After the addition is completed, stirring is continued for 0.1-10 hours to allow the reaction to proceed fully. The product is then collected by centrifugation, washed with deionized water, and freeze-dried to obtain a solid product of 2D-CeO2; 2) pyrolyzing the 2D-CeO2 obtained in step 1) together with a phosphate salt in an oxygen-free environment to obtain P-CeO2; 3) The P-CeO2 obtained in step 2) is dispersed in alcohol, and then the precursor solution of the precious metal X is added, ultrasonicated for 1-2 hours, and then the mixture is transferred to an oil bath. After magnetic stirring and reaction, it is naturally cooled to room temperature, centrifuged, washed with deionized water and ethanol, and freeze-dried to obtain an X / P-CeO2 catalyst.
5. The method for preparing a modified cerium oxide-supported noble metal-based catalyst according to claim 4, characterized in that: The mass ratio of the cerium precursor to the base used in step 1) is 1:1-100:1; the cerium precursor is cerium nitrate, cerium chloride, cerium sulfate or cerium oxalate; and the base is NaOH, KOH, ammonia water or Ca(OH)2.
6. The method for preparing a modified cerium oxide-supported noble metal-based catalyst according to claim 4, characterized in that: The mass ratio of 2D-CeO2 to phosphate used in step 2) is 4:1-1.5:1; the phosphate salt is sodium hypophosphite, ammonium dihydrogen phosphate, potassium dihydrogen phosphate or tripolyphosphate.
7. The method for preparing a modified cerium oxide-supported noble metal-based catalyst according to claim 4, characterized in that: The pyrolysis temperature in step 2) is 300-1000°C and the insulation time is 10-100min.
8. The method for preparing a modified cerium oxide-supported noble metal-based catalyst according to claim 4, characterized in that: In step 3), the alcohol is ethylene glycol, triethylene glycol, or propylene glycol; the precursor of the precious metal X is platinum, gold, rhodium, ruthenium, or at least one of the nitrates, chlorides, sulfates, or sulfites thereof that form alloys with transition metals.
9. The method for preparing a modified cerium oxide-supported noble metal-based catalyst according to claim 4, characterized in that: The reaction temperature in step 3) is 100-200°C and the reaction time is 3-6h.
10. Use of the modified cerium oxide-supported noble metal-based catalyst as claimed in claim 1 in hydrogen production by water electrolysis.