Non-noble metal hydrazine hydrate decomposition hydrogen production catalyst as well as preparation method and application thereof

Abstract

The invention discloses a non-noble metal hydrazine hydrate decomposition hydrogen production catalyst as well as a preparation method and application thereof. Soluble Ni < 2 + > salt, soluble Cr < 3 + > salt and a precipitator are subjected to a hydrothermal reaction in water to obtain a hydrothermal sample, and the hydrothermal sample is subjected to heat treatment at 250-350 DEG C in a reducing atmosphere to obtain the non-noble metal hydrazine hydrate decomposition hydrogen production catalyst. The catalyst shows high activity, 100% selectivity and excellent stability, can efficiently and stably catalyze complete decomposition of hydrazine hydrate to produce hydrogen under mild conditions, and has activity superior to that of most currently reported non-noble metal nickel-based catalysts.

Description

Technical Field

[0001] The present invention belongs to the field of hydrogen production technology and catalytic material technology, and specifically relates to a non-precious metal hydrazine hydrate decomposition hydrogen production catalyst and a preparation method and application thereof. Background Art

[0002] Hydrogen energy is a clean and efficient secondary energy source. Its large-scale application involves significant scientific and technological challenges in numerous areas, including production, transportation, storage, and distribution. Transportation and storage have become a bottleneck restricting hydrogen energy development. Therefore, the development of hydrogen storage materials and production technologies is crucial for achieving sustainable development. Decades of research by scholars worldwide have shown that reported reversible hydrogen storage materials do not yet meet, or at least meet, the requirements for onboard fuel cell applications. Based on this current state of research, researchers around the world have been focusing on controlled hydrogen release technologies for chemical hydrogen storage materials since around 2000, sparking a surge in research on these materials. Hydrazine hydrate (N₂H₄·H₂O), a novel chemical hydride, not only possesses the typical characteristics of integrated hydrogen storage and production, but also offers significant advantages such as high hydrogen storage density (8 wt%), low cost (2 $ / L), good chemical stability, and the absence of solid byproducts in the hydrogen production reaction. It holds great potential for use as an onboard / portable hydrogen source.

[0003] Developing catalysts that combine high selectivity, high activity, and good stability for hydrogen production has been a key goal in developing practical, controllable decomposition of N₂H₄·H₂O for hydrogen production. Early studies demonstrated that nickel exhibits moderate activity and high selectivity for the decomposition of hydrazine hydrate to produce hydrogen. Alloying nickel with noble metals such as Pt, Ir, and Ru can completely decompose N₂H₄·H₂O to produce hydrogen under mild conditions. However, the rarity and high cost of noble metals severely restrict their widespread application. Consequently, extensive research has focused on developing non-noble metal catalysts, primarily supported Ni-based alloy catalysts. However, the catalytic activity of existing non-noble metal catalysts is one to two orders of magnitude lower than that of noble metal-containing catalysts. Furthermore, most non-noble metal catalysts suffer from selectivity and / or stability issues. Addressing these issues requires a deeper understanding of the decomposition behavior on the catalytic surface and a better understanding of the relationship between the atomic structure, electronic properties, and catalytic performance of N₂H₄. However, theoretical studies of the catalytic mechanism currently lag far behind experimental progress. In the literature, no sound theoretical model or clear causal relationship describes the decomposition of N₂H₄ on non-noble metal catalysts. Therefore, the search for high-performance and low-cost N₂H₄·H₂O decomposition catalysts still relies primarily on trial-and-error methods. This reliance on empirical methods has, to a certain extent, slowed the research progress of catalysts for hydrogen production from hydrazine hydrate decomposition. Consequently, the preparation of non-precious metal catalysts with high catalytic activity and stability remains a major challenge in the development of N₂H₄·H₂O-based hydrogen storage technologies. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a non-precious metal catalyst for hydrogen production from the decomposition of hydrazine hydrate, as well as its preparation method and application. Developing efficient and stable catalyst design concepts and controllable synthesis methods are key challenges that need to be addressed in advancing the practical application of hydrazine hydrate controllable hydrogen production technology. The present method utilizes readily available raw materials, is simple to operate, and is readily amenable to mass production. The resulting catalyst exhibits both high activity and stability, efficiently and stably catalyzing the decomposition of N₂H₄·H₂O to produce hydrogen under alkaline conditions.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a non-noble metal hydrazine hydrate decomposition hydrogen production catalyst comprises the following steps:

[0007] Soluble Ni 2+ Salt, soluble Cr 3+ The salt and the precipitant are hydrothermally reacted in water to obtain a hydrothermal sample, which is then heat-treated at 250-350° C. (reduction) under a reducing atmosphere to obtain a non-noble metal hydrazine hydrate decomposition hydrogen production catalyst.

[0008] Furthermore, the soluble Ni 2+ The salt is nickel nitrate, the soluble Cr 3+ The salt is chromium nitrate.

[0009] Furthermore, Ni 2+ The concentration of Cr is 0.03~0.1M; 3+ The concentration is 0.03~0.1M;

[0010] Furthermore, Ni 2+ and Cr 3+ The molar ratio is 1:1~3.

[0011] More preferably, Ni 2+ and Cr 3+ The molar ratio is 1:1.

[0012] Furthermore, the temperature of the hydrothermal reaction is 90 to 150° C., and the time of the hydrothermal reaction is 2 to 16 hours;

[0013] Furthermore, the reducing atmosphere is hydrogen; the heat treatment time is 1 to 2 hours; and the heat treatment temperature is 280 to 320°C.

[0014] More preferably, the heat treatment temperature is 300°C.

[0015] Further, the concentration of the precipitant is 0.1 to 0.2 M;

[0016] Furthermore, the precipitant and Ni2+ The molar ratio is 4 to 6:1.

[0017] More preferably, the precipitant and Ni 2+ The molar ratio is 4:1.

[0018] Furthermore, the precipitant includes at least one of sodium hydroxide, sodium carbonate, tetramethylammonium hydroxide, and urea.

[0019] Furthermore, after the hydrothermal reaction, the sample is washed and dried to obtain a hydrothermal sample.

[0020] More preferably, the drying temperature is 40-60° C., and the drying time is 6-12 hours.

[0021] The non-noble metal hydrazine hydrate decomposition hydrogen production catalyst prepared by the above preparation method.

[0022] The non-precious metal hydrazine hydrate decomposition hydrogen production catalyst comprises a metal alloy active phase and a metal oxide matrix phase. The metal alloy active phase is dispersed on the surface of the metal oxide matrix phase in the form of fine nanoparticles. The metal oxide matrix phase has high specific surface area and a nanoporous structure. The metal alloy active phase is an alloy of Ni and Cr, and the metal oxide matrix phase is an oxide of Ni and Cr.

[0023] The particle size of the metal alloy active phase is 5 to 10 nm.

[0024] The metal alloy active phase and the metal oxide matrix phase are nanostructured.

[0025] The metal oxide matrix phase has a strong interaction with the metal alloy active phase;

[0026] The metal oxide matrix phase exists in two forms: nanocrystalline and amorphous.

[0027] Application of the above-mentioned non-noble metal hydrazine hydrate decomposition hydrogen production catalyst in hydrazine hydrate decomposition hydrogen production.

[0028] The present invention constructs single metal and alloy models, optimizes the constructed models, and obtains structural and energy information. The adsorption energies of hydrazine molecules at the d-band centers and different sites of the two models are analyzed by theoretical calculation, and it is predicted that the catalytic activity of the alloy relative to hydrazine hydrate decomposition to produce hydrogen is stronger than that of the single metal.

[0029] The principle of this invention is to develop a highly efficient catalyst for hydrogen production from the decomposition of hydrazine hydrate based on theoretical predictions. Starting from activity predictions, combined with experimental screening, a catalyst with 100% selectivity and high stability was selected. The catalyst provided by this invention incorporates theoretical predictions in its design and provides a simple and feasible preparation method. First, using density functional theory (DFT) calculations, we determined that Ni-based alloys shift the d-band center upward relative to the Fermi level, potentially enhancing the activity of Ni-based catalysts for hydrogen production from the decomposition of hydrazine hydrate. Subsequently, to experimentally verify this theoretical prediction, we used a hydrothermal method to generate a nanostructured metal oxide precursor containing catalytically active components and possessing a high specific surface area, laying the material composition and structural foundation for the synthesis of a high-performance catalyst. By controlling the heat treatment conditions, the metal oxide was partially reduced to a metal alloy phase, simultaneously forming a metal alloy phase dispersed as fine nanoparticles on the surface of the metal oxide matrix phase. The in-situ precipitated metal alloy phase, serving as the catalytically active phase, imparts significant electronic structural differences to the metal alloy. This difference alters the interaction between the metal alloy phase and N2H4 molecules, facilitating H2 production. The dehydration reaction of the precursor material synthesized by hydrothermal synthesis during heating leads to the formation of a large number of nanopores, further increasing the specific surface area of ​​the material, thereby providing more active sites. In summary, the hydrazine hydrate decomposition hydrogen production catalyst provided by the present invention has high activity, selectivity, and stability.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] (1) The present invention is different from the traditional empirical trial and error method. Based on the first principles and theoretical prediction, it screens out alloy component elements that may have higher activity. It can solve the problems of long cycle, many trial and error times, and high cost in the development of hydrazine hydrate decomposition hydrogen production catalysts in the existing technology, and realize the synthesis of efficient hydrazine hydrate decomposition hydrogen production catalysts.

[0032] (2) The present invention uses a simple hydrothermal combined with heat treatment reaction to synthesize a hierarchical nanostructured catalyst with abundant active sites and good mass transfer characteristics.

[0033] (3) The catalyst of the present invention has high activity and stability. In particular, the present invention's research shows that the nanocatalyst used, using a commercial 17.5M N2H4·H2O solution as the reaction fuel to construct a high-concentration N2H4·H2O hydrogen production system, can achieve a material-based actual hydrogen storage capacity of up to 6.2 wt%.

[0034] (4) The preparation method of the present invention has low raw material cost, is convenient to prepare, and is easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1These are the top view and front view of the surface of the Ni metal model and Ni-Cr alloy model (111) of Example 1.

[0036] Figure 2 Density of states maps of the two models of Example 1 (a); schematic diagram of the bonding between the catalyst surface and the adsorbate (b); and adsorption energy of the most stable configurations of Ni and Ni-Cr on the (111) surface (c).

[0037] Figure 3 The (111) surface adsorption configurations of the two models of Example 1 for N2H4 and the corresponding adsorption energies.

[0038] Figure 4 The hydrothermal sample and target catalyst Ni3Cr / NiO-CrO in Example 2 x XRD pattern of .

[0039] Figure 5 This is the SEM photo of the hydrothermal sample in Example 2.

[0040] Figure 6 TEM image of the hydrothermal sample in Example 2, and the inset is the corresponding selected area electron diffraction (SAED) spectrum.

[0041] Figure 7 The catalyst Ni3Cr / NiO-CrO obtained in Example 2 x SEM photos of .

[0042] Figure 8 The catalyst Ni3Cr / NiO-CrO obtained in Example 2 x TEM image, and the inset is the SAED spectrum.

[0043] Figure 9 The hydrothermal sample and target catalyst Ni3Cr / NiO-CrO in Example 2 x N2 adsorption-desorption isotherm (a) and corresponding pore size distribution curve (b).

[0044] Figure 10 The catalyst Ni3Cr / NiO-CrO obtained in Example 2 x HRTEM image (a), HAADF-STEM image (b) and corresponding element distribution maps (c&d). The inset in (b) is the line scan result shown in the figure.

[0045] Figure 11 These are the XPS results of the hydrothermal sample, target catalyst, and standard sample in Example 2, which are Ni 2p and Cr 2p, respectively.

[0046] Figure 12The catalyst Ni3Cr / NiO-CrO obtained in Example 2 x The cyclic kinetic curve of catalytic N2H4·H2O decomposition to produce hydrogen.

[0047] Figure 13 The catalyst Ni3Cr / NiO-CrO obtained in Example 2 x Kinetic curves of the catalytic decomposition of N₂H₄·H₂O at different test temperatures (a) and Arrhenius plots for determining activation energy (b). The inset in (b) shows the reaction rates at different test temperatures.

[0048] Figure 14 The catalyst Ni3Cr / NiO-CrO obtained in Example 2 x The top graph shows the reaction rate, and the bottom graph shows the time history of the fuel conversion rate.

[0049] Figure 15 The catalyst Ni3Cr / NiO-CrO obtained in Example 2 x Kinetic curve corresponding to the start-stop decomposition experiment of high concentration hydrazine.

[0050] Figure 16 The XRD pattern of the catalyst obtained in Example 3 is shown in FIG.

[0051] Figure 17 This is a TEM image of the catalyst obtained in Example 3. The inset in the left image is the corresponding SAED spectrum.

[0052] Figure 18 This is the cyclic kinetic curve of the catalyst obtained in Example 3 for catalytic decomposition of N2H4·H2O to produce hydrogen.

[0053] Figure 19 These are the XPS results of the catalysts obtained in Example 2, Example 3 and Example 4.

[0054] Figure 20 The XRD pattern of the catalyst obtained in Example 4 is shown in FIG.

[0055] Figure 21 This is a TEM image of the catalyst obtained in Example 4, and the inset in the left image is the corresponding SAED spectrum.

[0056] Figure 22 This is the cyclic kinetic curve of the catalyst obtained in Example 4 for catalytic decomposition of N2H4·H2O to produce hydrogen. DETAILED DESCRIPTION

[0057] The present invention will be described in further detail below with reference to the embodiments and accompanying drawings, but the embodiments and protection scope of the present invention are not limited thereto.

[0058] Example 1

[0059] Theoretical calculation study on the decomposition of N2H4 by Ni-Cr alloy:

[0060] Model construction: The properties of hydrazine adsorption on the Ni-Cr alloy surface were studied by density functional theory based on first principles and using the VASP package (VASP5.4.2). The interactions between inner-shell electrons and valence electrons were described using pseudopotentials of the plane wave basis set (PAW) and the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional based on the generalized gradient approximation (GGA), respectively. Ni(111) The surface is modeled using a (4×4) supercell, and the Ni-Cr(111) surface Then a (3×3) supercell model is used ( Figure 1 In the structural optimization, after fixing the bottom three layers, the remaining two layers and the adsorbates are released to allow them to fully relax until all forces acting on the unfixed atoms are less than The Brillouin zone is sampled using a 3×3×1k grid and the Z direction is added A dense 5 × 5 × 1 k-point grid was used for the electronic structure analysis.

[0061] Density of states (DOS) calculations were performed to gain a deeper understanding of the changes in electronic properties caused by the Ni-Cr alloy. The d-band centers of Ni metal and Ni-Cr alloy are -1.56 and -1.36 eV, respectively. Figure 2 According to the d-band theory, the electronic interaction between the valence state of the adsorbate and the d-state of the transition metal will form different bonding and antibonding states ( Figure 2 (b) The upward shift of the d-band center relative to the Fermi level means that the number of electrons in the antibonding state decreases, leading to an increase in the binding strength of the adsorbate to the transition metal surface.

[0062] According to the adsorption energy calculation of different adsorption configurations of N2H4 by two models, the most stable configuration ( Figure 3 ). For Ni metal, the adsorption energy of N2H4 when adsorbed on a single Ni atom and when adsorbed on two Ni atoms is extremely close (-1.30 vs -1.33 eV), so the probability of breaking the NN bond and the NH bond is almost equal. For Ni-Cr alloy, the bridging adsorption of N2H4 adsorbed on adjacent Ni-Cr atoms has the highest adsorption energy (-2.15 eV), which is about 35% to 45% higher than other configurations. It is worth noting that in this most energy-stable configuration, the adsorption of N2H4 on the Ni-Cr (111) surface is stronger than that on the Ni (111) surface ( Figure 2c). According to the principle of bond order conservation, the higher the adsorption strength, the higher the N2H4 dissociation activity, which means that Ni-Cr alloy may have higher activity as a catalyst for hydrogen production from hydrazine hydrate decomposition than pure metallic Ni catalyst.

[0063] Example 2

[0064] Ni3Cr / NiO-CrO x Catalyst preparation, structure and catalytic performance:

[0065] 1 mmol of Ni(NO3)2·6H2O, 1 mmol of Cr(NO3)3·9H2O and 4 mmol of urea were dissolved in 30 ml of deionized water to form a green transparent solution. Subsequently, the solution was stirred under magnetic stirring for 20 minutes, and then transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. After being heated at 120°C for 12 hours, it was naturally cooled to room temperature. After cooling to room temperature, the sample was collected and washed with deionized water and ethanol until the pH value reached neutral. The sample was vacuum dried at 60°C for 6 hours to obtain a hydrothermal sample. The hydrothermal sample was then heated to 300°C under H2 atmosphere at a heating rate of 5°C / min. After being heat treated at this temperature for 1 hour, it was cooled to room temperature to obtain the target catalyst Ni3Cr / NiO-CrO x The as-prepared catalyst samples were stored in a glove box filled with Ar atmosphere to minimize oxidation.

[0066] Phase / Structural Characterization of the Catalyst Obtained in This Example:

[0067] XRD analysis ( Figure 4 ) shows that the phase of the hydrothermal sample is Ni 5.2 Cr 2.8 (OH) 16 (CO3) 1.4 7.92H2O, corresponding to the typical Ni-Cr layered double hydroxide. The broad diffraction peak and diffuse scattering indicate that the hydrothermal sample (Ni,Cr)-LDH phase has a lower crystallinity and smaller grain size. SEM observation ( Figure 5 ) found that the hydrothermal sample is a random stacking of nano-layered structures with LDH characteristics. Figure 6 The results of TEM observation and SAED analysis confirmed that the nanocrystalline Ni 5.2 Cr 2.8 (OH) 16 (CO3) 1.4 · Formation of 7.92H2O.

[0068] After the hydrothermal sample was subjected to reduction heat treatment, SEM observation results showed that the sample retained the layered structure of the hydrothermal sample ( Figure 7). Compare the TEM images of the samples before and after reduction heat treatment ( Figure 8 ), it was found that many nanopores with a size of several nanometers were formed during the heat treatment. In agreement with this observation, the N2 adsorption isotherm measurement ( Figure 9 ) showed that the reduction heat treatment resulted in a more than two-fold increase in the specific surface area, and the pore size distribution curve expanded from micropores to the coexistence of nanopores and micropores.

[0069] XRD results ( Figure 4 ) shows Ni 5.2 Cr 2.8 (OH) 16 (CO3) 1.4 The diffraction peak corresponding to 7.92H2O completely disappears, and the new diffraction peak corresponds to the nanocrystalline NiO phase. Due to the small grain size of the Ni-Cr alloy phase, the corresponding Ni-Cr alloy phase cannot be observed in this XRD result.

[0070] TEM photos ( Figure 8 ) inset, the SAED pattern of the reduction heat-treated sample has a series of concentric diffraction rings that closely match the crystal planes of the Ni3Cr phase and the NiO phase. SAED analysis and HRTEM results ( Figure 10 (a) in the figure confirms the existence of Ni3Cr phase and NiO phase, which is consistent with the XRD results.

[0071] In addition, HRTEM observations revealed the presence of a large number of amorphous regions in the target sample, which can be inferred to be Cr oxides based on the composition of the precursor and the temperature of heat treatment reduction.

[0072] HAADF-STEM observation combined with EDS ( Figure 10 The analysis of b, c, and d) in Figure 3 confirms the uniform distribution of Ni and Cr elements, and the line scan results show that the Ni and Cr signals have the characteristics of synchronous changes. These results together confirm the compositional uniformity of the Ni-Cr alloy.

[0073] XPS analysis ( Figure 11 ) The results show that the Ni and Cr elements in the hydrothermal sample are in oxidized state, which is consistent with the XRD analysis results. After the reduction heat treatment, the sample shows a strong metallic Ni 0 signal, while Cr mainly remained in the oxidized state, and only weak Cr was detected. 0 The comprehensive analysis of XRD, SAED and HRTEM results shows that the Cr oxide in the sample exists in an amorphous form. 0 The binding energy of Cr 0 A negative shift occurred relative to the standard sample, further confirming the formation of Ni-Cr alloy.

[0074] The target catalyst Ni3Cr / NiO-CrO obtained in this example x Catalytic performance test:

[0075] (1) Ni3Cr / NiO-CrO obtained in this embodiment x The catalyst (25 mg) was tested for the hydrogen production performance of hydrazine hydrate decomposition under the test conditions of a reaction solution volume of 2 mL, a hydrazine hydrate concentration of 0.5 M, a sodium hydroxide concentration of 2.0 M, and a reaction temperature of 50 ° C. Figure 12 The results show that Ni3Cr / NiO-CrO x The catalyst has excellent activity, with a first-cycle reaction rate of 39.8h -1 , the selectivity is 100%. The test of the cyclic stability of the catalyst found that the catalyst has a very high cyclic stability. After 10 cycles of testing, the selectivity remains unchanged and the total activity decay is less than 4%. This high stability is at an advanced level among existing hydrazine hydrate catalysts. In addition, the reaction temperature dependence of the catalyst was further studied. Figure 13 As shown in a, increasing the reaction temperature leads to an increase in the catalytic decomposition rate of N2H4·H2O. When the reaction temperature increases from 30℃ to 50℃, the selectivity increases from 75% to 100%. Further increasing the reaction temperature will not affect the H2 selectivity. According to the temperature-dependent reaction rate, it is calculated that Ni3Cr / NiO-CrO x The apparent activation energy for the catalytic decomposition of N2H4·H2O is 53.1 kJ / mol ( Figure 13 b), which is comparable to reported non-precious metal catalysts.

[0076] (2) Using the Ni3Cr / NiO-CrO obtained in this example x A high concentration N2H4·H2O hydrogen production system was constructed using a catalyst, and the hydrogen production performance of this high hydrogen storage capacity system was studied. Commercial N2H4·H2O solution and NaOH aqueous solution were mixed to form a reaction solution of 17.5M N2H4·H2O and 2.0M NaOH. Figure 14 As shown, when 400 mg of the catalyst was added to the reaction solution, N₂H₄·H₂O rapidly decomposed to produce gas. The reaction rate quickly reached 150 mL(N₂+H₂) / min within approximately 1 minute and remained between 150 and 90 mL(N₂+H₂) / min for 100 minutes. Based on the total amount of gas produced, H₂ selectivity was 100%, and the system's hydrogen capacity reached 6.2 wt%. This laid the foundation for the practical application of the N₂H₄·H₂O hydrogen production system.

[0077] (3) Using the Ni3Cr / NiO-CrO obtained in this example xCatalyst, N2H4·H2O solution was periodically injected into the reactor containing the catalyst to test the dynamic response experiment of the N2H4·H2O-based system, such as Figure 15 As shown, in each start-stop cycle, the reaction rate reaches its peak within 1 minute, and the reaction is completed within 16-18 minutes. Catalysts with high hydrogen storage capacity, fast dynamic response, and stable hydrogen production performance lay the foundation for the practical application of N2H4·H2O-based hydrogen source systems.

[0078] Example 3

[0079] Preparation of the catalyst obtained in this example:

[0080] In the synthesis method of this embodiment, only the reduction heat treatment temperature in the embodiment is changed to 250°C, and the other preparation conditions are the same as those in Example 2. The obtained catalyst is recorded as Ni / NiO-CrO x .

[0081] Phase / Structural Characterization of the Catalyst Obtained in This Example:

[0082] The XRD pattern of the reduction heat-treated sample obtained in this embodiment is as follows: Figure 16 As shown. According to XRD analysis, the diffraction peaks correspond to Ni metal and NiO nanocrystals. Combined with TEM, SAED and XPS results, it can be seen that ( Figure 17 and Figure 18 ), the catalyst obtained in this embodiment is dispersed in NiO nanocrystals and amorphous CrO x The sample also has a nanoporous layered structure, which is very similar to the catalyst morphology of Example 2. Therefore, the only major difference between the catalysts prepared in this example and Example 2 is the conversion from Ni to Ni3Cr. Therefore, the catalyst obtained in this example is recorded as Ni / NiO-CrO x .

[0083] The catalyst Ni / NiO-CrO obtained in this example x Catalytic performance test:

[0084] The Ni / NiO-CrO obtained in this example x The catalyst (25 mg) was tested for the hydrogen production performance of hydrazine hydrate decomposition under the test conditions of a reaction solution volume of 2 mL, a hydrazine hydrate concentration of 0.5 M, a sodium hydroxide concentration of 2.0 M, and a reaction temperature of 50 ° C. Figure 19 The results show that the reaction rate is 7.5h -1 , the selectivity was 46%. Compared with the catalyst obtained in Example 1, the activity was reduced by nearly 5 times, and the H2 selectivity was reduced to 1 / 2, indicating that Ni-Cr alloying had a significant effect on the catalytic performance.

[0085] Example 4

[0086] Preparation of the catalyst obtained in this example:

[0087] In the synthesis method of this embodiment, only the reduction heat treatment temperature in the embodiment is changed to 350°C, and the other preparation conditions are the same as those in Example 1. The obtained catalyst is recorded as Ni(Ni3Cr) / CrO x .

[0088] Phase / Structural Characterization of the Catalyst Obtained in This Example:

[0089] The XRD pattern of the reduction heat-treated sample obtained in this embodiment is as follows: Figure 20 As shown. According to XRD analysis, most of NiO is completely reduced to metallic Ni or Ni3Cr alloy. Further analysis of XPS results ( Figure 18 ) It can be seen that the Ni content of the catalyst obtained in this embodiment is 0 The signal is significantly enhanced compared with Example 2, but Cr 0 The signal is only slightly stronger than that of Example 2, which indicates that Ni3Cr alloy may coexist with Ni metal. Figure 21 ) Comprehensive analysis shows that the catalyst obtained in this embodiment is a dispersed amorphous CrO x The Ni3Cr and Ni nanoparticles in the matrix are composed of Ni3Cr and Ni nanoparticles. The NiO diffraction ring in the SAED can be attributed to air oxidation during sample preparation. Therefore, the catalyst obtained in this example is recorded as Ni(Ni3Cr) / CrO x .

[0090] The catalyst Ni(Ni3Cr) / CrO obtained in this example x Catalytic performance test:

[0091] The Ni / NiO-CrO obtained in this example x The catalyst (25 mg) was tested for the hydrogen production performance of hydrazine hydrate decomposition under the test conditions of a reaction solution volume of 2 mL, a hydrazine hydrate concentration of 0.5 M, a sodium hydroxide concentration of 2.0 M, and a reaction temperature of 50 ° C. Figure 22 The results show that the reaction rate is 9.7h -1 , the selectivity is 87%. Compared with the catalyst obtained in Example 2, the catalytic performance of the catalyst obtained in this example should be regarded as the result of the combined effect of Ni metal and Ni3Cr alloy. Specifically, the decrease in activity is mainly due to the grain growth and particle aggregation of Ni3Cr alloy at high temperature ( Figure 21 The decrease in H2 selectivity is attributed to the participation of the metal element Ni in the catalytic decomposition of N2H4·H2O, which shows a lower selectivity.

[0092] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a non-precious metal hydrazine hydrate decomposition hydrogen production catalyst, characterized in that: The following steps are involved: The soluble Ni 2+ Salt, soluble Cr 3+ The salt and the precipitant are hydrothermally reacted in water to obtain a hydrothermal sample, which is heat treated at 250-350° C. under a reducing atmosphere to obtain a non-precious metal hydrazine hydrate decomposition catalyst for hydrogen production.

2. The preparation method according to claim 1, characterized in that: The soluble Ni 2+ The salt is nickel nitrate, the soluble Cr 3+ The salt is chromium nitrate.

3. The preparation method according to claim 1, characterized in that: Ni 2+ The concentration of Cr is 0.03~0.1M; 3+ The concentration is 0.03~0.1M.

4. The preparation method according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 90 to 150° C., and the time of the hydrothermal reaction is 2 to 16 hours.

5. The preparation method according to claim 1, characterized in that: The reducing atmosphere is hydrogen; the heat treatment time is 1 to 2 hours; and the heat treatment temperature is 300°C.

6. The preparation method according to claim 1, characterized in that: The concentration of the precipitant is 0.1 to 0.2 M; The precipitant includes at least one of sodium hydroxide, sodium carbonate, tetramethylammonium hydroxide and urea.

7. The preparation method according to claim 1, characterized in that: After the hydrothermal reaction, the sample is washed and dried to obtain a hydrothermal state sample.

8. The preparation method according to claim 7, characterized in that: The drying temperature is 40-60° C., and the drying time is 6-12 hours.

9. A non-precious metal hydrazine hydrate decomposition hydrogen production catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the non-precious metal hydrazine hydrate decomposition hydrogen production catalyst according to claim 9 in hydrazine hydrate decomposition hydrogen production.

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