Rare earth element doped hydrogen evolution electrocatalyst, preparation method and application thereof

Abstract

The application discloses a rare earth element doped hydrogen evolution electrocatalyst and a preparation method and application thereof. The rare earth element doped hydrogen evolution electrocatalyst comprises a rare earth element doped nickel oxide as a carrier and ruthenium atoms anchored on the carrier. The rare earth element doped hydrogen evolution electrocatalyst provided by the application enhances the adsorption of hydroxyl by doping NiO with oxygenophilic rare earth elements, the rare earth element / NiO carrier promotes the hydrogen conversion on the Ru surface, the rare earth element / NiO and Ru have a clear synergistic effect, and the water dissociation is jointly promoted, so that the rare earth element doped hydrogen evolution electrocatalyst has very high catalytic activity in the alkaline HER and provides a new idea for accelerating the kinetics of the alkaline HER. In the alkaline HER test, the rare earth element doped hydrogen evolution electrocatalyst provided by the application only needs an overpotential of 38 mV to reach a current density of 10 mA cm ‑2 ; and after 50 h of stability test, the overpotential does not appear to be attenuated.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a novel hydrogen evolution electrocatalyst, in particular to a rare earth element doped hydrogen evolution electrocatalyst and a preparation method and application thereof, and belongs to the technical field of nanomaterial preparation and application. BACKGROUND

[0002] Reducing the consumption of fossil energy and developing clean and renewable new energy have become strategic keys. Hydrogen energy has become a strong driving force for future low-carbon economy due to its high energy density, high calorific value and zero emission and many other advantages. The development of traditional coal hydrogen production and methane reforming hydrogen production is limited by high carbon emission restrictions. In comparison, water electrolysis hydrogen production (HER) has many advantages such as high efficiency and environmental protection, thereby providing a technical route for producing high-purity hydrogen.

[0003] Water electrolysis under alkaline conditions is a large-scale hydrogen production technology that can be widely applied. However, in the actual water electrolysis process, the slow reaction kinetics caused by insufficient proton supply seriously increases the additional energy consumption. The specific reaction formula is as follows:

[0004] Vomler step: H2O + e - → H* + OH -

[0005] Heyrovsky step: H* + H2O → OH- + H2

[0006] Tafel step: H* + H* → H2

[0007] In the above formula, it can be found that in the alkaline environment, the protons are derived from the dissociation of water (Vomler step). In order to accelerate the water electrolysis hydrogen production kinetics in the alkaline medium, it is crucial to reasonably design and prepare an alkaline hydrogen evolution electrocatalyst. At present, the material with the best performance of alkaline hydrogen evolution electrocatalyst is still a noble metal-containing electrocatalyst, and the high price limits its potential for large-scale application. If non-noble metals and noble metals are combined through heteroengineering, the amount of noble metals can be greatly reduced, thereby improving the mass activity of noble metals in the electrocatalyst.

[0008] Among many alkaline hydrogen evolution electrocatalysts, ruthenium (Ru) based catalysts have high water dissociation capacity and appropriate Ru-H bond strength, and have been widely concerned by researchers. Through heteroengineering, metal-support type catalysts can improve the efficiency of the catalysts. Lin et al. loaded Ru single atoms on WC xOn the other hand, the adsorption of hydroxyl on the carbide support and the adsorption of hydrogen intermediates on the single-atom Ru site are balanced, and the basic HER activity is enhanced. Qin et al. loaded Ru clusters on a vacancy-rich amorphous CeO2, and this unique heterostructure accelerated the water dissociation rate and hydrogen desorption kinetics, and the metal support synergistically improved the basic HER activity.

[0009] Loading Ru on a nickel oxide (NiO) electrocatalyst can promote the conversion of hydrogen on the Ru surface, while greatly reducing the use of Ru. However, NiO also has disadvantages, such as insufficient adsorption of OH-, which leads to a slow dissociation rate of H2O molecules and a low proton concentration on the Ru surface, directly leading to a decrease in hydrogen evolution reaction kinetics, so NiO still needs to be modified to improve the electrocatalytic performance. SUMMARY

[0010] The main purpose of the present application is to provide a rare earth element doped hydrogen evolution electrocatalyst and a preparation method thereof to overcome the shortcomings of the prior art.

[0011] Another purpose of the present application is to provide the application of the rare earth element doped hydrogen evolution electrocatalyst.

[0012] To achieve the above-mentioned purposes, the technical scheme adopted by the present application comprises:

[0013] The rare earth element doped hydrogen evolution electrocatalyst provided by the embodiments of the present application comprises: a rare earth element doped nickel oxide as a carrier, and a ruthenium atom anchored on the carrier.

[0014] The embodiments of the present application also provide a preparation method of a rare earth element doped hydrogen evolution electrocatalyst, which comprises:

[0015] Mixing a nickel source, a rare earth element source, a MOF precursor and an organic solvent to form a mixed solution; then adding water and alcohol to obtain a hydrothermal reaction system;

[0016] Making the hydrothermal reaction system undergo a first hydrothermal reaction to obtain a rare earth element / Ni-MOF precursor material;

[0017] Mixing the rare earth element / Ni-MOF precursor material with water to perform a second hydrothermal reaction to obtain a rare earth element / NiO material;

[0018] Making the rare earth element / NiO material fully contact with a ruthenium source and adsorb, and then performing freeze-drying to obtain a rare earth element / NiO-Ru precursor material;

[0019] Performing annealing treatment on the rare earth element / NiO-Ru precursor material in a protective atmosphere to obtain a rare earth element / NiO material anchored with a ruthenium atom, i.e. a rare earth element doped hydrogen evolution electrocatalyst.

[0020] The application also provides a rare earth element doped hydrogen evolution electrocatalyst prepared by the preparation method.

[0021] The application also provides an application of the rare earth element doped hydrogen evolution electrocatalyst in a water electrolysis hydrogen production reaction.

[0022] Compared with the prior art, the application has the following advantages and beneficial effects:

[0023] The rare earth element doped hydrogen evolution electrocatalyst provided by the application enhances the adsorption of hydroxyl groups by doping NiO with oxygenophilic rare earth elements, the rare earth element / NiO carrier promotes the hydrogen conversion on the Ru surface, the rare earth element / NiO and Ru have a clear synergistic effect, and the water dissociation is jointly promoted, which reflects very high catalytic activity in the alkaline HER and provides a new idea for accelerating the kinetics of the alkaline HER reaction. In the alkaline HER test, the rare earth element doped hydrogen evolution electrocatalyst provided by the application only needs an overpotential of 38 mV to achieve a current density of 10 mA cm-2; after 50 h of stability test, the overpotential does not decay. -2 BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings obtained from these drawings without creative labor are still within the scope of the application.

[0025] Figure 1 It is a preparation flowchart of a rare earth element doped hydrogen evolution electrocatalyst in the embodiment 1 of the application;

[0026] Figure 2a , Figure 2b It is a scanning electron microscope image of the NiO-Ru@NF prepared in the comparative example 3 of the application;

[0027] Figure 2c , Figure 2d It is a scanning electron microscope image of the Ce / NiO-Ru@NF prepared in the embodiment 1 of the application;

[0028] Figure 3 It is an XPS spectrum diagram of the Ce / NiO-Ru@NF prepared in the embodiment 1 of the application;

[0029] Figure 4a It is an LSV curve diagram of the NiO, Ce / NiO, NiO-Ru, Ce / NiO-Ru, and commercial Pt / C catalysts;

[0030] ​Figure 4b Tafel slope curve of NiO, Ce / NiO, NiO-Ru, Ce / NiO-Ru, and commercial Pt / C catalysts;

[0031] Figure 4c Catalyst performance comparison chart of NiO-Ru, Ce / NiO-Ru, and commercial Pt / C catalysts;

[0032] Figure 4d Catalyst chronopotentiometric curve of Ce / NiO-Ru prepared in Example 1 of the present application;

[0033] Figure 5a and Figure 5b Scanning electron microscope image of the catalyst prepared in Example 2 of the present application;

[0034] Figure 6a and Figure 6b Scanning electron microscope image of the catalyst prepared in Example 3 of the present application;

[0035] Figure 7a and Figure 7b Scanning electron microscope image of the catalyst prepared in Example 4 of the present application;

[0036] Figure 8a and Figure 8b Scanning electron microscope image of the catalyst prepared in Example 5 of the present application;

[0037] Figure 9a LSV curve of the catalysts prepared in Examples 1, 2, and 3 of the present application;

[0038] Figure 9b LSV curve of the catalysts prepared in Examples 1, 4, and 5 of the present application. DETAILED DESCRIPTION

[0039] In the prior art, there have been many studies on improving the electrocatalytic hydrogen evolution performance by modifying the oxide carrier. Among them, doping is a relatively common way. In order to solve the problem of insufficient OH-adsorption of NiO, the oxide is doped with oxygenophilic rare earth elements (such as La, Ce, Pr, Lu, Dy, etc.), which can enhance the adsorption of OH- and thus promote the water dissociation rate. On the other hand, after doping the NiO carrier, the NiO lattice is distorted, which leads to different changes in the combination of the oxide carrier surface and Ru, and to some extent, promotes the conversion of hydrogen on its surface. At present, there are few reports on improving the electrocatalytic hydrogen evolution performance by using this strategy.

[0040] In addition, the catalyst material can be grown in-situ on the nickel foam framework very uniformly. The in-situ growth on the nickel foam can improve the conductivity to ensure that the catalyst is connected when the minimum existing unit exists, and ensure good electron conduction efficiency. At the same time, the growth of the catalyst on the nickel foam electrode can ensure the utilization rate of the unit area of the electrocatalyst as much as possible due to the porous characteristics of the nickel foam electrode.

[0041] In order to improve the electrocatalytic HER efficiency of the metal-support type catalyst in the alkaline medium, the present application proposes to dope the cheap and extremely easy-to-prepare NiO with oxygenophilic rare earth elements, and then anchor Ru atoms on the oxide carrier to prepare a new high-performance HER electrocatalyst.

[0042] The technical scheme, implementation process and principles thereof will be further explained as follows.

[0043] One aspect of the embodiment of the present application provides a rare earth element doped hydrogen evolution electrocatalyst, which comprises: a rare earth element doped nickel oxide as a carrier, and Ru atoms anchored on the carrier.

[0044] In some embodiments, the rare earth element can include any one of cerium (Ce), lanthanum (La), praseodymium (Pr) and the like, but is not limited thereto.

[0045] In some embodiments, the content of the rare earth element in the rare earth element doped hydrogen evolution electrocatalyst is 2.5-7.5wt%.

[0046] In some embodiments, the rare earth element doped hydrogen evolution electrocatalyst has a linear nanosheet structure, and the linear nanosheets are stacked with each other.

[0047] Further, the length of the linear nanosheet is 5-20μm, the width is 1-3μm, and the thickness is 0.5μm or less.

[0048] Another aspect of the embodiment of the present application provides a preparation method of a rare earth element doped hydrogen evolution electrocatalyst, which proposes to dope the cheap and extremely easy-to-prepare NiO with oxygenophilic rare earth elements, and then anchor Ru atoms on the oxide carrier to prepare a new high-performance HER electrocatalyst rare earth element / NiO-Ru.

[0049] In some embodiments, the preparation method of the rare earth element doped hydrogen evolution electrocatalyst comprises:

[0050] The nickel source, the rare earth element source, the MOF precursor and the organic solvent are mixed to form a mixed solution; then water and alcohol are added to obtain a hydrothermal reaction system;

[0051] carrying out a first hydrothermal reaction on the hydrothermal reaction system to obtain a rare earth element / Ni-MOF precursor material;

[0052] carrying out a second hydrothermal reaction on the rare earth element / Ni-MOF precursor material mixed with water to obtain a rare earth element / NiO material;

[0053] carrying out a second hydrothermal reaction on the rare earth element / Ni-MOF precursor material mixed with water to obtain a rare earth element / NiO material;

[0054] carrying out a second hydrothermal reaction on the rare earth element / Ni-MOF precursor material mixed with water to obtain a rare earth element / NiO material;

[0055] In some embodiments, the rare earth element in the rare earth element source can include at least any one of cerium (Ce), lanthanum (La), praseodymium (Pr), etc., but is not limited thereto.

[0056] In some embodiments, the rare earth element source can be any one of cerium nitrate (Ce(NO3)3), lanthanum nitrate (La(NO3)3), praseodymium nitrate (Pr(NO3)3), etc., and is preferably cerium nitrate, but is not limited thereto.

[0057] Further, the nickel source can be NiCl2, but is not limited thereto.

[0058] In some embodiments, the molar ratio of the nickel source, the rare earth element source, and the MOF precursor is 1:(0.025-0.075):3.

[0059] Further, the MOF precursor can be terephthalic acid (TPA), but is not limited thereto.

[0060] In some embodiments, the organic solvent can be N,N-dimethylformamide (DMF), but is not limited thereto.

[0061] In some embodiments, the molar volume ratio of the nickel source and the organic solvent is 0.5-2 mmol: 17.5-70 mL.

[0062] Further, the volume ratio of the organic solvent, water, and alcohol is 17.5-70: 1.25-5: 1.25-5.

[0063] Further, the alcohol can be ethanol, but is not limited thereto.

[0064] In some more preferred embodiments, the preparation method comprises: adding water and alcohol after stirring the mixed solution at room temperature for 30 min to 2 h, and continuing to stir to obtain a hydrothermal reaction system.

[0065] In some embodiments, the first hydrothermal reaction has a temperature of 100 to 140°C and a time of 12 to 24 h.

[0066] In some embodiments, the second hydrothermal reaction has a temperature of 160 to 200°C and a time of 5.5 to 6.5 h.

[0067] In some embodiments, the ruthenium source can be RuCl3, but is not limited thereto.

[0068] In some more preferred embodiments, the preparation method comprises: immersing the rare earth element / NiO material in a ruthenium source aqueous solution and performing adsorption.

[0069] Further, the immersion time is 0.5 h to 4 h.

[0070] Further, the concentration of the ruthenium source aqueous solution is 1 to 5 mg mL -1 .

[0071] In some embodiments, the freeze-drying has a temperature of -80 to -40°C and a time of 18 to 48 h.

[0072] In some embodiments, the annealing treatment has a temperature of 250 to 400°C and a time of 1 to 4 h.

[0073] Further, the protective atmosphere includes an argon atmosphere, but is not limited thereto.

[0074] In some more specific embodiments of the present application, the inventors believe that when the water decomposition HER half-reaction is carried out in an alkaline medium, a strong interaction occurs between the support composed of a rare earth element-doped nickel oxide and the anchored ruthenium. Taking Ce as an example of the rare earth element, the preparation method of the rare earth element-doped hydrogen evolution electrocatalyst (HER catalyst) is as follows: the Ru site adsorbs hydrogen, the Ce / NiO support adsorbs hydroxyl, and then H-O…H is cracked into *H and *OH, so that the vomler step is accelerated. A large amount of H surrounds the Ru site, causing a local proton-rich environment. In this case, the proton availability of the Ru site is greatly improved, thereby accelerating the conversion of H* to H2.

[0075] The preparation method of the HER catalyst comprises the following steps:

[0076] (1) Commercially available foamed nickel was sequentially cleaned in acetone, ethanol and deionized water, and then immersed in 1M hydrochloric acid, and then cleaned in deionized water by ultrasonic for 3 times, and finally dried in a vacuum oven at 60°C for standby.

[0077] (2) A certain amount of NiCl2·6H2O, Ce(NO3)3·6H2O and terephthalic acid (TPA) were sequentially weighed and added into N,N-dimethylformamide (DMF) to obtain a mixed solution, and then a certain amount of water and ethanol were added and stirred at room temperature for a certain time; after the mixture was uniformly mixed, the mixed solution was transferred into the inner liner of a PTFE reaction kettle, and a piece of clean foamed nickel was put in; after the reaction kettle was sealed, the hydrothermal reaction was carried out in a hydrothermal oven, and then the sample was naturally cooled to room temperature; after the sample was taken out, it was washed with deionized water and ethanol alternately and then dried in a vacuum oven at 60°C for standby.

[0078] (3) The foamed nickel with precursors prepared in step (2) was put into the inner liner of a reaction kettle containing deionized water, and the hydrothermal reaction was carried out after the reaction kettle was sealed; after the reaction was completed, the sample was taken out, washed with deionized water and ethanol alternately, and then dried in a vacuum oven at 60°C for standby.

[0079] (4) The sample in step (3) was placed in a RuCl3·xH2O solution with a certain concentration and soaked for 2h for adsorption; after being taken out, it was freeze-dried.

[0080] (5) The sample after freeze-drying in step (4) was annealed in a tube furnace and naturally cooled to room temperature, and then the annealed sample was washed with deionized water for 3 times and dried in a vacuum oven at 60°C for standby, thereby preparing the final HER catalyst.

[0081] In the above step (1), the hydrochloric acid soaking time was controlled to be 10 min.

[0082] In the above step (2), the amounts of NiCl2·6H2O, Ce(NO3)3·6H2O and TPA were 1 mmol, 0.05 mmol and 3 mmol respectively, the amount of DMF was 35 mL, and the amounts of water and ethanol were 2.5 mL.

[0083] In the above step (3), the amount of deionized water added was 40 mL.

[0084] In the above step (4), the concentration of the RuCl3·xH2O solution was 1-5 mg / mL -1 , preferably 3 mg / mL -1 .

[0085] In the above step (5), the annealing conditions were 250-400°C for 1-4h in an argon atmosphere.

[0086] Another aspect of the embodiments of the present application also provides the rare earth element doped hydrogen evolution electrocatalyst prepared by the aforementioned preparation method.

[0087] In summary, the HER catalyst Ce / NiO-Ru prepared in the present application has high catalytic activity in alkaline HER, and provides a new idea for accelerating the kinetics of alkaline HER.

[0088] In some embodiments, in the alkaline HER test, the rare earth element doped hydrogen evolution electrocatalyst (Ce / NiO-Ru) only needs an overpotential of 38 mV to achieve a current density of 10 mA cm-2, and the Tafel slope is 58 mV / dec, indicating a faster reaction kinetics. In the stability test, the performance of the Ce / NiO-Ru catalyst does not decay after 50 h of continuous work, showing good stability. -2 In some embodiments, in the alkaline HER test, the rare earth element doped hydrogen evolution electrocatalyst (Ce / NiO-Ru) only needs an overpotential of 38 mV to achieve a current density of 10 mA cm-2, and the Tafel slope is 58 mV / dec, indicating a faster reaction kinetics. In the stability test, the performance of the Ce / NiO-Ru catalyst does not decay after 50 h of continuous work, showing good stability.

[0089] Another aspect of the embodiments of the present application also provides the application of the aforementioned rare earth element doped hydrogen evolution electrocatalyst in the water electrolysis hydrogen production reaction.

[0090] In order to further understand the present application, the technical solutions of the present application will be described in detail below in conjunction with the embodiments and drawings. In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the scope of the present application, therefore the present application is not limited to the specific embodiments disclosed below. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0091] Unless otherwise specified, the raw materials and reagents in the embodiments of the present application are purchased through commercial channels.

[0092] Example 1

[0093] The synthesis process of the Ce / NiO-Ru@NF catalyst in this embodiment is shown in Figure 1 2+ , Ce 3+ ​Ce doped Ni-MOF (Ce / Ni-MOF@NF) was obtained by hydrothermal reaction of TPA and TPA in DMF solvent; then Ce / Ni-MOF@NF was pyrolyzed in aqueous solvent to obtain Ce / NiO@NF; finally, Ce / NiO@NF was immersed in RuCl3 solution and annealed in a tube furnace to obtain Ce / NiO-Ru@NF. Specifically, the following steps are included:

[0094] (1) NF cleaning

[0095] Commercial NF was sequentially cleaned in acetone, ethanol and deionized water, and then immersed in 1M hydrochloric acid for 10 min, followed by repeated ultrasonic cleaning with deionized water for 3 times, and finally placed in a 60°C vacuum oven for drying for standby.

[0096] (2) Preparation of Ce / Ni-MOF@NF

[0097] 1 mmol of NiCl2·6H2O, 0.05 mmol of Ce(NO3)3·6H2O and 3 mmol of TPA were sequentially weighed and added to a 35 mL DMF containing solution, which was stirred at room temperature for 30 min, then 2.5 mL of water and 2.5 mL of ethanol were added and the stirring was continued; after the mixture was mixed uniformly, it was transferred to the inner liner of a PTFE reaction kettle, and a clean NF was taken out; after the reaction kettle was sealed, a 125°C hydrothermal reaction was carried out in the hydrothermal box for 24 h, and after the reaction was completed, it was naturally cooled to room temperature; after the sample was taken out, it was washed with deionized water and ethanol alternately and then placed in a 60°C vacuum oven for drying for standby.

[0098] (3) Preparation of Ce / NiO@NF

[0099] The Ce / Ni-MOF@NF prepared in step (2) was placed in a reaction kettle liner containing 40 mL of deionized water, and after the reaction kettle was sealed, a hydrothermal reaction was carried out at 180°C for 6 h; after the reaction was completed, the sample was taken out, washed with deionized water and ethanol alternately and then placed in a 60°C vacuum oven for drying for standby.

[0100] (4) Preparation of Ce / NiO-Ru@NF precursor

[0101] The sample in step (3) was placed in a 3 mg mL -1 solution of RuCl3·xH2O and soaked for 2 h for adsorption; after taking out, it was freeze-dried at -40°C for 24 h.

[0102] (5) Preparation of Ce / NiO-Ru@NF

[0103] The sample of step (4) was annealed in a tube furnace under argon atmosphere at 350℃ for 2h and naturally cooled to room temperature. The sample after annealing was washed with deionized water for three times and then dried in a vacuum oven at 60℃ for standby, thus the final HER catalyst Ce / NiO-Ru was prepared.

[0104] Example 2

[0105] (1) NF cleaning

[0106] The commercial NF was sequentially cleaned in acetone, ethanol and deionized water under ultrasonic. Then it was immersed in 1M hydrochloric acid for 10min and cleaned with deionized water under ultrasonic for three times. Finally, it was dried in a vacuum oven at 60℃ for standby.

[0107] (2) Preparation of Ce / Ni-MOF@NF

[0108] 1mmol NiCl2·6H2O, 0.025mmol Ce(NO3)3·6H2O and 3mmol TPA were sequentially weighed and added into a 35mL DMF solution. After stirring at room temperature for 30min, 2.5mL water and 2.5mL ethanol were added and the stirring was continued. After the mixture was sufficiently mixed, it was transferred into a PTFE inner liner of a reactor and a clean NF was put in. After the reactor was sealed, a 24h hydrothermal reaction was carried out at 125℃ in a hydrothermal oven. After the reaction, the sample was naturally cooled to room temperature. After washing with deionized water and ethanol, the sample was dried in a vacuum oven at 60℃ for standby.

[0109] (3) Preparation of Ce / NiO@NF

[0110] The Ce / Ni-MOF@NF prepared in step (2) was put into a reactor inner liner containing 40mL deionized water. After the reactor was sealed, a 6h hydrothermal reaction was carried out at 180℃. After the reaction, the sample was washed with deionized water and ethanol and dried in a vacuum oven at 60℃ for standby.

[0111] (4) Preparation of Ce / NiO-Ru@NF precursor

[0112] The sample in step (3) was immersed in a 3mg mL -1 solution of RuCl3·xH2O for 2h for adsorption. After taking out, it was freeze-dried at -40℃ for 24h.

[0113] (5) Preparation of Ce / NiO-Ru@NF

[0114] The sample of step (4) was annealed in a tube furnace under argon atmosphere at 350℃ for 2h and naturally cooled to room temperature. The sample after annealing was washed with deionized water for three times and then dried in a vacuum oven at 60℃ for standby, thus the final HER catalyst Ce / NiO-Ru was prepared.

[0115] Example 3

[0116] (1) NF cleaning

[0117] The commercial NF was sequentially cleaned in acetone, ethanol and deionized water under ultrasonic. Then it was immersed in 1M acid for 10min and cleaned in deionized water under ultrasonic for three times. Finally, it was dried in a vacuum oven at 60℃ for standby.

[0118] (2) Preparation of Ce / Ni-MOF@NF

[0119] 1mmol NiCl2·6H2O, 0.075mmol Ce(NO3)3·6H2O and 3mmol TPA were sequentially weighed and added into a 35mL DMF solution. After stirring at room temperature for 30min, 2.5mL water and 2.5mL ethanol were added and the stirring was continued. After the mixture was sufficiently mixed, it was transferred into a PTFE inner liner of a reactor and a clean NF was put in. After the reactor was sealed, a 24h hydrothermal reaction was carried out at 125℃ in a hydrothermal oven. After the reaction, the sample was naturally cooled to room temperature. After washing with deionized water and ethanol, the sample was dried in a vacuum oven at 60℃ for standby.

[0120] (3) Preparation of Ce / NiO@NF

[0121] The Ce / Ni-MOF@NF prepared in step (2) was put into a reactor inner liner containing 40mL deionized water. After the reactor was sealed, a 6h hydrothermal reaction was carried out at 180℃. After the reaction, the sample was washed with deionized water and ethanol and dried in a vacuum oven at 60℃ for standby.

[0122] (4) Preparation of Ce / NiO-Ru@NF precursor

[0123] The sample in step (3) was immersed in a 3mg mL -1 solution of RuCl3·xH2O for 2h for adsorption. After taking out, it was freeze-dried at -40℃ for 24h.

[0124] (5) Preparation of Ce / NiO-Ru@NF

[0125] The sample of step (4) was annealed in a tube furnace at 350°C for 2h under argon atmosphere and cooled to room temperature naturally. The sample was washed with deionized water for three times and dried in a vacuum oven at 60°C for later use, namely, the final HER catalyst Ce / NiO-Ru was prepared.

[0126] Example 4

[0127] (1) NF cleaning

[0128] The commercial NF was sequentially cleaned in acetone, ethanol and deionized water by ultrasonic cleaning. Then, the NF was immersed in 1M hydrochloric acid for 10min and cleaned in deionized water by ultrasonic cleaning for three times. Finally, the NF was dried in a vacuum oven at 60°C for later use.

[0129] (2) Preparation of La / Ni-MOF@NF

[0130] 1mmol of NiCl2·6H2O, 0.05mmol of La(NO3)3·6H2O and 3mmol of TPA were sequentially weighed and added to a container containing 70mL of DMF to obtain a mixed solution. After stirring at room temperature for 2h, 2.5mL of water and 2.5mL of ethanol were added for continuous stirring. After the mixture was sufficiently mixed, the mixed solution was transferred to a PTFE inner liner of a reaction kettle, and a clean NF was taken out. After the reaction kettle was sealed, a 100°C hydrothermal reaction was carried out in a hydrothermal box for 24h. After the reaction was completed, the sample was naturally cooled to room temperature. After the sample was taken out, it was washed with deionized water and ethanol alternately and dried in a vacuum oven at 60°C for later use.

[0131] (3) Preparation of La / NiO@NF

[0132] The La / Ni-MOF@NF prepared in step (2) was placed in a reaction kettle inner liner containing 40mL of deionized water. After the reaction kettle was sealed, a hydrothermal reaction was carried out at 200°C for 5.5h. After the reaction was completed, the sample was taken out, washed with deionized water and ethanol alternately and dried in a vacuum oven at 60°C for later use.

[0133] (4) Preparation of La / NiO-Ru@NF precursor

[0134] The sample in step (3) was placed in a 5mg mL -1 of RuCl3·xH2O solution for adsorption for 0.5h. After being taken out, it was freeze-dried at -40°C for 18h.

[0135] (5) Preparation of La / NiO-Ru@NF

[0136] The sample of step (4) was annealed in a tube furnace under argon atmosphere at 250°C for 4h and cooled to room temperature naturally. The sample after annealing was washed with deionized water for three times and then dried in a vacuum oven at 60°C for standby, i.e. the final HER catalyst La / NiO-Ru was prepared.

[0137] Example 5

[0138] (1) NF cleaning

[0139] The commercial NF was sequentially cleaned in acetone, ethanol and deionized water by ultrasonic cleaning. Then, the NF was immersed in 1M hydrochloric acid for 10min and cleaned in deionized water by ultrasonic cleaning for three times. Finally, the NF was dried in a vacuum oven at 60°C for standby.

[0140] (2) Preparation of Pr / Ni-MOF@NF

[0141] 1mmol of NiCl2·6H2O, 0.05mmol of Pr(NO3)3·6H2O and 3mmol of TPA were sequentially weighed and added to a container containing 17.5mL of DMF to obtain a mixed solution. After stirring at room temperature for 60min, 2.5mL of water and 2.5mL of ethanol were added for continuous stirring. After the mixture was sufficiently mixed, the mixed solution was transferred to the inner liner of a PTFE reaction kettle, and a clean NF was placed in it. After the reaction kettle was sealed, a 140°C hydrothermal reaction was carried out in the hydrothermal box for 12h. After the reaction was completed, the sample was naturally cooled to room temperature. After the sample was taken out, it was washed with deionized water and ethanol alternately and then dried in a vacuum oven at 60°C for standby.

[0142] (3) Preparation of Pr / NiO@NF

[0143] The La / Ni-MOF@NF prepared in step (2) was placed in a reaction kettle liner containing 40mL of deionized water. After the reaction kettle was sealed, a hydrothermal reaction was carried out at 160°C for 6.5h. After the reaction was completed, the sample was taken out, washed with deionized water and ethanol alternately, and then dried in a vacuum oven at 60°C for standby.

[0144] (4) Preparation of Pr / NiO-Ru@NF precursor

[0145] The sample in step (3) was placed in a 1mg mL -1 solution of RuCl3·xH2O and soaked for 4h for adsorption. After being taken out, it was freeze-dried at -80°C for 36h.

[0146] (5) Preparation of Pr / NiO-Ru@NF

[0147] The sample of step (4) was annealed in a tube furnace at 400℃ for 1h under argon atmosphere and cooled to room temperature naturally. The sample was washed with deionized water for three times and dried in a vacuum oven at 60℃ for standby, which was the final HER catalyst Pr / NiO-Ru.

[0148] Preparation of NiO@NF

[0149] The difference between this comparative example and example 1 is that the sample was collected at step (3) and no Ce(NO3)3·6H2O was added in step (2).

[0150] Preparation of Ce / NiO@NF

[0151] The difference between this comparative example and example 1 is that the sample was collected at step (3) and no step (4) and (5) was performed.

[0152] Preparation of NiO-Ru@NF

[0153] The difference between this comparative example and example 1 is that no Ce(NO3)3·6H2O was added in step (2) only.

[0154] The products obtained in the above examples and comparative examples were characterized by the present application, and the results are analyzed as follows:

[0155] Figure 1 A flow chart of catalyst preparation is described. First, Ni 2+ , Ce 3+ and TPA are hydrothermally treated in DMF solvent to grow Ce-doped Ni-MOF (Ce / Ni-MOF@NF) on the surface of NF; then Ce / Ni-MOF@NF is pyrolyzed in aqueous solvent to decompose the ligand and obtain Ce / NiO@NF, which ensures the connection of metal-oxygen bond in the catalyst material; finally, Ce / NiO@NF is immersed in RuCl3 solution, Ru 3+ is adsorbed on the surface of Ce / NiO and is balanced, and then annealed in a tube furnace to obtain Ce / NiO-Ru@NF.

[0156] In order to analyze the micro-morphology of the catalyst material, the inventors of the present application tested the catalyst by scanning electron microscope. NiO-Ru@NF and Ce / NiO-Ru@NF are the main controls of the present application, and the beneficial effects of oxygenophilic Ce doping on the catalyst are specifically analyzed, and uniform loading on the surface of NF skeleton is the prerequisite for performance comparison. As Figure 2a 、 2bAs shown, due to the process advantage of the application, whether it is NiO-Ru@NF or Ce / NiO-Ru@NF, the catalyst is fully coated on the surface of NF, and there is no exposed part, which ensures the stability of the current generated per unit area in the subsequent electrochemical test. On the other hand, the Ce doping has an impact on the micro-morphology of the catalyst, and the NiO-Ru@NF presents a porous sheet morphology Figure 2b ). This is because the initial Ni-MOF nucleates and grows uniformly along the surface of the NF, so that the Ni-MOF is cross-linked together to present a porous feature, and the uniformity is maintained in the micro-morphology. At the same time, there is a spacing of about 3 μm between the sheet layers, which also reflects the micro-densification of the catalyst. For the Ce-doped catalyst, the micro-morphology has changed, resulting in a large difference, as shown in Figure 2c and Figure 2d . The Ce / NiO-Ru@NF presents a linear nanosheet morphology, and the linear nanosheets are stacked together. It is analyzed that during the initial MOF synthesis, the Ce salt is nitrate, and the Ni salt is chloride. The ionization difference between the two causes the Ce 3+ to preferentially combine with TPA, providing a template for the growth of Ni-MOF, so that the growth of Ce-doped Ni-MOF is directional, and grows into a linear nanosheet. As can be seen from Figure 2d , the width of the present nanosheet is about 1 μm, the length is about 10 μm, and the surface presents a very smooth feature. The stacked linear nanosheets have a larger contact surface with H2O, OH* and H* in the electrolyte, which is more conducive to the electrocatalytic reaction, and provides a prerequisite for accelerating the reaction kinetics. At the same time, the XPS total spectrum confirms the existence of elements in the synthesized catalyst (as shown in Figure 3 ).

[0157] The electrochemical test of the application is carried out in 1M KOH using a three-electrode system, the catalyst is used as the working electrode, the carbon rod is used as the counter electrode, and the Hg / HgO is used as the reference electrode. It should be noted that Pt has strong HER activity, in order to standardize the electrochemical test and exclude the Pt sheet / silk / net from being dissolved and then cathodically deposited, Pt sheet electrode clamps and Pt counter electrodes are not selected. Since the test is carried out in an alkaline environment, the Hg / HgO reference electrode is selected. All potentials are converted from Hg / HgO to RHE. Figure 4a is the linear voltammetry scan curve of the catalyst, and the HER performance of NiO, Ce / NiO, NiO-Ru, Ce / NiO-Ru and commercial Pt / C catalysts is compared here. For NiO and Ce / NiO, it is obvious that they do not have HER activity, and the current density is less than 10 mA cm -2current density, a overpotential of 350 mV or more is required due to the lack of active sites for H conversion in the catalyst, but it can be observed that the performance of NiO after Ce doping is improved, which can explain that Ce-doped NiO enhances OH adsorption, and the higher proton concentration required for H conversion at high overpotential provides a mechanism for the subsequent existence of active Ru sites for H conversion. After loading Ru, both NiO-Ru and Ce / NiO-Ru have good catalytic activity, and Ce / NiO-Ru has better performance, which is due to the above-mentioned analysis of the enhanced OH adsorption of Ce-doped NiO, the Ru site regulated by Ce doping enhances the ability of H2 to H conversion, and accelerates the water dissociation rate, both of which have a strong synergistic effect, enhancing the alkaline HER performance. At the same time, it can be seen that the performance of the catalysts by this strategy is higher than that of the commercial Pt / C catalyst, which reflects the application potential of Ru-based catalysts. To verify the performance of the catalysts at the kinetic level, Tafel slope analysis needs to be performed, as shown in Figure 4b , the Tafel slope from large to small is consistent with the LSV curve rule, NiO (184.5 mV dec-1) > Ce / NiO (183.8 mV dec-1) > NiO-Ru (85.2 mV dec-1) > Pt / C (75.7 mV dec-1) > Ce / NiO-Ru (58.2 mV dec-1), which proves that Ce / NiO-Ru has the fastest reaction kinetics, and as the current density increases, the required overpotential is smaller than that of other catalysts. The overpotential and Tafel slope of the three better-performing catalysts are more intuitively reflected in Figure 4c . For HER catalysis, stability is also one of the most critical indicators to measure the quality of the catalyst, as shown in Figure 4d , Ce / NiO-Ru performs a chronopotentiometric test at a current density of 10 mA cm -2 , and the catalyst exhibits strong stability, and the overpotential does not increase after 50 h of continuous operation, only fluctuations caused by gas escape, which is considered to be excellent HER stability of Ce / NiO-Ru.

[0158] The scanning electron microscope images of the catalyst prepared in Example 2 of the present application are shown in Figure 5a and Figure 5b , and the LSV curve is shown in Figure 9a . The scanning electron microscope images of the catalyst prepared in Example 3 of the present application are shown in Figure 6a and Figure 6b , and the LSV curve is shown in Figure 9a .

[0159] The scanning electron microscope images of the catalyst prepared in Example 4 of the present application are shown in Figure 7a and Figure 7b , and the LSV curve is shown in Figure 9bThe scanning electron microscope image of the catalyst prepared in Example 5 is shown in Figure 5. Figure 8a and Figure 8b The LSV curve is shown in Figure 6. Figure 9b

[0160] In summary, the catalyst prepared by the present application and the strategy adopted not only provides a simple and environmentally friendly preparation method for high-performance HER catalysts, but also successfully verifies the beneficial effects of the catalyst structure design of the present application on alkaline HER. Specifically embodied as: (1) Ce-doped NiO carrier uniformly anchors Ru, showing very excellent HER activity; (2) oxygenophilic Ce-doped NiO promotes the adsorption of OH on the catalyst and the influence of Ru sites promotes the conversion of H on the Ru surface, which successfully promotes the dissociation of water. The present application is suitable for large-scale production of alkaline HER catalysts in the future and brings considerable economic benefits in the level of electrolytic tank hydrogen production.

[0161] In addition, the present inventors have also carried out tests with other raw materials, process operations and process conditions described in the present specification with reference to the foregoing examples, and all have obtained relatively ideal results.

[0162] Obviously, the above-mentioned embodiments of the present application are only intended to illustrate the principles of the present application, not to limit the embodiments thereof. Those skilled in the relevant art can modify or change the present application in other forms based on the above description. Since it is impossible to enumerate all the embodiments, but any obviously derivable technical solution changes are still protected by the present application.​

Claims

1. A rare earth element-doped hydrogen evolution electrocatalyst, characterized in that, include: Rare earth elements are used as carriers to dop nickel oxide, and ruthenium atoms are anchored on the carrier.

2. The rare earth element-doped hydrogen evolution electrocatalyst according to claim 1, characterized in that: The rare earth elements include at least one of cerium, lanthanum, and praseodymium.

3. The rare earth element-doped hydrogen evolution electrocatalyst according to claim 1, characterized in that: The rare earth element content in the rare earth element-doped hydrogen evolution electrocatalyst is 2.5~7.5wt%.

4. The rare earth element-doped hydrogen evolution electrocatalyst according to claim 1, characterized in that: The rare earth element-doped hydrogen evolution electrocatalyst has a linear nanosheet structure, and the linear nanosheets are stacked on top of each other.

5. The rare earth element-doped hydrogen evolution electrocatalyst according to claim 4, characterized in that: The linear nanosheets have a length of 5-20µm, a width of 1-3µm, and a thickness of less than 0.5µm.

6. A method for preparing a rare earth element-doped hydrogen evolution electrocatalyst, characterized in that, include: The nickel source, rare earth element source, MOF precursor, and organic solvent are mixed to form a mixed solution. Then water and alcohol are added to obtain a hydrothermal reaction system; The hydrothermal reaction system is subjected to a first hydrothermal reaction to obtain rare earth element / Ni-MOF precursor material; The rare earth element / Ni-MOF precursor material is mixed with water to carry out a second hydrothermal reaction to obtain the rare earth element / NiO material. The rare earth element / NiO material is brought into full contact with and adsorbed by a ruthenium source, and then freeze-dried to obtain a rare earth element / NiO-Ru precursor material. The rare earth element / NiO-Ru precursor material is annealed in a protective atmosphere to obtain a rare earth element / NiO material anchored with ruthenium atoms, i.e., a rare earth element-doped hydrogen evolution electrocatalyst.

7. The preparation method according to claim 6, characterized in that: The rare earth element source includes at least one of cerium, lanthanum, and praseodymium.

8. The preparation method according to claim 7, characterized in that: The rare earth element source includes at least one of cerium nitrate, lanthanum nitrate, and praseodymium nitrate.

9. The preparation method according to claim 6, characterized in that: The nickel source includes NiCl2.

10. The preparation method according to claim 6, characterized in that: The molar ratio of the nickel source, rare earth element source and MOF precursor is 1:(0.025~0.075):

3.

11. The preparation method according to claim 6, characterized in that: The MOF precursor includes terephthalic acid.

12. The preparation method according to claim 6, characterized in that: The organic solvent includes N,N-dimethylformamide.

13. The preparation method according to claim 6, characterized in that: The molar volume ratio of the nickel source to the organic solvent is 0.5~2 mmol: 17.5~70 mL.

14. The preparation method according to claim 6, characterized in that: The alcohols include ethanol.

15. The preparation method according to claim 6, characterized in that: The volume ratio of the organic solvent, water, and alcohol is 17.5~70:1.25~5:1.25~5.

16. The preparation method according to claim 6, characterized in that, The preparation method includes: stirring the mixed solution at room temperature for 30 min to 2 h, then adding water and alcohol, and continuing to stir to obtain a hydrothermal reaction system.

17. The preparation method according to claim 6, characterized in that: The temperature of the first hydrothermal reaction is 100~140 ℃, and the time is 12~24 h.

18. The preparation method according to claim 6, characterized in that: The temperature of the second hydrothermal reaction is 160~200 ℃, and the time is 5.5~6.5 h.

19. The preparation method according to claim 6, characterized in that: The ruthenium source includes RuCl3.

20. The preparation method according to claim 6, characterized in that, The preparation method includes: impregnating the rare earth element / NiO material in a ruthenium source aqueous solution and adsorbing it.

21. The preparation method according to claim 20, characterized in that: The soaking time is 0.5 h to 4 h.

22. The preparation method according to claim 20, characterized in that: The concentration of the ruthenium source aqueous solution is 1~5 mg / mL. -1 .

23. The preparation method according to claim 6, characterized in that: The freeze-drying temperature is -80~-40℃, and the time is 18~36 h.

24. The preparation method according to claim 6, characterized in that: The annealing process is carried out at a temperature of 250~400℃ for 1~4 hours.

25. The preparation method according to claim 6, characterized in that: The protective atmosphere includes an argon atmosphere.

26. A rare earth element-doped hydrogen evolution electrocatalyst prepared by any one of claims 6-25.

27. The application of the rare earth element-doped hydrogen evolution electrocatalyst according to any one of claims 1-5 and 26 in the hydrogen production reaction by water electrolysis.

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