WO-NiSe-CeO2 self-supporting heterostructure catalyst and preparation method thereof

Abstract

The invention relates to a WO-NiSe CeO2 self-supporting heterostructure catalyst and a preparation method thereof. The preparation method comprises the following steps: preparing Ni LDH at CeO2 on foamed nickel through a hydrothermal method, then realizing high-valence tungstate radical doping through impregnation exchange, and finally carrying out secondary hydrothermal selenylation to obtain a porous nanosheet heterojunction material with CeO2 nanoparticles attached to the surface, namely WO-NiSe at CeO2. The introduction of high-valence tungstate radicals and the coupling of CeO2 form a strong electron coupling interface on the surface of NiSe, and HER / OER charge transfer is accelerated. And according to a hard-soft acid-base (HSAB) theory, the high-valence metal serving as a relatively hard Lewis acid shows higher selectivity on OH <-> than Cl <->, so that accumulation of Cl <-> on the surface of the catalyst can be inhibited, the catalytic activity is remarkably improved, and the corrosion-resistant life is remarkably prolonged. According to the strategy, a new'activity-stability-cost 'ternary equilibrium normal form with the advantages of low overpotential, long-period stability and salt corrosion resistance is provided for seawater electrolytic hydrogen production, and the theoretical value and the industrialization potential are both achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of seawater electrolysis catalysts, in particular to a WO-NiSe@CeO2 self-supporting heterostructure catalyst and a preparation method thereof. BACKGROUND

[0002] Under the background of rapid consumption and sharp reduction of fossil fuels, energy shortage and environmental deterioration have increasingly attracted global attention. Hydrogen, as the beacon of renewable energy, is highly praised for its environmental sustainability and high energy density, and has become a model substitute for fossil fuels. In the face of freshwater shortage, seawater is increasingly considered a promising source for water electrolysis to produce hydrogen. However, the challenge of achieving efficient synergy between HER and OER, combined with the electrode corrosion and competitive chlorine evolution reaction (ClER) induced by chloride ions (Cl - ) in seawater, significantly reduces the overall activity and stability of seawater electrolysis.

[0003] Transition metal selenides (TMSs) are one of the most promising multifunctional electrocatalysts for future applications. TMSs exhibit high electrical conductivity due to the continuity of the density of states (DOS) near the Fermi level. And because of the rich diversity of crystal structures, TMSs can change their electronic structure by adjusting the crystal structure to match the reaction. In addition, CeO2, due to its abundant oxygen vacancies and flexible Ce 3+ and Ce 4+ oxidation state changes, can be used as an excellent cocatalyst to improve the HER and OER performance of the catalyst. According to the HSAB principle of Pearson, harder acids prefer to bind to harder bases (where OH - is harder than Cl - ), and high-valence metals act as harder Lewis acids, showing greater selectivity for OH - than Cl - , which inhibits the accumulation of Cl - on the surface of the catalyst. Therefore, we introduce high-valence tungstate by immersion doping to inhibit the accumulation of Cl - on the surface of the catalyst, and composite CeO2 to improve the catalytic performance of the catalyst. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the deficiencies and defects mentioned in the above background, and to provide a WO-NiSe@CeO2 self-supporting heterostructure catalyst and a preparation method thereof. The method is simple and efficient, and can prepare an electrolytic water catalyst with excellent hydrogen evolution activity and oxygen evolution activity by hydrothermal and high-temperature calcination methods. The catalyst can exhibit long-term stability at high current density, and can also be effectively applied to the seawater electrolysis process.

[0005] The preparation method of the WO-NiSe@CeO2 self-supporting heterostructure composite catalyst provided by the application comprises the following steps:

[0006] Step one: first, a piece of 2*2cm 2 foamed nickel is placed in 3M HCl, anhydrous ethanol and ultrapure water respectively for ultrasonic treatment for 15 minutes to remove possible oxides and organic impurities on the surface;

[0007] Step two: the foamed nickel (NF) treated in step one is placed in a 50mL reactor liner, 2-8mmol Ni(NO3)2·6H2O, 0-2mmol Ce(NO3)3·6H2O, 2-8mmol CH4N2O and 30mL deionized water are added. The above mixture is stirred for 30 minutes to ensure that each component is completely dissolved. Then the high-pressure reactor is placed in 100-180℃ for 12 hours. After the reaction is completed, it is cooled to room temperature, washed with deionized water several times, and dried in a 60℃ vacuum oven for 12 hours to obtain precursor 1, NiLDH@CeO2;

[0008] Step three: the precursor 1 is immersed in a 200mL ethanol / deionized water (volume ratio 1:4) mixed solution containing Na2WO4 (60mg). After 30-90min of reaction under 85℃ with vigorous stirring (300rpm), the sample is immediately recovered, washed with deionized water three times, and then dried in a 60℃ vacuum oven for 12h to obtain precursor 2, WO-Ni LDH@CeO2; Step four: 0-2mmol NaBH4 and 0-2mmol selenium powder are dissolved in 30ml saturated argon ethanol to obtain a clear NaHSe solution. Then, a piece of prepared precursor 2 (2cm*2cm) is placed in a 50mL Teflon-lined stainless steel autoclave. Then the autoclave is sealed and kept at 100-180℃ for 8 hours. After the reaction, washing and drying are carried out to obtain the WO-NiSe@CeO2 self-supporting heterostructure catalyst.

[0009] Compared with most existing electrocatalyst materials, the application has the following advantages:

[0010] 1. The application synthesizes a preparation method of a WO-NiSe@CeO2 self-supporting heterostructure catalyst. The nanosheet-shaped heterojunction catalyst prepared by using the strategy exhibits excellent electrocatalytic activity under 1M KOH alkaline conditions. When the current density is 100mA / cm 2 , the overpotential of the hydrogen evolution and oxygen evolution reactions is only 217.72mV and 285.91mV respectively, and the Tafel slope is 100.38mV / dec and 48.20mV / dec respectively, and the catalyst can maintain long-term stability under large current density.

[0011] 2. The present application synthesizes a WO-NiSe@CeO2 porous nanosheet heterojunction catalyst which exhibits excellent hydrogen evolution activity and oxygen evolution activity in both simulated seawater and real seawater environments. The doping of high-valence tungstate and the compounding of CeO2 effectively improve the catalyst activity and Cl - corrosion, solving the problems of low catalyst activity and poor stability during electrolysis of seawater. The present application simultaneously breaks through the activity, stability and cost bottlenecks in electrolysis of seawater, and is a potential next-generation low-cost seawater electrolysis catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 Polarization curve comparison diagram of HER in 1M KOH electrolyte of Example 1, Comparative Examples 1-4 and 20% Pt / C;

[0013] Figure 2 Polarization curve comparison diagram of OER in 1M KOH electrolyte of Example 1, Comparative Examples 1-4 and IrO2;

[0014] Figure 3 Comparison diagram of Tafel slope of hydrogen evolution in 1M KOH electrolyte of Example 1, Comparative Examples 1-4 and 20% Pt / C;

[0015] Figure 4 Comparison diagram of Tafel slope of oxygen evolution in 1M KOH electrolyte of Example 1, Comparative Examples 1-4 and IrO2;

[0016] Figure 5 Comparison diagram of hydrogen evolution overpotential in 1M KOH electrolyte of Example 1, Comparative Examples 1-4 at current density of 10 mA cm -2 , 100 mA cm -2 and 500 mA cm -2 ;

[0017] Figure 6 Comparison diagram of oxygen evolution overpotential in 1M KOH electrolyte of Example 1, Comparative Examples 1-4 at current density of 10 mA cm -2 , 100 mA cm -2 and 500 mA cm -2 ;

[0018] Figure 7 Hydrogen evolution reaction stability test curve of WO-NiSe@CeO2 prepared by the method of Example 1 in 1M KOH electrolyte at current density of 100 mA cm -2 and 500 mA cm -2 ;

[0019] Figure 8The WO-NiSe@CeO2 prepared by the method of Example 1 was tested for oxygen evolution reaction stability in 1M KOH electrolyte at a current density of 100mA cm -2 and 500mA cm -2 ;

[0020] Figure 9 The HER polarization curves of WO-NiSe@CeO2 prepared by the method of Example 1 before and after 5000 cycles of cyclic voltammetry were compared;

[0021] Figure 10 The OER polarization curves of WO-NiSe@CeO2 prepared by the method of Example 1 before and after 5000 cycles of cyclic voltammetry were compared;

[0022] Figure 11 The HER polarization curves of WO-NiSe@CeO2 prepared by the method of Example 1 in 1M KOH, 1M KOH+0.5M NaCl and 1M KOH+ seawater electrolyte were compared;

[0023] Figure 12 The OER polarization curves of WO-NiSe@CeO2 prepared by the method of Example 1 in 1M KOH, 1M KOH+0.5M NaCl and 1M KOH+ seawater electrolyte were compared;

[0024] Figure 13 The SEM image of WO-NiSe@CeO2 prepared by the method of Example 1 was provided;

[0025] Figure 14 The TEM image of WO-NiSe@CeO2 prepared by the method of Example 1 was provided;

[0026] Figure 15 The HRTEM image of WO-NiSe@CeO2 prepared by the method of Example 1 was provided;

[0027] Figure 16 The XRD image of WO-NiSe@CeO2 prepared by the method of Example 1 was provided. DETAILED DESCRIPTION

[0028] The application will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the following described embodiments can be combined in any manner to form new embodiments without conflict.

[0029] Example 1:

[0030] The method for preparing and application of the WO-NiSe@CeO2 self-supporting heterostructure catalyst provided in this embodiment are as follows:

[0031] (1) A piece of 2x2 cm 2 of NF was placed in 3M HCl, anhydrous ethanol, ultrapure water respectively for ultrasonic treatment for 15 min to remove the possible oxides and organic impurities on the surface, and then placed in an oven at 60℃ for drying for 6h for standby.

[0032] (2) The foam nickel (NF) treated in step one was placed in a 50mL reactor liner, and 2-8mmol Ni(NO3)2·6H2O, 0-2mmol Ce(NO3)3·6H2O, 2-8mmol CH4N2O and 30mL deionized water were added. The mixture was stirred for 30 minutes to ensure complete dissolution of each component. Then the high-pressure reactor was placed in 100-180℃ for 12 hours. After the reaction was completed, it was cooled to room temperature, washed with deionized water several times, and dried in a vacuum oven at 60℃ for 12 hours to obtain precursor 1, NiLDH@CeO2;

[0033] (3) The precursor 1 was immersed in a 200mL ethanol / deionized water (volume ratio 1:4) mixed solution containing Na2WO4(60mg). After 30-90min of reaction under 85℃ with vigorous stirring (300rpm), the sample was immediately recovered, washed with deionized water three times, and then dried in a vacuum oven at 60℃ for 12h to obtain precursor 2, WO-Ni LDH@CeO2;

[0034] (4) 0-2mmol NaBH4 and 0-2mmol selenium powder were dissolved in 30ml saturated argon ethanol solution to obtain a clear NaHSe solution. Then, a piece of prepared precursor 2 (2cm x 2cm) was placed in a 50mL Teflon-lined stainless steel autoclave. Then the autoclave was sealed and kept at 100-180℃ for 8 hours. After the reaction, washing and drying were carried out to obtain the WO-NiSe@CeO2 self-supported heterostructure catalyst.

[0035] Comparative Example 1

[0036] The difference between Comparative Example 1 and Example 1 is that the same process is adopted, and the cerium source and tungsten source are excluded to obtain NiSe.

[0037] Comparative Example 2

[0038] The difference between Comparative Example 2 and Example 1 is that the same process is adopted, and the nickel source and tungsten source are excluded to obtain CeO2.

[0039] Comparative Example 3

[0040] The difference between Comparative Example 3 and Example 1 is that the same process is adopted, and the tungsten source is excluded to obtain NiSe@CeO2.

[0041] Comparative Example 4

[0042] The difference between Comparative Example 4 and Example 1 is that, under the premise of using the same process, the cerium source was excluded, and WO-NiSe was obtained.

[0043] Experimental Example 1:

[0044] The products obtained in Examples 1 and Comparative Examples 1 to 4 were used as catalysts for HER and OER tests in 1M KOH, 1M KOH + 0.5M NaCl, and 1M KOH + seawater electrolytes. Electrochemical tests were performed on an electrochemical workstation (CHI660E) using a standard three-electrode system, with the Hg / HgO electrode as the reference electrode, the graphite rod electrode as the counter electrode, and the products prepared in Examples 1 and Comparative Examples 1 to 4 as the working electrode (cut to a geometric area of ​​1cm × 1cm). Linear sweep voltammetry (LSV) was used at 5mV s. -1 The scan rate was measured and 90% iR compensation was applied. iR correction was performed according to the following formula: E corr =E mea -iR(Ecorr is the iR compensation potential, E mea For experimental measurement of potential, R is the solution resistance). At a current density of 100 mA / cm². -2 Under the specified conditions, the electrochemical stability was tested using chronoamperometry.

[0045] Figure 1 This is a comparison of the HER polarization curves of Example 1, Comparative Examples 1-4, and 20% Pt / C in 1M KOH electrolyte. Figure 1 It can be seen from this that the WO-NiSe@CeO2 material has a performance of 100 mA / cm². -2 At a current density of 285.91 mV, the hydrogen evolution overpotential was 217.72 mV, which is superior to other comparative examples. This indicates that the WO-NiSe@CeO2 material exhibits excellent hydrogen evolution performance in alkaline electrolytes due to the synergistic effect of NiSe composite with CeO2 and tungstate doping.

[0046] Figure 2 This is a comparison of the OER polarization curves of Example 1, Comparative Examples 1-4, and IrO2 in 1M KOH electrolyte. Figure 2 It can be seen from this that the WO-NiSe@CeO2 material is at 100 mA cm⁻¹ -2 At a current density of 285.91 mV, the oxygen evolution overpotential is superior to that of other comparative examples. This indicates that, under the synergistic effect of NiSe composite with CeO2 material and tungstate doping, the WO-NiSe@CeO2 material exhibits excellent oxygen evolution performance in alkaline electrolyte.

[0047] Figure 3This is a comparison of the Tafel slopes for hydrogen evolution in Example 1, Comparative Examples 1-4, and 20% Pt / C in 1M KOH electrolyte. Figure 3 The results show that the Tafel slope of the hydrogen evolution reaction of the WO-NiSe@CeO2 material is 100.38 mV / dec, which is superior to other comparative examples besides Pt / C. This indicates that, under the synergistic effect of NiSe composite with CeO2 material and tungstate doping, the WO-NiSe@CeO2 material exhibits excellent hydrogen evolution performance in alkaline electrolyte.

[0048] Figure 4 This is a comparison of the Tafel slopes of oxygen evolution in Example 1, Comparative Examples 1-4, and IrO2 in 1M KOH electrolyte. Figure 4 The results show that the Tafel slope of the oxygen evolution reaction (OER) of the WO-NiSe@CeO2 material is 48.20 mV / dec, which is superior to the Tafel slope comparisons of other comparative examples. This indicates that, under the synergistic effect of NiSe composite with CeO2 material and tungstate doping, the WO-NiSe@CeO2 material exhibits excellent OER performance in alkaline electrolyte.

[0049] Figure 5 Examples 1, 1-4, and 20% Pt / C were prepared in 1M KOH electrolyte at a current density of 10 mA / cm². -2 100mA cm -2 and 500mA cm -2 A comparison of hydrogen evolution overpotentials at different times. From Figure 5 It can be seen from this that the WO-NiSe@CeO2 material has a performance of 10 mA / cm². -2 100mA cm -2 and 500mA cm -2 At high current densities, the hydrogen evolution overpotential is superior to that of other comparative examples. This indicates that the WO-NiSe@CeO2 material exhibits excellent hydrogen evolution catalytic activity even at high current densities.

[0050] Figure 6 Examples 1, 1-4, and IrO2 were prepared in 1M KOH electrolyte at a current density of 10 mA cm⁻¹. -2 100mAcm -2 and 500mAcm -2 A comparison diagram of oxygen evolution overpotential at different times. From Figure 6 It can be seen from this that the WO-NiSe@CeO2 material operates at 10 mA cm⁻¹ -2 100mA cm -2 and 500mA cm -2 At high current densities, the oxygen evolution overpotential is superior to that of other comparative examples. This indicates that the WO-NiSe@CeO2 material exhibits excellent oxygen evolution catalytic activity even at high current densities.

[0051] Figure 7 The hydrogen evolution reaction stability test curve of WO-NiSe@CeO2 in 1M KOH electrolyte, current density is 100mA cm -2 and 500mA cm -2 , the water electrolysis reaction is almost no decay for nearly 100h.

[0052] Figure 8 The oxygen evolution reaction stability test curve of WO-NiSe@CeO2 in 1M KOH electrolyte, current density is 100mA cm -2 and 500mA cm -2 , the water electrolysis reaction is almost no decay for nearly 100h.

[0053] Figure 9 The HER polarization curve comparison chart of WO-NiSe@CeO2 in 1M KOH electrolyte before and after 5000 cycles of CV cycle;

[0054] Figure 10 The OER polarization curve comparison chart of WO-NiSe@CeO2 in 1M KOH electrolyte before and after 5000 cycles of CV cycle;

[0055] Figure 11 The HER polarization curve comparison chart of WO-NiSe@CeO2 prepared by the method of Example 1 in 1M KOH, 1M KOH+0.5M NaCl and 1M KOH+ seawater electrolyte, which shows that the material has good hydrogen evolution activity whether in simulated seawater or real seawater environment;

[0056] Figure 12 The OER polarization curve comparison chart of WO-NiSe@CeO2 prepared by the method of Example 1 in 1M KOH, 1M KOH+0.5M NaCl and 1M KOH+ seawater electrolyte, which shows that the material has good oxygen evolution activity whether in simulated seawater or real seawater environment;

[0057] Figure 13 The scanning electron microscope image of WO-NiSe@CeO2 prepared by the method of Example 1;

[0058] Figure 14 The transmission electron microscope image of WO-NiSe@CeO2 prepared by the method of Example 1;

[0059] Figure 15 The high-resolution transmission electron microscope image of WO-NiSe@CeO2 prepared by the method of Example 1;

[0060] Figure 16X-ray diffraction pattern of WO-NiSe@CeO2 prepared by the method of Example 1.

[0061] In summary, the present application forms a stable porous nanosheet heterojunction catalyst on the foam nickel by secondary hydrothermal and soaking doping, which exhibits excellent catalytic performance on hydrogen evolution and oxygen evolution, and can exhibit long-term stability at large current density. In addition, the catalyst has high corrosion voltage and low corrosion current, and exhibits excellent corrosion resistance.

[0062] The above embodiments are only preferred embodiments of the present application, and cannot be used to limit the scope of protection of the present application, and any non-essential changes and substitutions made by those skilled in the art on the basis of the present application are within the scope of protection of the present application.

Claims

1. A method for preparing a WO-NiSe@CeO2 self-supporting heterostructure catalyst, comprising the following steps: (1) Place the nickel foam (NF) in a 50mL Teflon autoclave and add a mixed solution containing nickel source and cerium source. After hydrothermal treatment, wash and dry to obtain Ni LDH@CeO2. (2) The Ni LDH@CeO2 obtained in step 1 was immersed in a solution containing a tungsten source for ion exchange reaction. After stirring, it was taken out to obtain WO-Ni LDH@CeO2 modified with tungstate ions. (3) The Ni LDH@CeO2 obtained in step 2 is placed in a 50mL stainless steel autoclave lined with Teflon, an alkaline solution containing selenium powder is added, followed by a second hydrothermal treatment, washing and drying to obtain the WO-NiSe@CeO2 catalyst.

2. The method according to step (1) of claim 1, characterized in that, The mixed solution of nickel source and cerium source mentioned in step (1) consists of 2-8 mmol Ni(NO3)2·6H2O, 0-2 mmol Ce(NO3)3·6H2O, 2-8 mmol CH4N2O and 30 mL deionized water.

3. The method according to step (1) of claim 1, characterized in that, The hydrothermal reaction described in step (1) refers to a reaction at 100–180°C for 12 hours.

4. The method according to step (2) of claim 1, characterized in that, The tungsten source solution was a mixed solution of 200 mL ethanol / deionized water (volume ratio 1:4) containing 60 mg of Na2WO4.

5. The method according to step (2) of claim 1, characterized in that, The ion exchange soaking was carried out at 85°C with vigorous stirring (300 rpm) for 30–90 min.

6. The method according to step (3) of claim 1, characterized in that, The alkaline solution containing selenium powder is prepared by dissolving 0–2 mmol NaBH4 and 0–2 mmol selenium powder in 30 ml of ethanol saturated with argon and reacting for 45 min to obtain a clear NaHSe solution.

7. The method according to step (3) of claim 1, characterized in that, The hydrothermal reaction described in step (1) refers to a reaction at 100–180°C for 8 hours.

Images