Cation-vacancy-rich heterojunction catalytic material, preparation method and application thereof

Abstract

The application relates to a cation vacancy-rich heterojunction catalytic material and a preparation method and application thereof. The cation vacancies in the catalytic material can effectively adjust the electronic properties of a host material, thereby promoting charge transfer and redox reaction kinetics, and can also serve as additional host sites for inserting protons or alkali metal cations, promoting ion diffusion during electrochemical cycles; the formed cation vacancies can also expose more active sites, improve conductivity, promote mass transfer during the reaction, and thus improve the reaction catalytic activity. In the preparation method, the hydrothermal method process is simple, energy consumption is low, and the method is suitable for a wide range of applications. Raw materials are cheap and easy to obtain, the obtained product has good crystallinity, and the yield is high. The low-temperature reaction consumes less phosphating chemicals, has relatively low energy consumption, and has a higher safety factor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrocatalytic materials, and particularly relates to a cation-vacancy-rich heterojunction catalytic material and a preparation method and application thereof. BACKGROUND

[0002] With the growth of the world population and the decrease of fossil fuel energy supply, it is imperative to find effective alternative sustainable energy conversion technologies. Direct liquid fuel cells, which directly convert chemical energy stored in chemicals into electrical energy, have attracted much attention. Recently, urea solution and hydrazine have been used as liquid fuels, and the corresponding devices are named direct urea / hydrazine fuel cells (DUFC / DHzFC).

[0003] For example, cobalt defects in NiCo2O4 produce electron delocalization and increase the intrinsic conductivity, resulting in enhanced OER performance compared to the counterpart without cobalt defects (J. X. Zheng, X. F. Peng, Z. Xu, J. B. Gong and Z. Wang, Acs Catal, 2022, 12, 10245-10254.). In a recent study, the introduction of cation vacancies in the NiFe-LDH basal plane not only produced high catalytic activity, but also enhanced the stability of OER; their study showed that cation vacancies accelerated the evolution of the surface gamma-(NiFe)OOH phase and reduced metal dissolution, thereby improving the OER activity (L. S. Peng, N. Yang, Y. Q. Yang, Q. Wang, X. Y. Xie, D. Sun-Waterhouse, L. Shang, T. R. Zhang and G. I. N. Waterhouse, Angew Chem Int Edit, 2021, 60, 24612-24619.). There is no introduction of cation-vacancy-rich in the field of electrocatalytic UOR / HzOR to improve catalytic activity. SUMMARY

[0004] The technical problem to be solved by the present application is to solve the deficiencies in the prior art, thereby providing a cation-vacancy-rich heterojunction catalytic material for use in UOR / HzOR systems and a preparation method and application thereof.

[0005] The technical scheme adopted by the present application to solve the technical problem is:

[0006] A preparation method of a cation-vacancy-rich heterojunction catalytic material, comprising the following steps:

[0007] S1: Dissolve the hydrates of Ni(NO3)2, Co(NO3)2, Zn(NO3)2 or all three in deionized water, form a homogeneous mixed solution by stirring, and then carry out a hydrothermal reaction to obtain the product Zn-NiCo LDH by taking the precipitate after washing and drying;

[0008] S2: Disperse the Zn-NiCo LDH powder prepared in step S1 in a KOH solution to react, take the precipitate, wash, centrifuge and dry to obtain Ni(OH)2-Co(OH)2.

[0009] S3: Place the Ni(OH)2-Co(OH)2 obtained in step S2 and NaH2PO2·H2O in porcelain boats respectively and place them in the downstream and upstream respectively, and then heat and react in an oxygen-free atmosphere to obtain the cation-vacancy-rich heterojunction catalytic material Ni2P / CoP3-Zn after cooling. vac .

[0010] The Zn-NiCo LDH precursor doped with zinc after hydrothermal treatment is very consistent with NiCo-LDH.

[0011] After the Zn-NiCo LDH precursor is etched by KOH for three times, it is converted into Ni(OH)2-Co(OH)2 two-phase structure, which is well matched with Ni(OH)2 and Co(OH)2.

[0012] Finally, the Ni(OH)2-Co(OH)2 is phosphated to obtain the cation-vacancy-rich heterojunction catalytic material Ni2P / CoP3-Zn vac , the XRD image of which is well matched with Ni2P and CoP3.

[0013] Preferably, in the preparation method of the cation-vacancy-rich heterojunction catalytic material of the application, the molar ratio of Ni:Co:Zn elements in the three raw materials of Ni(NO3)2, Co(NO3)2, Zn(NO3)2 or the hydrates of all three in step S1 is 7:3:0.3.

[0014] The hydrothermal reaction in step S1 is carried out at 120±5℃ for 10-14 hours.

[0015] Preferably, in the preparation method of the cation-vacancy-rich heterojunction catalytic material of the application, the precipitate in step S1 is collected after being washed and centrifuged with deionized water and ethanol for multiple times, and then vacuum dried at 60±5℃ to obtain the product Zn-NiCo LDH.

[0016] Preferably, in the preparation method of the cation-vacancy-rich heterojunction catalytic material of the application, the concentration of the KOH solution in step S2 is 6.0±0.1M, the reaction temperature is 60±5℃, and the reaction time is 3-5h.

[0017] Preferably, in the preparation method of the cation-vacancy-rich heterojunction catalytic material of the present application, the precipitate after the reaction of the Zn-NiCo LDH powder dispersed in the KOH solution in the S2 step is washed with deionized water and ethanol, then dispersed in the KOH solution again, and the precipitate after the reaction is washed with deionized water and ethanol, and then dispersed in the KOH solution again, and the precipitate after the reaction is washed with deionized water and ethanol to completely remove zinc ions.

[0018] Preferably, in the preparation method of the cation-vacancy-rich heterojunction catalytic material of the present application, the heating reaction in the S3 step is heated to 350±2℃ at a heating rate of 2±0.1℃ / min for 2-3h. -1 Preferably, in the preparation method of the cation-vacancy-rich heterojunction catalytic material of the present application, the heating reaction in the S3 step is heated to 350±2℃ at a heating rate of 2±0.1℃ / min for 2-3h.

[0019] Preferably, in the preparation method of the cation-vacancy-rich heterojunction catalytic material of the present application, the oxygen-free atmosphere in the S3 step is a nitrogen atmosphere.

[0020] The present application also provides a cation-vacancy-rich heterojunction catalytic material prepared by the above preparation method.

[0021] The present application also provides a carbon fiber cloth anode material coated with the above cation-vacancy-rich heterojunction catalytic material on the surface.

[0022] The present application also provides the use of the above carbon fiber cloth anode material as an anode in a urea fuel cell.

[0023] The present application has the following advantages:

[0024] (1) The cation vacancies in the catalytic material can effectively adjust the electronic properties of the host material, thereby promoting charge transfer and redox reaction kinetics, and also serving as additional host sites for the insertion of protons or alkali metal cations, promoting ion diffusion during electrochemical cycling; the formed cation vacancies can also expose more active sites, improve electrical conductivity, and promote mass transfer during the reaction, thereby improving the reaction catalytic activity.

[0025] (2) Transition metal phosphides (TMP) have the advantages of low cost and abundant content. P atoms not only act as proton acceptors, but also can significantly weaken the hydrogen adsorption strength, thereby preventing the catalyst from being poisoned due to the close combination with hydrogen atoms. Generally, transition metal phosphides M x P yTMPs can be classified into two categories according to the atomic ratio of metal to phosphorus in the molecular formula, namely, phosphorus-poor TMPs, where x>y, and phosphorus-rich TMPs, x<y. P-poor TMPs with rich metal sites usually exhibit excellent electrical conductivity, but relatively poor electrocatalytic activity, while P-rich TMPs with rich P sites have better catalytic capacity, but poor electrical conductivity. The reason why P-rich TMPs have better catalytic activity is that the negative P sites are Lewis bases that can adsorb positively charged reaction intermediates. In this regard, compared with single TMP, the catalyst component constructed with P-rich and P-poor compositions will have superior catalytic performance.

[0026] (3) The heterostructure interface constructed is an effective strategy to realize the simultaneous modulation of the electronic structure and active sites of the catalyst. These characteristics not only maintain the inherent catalytic activity of each component, but also impart new or enhanced electrochemical properties due to the interface synergistic effect.

[0027] (4) In the preparation method of the present application, the hydrothermal process is relatively simple, low in energy consumption and widely applicable. By changing factors such as reaction temperature and reaction time, the morphology and crystal structure of the reaction product can be effectively controlled; the raw materials are cheap and easy to obtain, the obtained product has good crystallinity and high yield; the sealed environment of the hydrothermal process greatly reduces environmental pollution. Metal Zn is an amphoteric metal and can be dissolved in alkaline solution. By alkaline etching, the doped Zn 2+ can be effectively etched to form cation vacancies, promote mass transfer, expose more active sites, and greatly improve the catalytic performance. Low-temperature phosphating consumes less chemicals and has relatively low energy consumption and higher safety factor. BRIEF DESCRIPTION OF DRAWINGS

[0028] The technical solutions of the present application will be further described below in combination with the drawings and examples.

[0029] Figure 1 is the synthetic route of the preparation method of the cation vacancy-rich heterojunction catalytic material according to the embodiments of the present application;

[0030] Figure 2 is the X-ray diffraction spectrum, wherein a is the XRD pattern of Ni2P / CoP3-Zn vac , b is the XRD pattern of the hydrothermal precursor Zn-NiCo LDH, and c is the XRD pattern of the product Ni(OH)2-Co(OH)2 after alkaline etching three times.

[0031] Figure 3 is the UOR performance detection result graph, wherein (a) is the polarization curve and (b) is the corresponding Tafel slope comparison. (c) Nyquist plot obtained at 1.35 V vs. RHE potential. (d) Ni2P / CoP3-Zn vacChronoamperometric (i-t) tests were performed for UOR. p ) and UOR potential at 10±0.1 mA cm -2 .

[0032] Figure 4 are the performance testing results of HzOR, in which (a) polarization curves and (b) corresponding Tafel slopes are compared. (c) Nyquist plots obtained at 0.05±0.001 V vs. RHE potential. (d) Double-layer capacitance obtained by cyclic voltammetry at 0.15±0.01 V vs. RHE. (e) Chronopotentiometric (E-t) tests were performed for Ni2P / CoP3-Zn vac at a fixed current for 24 hours.

[0033] Figure 5 are the performance testing results of direct hydrazine fuel cells, in which (a) are the polarization curves of DUHPFCs, (b) are the 24h stability test curves with Ni2P / CoP3-Zn vac as the anode catalyst. (c) are the polarization curves of DHzFCs, (b) are the 24h stability test curves with Ni2P / CoP3-Zn vac as the anode catalyst. DETAILED DESCRIPTION

[0034] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0035] Embodiment 1

[0036] The embodiment provides a preparation method of a cation-vacancy-rich heterojunction catalytic material, comprising the following steps:

[0037] S1: Ni(NO3)2·6H2O, Co(NO3)2·6H2O, Zn(NO3)2·6H2O (the molar ratio of Ni:Co:Zn elements in the three raw materials is 7:3:0.3) and 10±0.1 mmol CO(NH2)2 are dissolved in 35±1 mL of deionized water to form a homogeneous solution by stirring. Pour the mixed solution into a 50±2 mL reaction kettle, and hydrothermally react at 125℃ for 10 hours. After the temperature is cooled to room temperature, the product is washed and centrifuged with deionized water and ethanol for several times, and finally dried under vacuum at 60±5℃. The obtained product is marked as Zn-NiCo LDH.

[0038] S2: The Zn-NiCo LDH powder prepared in step S1 was dispersed in 25 ± 2 mL of 6.0 ± 0.1 M KOH solution and reacted at 65 °C for 3 h. The precipitate was washed with deionized water and ethanol, then dispersed in KOH solution again and reacted to collect the precipitate, which was washed with deionized water and ethanol. The precipitate was dispersed in KOH solution again and reacted to collect the precipitate, which was washed with deionized water and ethanol to completely remove zinc ions. The final product was vacuum dried at 65 °C. It was labeled as Ni(OH)2-Co(OH)2.

[0039] S3: The Ni(OH)2-Co(OH)2 powder (50 ± 0.1 mg) obtained in step S2 and NaH2PO2·H2O (500 ± 0.1 mg) (i.e., the mass ratio of Ni(OH)2-Co(OH)2 powder to NaH2PO2·H2O was 1:10) were placed in two porcelain boats, respectively. The porcelain boat containing NaH2PO2·H2O particles was placed upstream, and the other was placed downstream. Then, it was heated to 352 °C at a heating rate of 2 ± 0.1 °C / min under N2 atmosphere for 2 h. The product obtained after cooling to room temperature was labeled as Ni2P / CoP3-Zn -1 vac .

[0040] Example 2

[0041] The present embodiment provides a method for preparing a cation vacancy-rich heterojunction catalytic material, comprising:

[0042] S1: Ni(NO3)2·6H2O, Co(NO3)2·6H2O, and Zn(NO3)2·6H2O (the molar ratio of Ni:Co:Zn elements in the three raw materials was 7:3:0.3) and 10 ± 0.1 mmol CO(NH2)2 were dissolved in 35 ± 1 mL of deionized water to form a homogeneous solution by stirring. The mixed solution was poured into a 50 ± 2 mL reaction kettle and hydrothermally reacted at 1202 °C for 12 hours. After the temperature cooled to room temperature, the product was washed with deionized water and ethanol several times and centrifuged to collect, and finally vacuum dried at 62 °C. The obtained product was labeled as Zn-NiCo LDH.

[0043] S2: The Zn-NiCo LDH powder prepared in step S1 was dispersed in 25 ± 2 mL of 6.0 ± 0.1 M KOH solution and reacted at 65 °C for 3 h. The precipitate was washed with deionized water and ethanol, then dispersed in KOH solution again and reacted to collect the precipitate, which was washed with deionized water and ethanol. The precipitate was dispersed in KOH solution again and reacted to collect the precipitate, which was washed with deionized water and ethanol to completely remove zinc ions. The final product was vacuum dried at 65 °C. It was labeled as Ni(OH)2-Co(OH)2.

[0044] ​S3: The Ni(OH)2-Co(OH)2 powder (50 ± 0.1 mg) obtained in step S2 and NaH2PO2-H2O (500 ± 0.1 mg) (i.e., the mass ratio of the Ni(OH)2-Co(OH)2 powder to NaH2PO2-H2O is 1:10) were placed in two porcelain boats, respectively, and the porcelain boat containing the NaH2PO2-H2O particles was placed upstream, and the other was placed downstream, and then heated to 350°C at a heating rate of 2 ± 0.1°C min-1under a N2 atmosphere for 2 h, and the obtained product was labeled as Ni2P / CoP3-Zn -1 vac .

[0045] Example 3

[0046] The present embodiment provides a method for preparing a cation-vacancy-rich heterojunction catalytic material, comprising:

[0047] S1: Ni(NO3)2-6H2O, Co(NO3)2-6H2O, Zn(NO3)2-6H2O (the molar ratio of Ni:Co:Zn elements in the three raw materials is 7:3:0.3) and 10 ± 0.1 mmol CO(NH2)2 were dissolved in 35 ± 1 mL of deionized water to form a homogeneous solution by stirring. The mixed solution was poured into a 50 ± 2 mL reaction kettle, and hydrothermal reaction was carried out at 120°C for 14 hours. After the temperature cooled to room temperature, the product was washed with deionized water and ethanol for several times and centrifuged to collect, and finally vacuum dried at 605°C. The obtained product was labeled as Zn-NiCo LDH.

[0048] S2: The Zn-NiCo LDH powder prepared in step S1 was dispersed in 25 ± 2 mL of 6.0 ± 0.1 M KOH solution at 60°C for 5 h, and the precipitate was washed with deionized water and ethanol. The precipitate was again dispersed in the KOH solution and reacted to obtain the precipitate, which was washed with deionized water and ethanol. The precipitate was again dispersed in the KOH solution and reacted to obtain the precipitate, which was washed with deionized water and ethanol. The precipitate was again dispersed in the KOH solution and reacted to obtain the precipitate, which was washed with deionized water and ethanol to completely remove the zinc ions. In order to completely remove the zinc ions, the above steps were repeated three times, and the final product was vacuum dried at 60°C. It was labeled as Ni(OH)2-Co(OH)2. 2+ S2: The Zn-NiCo LDH powder prepared in step S1 was dispersed in 25 ± 2 mL of 6.0 ± 0.1 M KOH solution at 60°C for 5 h, and the precipitate was washed with deionized water and ethanol. The precipitate was again dispersed in the KOH solution and reacted to obtain the precipitate, which was washed with deionized water and ethanol. The precipitate was again dispersed in the KOH solution and reacted to obtain the precipitate, which was washed with deionized water and ethanol. The precipitate was again dispersed in the KOH solution and reacted to obtain the precipitate, which was washed with deionized water and ethanol. The precipitate was again dispersed in the KOH solution and reacted to obtain the precipitate, which was washed with deionized water and ethanol to completely remove the zinc ions. In order to completely remove the zinc ions, the above steps were repeated three times, and the final product was vacuum dried at 60°C. It was labeled as Ni(OH)2-Co(OH)2.

[0049] S3: The Ni(OH)2-Co(OH)2 powder (50 ± 0.1 mg) obtained in step S2 and NaH2PO2-H2O (500 ± 0.1 mg) (i.e., the mass ratio of the Ni(OH)2-Co(OH)2 powder to NaH2PO2-H2O is 1:10) were placed in two porcelain boats, respectively, and the porcelain boat containing the NaH2PO2-H2O particles was placed upstream, and the other was placed downstream, and then heated to 350°C at a heating rate of 2 ± 0.1°C min-1under a N2 atmosphere for 2 h, and the obtained product was labeled as Ni2P / CoP3-Zn -1 ​at a heating rate of 10 °C min-1to 348 °C for 3 h, and then cooled to room temperature. The obtained product is labeled as Ni2P / CoP3-Zn vac .

[0050] 10 ± 0.1 mg of Ni2P / CoP3-Zn vac powder and 5 ± 0.1 mg of conductive carbon black were dispersed in a mixture of ethanol (950 ± 1 μL) and 5% Nafion solution (50 ± 1 μL) by ultrasonic treatment for 2 h to prepare an ink. A certain volume (5 ± 1 μL) of the above ink was dropped onto a glassy carbon electrode and dried at room temperature. The UOR performance test was carried out in the case of 1.0 ± 0.1 M KOH / 0.33 ± 0.01 M urea by cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), chronoamperometry (i-t) and other methods, and the HzOR measurement was carried out in the case of 1.0 ± 0.1 M KOH / 0.5 ± 0.01 M N2H4. The cation-vacancy-rich heterojunction catalytic material (Ni2P / CoP3-Zn vac heterostructure composed of phosphorus-poor Ni2P and phosphorus-rich CoP3) of the present embodiment has the following urea oxidation reaction (UOR) and hydrazine oxidation reaction (HzOR) catalytic performance:

[0051] (1) For UOR, Ni2P / CoP3-Zn vac can achieve a current density of 10 ± 0.1 mA cm-2at an extremely low overpotential of 1.311 ± 0.01 V vs. RHE, which is superior to Zn-NiCo LDH (1.39 ± 0.01 V) and Ni(OH)2-Co(OH)2(1.41 ± 0.01 V), demonstrating the positive effect of alkaline etching and phosphating treatment. In addition, it can provide a peak current density of 164 ± 0.1 mA cm-2at a potential of 1.6 ± 0.01 V vs. RHE, which is about 13 times and 10 times higher than that of Zn-NiCo LDH (13.2 ± 0.1 mA cm-2) and Ni(OH)2-Co(OH)2samples (15.8 ± 0.1 mA cm-2) at the same potential, respectively. -2 -2 -2 -2 vac The Tafel slope of Ni2P / CoP3-Zn -1 is only 37.24 ± 0.1 mV dec-1, which is much lower than that of Zn-NiCo LDH (94.39 ± 0.1 mV dec-1) and Ni(OH)2-Co(OH)2(92.71 ± 0.1 mV dec-1). -1 -1 ​​​​​), demonstrating its beneficial UOR kinetics. At a working potential of 1.35 ± 0.01 V vs. RHE, Ni2P / CoP3-Zn vac has a relatively small semicircle radius at high frequency, associated with a lower charge transfer resistance (R ct ), which means it has the fastest reaction kinetics. Ni2P / CoP3-Zn vac has the smallest R ct , which may be attributed to the abundant heterointerface and good electrical conductivity of the P-poor Ni2P. Moreover, it can maintain stability at a current density of 10 ± 0.1 mA cm -2 for 10 h. A direct urea fuel cell (DUHPFC) assembled with Ni2P / CoP3-Zn vac as the anode catalyst and 10% Pd / C as the cathode catalyst has a maximum power density of 16.22 ± 0.1 mW cm -2 at room temperature, which is about 1.68 times that of Zn-NiCo LDH (9.66 ± 0.1 mW cm -2 ) and 1.36 times that of Ni(OH)2-Co(OH)2(11.94 ± 0.1 mW cm -2 ). Moreover, it can maintain stability at a current density of 10 ± 0.1 mA cm -2 for 24 h with little change in current density, which is superior to most reported catalysts. The results are shown in Figure 3 .

[0052] (2) For HzOR, Ni2P / CoP3-Zn vac can reach a current density of 10 ± 0.1 mA cm -2 at a low overpotential of -47 ± 0.1 mV vs. RHE, which is much lower than that of Zn-NiCo LDH (29 ± 1 mV vs. RHE) and Ni(OH)2-Co(OH)2(269 ± 1 mV vs. RHE). In addition, the corresponding Tafel slope of Ni2P / CoP3-Zn vac is 54.3 ± 0.1 mV dec -1 , which is much lower than that of Zn-NiCo LDH (151.3 ± 0.1 mV dec -1 ) and Ni(OH)2-Co(OH)2(164.1 ± 0.1 mV dec -1 ), indicating its excellent HzOR kinetics. In addition, Ni2P / CoP3-Zn vac exhibits the smallest R ct compared with the other catalysts. Moreover, it can maintain stability at a current density of 10 ± 0.1 mA cm -2The stability of the current density was maintained for 24 h with almost no change in the current density. The maximum power density of the direct hydrazine fuel cell (DHZFC) assembled with Ni2P / CoP3-Zn vac as an anode catalyst and 20% Pt / C as a cathode catalyst was measured to be 229.01 ± 0.1 mW cm -2 at room temperature, which is about 1.46 times (157.18 ± 0.1 mW cm -2 ) of Zn-NiCo LDH and 1.92 times (119.91 ± 0.1 mW cm -2 ) of Ni(OH)2-Co(OH)2, and can maintain the stability of the current density for 24 h with almost no change in the current density at a large current density of 50 ± 0.1 mA cm -2 , which is superior to most of the reported catalysts. The results are shown in Figure 4 .

[0053] In the S2 step, the zinc ions can be completely removed through three reactions and three washes. As a comparison, the zinc ions can still be detected after two reactions and two washes.

[0054] Effect Example 1

[0055] A preparation method of a direct urea fuel cell (DUHPFC):

[0056] 200 ± 1 μL of ink for UOR was coated on a carbon cloth (0.4 x 0.5 cm) as an anode of the DUHPFC, and 5.0 ± 0.1 mg of 10% Pd / C was dispersed in a mixture of 380 ± 1 μL of ethanol and 5% Nafion (20 ± 1 μL) and coated on a carbon cloth (0.4 x 0.5 cm) as a cathode of the DUHPFC. The H-type direct urea-H2O2 fuel cell (acidic) in this work was assembled from the prepared anode (anode electrolyte: 4.0 ± 0.1 M KOH and 0.33 ± 0.01 M urea) and cathode (cathode electrolyte: 2.0 ± 0.1 M H2O2 and 2.0 ± 0.1 M H2SO4). The stability was recorded by chronoamperometry for 24 h. In addition, the electrolytes were separated by a proton exchange membrane (Nafion 115). In order to further evaluate the performance of the DUHPFCs, a multi-current program at different current densities (0, 1, 2, 4, 8, 12, 16, 20, 24, 28, 32, 36 mA cm -2 ) was performed.

[0057] Effect Example 2

[0058] A preparation method of a direct hydrazine fuel cell (DHZFC):

[0059] For HzOR, 200 ± 1 μL of ink was coated on carbon cloth (0.4 x 0.5 cm) as anode of DHzFC, while 5.0 ± 0.1 mg of Pt / C was dispersed in a mixture of 950 ± 1 μL of ethanol and 5% Nafion (50 ± 1 μL) and coated on carbon cloth (0.4 x 0.5 cm) as cathode of DHzFC. Ni2P / CoP3-Zn vac The preparation method of / CC anode was the same as that of Pt / C / CC, and the preparation method of catalyst ink was as described in the experimental section. The H-type direct N2H4-H2O2 fuel cell (acidic) in this work was assembled by the prepared anode (anolyte: 4 ± 0.1 M KOH and 10 wt% N2H4) and cathode (catholyte: 20 wt% H2O2 and 0.5 ± 0.01 M H2SO4). The stability was recorded by chronopotentiometry for 24 h. In addition, the electrolytes were separated by proton exchange membrane (Nafion 115). To further evaluate the performance of DHzFCs, a multi-current procedure was performed at different current densities (0, 20, 40, 60, 80, 100, 120, 140, 170, 200, 230, 260 mA cm -2 ).

[0060] With the above ideal embodiments according to the present application as the inspiration, through the above description, relevant staff can definitely make various changes and modifications without deviating from the scope of the technical idea of the present application. The technical scope of the present application is not limited to the content in the specification, and must be determined according to the scope of claims.

Claims

1. A method for preparing a cation-vacancy-rich heterojunction catalytic material, characterized in that, The following steps: S1: Dissolve Ni(NO3)2, Co(NO3)2, Zn(NO3)2 or their hydrates with CO(NH2)2 in deionized water, stir to form a homogeneous mixed solution, and carry out a hydrothermal reaction of the mixed solution to obtain the product Zn-NiCo LDH after washing and drying. S2: Disperse the Zn-NiCo LDH powder prepared in step S1 in KOH solution and react. Take the precipitate, wash, centrifuge and dry to obtain Ni(OH)2-Co(OH)2. S3: Ni(OH)2-Co(OH)2 and NaH2PO2·H2O obtained in step S2 are placed in a porcelain boat, with the boat positioned downstream and upstream, respectively. The mixture is then heated and reacted under an oxygen-free atmosphere. After cooling, Ni2P / CoP3-Znvac, a heterojunction catalyst rich in cation vacancies, is obtained.

2. The method for preparing the cation-vacancy-rich heterojunction catalytic material according to claim 1, characterized in that, In step S1, the molar ratio of Ni:Co:Zn elements in the three raw materials, Ni(NO3)2, Co(NO3)2, Zn(NO3)2, or their hydrates, is 7:3:0.

3. In step S1, the hydrothermal reaction is carried out at 120±5℃ for 10-14 hours.

3. The method for preparing the cation-vacancy-rich heterojunction catalytic material according to claim 1, characterized in that, In step S1, the precipitate was collected after being washed and centrifuged multiple times with deionized water and ethanol, and then vacuum dried at 60±5℃ to obtain the product Zn-NiCo LDH.

4. The method for preparing the cation-vacancy-rich heterojunction catalytic material according to claim 1, characterized in that, In step S2, the KOH solution concentration is 6.0±0.1M, the reaction temperature is 60±5℃, and the reaction time is 3-5h.

5. The method for preparing the cation-vacancy-rich heterojunction catalytic material according to claim 1, characterized in that, In step S2, the precipitate of Zn-NiCo LDH powder dispersed in KOH solution is washed with deionized water and ethanol, then dispersed again in KOH solution for reaction. The precipitate is then washed with deionized water and ethanol, dispersed in KOH solution for reaction once more, and the precipitate is washed with deionized water and ethanol to completely remove zinc ions.

6. The method for preparing the cation-vacancy-rich heterojunction catalytic material according to claim 1, characterized in that, In step S3, the reaction is heated to 350±2℃ at a heating rate of 2±0.1℃min-1 for 2-3 hours.

7. The method for preparing the cation-vacancy-rich heterojunction catalytic material according to claim 1, characterized in that, The oxygen-free atmosphere mentioned in step S3 is a nitrogen atmosphere.

8. A cation-vacancy-rich heterojunction catalytic material, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. A carbon fiber cloth anode material, the surface of which is coated with the cation-vacancy-rich heterojunction catalyst material of claim 8.

10. The application of the carbon fiber cloth anode material as described in claim 9 as the anode in a urea fuel cell.

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