NiFe-LDH-coated E-PBA composite electrocatalyst rich in oxygen vacancies and preparation method and application thereof

Abstract

The invention discloses a NiFe-LDH-coated E-PBA composite electrocatalyst rich in oxygen vacancies as well as a preparation method and application of the NiFe-LDH-coated E-PBA composite electrocatalyst. The preparation method specifically comprises the following steps: firstly, carrying out alkali etching on NiFe-PBA which is electrodeposited on foamed nickel, and then electrodepositing an ultrathin NiFe-LDH nanosheet on the surface of the NiFe-PBA. Alkali etching and electro-deposition enable the composite catalyst to contain rich oxygen vacancies, and the OER intrinsic activity can be enhanced by reducing band gaps and adsorption; the three-dimensional NiFe-LDH-coated E-PBA heterostructure can adjust interface charge distribution, optimize adsorption / desorption energy of an OER intermediate and release more active sites and mass transfer channels; the foamed nickel substrate provides rapid electron transfer and mass transfer. Therefore, the NiFe-LDH-coated E-PBA shows excellent alkaline water OER performance and stability, the overpotential is only 263 mV when the current density is 100 mA / cm < 2 >, and the NiFe-LDH-coated E-PBA can stably electrocatalytically decompose water for 50 h under the constant current density of 50 mA / cm < 2 >.

Description

Technical field:

[0001] The present invention belongs to the field of new energy material technology and electrochemical catalysis, and specifically relates to a NiFe-LDH@E-PBA composite electrocatalyst rich in oxygen vacancies; it also relates to a method for preparing the catalyst and its application in an oxygen evolution reaction at an anode of water electrolysis. Background technology:

[0002] Water electrolysis is an effective method for hydrogen production and shows great potential in alleviating the energy crisis. Water electrolysis can be decomposed into a cathode two-electron hydrogen evolution (HER) process and an anode four-electron oxygen evolution (OER) process. Compared with HER, the OER process has a slow reaction kinetics, which seriously limits the energy conversion efficiency of water splitting. Therefore, it is imperative to develop stable and efficient OER catalysts to improve the overall hydrogen production efficiency. Precious metal (Ru and Ir) oxides are recognized as commercial benchmark catalysts for OER, however, their high cost and poor stability under harsh electrolysis conditions limit their practical application. Therefore, it is very important to develop efficient non-precious metal OER electrocatalysts to improve the economy of water electrolysis. Nickel-iron layered double hydroxide (NiFe-LDH) has been demonstrated to be the most active transition metal-based OER electrocatalyst due to its unique composition and layered structure. However, conventional NiFe-LDH still has some disadvantages, such as poor conductivity, limited active sites, and self-aggregation, which seriously hinder the catalyst from achieving perfect performance. To overcome the above obstacles, one of the effective methods is to construct a three-dimensional (3D) hierarchical structure, which can release more active sites and ensure rapid mass transfer. The rearrangement of interfacial electrons can promote charge transfer and optimize the adsorption / desorption energy of intermediates in the electrocatalytic process. Another important strategy is to introduce vacancies in LDH nanosheets. The rich oxygen vacancies (O V ) can destroy the electronic neutrality of the lattice and produce unsaturated atomic active sites, thereby enhancing the electrocatalytic activity. In addition, conductive substrates such as nickel foam (NF) are often used for the in situ growth of electrocatalysts. In the absence of any binder, two-dimensional (2D) or 2D-3D nanostructures tightly fixed on nickel foam can improve the conductivity of the catalyst and effectively expose the active centers. Therefore, integrating these methods is an important strategy for preparing efficient OER electrocatalysts.

[0003] Prussian blue (PB) and its analogs (PBAs) are a class of perovskite materials that have great application prospects in energy conversion and storage due to their large specific surface area, adjustable composition and morphology. The molecular formula of Prussian blue analogs is usually described as A x M[Fe(CN)6] y·mH2O (y < 1, 0 < x < 2), where M is a transition metal and A is an alkali metal. In this material, the N-coordinated M cations and the C-coordinated Fe sites are bridged by cyanide (CN) groups to form an open framework structure. Although cyanide has a strong coordination with transition metals, it is extremely unstable in harsh environments such as strong alkalis or high temperatures. Therefore, Prussian blue analogues can be used as precursors for preparing transition metal oxides / hydroxides, phosphides, sulfides, etc.

[0004] Ion exchange method and hydrothermal method have been widely used in the preparation of PBAs and LDHs. However, the ion exchange method usually takes a long time, and the hydrothermal method requires a high-temperature and high-pressure environment with high energy consumption. In contrast, electrochemical deposition is a rapid and effective method for preparing nanostructures with various morphologies on conductive electrodes, with advantages such as low temperature, controllability, and environmental friendliness.

[0005] In this invention, a 3D cubic structure PBA precursor was first prepared by electrodeposition method, and its surface was transformed into amorphous nickel hydroxide rich in oxygen vacancies through a simple alkali etching process. Then, two-dimensional NiFe-LDH nanosheets were deposited on the surface of the 3D PBA cube rich in oxygen vacancies through further electrodeposition. Oxygen vacancies in the composite catalyst play an important role in improving the intrinsic activity of the electrocatalyst for oxygen evolution reaction; the 3D hierarchical structure can release more active sites and optimize the adsorption / desorption energy of *OOH, *O, and *OH intermediates. The synergistic effect between NiFe-LDH and E-PBA provides effective electron and mass transfer. The NiFe-LDH@E-PBA composite catalyst exhibits excellent alkaline water OER performance, and the overpotential is only 263 mV at a current density of 100 mA / cm 2 Moreover, the electrocatalyst shows excellent long-term stability and can stably electrocatalytically decompose water for 50 h at a constant current density of 50 mA / cm 2 , and its OER performance is better than that of the state-of-the-art IrO2 catalyst. The excellent OER performance of NiFe-LDH@E-PBA is attributed to the large number of oxygen vacancies induced by the amorphous phase, the synergistic effect between the three-dimensional heterostructures, and the high conductivity and gas diffusion channels provided by the nickel foam skeleton, endowing it with high intrinsic electrocatalytic activity, abundant active sites, and good electron mass transfer characteristics. This invention provides a simple strategy for constructing amorphous three-dimensional heterostructure materials with abundant oxygen vacancies, which has certain application prospects in the fields of energy conversion and storage. Summary of the Invention:

[0006] In view of the deficiencies of the prior art and the needs of research and application in this field, one of the purposes of the present invention is to provide a NiFe-LDH@E-PBA composite electrocatalyst rich in oxygen vacancies; the electrocatalyst is characterized in that the electrocatalyst is based on nickel foam, and a NiFe-LDH@E-PBA three-dimensional layered structure rich in oxygen vacancies is constructed by electrodeposition and alkaline etching methods; the oxygen vacancy concentration of the electrocatalyst is adjusted by alkaline etching and electrodeposition time; the electrocatalyst has excellent catalytic performance for alkaline anode oxygen evolution reaction; wherein NiFe-LDH is nickel-iron double metal hydroxide, and E-PBA is an alkaline-etched nickel-iron Prussian blue analogue;

[0007] The second object of the present invention is to provide a method for preparing a NiFe-LDH@E-PBA composite electrocatalyst rich in oxygen vacancies, which specifically comprises the following steps:

[0008] (a) Preparation of NiFe-PBA

[0009] Three pieces of 2×3cm 2 The nickel foam was ultrasonically treated with 1 mol / L hydrochloric acid solution, deionized water and ethanol for 30, 5 and 10 minutes respectively; the electrodeposition was carried out in a three-electrode system, in which the pre-treated nickel foam was used as the working electrode, the silver / silver chloride electrode was used as the reference electrode, and the platinum wire placed in parallel was used as the auxiliary electrode; the electrolyte was a mixed solution containing 1mmol / LK3Fe(CN)6, 1mmol / L Ni(NO3)2·6H2O and 1mol / LNaNO3; the electrodeposition was completed by 240 cycles of cyclic voltammetry scanning, with a scanning rate of 100mV / s and a scanning voltage of 0-1V (vs.Ag / AgCl), and the deposited electrode was fully rinsed with deionized water and dried at 60°C for 6h for standby use;

[0010] (b) Preparation of E-PBA

[0011] The NiFe-PBA prepared in step (a) is immersed in 1 mol / L KOH at room temperature for 10 to 60 minutes, and then fully rinsed with deionized water and anhydrous ethanol and dried at 60° C. for 6 hours for later use;

[0012] (c) Preparation of NiFe-LDH@E-PBA

[0013] In a three-electrode system, NiFe-LDH@E-PBA was prepared by electrodeposition technology, wherein the E-PBA prepared in step (b) was used as a working electrode, a silver / silver chloride electrode was used as a reference electrode, a platinum wire placed in parallel was used as an auxiliary electrode, and the electrolyte was a mixed solution containing 1mmol / L Ni(NO3)2·6H2O and 1mmol / LFeSO4·7H2O; the electrodeposition was carried out at a constant voltage of -1V for 5 to 40 minutes; the electrode after deposition was dried at 60°C for 6h for use;

[0014] In the prepared oxygen vacancy-rich NiFe-LDH@E-PBA composite electrocatalyst, the size of the NiFe-PBA cubes is 100-200nm; the E-PBA after alkali etching retains the original cubic morphology, but the etching of strong alkali makes the surface rougher and the edges and corners of the cubic structure disappear; the thickness of the NiFe-LDH nanosheets is 15-20nm, and they grow in situ on the surface of the E-PBA nanocubes in the form of small-sized ultra-thin nanosheets, forming a three-dimensional hierarchical heterogeneous structure; this structure can provide more active sites and more mass transfer channels for catalytic reactions.

[0015] The third object of the present invention is to provide a NiFe-LDH@E-PBA composite electrocatalyst rich in oxygen vacancies, characterized in that the catalyst is used for alkaline anode oxygen evolution reaction.

[0016] The present invention prepares a three-dimensional NiFe-LDH@E-PBA heterostructure rich in oxygen vacancies by two-step electrodeposition and alkaline etching of NiFe-PBA. Alkaline etching and electrodeposition make Ni(OH)2 and NiFe-LDH produced by NiFe-PBA conversion have rich V O , these V O The intrinsic OER activity of the catalyst can be enhanced by reducing the band gap and adsorption energy; the three-dimensional NiFe-LDH@E-PBA heterostructure can regulate the interfacial charge distribution, optimize the adsorption / desorption energy of OOH*, O* and OH* intermediates during the electrocatalytic process, release more active sites, and increase V O The concentration of nickel foam substrate is high, and the electron transfer and mass transfer are fast. Therefore, the catalyst has excellent OER catalytic activity and electrochemical catalytic stability.

[0017] Compared with the prior art, the present invention has the following main advantages and beneficial effects:

[0018] 1) The OER catalyst of the present invention is a non-precious metal material prepared by electrodeposition. The raw materials used are easy to purchase, abundant in resources and low in cost. The experimental method is more low-temperature, controllable and environmentally friendly compared to traditional high-temperature treatment;

[0019] 2) The NiFe-LDH@E-PBA composite electrocatalyst described in the present invention has unsaturated catalytic sites generated by abundant defects, which effectively reduces the overpotential of OER and exhibits excellent OER catalytic performance and stability, which is superior to most non-precious metal catalysts reported in current research.

[0020] 3) The NiFe-LDH@E-PBA composite electrocatalyst described in the present invention has better electrochemical performance than the commercial RuO2 electrode in the field of OER catalysis.

[0021] 4) The present invention is to construct a V-rich O Amorphous three-dimensional heterostructures provide a new strategy. Description of the drawings:

[0022] Figure 1 They are respectively the scanning electron microscope images of NiFe-PBA (A) obtained in comparative example 1, the E-PBA (B) obtained in example 5, the NiFe-LDH@E-PBA (C) obtained in example 1, and the transmission electron microscope image of NiFe-LDH@E-PBA (D) obtained in example 1.

[0023] Figure 2 XRD diagrams of NiFe-PBA obtained in Comparative Example 1, E-PBA (B) obtained in Example 5, and NiFe-LDH@E-PBA obtained in Example 1.

[0024] Figure 3 The catalysts E-PBA, E-PBA-10, E-PBA-30 and E-PBA-60 obtained in Examples 5, 6, 7 and 8 were prepared at 1.0 mol L -1 Linear sweep voltammogram of OER in KOH solution.

[0025] Figure 4 The catalysts NiFe-LDH@E-PBA, NiFe-LDH@E-PBA-5, NiFe-LDH@E-PBA-10 and NiFe-LDH@E-PBA-40 obtained in Example 1, Example 2, Example 3 and Example 4 were prepared at 1.0 mol L -1 Linear sweep voltammogram of OER in KOH solution.

[0026] Figure 5 The catalysts NiFe-LDH@E-PBA, E-PBA, NiFe-PBA, NiFe-LDH, NiFe-LDH@PBA obtained in Example 1, Example 5, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were quenched in 1.0 mol L -1 Linear sweep voltammogram of OER in KOH solution.

[0027] Figure 6 The catalyst NiFe-LDH@E-PBA obtained in Example 1 was heated to 1.0 mol L -1 Galvanostatic chronopotentiometry curves in KOH.

[0028] Figure 7 The catalyst NiFe-LDH@E-PBA obtained in Example 1 was heated to 1.0 mol L -1 Scanning electron microscopy image after 50h stability test in KOH solution. Specific implementation method:

[0029] For a further understanding of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited in any way.

[0030] Embodiment 1:

[0031] (a) Preparation of NiFe-PBA

[0032] Three pieces of 2×3cm 2 The nickel foam was ultrasonically treated with 1mol / L hydrochloric acid solution, deionized water and ethanol for 30, 5 and 10min respectively. The electrodeposition was carried out under a three-electrode system, in which the pre-treated nickel foam was used as the working electrode, the silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode, and the parallel platinum wire was used as the auxiliary electrode. The electrolyte contained 1mmol / L K3Fe(CN)6, 1mmol / L Ni(NO3)2·6H2O and 1mol / L NaNO3. Cyclic voltammetry (CV) was performed for 240 cycles with a scan rate of 100mV / s and a scanning voltage of 0~1V (vs.Ag / AgCl). The deposited material was fully rinsed with deionized water and dried at 60℃ for 6h for later use.

[0033] (b) Preparation of E-PBA

[0034] The pre-prepared NiFe-PBA was immersed in 1 mol / L KOH for 20 min. The immersed material was fully rinsed with deionized water and anhydrous ethanol and then dried at 60 °C for 6 h.

[0035] (c)NiFe-LDH@E-PBA

[0036] NiFe-LDH@E-PBA was prepared by electrodeposition in a three-electrode system, in which the pre-prepared E-PBA was used as the working electrode, the silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode, and the parallel platinum wire was used as the auxiliary electrode. The electrolyte contained 1mmol / L Ni(NO3)2·6H2O and 1mmol / LFeSO4·7H2O. The electrodeposition was carried out at a constant voltage of -1V for 20min. After naturally cooling to room temperature, the obtained sample was NiFe-LDH@E-PBA.

[0037] Embodiment 2:

[0038] (a) Preparation of NiFe-PBA

[0039] Prepared according to the method and conditions of step (a) in Example 1.

[0040] (b) Preparation of E-PBA

[0041] Prepared according to the method and conditions of step (b) in Example 1.

[0042] (c)NiFe-LDH@E-PBA

[0043] NiFe-LDH@E-PBA was prepared by electrodeposition in a three-electrode system, in which the pre-prepared E-PBA was used as the working electrode, the silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode, and the platinum wire placed in parallel was used as the auxiliary electrode. The electrolyte contained 1mmol / L Ni(NO3)2·6H2O and 1mmol / LFeSO4·7H2O. The electrodeposition was carried out at a constant voltage of -1V for 5min. After naturally cooling to room temperature, the obtained sample was NiFe-LDH@E-PBA-5.

[0044] Embodiment 3:

[0045] (a) Preparation of NiFe-PBA

[0046] Prepared according to the method and conditions of step (a) in Example 1.

[0047] (b) Preparation of E-PBA

[0048] Prepared according to the method and conditions of step (b) in Example 1.

[0049] (c)NiFe-LDH@E-PBA

[0050] NiFe-LDH@E-PBA was prepared by electrodeposition in a three-electrode system, in which the pre-prepared E-PBA was used as the working electrode, the silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode, and the platinum wire placed in parallel was used as the auxiliary electrode. The electrolyte contained 1mmol / L Ni(NO3)2·6H2O and 1mmol / LFeSO4·7H2O. The electrodeposition was carried out at a constant voltage of -1V for 10min. After naturally cooling to room temperature, the obtained sample was NiFe-LDH@E-PBA-10.

[0051] Embodiment 4:

[0052] (a) Preparation of NiFe-PBA

[0053] Prepared according to the method and conditions of step (a) in Example 1.

[0054] (b) Preparation of E-PBA

[0055] Prepared according to the method and conditions of step (b) in Example 1.

[0056] (c)NiFe-LDH@E-PBA

[0057] NiFe-LDH@E-PBA was prepared by electrodeposition in a three-electrode system, in which the pre-prepared E-PBA was used as the working electrode, the silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode, and the platinum wire placed in parallel was used as the auxiliary electrode. The electrolyte contained 1mmol / L Ni(NO3)2·6H2O and 1mmol / LFeSO4·7H2O. The electrodeposition was carried out at a constant voltage of -1V for 40min. After naturally cooling to room temperature, the obtained sample was NiFe-LDH@E-PBA-40.

[0058] Embodiment 5:

[0059] (a) Preparation of NiFe-PBA

[0060] Prepared according to the method and conditions of step (a) in Example 1.

[0061] (b) Preparation of E-PBA

[0062] The sample obtained by preparing according to the method and conditions of step (b) in Example 1 is E-PBA.

[0063] Embodiment 6:

[0064] (a) Preparation of NiFe-PBA

[0065] Prepared according to the method and conditions of step (a) in Example 1.

[0066] (b) Preparation of E-PBA

[0067] The pre-prepared NiFe-PBA was immersed in 1 mol / L KOH for 10 min. The immersed material was fully rinsed with deionized water and anhydrous ethanol and dried at 60°C for 6 h. The obtained sample was E-PBA-10.

[0068] Embodiment 7:

[0069] (a) Preparation of NiFe-PBA

[0070] Prepared according to the method and conditions of step (a) in Example 1.

[0071] (b) Preparation of E-PBA

[0072] The pre-prepared NiFe-PBA was immersed in 1 mol / L KOH for 30 min. The immersed material was fully rinsed with deionized water and anhydrous ethanol and dried at 60°C for 6 h. The obtained sample was E-PBA-30.

[0073] Embodiment 8:

[0074] (a) Preparation of NiFe-PBA

[0075] Prepared according to the method and conditions of step (a) in Example 1.

[0076] (b) Preparation of E-PBA

[0077] The pre-prepared NiFe-PBA was immersed in 1 mol / L KOH for 60 min. The immersed material was fully rinsed with deionized water and anhydrous ethanol and dried at 60°C for 6 h. The obtained sample was E-PBA-60.

[0078] Comparative Example 1:

[0079] (a) Preparation of NiFe-PBA

[0080] Prepared according to the method and conditions of step (a) in Example 1.

[0081] Comparative Example 2:

[0082] (a) Preparation of NiFe-LDH

[0083] NiFe-LDH was prepared by electrodeposition in a three-electrode system, in which NF was used as the working electrode, silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode, and a platinum wire placed in parallel was used as the auxiliary electrode. The electrolyte contained 1mmol / L Ni(NO3)2·6H2O and 1mmol / L FeSO4·7H2O. The electrodeposition was carried out at a constant voltage of -1V for 20min. After naturally cooling to room temperature, the obtained sample was NiFe-LDH.

[0084] Comparative Example 3:

[0085] (a) Preparation of NiFe-PBA

[0086] Prepared according to the method and conditions of step (a) in Example 1.

[0087] (b) Preparation of NiFe-LDH@PBA

[0088] NiFe-LDH@PBA was prepared by electrodeposition in a three-electrode system, in which the pre-prepared NiFe-PBA was used as the working electrode, the silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode, and the platinum wire placed in parallel was used as the auxiliary electrode. The electrolyte contained 1mmol / L Ni(NO3)2·6H2O and 1mmol / LFeSO4·7H2O. The electrodeposition was carried out at a constant voltage of -1V for 20min. After naturally cooling to room temperature, the obtained sample was NiFe-LDH.

[0089] Figure 1 The scanning electron microscope images of NiFe-PBA (A) obtained in comparative example 1, E-PBA (B) obtained in example 5, NiFe-LDH@E-PBA (C) obtained in example 1, and the transmission electron microscope image of NiFe-LDH@E-PBA (D) obtained in example 1 are shown. It can be seen from the figure that NiFe-PBA nanocubes with clear corners and edges of about 100 to 200 nm in size are evenly covered on the surface of nickel foam. After alkali etching, E-PBA maintains a good cubic morphology, but the etching of strong alkali makes its surface rougher and the corners of the cubic structure disappear. The reaction during the etching process can be expressed as: Ni2 2+ Fe(CN)6+4OH - =2Ni(OH)2+[Fe(CN)6] 4- Ultrathin NiFe-LDH nanosheets were deposited on the surface of E-PBA, and the SEM image of the obtained NiFe-LDH@E-PBA catalyst showed that NiFe-LDH nanosheets with a thickness of 15 to 20 nm were uniformly grown vertically on the surface of E-PBA. Figure 1TEM of D shows that the NiFe-LDH@E-PBA composite catalyst is composed of NiFe-LDH nanosheets and E-PBA nanocubes, in which the two-dimensional ultra-thin NiFe-LDH nanosheets are tightly stacked on the surface of the three-dimensional E-PBA nanocubes, constructing a three-dimensional hierarchical heterogeneous structure, which can provide more abundant catalytic active sites and more mass transfer channels for catalytic reactions.

[0090] Figure 2 The XRD patterns of NiFe-PBA obtained in Comparative Example 1, E-PBA (B) obtained in Example 5, and NiFe-LDH@E-PBA obtained in Example 1 are shown. The XRD diffraction peaks of NiFe-PBA correspond to the standard card JCPDS No. 46-0908, and the three obvious characteristic peaks (2θ = 17.59°, 24.97° and 35.61°) correspond to the (200), (220) and (400) crystal planes of NiFe-PBA, respectively, proving that the crystalline NiFe-PBA phase was successfully synthesized. After etching, the E-PBA nanocubes exhibited diffraction lines similar to those of NiFe-PBA, but due to the introduction of defects during the etching process, the peak intensity was significantly reduced and the half-peak width was wider relative to the original NiFe-PBA. There were no characteristic diffraction peaks related to Ni(OH)2, indicating that the Ni(OH)2 produced by etching was amorphous. Impressively, the electrodeposition of NiFe-LDH showed no hydrotalcite-related diffraction peaks, indicating that NiFe-LDH exists in the form of ultrathin nanosheets with low crystallinity, which can provide more catalytic sites to promote the OER process. Due to the coverage of ultrathin NiFe-LDH nanosheets, the XRD diffraction intensity of NiFe-LDH@E-PBA is further reduced relative to that of E-PBA nanocubes.

[0091] The above electrocatalytic performance tests all used a saturated Hg / HgO electrode as a reference electrode, a stone mill rod electrode as a counter electrode, a scan rate of 1 mV / s, and a compensation degree of 90%.

[0092] Figure 3 The catalysts E-PBA, E-PBA-10, E-PBA-30 and E-PBA-60 obtained in Examples 5, 6, 7 and 8 were prepared at 1.0 mol L -1 OER linear sweep voltammetry curve in KOH solution. It can be seen from the figure that when the alkaline etching time is 20 min, the E-PBA catalyst obtained has a -1 The OER electrocatalytic performance in KOH solution is the best.

[0093] Figure 4The catalysts NiFe-LDH@E-PBA, NiFe-LDH@E-PBA-5, NiFe-LDH@E-PBA-10 and NiFe-LDH@E-PBA-40 obtained in Example 1, Example 2, Example 3 and Example 4 were prepared at 1.0 mol L -1 OER linear sweep voltammetry curve in KOH solution. It can be seen that when the electrodeposition time of NiFe-LDH is 20 min, the obtained catalyst NiFe-LDH@E-PBA has the best electrocatalytic performance.

[0094] Figure 5 The catalysts NiFe-LDH@E-PBA, E-PBA, NiFe-PBA, NiFe-LDH, NiFe-LDH@PBA obtained in Example 1, Example 5, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were quenched in 1.0 mol L -1 OER linear sweep voltammetry curve in KOH solution. It can be seen from the figure that compared with NiFe-PBA, E-PBA, NiFe-LDH and NiFe-LDH@PBA, NiFe-LDH@E-PBA has the best OER catalytic activity at a current density of 100mA / cm 2 The overpotential is only 263 mV. Compared with single-phase NiFe-LDH, the presence of E-PBA nanocubes can effectively avoid the stacking of NiFe-LDH nanosheets and provide more reactive sites. The defects in E-PBA can also adjust the electronic structure of NiFe-LDH and improve the intrinsic activity of the catalyst. Alkaline etching and electrodeposition make NiFe-PBA-transformed Ni(OH)2 and NiFe-LDH have rich V O , rich V O The intrinsic activity of the catalyst can be enhanced by reducing the band gap and adsorption energy; the three-dimensional NiFe-LDH@E-PBA heterostructure can regulate the interfacial charge distribution, optimize the adsorption / desorption energy of OOH*, O*, and OH* intermediates during the electrocatalytic process, release more active sites, and increase the concentration of oxygen vacancies. Therefore, NiFe-LDH@E-PBA has the lowest overpotential.

[0095] Figure 6 The catalyst NiFe-LDH@E-PBA obtained in Example 1 was heated to 1.0 mol L -1 The constant current chronopotentiometry curve in KOH. As shown in the figure, at a current density of 100 mA / cm 2 After 50 h of chronopotentiometry, the potential hardly changed, indicating that NiFe-LDH@E-PBA has good stability.

[0096] Figure 7The catalyst NiFe-LDH@E-PBA obtained in Example 1 was heated to 1.0 mol L -1 SEM images after 50h stability test in KOH solution. The SEM images show that NiFe-LDH@E-PBA still maintains a complete layered morphology after the stability test. It is worth noting that the thickness of the nanosheets increased compared to before the stability test, which may be due to the generation of an amorphous nickel hydroxide layer during the OER process.

Claims

1. A NiFe-LDH@E-PBA composite electrocatalyst rich in oxygen vacancies; characterized by The electrocatalyst is based on nickel foam, and a NiFe-LDH@E-PBA three-dimensional hierarchical structure rich in oxygen vacancies is constructed by electrodeposition and alkaline etching methods; the oxygen vacancy concentration of the electrocatalyst is adjusted by alkaline etching and electrodeposition time; the electrocatalyst has excellent catalytic performance for alkaline anode oxygen evolution reaction; wherein NiFe-LDH is nickel-iron double metal hydroxide, and E-PBA is an alkaline-etched nickel-iron Prussian blue analogue; the preparation method of the electrocatalyst is characterized by comprising the following specific steps: (a) Preparation of NiFe-PBA Three pieces of 2×3cm 2 The nickel foam was ultrasonically treated with 1 mol / L hydrochloric acid solution, deionized water and ethanol for 30, 5 and 10 minutes respectively; the electrodeposition was carried out in a three-electrode system, in which the pre-treated nickel foam was used as the working electrode, the silver / silver chloride electrode was used as the reference electrode, and the platinum wire placed in parallel was used as the auxiliary electrode; the electrolyte was a mixed solution containing 1mmol / L K3Fe(CN)6, 1mmol / L Ni(NO3)2·6H2O and 1mol / LNaNO3; the electrodeposition was completed by 240 cycles of cyclic voltammetry scanning, with a scanning rate of 100mV / s and a scanning voltage of 0-1V (vs.Ag / AgCl), and the deposited electrode was fully rinsed with deionized water and dried at 60°C for 6h for standby use; (b) Preparation of E-PBA The NiFe-PBA prepared in step (a) is placed in 1 mol / L KOH and soaked at room temperature for 10 to 20 minutes, and then fully rinsed with deionized water and anhydrous ethanol and dried at 60° C. for 6 hours for later use; (c) Preparation of NiFe-LDH@E-PBA In a three-electrode system, NiFe-LDH@E-PBA is prepared by electrodeposition technology, wherein the E-PBA prepared in step (b) is used as a working electrode, a silver / silver chloride electrode is used as a reference electrode, a platinum wire placed in parallel is used as an auxiliary electrode, and the electrolyte is a mixed solution containing 1mmol / L Ni(NO3)2·6H2O and 1mmol / L FeSO4·7H2O; the electrodeposition is carried out at a constant voltage of -1V for 5 to 40 minutes; the electrode after deposition is dried at 60°C for 6 hours for use; In the prepared oxygen vacancy-rich NiFe-LDH@E-PBA composite electrocatalyst, the size of the NiFe-PBA cubes is 100-200nm; the E-PBA after alkali etching retains the original cubic morphology, but the etching of strong alkali makes the surface rougher and the edges and corners of the cubic structure disappear; the thickness of the NiFe-LDH nanosheets is 15-20nm, and they grow in situ on the surface of the E-PBA nanocubes in the form of small-sized ultra-thin nanosheets, forming a three-dimensional hierarchical heterogeneous structure; this structure can provide more active sites and more mass transfer channels for catalytic reactions.

2. The NiFe-LDH@E-PBA composite electrocatalyst rich in oxygen vacancies according to claim 1, characterized in that The catalyst is used for alkaline anode oxygen evolution reaction.

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