Preparation method of NiSNiSe2 heterojunction containing non-interface Ni vacancy

Abstract

The invention discloses a preparation method of a NiS / NiSe2 heterojunction containing a non-interface Ni vacancy. The preparation method comprises the steps of precursor preparation and in-situ selenylation treatment. The invention further discloses the NiS / NiSe2 heterojunction containing the non-interface Ni vacancy. The NiS / NiSe2 heterojunction containing the non-interface Ni vacancy is prepared through the method.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterial preparation and electrocatalysis technology, specifically to a method for preparing NiS / NiSe2 heterojunctions containing non-interfacial Ni vacancies. Technical Background

[0002] Hydrogen energy, due to its high energy density and environmentally friendly properties, is considered an ideal energy source to replace fossil fuels. The electrolysis of water to produce hydrogen is an important method, but its efficiency is highly dependent on the performance of the catalyst. Currently, while platinum, a precious metal, exhibits excellent performance, its scarcity and high cost limit its large-scale application. Therefore, developing low-cost, highly active non-precious metal catalysts is of great significance.

[0003] In existing catalyst modification strategies, vacancy engineering and interface engineering are key means to improve performance. Among these, metal vacancies, due to their high formation energy, are more difficult to prepare and maintain stably than non-metallic vacancies. Currently, most metal vacancies are concentrated at the interface; however, under electrochemical reaction conditions, interfacial metal vacancies often undergo structural reconstruction due to high surface energy and the influence of active intermediates, leading to instability. Therefore, how to construct stable metal vacancies at non-interfacial sites in heterojunctions is a pressing technical challenge that needs to be addressed. Summary of the Invention

[0004] The purpose of this invention is to disclose a NiS / NiSe2 heterojunction with low overpotential and containing non-interfacial Ni vacancies. This invention also provides a method for preparing a NiS / NiSe2 heterojunction containing non-interfacial Ni vacancies.

[0005] The present invention proposes a method for preparing the NiS / NiSe2 heterojunction containing non-interfacial Ni vacancies, comprising the following steps: weighing high-purity nickel powder and sulfur powder according to an atomic molar ratio of nickel to sulfur of 2.8:2, mixing them evenly, pressing them into sheets, and sealing them in a quartz tube filled with argon gas; placing the sealed quartz tube in a muffle furnace and sintering it at 800°C to obtain NiS / NiSe2 heterojunction containing nickel vacancies. 2.8 S2 precursor; Ni obtained from the above treatment 2.8 The S2 precursor was placed in the downstream region of the tube furnace, and the selenium powder was placed in the upstream region of the tube furnace. Under a protective atmosphere, the tube furnace was heated to 450°C at a rate of 1°C / min, held at that temperature for 1 hour, and then cooled to room temperature.

[0006] The NiS / NiSe2 heterojunction containing non-interfacial Ni vacancies proposed in this invention exhibits excellent electrocatalytic activity. In acidic media, only an overpotential of 96 mV is required to achieve this. The current density is significantly better than that of materials without non-interface Ni vacancies. The overpotential is 200 mV. Attached Figure Description

[0007] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0008] Figure 1 The X-ray diffraction patterns are for comparative examples and embodiments; wherein, Figure 1 A is the complete X-ray diffraction pattern of the proportions and examples; Figure 1 B and Figure 1 C represents a magnified view of two feature regions in the embodiment.

[0009] Figure 2 The electron paramagnetic resonance spectra are for comparative and example embodiments.

[0010] Figure 3 The high-resolution lattice diagram shown in the example is marked by dashed lines indicating the phase interfaces of the heterojunction.

[0011] Figure 4 The image shown is a high-resolution transmission electron microscope image of an example.

[0012] Figure 5 The overpotential curves are for comparative examples and embodiments. Detailed Implementation

[0013] The present invention will be further described in detail below through specific embodiments, but the present invention is not limited to the following examples.

[0014] The specific steps of this embodiment are as follows: High-purity nickel powder and sulfur powder are weighed according to an atomic molar ratio of nickel to sulfur of 2.8:2, mixed evenly, pressed into sheets, and sealed in a quartz tube filled with argon gas; the sealed quartz tube is placed in a muffle furnace and sintered at 800°C to obtain Ni containing nickel vacancies. 2.8 S2 precursor; Ni obtained from the above treatment 2.8 The S2 precursor was placed in the downstream region of the tube furnace, and the selenium powder was placed in the upstream region of the tube furnace. Under a protective atmosphere, the tube furnace was heated to 450°C at a rate of 1°C / min, held at that temperature for 1 hour, and then cooled to room temperature.

[0015] To illustrate the technical effect of this embodiment, a sample was prepared as a comparative example according to the following steps: high-purity nickel powder and sulfur powder were weighed according to the atomic molar ratio of nickel to sulfur of 3:2, mixed evenly, pressed into sheets, and sealed in a quartz tube filled with argon gas; the sealed quartz tube was placed in a muffle furnace and sintered at 800°C to obtain a Ni3S2 precursor containing nickel vacancies; the Ni3S2 precursor obtained by the above treatment was placed in the downstream region of a tube furnace, and the selenium powder was placed in the upstream region of the tube furnace. Under a protective atmosphere, the tube furnace was heated to 450°C at a rate of 1°C / min, held for 1 hour, and then cooled to room temperature.

[0016] The present invention will be further described below with reference to the accompanying drawings, specific embodiments, and comparative examples.

[0017] Figure 1 A shows the X-ray powder diffraction patterns of samples prepared according to the methods of the examples and comparative examples. Two distinct sets of diffraction peaks can be clearly distinguished in the diffraction peaks of the examples and comparative examples. The diffraction peaks at 30.2, 34.7, 46.0, 53.5, and 60.9° correspond to the standard PDF card for NiS. Conversely, the second set at 29.8, 33.4, 36.7, 42.7, 45.4, 50.5, 52.9, 55.2, and 57.5° matches the standard PDF card for NiSe2. Notably, the absence of redundant Ni3S2 diffraction peaks indicates the thoroughness of the selenization process. Comparing the diffraction peaks of the examples and comparative examples reveals that the diffraction peaks of the examples are shifted to the right relative to the diffraction peaks of the comparative examples, as shown below. Figure 1 As shown in B and 1C, this is due to the decrease in lattice constant caused by Ni vacancies.

[0018] Figure 2 The electron paramagnetic resonance (EPR) spectra of the comparative and example samples are shown. The EPR spectra further reveal the vacancy properties of the prepared example samples. The characteristic peak at a g-factor of 2.003 is attributed to dangling Ni-S bonds, and the peak intensity is related to the concentration of Ni vacancies. We can see that the example samples exhibit much higher intensities than the comparative samples, indicating the formation of strong Ni vacancies.

[0019] Figure 3 The image shown is a high-resolution lattice diagram of an embodiment; the dashed lines indicate... The phase interface with NiS. The superimposed atomic structure diagram shows the schematic atomic occupancy of NiSe2. It can be seen that the presented high-resolution lattice image matches well with the

[010] crystal plane of NiSe2 and the

[102] crystal plane of NiS. To further confirm the vacancy situation of the sample of the example, the sample was characterized at atomic resolution using a spherical aberration-corrected scanning transmission electron microscope. Figure 4As shown. In high-resolution electron microscopy images, locations containing vacancies have lower brightness. To illustrate the brightness variation more clearly, Figure 4 B and 4C respectively show the directions along Figure 4 The brightness distribution of the two lines in Figure A shows a clear difference in brightness due to the presence of nickel vacancies at the non-interface location, indicated by the arrows in the figure. Therefore, XRD, EPR, and STEM images all provide reliable evidence for the successful fabrication of nickel Ni vacancies at the non-interface location.

[0020] The electrocatalytic activity of the synthesized samples for the hydrogen evolution reaction was evaluated using an electrochemical workstation, such as... Figure 5 As shown in the figure, the comparative example and the embodiment require overpotentials of 200 mV and 96 mV, respectively, to achieve the desired effect. The current density was significantly reduced. This marked decrease in overpotential indicates that the formation of the NiS / NiSe2 heterointerface and the presence of non-interfacial vacancies greatly enhance the HER activity. On one hand, the formation of NiS / NiSe2 and the presence of non-interfacial vacancies promote efficient electron transfer between NiS and NiSe2, which is necessary for the electrochemical reduction of protons to hydrogen. This improved electron transfer accelerates the kinetics of HER and reduces the overpotential. On the other hand, the presence of the NiS / NiSe2 heterointerface and the presence of non-interfacial vacancies alters the local coordination environment of Ni ions, thereby affecting their intrinsic catalytic activity by changing the electronic structure of Ni ions.

[0021] It should be noted that the above descriptions are merely preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations directly derived or conceived by those skilled in the art without departing from the basic concept of the present invention should be considered to be included within the scope of protection of the present invention.

Claims

1. A method for preparing a NiS / NiSe2 heterojunction containing non-interfacial Ni vacancies, characterized in that, The process includes the following steps: Weigh high-purity nickel powder and sulfur powder according to an atomic molar ratio of nickel to sulfur of 2.8:2, mix them thoroughly, press them into sheets, and seal them in a quartz tube filled with argon gas; place the sealed quartz tube in a muffle furnace and sinter it at 800℃ to obtain Ni containing nickel vacancies. 2.8 S2 precursor; Ni obtained from the above treatment 2.8 The S2 precursor was placed in the downstream region of the tube furnace, and the selenium powder was placed in the upstream region of the tube furnace. Under a protective atmosphere, the tube furnace was heated to 450°C at a rate of 1°C / min, held at that temperature for 1 hour, and then cooled to room temperature.

2. A NiS / NiSe2 heterojunction containing non-interfacial Ni vacancies as described in claim 1, characterized in that, The material consists of a heterojunction structure composed of NiS and NiSe2 phases, and contains non-interfacial Ni vacancies.

3. A NiS / NiSe2 heterojunction containing non-interfacial Ni vacancies as described in claim 1, characterized in that, It is used as an electrocatalyst for the hydrogen evolution reaction in acidic electrolytes.

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