A method for preparing Ni3B / Ni electrocatalyst without calcination and its application

Abstract

This invention provides a synthesis method and application of a nickel-boron alloy and nickel composite (Ni3B / Ni). Specifically, the method comprises the following steps: 1) coprecipitating sodium borohydride and a nickel salt (nickel sulfate, nickel nitrate, nickel chloride, etc.) in a solution to obtain a nickel borate precursor; 2) vacuum treating the precursor to obtain a metastable intermediate product, which spontaneously combusts in air to produce a composite primarily composed of nickel-boron alloy and nickel (Ni3B / Ni > 80 wt%). This composite exhibits high activity and long life in the electrooxidation of methanol to formic acid, achieving a Faradaic efficiency of nearly 100% for the electrocatalytic production of formic acid from methanol at 100 mA cm. ‑2 It can operate stably for 50 hours at the current density. It can also be used for carbon dioxide reduction (CO2RR) and nitrate reduction (NO x RR) and other fields.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst materials and relates to a preparation method and application of a boron nickel alloy / nickel (Ni3B / Ni) catalyst with energy-saving, simple and efficient synthesis process and large-scale industrial production. Background Art

[0002] Boron nickel alloy is an inorganic compound with the general formula NixBy, which was originally used as a catalyst for various reactions under a hydrogen atmosphere. Boron nickel alloy has good catalytic effect, high chemical stability, good selectivity and reactivity in liquid phase reactions, and is now used as a reactant and catalyst in many reactions. Among them, Ni3B is widely used as a non-precious metal catalyst in hydrogenation\dehydrogenation catalysts, energy storage and electrocatalysis due to its unique high activity. Especially in the field of electrocatalysis, it is considered to be a multifunctional catalyst used in (electrocatalytic hydrogen evolution reaction) HER, (hydrogen oxidation reaction) HOR, (electrocatalytic oxygen evolution reaction) OER, (oxygen reduction reaction) ORR, (methanol oxidation reaction) MOR and (NOx reduction reaction) NO x RR etc. Boron nickel alloy (Ni x B) Nanosheets are one of the low-cost, efficient and stable catalysts for electrochemical water splitting (OER). Ni3B is an active, selective and stable catalyst for ORR to H2O2, which shows a high selectivity of more than 90% and an onset potential of 0.7V relative to the reversible hydrogen electrode (RHE). The heterogeneous structure of Ni3B / Ni catalyst enables the electrocatalytic oxidation (MOR) of methanol to formate with a Faradaic efficiency close to 100%. 6 Crystalline Ni3B as an OER electrocatalyst at 10 mA cm -2 It shows a small overpotential of 302mV and a 52mV dec -1 The Tafel slope of the porous Ni3B sintered with pure Ni and B powders in Ar gas showed good HER activity at a current density of 10 mA cm in 0.5MH2SO4 electrolyte. -2 , the HER overpotential is as low as 79 mV, and the Tafel slope is 85.32 mV dec -1 , and has outstanding stability. The Ni3B / Ni heterostructure exhibits excellent catalytic performance for hydrogen oxidation reaction (HOR) in alkaline media, and its mass activity is about 10 times greater than that of the Ni3B and Ni catalysts alone. It is one of the most active electrocatalysts without platinum group metals. Experimental results and theoretical calculations confirm the electron transfer from Ni3B to Ni at the Ni3B / Ni interface, resulting in mutual regulation of the d-band centers of the two components. This mutual regulation produces an optimized binding energy of the intermediate, which helps to enhance the alkaline HOR activity. Ni3B@NiB 0.72The boron-rich surface property is achieved by enhancing the NO x -Adsorption and inhibition of hydrogen evolution and surface Ni oxidation are key to improving activity, selectivity and stability. Ammonia production reached 198.3 μmol cm -2 h -1 , with a Faradaic efficiency approaching 100%. Ni3B was first synthesized in 1958. However, Ni3B synthesis methods primarily involve direct synthesis of nickel and boron sources under high temperature conditions in an inert atmosphere, or calcination of the product from solution precipitation under inert atmosphere. These harsh experimental conditions and long synthesis cycles are not conducive to energy conservation, environmental protection, or large-scale synthesis. Proposing simpler and more efficient synthesis methods is of great significance for advancing the development of boron-nickel alloy-based catalysts. Summary of the Invention

[0003] Nickel-based catalysts, particularly nanocatalysts composed of metallic nickel and nickel alloys, can be used in the electrocatalytic processes of hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), methanol oxidation reaction (MOR), and NOx reduction reaction (NOxRR). To achieve a highly efficient, cost-effective, and long-lived nickel-based catalyst, the present invention employs a method for preparing a nickel-based (Ni3B / Ni) catalyst without calcination.

[0004] The present invention proposes a method for reducing nickel borate to boron-nickel alloy by a vacuum induction method, which can be achieved only by vacuum treatment without heat treatment, and is therefore energy-saving and highly efficient.

[0005] The present invention proposes a synthesis process for a nickel-boron alloy / nickel catalyst (Ni3B / Ni), comprising the following steps: sodium borohydride and a nickel salt (nickel sulfate, nickel nitrate, nickel chloride) are coprecipitated in a solution to produce a black nickel borate precursor. The nickel borate precursor is then vacuum-treated to produce a dehydrated, metastable intermediate. The vacuum is then broken by momentary injection of air, which releases heat upon contact with the air, resulting in the product, a nickel-boron alloy (Ni3B / Ni).

[0006] Preferably, the total amount of Ni3B / Ni in the nickel-based catalyst synthesized in the present invention exceeds 80% by mass of the total sample, and has excellent anti-poisoning ability and stable electrocatalytic activity when applied to methanol electrocatalytic oxidation.

[0007] The precursor for the boron-nickel alloy / nickel catalyst (Ni3B / Ni) can be obtained by coprecipitating sodium borohydride with a nickel salt (nickel sulfate, nickel nitrate, nickel chloride, nickel sulfamate, nickel bromide, nickelous hydroxide, or nickel carbonyl) in solution. The resulting precursor can be in the form of flakes, spheres, or rods.

[0008] Preferably, the morphology and size of the obtained nickel borate precursor are 50-500 nm.

[0009] A method for reducing nickel borate to boron-nickel alloy / nickel by vacuum induction comprises the following steps: preparing sodium borohydride and one or more of the above-mentioned nickel salts into solutions; slowly mixing the two solutions to obtain a black nickel borate precipitate; and treating the precipitate in a vacuum for several hours. After the vacuum is broken, the sample spontaneously forms a boron-nickel alloy / nickel composite nanocatalyst (Ni3B / Ni) in the air.

[0010] A method for preparing a nickel-based (Ni3B / Ni) catalyst by a non-calcining method and its application, wherein the nickel-based catalyst is used in the field of electrocatalysis. Including methanol electrocatalytic oxidation (MOR), hydrogen electrochemical oxidation (HOR), electrochemical oxygen reduction (ORR), carbon dioxide reduction (CO2RR) and nitrate reduction (NO X RR).

[0011] The present invention offers the following advantages: The nickel-based (Ni3B / Ni) catalyst has a simple preparation process, high activity, long lifespan, and low price, enabling efficient and stable methanol oxidation. A key feature of the present invention is its vacuum-induced synthesis of the highly active nano-nickel-based (Ni3B / Ni) catalyst, which effectively simplifies the process flow, significantly reduces operating costs, and offers significant application value.

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. The drawings described below are merely examples of the present invention. Those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0013] Attachment Figure 1 This is an SEM image of the nickel borate precursor of the present invention.

[0014] Attachment Figure 2 This is the XRD pattern of nickel borate precursor of the present invention.

[0015] Attachment Figure 3 This is an SEM image of the target catalyst boron-nickel alloy / nickel in the present invention.

[0016] Attachment Figure 4 This is the XRD pattern of the target catalyst boron-nickel alloy / nickel of the present invention.

[0017] Attachment Figure 5 These are the cyclic voltammetry test results of the methanol oxidation performance of the precursor nickel borate of the present invention in different electrolytes.

[0018] Attachment Figure 6These are the cyclic voltammetry test results of the methanol oxidation performance of the precursor boron-nickel alloy / nickel of the present invention in different electrolytes.

[0019] Attachment Figure 7 The figure shows a comparison of the performance of the two catalysts of the present invention in catalyzing methanol oxidation at different current densities.

[0020] Attachment Figure 8 The boron nickel alloy / nickel sample of the present invention is 100mA cm -2 Stability test results under constant high current density.

[0021] Attachment Figure 9 The electrochemical activity test results of the boron-nickel alloy / nickel sample of the present invention after 50 hours of stability test.

[0022] Attachment Figure 10 is the Faradaic efficiency of the boron nickel alloy / nickel sample of the present invention for electrocatalyzing methanol to produce formate.

[0023] Attachment Figure 11 These are the Tafel data of the nickel borate sample and the boron nickel alloy / nickel sample, which are precursors of the present invention.

[0024] Attachment Figure 12 These are the cyclic voltammetry test results of the maximum voltage and maximum current density that can be used for the boron-nickel alloy / nickel sample of the present invention.

[0025] Attachment Figure 13 The performance of the boron-nickel alloy / nickel sample of the present invention is compared with existing commercial precious metal catalysts.

[0026] Attachment Figure 14 1 is the cyclic voltammetry curve of the boron-nickel alloy / nickel sample before and after the compensation voltage drop (iR) in the present invention.

Claims

1. A method for preparing Ni3B / Ni nickel-based catalyst material without calcination, characterized in that: The following steps are involved: 1) Sodium borohydride and nickel salt are co-precipitated in an aqueous solution to obtain a precipitated product as a precursor, the main component of which is nickel borate with crystal water, and the co-precipitation process does not require inert gas protection; 2) subjecting the precursor to vacuum treatment, whereby a portion of its crystalline water is removed in the vacuum to become a metastable intermediate; 3) Injecting air instantly, the intermediate spontaneously combusts upon contact with air, and the product is a composite of boron-nickel alloy and metallic nickel, namely, the Ni3B / Ni nickel-based catalyst material.

2. The method according to claim 1, characterized in that The nickel salt is one of nickel sulfate, nickel nitrate and nickel chloride.

3. The method according to claim 1, characterized in that The precursor is prepared by hydrothermal treatment of nickel nitrate, boric acid and sodium hydroxide.

4. The precursor method according to claim 1, characterized in that The precursor has a morphology of flake, spherical or rod.

5. The method according to claim 1, wherein There is no limit to the speed of injecting air, but in order to complete the reaction, the intermediate needs to be spread as much as possible so that it can fully contact with the air.

6. The method according to claim 1, characterized in that During the vacuum treatment, appropriately increasing the temperature is beneficial to the rapid removal of crystal water so that the sample reaches a metastable state.

7. Use of a nickel-based catalyst material prepared by the method according to any one of claims 1 to 6, characterized in that: The nickel-based catalyst material is used in the preparation of formic acid by electrocatalytic oxidation of methanol.

8. The use of the nickel-based catalyst material according to claim 7, characterized in that: The nickel-based catalyst material is loaded on a conductive carrier to play a role. The conductive carrier is one of a glassy carbon electrode, a nickel mesh, a copper mesh, a carbon cloth, and a carbon felt.

9. The use of the nickel-based catalyst material according to claim 7, characterized in that: The obtained nickel-based catalyst material was used directly as a catalyst.

Images