CN-121976298-A - Preparation of layered nickel molybdenum oxygen cluster crystal and application of layered nickel molybdenum oxygen cluster crystal in preparing ammonia by catalyzing nitrate reduction

Abstract

The invention relates to a layered nickel molybdenum oxygen cluster crystal, a preparation method thereof and application of electrocatalytic nitrate reduction to ammonia production. The chemical formula of the crystal is [Ni(H 2 O) 3 ] 4 [Ni(H 2 O) 6 ] 2 [P 28 Mo 16 Ni 20 O 170 ] 2 ·20H 2 O,, the crystallographic parameters are orthorhombic system, space group Cccm, unit cell parameters a= 23.9730 (16) a, b= 36.550 (3) a, c= 20.4477 (15) a, α=90°, β=90°, γ=90°, v=17916 (2) a 3. The preparation adopts a one-step hydrothermal synthesis method, sodium molybdate and nickel chloride are dispersed in an ethanol-water system, phosphoric acid is added to adjust the pH value, and the mixture reacts for 3 days at a constant temperature of 160 ℃ to obtain yellow flaky crystals which have a unique two-dimensional lamellar stacking structure. After the catalyst is prepared into a working electrode, the catalyst shows good performance in an electrocatalytic nitrate reduction ammonia preparation reaction, the Faraday efficiency can reach 75.20% under the potential of minus 0.9V vs. RHE, and the ammonia yield is 10.51: 10.51 mg h ‑1 mg ‑1 cat. , and has high catalytic activity, selectivity and structural stability. The invention provides a novel high-efficiency catalyst for green low-carbon synthetic ammonia and wastewater recycling treatment, and has wide application prospect.

Inventors

• WANG XINMING
• LIU CHENGXU
• LUO HUI
• ZHAO NAN
• PANG HAIJUN

Assignees

• 哈尔滨理工大学

Dates

Publication Date

20260505

Application Date

20260131

Claims (4)

1. 1. A layered nickel-molybdenum-oxygen cluster crystal is characterized in that a [Ni(H 2 O) 3 ] 4 [Ni(H 2 O) 6 ] 2 [P 28 Mo 16 Ni 20 O 170 ] 2 ·20H 2 O, metal center molybdenum atom exists in a hexacoordinated MoO 6 octahedral form, and a nickel atom is used as a bridging metal and is responsible for connecting different MoO 6 units and interacts with a P atom to form a two-dimensional annular structure to form a basic structural unit. The different basic structural units are bridged by Ni atoms and P atoms, each P atom of the phosphorus atoms is bonded with 4O atoms, and the O atoms are connected to surrounding Mo atoms as bridging oxygen to form the layered nickel-molybdenum-oxygen cluster crystal by coaction.
2. 2. The layered nickel molybdenum oxide cluster crystal of claim 1, characterized in that it belongs to an orthorhombic system, the space group is Cccm, the unit cell parameters are a= 23.9730 (16) a, b= 36.550 (3), c= 20.4477 (15) a, α=90 °, β=90 °, γ=90 °, v=17916 (2) a 3 .
3. 3. A method for preparing the layered nickel molybdenum oxygen cluster crystal according to claim 1 or 2, comprising the steps of: adding sodium molybdate and nickel chloride into ethanol according to the molar ratio of 1.39 (1.0-1.2), stirring for 10min, adding distilled water, stirring for 10min, adding 1.72 mL phosphoric acid, stirring for 20min, regulating the pH value of the suspension to 4.1-4.3, obtaining a reaction solution with the pH value of 4.1-4.3, placing the obtained reaction mixture into a closed reactor, reacting for 3 days at 160 ℃, and cooling, washing and drying after the reaction is finished, thus obtaining the layered nickel-molybdenum oxygen cluster crystal.
4. 4. The use of a layered nickel molybdenum oxygen cluster crystal produced by the production method of claim 1, characterized in that the crystal material is used as an electrode material for electrocatalytic nitrate reduction synthesis of ammonia at normal temperature and pressure.

Description

Preparation of layered nickel molybdenum oxygen cluster crystal and application of layered nickel molybdenum oxygen cluster crystal in preparing ammonia by catalyzing nitrate reduction Technical Field The invention belongs to the technical field of electrocatalytic materials, and particularly relates to preparation of layered nickel molybdenum oxygen cluster crystals and application of catalyzing nitrate reduction to ammonia production, which are particularly suitable for environment-friendly low-carbon synthetic ammonia and wastewater recycling treatment scenes. Background Ammonia (NH 3) is an indispensable nitrogenous fertilizer core raw material for modern agriculture, and has important strategic value in future energy systems as a potential clean energy medium such as a hydrogen energy carrier, a fuel cell fuel and the like. The inherent drawbacks of the traditional synthesis of ammonia, which relies on the Haber-Bosch process, have been increasingly highlighted since the beginning of the 20 th century, are that the reaction needs to be carried out under extreme conditions of 400-500 ℃ and 15-25 MPa, consuming about 1% -2% of fossil energy worldwide, with about 1.9 tons of CO 2 emissions per 1 ton of ammonia produced. Therefore, development of a low-carbon ammonia synthesis technology driven by renewable energy at normal temperature and normal pressure is urgent. The electrocatalytic nitrate reduction ammonia synthesis (NO 3 RR) technology takes nitrate (NO 3-) widely existing in industrial wastewater and agricultural runoff as a raw material, converts NO 3 -into NH 3 through electrocatalytic reaction at normal temperature and normal pressure, has dual values of pollution control and resource recovery, and is considered to be one of the most potential paths for replacing the Haber-Bosch process. However, the NO 3 RR reaction involves a complex multi-electron transfer process, byproducts such as NO 2-、N2 and the like are easy to generate, so that ammonia selectivity is low, faraday efficiency is poor, meanwhile, the electrocatalyst needs to have excellent electron transmission capability and a stable structure, and the problems of insufficient active sites, poor stability, poor conductivity, difficult selectivity regulation and the like of the existing catalyst (such as noble metal base, transition metal oxide and traditional polyacid material) generally exist, so that the industrial application of the technology is limited. The poly metal oxygen cluster (POM) is used as a nano metal oxygen cluster with a definite structure, has an atomically adjustable composition and excellent oxidation-reduction performance, and is an ideal candidate material for electrocatalytic reaction. However, most of the traditional multi-acid-base catalysts have zero-dimensional/low-dimensional structures, are easy to agglomerate and dissolve in the electrocatalytic process, and have insufficient stability, and the structure-activity relationship between the structure and the catalytic performance is not clear, so that the directional design and the performance optimization are difficult to realize. Therefore, the development of a novel multi-metal oxygen cluster-based catalyst with a unique layered structure, high stability and high selectivity has important significance for promoting the industrialization of the NO 3 RR technology. At present, the preparation of layered nickel molybdenum oxygen cluster crystals and the application thereof in the preparation of ammonia from NO 3 RR have not been reported in the literature and patents. Disclosure of Invention Aiming at the technical defects of poor stability, limited catalytic activity and selectivity, ambiguous structure-activity relationship and the like of the conventional multi-acid-base electrocatalyst in the ammonia production reaction by nitrate reduction, the invention provides a preparation method and application of a layered nickel-molybdenum-oxygen cluster crystal, and a layered crystal with an atomic-scale precise structure is constructed by a one-step hydrothermal method, so that the cooperative promotion of catalytic activity, selectivity and stability is realized. In order to achieve the above purpose, the present invention adopts the following technical scheme: 1. adding sodium molybdate and nickel chloride into ethanol, stirring for 10 min, adding distilled water, stirring for 10 min, adding phosphoric acid, stirring for 20 min, and finally adjusting the pH value of the suspension to 4.1-4.3 to obtain a target reaction solution; The molar ratio of the sodium molybdate to the nickel chloride in the first step is 1.39 (1.0-1.2), and the volume ratio of the sodium molybdate to the distilled water in the first step is 3.512mmol to 40 mL; 2. transferring the reaction solution prepared in the first step into a polytetrafluoroethylene reaction kettle (with the volume of 25 mL), sealing, placing in an oven, carrying out constant-temperature reaction for 3 days at 160 ℃