阅读说明：本技术 硼掺杂银纳米海绵状电化学合成氨催化剂及其制备方法 (boron-doped silver nano spongy catalyst for electrochemical synthesis of ammonia and preparation method thereof ) 是由 王鸿静 李英豪 *** 许友 王亮 于 2019-08-22 设计创作，主要内容包括：一种硼掺杂银纳米海绵状电化学合成氨催化剂,由如下方法制备：分别配浓度在0.01～1.0M之间的硝酸银和硼氢化钠的N、N-二甲基甲酰胺(DMF)溶液和水溶液；取1.0mL浓度为0.01～1.0M之间的硝酸银的DMF溶液和水溶液,然后加入到5.0mL浓度为0.01～1.0M之间的硼氢化钠的DMF溶液和水溶液,分别在冰水浴和常温条件下搅拌反应1.5～2.5小时,洗涤、离心、干燥,得到所述硼掺杂的银纳米海绵状催化剂。以及提供一种硼掺杂银纳米海绵状电化学合成氨催化剂的制备方法。本发明制备工艺简单,反应时间短,在低温常压下,制得的材料具有优异的电化学氮气还原性能。(a boron-doped silver nano spongy catalyst for electrochemical synthesis of ammonia is prepared by the following steps: respectively preparing N, N-Dimethylformamide (DMF) solution and aqueous solution of silver nitrate and sodium borohydride with the concentration of 0.01-1.0M; taking 1.0mL of a DMF (dimethyl formamide) solution of silver nitrate and an aqueous solution of silver nitrate with the concentration of 0.01-1.0M, adding 5.0mL of DMF solution of sodium borohydride and an aqueous solution of sodium borohydride with the concentration of 0.01-1.0M, respectively stirring and reacting for 1.5-2.5 hours in an ice water bath at normal temperature, washing, centrifuging and drying to obtain the boron-doped silver nano sponge catalyst. And provides a preparation method of the boron-doped silver nano spongy catalyst for electrochemical synthesis of ammonia. The preparation method is simple in preparation process and short in reaction time, and the prepared material has excellent electrochemical nitrogen reduction performance at low temperature and normal pressure.)

1. The electrochemical synthesis ammonia catalyst is characterized by being prepared by the following steps:

(1) Respectively preparing N, N-dimethylformamide DMF solution and aqueous solution of silver nitrate and sodium borohydride with the concentration of 0.01-1.0M;

(2) Taking 1.0mL of a DMF (dimethyl formamide) solution of silver nitrate and an aqueous solution of silver nitrate with the concentration of 0.01-1.0M, adding 5.0mL of DMF solution of sodium borohydride and an aqueous solution of sodium borohydride with the concentration of 0.01-1.0M, respectively stirring and reacting for 1.5-2.5 hours in an ice water bath at normal temperature, washing, centrifuging and drying to obtain the boron-doped silver nano spongy electrochemical synthesis ammonia catalyst.

2. The method for preparing the boron-doped silver nanosponge-like electrochemical synthesis ammonia catalyst according to claim 1, characterized in that the method comprises the following steps:

(1) respectively preparing N, N-dimethylformamide DMF solution and aqueous solution of silver nitrate and sodium borohydride with the concentration of 0.01-1.0M;

(2) taking 1.0mL of a DMF (dimethyl formamide) solution of silver nitrate and an aqueous solution of silver nitrate with the concentration of 0.01-1.0M, adding 5.0mL of DMF solution of sodium borohydride and an aqueous solution of sodium borohydride with the concentration of 0.01-1.0M, respectively stirring and reacting for 1.5-2.5 hours in an ice water bath at normal temperature, washing, centrifuging and drying to obtain the boron-doped silver nano spongy electrochemical synthesis ammonia catalyst.

3. the method of claim 2, wherein the reaction temperature, the concentration and volume of sodium borohydride and silver nitrate are controlled to control the morphology and structure of Ag and boron doped Ag.

Technical Field

The invention relates to a boron-doped silver nano spongy catalyst for electrochemical synthesis of ammonia and a preparation method thereof, and the catalyst can be used for research on electro-catalytic nitrogen reduction reaction.

background

ammonia (NH)₃) Is an important synthetic chemical substance and has wide application in the fields of chemical fertilizers, textiles, medicines and the like. And, NH₃Is considered to be a promising carbon-free energy carrier, has high hydrogen content and is convenient to store and transport. At present, the conventional Haber-Bosch process is carried out in NH₃In which N is a large proportion₂And H₂The reaction is carried out on an iron-based or ruthenium-based catalyst under the harsh reaction conditions of 400-600 ℃, 150-350atm and the like. Due to N₂Is more than 1% of the annual global energy supply for the production of NH₃. At the same time, H required for the reaction₂mainly from fossil fuels, which results in large amounts of CO₂And (5) discharging. In order to reduce energy consumption and greenhouse gas emissions, there is an urgent need to develop an environmentally friendly, sustainable method for ammonia production to meet the ever-increasing social needs. In recent years, electrocatalytic nitrogen reduction (NRR) has been considered as a desirable alternative to the synthesis of artificial ammonia, which can be driven at ambient temperature and pressure with renewable electrical power.

Currently, the key to NRR is the development of highly efficient electrocatalysts that can break strong N ≡ N triple bonds and suppress competitive Hydrogen Evolution Reactions (HER). Although a great deal of theoretical and experimental research has been conducted in developing noble metal-based NRR electrocatalysts, their low NH content₃The yield and the faraday efficiency are far from being applied to the industrial field. Researches show that the catalytic performance of the noble metal-based electrocatalyst is closely related to the morphology and the composition of the noble metal-based electrocatalyst. Porous nanostructures with interconnected nanoscale frameworks and large spaces have attracted extensive research interest, which not only provide large specific surface areas and abundant active sites, promote the activity of the catalyst, but also prevent the aggregation of the catalyst. The addition of another element to the noble metal catalyst can change the activation energy of the intermediate by transfer of the d-band center or by electron strain effects. In recent years, boron doping in carbon materials can redistribute the electron density of boron and carbon due to their different electronegativities, the electron deficient boron site pair N₂the binding ability of (c) is enhanced. Based on the idea, the development of a simple and efficient method for synthesizingBoron doped porous noble metal catalyst to enhance electrochemical NH₃The production of (1).

Disclosure of Invention

The invention aims to provide a controllable preparation method of a boron-doped silver nano spongy catalyst for electrochemical synthesis of ammonia and research on an electro-catalytic nitrogen reduction reaction.

The technical scheme adopted by the invention is as follows:

A boron-doped silver nano spongy catalyst for electrochemical synthesis of ammonia is prepared by the following steps:

(1) Respectively preparing N, N-dimethylformamide DMF solution and aqueous solution of silver nitrate and sodium borohydride with the concentration of 0.01-1.0M;

(2) taking 1.0mL of a DMF (dimethyl formamide) solution of silver nitrate and an aqueous solution of silver nitrate with the concentration of 0.01-1.0M, adding 5.0mL of DMF solution of sodium borohydride and an aqueous solution of sodium borohydride with the concentration of 0.01-1.0M, respectively stirring and reacting for 1.5-2.5 hours in an ice water bath at normal temperature, washing, centrifuging and drying to obtain the boron-doped silver nano spongy electrochemical synthesis ammonia catalyst.

In the invention, the selection of reaction conditions has important influence on the structure of the catalyst for preparing the boron-doped silver nano spongy electrochemical synthesis ammonia, and DMF is added in the reaction by utilizing the DMF to Na⁺Has stronger solvation effect, improves BH4^-Stability in DMF solution, which facilitates tunable decomposition and deposition of B atoms on Ag surfaces. NaBH₄Are reducing agents and dopants. In the preparation process, the morphology and the structure of Ag can be controlled by changing the adding proportion of the precursor.

A preparation method of a boron-doped silver nano spongy catalyst for electrochemical synthesis of ammonia comprises the following steps:

(1) Respectively preparing N, N-dimethylformamide DMF solution and aqueous solution of silver nitrate and sodium borohydride with the concentration of 0.01-1.0M;

(2) Taking 1.0mL of a DMF (dimethyl formamide) solution of silver nitrate and an aqueous solution of silver nitrate with the concentration of 0.01-1.0M, adding 5.0mL of DMF solution of sodium borohydride and an aqueous solution of sodium borohydride with the concentration of 0.01-1.0M, respectively stirring and reacting for 1.5-2.5 hours in an ice water bath at normal temperature, washing, centrifuging and drying to obtain the boron-doped silver nano spongy electrochemical synthesis ammonia catalyst.

Further, the concentration and volume of silver nitrate and sodium borohydride and the reaction temperature are controlled to control the morphology and structure of Ag.

Carrying out electrochemical catalytic nitrogen reduction reaction at normal temperature and normal pressure, wherein the specific performance test operation process is as follows:

(1) Weighing about 5mg of catalyst, dispersing the catalyst in ultrapure water, adding 100 mu L of Nafion solution (5 wt%), performing ultrasonic treatment for 30 minutes to obtain uniform dispersion liquid, and coating 10-50 mu L of the dispersion liquid on carbon paper (0.5 multiplied by 0.5 cm)²) Drying at 50 ℃;

(2) the experiment for preparing ammonia by nitrogen reduction was carried out using catalyst-loaded carbon paper as an electrode material. In an H-cell, carbon paper was used as the working electrode, and a saturated Ag/AgCl electrode and a carbon rod were used as the reference electrode and the counter electrode, respectively. Before testing, nitrogen gas is introduced for 30 minutes to saturate the solution with nitrogen gas, test programs of linear sweep cyclic voltammetry and chronoamperometry are selected, and the current condition of the working electrode under different potentials is monitored by a computer. And then testing the concentration of ammonia in the catalyzed electrolyte by an ultraviolet-visible spectrophotometer, and finally calculating the ammonia production rate and the Faraday efficiency of the catalyst.

The boron-doped silver nano spongy catalyst for electrochemical synthesis of ammonia and the preparation method thereof provided by the invention have the main beneficial effects that:

(1) The preparation method is simple and mild, the product is directly obtained by a one-step method, and the yield of the boron-doped silver nano spongy product is high.

(2) the morphology and structure of silver can be controlled by changing the concentration and volume of the precursor, thus the performance in nitrogen reduction application is different.

(3) the synthesized boron-doped silver nano spongy electrocatalyst shows outstanding activity and stability in the nitrogen reduction reaction, and the Ag nano material has a very high application prospect as the electrocatalyst.

Drawings

fig. 1 is an SEM image of a boron-doped silver nanosponge-like electrochemical synthesis ammonia catalyst according to embodiment 1 of the present invention.

fig. 2 is TEM and HRTEM images of boron-doped silver nanosponges electrochemical synthesis ammonia catalyst according to embodiment 1 of the present invention.

fig. 3 is an XRD chart of the electrochemical synthesis ammonia catalyst in the form of boron-doped silver nanosponges according to embodiment 1 of the present invention.

Fig. 4 is an XPS chart of the electrochemical synthesis ammonia catalyst in the form of boron-doped silver nano sponge according to embodiment 1 of the present invention.

FIG. 5 is a linear cyclic voltammogram of the boron-doped silver nanosponges electrochemical ammonia synthesis catalyst in 0.1M HCl solution according to example 1 of the present invention.

fig. 6 is a diagram of the catalytic performance of the boron-boron doped silver nano sponge-like electrochemical ammonia synthesis catalyst according to embodiment 1 of the present invention.

Fig. 7 is an SEM image of the silver nanosponge-like electrochemical ammonia synthesis catalyst according to embodiment 2 of the present invention.

Fig. 8 is a diagram of the catalytic performance of the silver nanosponge-like electrochemical ammonia synthesis catalyst according to embodiment 2 of the present invention.

Fig. 9 is an SEM image of boron-doped silver nanoparticles according to embodiment 3 of the present invention.

Detailed Description

The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto.

referring to fig. 1 to 9, in this embodiment, the catalytic performance test of the silver nano sponge-like electrochemical synthesis ammonia catalyst and the boron-doped silver nano sponge-like electrochemical synthesis ammonia catalyst is performed on a CHI 660E electrochemical workstation, and the operation process is as follows:

First, about 5mg of the catalyst was weighed and dispersed in 0.9mL of ultrapure water, then 100. mu.L of Nafion solution (5 wt%) was added, and ultrasonic treatment was performed for 30 minutes to obtain a uniform dispersion, and then 50. mu.L of the dispersion was coated on carbon paper (0.5X 0.5 cm)²) Drying at 50 ℃;

And secondly, taking the carbon paper loaded with the catalyst as an electrode material, and carrying out an experiment for preparing ammonia by nitrogen reduction. Before testing, nitrogen gas is introduced for 30 minutes to saturate the solution with nitrogen gas, test programs of linear sweep cyclic voltammetry and chronoamperometry are selected, and the current condition of the working electrode under different potentials is monitored by a computer. And then testing the concentration of ammonia in the catalyzed electrolyte by an ultraviolet-visible spectrophotometer, and finally calculating the ammonia production rate and the Faraday efficiency of the catalyst.