CN110813271A - Improved BaTiO3Preparation method of active catalyst for producing ammonia by sunlight nitrogen reduction - Google Patents

Abstract

The invention discloses an improved BaTiO₃A preparation method of an active catalyst for producing ammonia by reducing sunlight nitrogen belongs to the technical field of preparation and application of nanometer materials. Oxygen defect is introduced into perovskite structure semiconductor BaTiO with stable structure, narrow forbidden band, wide light absorption wavelength range and high solar energy utilization rate₃The formed oxygen vacancy provides more active sites for reactants, enhances electron transfer, enables the reaction to be quicker and more active, generates more reaction products, and enables the catalyst to exert the highest performance by controlling the number of the oxygen vacanciesCatalytic efficiency. By NH per unit time₃The yield is used for evaluating the catalytic performance, and whether the catalyst is deactivated after the reaction is finished and the recycling condition of the catalyst can be determined. The method is simple, environment-friendly and low in cost; the catalyst has the advantages of obvious catalytic effect, rapid reaction, high repeatability and the like; the catalyst has potential application value in photocatalytic nitrogen reduction to produce ammonia.

Description

Improved BaTiO3Preparation method of active catalyst for producing ammonia by sunlight nitrogen reduction

Technical Field

The invention belongs to the field of preparation and application of nano materials, and particularly relates to sodium borohydride (NaBH)₄) Reducing BaTiO₃Improvement of BaTiO by introducing oxygen defect₃A preparation method of an active catalyst for producing ammonia by reducing sunlight nitrogen.

Background

With the development of industry, the increasingly exhausted energy reserves and the increasingly severe environmental pollution are two major challenges to be faced. Fossil energy has been consumed as a main energy source for a long time, and it has been difficult to satisfy a long-term energy supply, and on the other hand, fossil fuel is combusted to generate energy and simultaneously generate a large amount of CO₂、SO₂And the like, which brings pollution problems of greenhouse effect and the like. Therefore, how to solve the above two problems has important strategic significance on realizing sustainable development and maintaining harmony of ecological environment, and developing and using clean renewable energy is an effective way to solve the two problems. Sunlight is the most abundant and sustainable energy source for human society. People have proposed a solar cell technology for converting solar energy into electricity, a photothermal conversion technology for converting light energy into heat energy, and a photoelectrochemical technology for converting light energy into chemical energy by artificially simulating photosynthesis. Ammonia (NH)₃) Is an important synthetic chemical feedstock for fertilizers and non-carbon based energy carriers that is an important energy crisis in the future, and its increased consumption (about 1500WT annually) is a key requirement for social development and population growth [1]. In the global nitrogen cycle, the conversion of most ammonia is a biosynthesis by nitrogen-fixing bacteria in nature. However, the biogeochemical nitrogen fixation technology has uncertainty and unreliability, and can hardly meet the huge demand of the current fertilizer industry. The first large-scale synthetic nitrogen fixation process developed by Fritz Haber and Carl Bosch in BASF at the beginning of the 20 th century [2]. Over a hundred yearsThe ammonia synthesis industry remains insisting on the use of the Haber-Bosch process, typically carried out at high pressures (150-350atm), high temperatures (350-550℃.) and plant power requirements, in the synthesis process and associated raw materials (e.g., hydrogen extraction from fossil fuels), and so far, essentially the original iron or ruthenium based catalysts and processes have been used, with only hydrogen and nitrogen being produced and purified. Despite the growing global population and the high degree of nutrient dependence on fertilizers, the traditional industrial ammonia production consumes 1-3% of the global energy supply, and this process results in 1.6-3% of the global greenhouse gas emissions of carbon dioxide 3]. Therefore, the development of an environmentally friendly, low energy, efficient, mild nitrogen fixation strategy to achieve ammonia synthesis is the leading edge and hot spot of current chemical and catalytic research [4 ]]. However, such a system still faces a number of challenges such as: how to overcome BaTiO₃The wide-bandgap semiconductor has the characteristics of expanding the spectral response range, reducing the high recombination rate of photo-generated electrons and holes, accelerating the diffusion rate of hot carriers and the like. The patent develops a simple and easy synthetic route to prepare NaBH₄Reducing BaTiO₃Improvement of BaTiO by introducing oxygen defect₃Active catalyst for producing ammonia by sunlight nitrogen reduction. More active sites are increased and the reaction rate is improved by adjusting the content of oxygen vacancies; by mixing in BaTiO₃The semiconductor photocatalysis system with oxygen defect introduced to the surface can obtain high-efficiency charge separation efficiency and photocatalytic nitrogen reduction for ammonia production.

1.Canfield,D.E.,A.N.Glazer,andP.G.Falkowski,The evolutionandfutureofEarth’snitrogen cycle.science,2010.330(6001):p.192-196.

2.Licht,S.,et al.,Ammonia synthesis by N2 and steam electrolysis inmolten hydroxide suspensions of nanoscaleFe2O3.Science,2014.345(6197):p.637-640.

3.Mukherjee,S.,et al.,Metal-organic framework-derived nitrogen-dopedhighly disordered carbon for electrochemicalammoniasynthesis usingN2 andH2Oin alkaline electrolytes.Nano Energy,2018.48:p.217-226.

4.Chen,X.,et al.,Photocatalyticfixation ofnitrogen to ammonia:state-of-the-art advancements andfuture prospects.MaterialsHorizons,2018.5(1):p.9-27.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides sodium borohydride (NaBH)₄) Reducing BaTiO₃Improvement of BaTiO by introducing oxygen defect₃The preparation method of the active catalyst for producing ammonia by the reduction of nitrogen in sunlight is simple and easy to implement, the yield is higher, and the prepared oxygen-deficient BaTiO is₃The catalyst has better function of catalyzing nitrogen reduction by sunlight to generate ammonia.

The purpose of the invention is realized as follows: the method specifically comprises the following steps:

step one, BaTiO is added₃Mixing with 300mg of sodium borohydride, and uniformly grinding for 1h to obtain a mixed sample A;

step two, transferring the mixed sample A into a tubular furnace protected by argon, heating to 300 ℃ at the speed of 10 ℃/min, calcining the mixed sample A for 30 minutes, and cooling to room temperature to obtain a sample B;

step three, putting the obtained sample B into a 50mL centrifuge tube, adding 20mL deionized water, and standing for 36 hours to allow the sample B to react fully; and after the reaction, carrying out centrifugal treatment on the sample, wherein the centrifugal rotation speed is 5000rpm, the centrifugal time is 3min, discarding the supernatant, washing the precipitate with deionized water, carrying out ultrasonic treatment for 3min, repeating the centrifugal and deionized water washing processes once, centrifuging again, and draining under natural conditions to form the BaTiO3 nanostructure catalyst with the introduced oxygen defect.

1. The reagent dosage in the above steps can not be scaled up.

2. The reagents in the above steps are all analytically pure and are not further processed.

The invention has the following advantages and positive effects:

1. the catalyst synthesized by the method has high sample purity, simple and advanced synthesis process, and BaTiO with introduced oxygen defect for the first time₃Increasing active sites improves BaTiO₃The nitrogen is reduced by sunlight to generate ammonia activity.

2. The method is simple, environment-friendly and low in cost; the detection is rapid and the repeatability is high; has wide application prospect in reducing nitrogen to produce ammonia under the sunlight condition.

Drawings

FIG. 1 shows BaTiO with oxygen defect introduced therein according to the present invention₃A photocatalyst XRD pattern;

FIG. 2 shows BaTiO with oxygen defect introduced therein according to the present invention₃A photocatalyst solid ultraviolet diffuse reflectance pattern;

FIG. 3 shows BaTiO with oxygen defect introduced therein according to the present invention₃Photocatalyst TEM images and high resolution TEM images;

FIG. 4 shows BaTiO with oxygen defect introduced therein according to the present invention₃The photocatalyst photocatalysis nitrogen fixation performance is shown schematically.

Detailed Description

Specific embodiments of the present invention are described in detail below with reference to the accompanying drawings:

improved BaTiO₃The preparation method of the active catalyst for producing ammonia by sunlight nitrogen reduction comprises the following steps: the preparation method comprises the following steps:

step one, BaTiO is added₃Mixing with 300mg of sodium borohydride, and uniformly grinding for 1h to obtain a mixed sample A;

step two, transferring the mixed sample A into a tubular furnace protected by argon, heating to 300 ℃ at the speed of 10 ℃/min, calcining the mixed sample A for 30 minutes, and cooling to room temperature to obtain a sample B;

step three, putting the obtained sample B into a 50mL centrifuge tube, adding 20mL deionized water, and standing for 36 hours to allow the sample B to react fully; centrifuging the sample after reaction at the centrifugal speed of 5000rpm for 3min, discarding the supernatant, washing the precipitate with deionized water, performing ultrasonic treatment for 3min, repeating the above centrifuging and deionized water washing processes, centrifuging again, and draining under natural conditions to obtain BaTiO with oxygen defect₃A nanostructured catalyst.

The oxygen-containing vacancy BaTiO prepared by the method is characterized by adopting X-ray diffraction (XRD), solid ultraviolet diffuse reflection, a transmission electron microscope and a high-resolution transmission electron microscope₃A photocatalyst.

As can be seen from fig. 1: diffraction peaks thereof all show BaTiO₃Single perovskite junction of tetragonal phaseAnd (5) forming.

As can be seen from fig. 2: oxygen deficient BaTiO₃The light absorption ability of (a) is closely related to the surface defect state.

As can be seen from fig. 3: oxygen deficient BaTiO₃The particles are uniform, the particle size is about 50nm, the particles are in an irregular spherical shape, the lattice stripe spacing is 0.405nm, and the particles have good (100) crystal faces.

As can be seen from fig. 4: oxygen deficient BaTiO₃After 4 times of nitrogen fixation, the catalyst still maintains higher catalytic activity, which indicates that the catalyst has good stability.

Claims (1)

1. Improved BaTiO₃The preparation method of the active catalyst for producing ammonia by reducing sunlight nitrogen is characterized by comprising the following steps: the method comprises the following steps:

step one, BaTiO is added₃Mixing with 300mg of sodium borohydride, and uniformly grinding for 1h to obtain a mixed sample A;

step two, transferring the mixed sample A into a tubular furnace protected by argon, heating to 300 ℃ at the speed of 10 ℃/min, calcining the mixed sample A for 30 minutes, and cooling to room temperature to obtain a sample B;

step three, putting the obtained sample B into a 50mL centrifuge tube, adding 20mL deionized water, and standing for 36 hours to allow the sample B to react fully; centrifuging the sample after reaction at the centrifugal speed of 5000rpm for 3min, discarding the supernatant, washing the precipitate with deionized water, performing ultrasonic treatment for 3min, repeating the above centrifuging and deionized water washing processes, centrifuging again, and draining under natural conditions to obtain BaTiO with oxygen defect₃A nanostructured catalyst.

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