阅读说明：本技术 一种碳化铁复合一氧化钛的纳米颗粒光热催化剂及其制备 (Iron carbide and titanium monoxide compounded nanoparticle photo-thermal catalyst and preparation thereof ) 是由 闵宇霖 郝敬轩 魏泺骥 时鹏辉 范金辰 徐群杰 朱晟 于 2020-03-10 设计创作，主要内容包括：本发明涉及一种碳化铁复合一氧化钛的纳米颗粒光热催化剂及其制备,首先将P25,PAN,DMF,硝酸铁混合后烘干,在氨气氛围下800～850℃煅烧4小时,取出样品后研磨成粉末,得到碳化铁复合一氧化钛的纳米颗粒光热催化剂,其具有宽的光吸收范围,高产甲烷性能,低电阻率,快速转移载流子的能力,高光生载流子分离能力,低载流子重组率,以及良好的二氧化碳还原高循环稳定性等特点,其用于光热催化二氧化碳还原甲烷,速率最高可达37.67μmol·g<Sup>-1</Sup>·h<Sup>-1</Sup>。其制备方法具有操作简单,成本低廉,所用原材料无毒,符合环保理念的生产。(The invention relates to a nanoparticle photo-thermal catalyst of iron carbide composite titanium monoxide and a preparation method thereof, wherein P25, PAN, DMF and ferric nitrate are mixed and dried, calcined for 4 hours at 800-850 ℃ in an ammonia atmosphere, a sample is taken out and ground into powder to obtain the nanoparticle photo-thermal catalyst of iron carbide composite titanium monoxide, which has the characteristics of wide light absorption range, high methane yield, low resistivity, capability of quickly transferring carriers, high photo-generated carrier separation capability, low carrier recombination rate, good carbon dioxide reduction high cycle stability and the like, and is used for photo-thermal catalysisThe methane is reduced by the thermal catalysis of the carbon dioxide, and the speed can reach 37.67 mu mol g at most ‑1 ·h ‑1 . The preparation method has the advantages of simple operation, low cost, nontoxic raw materials and production according with the environmental protection concept.)

1. A preparation method of a nanoparticle photo-thermal catalyst of iron carbide compounded with titanium monoxide is characterized by comprising the following steps:

(1) dissolving PAN in a DMF solution, heating overnight, adding ferric nitrate nonahydrate, stirring uniformly to obtain an orange yellow solution, adding titanium dioxide P25, stirring for reaction, and drying;

(2) putting the dried sample obtained in the step (1) into NH₃And (3) heating and calcining under the atmosphere to obtain a blocky product, and grinding the blocky product into powder to obtain the target product.

2. The method for preparing nanoparticle photo-thermal catalyst of iron carbide compounded with titanium monoxide as claimed in claim 1, wherein in the step (1), the addition ratio of PAN, ferric nitrate nonahydrate and titanium dioxide P25 is 0.8 g: (1-3) mmol: (0.03-0.05) g.

3. The method for preparing nanoparticle photo-thermal catalyst of iron carbide and titanium monoxide as claimed in claim 1, wherein in step (1), the concentration of DMF solution is 99.5%, and the ratio of DMF solution to PAN addition is 10 mL: 0.8 g.

4. The method for preparing nanoparticle photo-thermal catalyst of iron carbide compounded with titanium monoxide as claimed in claim 1, wherein in the step (1), the overnight heating process conditions are as follows: heated in an oil bath at 60 ℃ overnight.

5. The method for preparing nanoparticle photo-thermal catalyst of iron carbide compounded with titanium monoxide as claimed in claim 1, wherein in the step (1), the stirring reaction time is 24 h.

6. The method for preparing nanoparticle photo-thermal catalyst of iron carbide compounded with titanium monoxide as claimed in claim 1, wherein the drying temperature in step (1) is 60 ℃.

7. The preparation method of the nanoparticle photo-thermal catalyst of iron carbide and titanium monoxide as claimed in claim 1, wherein the temperature-rising calcination process conditions are as follows: heating to 800-850 ℃ at a heating rate of 2 ℃/min, and calcining for 3-4 h.

8. A nanoparticle photo-thermal catalyst of iron carbide compounded with titanium monoxide, which is prepared by the preparation method of any one of claims 1 to 7, and has a particle size of 5 to 10 nm.

Technical Field

The invention belongs to the technical field of photocatalytic materials, and relates to a nanoparticle photo-thermal catalyst of iron carbide and titanium monoxide and a preparation method thereof.

Background

With the rapid development of the global population and the world economy, the demand of human beings for fossil energy is increasing. However, the increasing exhaustion of fossil fuels such as petroleum, coal, and natural gas, and the climate change caused by global greenhouse effect, the development of renewable clean energy is urgent. Chemical reduction is a key process of the earth's carbon cycle and is the developing direction of future solar energy capture and storage technologies. Photosynthesis converts carbon dioxide into carbohydrates, maintaining almost all life on earth. Inspired by this, researchers have attempted to develop photosynthetic simulation systems to reduce carbon dioxide to fuels and valuable chemical feedstocks. However, limiting the current stage of photocatalytic CO₂Depending on three main factors: (1) the photocatalyst absorbs solar energy of a wider spectrum; (2) efficient separation and transfer of photogenerated carriers (electron-hole pairs); (3) the surface of the photocatalyst effectively catalyzes oxidation-reduction reaction. Ti-based materials are currently the most studied catalytic materials in the field of photocatalysis. Photocatalytic TiO has been discovered since 1972 by Honda and Fujishima et al₂After water is photolyzed by the single crystal electrode, a large number of Ti-based materials are widely studied. However, since conventional TiO2 photocatalysts cannot absorb visible light or even near infrared light, and since TiO₂The conduction band potential of the carbon nanotube is too low (-0.1eVvsNHE), and the carbon nanotube is far from meeting the requirement of CO₂Reduction to CO (-0.52eV vs NHE) or CH₄Potential of (-0.24eV vs NHE), and thus for the modified Ti-based materials for the reduction of CO₂Is highly desirable. Generally, four typical strategies are employed to improve their catalytic capacity: (1) Doping a semiconductor with noble metal/non-noble metal; (2) compounding two different semiconductors to form a multi-band gap material; (3) the optimal crystal face of the catalytic reaction is exposed for improving the reaction efficiency; (4) oxygen vacancies are created by using low valence Ti oxides/nitrides to enhance photocatalytic performance.

However, the use of energy is very low because only the energy of light is used to excite the photo-generated electron-hole pairs, and most of the light energy is converted into heat energy during the whole process of illumination, and most of the heat energy is dissipated due to reaction, so that the overall utilization rate of sunlight is very low. Recently, a large number of researchers have started research on photothermal catalysis to achieve maximum utilization efficiency of sunlight. Fischer-tropsch synthesis (FTS) converts carbon monoxide from fossil fuels or biomass feedstocks into valuable hydrocarbons and oxygenates, and FTS has been used commercially for over 50 years. The most commonly used catalysts in FTS are the group VIIIB transition metals, especially iron, cobalt, nickel and ruthenium. The CO hydrogenation activity and product selectivity of these catalysts vary, and several of these metals are often used together (in alloy form) to achieve high CO conversion or to enhance selectivity to a particular product or group of products. Iron-based catalysts exhibit good initial selectivity to light olefins during FTS. During FTS, metallic iron is gradually converted to iron carbide during the reaction (this is considered to be the true active phase of the iron-based FTS catalyst). Iron carbide has relatively mild hydrogenation capability and the ability to promote C-C coupling reactions.

Disclosure of Invention

One of the purposes of the invention is to solve the technical problems of poor photocatalytic carbon dioxide reduction performance caused by limited light absorption range, few surface active sites, easy recombination of photon-generated carriers, low conduction band position and the like of the traditional Ti-based material serving as a photocatalytic material, and provide the iron carbide and titanium monoxide compounded nanoparticle photo-thermal catalyst which has the advantages of wide light absorption range, full light absorption range, difficult recombination of carriers and the like, and the catalyst has the advantages of wide light absorption range, full light spectrum, difficult recombination of carriers and the like at lambda>Under the irradiation of simulated sunlight with the wavelength of 420nm, the highest methane production rate can reach 37.67 mu mol.h^-1·g^-1。

The invention also aims to provide the preparation method of the nanoparticle photo-thermal catalyst for compounding the iron carbide and the titanium monoxide.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention provides a preparation method of a nanoparticle photo-thermal catalyst of iron carbide compounded with titanium monoxide, which comprises the following steps:

(1) dissolving PAN in a DMF solution, heating overnight, adding ferric nitrate nonahydrate, stirring uniformly to obtain an orange yellow solution, adding titanium dioxide P25, stirring for reaction, and drying;

(2) putting the dried sample obtained in the step (1) into NH₃And (3) heating and calcining under the atmosphere to obtain a blocky product, and grinding the blocky product into powder to obtain the target product.

Further, in the step (1), the ratio of the addition amounts of PAN, iron nitrate nonahydrate and titanium dioxide P25 was 0.8 g: (1-3) mmol: (0.03-0.05) g.

Further, in the step (1), the concentration of the DMF solution is 99.5% (mass fraction), and the ratio of the concentration to the addition amount of the PAN solution is 10 mL: 0.8 g.

Further, in the step (1), the process conditions for heating overnight are as follows: heated in an oil bath at 60 ℃ overnight.

Further, in the step (1), the reaction time is 24 hours under stirring.

Further, in the step (1), the drying temperature is 60 ℃.

Further, the process conditions of temperature-rising calcination are as follows: heating to 800-850 ℃ at a heating rate of 2 ℃/min, and calcining for 3-4 h.

In the invention, the ternary carbon bridge chain Fe is synthesized by a one-step burning method₂C/C/TiO complexes in NH₃Calcination was carried out at 800 ℃ in an atmosphere. The prepared composite nano-fiber is a stable photo-thermal catalyst and can effectively realize CO₂By photocatalytic reduction of (D), is suitable forUltraviolet-near infrared spectrum of solar radiation.

The whole synthesis process is as follows:

p25 is nanometer level photosensitive titanium dioxide, and its tiny particle is favorable to produce titanium monoxide by combining reaction with ammonia gas;

② since the reaction for synthesizing titanium monoxide needs carbon to participate in the process of reducing P25, the addition of Fe can combine Fe with C to form Fe₂C；

③ in the course of synthesis, due to the presence of PAN, under high temperature ignition in Fe₂The carbon layer is formed on the C/TiO, so that the specific surface area of the catalyst is increased

The second technical scheme of the invention provides a nanoparticle photo-thermal catalyst of iron carbide compounded with titanium monoxide, which is prepared by the preparation method and has the particle size of 5-10 nm.

The prepared catalyst has four elements of Fe, C, Ti and O, wherein the iron carbide and the titanium monoxide are in nanoparticle structures, the particle size is 5-10nm, the molybdenum nitride nanoparticles are loaded on the surface of the carbon nitride nanosheet layer, and P25 and Fe (NO) are contained in the nanoparticle photo-thermal catalyst of iron carbide compounded with the titanium monoxide₃)₃Amount of (c), as P25: fe (NO)₃)₃The mass ratio of (1): 10-30 is preferably 1: and (5) calculating the proportion of 20. The absorption range of the catalyst is full-spectrum absorption, the catalyst is used for preparing methane by photo-thermal catalytic reduction of carbon dioxide, and the methane production rate can reach 37.67 mu mol g at most under the irradiation of simulated sunlight with lambda being more than 420nm^-1·h^-1。

The iron carbide composite titanium monoxide nano-particles obtained by the invention are used as a novel photo-thermal catalyst, and have the following advantages in the application of photo-thermal catalytic carbon dioxide reduction:

the carbon substrate exists in the material, so that a larger specific surface area is provided, and the electron transmission rate is improved;

secondly, the material is beneficial to providing more active sites due to small particle size;

the titanium monoxide has stronger light absorption capacity as a novel titanium material;

the iron carbide as the transition metal carbide has high conductivity and is beneficial to the transmission of electrons, thereby promoting the generation of methane;

titanium monoxide has low resistance as a low-valence transition metal oxide, which is favorable for the transfer of current carriers, thereby promoting the generation of methane;

the titanium atom of titanium monoxide may serve as an active site for converting a proton into a methyl radical.

The method comprises the steps of mixing and drying P25, PAN, DMF and ferric nitrate, calcining for 4 hours at 800 ℃ in the atmosphere of ammonia gas, taking out a sample, and grinding the sample into powder to obtain the iron carbide composite titanium monoxide nano-particle photo-thermal catalyst, wherein the iron carbide composite titanium monoxide nano-particle photo-thermal catalyst has the characteristics of wide light absorption range, high methane yield, low resistivity, rapid carrier transfer capability, high photo-generated carrier separation capability, low carrier recombination rate, good carbon dioxide reduction high cycle stability and the like, and can be used for photo-thermally catalyzing carbon dioxide to reduce methane at the highest rate of 37.67 mu mol g^-1·h^-1. The preparation method has the advantages of simple operation, low cost, nontoxic raw materials and production according with the environmental protection concept.

Compared with the prior art, the invention has the following advantages:

(1) because the iron carbide composite titanium monoxide nano-particles are synthesized by adopting a one-step calcination method in the preparation process, compared with bulk phase materials, the ultra-large specific surface area can enable a large number of surface atoms to be used as active sites, so that the catalytic process is improved, the catalytic activity is improved, and a clear atomic structure model is favorably constructed.

(2) The titanium-based catalyst is combined with the traditional thermocatalytic material iron carbide, and the iron carbide composite titanium monoxide nano particles are obtained by an ammonia one-step calcination method, so that the full spectrum absorption and utilization are realized, the development of the photothermal catalyst is promoted, and the obvious practical application of more fully utilizing sunlight is realized.

(3) Compared with pure P25, the iron carbide and titanium monoxide compounded nanoparticle photocatalyst has the characteristics of wide light absorption range, high carbon dioxide reduction performance, low resistivity, capability of rapidly transferring self-current, high photogeneration carrier separation capability, low carrier recombination rate and good carbon dioxide reduction cycle stability.

(4) The invention takes carbon calcined by PAN as a basic framework, iron carbide and titanium monoxide nanoparticles are distributed on the base material, the morphological characteristics are uniformly and regularly distributed, a high specific surface area is provided for the material to better absorb sunlight, the preparation process is very simple, the method is suitable for industrial mass production, and the method has high economic and practical values.

(5) The iron carbide is applied to the photo-thermal catalysis direction for the first time to synthesize the iron carbide/carbon/titanium monoxide sandwich structure, the material is a noble metal-free photo-thermal catalysis material absorbing the full spectrum, the addition of the iron carbide effectively promotes the C-C coupling of methyl free radicals, the high-efficiency carbon dioxide reduction performance is shown, the better photo-thermal catalysis activity is shown in an ultraviolet-near infrared region, under the irradiation of visible light, the material is used for photo-catalytically reducing carbon dioxide to generate methane, and the methane generation rate can reach 37.67 mu mol g at most^-1·h^-1。

(6) The catalyst has light absorption range of full spectrum, carrier recombination difficulty and lambda>Under the irradiation of simulated sunlight with the wavelength of 420nm, the highest methane production rate can reach 37.67 mu mol.h^-1·g^-1. The preparation method of the catalyst has the advantages of low preparation cost, batch production and the like because the raw materials are easily obtained, the operation is simple, and the experimental conditions are easily achieved.

Drawings

FIG. 1 shows Fe obtained in example 1₂X-ray electron diffraction pattern of C/C/TiO nanoparticle photo-thermal catalyst;

FIG. 2 shows Fe obtained in example 1₂C/TiO nanoparticles, TiO/C uv-visible diffuse reflectance pattern prepared in comparative example 2;

FIG. 3 shows Fe obtained in example 1₂C/C/TiO nanoparticles, Fe obtained in comparative example 1₂A photocurrent performance diagram of the C/C nanoparticle photo-thermal catalyst when the bias voltage adopted by the photocurrent is 0V;

FIG. 4 shows Fe obtained in example 1₂C/C/TiO nanoparticles, Fe obtained in comparative example 1₂C/C, comparisonElectrochemical impedance of the TiO/C nanoparticle photothermal catalyst obtained in example 2;

FIG. 5 shows Fe obtained in example 1₂C/C/TiO nanoparticles, Fe obtained in comparative example 1₂C/C, the methane yield of the TiO/C nanoparticle photo-thermal catalyst obtained in the comparative example 2 and the time;

fig. 6 is an X-ray electron diffraction pattern of the catalyst prepared in comparative example 3.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

The electrochemical workstation used for testing the electrochemical performance of the iron carbide composite titanium monoxide photothermal catalysis carbon dioxide reduction material with effective photon-generated carrier separation and transfer performance in the embodiment of the invention is an Aiwei electrochemical workstation with the model IviumStat.h. UV-visible diffuse reflectance passes the UV-2800 test; fluorescence spectra were measured by FLS 980; the carbon dioxide reduction performance test adopts Shimadzu GC2014 gas chromatography.

The electrochemical performance test method in each embodiment of the invention is as follows:

mixing 7.5mg of nanoparticle photocatalyst, 1mg of ethyl cellulose, 1mL of alpha-terpineol and 0.5mL of ethanol, and then carrying out ultrasonic treatment for 12h with the power of 60W and the frequency of 40KHz to obtain slurry;

coating the obtained slurry on FTO glass, controlling the coating thickness to be 0.5-1mm, drying in an oven at 60 ℃ to obtain an electrochemical testing working electrode, and then testing at an electrochemical workstation to carry out electrochemical performance.

In the following examples, unless otherwise specified, the starting materials or the treatment techniques are all conventional and commercially available materials or conventional treatment techniques in the art.