阅读说明：本技术 电催化氧还原制过氧化氢氮掺杂碳催化剂及其制备方法 (Nitrogen-doped carbon catalyst for preparing hydrogen peroxide by electrocatalytic oxygen reduction and preparation method thereof ) 是由 乔明华 王丹 于 2020-11-26 设计创作，主要内容包括：本发明属于能源化工技术领域,具体为一种电催化氧还原制过氧化氢氮掺杂碳催化剂及其制备方法。本发明的催化剂以糖为碳源,以二氰二胺为氮源,通过一步热裂解法制备的氮掺杂碳材料。本发明具有制备方法便捷、原料易得和氮碳含量易于调节等优点。该催化剂用于电化学氧还原制备过氧化氢的反应时,以葡萄糖为碳源的催化剂与以其他糖为碳源的催化剂相比表现出更高的选择性和活性,选择性最高可达90%,实现在常温、常压液相体系中电催化氧还原合成过氧化氢,具有良好的环保意义和工业应用前景。(The invention belongs to the technical field of energy chemical industry, and particularly relates to a nitrogen-doped carbon catalyst for preparing hydrogen peroxide by electrocatalytic oxygen reduction and a preparation method thereof. The catalyst is a nitrogen-doped carbon material prepared by one-step thermal cracking method by taking sugar as a carbon source and dicyanodiamine as a nitrogen source. The invention has the advantages of convenient preparation method, easily obtained raw materials, easily adjusted nitrogen and carbon content and the like. When the catalyst is used for preparing hydrogen peroxide by electrochemical oxygen reduction, the catalyst taking glucose as a carbon source has higher selectivity and activity compared with catalysts taking other sugars as carbon sources, the selectivity can reach 90 percent at most, the hydrogen peroxide is synthesized by electrocatalytic oxygen reduction in a normal-temperature and normal-pressure liquid-phase system, and the catalyst has good environmental protection significance and industrial application prospect.)

1. A catalyst for preparing hydrogen peroxide by electrochemical catalytic oxygen reduction is characterized in that a nitrogen-doped carbon material is prepared by one-step thermal cracking by taking sugar as a carbon source and dicyanodiamine as a nitrogen source; wherein the nitrogen doping amount is controlled and adjusted by adjusting the ratio of glucose and dicyanodiamine.

2. The catalyst for preparing hydrogen peroxide by electrochemical catalytic oxygen reduction according to claim 1, wherein the sugar is derived from monosaccharide, disaccharide and polysaccharide, and is selected from glucose, fructose, ribose, xylose, arabinose, galactose, mannose, maltose, sucrose, cellulose and starch.

3. The catalyst for preparing hydrogen peroxide by electrochemical catalytic oxygen reduction according to claim 2, wherein the mass ratio of the sugar to dicyanodiamine is 0.01 to 0.5.

4. The preparation method of the catalyst for preparing hydrogen peroxide by electrochemical catalytic oxygen reduction according to claim 1, which comprises the following steps:

(1) dispersing 0.1-5 g of sugar and 1-10 g of dicyanodiamide in 50-200 mL of deionized water, uniformly dispersing by ultrasonic, and evaporating in a water bath at 50-90 ℃;

(2) then, drying the mixture in an oven at the temperature of 80-120 ℃ overnight;

(3) and finally, placing the mixture in a tube furnace to be roasted for 2.0 to 5.0 hours at the temperature of 900 ℃ in nitrogen, taking out the mixture after cooling to the room temperature, and grinding the mixture into powder to obtain the nitrogen-doped carbon catalyst.

Dispersing 0.1-5 g of sugar and 1-10 g of dicyanodiamine in 50-200 mL of deionized water, drying by distillation in a water bath at 50-90 ℃ after uniform ultrasonic dispersion, then drying overnight in an oven at 80-120 ℃, finally roasting in a tube furnace at 900 ℃ in nitrogen for 2.0-5.0 h, cooling to room temperature, taking out, and grinding into powder to obtain the nitrogen-doped carbon catalyst.

5. The method according to claim 4, wherein the sugar is selected from the group consisting of monosaccharides, disaccharides and polysaccharides, and is selected from the group consisting of glucose, fructose, ribose, xylose, arabinose, galactose, mannose, maltose, sucrose, cellulose and starch.

6. The method according to claim 5, wherein the mass ratio of the sugar to the dicyanodiamide is 0.01 to 0.5.

Technical Field

The invention belongs to the technical field of chemical industry, and particularly relates to a nitrogen-doped carbon catalyst for preparing hydrogen peroxide by electrocatalytic oxygen reduction and a preparation method thereof.

Background

Hydrogen peroxide (H)₂O₂) Is thatAn important bulk chemical, which is a green and clean environment-friendly oxidant, is widely applied to the industries of medical sterilization, wastewater treatment, papermaking and textile, aerospace, metallurgy, electronic industry and the like. At present, hydrogen peroxide still has many beneficial effects which are continuously discovered: unlike other anti-infective drugs or antiseptics, the mechanism of action of hydrogen peroxide can significantly reduce the risk of resistance of bacteria over time, which will provide more possibilities for the widespread use of hydrogen peroxide as an antimicrobial chemical on a global scale. The traditional anthraquinone autoxidation method for producing hydrogen peroxide has the defects of high energy consumption, environmental pollution caused by reaction byproducts, high production cost and the like. Compared with the multi-step and high-consumption production process, the method adopts a one-step method to directly synthesize the hydrogen and the oxygen into H₂O₂Has the advantages of simple process, environment-friendly property, economic raw materials and the like. The research shows that the palladium-based catalyst has good hydrogen and oxygen to directly synthesize H₂O₂And (4) performance. However, the direct synthesis of H from hydrogen and oxygen₂O₂There is a potential risk of explosion. Therefore, the development of a novel safe, environmentally friendly H₂O₂The synthetic route has important practical significance.

The electrochemical method for synthesizing hydrogen peroxide by oxygen reduction has the advantages of high efficiency, safe operation, higher current density and the like, and the synthesized hydrogen peroxide solution has no impurities and high purity, so the method has good development prospect. The advantages of hydrogen peroxide prepared by the oxygen cathode reduction method are mainly reflected in convenience and economy, the product hydrogen peroxide can be directly used for sewage treatment and other applications, the hydrogen peroxide does not need to be transferred and transported, the use cost of the hydrogen peroxide is greatly saved, and the hydrogen peroxide has strong economic applicability.

The catalysts currently used for the electrocatalytic synthesis of hydrogen peroxide mainly comprise noble metals and alloys thereof, monatomic catalysts and carbon-based materials. Amal et al (Zheng, Z., Ng, Y. H., Wang, D.W., Amal, R. Epitaxial Growth of Au-Pt-Ni nanorodes for Direct high selection H.)₂O₂ Production[J]. Advanced Materials,2016, 28,9949.) demonstrated that both Au-Ni and Au-Ni-Pt core-shell nanorods can exhibit relatively high activity and H₂O₂And (4) selectivity. At the overpotential of 150 mV, the Au-Pt-Ni nanorod couples H₂O₂The selectivity and activity of the compound can reach 95 percent and 1.01 mAcm^-2. Lee et al (Yang, S., Kim, J., Tak, Y. J., Soon, A., Lee, H. Single-Atom Catalyst of Platinum Supported on Titanium Nitride for selective Electrochemical Reactions [ J., U.S.)]. AngewandteChemieInternation Edition2015,55, 2058.) a Pt monatomic catalyst supported on titanium nitride nanoparticles (Pt/TiN) was prepared. DFT calculations indicate that N-vacancies on TiN supports are essential for stabilizing a single Pt atom. Results of the Rotating Ring Disk Electrode (RRDE) study showed that the monatomic Pt catalyst with a Pt loading of 0.35wt% (0.35 wt% Pt/TiN) exhibited the highest H₂O₂The selectivity and the mass ratio activity of the catalyst are nearly one order of magnitude higher than that of Pt nanoparticles, and the selectivity and the mass ratio activity of the catalyst reach 78Ag_Pt ^-1. Cui et al (Lu, z., Chen, g., Siahrostami, s., Chen, z., Liu, k., Xie, J., Liao, l., Wu, t., Lin, d., Liu, y., jaramilo, t. f., nw rskov, J. k., Cui, y. High-efficiency oxygen reduction to hydrogenated peroxide catalyst captured by oxidized carbon substrates [ J. k., Cui, y., High-efficiency oxygen reduction to oxidized carbon substrates].Nature Catalysis2018, 1, 156.) improvement of electrocatalytic synthesis H of carbon materials by surface oxidation treatment₂O₂And (4) performance. Compared with the conventional carbon nanotubes, the overpotential (about 130mV, 0.2 mA) of the oxidized carbon nanotubes (O-CNTs) in the alkaline and neutral media is remarkably reduced, and the selectivity is improved to about 90%. Characterization indicated that the presence of C-O and C = O functional groups contributed to H₂O₂Production plays a key role. The authors also found that the activity and selectivity of the catalyst was directly related to the oxygen content, further indicating the importance of the oxygen-containing functional groups.

From O₂Preparation of H by cathodic reduction₂O₂No explosion risk and no pollution, can convert electric energy from renewable energy sources (water, wind and sunlight) into chemical energy, and is a new generation of green, environment-friendly, safe and reliable H₂O₂And (3) a synthesis technology. For this reaction, a noble metal catalyst and a carbon-based catalystHas the advantages of high selectivity, low overpotential, good electrocatalytic performance and the like. However, the following major problems still exist in the current catalysts for this reaction: the atom utilization efficiency of the noble metal nano catalyst is not high; monatomic catalysts have much higher surface energies than their corresponding nanoparticles and clusters, which can lead to severe agglomeration during the catalytic reaction; the interaction between the active ingredients and the carrier and the mechanism of action on the reaction remain to be elucidated.

Therefore, the development of a novel catalyst for preparing hydrogen peroxide by electrocatalytic oxidation reduction of the nitrogen-doped carbon material, which is prepared by using the sugar as the carbon source and the dicyanodiamine as the nitrogen source through one-step thermal cracking, has important practical value. Research results show that the selectivity and activity of the material prepared by taking glucose as a carbon source are obviously higher than those of the catalyst prepared by taking other sugars as the carbon source.

Disclosure of Invention

The invention aims to provide a catalyst with good catalytic performance and capable of being used for synthesizing hydrogen peroxide by electrochemical catalytic oxygen reduction, and a preparation method of the catalyst.

The catalyst for synthesizing hydrogen peroxide by electrocatalytic oxidation reduction is a non-noble metal catalyst, and is a nitrogen-doped carbon material prepared by one-step thermal cracking method by using various sugars as carbon sources and dicyanodiamine as nitrogen sources, wherein the nitrogen doping amount can be controlled and adjusted by adjusting the ratio of glucose to dicyanodiamine.

In the invention, the sugar is derived from monosaccharide, disaccharide and polysaccharide, and comprises glucose, fructose, ribose, xylose, arabinose, galactose, mannose, maltose, sucrose, cellulose and starch.

In the invention, the mass ratio of the sugar to the dicyanodiamine is 0.01-0.5.

The invention provides a preparation method of a catalyst for preparing hydrogen peroxide by electrochemical oxygen reduction, which comprises the following specific steps:

(1) dispersing 0.1-5 g of sugar and 1-10 g of dicyanodiamide in 50-200 mL of deionized water, uniformly dispersing by ultrasonic, and evaporating in a water bath at 50-90 ℃;

(2) then, drying the mixture in an oven at the temperature of 80-120 ℃ overnight;

(3) and finally, placing the mixture in a tube furnace to be roasted for 2.0 to 5.0 hours at the temperature of 900 ℃ in nitrogen, taking out the mixture after cooling to the room temperature, and grinding the mixture into powder to obtain the nitrogen-doped carbon catalyst.

In the invention, the sugar is derived from monosaccharide, disaccharide and polysaccharide, and comprises glucose, fructose, ribose, xylose, arabinose, galactose, mannose, maltose, sucrose, cellulose and starch.

In the invention, the mass ratio of the sugar to the dicyanodiamine is 0.01-0.5.

The catalyst prepared based on the catalyst design strategy provided by the invention can reduce two electrons of oxygen into hydrogen peroxide with 90% selectivity, the selectivity is basically kept unchanged within the voltage range of 0-0.6V, and the catalytic performance is obviously improved.

Compared with the prior art, the beneficial effects of the invention are mainly embodied in the following three aspects:

(1) compared with anthraquinone process and direct hydrogen-oxygen synthesis process, the preparation process of hydrogen peroxide has the obvious advantages of environment friendship, less explosion, normal temperature and pressure operation, etc. Meanwhile, the low-concentration hydrogen peroxide synthesized by the process can be directly applied to the fields of medical sterilization, sewage treatment and the like, so that the in-situ distributed green production and green application of the hydrogen peroxide are realized, and the transportation safety risk is reduced;

(2) the nitrogen-doped carbon material provided by the invention is a non-noble metal catalyst, is prepared by one-step pyrolysis of various sugars and dicyanodiamine, and has the advantages of wide raw material source and low catalyst cost;

(3) the reaction proposed by the invention is carried out at normal temperature and normal pressure. The reaction system is a heterogeneous liquid phase catalysis system consisting of perchloric acid solution, and the synthesized hydrogen peroxide can stably exist and has good reaction stability.

The catalyst provided by the invention can be evaluated by the following method:

the catalytic performance of the catalyst was investigated using the rotating ring disk electrode of PINE and an electrochemical workstation. Dispersing the catalyst in a mixed solution of water, isopropanol and nafion, ultrasonically dispersing uniformly, dripping a certain amount of uniform solution on a rotating ring disk electrode, and placing in the air for airing. Then 0.1M perchloric acid solution is poured into an H-shaped electrolytic cell, nitrogen is firstly introduced to remove oxygen dissolved in the solution, CV and LSV scanning is carried out by an electrochemical workstation, and then oxygen is continuously introduced into the solution until the solution is saturated to carry out CV and LSV scanning. The electrode speed in the reaction was 1600 rpm, and the loop current was 1.2V.

Drawings

FIG. 1 is an SEM photograph of a catalyst of the present invention.

FIG. 2 shows the results of activity (a) and selectivity (b) of the reaction test examples for preparing hydrogen peroxide by electrocatalytic oxygen reduction with different catalysts.

FIG. 3 shows the results of activity (a) and selectivity (b) of comparative test examples of electrocatalytic oxygen reduction reactions for hydrogen peroxide with different catalysts.

Detailed Description

The invention is further illustrated by the following examples, but is not limited thereby.

Example 1:

(1) dispersing 1.25 g of sugar and 5g of dicyanodiamine in 200 mL of deionized water, performing ultrasonic dispersion uniformly, evaporating to dryness in a water bath at 80 ℃, then placing in an oven at 80 ℃ for drying overnight, finally placing in a tube furnace, roasting at 800 ℃ in nitrogen for 2.0 h, cooling to room temperature, taking out, grinding into powder to obtain a catalyst, and marking as Glc-DICY;

(2) dispersing the catalyst in a mixed solution of water, isopropanol and nafion, ultrasonically dispersing uniformly, dripping a certain amount of uniform solution on a rotating ring disk electrode, and placing in the air for airing. Then 0.1M perchloric acid solution is poured into an H-shaped electrolytic cell, nitrogen is firstly introduced to remove oxygen dissolved in the solution, CV and LSV scanning is carried out by an electrochemical workstation, and then oxygen is continuously introduced into the solution until the solution is saturated to carry out CV and LSV scanning. The electrode speed in the reaction was 1600 rpm, and the loop current was 1.2V.

The reaction results of this example are shown in FIG. 2. As can be seen from the figure, the ratio of glucose to dicyanodiamine can significantly affect the activity and selectivity of oxygen two-electron reduction, and the optimal ratio of glucose to dicyanodiamine can prepare the catalyst with the selectivity of 90% and the activity can reach the highest.

Example 2:

the glucose in example 1 was replaced with fructose, and the other preparation conditions were the same as in example 1. The catalyst obtained is designated Fru-DICY.

Example 3:

the glucose in example 1 was replaced with galactose, and the other preparation conditions were the same as in example 1. The resulting catalyst is designated Gal-DICY.

Example 4:

the glucose in example 1 was replaced with arabinose, and the other preparation conditions were the same as in example 1. The resulting catalyst is designated Ara-DICY.

Example 5:

the glucose in example 1 was replaced with ribose, and the preparation conditions were the same as in example 1. The resulting catalyst is designated Rib-DICY.

Example 6:

the glucose in example 1 was replaced with xylose, and the other preparation conditions were the same as in example 1. The resulting catalyst is designated Xyl-DICY.

Example 7:

the glucose in example 1 was replaced with mannose, and the other preparation conditions were the same as in example 1. The resulting catalyst is designated Man-DICY.

Through the analysis of the results of the above examples, the effect of 1.25 g of seven monosaccharides mixed with 5g of dicyanodiamine on the activity and selectivity of the oxygen reduction reaction is obtained. When glucose is used as a carbon source, the activity is highest, the ring current can reach 0.17 mA, and the selectivity is kept at about 90% in the range of 0-0.5V.

Comparative example 1:

(1) dispersing 0.5g of sugar and 5g of dicyanodiamide in 200 mL of deionized water, performing ultrasonic dispersion uniformly, evaporating to dryness in a water bath at 80 ℃, then placing in an oven at 80 ℃ for drying overnight, finally placing in a tube furnace, roasting at 800 ℃ in nitrogen for 2.0 h, cooling to room temperature, taking out, and grinding into powder to obtain a catalyst, namely 0.5 Glc-DICY;

(2) dispersing the catalyst in a mixed solution of water, isopropanol and nafion, ultrasonically dispersing uniformly, dripping a certain amount of uniform solution on a rotating ring disk electrode, and placing in the air for airing. Then 0.1M perchloric acid solution is poured into an H-shaped electrolytic cell, nitrogen is firstly introduced to remove oxygen dissolved in the solution, CV and LSV scanning is carried out by an electrochemical workstation, and then oxygen is continuously introduced into the solution until the solution is saturated to carry out CV and LSV scanning. The electrode speed in the reaction was 1600 rpm, and the loop current was 1.2V.

The results of this comparative example are shown in FIG. 3, and show that the selectivity of hydrogen peroxide generation is low when 0.5g of glucose is mixed with 5g of dicyanodiamide, and the selectivity is the highest when 1.25 g or 1.5 g of glucose is mixed with 5g of dicyanodiamide, and reaches 90% between 0 and 0.5V. The magnitude of the combined current gave a mixing ratio of 1.25 g of sugar to 5g of dicyanodiamine which was the optimum mixing ratio.