阅读说明：本技术 一种自支撑杂原子掺杂污泥炭电极材料的制备方法 (Preparation method of self-supporting heteroatom-doped sludge carbon electrode material ) 是由 赵迎新 麻泽浩 杨凯超 杨知凡 季民 于 2020-05-21 设计创作，主要内容包括：本发明提供了一种自支撑杂原子掺杂污泥炭电极材料的制备方法,相比于现有技术,本发明制备的自支撑杂原子掺杂污泥炭电极材料可同时满足作为产氢催化剂和工作电极的要求,将两者“合二为一”,不仅有效避免了传统粉末催化剂存在的问题,同时因独特的多孔自支撑结构有效增加了析氢反应的活性位点,解决了目前电化学析氢技术的高耗低效问题。此外,本发明提供的制备方法简单快捷,无需负载步骤,也无需添加掺杂剂、改良剂和造孔剂等多种化学添加剂,降低了制备成本,体现了废弃物再利用以及产生高附加值的作用,同时也为电解水析氢技术提供了一种新的电极材料。(Compared with the prior art, the self-supporting heteroatom-doped sludge carbon electrode material prepared by the invention can simultaneously meet the requirements of serving as a hydrogen production catalyst and a working electrode, combines the hydrogen production catalyst and the working electrode into a whole, effectively avoids the problems of the traditional powder catalyst, effectively increases the active sites of hydrogen evolution reaction due to a unique porous self-supporting structure, and solves the problems of high consumption and low efficiency of the existing electrochemical hydrogen evolution technology. In addition, the preparation method provided by the invention is simple and rapid, does not need a loading step, does not need to add various chemical additives such as a doping agent, a modifying agent, a pore-forming agent and the like, reduces the preparation cost, embodies the effects of recycling wastes and generating high added value, and simultaneously provides a new electrode material for the electrolytic water hydrogen evolution technology.)

1. A preparation method of a self-supporting heteroatom-doped sludge carbon electrode material is characterized by comprising the following steps:

1) putting the sludge dry powder in an atmosphere furnace, introducing inert gas, heating and pre-carbonizing to obtain first sludge carbon powder, washing and drying the first sludge carbon powder to obtain second sludge carbon powder;

2) placing phenolic resin into a container, adding deionized water for first ultrasonic dispersion, and then adding the second sludge carbon powder for second ultrasonic dispersion to obtain uniform mixed liquor; transferring the mixed solution into an evaporator, and heating and drying the mixed solution in a vacuum state to obtain a sludge-like mixture of the sludge autodoped phenolic resin;

3) pressing and forming the sludge-shaped mixture of the sludge autodoped phenolic resin, and solidifying to obtain a sheet-shaped mixture of the sludge autodoped phenolic resin; then placing the sheet-shaped mixture of the sludge self-doping phenolic resin in an atmosphere furnace, introducing inert gas, keeping the temperature rise and carbonization under anaerobic condition until the sheet-shaped mixture of the sludge self-doping phenolic resin has a porous self-supporting structure; and after carbonization, washing to be neutral, and drying to obtain the self-supporting heteroatom-doped sludge carbon electrode material.

2. The preparation method of the self-supporting heteroatom-doped sludge carbon electrode material as claimed in claim 1, wherein the preparation process of the sludge dry powder is as follows: drying sludge to obtain blocky dry sludge, crushing the blocky dry sludge, screening by using a screen to obtain sludge fine powder, carrying out magnetic stirring and cleaning on the sludge fine powder, and drying to obtain the sludge dry powder.

3. The preparation method of the self-supporting heteroatom-doped sludge carbon electrode material as claimed in claim 2, wherein the drying temperature of the sludge is 80-105 ℃; the mesh opening of the mesh screen is 60-80 meshes; the magnetic stirring time of the sludge fine powder is 0.5-1 h, and the drying temperature of the sludge fine powder is 60-80 ℃.

4. The preparation method of the self-supporting heteroatom-doped sludge carbon electrode material as claimed in claim 1, wherein in the step 1), sludge dry powder is placed in an atmosphere furnace, inert gas is introduced, and heating and pre-carbonization are performed to obtain first sludge carbon powder; and washing the first sludge carbon powder by using deionized water and absolute ethyl alcohol under the condition of magnetic stirring, and drying to obtain second sludge carbon powder.

5. The preparation method of the self-supporting heteroatom-doped sludge carbon electrode material as claimed in claim 4, wherein in the step 1), the pre-carbonization temperature is 400-500 ℃, the pre-carbonization time is 1-2 h, and the flow rate of the inert gas is 200-300 mL/min; the magnetic stirring time of the first sludge carbon powder is 1-2 h; the drying temperature of the first sludge carbon powder is 60-80 ℃.

6. The preparation method of the self-supporting heteroatom-doped sludge carbon electrode material as claimed in claim 1, wherein in the step 2), the weight ratio of the phenolic resin to the second sludge carbon powder is 1: 2-1: 4.

7. The preparation method of the self-supporting heteroatom-doped sludge carbon electrode material as claimed in claim 1, wherein in the step 2), the time of the first ultrasonic dispersion and the time of the second ultrasonic dispersion are both 1-2 h; the drying temperature of the mixed liquid is 60-80 ℃, and the drying time of the mixed liquid is 6-8 h.

8. The preparation method of the self-supporting heteroatom-doped sludge carbon electrode material as claimed in claim 1, wherein in the step 3), the pressing forming pressure of the sludge-like mixture of the sludge self-doped phenolic resin is 20-30 Mpa; the curing is constant temperature curing at the temperature of 180-220 ℃; the curing time is 5-6 h.

9. The preparation method of the self-supporting heteroatom-doped sludge carbon electrode material as claimed in claim 1, wherein in the step 3), the flow rate of the inert gas is 200-400 mL/min; the temperature rise rate of the carbonization is 5-10 ℃/min, and the temperature of the carbonization is 800-1000 ℃; the carbonization time is 2-2.5 h.

10. The preparation method of the self-supporting heteroatom-doped sludge carbon electrode material as claimed in claim 1, wherein in the step 3), after carbonization is completed, acid washing is performed firstly, then water washing is performed to neutrality, and drying is performed to obtain the self-supporting heteroatom-doped sludge carbon electrode material; wherein the acid concentration of the acid washing is 0.1-0.2M, and the drying temperature is 60-80 ℃.

Technical Field

The invention relates to the technical field of electrocatalysis, in particular to a preparation method of a self-supporting heteroatom-doped sludge carbon electrode material.

Background

Hydrogen energy is recognized as a clean, high calorific value and environmentally friendly energy source. Hydrogen energy can also be used as a medium for storing, transporting, and converting other clean energy sources (solar, wind, biological, etc.). The electrolytic water is an important hydrogen preparation method, most of catalysts for the electrolytic water Hydrogen Evolution Reaction (HER) are precious metal-based (such as Pt) materials, the reserves are rare, the cost is high, and in contrast, the development of low-cost and high-activity non-precious metal catalysts is an important challenge in the field of hydrogen production.

Carbon materials have gradually entered the human vision due to low cost, abundant resources, and good stability. Conventional hydrogen evolution catalytic materials require doping by complex chemical methods to improve the hydrogen evolution performance of the catalyst. However, in the synthesis process of the carbon-doped catalytic material, a chemical agent is required to be added as a dopant, and sometimes a carbon-doped precursor, a pore-forming agent, a template agent and the like are also required to improve the content of doped atoms in the carbon material, the catalytic activity of the catalytic material and active sites of the reaction. The cost of preparing the catalytic material is increased due to the complicated reaction involved, and byproducts are easily generated.

At present, most of the forms of the catalysts for hydrogen evolution from electrolyzed water are powder. When preparing a working electrode, a polymer binder and a conductive additive are needed to load a catalyst on the electrode, but the following problems exist:

(1) the morphology and structure of the catalyst cannot be effectively controlled, so that the dead volume on the catalyst is large, the electrochemical active sites are reduced, an interference interface which is not beneficial to reaction is formed on the surface of the electrode, and the electronic conduction between the electrode and electrolyte in the electrochemical process and the mass transfer of reactants/products in the multiphase reaction process are limited.

(2) Because the gas separated out on the surface of the electrode in the electrocatalytic hydrogen evolution reaction continuously escapes, the catalyst coated on the electrode is easy to separate, and the activity and the service life of the catalyst are damaged.

In view of the above, it is necessary to provide a technical solution to the above problems.

Disclosure of Invention

The invention aims to: the preparation method of the self-supporting heteroatom-doped sludge carbon electrode material is provided, and the problems of high consumption and low efficiency of the traditional electrochemical hydrogen evolution technology are solved; the electrode material is low in manufacturing cost, chemical agents do not need to be added in the preparation process to serve as doping agents, modifying agents, pore-forming agents and the like, and the effect of recycling wastes to generate high added value is fully reflected.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a self-supporting heteroatom-doped sludge carbon electrode material comprises the following steps:

1) putting the sludge dry powder in an atmosphere furnace, introducing inert gas, heating and pre-carbonizing to obtain first sludge carbon powder, washing and drying the first sludge carbon powder to obtain second sludge carbon powder;

2) placing phenolic resin into a container, adding deionized water for first ultrasonic dispersion, and then adding the second sludge carbon powder for second ultrasonic dispersion to obtain uniform mixed liquor; transferring the mixed solution into an evaporator, and heating and drying the mixed solution in a vacuum state to obtain a sludge-like mixture of the sludge autodoped phenolic resin;

3) pressing and forming the sludge-shaped mixture of the sludge autodoped phenolic resin, and solidifying to obtain a sheet-shaped mixture of the sludge autodoped phenolic resin; then placing the sheet-shaped mixture of the sludge self-doping phenolic resin in an atmosphere furnace, introducing inert gas, keeping the temperature rise and carbonization under anaerobic condition until the sheet-shaped mixture of the sludge self-doping phenolic resin has a porous self-supporting structure; and after carbonization, washing to be neutral, and drying to obtain the self-supporting heteroatom-doped sludge carbon electrode material.

The self-supporting heteroatom-doped sludge carbon electrode material prepared by the invention has an independent supporting structure, can be directly applied to a working electrode of electrochemical reaction, does not need to coat a catalyst on the electrode, does not need to coat an organic adhesive and a conductive additive, and fully utilizes the characteristic of heteroatom doping contained in sludge to improve the electro-catalytic hydrogen evolution performance. The preparation method ensures the integrity and mechanical strength of the self-supporting electrode catalyst, and is beneficial to the electron transfer and gas conduction between the electrode and the electrolyte; the preparation process is simple, the raw materials are easy to obtain, and the electrode has good activity and stability and wide application value. In addition, compared with the powder catalyst, the self-supporting sludge carbon electrode material has rich porous structures, so that on one hand, the self-supporting sludge carbon electrode material is beneficial to the permeation of electrolyte, the diffusion of ions and reaction products and the improvement of the electro-catalytic reaction kinetics in the electrochemical process; on the other hand, the active surface area is increased, and the electrochemical active sites are increased.

The phenolic resin adopted by the invention is the earliest artificially synthesized resin, has the advantages of mature production process, low price, high carbonization yield, single component, low impurity content, easiness in activation and pore formation and the like, and has wide application prospect when being used as an electrode material. The sludge has the characteristic of heteroatom autodoping, and the heteroatoms can not only improve the catalytic performance of the carbon material, but also enhance the stability of the carbon material. The sludge and the phenolic resin are dispersed and mixed uniformly by ultrasound, and are carbonized at high temperature under anaerobic conditions, so that the obtained novel electrode material with the self-supporting structure fully exerts the characteristic of sludge heteroatom autodoping, realizes resource treatment of the sludge on the one hand, and provides a new practical application mode for a sludge resource utilization technology by combining the application of the field of electrocatalysis hydrogen production on the other hand, and has good innovation and research value.

Preferably, the preparation process of the sludge dry powder comprises the following steps: drying sludge to obtain blocky dry sludge, crushing the blocky dry sludge, screening by using a screen to obtain sludge fine powder, carrying out magnetic stirring and cleaning on the sludge fine powder, and drying to obtain the sludge dry powder. The sludge in the digestion tank is subjected to anaerobic biological treatment, most of impurities are removed, organic matters in the sludge are degraded into organic matters mainly comprising methane by bacteria under an anaerobic condition, so that the organic matters are decomposed more quickly and easily in the subsequent pre-carbonization and carbonization processes, and uniform and continuous formation of holes is facilitated.

Preferably, the drying temperature of the sludge is 80-105 ℃; the mesh opening of the mesh screen is 60-80 meshes; the magnetic stirring time of the sludge fine powder is 0.5-1 h, and the drying temperature of the sludge fine powder is 60-80 ℃.

Preferably, in the step 1), the sludge dry powder is placed in an atmosphere furnace, inert gas is introduced, and heating and pre-carbonization are carried out to obtain first sludge carbon powder; and washing the first sludge carbon powder by using deionized water and absolute ethyl alcohol under the condition of magnetic stirring, and drying to obtain second sludge carbon powder. The contact area of the small-particle sludge carbon powder is large, the mixing reaction with the phenolic resin is more uniform, and the mixture formed by the small-particle sludge carbon powder and the phenolic resin is more uniform and consistent in the subsequent processes of press forming, self-supporting structure building and the like due to smaller particles on the whole; in addition, the small particulate matters have small interaction force with each other, and gas generated by the decomposition of the organic matters is more easily discharged.

Preferably, in the step 1), the pre-carbonization temperature is 400-500 ℃, the pre-carbonization time is 1-2 hours, and the flow rate of the inert gas is 200-300 mL/min; the magnetic stirring time of the first sludge carbon powder is 1-2 h; the drying temperature of the first sludge carbon powder is 60-80 ℃. The method is characterized in that the pre-carbonization is carried out at the temperature of 400-500 ℃, a part of substances in the sludge are decomposed and gas is generated to be discharged, holes are formed in advance, a foundation is provided for subsequent carbonization at high temperature by uniformly mixing with phenolic resin, the mixing is more uniform, a certain supporting structure is formed, the formation of a subsequent self-supporting structure is facilitated, and the self-supporting heteroatom-doped sludge carbon electrode material is obtained.

Preferably, in the step 2), the weight ratio of the phenolic resin to the second sludge carbon powder is 1: 2-1: 4. The deionized water can be mixed with the phenolic resin in the ratio of (80-100) to (1-2). The phenolic resin and the second sludge carbon powder can be uniformly mixed by mixing according to the proportion. The higher the proportion of the second sludge carbon powder is, the higher the heteroatom of the sludge is, the more holes are formed in and on the surface of the obtained sludge carbon electrode material, the more active sites of the corresponding electrocatalytic hydrogen evolution reaction are, and the higher the stability of the electrode material is. However, if the proportion of the second sludge carbon powder is too high and the proportion of the phenolic resin is insufficient, the carbonization rate is low, which adversely affects the formation of pores in the second sludge carbon powder and the hydrogen evolution effect of the electrode material. Thus, the weight ratio of the phenolic resin to the second sludge carbon powder is preferably kept to be 1: 2-1: 4, specifically, the weight of the phenolic resin is 5-10 g, the weight of the deionized water is 400-500 mL, and the weight of the second sludge carbon powder is 15-20 g.

Preferably, in the step 2), the time of the first ultrasonic dispersion and the time of the second ultrasonic dispersion are both 1-2 hours; the drying temperature of the mixed liquid is 60-80 ℃, and the drying time of the mixed liquid is 6-8 h. The specific ultrasonic time can be changed along with the different carbonization contents of the added phenolic resin and the second sludge, so that the phenolic resin and the second sludge can be ensured to be finally uniformly mixed.

Preferably, in the step 3), the pressing degree of the mud-like mixture of the sludge self-doping phenolic resin is 20-30 Mpa; the curing is constant temperature curing at the temperature of 180-220 ℃; the curing time is 5-6 h. The mixture is cured under a constant temperature state, so that each surface of the mixture can be uniformly cured, the property of the mixture cannot be influenced due to different temperatures in the mixture and the surface of the mixture, the preheating effect can be achieved when the mixture is cured at 180-220 ℃, a solid foundation is laid for subsequent high-temperature carbonization, and preferably, the constant-temperature curing temperature is 200 ℃.

Preferably, in the step 3), the flow rate of the inert gas is 200-400 mL/min; the temperature rise rate of the carbonization is 5-10 ℃/min, and the temperature of the carbonization is 800-1000 ℃; the carbonization time is 2-2.5 h. The uniform heating rate is helpful for fully exciting the early reaction of the organic components in the sludge, and provides a foundation for the subsequent rapid decomposition of the organic components under the high-temperature anaerobic carbonization condition, and decomposed gas can be continuously discharged, so that abundant holes are formed inside and on the surface of the sludge carbon electrode, and a porous self-supporting structure can be uniformly formed under the condition.

Preferably, in the step 3), after carbonization, acid washing is performed firstly, then water washing is performed to be neutral, and the self-supporting heteroatom-doped sludge carbon electrode material is obtained after drying; wherein the acid concentration of the acid washing is 0.1-0.2M, and the drying temperature is 60-80 ℃. The acid used for acid washing may be HNO₃、HCl、H₂SO₄At least one of (1).

The invention has the beneficial effects that:

1) compared with the prior art, the self-supporting heteroatom-doped sludge carbon electrode material prepared by the invention can simultaneously meet the requirements of serving as a hydrogen production catalyst and a working electrode, combines the hydrogen production catalyst and the working electrode into a whole, not only effectively avoids the problems of the traditional powder catalyst, but also effectively increases the active sites of hydrogen evolution reaction due to the unique porous self-supporting structure, and solves the problems of high consumption and low efficiency of the existing electrochemical hydrogen evolution technology. In addition, the preparation method provided by the invention is simple and rapid, does not need a loading step, does not need to add various chemical additives such as a doping agent, a modifying agent, a pore-forming agent and the like, reduces the preparation cost, embodies the effects of recycling wastes and generating high added value, and simultaneously provides a new electrode material for the electrolytic water hydrogen evolution technology.

2) The preparation method comprises the steps of ultrasonically dispersing and uniformly mixing the sludge and the phenolic resin, then performing press forming on the mixture, performing anaerobic high-temperature carbonization on the mixture, and finally converting the mixture into the electrode material.

3) Under the condition of high-temperature anaerobic carbonization, the organic components of the sludge are quickly decomposed and generate gas to be discharged, and because the gas is continuously discharged, rich holes are formed in the interior and the surface of the sludge carbon electrode material, so that the active surface area of the sludge carbon electrode material is increased, and further, active sites of the sludge carbon electrode material for electrocatalytic hydrogen evolution reaction are increased, hydrogen production reaction and hydrogen gas precipitation are facilitated, the blockage and inactivation of the sludge carbon electrode material are prevented, and the stability of the sludge carbon electrode material is improved.

4) The sludge contains heteroatom catalytic components such as Fe, S, P and the like, has the advantage of heteroatom self-doping, and the doped heteroatom is beneficial to the catalytic hydrogen evolution reaction, so that the electrocatalytic hydrogen evolution effect of the sludge carbon electrode material is further improved, and if the sludge carbon electrode material is taken as a catalyst, the activity and the service life of the catalyst are prolonged.

Drawings

FIG. 1 is a flow chart of the preparation method of the present invention.

FIG. 2 is a scanning electron micrograph of an electrode material according to example 3.

FIG. 3 is a second SEM image of the electrode material of example 3.

FIG. 4 is an elemental analysis chart of the electrode material of example 3.

FIG. 5 is a linear voltammogram of hydrogen evolution for the electrode materials of examples 1, 2, and 3 made at different temperatures.

FIG. 6 is a graph of current versus time at 1000 ℃ for the electrode material of example 3.

Detailed Description

In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantages will be described in further detail below with reference to the following detailed description and the accompanying drawings, but the embodiments of the present invention are not limited thereto.