Biomass-based porous tar carbon as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of energy storage materials, and particularly relates to biomass-based porous tar carbon as well as a preparation method and application thereof. The preparation method of the biomass-based porous tar carbon comprises the following steps: mixing biomass pyrolysis tar and ball-milled tar carbon powder, and carrying out flash Joule heat treatment to obtain the biomass-based porous tar carbon, the particle size of the ball-milled tar carbon powder is less than 75 microns. The invention innovatively provides a method for treating the biomass pyrolysis tar by utilizing a flash evaporation Joule thermal conversion technology, so that the use of chemical activators can be reduced, the generation of post-treatment waste liquid is avoided, and the method is environment-friendly. According to the method, the tar-based carbon material is prepared by taking the byproduct pyrolysis tar generated by biomass pyrolysis as a carbon source and the ball-milled tar carbon powder as a conductive agent and a carbon skeleton through a flash Joule thermal conversion technology, and the porous tar carbon with a rich pore structure is prepared in a green and efficient manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage materials, and in particular relates to a biomass-based porous tar carbon and a preparation method and application thereof. Background Art

[0002] Biomass pyrolysis tar is an inevitable by-product produced during the pyrolysis of biomass. The production of pyrolysis tar may cause problems such as pipeline blockage and environmental pollution. The components of pyrolysis tar mainly include aromatic compounds and a small amount of aliphatic compounds. Pyrolysis tar itself has the characteristics of rich carbon and low ash. The tar carbon material prepared by thermochemical conversion has good graphitization characteristics and extremely low ash content (less than 0.5%). However, pyrolysis tar relies on the thermal polymerization reaction between complex components to form carbon materials. The polymerization reaction process will seriously affect the formation of the tar carbon pore structure, which easily causes the tar-based carbon material to have poor pore structure and low specific surface area. In addition, the polymerization reaction intensifies the agglomeration of tar carbon, which directly leads to the tar carbon particle size being too large, which is not conducive to further application. The problems of poor pore structure and low specific surface area of ​​tar-based carbon materials are currently generally solved by secondary thermal conversion of potassium ion chemical activators, such as KOH, KMnO4, etc. However, the post-treatment operation of the potassium ion activator requires acid washing and water washing to remove the excess activator remaining on the surface of the carbon material. The post-treatment process will produce a large amount of waste liquid, which will have an adverse impact on the environment. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a biomass-based porous tar carbon and a preparation method and application thereof. The present invention uses ball milling coupled with flash Joule heat treatment to prepare biomass-based porous tar carbon, does not require the use of potassium ion activator, and is environmentally friendly.

[0004] The present invention provides a method for preparing biomass-based porous tar carbon, comprising the following steps: The biomass pyrolysis tar and ball-milled tar carbon powder are mixed and subjected to flash Joule thermal treatment to obtain biomass-based porous tar carbon; The particle size of the ball-milled tar carbon powder is less than 75 μm.

[0005] Preferably, the mass ratio of the ball-milled tar carbon powder to the biomass pyrolysis tar is 1:10 to 1:20.

[0006] Preferably, the voltage of the flash Joule heat treatment is 100-500 V, the voltage is a pulse voltage, the voltage pulse time interval is 1 μs-1 s, and the time of the flash Joule heat treatment is 1-10 min.

[0007] Preferably, the ball-milled tar carbon powder is obtained by ball-milling tar carbon, the rotation speed of the ball mill is 300-600 rpm, the time is 1-3 hours, and the mass ratio of the tar carbon to the ball-milling medium is 1:4-1:6.

[0008] Preferably, the tar carbon is obtained by polymerizing pyrolyzed tar into carbon, and the polymerization into carbon is carried out in a nitrogen atmosphere, the polymerization into carbon temperature is 300-500° C., and the insulation time is 1-3 hours.

[0009] Preferably, the biomass pyrolysis tar is obtained by condensing gaseous products obtained by pyrolysis of biomass, and the biomass includes one or more of corn straw, wheat straw and cotton straw.

[0010] Preferably, the pyrolysis atmosphere is nitrogen, the pyrolysis temperature is 300-800° C., and the time is 1-3 hours.

[0011] The present invention also provides a biomass-based porous tar carbon obtained by the preparation method described in the above technical solution, wherein the ash content of the biomass-based porous tar carbon is less than 0.1% by weight, and the specific surface area is 1000-2500m 2 / g, and micropores account for 60%~65%.

[0012] The present invention also provides the use of the biomass-based porous tar carbon described in the above technical solution in electrode materials.

[0013] The present invention also provides a working electrode, comprising a base material and a mixture of biomass-based porous tar carbon, a binder and a conductive agent coated on the base material; The biomass-based porous tar carbon is the biomass-based porous tar carbon described in the above technical solution.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The invention provides a method for preparing biomass-based porous tar carbon, comprising the following steps: mixing biomass pyrolysis tar and ball-milled tar carbon powder and subjecting them to flash Joule heat treatment to obtain biomass-based porous tar carbon; the particle size of the ball-milled tar carbon powder is less than 75 μm.

[0015] Flash Joule thermal conversion technology is a thermal conversion technology that uses electric current to pass through raw materials to induce rapid heating. Its principle is to heat the raw materials to several hundred to thousands of degrees Celsius in a very short time, thereby promoting chemical reactions or material conversions. The components of biomass pyrolysis tar are mainly aromatic compounds, which have poor electrical conductivity and cannot be heated instantly using electric current. Moreover, during the rapid heating process, the main components of biomass pyrolysis tar are easily decomposed and overflowed in the form of volatile substances. Therefore, it is difficult to directly convert biomass pyrolysis tar through flash Joule thermal conversion technology to prepare porous tar carbon.

[0016] The present invention innovatively proposes to use flash Joule heat conversion technology to treat biomass pyrolysis tar, and adds ball-milled tar carbon powder to biomass pyrolysis tar. The ball-milled tar carbon powder has good graphitization characteristics and electrical conductivity. In the flash Joule heat conversion process, the ball-milled tar carbon powder can be used as a conductive agent and carbon skeleton in the flash Joule heat conversion process of biomass pyrolysis tar. On the one hand, it improves the conductivity of the raw material (biomass pyrolysis tar), so that the instantaneous heating process can be achieved by electric current. On the other hand, it weakens the adverse effect of volatile overflow on the tar carbon yield. The present invention can reduce the use of chemical activators and avoid the generation of post-treatment waste liquid, which is environmentally friendly. The present invention innovatively proposes a process route combining biomass pyrolysis tar carbonization with flash Joule heat conversion, realizing efficient conversion and high-value utilization of biomass pyrolysis tar.

[0017] Furthermore, the ball milling technology adopted in the present invention can effectively improve the particle size and dispersibility of tar carbon, and further increase the proportion of micropores in tar carbon powder. The obtained ball-milled tar carbon powder is evenly mixed with biomass pyrolysis tar, and the obtained biomass-based porous tar carbon has a large specific surface area and a high proportion of micropores.

[0018] The present invention innovatively uses the pyrolysis tar produced as a byproduct of biomass pyrolysis as a carbon source, ball-milled tar carbon powder as a conductive agent and carbon skeleton, and prepares tar-based carbon materials through flash Joule thermal conversion technology, thereby preparing biomass-based porous tar carbon with rich pore structure in an environmentally friendly and efficient manner. Biomass-based porous tar carbon is used as a supercapacitor electrode material with excellent electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The flowchart of preparing biomass-based porous tar carbon in the examples is shown in FIG. DETAILED DESCRIPTION

[0021] The present invention provides a method for preparing biomass-based porous tar carbon, comprising the following steps: The biomass pyrolysis tar and ball-milled tar carbon powder are mixed and subjected to flash Joule thermal treatment to obtain biomass-based porous tar carbon; The particle size of the ball-milled tar carbon powder is less than 75 μm.

[0022] In the present invention, unless otherwise specified, the materials and equipment used are commercially available products in the art.

[0023] In the present invention, the ball-milled tar carbon powder is preferably obtained by ball-milling tar carbon, and the present invention has no special requirements on the source of the tar carbon; the tar carbon is preferably obtained by polymerizing pyrolysis tar into carbon; The pyrolysis tar is preferably the first biomass pyrolysis tar, which is preferably obtained by condensing the gaseous product obtained by pyrolysis of biomass, and the biomass pyrolysis tar has the characteristic of polymerizing into carbon; the biomass preferably includes one or more of corn straw, wheat straw and cotton straw; the pyrolysis temperature is preferably 300-800°C, more preferably 400-600°C, specifically 500°C, the time is preferably 1-3h, specifically 2h, and the heating rate from room temperature to the pyrolysis temperature is preferably 10°C / min; the pyrolysis atmosphere is preferably nitrogen; The carbon polymerization is preferably carried out in a nitrogen atmosphere, the carbon polymerization temperature is preferably 300-500°C, specifically 300°C, 400°C or 300°C, the holding time is preferably 1-3h, specifically 1h, 2h or 3h; the heating rate from room temperature to the carbon polymerization temperature is preferably 5-10°C / min. The carbon polymerization temperature of the present invention is neither too high, resulting in high volatile matter production and low carbon yield; nor too low, resulting in low graphitization degree of tar carbon and poor conductivity.

[0024] In the present invention, the rotation speed of the ball mill is preferably 300-600 rpm, specifically 300 rpm, 400 rpm or 600 rpm, the time is preferably 1-3 hours, specifically 2 hours, and the mass ratio of the tar carbon to the ball milling medium is preferably 1:4-1:6, specifically 1:4, 1:5 or 1:6. The pulverization further includes screening, and the screening preferably uses a 200 mesh sieve (75 μm).

[0025] The invention mixes biomass pyrolysis tar and ball-milled tar carbon powder and performs flash Joule heat treatment to obtain biomass-based porous tar carbon.

[0026] The present invention has no special requirements for the preparation method of the biomass pyrolysis tar. The biomass pyrolysis tar is preferably obtained by condensing the gaseous product obtained by pyrolysis of biomass; the biomass preferably includes one or more of corn straw, wheat straw and cotton straw; the pyrolysis atmosphere is preferably nitrogen; the pyrolysis temperature is preferably 300-800°C, more preferably 400-600°C, specifically 500°C, the time is preferably 1-3h, specifically 2h, and the heating rate from room temperature to the pyrolysis temperature is preferably 10°C / min. The biomass pyrolysis tar and the pyrolysis tar for preparing tar carbon may be the same or different.

[0027] In the present invention, the mass ratio of the ball-milled tar carbon powder to the biomass pyrolysis tar is preferably 1:10 to 1:20, and specifically can be 1:10 or 1:20. The mass ratio of the ball-milled tar carbon powder to the biomass pyrolysis tar of the present invention provides a mixed raw material with good electrical conductivity, which can achieve Joule heat conversion, and the obtained product has a large specific surface area and high specific capacitance.

[0028] In the present invention, the flash Joule heat treatment is preferably carried out in a pulsed electric flash Joule heat reactor. The flash Joule heat treatment is preferably carried out under constant pressure, and the voltage of the flash Joule heat treatment is preferably 100-500V, more preferably 200-400V, specifically 200V, 300V or 400V; the voltage is a pulse voltage, and the voltage pulse time interval is preferably 1μs-1s, more preferably 300-500ms, specifically 300ms, 400ms or 500ms; the time of the flash Joule heat treatment is preferably 1-10min, more preferably 1-3min, specifically 1min, 2min or 3min.

[0029] During the flash Joule heat treatment process, rapid heating causes a portion of the organic components in the raw material (small molecular oxygen-containing components with a carbon number less than 10) to quickly decompose and produce volatile substances, and the other portion is converted (heavy components are polymerized) into carbon materials. The overflow of volatile substances promotes the formation of the pore structure of the carbon material, and ultimately produces a carbon material with a high specific surface area and porosity, which is beneficial to improving the energy storage performance of the carbon material.

[0030] The present invention also provides a biomass-based porous tar carbon obtained by the preparation method described in the above technical solution, wherein the ash content of the biomass-based porous tar carbon is less than 0.1% by weight, and the specific surface area is 1000-2500m 2 / g, and micropores account for 60%~65%.

[0031] In the present invention, the ash content of the biomass-based porous tar carbon is preferably 0.05% by weight, and the specific surface area is preferably 2172~2437m 2 / g, the micropore ratio is preferably 60% to 64%. The micropores are pores with a pore diameter less than 2nm, and the micropore ratio is the ratio of the micropore volume to the total pore volume.

[0032] The present invention also provides the use of the biomass-based porous tar carbon described in the above technical solution in electrode materials.

[0033] The present invention also provides a working electrode, comprising a base material and a mixture of biomass-based porous tar carbon, a binder and a conductive agent coated on the base material; The biomass-based porous tar carbon is the biomass-based porous tar carbon described in the above technical solution.

[0034] In the present invention, the binder is preferably polyvinylidene fluoride, and the conductive agent is preferably acetylene black; the mass ratio of the biomass-based porous tar carbon, polyvinylidene fluoride and acetylene black is preferably 8:1:1.

[0035] In the present invention, the substrate material is preferably highly conductive graphite paper. The preparation method of the working electrode preferably comprises: mixing and grinding biomass-based porous tar carbon, a binder and a conductive agent, dripping the obtained thick slurry on the substrate material, and drying to obtain a working electrode; the drying temperature is preferably 60° C., and the drying time is preferably 12 hours.

[0036] The working electrode of the present invention has a specific capacitance of >350 F / g at a current density of 0.5 A / g under the condition of a three-electrode system (the reference electrode is a saturated calomel electrode and the counter electrode is a platinum foil) and KOH as an electrolyte, and a specific capacitance retention rate of >95% after 5000 cycles. The electrochemical performance of biomass-based porous tar carbon used as supercapacitor electrode material is significantly better than that of ordinary commercial activated carbon.

[0037] In order to further illustrate the present invention, the biomass-based porous tar carbon and its preparation method and application provided by the present invention are described in detail below in combination with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0038] In the embodiments or comparative examples of the present invention, the corn straw pyrolysis tar used was collected by condensing the gaseous product of corn straw pyrolysis at 500°C (in a nitrogen atmosphere, the heating rate was 10°C / min, and the 500°C holding time was 2h); the reference electrode of the three-electrode system was a saturated calomel electrode, and the counter electrode was a platinum foil. Figure 1 As shown in the flow chart, biomass-based porous tar carbon was prepared and used as an energy storage material to prepare a working electrode for electrochemical performance testing.

[0039] Example 1 (1) Using corn straw pyrolysis tar as raw material to prepare tar carbon by polymerization: The carbon polymerization reaction was carried out in a nitrogen atmosphere at a temperature of 300°C, a heating rate of 10°C / min, and a holding time of 2 h.

[0040] (2) Preparing ball-milled tar carbon powder by ball milling: The ball milling speed was 400 rpm, the ball milling time was 2 h, the mass ratio of tar carbon to ball milling medium was 1:5, and the product was sieved through a 200-mesh sieve.

[0041] (3) The corn straw pyrolysis tar and ball-milled tar carbon powder are then mixed and placed in a pulsed electric flash Joule thermal reactor for thermochemical conversion to obtain porous tar carbon: The mass ratio of ball-milled tar carbon powder to corn straw pyrolysis tar was 1:10. Constant-pressure Joule thermal treatment was carried out at a voltage of 400 V, a voltage pulse time interval of 400 ms, and a flash Joule thermal treatment time of 2 min.

[0042] The porous tar carbon prepared in Example 1 has an ash content of 0.05% by mass and a specific surface area of ​​2437 m 2 / g, and micropores account for 64%.

[0043] Application Example 1 The porous tar carbon, polyvinylidene fluoride and acetylene black prepared in Example 1 were ground in a mass ratio of 8:1:1, and the ground thick slurry was dropped on a highly conductive graphite paper, and placed in an oven at 60° C. for 12 h to obtain a working electrode.

[0044] Under the conditions of a three-electrode system, with KOH as the electrolyte, the specific capacitance at a current density of 0.5 A / g can reach 357F / g, and the specific capacitance retention rate after 5000 cycles is 95.3%. The electrochemical performance of porous tar carbon used as supercapacitor electrode material is better than that of ordinary commercial activated carbon (specific capacitance is 100~250F / g, such as commercial coconut shell activated carbon with a maximum of 235F / g).

[0045] Example 2 (1) Using corn straw pyrolysis tar as raw material to prepare tar carbon by polymerization: The carbon polymerization reaction was carried out in a nitrogen atmosphere at a temperature of 500°C, a heating rate of 10°C / min, and a holding time of 2 h.

[0046] (2) Preparing ball-milled tar carbon powder by ball milling: The ball milling speed was 400 rpm, the ball milling time was 2 h, the mass ratio of tar carbon to ball milling medium was 1:5, and the product was sieved through a 200-mesh sieve.

[0047] (3) The corn straw pyrolysis tar and ball-milled tar carbon powder are then mixed and placed in a pulsed electric flash Joule thermal reactor for thermochemical conversion to obtain porous tar carbon: The mass ratio of ball-milled tar carbon powder to corn straw pyrolysis tar was 1:20. Constant-pressure Joule thermal treatment was carried out at a voltage of 300 V, a voltage pulse time interval of 300 ms, and a flash Joule thermal treatment time of 2 min.

[0048] The porous tar carbon prepared in Example 2 has an ash content of 0.05% by mass and a specific surface area of ​​2172 m 2 / g, and micropores account for 60%.

[0049] Application Example 2 The porous tar carbon, polyvinylidene fluoride and acetylene black prepared in Example 2 were ground in a mass ratio of 8:1:1, and the ground thick slurry was dropped on a highly conductive graphite paper, and placed in an oven at 60° C. for 12 h to obtain a working electrode.

[0050] Under the conditions of a three-electrode system, with KOH as the electrolyte, the specific capacitance at a current density of 0.5 A / g can reach 352F / g, and the specific capacitance retention rate after 5000 cycles is 95.1%. The electrochemical performance of porous tar carbon used as supercapacitor electrode material is better than that of ordinary commercial activated carbon.

[0051] Comparative Example 1 (1) Using corn straw pyrolysis tar as raw material to prepare tar carbon by polymerization: The carbon polymerization reaction was carried out in a nitrogen atmosphere at a temperature of 500°C, a heating rate of 10°C / min, and a holding time of 2 h.

[0052] (2) The corn straw pyrolysis tar and tar carbon are mixed and placed in a pulsed electric flash Joule thermal reactor for thermochemical conversion to obtain porous tar carbon: The mass ratio of ball-milled tar carbon to corn straw pyrolysis tar was 1:10. Constant-pressure Joule thermal treatment was carried out at a voltage of 400 V, a voltage pulse time interval of 400 ms, and a flash Joule thermal treatment time of 2 min.

[0053] The porous tar carbon prepared in Example 1 has an ash content of 0.05% by mass and a specific surface area of ​​1372 m 2 / g, and micropores account for 57%.

[0054] Comparative application example 1 The porous tar carbon, polyvinylidene fluoride and acetylene black prepared in Comparative Example 1 were ground in a mass ratio of 8:1:1, and the ground thick slurry was dropped on a highly conductive graphite paper and placed in an oven at 60° C. for 12 h to obtain a working electrode.

[0055] Under the conditions of the three-electrode system, with KOH as the electrolyte, the specific capacitance at a current density of 0.5 A / g is 234 F / g, and the specific capacitance retention rate is 90% after 5000 cycles. Compared with Example 1, Comparative Example 1 does not have a ball milling step, and the pore characteristics and electrochemical performance of the porous tar carbon are poor.

[0056] Comparative Example 2 (1) Using corn straw pyrolysis tar as raw material to prepare tar carbon by polymerization: The carbon polymerization reaction was carried out in a nitrogen atmosphere at a temperature of 500°C, a heating rate of 10°C / min, and a holding time of 2 h.

[0057] (2) Preparing ball-milled tar carbon powder by ball milling: The ball milling speed was 400 rpm, the ball milling time was 2 h, the mass ratio of tar carbon to ball milling medium was 1:5, and the product was sieved through a 200-mesh sieve.

[0058] The ball-milled tar carbon powder obtained in Comparative Example 2 has an ash content of 0.05% and a specific surface area of ​​391 m 2 / g, and micropores account for 30%.

[0059] Comparative Application Example 2 The ball-milled tar carbon, polyvinylidene fluoride and acetylene black prepared in Comparative Example 2 were ground in a mass ratio of 8:1:1, and the ground thick slurry was dropped onto a highly conductive graphite paper and placed in an oven at 60° C. for 12 h to obtain a working electrode.

[0060] Under the conditions of a three-electrode system with KOH as the electrolyte, the specific capacitance is 63 F / g at a current density of 0.5 A / g, and the specific capacitance retention rate is 80% after 5000 cycles.

[0061] Compared with Example 1, Comparative Example 2 does not have the flash Joule heat conversion step, and the porosity characteristics and electrochemical performance of the ball-milled tar carbon are poor.

[0062] Comparative Example 3 (1) Using corn straw pyrolysis tar as raw material to prepare tar carbon by polymerization: The carbon polymerization reaction was carried out in a nitrogen atmosphere at a temperature of 500°C, a heating rate of 10°C / min, and a holding time of 2 h.

[0063] (2) Preparing ball-milled tar carbon powder by ball milling: The ball milling speed was 400 rpm, the ball milling time was 2 h, the mass ratio of tar carbon to ball milling medium was 1:5, and the product was sieved through a 200-mesh sieve.

[0064] (3) The corn straw pyrolysis tar and ball-milled tar carbon powder are then mixed and placed in a pulsed electric flash Joule thermal reactor for thermochemical conversion to obtain porous tar carbon: The mass ratio of ball-milled tar carbon powder to corn straw pyrolysis tar was 1:5. Constant-pressure Joule thermal treatment was carried out at a voltage of 400 V, a voltage pulse time interval of 400 ms, and a flash Joule thermal treatment time of 2 min.

[0065] The porous tar carbon prepared in Example 3 has an ash content of 0.05% by mass and a specific surface area of ​​832 m 2 / g, and micropores account for 41%.

[0066] Comparative Application Example 3 The porous tar carbon, polyvinylidene fluoride and acetylene black prepared in Comparative Example 3 were ground in a mass ratio of 8:1:1, and the ground thick slurry was dropped on a highly conductive graphite paper and placed in an oven at 60° C. for 12 h to obtain a working electrode.

[0067] Under the conditions of the three-electrode system, with KOH as the electrolyte, the specific capacitance at a current density of 0.5 A / g is 207 F / g, and the specific capacitance retention rate is 90% after 5000 cycles. Compared with Example 1, the mass ratio of ball-milled tar carbon and corn straw pyrolysis tar in Comparative Example 3 is too high, and the pore characteristics and electrochemical performance of the porous tar carbon are poor.

[0068] Although the above-mentioned embodiments have made a detailed description of the present invention, they are only some embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on the embodiments of the present invention without creative work, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing biomass-based porous tar carbon, characterized in that: The following steps are involved: The biomass pyrolysis tar and ball-milled tar carbon powder are mixed and subjected to flash Joule thermal treatment to obtain biomass-based porous tar carbon; The particle size of the ball-milled tar carbon powder is less than 75 μm.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the ball-milled tar carbon powder to the biomass pyrolysis tar is 1:10-1:

20.

3. The preparation method according to claim 1 or 2, characterized in that: The voltage of the flash Joule heat treatment is 100-500V, the voltage is a pulse voltage, the voltage pulse time interval is 1μs-1s, and the time of the flash Joule heat treatment is 1-10min.

4. The preparation method according to claim 1, characterized in that: The ball-milled tar carbon powder is obtained by ball-milling tar carbon, the rotation speed of the ball mill is 300-600 rpm, the time is 1-3 hours, and the mass ratio of the tar carbon to the ball-milling medium is 1:4-1:

6.

5. The preparation method according to claim 4, characterized in that: The tar carbon is obtained by polymerizing pyrolyzed tar into carbon, and the polymerization into carbon is carried out in a nitrogen atmosphere. The temperature of the polymerization into carbon is 300-500° C., and the insulation time is 1-3 hours.

6. The preparation method according to claim 1, characterized in that: The biomass pyrolysis tar is obtained by condensing a gaseous product obtained by pyrolysis of biomass, wherein the biomass includes one or more of corn straw, wheat straw and cotton straw.

7. The preparation method according to claim 6, characterized in that: The pyrolysis atmosphere is nitrogen, the pyrolysis temperature is 300-800° C., and the time is 1-3 hours.

8. The biomass-based porous tar carbon obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The ash content of the biomass-based porous tar carbon is less than 0.1% by weight, and the specific surface area is 1000-2500m 2 / g, and micropores account for 60%~65%.

9. Use of the biomass-based porous tar carbon according to claim 8 in electrode materials.

10. A working electrode, characterized in that: A mixture comprising a base material and biomass-based porous tar carbon, a binder and a conductive agent coated on the base material; The biomass-based porous tar carbon is the biomass-based porous tar carbon according to claim 8.

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