CN111362250A - High specific capacitance super-thick biochar, biochar monolithic electrode and biochar composite electrode - Google Patents
High specific capacitance super-thick biochar, biochar monolithic electrode and biochar composite electrode Download PDFInfo
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- 238000010411 cooking Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- 229910000314 transition metal oxide Inorganic materials 0.000 claims description 3
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- 239000003990 capacitor Substances 0.000 abstract description 11
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- 230000001070 adhesive effect Effects 0.000 abstract 1
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- 238000007599 discharging Methods 0.000 description 7
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- C01B32/00—Carbon; Compounds thereof
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- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
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- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
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- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
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Abstract
The invention discloses high specific capacitance super-thick biochar, a biochar single-chip electrode and a biochar composite electrode, and belongs to the technical field of high-value resource utilization of biomass solid waste and preparation of supercapacitor electrodes. The invention takes the whole natural wood as the initial raw material, and prepares a series of super-thick biochar monolithic electrodes with high stability, high specific volume capacitance and no adhesive based on a continuous biological structure or super-thick composite monolithic composite electrodes after loading metal oxides by low-speed pyrolysis or surface solvation pretreatment, densification extrusion and low-speed pyrolysis. The obtained monolithic electrode and the composite monolithic electrode have excellent conductivity, high specific capacitance and excellent rate performance, can be directly applied to a high specific volume capacitance super capacitor, and are beneficial to assembly, miniaturization and performance improvement of the super capacitor.
Description
Technical Field
The invention belongs to the field of high-value resource utilization of biomass solid waste and preparation of high-performance green supercapacitor electrode materials, and particularly relates to a stable high-specific-capacitance ultra-thick biochar monolithic electrode and a composite electrode material.
Background
In recent years, the popularization of portable electronic devices and the use of clean energy have led to an unprecedented rapid development of high-performance energy storage devices. Supercapacitors are currently of considerable interest as the best energy storage technology. As the most important component in the super capacitor, the quality of the electrode largely determines the overall performance of the super capacitor. Researchers have made a great deal of research in the field of development of high-performance electrode materials, and developed various electrode materials including carbon-based, metal oxides, and composites of the two.
However, most studies have not been considered from the viewpoint of capacitor devices, and the prepared electrode active material is generally in a powder state, and a certain binder needs to be mixed to prepare a usable electrode. However, the addition of the binder causes the overall conductivity of the electrode to be poor, so that the thin film electrode is frequently used in the assembly of the supercapacitor, which not only causes the utilization rate of the electrode active material to be low, but also causes the assembly process of the capacitor to be difficult, and causes the volume of the capacitor to be large. Currently, the improvement of electrode thickness has become a bottleneck problem in the research and application of supercapacitors.
Disclosure of Invention
In order to overcome the problems, the invention provides a biochar which is based on a continuous biological structure, has high stability and high specific volume capacitance and is free from a bonding agent and is prepared by taking natural wood as a whole as a starting material through low-rate pyrolysis or pretreatment and low-rate pyrolysis, and the biochar is used for an ultra-thick biochar single-chip electrode and a composite electrode for a super capacitor.
The invention firstly provides biochar which is prepared by the following method:
A. preparing raw materials: cutting wood into wood blocks, and drying to obtain dried wood blocks;
B. pyrolysis: pyrolyzing the dried wood blocks under the protection of inert gas to obtain biochar; the pyrolysis is controlled in the following manner: in the pyrolysis process, when the temperature is lower than 200 ℃, the heating rate is not more than 60 ℃/h, and then the material stays at the constant temperature of 200 +/-10 ℃ for 2-6 h; when the temperature is between 200 ℃ and 600 ℃, the heating rate is 15-30 ℃/h, and when the temperature is higher than 600 ℃, the heating rate is 20-40 ℃/h; after the temperature is raised to 200 +/-10 ℃, keeping the pyrolysis temperature for 0.1-0.3 h at a constant temperature of 200 ℃ every time when the pyrolysis temperature is raised (namely keeping the temperature for 0.1-0.3 h when the temperature is raised to 200n +/-10 ℃ (n is more than or equal to 2)), and then continuing to raise the temperature; the final temperature of the pyrolysis process is not lower than 800 ℃.
Wherein, in the step A, the drying temperature of the biochar is 60-100 ℃.
On the basis of the biochar, the invention also provides biochar with more excellent performance, which is prepared by the following method:
a. preparing raw materials: cutting wood into wood blocks, and drying to obtain dried wood blocks;
b. surface solvation pretreatment: preparing a mixed solution of sodium sulfite and sodium hydroxide, heating to boil, then placing the dried wood block into the mixed solution for cooking, and carrying out surface solvation pretreatment;
c. surface cleaning: washing the wood blocks subjected to surface solvent treatment to remove sodium hydroxide and sodium sulfite remained on the wood blocks;
d. densification: carrying out densification and extrusion treatment on the cleaned wood block, and then drying the extruded wood block;
e. pyrolysis: pyrolyzing the extruded and dried wood blocks under the protection of inert gas to obtain biochar; the pyrolysis is controlled in the following manner: in the pyrolysis process, when the temperature is lower than 200 ℃, the heating rate is not more than 60 ℃/h, and then the material stays at the constant temperature of 200 +/-10 ℃ for 2-6 h; when the temperature is between 200 ℃ and 600 ℃, the heating rate is 15-30 ℃/h, and when the temperature is higher than 600 ℃, the heating rate is 20-40 ℃/h; after the temperature is raised to 200 +/-10 ℃, keeping the pyrolysis temperature for 0.1-0.3 h at a constant temperature of 200 ℃ every time when the pyrolysis temperature is raised (namely keeping the temperature for 0.1-0.3 h when the temperature is raised to 200n +/-10 ℃ (n is more than or equal to 2)), and then continuing to raise the temperature; the final temperature of the pyrolysis process is not lower than 800 ℃.
Wherein, in the step b, the total concentration of the mixed solution of sodium hydroxide and sodium sulfite is 2-4 mol/L, wherein the molar concentration ratio of sodium hydroxide to sodium sulfite is 8-5: 1.
wherein, in the step b, the surface solvation pretreatment time of the biochar is 2-8 h.
Preferably, in the biochar, in the step b, the time for surface solvation pretreatment is 4-6 h.
And c, boiling and washing the wood blocks subjected to surface solvent treatment in boiled deionized water for not less than 10min for a single time, wherein the boiling and washing times are not less than 6 times.
In the step d, during the densification extrusion treatment, the extrusion pressure is 3-8 MPa, and the extrusion time is 12-24 hours.
Preferably, in the biochar, in the step d, the extrusion pressure is 4-6 MPa during the densification extrusion treatment.
Further, on the basis of the two biochar, the biochar single-chip electrode is prepared and prepared by slicing and grinding the two biochar.
Wherein, the thickness of the biochar monolithic electrode is not less than 600 mu m.
Further, RuO is loaded by taking the biochar single chip as a carrier2NiO and MnO2And the biological carbon/metal oxide composite electrode can be prepared by using the transition metal oxide.
The invention has the beneficial effects that:
firstly, the invention directly adopts the wood block with the complete and continuous natural biological structure of the tree as the raw material, ensures that the biochar can be directly molded after pyrolysis, avoids the use of a binder in the process of preparing the electrode by using a conventional powdery material, and ensures that the continuous biological structure of the biochar is not damaged by accurately controlling the heating rate and the constant-temperature carbonization time in the slow pyrolysis process, so that the biochar (and the monolithic electrode thereof) has excellent conductivity and electrochemical stability.
And then, further optimizing the preparation process, removing partial lignin and hemicellulose in the natural wood structure by adopting surface solvent treatment to ensure that the continuous structure of the natural wood is not damaged in the densification and extrusion process, and simultaneously enhancing the interaction between contact surfaces in the extrusion process by surface solvent modification to realize the stable maintenance of the densification structure so as to prepare the ultra-thick biochar monolithic electrode with ultrahigh specific volume capacitance.
Through raw material selection, surface solvent treatment, densification extrusion and/or pyrolysis control, the biochar (and a single-chip electrode) has the following advantages: the material has a continuous natural biological structure, so that the material has excellent conductivity which is comparable to that of a single graphite crystal; the electrode has low curvature of a pore structure, so that the transmission of electrolyte in the charge and discharge process is facilitated, and higher specific capacitance and excellent rate performance are obtained; the high-performance super-thick super capacitor electrode can be prepared, and the assembly and miniaturization of the super capacitor are facilitated; the specific volume capacitance of the electrode is obviously improved and is 3.3 times that of an untreated single-chip electrode under the same condition.
Finally, the biochar single chip can also be used as a carrier to load metal oxide to prepare a composite electrode, and the metal oxide has a pseudo-capacitance utilization rate which is obviously superior to that of a powder carrier electrode.
Drawings
FIG. 1 is a physical diagram of the biochar obtained in example 1 and an SEM diagram of a single-chip electrode of the biochar; wherein a is a real object image of the biochar, and b-e are SEM images of the biochar single-chip electrode.
FIG. 2 is a constant current charge and discharge curve, a capacitance data graph and a cycle stability graph of the biochar monolithic electrode obtained in example 1; wherein a is a constant current charging and discharging curve of the biochar monolithic electrode under different current densities, b is a capacitance data graph of the biochar monolithic electrode under different current densities, and c is a recycling stability graph of the biochar monolithic electrode.
FIG. 3 is an SEM photograph of the biochar monolithic electrode obtained in example 2.
FIG. 4 is a constant current charge and discharge curve, a capacitance data graph and a cycle stability graph of the biochar monolithic electrode obtained in example 2; wherein a is a constant current charging and discharging curve of the biochar monolithic electrode under different current densities, b is a capacitance data graph of the biochar monolithic electrode under different current densities, and c is a recycling stability graph of the biochar monolithic electrode.
FIG. 5 is a constant current charge and discharge curve, a capacitance data graph and a cycle stability graph of the biochar monolithic electrode obtained in example 3; wherein a is a constant current charging and discharging curve of the biochar monolithic electrode under different current densities, b is a capacitance data graph of the biochar monolithic electrode under different current densities, and c is a recycling stability graph of the biochar monolithic electrode.
FIG. 6 shows RuO in example 42(x) @ MBC electrode specific volume capacitance diagram, RuO2(x) @ MBC electrode surface RuO2Specific mass capacitance and RuO2(24.76) @ MBC electrode electrochemical stability profile; wherein a is different RuO2Capacity of RuO2(x) Specific volume capacitance diagram of @ MBC electrode, b is RuO with different loading capacity2RuO of (2)2(x) @ MBC electrode surface RuO2C is RuO2(24.76) @ MBC electrode cycling stability graph.
Detailed Description
Specifically, the biochar is prepared by the following method:
A. preparing raw materials: cutting wood into wood blocks, and drying to obtain dried wood blocks;
B. pyrolysis: pyrolyzing the dried wood blocks under the protection of inert gas to obtain biochar; the pyrolysis is controlled in the following manner: in the pyrolysis process, when the temperature is lower than 200 ℃, the heating rate is not more than 60 ℃/h, then the mixture stays at the constant temperature of 200 +/-10 ℃ for 2-6 h, when the temperature is between 200 ℃ and 600 ℃, the heating rate is 15-30 ℃/h, and when the temperature is higher than 600 ℃, the heating rate is 20-40 ℃/h; after the temperature is raised to 200 +/-10 ℃, keeping the pyrolysis temperature for 0.1 to 0.3h at a constant temperature of 200 ℃ every time, and then continuously raising the temperature (namely keeping the temperature for 0.1 to 0.3h when the temperature is raised to 200n +/-10 ℃ (n is more than or equal to 2)); the final temperature of the pyrolysis process is not lower than 800 ℃.
In the invention, the raw material wood is mainly from cork seeds such as white pine, birch, zelkova and the like, and the raw material wood has a complete and continuous natural biological structure of the tree. The raw material wood is generally cut into blocks (for example, the blocks are cut into 2x2x 2-6 x12x12 cm) and then dried at 60-100 ℃ for 12-24 hours.
During pyrolysis, in order to ensure that the continuous biological structure of the biochar is not damaged, the temperature rise rate and the constant temperature carbonization time of the slow pyrolysis process need to be accurately controlled.
Tests show that although the biochar (and the single-chip electrode) obtained through pyrolysis program control has excellent conductivity and electrochemical stability, the capacitance characteristics are poor, and the charge-discharge efficiency is low; therefore, the inventor carries out further optimization on the basis of the biochar.
The invention also provides a biochar with more excellent performance, which is prepared by the following method:
a. preparing raw materials: cutting wood into wood blocks, and drying to obtain dried wood blocks;
b. surface solvation pretreatment: preparing a mixed solution of sodium sulfite and sodium hydroxide, heating to boil, then placing the dried wood block into the mixed solution for cooking, and carrying out surface solvation pretreatment;
c. surface cleaning: washing the wood blocks subjected to surface solvent treatment to remove sodium hydroxide and sodium sulfite remained on the wood blocks;
d. densification: carrying out densification and extrusion treatment on the cleaned wood block, and then drying the extruded wood block;
e. pyrolysis: pyrolyzing the extruded and dried wood blocks under the protection of inert gas to obtain biochar; the pyrolysis is controlled in the following manner: in the pyrolysis process, when the temperature is lower than 200 ℃, the heating rate is not more than 60 ℃/h, and then the material stays at the constant temperature of 200 +/-10 ℃ for 2-6 h; when the temperature is between 200 ℃ and 600 ℃, the heating rate is 15-30 ℃/h, and when the temperature is higher than 600 ℃, the heating rate is 20-40 ℃/h; after the temperature is raised to 200 +/-10 ℃, keeping the pyrolysis temperature for 0.1 to 0.3h at a constant temperature of 200 ℃ every time, and then continuously raising the temperature (namely keeping the temperature for 0.1 to 0.3h when the temperature is raised to 200n +/-10 ℃ (n is more than or equal to 2)); the final temperature of the pyrolysis process is not lower than 800 ℃.
In the step b, the main function of the surface solvent treatment is to remove part of lignin and hemicellulose in the natural wood structure so as to ensure that the continuous structure of the natural wood is not damaged in the densification and extrusion process, and meanwhile, the interaction between contact surfaces in the extrusion process is enhanced through surface solvent modification so as to realize the stable maintenance of the densified structure. Experiments show that the total concentration of a mixed solution of sodium hydroxide and sodium sulfite needs to be controlled to be 2-4 mol/L, wherein the molar concentration ratio of the sodium hydroxide to the sodium sulfite is 8-5: 1.
in the step b, the surface solvation pretreatment needs to be carried out under the condition of cooking, and the treatment time is 2-8 hours; preferably 4-6 h.
Residual sodium hydroxide and sodium sulfite on the wood block can affect the structural integrity and surface chemical characteristics of the biochar, so that the biochar needs to be washed as clean as possible; therefore, in the step c, the wood blocks subjected to surface solvent treatment are boiled and washed in boiled deionized water, the time of single boiling and washing is not less than 10min, and the boiling and washing times are not less than 6 times.
In the step d, during the densification extrusion treatment, the extrusion pressure is 3-8 MPa (preferably 4-6 MPa), and the extrusion time is 12-24 h; otherwise, the goal of effective densification and maintenance of the intact natural biological structure in the biochar cannot be achieved at the same time. In addition, the mould for extrusion is heated to a constant temperature by using boiling water while the wood block is boiled and washed, and then the washed wood block is quickly transferred to an extruder, so that the performance of the obtained charcoal is more excellent.
Further, on the basis of the two biochar, the biochar single-chip electrode is prepared and prepared by slicing and grinding the two biochar.
Because the biochar has a natural biological structure, the biochar can be sliced and polished into corresponding size specifications according to needs to prepare the biochar monolithic electrode, and the thickness of the biochar monolithic electrode is generally not less than 600 mu m.
Further, RuO is loaded by taking the biochar single chip as a carrier2NiO and MnO2And the biological carbon/metal oxide composite electrode can be prepared by using the transition metal oxide.
The present invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
Example 1
A. Cutting white pine wood serving as a raw material into square wood blocks of 2x1x4 inches, and drying at 60 ℃ for 6 hours for later use;
B. the dried wood blocks are placed in a vertical tubular furnace and pyrolyzed in a high-purity nitrogen atmosphere, and the pyrolysis temperature rise process is shown in table 1:
TABLE 1 pyrolytic warming Process parameters for biochar preparation
C. And (4) grinding the whole biochar slice obtained by pyrolysis to prepare a 15x10x1.2mm single-chip electrode which is marked as MBC.
The prepared conventional MBC biochar block is shown in figure 1a, the natural biological structure of the white pine is not damaged by slow pyrolysis, and the prepared biochar has a complete and continuous structure. FIGS. 1b to e are SEM images of BMC electrodes, and it can be seen from FIGS. 1b to e that biochar almost completely maintains the natural biological structure of wood, and the pore walls and other parts of biochar are continuously and completely maintained.
The electrode test is carried out by adopting a three-electrode system, wherein a nickel screen is used as a current collector, Hg/HgO/OH & lt- & gt is used as a reference electrode, 4M KOH is used as an electrolyte, and the test voltage range is-0.8-0.1V; the results are shown in FIG. 2.
Fig. 2 shows charge and discharge curves and capacitance data for different current densities of MBC electrodes. Wherein, fig. 2a is a constant current charging and discharging curve of MBC under different current densities, fig. 2b is capacitance data of MBC under different current densities, and fig. 2c is cycle use stability of MBC electrode.
Fig. 2a shows that the BMC electrode has some electrochemical reaction processes during charging and discharging, ideal capacitance characteristics are poor, and charging and discharging efficiency is low. As can be seen from FIG. 2b, the specific volume capacitance at a current density of 50mA/g was 23.46F/cm3The corresponding energy density and power density are respectively 2.09Wh/L and 6.16W/L; the rate capability of BMC is poor, and when the point current density is increased to 500mA/g, the BMC only maintains about 50% of capacitance; however, as shown in FIG. 2c, MBC has good electrochemical stability and maintains 95.1% of the capacitance after 1000 times of charge and discharge.
Example 2
A. Cutting white pine wood serving as a raw material into square wood blocks of 2x1x2 inches, and drying at 60 ℃ for 6 hours for later use;
B. preparing a mixed solution of sodium hydroxide and sodium sulfite according to a molar concentration ratio of 5/1 and a total concentration of 2.9M, and then heating the mixed solution in a conical flask to boil;
C. putting the dried wood blocks into the mixed solution, and keeping the solution boiling to continuously cook the wood blocks for 6 hours;
D. transferring the steamed wood blocks into boiled deionized water for repeated boiling and cleaning, wherein the boiling and cleaning time is 10min each time, and repeating for 6 times;
E. heating an extrusion die to a constant temperature by using boiling water while boiling and washing wood blocks, then quickly placing the wood blocks into the die, applying 5MPa pressure to extrude the wood blocks by using a tablet press, keeping the extrusion process for 12 hours to ensure that the wood blocks are stably densified, and drying the compacted wood blocks after extrusion treatment at 60 ℃ for later use;
F. the treated compact wood block was pyrolyzed and carbonized, the thermal temperature rise process was as in table 1 in example 1, and the obtained charcoal slices were ground to make 15 × 10 × 1.2mm monolithic electrodes, which were denoted as IMBC.
FIG. 3 shows an SEM representation of IMBC without disruption of its continuous structure by the surface solvation treatment and densification treatment. No slit lamp failure was observed in the axial partition walls. However, the pore wall coating shown in fig. 1 is damaged due to surface solvation treatment, as shown in fig. 3g and h, the monolithic electrode made of the biochar has better connectivity inside, and can further strengthen the transmission of electrolyte ions in the electrode charging and discharging processes, so that the rate capability of the electrode is enhanced.
The electrochemical specificity of the IMBC electrodes was tested using the same three-electrode system as in example 1 and the results are shown in figure 4. Fig. 4a is a constant current charge and discharge curve of the IMBC at different current densities, fig. 4b is capacitance data of the IMBC at different current densities, and fig. 4c is cycle stability of the IMBC electrode.
As shown in FIG. 4a, the treated IMBC has a more perfectly symmetric charge-discharge curve than MBC, and the charge-discharge time at the same current density is longer, as shown in the tableThe lithium ion battery has higher electricity storage capacity, and the charge-discharge efficiency is obviously improved. As can be seen from FIG. 4b, the specific volume capacitance of the IMBC electrode is 77.96F/cm when the current is 50mA/g3The maximum energy density is 6.93Wh/L (13.09W/L); the rate capability of the IMBC electrode is also better, and when the current density is increased to 500mA/g, the specific volume capacitance of the IMBC is 63.14F/cm3At this time, the energy density was 5.61Wh/L (178.81 Wh/L). As can be seen from fig. 4c, the electrochemical stability of IMBC was good, and 100% of the capacitance was maintained after 1000 times of charge and discharge.
Example 3
The biochar monolithic electrode, marked as IMBC-1, was prepared using pine as the raw material, the pyrolysis conditions are as shown in Table 2, and the rest of the operations were the same as in example 2.
TABLE 2 pyrolytic warming process parameters for biochar preparation
The IMBC-1 electrode was tested for electrochemical specificity using the same three-electrode system as in example 1, and the results are shown in FIG. 5. Wherein, fig. 5a is a constant current charge and discharge curve of the IMBC-1 under different current densities, fig. 5b is capacitance data of the IMBC-1 under different current densities, and fig. 5c is the cycling stability of the electrode of the IMBC-1.
As shown in FIG. 5a, IMBC-1 has an almost symmetrical constant current charge and discharge curve, indicating that IMBC-1 has typical ideal capacitor characteristics, and the charge and discharge time is significantly increased compared to BMC, indicating that it has a larger capacitance. As shown in FIG. 5b, the specific capacitance of IMBC-1 was 95.28F/g at a current density of 50mA/g, which showed no significant improvement over BMC, but the specific volume capacitance increased from 42.50F/cm3(ii) a The rate performance and stability of IMBC-1 are also obviously superior to those of a BMC electrode, and the specific volume capacitance is only reduced by 14.6% when the current density is increased to 500 mA/g; as is clear from FIG. 5c, IMBC-1 has good electrochemical stability, and retains 97.8% of its capacitance after 1000 times of charge and discharge.
Example 4
The biochar monolithic electrode prepared in example 1 was used as a support, andloading of different amounts of RuO by liquid deposition2·H2O to RuO2(x) @ MBC composite electrode, where x represents RuO2·H2The specific preparation process of the load (%) of O is as follows:
A. 10mL of RuCl with the concentration of 0.01, 0.02, 0.04, 0.08 and 0.20mol/L are respectively prepared3A solution;
B. the electrode after polishing and cleaning is placed in the RuCl3Dipping in the solution for 48h at 60 ℃ under the assistance of vacuum;
C. from true RuCl3Taking out the biochar single chip from the solution, wiping off surface moisture by using filter paper, and transferring the biochar single chip into 5mL of 0.1mol/L sodium hydroxide solution for reaction for 24 hours;
D. the carbon monolith was removed from the solution, then repeatedly rinsed with deionized water by soaking to remove residual sodium hydroxide, and adsorbed with filter paper to remove excess water from its surface. Then the impregnated single carbon is quickly placed in a constant-temperature oven at 150 ℃ for 6h to prepare RuO2(x) @ MBC composite electrode.
RuO testing Using the same three-electrode System as in example 12(x) The electrochemical results of the @ MBC composite electrode are shown in FIG. 6.
Wherein FIG. 6a shows different RuOs2Capacity of RuO2(x) @ MBC composite electrode specific volume capacitance, RuO in FIG. 6b2(x) @ MBC composite electrode surface RuO2Specific mass capacitance of (3), FIG. 6c RuO2(24.76) @ MBC composite electrode cycle stability.
As can be seen from FIG. 6a, when RuO is used2·H2RuO at an O loading of 5.66%2Maximum specific volume capacitance of (5.66) @ MBC of 44.97F/cm3. The capacitance gradually increases with the load amount, and RuO is performed when the load amount is 24.76%2The specific volume capacitance of (24.76) @ MBC reaches 79.03F/cm3. FIG. 6b is based on load RuO2The calculated specific capacitance data is RuO when the load is 5.66% and the current density is 300-500 mA/g2The reported highest specific capacitance data of 1670F/g is shown to reach 76 percent of the theoretical capacitance of 2200F/g, which is the reportThe specific capacitance value closest to its theoretical value. As can be seen in FIG. 6c, RuO2(x) Good electrochemical stability of @ MBC composite electrode and RuO2(24.76) @ MBC maintained 97.1% of capacitance after 1000 charges and discharges.
Claims (10)
1. Biochar, characterized in that: the preparation method comprises the following steps:
A. preparing raw materials: cutting wood into wood blocks, and drying to obtain dried wood blocks;
B. pyrolysis: pyrolyzing the dried wood blocks under the protection of inert gas to obtain biochar; the pyrolysis is controlled in the following manner: in the pyrolysis process, when the temperature is lower than 200 ℃, the heating rate is not more than 60 ℃/h, then the mixture stays at the constant temperature of 200 +/-10 ℃ for 2-6 h, when the temperature is between 200 ℃ and 600 ℃, the heating rate is 15-30 ℃/h, and when the temperature is higher than 600 ℃, the heating rate is 20-40 ℃/h; after the temperature rises to 200 +/-10 ℃, keeping the pyrolysis temperature for 0.1-0.3 h at a constant temperature of 200 ℃ every time, and then continuously raising the temperature; the final temperature of the pyrolysis process is not lower than 800 ℃.
2. Biochar according to claim 1, characterized in that: in the step A, the drying temperature is 60-100 ℃.
3. Biochar, characterized in that: the preparation method comprises the following steps:
a. preparing raw materials: cutting wood into wood blocks, and drying to obtain dried wood blocks;
b. surface solvation pretreatment: preparing a mixed solution of sodium sulfite and sodium hydroxide, heating to boil, then placing the dried wood block into the mixed solution for cooking, and carrying out surface solvation pretreatment;
c. surface cleaning: washing the wood blocks subjected to surface solvent treatment to remove sodium hydroxide and sodium sulfite remained on the wood blocks;
d. densification: carrying out densification and extrusion treatment on the cleaned wood block, and then drying the extruded wood block;
e. pyrolysis: pyrolyzing the extruded and dried wood blocks under the protection of inert gas to obtain biochar; the pyrolysis is controlled in the following manner: in the pyrolysis process, when the temperature is lower than 200 ℃, the heating rate is not more than 60 ℃/h, then the mixture stays at the constant temperature of 200 +/-10 ℃ for 2-6 h, when the temperature is between 200 ℃ and 600 ℃, the heating rate is 15-30 ℃/h, and when the temperature is higher than 600 ℃, the heating rate is 20-40 ℃/h; after the temperature rises to 200 +/-10 ℃, keeping the pyrolysis temperature for 0.1-0.3 h at a constant temperature of 200 ℃ every time, and then continuously raising the temperature; the final temperature of the pyrolysis process is not lower than 800 ℃.
4. Biochar according to claim 3, characterized in that: in the step b, the total concentration of the mixed solution of sodium hydroxide and sodium sulfite is 2-4 mol/L, wherein the molar concentration ratio of sodium hydroxide to sodium sulfite is 8-5: 1.
5. biochar according to claim 3, characterized in that: in the step b, the time of surface solvation pretreatment is 2-8 h; preferably 4-6 h.
6. Biochar according to claim 3, characterized in that: and c, boiling and washing the wood blocks subjected to surface solvent treatment in boiled deionized water, wherein the time of single boiling and washing is not less than 10min, and the number of boiling and washing is not less than 6.
7. Biochar according to any one of claims 3 to 6, characterized in that: in the step d, during the densification extrusion treatment, the extrusion pressure is 3-8 MPa, and the extrusion time is 12-24 h; preferably, the extrusion pressure is 4-6 MPa.
8. The biochar monolithic electrode is characterized in that: polishing the biochar slice obtained in any one of claims 1 to 7 to prepare the biochar monolithic electrode.
9. The biochar monolithic electrode as claimed in claim 8, wherein: the thickness of the biochar single-chip electrode is not less than 600 mu m.
10. The biochar composite electrode is characterized in that: the biochar single chip of claim 8 or 9 is used as a carrier, and a transition metal oxide with electrochemical activity is loaded to obtain the single-chip biochar/metal oxide composite electrode.
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| CN112194114A (en) * | 2020-10-10 | 2021-01-08 | 中北大学 | Method for preparing three-dimensional pore channel structure by taking wood as raw material |
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| CN113257990A (en) * | 2021-04-23 | 2021-08-13 | 苏州攀特电陶科技股份有限公司 | Base metal inner electrode material for multilayer piezoelectric ceramic actuator and preparation method thereof |
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| CN115818639A (en) * | 2022-11-16 | 2023-03-21 | 珠江水利委员会珠江水利科学研究院 | Biomass phase carbon material, preparation thereof and application thereof in field of environmental remediation |
| CN115818639B (en) * | 2022-11-16 | 2023-08-04 | 珠江水利委员会珠江水利科学研究院 | Biomass phase carbon material, preparation thereof and application thereof in field of environmental remediation |
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