Hollow spherical ruthenium-doped cobaltosic oxide catalyst material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of hydrolysis hydrogen production and flue gas zero-valent mercury removal, and provides a hollow spherical ruthenium-doped Co3O4 catalyst material as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing ruthenium salt, cobalt salt, alkali and a solvent for reaction to obtain a precursor product; and calcining the precursor product to obtain the hollow spherical ruthenium-doped Co3O4 catalyst material. The active sites of Co3O4 can be effectively adjusted by doping a trace amount of Ru, and the catalytic activity of the catalyst and the responsiveness to microwaves are improved, so that the NaBH4 hydrolysis hydrogen production rate and the zero-valent mercury removal efficiency are improved. The result of the embodiment shows that compared with the original Co3O4, the hollow spherical ruthenium-doped Co3O4 catalyst material prepared by the method has the advantages that the rate of hydrolyzing NaBH4 to produce hydrogen under the conditions of traditional heating and microwave heating is obviously improved, and the adsorption and oxidation removal efficiency of zero-valent mercury is also obviously improved.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis hydrogen production technology, and in particular to a hollow spherical ruthenium-doped cobalt tetroxide catalyst material, its preparation method, and its application. Background Technology

[0002] NaBH4 has a high hydrogen content, theoretically achieving a hydrogen storage density of 10.8 wt%, making it a highly efficient hydrogen storage material. NaBH4 hydrolysis for hydrogen production is considered a promising solution for future hydrogen energy applications, particularly in portable energy and transportation. However, the NaBH4 hydrolysis reaction proceeds slowly without a catalyst, making it difficult to meet the demanding hydrogen production rates in practical applications. Therefore, a catalyst is typically required to accelerate the reaction rate. Common catalysts include various metals and their oxides, such as platinum (Pt) and palladium (Pd).

[0003] Microwave enhancement is a technology that uses microwave energy to improve the rate and efficiency of chemical reactions. Applying microwave technology to NaBH4 water electrolysis for hydrogen production allows for direct heating of the reaction medium and catalyst, enabling the active sites of the catalyst to reach the optimal reaction temperature more quickly, thereby accelerating the reaction rate between NaBH4 and water. Compared to traditional heating methods, microwave heating offers advantages such as uniformity and speed, allowing for more effective control of reaction conditions, helping to optimize hydrogen yield and purity, and significantly shortening reaction time for efficient hydrogen production in a short period. Furthermore, microwave radiation can provide additional energy to activate active sites on the catalyst surface, enhancing catalytic performance and thus improving hydrogen production efficiency. From an energy efficiency perspective, microwaves act directly on the reactants and catalyst, reducing energy losses during transfer and significantly improving the system's energy utilization efficiency. In conclusion, microwave-enhanced NaBH4 water electrolysis for hydrogen production can achieve a synergistic improvement in reaction efficiency, hydrogen production performance, and energy utilization. In this process, selecting a catalyst with a high microwave response is crucial.

[0004] Currently, the catalysts used for NaBH4 water electrolysis to produce hydrogen are precious metals such as platinum and palladium, which are expensive. Although non-precious metal catalysts such as Co3O4 are inexpensive, they have problems such as insufficient catalytic activity and low water electrolysis hydrogen production rate. In addition, both types of catalysts have poor microwave responsiveness.

[0005] Furthermore, mercury, as a highly toxic, persistent, and bioaccumulative heavy metal pollutant, has made its emission control a key issue in global environmental governance. Zero-valent mercury (Hg) is a particularly important pollutant. 0Zero-valent mercury is one of the main forms of mercury found in industrial flue gas from coal-fired power plants, waste incineration plants, and steel smelters. It is characterized by high vapor pressure, extremely poor water solubility, and stable chemical properties, making it difficult for conventional flue gas purification equipment to capture directly. Currently, materials used to remove zero-valent mercury from flue gas mainly include modified activated carbon and metal oxide-based materials; however, these materials generally have low removal efficiency for zero-valent mercury, failing to meet the requirements for efficient mercury removal. Summary of the Invention

[0006] In view of this, the present invention provides a hollow spherical ruthenium-doped cobalt tetroxide catalyst material, its preparation method, and its application. The hollow spherical ruthenium-doped cobalt tetroxide catalyst material provided by the present invention exhibits high catalytic activity and good microwave responsiveness. It can significantly improve the rate of NaBH4 hydrolysis to hydrogen production under both conventional heating and microwave heating conditions, and also significantly improves the adsorption and oxidative removal efficiency of zero-valent mercury.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing hollow spherical ruthenium-doped Co3O4 catalyst material includes the following steps: Ruthenium salt, cobalt salt, base and solvent are mixed and reacted to obtain the precursor product; The precursor product was calcined to obtain the hollow spherical ruthenium-doped Co3O4 catalyst material; the chemical formula of the hollow spherical ruthenium-doped Co3O4 catalyst material is Ru. x Co 3-x O4, where x takes values ​​from 0.1 to 0.5.

[0008] Preferably, the ruthenium salt is ruthenium chloride; the cobalt salt is cobalt nitrate; and the solvent includes one or more of alcohols, N,N-dimethylformamide, and polyvinylpyrrolidone.

[0009] Preferably, the ratio of cobalt salt to solvent is 1 mmol: 10~20 mL.

[0010] Preferably, the alkali is sodium hydroxide, and the alkali is used in the form of an alkaline solution with a concentration of 0.5~2 mol / L; the volume ratio of the solvent to the alkaline solution is 3~10:1.

[0011] Preferably, the reaction temperature is 120~180℃, the heating rate is 5~25℃ / min, and the holding time is 2~24h.

[0012] Preferably, the calcination temperature is 300~900℃, the heating rate is 2~20℃ / min, the holding time is 2~8h, and the calcination atmosphere is nitrogen or air.

[0013] The present invention also provides a hollow spherical ruthenium-doped Co3O4 catalyst material prepared by the preparation method described above.

[0014] This invention also provides the application of the hollow spherical ruthenium-doped Co3O4 catalyst material described above in the production of hydrogen from liquid-phase chemical hydrogen storage materials.

[0015] Preferably, the liquid-phase chemical hydrogen storage material is a sodium borohydride; the hydrogen production of the liquid-phase chemical hydrogen storage material is carried out under microwave heating or ordinary heating conditions.

[0016] The present invention also provides the application of the hollow spherical ruthenium-doped Co3O4 catalyst material described above in the removal of zero-valent mercury.

[0017] This invention provides a method for preparing hollow spherical ruthenium-doped Co3O4 catalyst material, comprising the following steps: mixing ruthenium salt, cobalt salt, alkali, and solvent to react and obtain a precursor product; calcining the precursor product to obtain the hollow spherical ruthenium-doped Co3O4 catalyst material; the chemical formula of the hollow spherical ruthenium-doped Co3O4 catalyst material is Ru. x Co 3-x O4, where x ranges from 0.1 to 0.5. This invention effectively modulates the active sites of Co3O4 by doping with trace amounts of Ru, improving the catalyst's catalytic activity and microwave responsiveness, thereby increasing the hydrogen production rate from NaBH4 hydrolysis. Furthermore, this invention employs alkali-induced precursor aggregation into spheres, followed by core dissolution and shell redeposition under solvothermal conditions to form a hollow structure. Calcination and phase transformation then solidify and porous the cavity, ultimately yielding a ruthenium-doped Co3O4 catalyst material with a hollow spherical morphology. The hollow structure has a larger specific surface area, increasing the contact area between the catalyst and reactants, significantly improving the utilization rate of active sites, thereby accelerating the hydrolysis reaction rate and enhancing hydrogen production efficiency.

[0018] Furthermore, the catalyst material of this invention has a low Ru doping content, and Ru is cheaper than other noble metals (such as Pd and Pt), giving it a significant cost advantage. The results of the examples show that, compared with the original Co3O4, the hollow spherical ruthenium-doped Co3O4 catalyst material prepared in this invention significantly improves the rate of NaBH4 hydrolysis for hydrogen production under both conventional heating and microwave heating conditions.

[0019] In addition, the hollow spherical ruthenium-doped Co3O4 catalyst material prepared by this invention can also be used for the removal of zero-valent mercury. The hollow spherical ruthenium-doped Co3O4 catalyst material prepared by this invention has good adsorption and activation performance for zero-valent mercury and a high removal rate, and has good application prospects in the zero-valent mercury removal scheme. Attached Figure Description

[0020] Figure 1The XRD test results are for the hollow spherical ruthenium-doped Co3O4 catalyst materials prepared in Examples 1-3; Figure 2 The image shows an HRTEM image of the hollow spherical ruthenium-doped Co3O4 catalyst material prepared in Example 1, with the scale bar on the left being 5 nm and the scale bar on the right being 50 nm. Figure 3 SEM images of the hollow spherical ruthenium-doped Co3O4 catalyst materials prepared in Examples 2-4 and the hollow spherical Co3O4 prepared in Comparative Example 1; Figure 4 The diagram shows the apparatus for testing hydrogen production under microwave heating and conventional heating conditions, where (a) is microwave heating and (b) is conventional heating. Figure 5 The results are from the hydrogen production rate test. Figure 6 The results are the test results for the removal rate of zero-valent mercury. Detailed Implementation

[0021] This invention provides a method for preparing hollow spherical ruthenium-doped Co3O4 catalyst material, comprising the following steps: Ruthenium salt, cobalt salt, base and solvent are mixed and reacted to obtain the precursor product; The precursor product was calcined to obtain the hollow spherical ruthenium-doped Co3O4 catalyst material; the chemical formula of the hollow spherical ruthenium-doped Co3O4 catalyst material is Ru. x Co 3-x O4, where x takes values ​​from 0.1 to 0.5.

[0022] This invention involves reacting a mixture of ruthenium salt, cobalt salt, alkali, and solvent to obtain a precursor product. In this invention, the ruthenium salt is preferably ruthenium chloride; the cobalt salt is preferably cobalt nitrate, specifically cobalt nitrate hexahydrate (Co(NO3)2·6H2O); the amounts of the ruthenium salt and cobalt salt are preferably determined based on the value of x in the target product. In this invention, the solvent preferably includes one or more of alcohol, N,N-dimethylformamide and polyvinylpyrrolidone; the alcohol preferably includes one or more of methanol, ethanol, propanol, butanol, isopropanol and glycerol; in a specific embodiment of this invention, the solvent is a mixed solvent of isopropanol and glycerol, and the volume ratio of isopropanol to glycerol in the mixed solvent is preferably 4~6:1, specifically 5:1.

[0023] In this invention, the alkali is preferably a sodium hydroxide solution, and the alkali is preferably used in the form of an alkaline solution. The concentration of the alkaline solution is preferably 0.5~2 mol / L, specifically 1 mol / L. The solvent of the sodium hydroxide solution is water. The volume ratio of the solvent to the alkaline solution is 3~10:1, more preferably 5~6:1.

[0024] In a specific embodiment of the present invention, the mixing of the cobalt salt, ruthenium salt, alkaline solution and solvent is preferably carried out under ultrasonic conditions, and the ultrasonic time is preferably 10-20 min, specifically 15 min.

[0025] In this invention, the reaction temperature is preferably 120~180℃, specifically 120, 140, 160 or 180℃; the heating rate is preferably 5~25℃ / min, specifically 5, 10, 20 or 25℃ / min; and the holding time is preferably 2~24h, specifically 2, 4, 6, 12 or 24h. During the reaction, cobalt salt and ruthenium salt first undergo hydrolysis under alkaline conditions to generate corresponding metal hydroxide or basic salt precursors. These precursors further undergo nucleation, growth, and self-assembly under solvothermal conditions, gradually forming spherical aggregates composed of nanocrystals. As the reaction continues, components with smaller crystallites and unstable structures inside the spherical precursors dissolve and migrate to the outer layer, where they are redeposited and grown, causing the spherical precursors to gradually transform from a solid structure to a hollow structure. Simultaneously, ruthenium species are generated synergistically with cobalt-based precursors during the above process and doped into the precursor structure, thereby forming hollow spherical ruthenium-doped precursor products.

[0026] After the reaction is completed, the reaction solution is preferably cooled to room temperature naturally, and then filtered, washed and dried in sequence to obtain the precursor product; the washing is preferably done with anhydrous ethanol; the drying temperature is preferably 60°C, and the drying time is preferably 12~24h.

[0027] After obtaining the precursor product, the present invention calcines the precursor product to obtain the hollow spherical ruthenium-doped Co3O4 catalyst material. In the present invention, the calcination temperature is preferably 300~900℃, specifically 300, 500, 700 or 900℃, and the heating rate is preferably 2~20℃ / min, specifically 2, 5, 10 or 20℃ / min. The holding time is preferably 2~8h, specifically 2, 4, 6 or 8h, and the calcination atmosphere is preferably nitrogen or air; the calcination is preferably carried out in a tube furnace. During the calcination process, hydroxyl groups, nitrates and residual organic components in the precursor undergo thermal decomposition and are removed. The cobalt-based precursor further undergoes thermal decomposition and oxidation under heating conditions, gradually transforming into a cobalt tetroxide phase with a spinel structure. Simultaneously, ruthenium species undergo lattice rearrangement in synergy with cobalt oxides during calcination and enter the Co3O4 lattice as dopant, thereby forming the ruthenium-doped Co3O4 catalyst material. During the calcination process described above, the release of gas inside the precursor and the gradual crystallization of the shell help to preserve and stabilize the hollow structure, so that the resulting product maintains a hollow spherical morphology.

[0028] After calcination, the product is preferably cooled and removed to obtain hollow spherical ruthenium-doped Co3O4 catalyst material. In this invention, the chemical formula of the hollow spherical ruthenium-doped Co3O4 catalyst material is Ru. x Co 3-x O4, where x takes values ​​from 0.1 to 0.5, specifically 0.1, 0.2, 0.3, 0.4, or 0.5.

[0029] This invention also provides a hollow spherical ruthenium-doped Co3O4 catalyst material prepared by the preparation method described above; in this invention, the chemical formula of the hollow spherical ruthenium-doped Co3O4 catalyst material can be specifically Ru 0.1 Co 2.9 O4, Ru 0.2 Co 0.8 O4 or Ru 0.3 Co 2.7 O4, Ru 0.4 Co 2.6 O4 or Ru 0.5 Co 2.5 O4; the average particle size of the hollow spherical ruthenium-doped Co3O4 catalyst material is preferably 0.1~5 micrometers.

[0030] This invention also provides the application of the hollow spherical ruthenium-doped Co3O4 catalyst material described above in hydrogen production from liquid-phase chemical hydrogen storage materials. In this invention, the liquid-phase chemical hydrogen storage material is a sodium borohydride, specifically sodium borohydride; the hydrogen production from the liquid-phase chemical hydrogen storage material is carried out under microwave heating or ordinary heating conditions; the ordinary heating can specifically be water bath heating or oil bath heating; the preferred temperature for microwave heating or ordinary heating is 40°C.

[0031] This invention also provides the application of the hollow spherical ruthenium-doped Co3O4 catalyst material described above in the removal of zero-valent mercury. Specifically, this invention uses hollow spherical ruthenium-doped Co3O4 catalyst material to remove zero-valent mercury from flue gas.

[0032] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] Example 1 9 mmol (2.62 g) of Co(NO3)2·6H2O, 0.643 mmol (0.133 g) of RuCl3, 120 mL of isopropanol, 24 mL of glycerol, and 25 mL of NaOH solution (1 mol / L) were mixed and subjected to ultrasonic treatment for 15 min. The mixture was then transferred to the lining of a reactor and heated from 25 °C to 180 °C over 70 min, and maintained at 180 °C for 6 h. After the reaction was complete, the mixture was cooled to room temperature. The resulting reaction solution was filtered, and the solid product was washed twice with anhydrous ethanol and dried overnight at 60 °C to obtain 1.48 g of dried product. The product was placed in a tube furnace and calcined in air at a rate of 1 °C / min to 350 °C for 2 h. After calcination, the mixture was cooled to room temperature to obtain hollow spherical ruthenium-doped Co3O4 catalyst material with the chemical formula RuCl3. 0.2 Co 2.8 O4.

[0034] Example 2 Other conditions were the same as in Example 1, except that the amount of RuCl3 was changed to 0.31 mmol (0.064 g), resulting in hollow spherical ruthenium-doped Co3O4 catalyst material with the chemical formula Ru 0.1 Co 2.9 O4.

[0035] Example 3 Other conditions were the same as in Example 1, except that the amount of RuCl3 was changed to 1 mmol (0.207 g), resulting in hollow spherical ruthenium-doped Co3O4 catalyst material with the chemical formula Ru 0.3 Co 2.7 O4.

[0036] Example 4 Other conditions were the same as in Example 1, except that the amount of RuCl3 was changed to 1.385 mmol (0.287 g), resulting in hollow spherical ruthenium-doped Co3O4 catalyst material with the chemical formula Ru 0.4 Co 2.6 O4.

[0037] Comparative Example 1 The other conditions were the same as in Example 1, except that RuCl3 was not added, and hollow spherical Co3O4 was prepared.

[0038] Characterization and test results 1. Characterization Results XRD tests were performed on the hollow spherical ruthenium-doped Co3O4 catalyst materials prepared in Examples 1-3, and the results are as follows: Figure 1 As shown. According to Figure 1 It can be seen that the crystal form of Co3O4 doped with trace amounts of Ru still retains the crystal form of Co3O4.

[0039] The hollow spherical ruthenium-doped Co3O4 catalyst material (Ru) prepared in Example 1 was analyzed using high-resolution transmission electron microscopy (HRTEM). 0.2 Co 2.8 O4) was observed, and the results were as follows: Figure 2 As shown. Figure 2 The lattice fringes in the data show that Ru is indeed doped into the Co3O4 material. Meanwhile, according to... Figure 2 As can be seen in the right-hand figure, trace amounts of Ru are clearly and dispersedly incorporated into the surface or interior of Co3O4.

[0040] The hollow spherical ruthenium-doped Co3O4 catalyst materials prepared in Examples 2-4 and the hollow spherical Co3O4 prepared in Comparative Example 1 were observed using scanning electron microscopy. The results are as follows: Figure 3 As shown. According to Figure 3 It can be seen that the catalyst material prepared by this invention has a hollow spherical morphology.

[0041] 2. Hydrogen production performance test The experimental setup for microwave-enhanced catalytic reduction of NaBH4 to H2 is as follows: Figure 4As shown in (a). All experiments were conducted in a programmable microwave reactor (Shanghai Sino Microwave Chemical Technology Co., Ltd., UWave-2000), with microwave radiation operated on demand rather than continuously. This was to ensure that the required reaction temperature was maintained throughout the reaction process; a power of 400W was selected to guarantee sufficient heating capacity.

[0042] Temperature monitoring was performed using an infrared thermometer, which read temperature data from the side of the reactor surface. To ensure the accuracy of the infrared thermometer measurements, a pseudo-homogeneous solid-liquid reaction system was established, and continuous magnetic stirring was carried out at 600 rpm throughout the reaction process. Continuous stirring improves heat transfer, quickly eliminates the temperature gradient caused by localized hot spots induced by microwave heating, and ensures that the reaction system maintains an isothermal state.

[0043] Hydrogen production was assessed using the water displacement method. In the experiment, the catalyst was mixed with 90 mL of aqueous solution, followed by ultrasonic treatment for 15 minutes. The mixture was then transferred to a single-necked flask, placed in the center of a microwave oven cavity, and continuously stirred at 600 rpm using a magnetic stirrer. The system was then programmed to maintain a specific residence time at the desired temperature. When the catalyst-water mixture reached the desired temperature (40°C), 30 mL of a 0.6 wt% NaBH4 aqueous solution was added directly to the single-necked flask via a glass tube extending from the microwave oven cavity. Simultaneously, the NaBH4 inlet was quickly sealed with a sealing membrane to prevent any leakage, and mass recording began immediately after sealing the reactor. The amount of water displaced was recorded using electronic balance software at 30-second intervals. The hydrogen production rate at the specific temperature was determined using Equation (1-1).

[0044] HGR=V H2O / (t×m) Equation (1-1).

[0045] In the formula: V H2O - The volume of water accumulated, in milliliters (mL); m - the mass of the catalyst, in grams (g); t - the duration of the equilibrium reaction, in minutes (min).

[0046] In addition, the NaBH4 hydrolysis reaction was carried out under conventional heating (oil bath heating) (all other conditions were the same, except that microwave heating was replaced with oil bath heating at 40°C), using the following apparatus: Figure 4 As shown in (b), the hydrogen production rate was calculated.

[0047] Test results are as follows Figure 5 As shown. According to Figure 5It can be seen that, under both conventional heating and microwave heating conditions, compared with the original Co3O4 (i.e., the hollow spherical Co3O4 prepared in Comparative Example 1), the hollow spherical ruthenium-doped Co3O4 catalyst material prepared in this invention significantly improves the rate of hydrogen production from NaBH4 hydrolysis, and the improvement is even greater under microwave conditions. This indicates that Ru doping can effectively regulate the active sites of Co3O4, improve the catalytic activity of the catalyst and its responsiveness to microwaves.

[0048] 3. Zero-valent mercury removal capability test Zero-valent mercury can be directly measured using an online analyzer, conforming to the national standard method GB / T16659-2008. The removal efficiency of zero-valent mercury is calculated using formula (1-2). Hg 0 The steam initially flows through the bypass loop; once its concentration stabilizes, it is recorded as the inlet concentration Hg. in Subsequently, stable Hg 0 Steam is introduced into the reaction zone of the quartz tube reactor (the reaction zone is filled with Ru prepared in Example 1). 0.2 Co 2.8 O4 or the original Co3O4 prepared in Comparative Example 1), Hg at the outlet after the reaction 0 Concentration recorded as Hg out The expression for the removal efficiency η of zero-valent mercury is as follows: Equation (1-2).

[0049] Test results are as follows Figure 6 As shown. According to Figure 6 It can be seen that, compared with the original Co3O4 (i.e., the hollow spherical Co3O4 prepared in Comparative Example 1), the hollow spherical ruthenium-doped Co3O4 catalyst material prepared in this invention has a better effect on Hg. 0 The significant improvement in removal indicates that Ru doping can effectively regulate the active sites of Co3O4 and enhance the Hg content of the catalyst. 0 Adsorption and activation properties.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing hollow spherical ruthenium-doped Co3O4 catalyst material, characterized in that, Includes the following steps: Ruthenium salt, cobalt salt, base and solvent are mixed and reacted to obtain the precursor product; The precursor product was calcined to obtain the hollow spherical ruthenium-doped Co3O4 catalyst material. The hollow spherical ruthenium-doped Co3O4 catalyst material has the chemical formula Ru. x Co 3-x O4, where x takes values ​​from 0.1 to 0.

5.

2. The preparation method according to claim 1, characterized in that, The ruthenium salt is ruthenium chloride; the cobalt salt is cobalt nitrate; the solvent includes one or more of alcohols, N,N-dimethylformamide and polyvinylpyrrolidone.

3. The preparation method according to claim 1, characterized in that, The ratio of cobalt salt to solvent is 1 mmol: 10~20 mL.

4. The preparation method according to claim 1, characterized in that, The alkali is sodium hydroxide, and the alkali is used in the form of an alkaline solution with a concentration of 0.5~2 mol / L; the volume ratio of the solvent to the alkaline solution is 3~10:

1.

5. The preparation method according to claim 1, characterized in that, The reaction temperature is 120~180℃, the heating rate is 5~25℃ / min, and the holding time is 2~24h.

6. The preparation method according to claim 1, characterized in that, The calcination temperature is 300~900℃, the heating rate is 2~20℃ / min, the holding time is 2~8h, and the calcination atmosphere is nitrogen or air.

7. Hollow spherical ruthenium-doped Co3O4 catalyst material prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the hollow spherical ruthenium-doped Co3O4 catalyst material according to claim 7 in hydrogen production from liquid-phase chemical hydrogen storage materials.

9. The application according to claim 8, characterized in that, The liquid-phase chemical hydrogen storage material is a sodium borohydride; the hydrogen production of the liquid-phase chemical hydrogen storage material is carried out under microwave heating or ordinary heating conditions.

10. The application of the hollow spherical ruthenium-doped Co3O4 catalyst material according to claim 7 in the removal of zero-valent mercury.

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