CN109802150B - Non-noble metal bifunctional oxygen electrode catalyst, preparation method thereof, zinc-air battery anode and zinc-air battery - Google Patents
Non-noble metal bifunctional oxygen electrode catalyst, preparation method thereof, zinc-air battery anode and zinc-air battery Download PDFInfo
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Abstract
The invention provides a non-noble metal bifunctional oxygen electrode catalyst which is characterized by being nano FeCo8S8A complex with reduced graphene oxide. The FeCo of the invention8S8The @ rGO catalyst has a synergistic effect between multi-element metals, and the catalytic intrinsic activity of the catalyst can be improved by regulating and controlling the electronic structure of the metal, and simultaneously FeCo8S8The in-situ composite structure formed by the catalyst and the reduced graphene oxide can improve the conductivity and stability of the whole catalyst, and can show excellent performance in both electrocatalytic oxygen reduction and water oxidation in an alkaline solution. The zinc-air battery assembled based on the catalyst shows the charge-discharge potential difference and the stability which are comparable with those of a commercial noble metal (platinum carbon + ruthenium dioxide) combined catalyst. Therefore, the FeCo provided by the invention8S8The @ rGO catalyst has the advantages of low cost and good performance, and can be used as a high-efficiency oxygen electrode material to be applied to a zinc-air battery.
Description
Technical Field
The invention belongs to the technical field of electrocatalyst synthesis technology and energy conversion devices, and particularly relates to a non-noble metal bifunctional oxygen electrode catalyst and a preparation method thereof.
Background
The high-efficiency conversion and utilization of clean energy has become a focus of global attention, and in recent years, a novel rechargeable metal-air battery, especially a zinc-air battery, is considered to be a novel energy conversion device with great development prospect due to the advantages of high theoretical capacity (1084Wh/kg), high cost performance, safety, no toxicity, environmental friendliness and the like. (Wang, Zhong-Li, et al, "Oxygen electrolytes in metal-air bases: from aqueous to non-aqueous electrolytes." Chemical Society reviews.43.22(2014):7746-7786.) however, the energy barrier for both Oxygen reduction (ORR) and water Oxidation (OER) reactions on the air electrode is very high, and the reaction energy barrier needs to be lowered by means of a highly efficient catalyst to promote the reaction. Therefore, if a high-efficiency non-noble metal bifunctional catalyst can be developed to be used as a substitute of a noble metal catalyst, the production and operation costs of the zinc-air battery can be greatly reduced.
Co9S8The compounds exhibit excellent ORR catalytic activity due to their unique electronic structure, but their OER catalytic performance is not ideal (Sidik R A, Anderson A B. Co9S8 as a catalyst for electrochemical reduction of O2: quaternary chemistry precursors [ J].The journal of physical chemistry b,2006,110(2):936-941.)。
Disclosure of Invention
In view of this, the technical problem to be solved by the present invention is to provide a non-noble metal bifunctional oxygen electrode catalyst, which has good ORR catalytic activity and good OER catalytic performance.
The invention provides a non-noble metal bifunctional oxygen electrode catalyst which is nano FeCo8S8A complex with reduced graphene oxide.
Preferably, the material is FeCo compounded on the surface of a substrate which is made of reduced graphene oxide8S8A nano flower ball formed by nano sheets.
Preferably, the diameter of the nano flower ball is 50-300 nm;
the reduced graphene oxide accounts for 20-60% of the non-noble metal bifunctional oxygen electrode catalyst in percentage by mass.
The invention also provides a preparation method of the non-noble metal bifunctional oxygen electrode catalyst, which comprises the following steps:
A) mixing a metal precursor, graphene oxide, a thiol compound, a surfactant and a high-boiling-point organic solvent by taking iron acetylacetonate and cobalt acetylacetonate as the metal precursor, heating to 220-260 ℃ under the condition of protective atmosphere, and reacting for 15-60 min to obtain a reaction product;
B) in the presence of NH3Annealing the reaction product in the Ar gas mixed gas, and cooling to obtain non-noble metal bifunctional oxygen electrode catalyst FeCo8S8@rGO。
Preferably, the thiol compound is selected from octanethiol;
the surfactant is selected from oleic acid;
the high-boiling-point organic solvent is selected from a mixed solvent of oleylamine and octadecene, and the volume ratio of oleylamine to octadecene is 1 (2-5);
the protective atmosphere conditions are selected from nitrogen;
the molar ratio of the iron acetylacetonate to the cobalt acetylacetonate is 1: 8;
the addition amount of the graphene oxide is 10-50 mg/mmol of metal precursor;
the addition amount of the high-boiling-point organic solvent is 20-50 mL/mmol of metal precursor;
the addition amount of the thiol compound is more than 0.25mL/mmol of the metal precursor;
the addition amount of the surfactant is 0.5-2 mL/mmol of the metal precursor.
Preferably, the temperature raising procedure in step a) is:
raising the temperature from room temperature to 120-150 ℃ within 10-30 min, keeping the temperature for 30-60 min, setting the temperature raising rate to be 5-10 ℃/min, reaching the reaction temperature of 220-260 ℃, and keeping the reaction time to be 15-60 min;
in the step B), the annealing heating rate is 2.5-10 ℃/min, the annealing temperature is 400-450 ℃, and the annealing time is 2-4 h;
said compound containing NH3NH in Ar gas mixture3The volume content of (A) is 5-15%.
The invention also provides a zinc-air battery anode which comprises the non-noble metal bifunctional oxygen electrode catalyst or the non-noble metal bifunctional oxygen electrode catalyst prepared by the preparation method.
Preferably, the catalyst comprises a catalyst layer, a foamed nickel support framework and an air diffusion layer which are sequentially compounded.
The invention also provides a zinc-air battery, which comprises an anode, a cathode, electrolyte and a battery shell, wherein the anode is the anode of the zinc-air battery.
Preferably, theThe battery shell is made of PMMA material, the negative electrode material is a polished zinc sheet, and the electrolyte is KOH and Zn (Ac)2The solution was mixed.
Compared with the prior art, the invention provides a non-noble metal bifunctional oxygen electrode catalyst which is characterized by being nano FeCo8S8A complex with reduced graphene oxide. The FeCo of the invention8S8The @ rGO catalyst has a synergistic effect between multi-element metals, and the catalytic intrinsic activity of the catalyst can be improved by regulating and controlling the electronic structure of the metal, and simultaneously FeCo8S8The in-situ composite structure formed by the catalyst and the reduced graphene oxide can improve the conductivity and stability of the whole catalyst, and can show excellent performance in both electrocatalytic oxygen reduction and water oxidation in an alkaline solution. The zinc-air battery assembled based on the catalyst shows the charge-discharge potential difference and the stability which are comparable with those of a commercial noble metal (platinum carbon + ruthenium dioxide) combined catalyst. Therefore, the FeCo provided by the invention8S8The @ rGO catalyst has the advantages of low cost and good performance, and can be used as a high-efficiency oxygen electrode material to be applied to a zinc-air battery.
Drawings
FIG. 1 is a scheme for synthesizing FeCo8S8A preparation scheme for @ rGO;
FIG. 2 is FeCo synthesized by an oil phase reaction one-pot method8S8Scanning electron micrographs of @ GO; the scale in the figure is 1 μm, and the resulting FeCo can be seen8S8Is a flower ball composed of nano-sheets, uniformly dispersed on the surface of the GO substrate;
FIG. 3 is a one-pot synthesis of Co by oil phase reaction9S8Scanning electron micrographs of @ GO; the scale in the figure is 1 μm, and the resulting Co can be seen9S8Also is a flower ball composed of nano-sheets, and is uniformly dispersed on the surface of the GO substrate;
FIG. 4 is FeCo synthesized by an oil phase reaction one-pot method8S8Transmission electron micrograph of @ GO; the scale in the figure is 500nm, the sheet structure with clear flower ball edge can be seen, which shows that the flower ball is composed of two-dimensional nano-sheets and is spread out in additionThe GO substrate of (2) can also be observed, and the flower balls are tightly combined with GO, which shows that FeCo8S8Growing in situ on the GO surface;
FIG. 5 is a one-pot synthesis of Co by oil phase reaction9S8Transmission electron micrograph of @ GO; the scale in the figure is 500nm, Co9S8Morphology of @ GO and FeCo8S8@ GO is very similar, the curd is composed of two-dimensional nanosheets, and the curd is tightly combined with GO;
FIG. 6 is FeCo synthesized by an oil phase reaction one-pot method8S8@ GO and Co9S8X-ray diffraction pattern of @ GO, the resulting product being separately associated with FeCo8S8Standard cards JCPDS #290484 and Co9S8The standard card JCPDS #190364, the two most intense peaks correspond to crystal planes (311) and (440);
FIG. 7 is FeCo synthesized by an oil phase reaction one-pot method8S8High resolution transmission electron micrograph of @ GO, lattice analysis of this region revealed FeCo8S8The exposed crystal face of @ GO is mainly the (311) crystal face, which corresponds to the result of XRD;
FIG. 8 is FeCo synthesized by an oil phase reaction one-pot method8S8@ GO and Co9S8@ GO; at 187, 464, 510 and 662cm-1Peak at FeCo8S8And Co9S8And characteristic peaks at 1349 and 1585cm-1The two strong peaks correspond to the characteristic D peak and G peak of GO respectively;
FIG. 9 shows FeCo obtained after annealing treatment8S8@ rGO and Co9S8@ rGO is in a 0.1mol/L KOH solution, and an LSV curve obtained by testing ORR performance by using a three-electrode system; in the figure, the abscissa is the standard hydrogen electrode voltage (V) and the ordinate is the current density (mA cm)-2) In the three curves, -. tangle-solidup-represents FeCo8S8Oxygen reduction LSV curve of @ rGO, - ● -oxygen reduction LSV curve representing commercial Pt/C (20% wt), - ■ -representing Co9S8The oxygen reduction LSV curve for @ rGO;
FIG. 10 shows FeCo obtained after annealing treatment8S8@ rGO and Co9S8@ rGO is tested in 0.1mol/L KOH solution by using a three-electrode system to obtain an LSV curve of OER performance; in the figure, the abscissa is the standard hydrogen electrode voltage (V) and the ordinate is the current density (mA cm)-2) In the three curves, -. tangle-solidup-represents FeCo8S8LSV curve for water oxidation reaction of @ rGO, - ● -stands for commercial RuO2LSV curve of water oxidation reaction of- ■ -represents Co9S8The LSV curve for water oxidation reaction of @ rGO;
FIG. 11 is FeCo obtained after annealing treatment8S8The @ rGO is used as an LSV curve for a zinc-air battery performance test of a positive electrode material of the zinc-air battery, and the comparison materials are Pt/C and RuO respectively2A mixture of (a); in the figure, the abscissa is the current density (mA cm)-2) The ordinate is the electrode voltage (V) taking zinc as reference, in the three curves, a-represents FeCo8S8@ rGO-charge-discharge LSV curve, -. diamond-solid-represents Pt/C charge-discharge LSV curve, - ● -represents Pt/C and RuO2The charge-discharge LSV curve of the mixture of (a);
FIG. 12 is FeCo obtained after annealing treatment8S8The curve of the charging and discharging cycle stability test of the zinc-air battery is carried out by adopting @ rGO as the anode material of the zinc-air battery, and the comparison materials are Pt/C and RuO respectively2A mixture of (a); the test current density is 10mA cm-2Charging for 400s, discharging for 400s is a cycle, the test is performed through 200 cycles, and arrows in the figure point to charge-discharge cycle curves of electrodes loaded with different materials;
fig. 13 is an entity diagram of the assembled zinc-air battery, which is tested by using a three-electrode system, wherein the working electrode is a positive electrode plate loaded with a catalyst, the reference electrode and the counter electrode are both zinc plates, and oxygen is generated during the charging process during the reaction, so that bubbles are generated on the electrodes and in the solution.
Detailed Description
The invention provides a non-noble metal bifunctional oxygen electrode catalyst which is nano FeCo8S8And reduction oxidationA composite of graphene.
The catalyst takes reduced graphene oxide as a substrate, and FeCo is compounded on the surface of the substrate8S8A nano flower ball formed by nano sheets. The diameter of the nanometer flower ball is 50-300 nm.
The mass percentage of the reduced graphene oxide in the non-noble metal bifunctional oxygen electrode catalyst is 20-60%, preferably 30-40%, and more preferably 35%.
The invention also provides a preparation method of the non-noble metal bifunctional oxygen electrode catalyst, which comprises the following steps:
A) mixing a metal precursor, graphene oxide, a thiol compound, a surfactant and a high-boiling-point organic solvent by taking iron acetylacetonate and cobalt acetylacetonate as the metal precursor, heating to 220-260 ℃ under the condition of protective atmosphere, and reacting for 15-60 min to obtain a reaction product;
B) in the presence of NH3Annealing the reaction product in the Ar gas mixed gas, and cooling to obtain non-noble metal bifunctional oxygen electrode catalyst FeCo8S8@rGO。
The invention takes ferric acetylacetonate and cobalt acetylacetonate as metal precursors, wherein the molar ratio of the ferric acetylacetonate to the cobalt acetylacetonate is 1: 8.
The graphene oxide is used as a substrate, and is prepared by an improved hummers method. The present invention is not particularly limited to the specific method for modifying the hummers method, and any method known to those skilled in the art may be used. The addition amount of the graphene oxide is 10-50 mg/mmol of the metal precursor, and preferably 20-40 mg/mmol of the metal precursor.
The invention takes a high-boiling-point organic solvent as a solvent, wherein the high-boiling-point organic solvent is selected from a mixed solvent of oleylamine and octadecene, the volume ratio of oleylamine to octadecene is 1 (2-5), and preferably 1 (3-4). The addition amount of the high-boiling-point organic solvent is 20-50 mL/mmol of the metal precursor, and preferably 30-40 mL/mmol of the metal precursor.
The thiol compound is selected from octyl mercaptan, and the addition amount of the thiol compound is more than 0.25mL/mmol of the metal precursor, preferably 1-2 mL/mmol of the metal precursor, and more preferably 1mL/mmol of the metal precursor.
The surfactant is selected from oleic acid; the shape and performance of the product can be controlled by the using amount of the surfactant, and in the invention, the adding amount of the surfactant is preferably 0.5-2 mL/mmol of the metal precursor, and is further preferably 1mL/mmol of the metal precursor.
The mixing order of the raw materials is not particularly limited, and the raw materials can be mixed according to the following method:
and (2) placing iron acetylacetonate and cobalt acetylacetonate into a reaction container, adding oleylamine dispersion liquid of graphene oxide, and then adding octadecene, a surfactant and a thiol compound.
Placing all the raw materials in a reaction container, heating to 220-260 ℃ under the condition of protective atmosphere, and reacting for 15-60 min to obtain a reaction product.
The temperature raising procedure comprises the following steps:
raising the temperature from room temperature to 120-150 ℃ within 10-30 min, keeping the temperature for 30-60 min, setting the temperature raising rate to be 5-10 ℃/min, reaching the reaction temperature of 220-260 ℃, and keeping the reaction time to be 15-60 min;
in the present invention, the room temperature is defined as 20 ± 10 ℃.
In some embodiments of the invention, the temperature raising procedure is:
heating the reaction system to 150 ℃ within 20min, keeping the temperature for 30min, then heating the reaction system to 260 ℃ at the heating rate of 10 ℃/min, and keeping the reaction for 30 min.
The heating and temperature-rising reaction is carried out under the condition that a magnetic stirrer is used for stirring, and the rotating speed of magnetons is 300-800 rpm.
The protective atmosphere conditions are selected from nitrogen.
And after the reaction is finished, naturally cooling to room temperature to obtain a reaction product.
And then, alternately washing and centrifuging the reaction product by using ethanol and n-hexane, and then drying at 40-100 ℃.
Specifically, after the reaction is finished, firstly, ultrasonically washing and centrifuging the product for 1-3 times by using an ethanol solution, then ultrasonically washing and centrifuging the product for 2-4 times by using normal hexane, and finally, drying the centrifuged product in a vacuum drying oven at 40-100 ℃ to obtain FeCo8S8@GO。
In the presence of NH3Annealing the reaction product in the Ar gas mixed gas, and cooling to obtain non-noble metal bifunctional oxygen electrode catalyst FeCo8S8@rGO。
Wherein the annealing heating rate is 2.5-10 ℃/min, the annealing temperature is 400-450 ℃, and the annealing time is 2-4 h;
said compound containing NH3NH in Ar gas mixture3The volume content of (A) is 5-15%.
Specifically, the gas introduced into the tube furnace is NH35-15% of Ar mixed gas, wherein the rate of the temperature rise process is 2.5-10 ℃/min, the temperature is raised to 400-450 ℃, then the temperature is kept for 2-4 h, and finally the FeCo is obtained by natural cooling8S8@rGO。
This step can remove solvents and surfactants from the surface of the product powder, convert it to a hydrophilic product, and reduce GO to some N-doped rGO, thereby increasing its conductivity.
Referring to FIG. 1, FIG. 1 is a diagram of the synthesis of FeCo8S8The preparation scheme of @ rGO.
The invention adopts improved oil phase reaction to successfully prepare GO in-situ compounded ternary FeCo by a simple one-pot method8S8Nanosheet, and then calcining in ammonia atmosphere to reduce GO to obtain FeCo8S8@ rGO catalyst. The invention is to provide Co with excellent ORR performance9S8For the starting point, a proper amount of Fe element is introduced, the electronic structures of two metals are optimized through the synergistic effect between multiple metals, the intrinsic activity of the catalyst is improved, and the catalyst has excellent OER and ORR dual-function catalytic performance. Meanwhile, GO is added as a substrate in the synthesis process, so that the products can be uniformUniformly dispersing on the surface of GO to avoid product agglomeration; another advantage is that GO becomes partially N-doped rGO after ammonia reduction, and due to its special two-dimensional structure and good electrical conductivity, the electronic conductivity of the composite in the reaction can be enhanced, thereby improving the performance of the catalyst. The result of applying the bifunctional catalyst to an actual zinc-air battery system shows that the catalyst has good stability and cyclicity in actual battery reaction and has the potential of commercial application.
The invention also provides a zinc-air battery anode which comprises a catalyst layer, a foam nickel support framework and an air diffusion layer which are sequentially compounded.
Wherein the air diffusion layer is prepared according to the following method:
mixing and dispersing acetylene black, carbon black and PTFE solution in ethanol, mixing and stirring, then removing ethanol, and rolling into a film with the thickness of 250-300 nm in a rolling machine.
The PTFE solution is a polytetrafluoroethylene solution with the mass concentration of 60 wt%, and the polytetrafluoroethylene solution is a polytetrafluoroethylene aqueous phase dispersion liquid containing a nonionic surface active stabilizer.
The mass ratio of the acetylene black to the carbon black to the PTFE solution is 1 (2-3) to (7-8).
The mixing and stirring time is 30-90 min.
The method for removing the ethanol is a method for removing the solvent, which is well known to a person skilled in the art, and in the invention, the method can be placed in an oven at 50-80 ℃ to remove the ethanol.
After the ethanol is removed, the mixture becomes a dough shape, and the dough is taken out and rolled to form a film.
The catalyst layer was prepared as follows:
mixing carbon black and FeCo8S8@ rGO is dispersed in ethanol, then PTFE solution is added, mixed and stirred, and then the ethanol is removed, and rolled to form a film.
Wherein the carbon black and FeCo8S8The mass ratio of the @ rGO to the PTFE solution is 1 (3-4) to (3-4).
Said FeCo8S8The @ rGO is the non-noble metal bifunctional oxygen electrode catalyst or the non-noble metal bifunctional oxygen electrode catalyst prepared by the preparation method.
The mixing and stirring time is 30-90 min.
The method for removing the ethanol is a method for removing the solvent, which is well known to a person skilled in the art, and in the invention, the method can be placed in an oven at 50-80 ℃ to remove the ethanol.
After the ethanol is removed, the mixture becomes a dough shape, the mixture is taken out to be rolled into a film, and the catalyst FeCo is ensured in the rolling film forming process8S8The load capacity of @ rGO is 2-5 mg/cm2。
After the steps are completed, the air diffusion layer and the catalyst layer are respectively attached to two sides of the foamed nickel with the thickness of 1.5mm, the foamed nickel becomes an electrode slice with the thickness of 0.4-0.5 mm after rolling, finally the electrode slice is placed in a muffle furnace, the electrode slice is solidified stably through heating treatment, the heating temperature is preferably 300-360 ℃, the heating time is 20-60 min, and the electrode slice is taken out after cooling to become the final electrode slice.
The invention also provides a zinc-air battery, which comprises a positive electrode, a negative electrode, electrolyte and a battery shell, wherein the positive electrode is the positive electrode of the zinc-air battery.
The specific type of the zinc-air battery is not particularly limited, and the zinc-air battery known to those skilled in the art can be used, and the invention is not limited to rechargeable or non-rechargeable zinc-air batteries.
The battery shell is made of PMMA materials, and consists of three parts: a lower layer, a middle layer and an upper layer. The size of PMMA plate is (5 ~ 7) cm (4 ~ 6) cm (1 ~ 2) cm, wherein cut out the same round hole of area in the middle of well and the top plate, and the area is 1~ 3cm2And a round hole with the diameter of 0.3-0.5 cm is reserved on the side surface of the middle layer plate and communicated with the large round hole in the center of the plate for injecting electrolyte.
The cathode material is a polished zinc sheet, and the electrolyte is KOH and Zn (Ac)2Preferably, the electrolyte is a mixture of KOH with a concentration of 4-6 mol/L and Zn (Ac) with a concentration of 0.2mol/L2The solution was mixed.
The structure of the zinc-air battery cell is not particularly limited in the present invention, and the zinc-air battery cell structure known to those skilled in the art may be used.
In the present invention, the assembly sequence of the zinc-air battery cell is as follows: the lower layer plate is polished, the silicone membrane with the round hole which is the same as the round hole in the middle layer plate in size is reserved on the polished zinc sheet, the thickness of the silicone membrane is 0.8mm, the silicone membrane with the round hole which is the same as the round hole in the middle layer plate in size is reserved on the middle layer plate, the thickness of the silicone membrane is 0.8mm, the anode electrode plate is arranged on the upper layer plate, and then the whole assembly is fixed by screws in four corners. The electrolyte is injected from the small hole on the side surface and is blocked by a rubber plug after bubbles are removed.
The FeCo of the invention8S8The @ rGO catalyst has a synergistic effect between multi-element metals, and the catalytic intrinsic activity of the catalyst can be improved by regulating and controlling the electronic structure of the metal, and simultaneously FeCo8S8The in-situ composite structure formed by the catalyst and the reduced graphene oxide can improve the conductivity and stability of the whole catalyst, and can show excellent performance in both electrocatalytic oxygen reduction and water oxidation in an alkaline solution. The zinc-air battery assembled based on the catalyst shows the charge-discharge potential difference and the stability which are comparable with those of a commercial noble metal (platinum carbon + ruthenium dioxide) combined catalyst. Therefore, the FeCo provided by the invention8S8The @ rGO catalyst has the advantages of low cost and good performance, and can be used as a high-efficiency oxygen electrode material to be applied to a zinc-air battery.
Unless otherwise specified, the starting materials and reagents used in the present invention are commercially available products.
In order to further understand the present invention, the following examples are provided to illustrate the non-noble metal bifunctional oxygen electrode catalyst and the preparation method thereof, as well as the positive electrode of the zinc-air battery and the zinc-air battery, and the protection scope of the present invention is not limited by the following examples.
Example 1 FeCo8S8Preparation of @ GO
In a clean 50mL three-necked round bottom flask, 0.0078g of iron acetylacetonate and 0.0458g of cobalt acetylacetonate were added, and then 5mg of freeze-dried GO was weighed into 1mL of oleylamineThe mixture was sonicated and charged to a flask, followed by 5mL octadecene, 0.2mL oleic acid and 0.2mL octanethiol. In N2Under protection, the reaction system is heated to 150 ℃ within 20min, kept for 30min, then heated to 260 ℃ at the heating rate of 10 ℃/min, kept for reaction for 30min, and then naturally cooled to room temperature. Taking out and centrifuging to obtain a black product, then ultrasonically washing and centrifuging for 2 times by using ethanol, ultrasonically washing and centrifuging for 2 times by using normal hexane, taking out a small amount of sample before centrifuging for the last time, dripping the sample on a clean copper sheet for scanning electron microscope shooting, dripping the sample on a 300-mesh copper net for transmission electron microscope shooting and high-resolution transmission electron microscope shooting, and finally placing the product obtained after centrifuging in a vacuum drying oven at 80 ℃ for 8 hours and then taking out. Referring to fig. 2 and 4, fig. 2 is FeCo synthesized by an oil phase reaction one-pot method8S8Scanning electron micrograph of @ GO. The scale in the figure is 1 μm. The resulting FeCo can be seen in the figure8S8Is a flower ball composed of nano-sheets, uniformly dispersed on the surface of the GO substrate. FIG. 4 is FeCo synthesized by an oil phase reaction one-pot method8S8Transmission electron microscopy of @ GO. The ruler in the figure is 500nm, the flaky structure with clear flower ball edges can be seen, the flower ball is composed of two-dimensional nanosheets, in addition, the spread GO substrate can also be observed, and the flower ball and GO are tightly combined together, so that FeCo is illustrated8S8In-situ growth on the GO surface.
Example 2 FeCo8S8@ GO in NH3Annealing step in/Ar atmosphere
The dried product in example 1 is put into a corundum porcelain boat and put into a tube furnace, NH is introduced3Heating the mixed gas/Ar (the volume percentage of ammonia gas in the mixed gas is 10 percent) to 400 ℃ at the speed of 5 ℃/min, keeping the temperature for 2h, and then naturally cooling. This step can remove solvents and surfactants from the surface of the product powder, convert it to a hydrophilic product, and reduce GO to some N-doped rGO, thereby increasing its conductivity.
Comparative example 1
In the above examples, to embody FeCo8S8@ rGO is in dual function, especially inOER performance relative to Co9S8The @ rGO is more advantageous, and the Co is synthesized by adopting the same method steps9S8The @ rGO complex was subjected to various characterizations and tests, except that in example 1, the metal precursors were all 0.0478g of cobalt acetylacetonate.
Obtained Co9S8The @ GO complex was observed by scanning electron microscopy and transmission electron microscopy, and the results are shown in FIGS. 3 and 5. FIG. 3 is a one-pot synthesis of Co by oil phase reaction9S8Scanning electron micrograph of @ GO. The scale in the figure is 1 μm. The resulting Co can be seen in the figure9S8Also a flower ball composed of nanosheets, and is uniformly dispersed on the surface of the GO substrate. FIG. 5 is a one-pot synthesis of Co by oil phase reaction9S8Transmission electron microscopy of @ GO. The scale in the figure is 500nm, Co9S8Morphology of @ GO and FeCo8S8@ GO is very similar, the curd is composed of two-dimensional nanosheets, and the curd is tightly bound to GO.
The above Co was reacted as in example 29S8@ GO complex in NH3Annealing in/Ar atmosphere to obtain Co9S8@ rGO complex.
Example 3 FeCo8S8XRD and Raman characterization of @ rGO
The dried product of example 1 was taken out, ground with a mortar, and then a part was taken out for analysis and characterization, and its phase structure was analyzed with a sample level type high power X-ray diffractometer (Rigaku TTRIII), a diffraction peak appeared clearly, and compared with FeCo8S8Corresponds to standard card JCPDS # 290484, in which the three intensity peaks correspond to crystal planes (311), (440), and (222), respectively. It was characterized by Raman testing at 187, 464, 510 and 662cm-1Peak at FeCo8S8And characteristic peaks at 1349 and 1585cm-1The two strong peaks at (b) then correspond to the characteristic D and G peaks of GO, respectively. See figures 6, 7 and 8 for specific results.
Example 4 FeCo8S8Testing of electrocatalytic properties for @ rGO
FeCo product obtained by annealing in example 28S8@ rGO was used for electrocatalytic performance testing by weighing 3mg into a centrifuge tube, adding 1mg of conductive carbon black, followed by 0.5mL of a mixed solvent of water and isopropanol (V)Water (W)/VIsopropanol (I-propanol)3: 1) sonication for 20min formed a homogeneous mixture, followed by the addition of 10 μ L of nafion membrane solution (perfluorosulfonic acid-polytetrafluoroethylene copolymer solution), followed by sonication for 60min formed an ink-like black mixture. 10 μ L of the mixture was pipetted onto the glassy carbon electrode surface (loading 0.3 mg/cm)2) And after drying, placing the electrode in 0.1mol/L KOH solution, adopting a three-electrode system, taking a glassy carbon electrode as a working electrode, taking Ag/AgCl as a reference electrode, taking a platinum wire as a counter electrode, and testing the ORR and OER performances of the material by utilizing a rotary disc device and a CHI 760d electrochemical workstation. In the ORR test, the sweep rate was 5mV/s, the reverse sweep, and the voltage range was 0.2-1.0V (FIG. 9). In the OER test, the sweep rate was 5mV/s, the forward sweep, and the voltage range was 1.2-1.7V (FIG. 10). Pt/C and RuO2The slurry preparation process and test process methods of (a) are the same as described above. Co obtained in comparative example 19S8@ rGO was also tested according to the method described above. See fig. 9 and 10 for results.
EXAMPLE 5 preparation of Zinc air cell
For the air diffusion layer, 0.1g of acetylene black and 0.2g of carbon black are mixed and dispersed in ethanol, ultrasonic treatment is carried out for 10min, then 0.7g of PTFE solution (polytetrafluoroethylene solution) is added, the mixture is uniformly stirred for 60min, the mixture is placed in an oven at 80 ℃ after stirring to remove excessive ethanol until the mixture becomes a dough shape, then the mixture is taken out, and the mixture is rolled into a film with the thickness of 300nm in a rolling press. For the catalyst layer, 15mg of FeCo obtained after treatment in example 2 were added8S8Mixing and dispersing the @ rGO catalyst and 5mg of carbon black in ethanol, carrying out ultrasonic treatment for 10min, adding 15mg of PTFE solution, stirring for 60min, placing in an oven at 80 ℃ to remove excessive ethanol until the mixture becomes dough, taking out and rolling to form a film, and ensuring that the loading capacity of the catalyst is 5mg/cm2. After the operation is finished, the rolled air diffusion layer and the rolled catalyst layer are respectively attached to two sides of the foamed nickel, and then the rolled air diffusion layer and the rolled catalyst layer are rolled to form airThe gas diffusion layer and the catalyst layer completely covered the foamed nickel and pressed into the gaps of the foamed nickel skeleton, and the thickness after rolling was 0.4 mm. And finally, placing the electrode slice in a muffle furnace, heating the electrode slice in air at 320 ℃ for 20min, and taking out the electrode slice after cooling for later use. Finally, assembling the battery (figure 13), wherein the battery shell is made of PMMA material, the cathode is made of polished zinc sheets, the anode is the electrode prepared in the process, and the electrolyte is 6mol/L KOH and 0.2mol/L Zn (Ac)2The solution was mixed. The area of the battery case at one side of the positive electrode is 3cm2The circular hole is convenient for the anode to contact with air, so that oxygen participates in the reaction.
Similarly, corresponding commercial Pt/C and Pt/C + RuO loads2Zinc-air cells prepared with electrodes of the mixture were also prepared as described above, except that FeCo was used8S8Replacement of @ rGO catalyst with Pt/C or Pt/C + RuO of equal mass2Mixture (Pt/C + RuO)2Pt/C and RuO in mixture 250% of each mass fraction).
EXAMPLE 6 testing of Zinc air cell Performance
In the process of testing the battery, a three-electrode system is adopted, a working electrode is a positive electrode plate loaded with a catalyst, a reference electrode and a counter electrode are both zinc plates, and the test is carried out by utilizing a CHI 760d electrochemical workstation. For the charge and discharge LSV test, the sweep rate was 5mV/s, the forward sweep, and the voltage range was 0.6-2.2V (FIG. 11). From the analysis of the results, FeCo-supported8S8The overpotential ratio of the/rGO electrode battery is loaded with commercial Pt/C and loaded with Pt/C + RuO in the discharging stage2The electrode overpotential of the mixture is slightly larger, but in the charging phase, FeCo is loaded8S8the/rGO electrode has clear advantages. For the test of the stability of the charge-discharge cycle, the test current density is 10mA cm-2Charging 400s and discharging 400s are one cycle, and a cycle curve of 200 circles is obtained through testing. And (3) analysis results: at a current density of 10mA cm-2In the case of (2), corresponding to the load FeCo8S8PerGO, commercial Pt/C and Pt/C + RuO2The charge and discharge potential differences of the battery with the electrode of the mixture as the positive electrode were 0.86V, 0.95V and 0.75V, respectively. After 200 cycles, the battery performance is attenuatedLoaded with FeCo8S8The charge-discharge potential difference of the/rGO battery is 0.97V, commercial Pt/C is loaded, and Pt/C + RuO is loaded2The charge and discharge potential differences of the mixture are 1.58V and 0.90V respectively, so the corresponding potential difference increment values of the three are 0.11V, 0.63V and 0.15V, and the data show that the loaded FeCo8S8the/rGO battery has greater advantage in stability
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A preparation method of a non-noble metal bifunctional oxygen electrode catalyst is characterized by comprising the following steps:
A) mixing a metal precursor, graphene oxide, a thiol compound, a surfactant and a high-boiling-point organic solvent by taking iron acetylacetonate and cobalt acetylacetonate as the metal precursor, heating to 220-260 ℃ under the condition of protective atmosphere, and reacting for 15-60 min to obtain a reaction product;
B) in the presence of NH3Annealing the reaction product in the Ar gas mixed gas, and cooling to obtain non-noble metal bifunctional oxygen electrode catalyst FeCo8S8@rGO；
The non-noble metal bifunctional oxygen electrode catalyst is nano FeCo8S8A complex with reduced graphene oxide.
2. The preparation method of claim 1, wherein the non-noble metal bifunctional oxygen electrode catalyst is FeCo based on reduced graphene oxide and compounded on the surface of the substrate8S8A nano flower ball formed by nano sheets.
3. The preparation method according to claim 2, wherein the diameter of the nano flower ball is 50-300 nm;
the mass percentage of the reduced graphene oxide in the non-noble metal bifunctional oxygen electrode catalyst is 20-60%.
4. The method of claim 1, wherein the thiol-based compound is selected from the group consisting of octanethiol;
the surfactant is selected from oleic acid;
the high-boiling-point organic solvent is selected from a mixed solvent of oleylamine and octadecene, and the volume ratio of oleylamine to octadecene is 1 (2-5);
the protective atmosphere conditions are selected from nitrogen;
the molar ratio of the iron acetylacetonate to the cobalt acetylacetonate is 1: 8;
the addition amount of the graphene oxide is 10-50 mg/mmol of metal precursor;
the addition amount of the high-boiling-point organic solvent is 20-50 mL/mmol of metal precursor;
the addition amount of the thiol compound is more than 0.25mL/mmol of the metal precursor;
the addition amount of the surfactant is 0.5-2 mL/mmol of the metal precursor.
5. The method according to claim 1, wherein the procedure of raising the temperature in step a) is:
raising the temperature from room temperature to 120-150 ℃ within 10-30 min, keeping the temperature for 30-60 min, setting the temperature raising rate to be 5-10 ℃/min, reaching the reaction temperature of 220-260 ℃, and keeping the reaction time to be 15-60 min;
in the step B), the annealing heating rate is 2.5-10 ℃/min, the annealing temperature is 400-450 ℃, and the annealing time is 2-4 h;
said compound containing NH3NH in Ar gas mixture3The volume content of (A) is 5-15%.
6. A zinc-air battery positive electrode is characterized by comprising the non-noble metal bifunctional oxygen electrode catalyst prepared by the preparation method of any one of claims 1-5.
7. The positive electrode of claim 6, comprising a catalyst layer, a nickel foam support skeleton and an air diffusion layer, which are sequentially compounded.
8. A zinc-air battery, comprising a positive electrode, a negative electrode, an electrolyte and a battery case, wherein the positive electrode is the positive electrode of the zinc-air battery according to claim 6 or 7.
9. The zinc-air cell of claim 8, wherein the cell housing is made of PMMA, the negative electrode is made of polished zinc sheet, and the electrolyte is KOH and Zn (Ac)2The solution was mixed.
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