Preparation method and application of multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst

Abstract

The present invention discloses a preparation method and application of a multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst. The metal salt species are introduced by an impregnation method, and high-temperature calcination is performed under a N2 protective atmosphere. The target catalyst is obtained after carbonization. A simple, fast and efficient molecular self-assembly coupled with a high-temperature calcination strategy is used to synthesize an N-doped graphene carbon layer-encapsulated FeNi alloy nanoparticle electrocatalyst with high activity, high stability and high selectivity. The catalyst has a stable structure and can effectively resist Cl in seawater. ‑ and complex components to erode active sites, thereby exhibiting excellent ORR / OER bifunctional catalytic performance and having great application prospects in rechargeable metal-air batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of nanofiber membranes, and in particular to a preparation method and application of a FeNi alloy armor catalyst encapsulated by multi-layer graphene carbon layers. Background Art

[0002] The ever-increasing demand for energy has brought about a series of serious environmental crises and challenges. As an efficient energy conversion and storage device, metal-air batteries are increasingly attracting attention from the international community. For metal-air batteries and water electrolysis, the use of seawater as an electrolyte will bring a variety of economic and social advantages, and reduce the competition for limited freshwater resources consumed by human activities. Like conventional metal-air batteries, the cathode of rechargeable seawater batteries also involves multi-electron reaction steps, and its performance is usually determined by the oxygen reaction on the cathode, where the oxygen reduction reaction (ORR) determines the discharge performance and the oxygen evolution reaction (OER) determines the charging performance. However, the following challenges are encountered during the operation of seawater batteries: (1) The composition of seawater is complex, including Mg 2+ , Ca 2+ , K + , SO4 2- ,HCO3 - etc., which will accelerate the corrosion of the catalyst and lead to poor stability of the catalyst; (2) There are a lot of Cl in seawater - , which can easily block the metal active sites and limit the adsorption of O2 molecules, Cl - Adsorption on the metal surface reduces the catalytic activity and reaction kinetics by interfering with the cleavage of the OO bond during the ORR process, which makes 4e - The reaction path changes to 2e - reaction; (2) Cl adsorbed on the active site - It's easy with OH - This creates a competitive adsorption mechanism, hindering the adsorption of oxygen-containing intermediates on active sites during the ORR / OER process, significantly reducing catalytic activity. Currently, commercially available precious metal-based electrocatalysts are resource-scarce, increasing their cost and exhibiting poor stability. Therefore, developing robust, stable, and efficient multifunctional catalysts is key to addressing this issue. Summary of the Invention

[0003] Based on previous research and existing problems, the present invention, after further research and analysis, proposes a preparation method and application of a multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing nitrogen-doped graphene carbon layer-coated FeNi alloy nanoparticle oxygen electrocatalyst, the method steps are as follows:

[0005] S1, preparation of rGO-PTCAPs-FeNi precursor;

[0006] S2, grinding the rGO-PTCAPs-FeNi precursor obtained in S1 and melamine in proportion until fully mixed, heating to 900 °C under inert gas protection and carbonizing for 3 h;

[0007] S3. The carbonized catalyst precursor is cooled to room temperature in the furnace to obtain the rGO-PTCAPs-FeNi-N catalyst.

[0008] Preferably, the specific method for preparing the rGO-PTCAPs-FeNi precursor in S1 includes:

[0009] S11, dissolving graphene oxide in deionized water at room temperature, and obtaining a uniformly dispersed graphene oxide solution by stirring, which is labeled as solution A;

[0010] S12, adding potassium perylenecarboxylate to solution A, stirring for 24 hours in the dark, to modify the edge position of graphene oxide;

[0011] S13. Under magnetic stirring, the FeCl3·6H2O aqueous solution and the NiCl2·6H2O aqueous solution are mixed with the suspension in step S12, and stirring is continued at room temperature. Finally, the target catalyst precursor is obtained by centrifugation, washing, and freeze-drying.

[0012] Preferably, in S2, the mixing ratio of the target catalyst precursor to melamine is 1:10.

[0013] Preferably, the heating rate is 2°C / min.

[0014] Preferably, the inert gas is one of nitrogen, argon or ammonia.

[0015] The present invention also provides a multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst, which is prepared by the above-mentioned method.

[0016] In addition, the present invention also proposes the application of the multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst prepared above, with the prepared catalyst as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode; the electrochemical performance test is carried out in a standard three-electrode system at room temperature, normal pressure and room temperature.

[0017] Compared with existing technologies, the present invention provides a preparation method and application of a multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst, which has the following beneficial effects:

[0018] (1) The present invention introduces metal salt species by impregnation, performs high-temperature calcination under N2 protective atmosphere, and obtains the target catalyst after carbonization. The preparation process is simple, green, environmentally friendly and pollution-free, and does not use rare precious metals, which greatly reduces production costs and can be produced in large quantities.

[0019] (2) The present invention controls the alloy size by adjusting the ratio of metal species introduced, and can achieve multi-dimensional regulation of the target catalyst by adjusting the calcination temperature, holding time and heteroatom doping ratio, which helps to accurately control the structure and performance of the catalyst.

[0020] (3) The present invention provides a simple, economical and efficient synthesis method to prepare N-doped carbon-supported transition metal-based electrocatalysts with excellent ORR / OER bifunctional electrocatalytic performance through molecular self-assembly coupled with high-temperature calcination strategy. The catalyst, thanks to its unique carbon coating structure, can effectively resist Cl in seawater. - Adsorption and corrosion of complex components on catalytic active sites are of great significance for promoting the development of clean energy conversion devices, such as rechargeable (seawater) metal-air batteries and hydrogen production by electrolysis of (sea) water. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 TEM image of the catalyst prepared in Example 1 of the present invention;

[0022] Figure 2 HRTEM images and selected area electron diffraction (SAED) patterns of the catalyst in Example 1 of the present invention, wherein ac are HRTEM images of the catalyst, and d is a SAED pattern;

[0023] Figure 3 : are X-ray diffraction patterns, Raman spectra, and X-ray photoelectron spectra of the catalysts in various embodiments of the present invention, wherein a is the X-ray diffraction pattern of each embodiment, b is the Raman spectra of each embodiment, and cf are the X-ray photoelectron spectra of each embodiment;

[0024] Figure 4 Ac in the figure are the LSV curves of ORR, Tafel slope and LSV curves of OER of the catalysts in alkaline seawater environment in each embodiment; df are the open circuit voltage diagram, specific capacity diagram and power density diagram of the zinc-air battery assembled with the catalyst of Example 1 and the Pt / C catalyst, respectively;

[0025] Figure 5 ac in the figure are the LSV curves, Tafel slopes and RRDE stability of the ORR of the catalysts in each embodiment in a (natural) seawater environment; df are the open circuit voltage diagram, specific capacity diagram and power density diagram of the seawater magnesium-air battery assembled with the catalyst of Example 1 and the Pt / C catalyst. DETAILED DESCRIPTION

[0026] The present invention provides a multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It should be noted in particular that all similar replacements and modifications are obvious to those skilled in the art and they all fall within the scope of protection of the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications of this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0027] Example 1

[0028] This embodiment discloses a preparation method of rGO-PTCAPs-FeNi-N catalyst, and the specific preparation method is as follows:

[0029] S1. Dissolve reduced graphene oxide in deionized water at room temperature, sonicate for 30 minutes, and stir for 30 minutes to obtain a uniformly dispersed reduced graphene oxide solution, which is labeled as solution A.

[0030] S2. Add potassium perylenecarboxylate to solution A and stir in the dark for 24 h to modify the edge position of graphene;

[0031] S3. Under magnetic stirring, 500 μl of a 5 mg / ml FeCl3·6H2O aqueous solution and a 500 μl NiCl2·6H2O aqueous solution were added to mix with the suspension in step S12, and stirring was continued at room temperature for 8 h. Finally, the target catalyst precursor was obtained by centrifugation, washing, and freeze-drying.

[0032] S4: Take 30 mg of the rGO-PTCAPs-FeNi precursor obtained in S3 and grind it with melamine in proportion until it is fully mixed. Heat it to 900 °C under inert gas protection and carbonize it for 3 h. The heating rate is set to 2 °C / min.

[0033] S5. The carbonized catalyst precursor is cooled to room temperature in the furnace to obtain the rGO-PTCAPs-FeNi-N catalyst.

[0034] Example 2

[0035] This embodiment discloses a method for preparing an rGO-PTCAPs-FeNi catalyst. The specific preparation method is as follows: S1, dissolving reduced graphene oxide in deionized water at room temperature, ultrasonicating for 30 minutes, and stirring for 30 minutes to obtain a uniformly dispersed reduced graphene oxide solution, which is labeled as solution A;

[0036] S2. Add potassium perylenecarboxylate to solution A and stir in the dark for 24 h to modify the edge position of the reduced graphene oxide;

[0037] S3. Under magnetic stirring, 500 μl of a 5 mg / ml FeCl3·6H2O aqueous solution and a 500 μl NiCl2·6H2O aqueous solution were added to mix with the suspension in step S12, and stirring was continued at room temperature for 8 h. Finally, the target catalyst precursor was obtained by centrifugation, washing, and freeze-drying.

[0038] S4. Take 30 mg of the rGO-PTCAPs-FeNi precursor obtained in S3, heat it to 900 °C under inert gas protection and carbonize it for 3 h. The heating rate is set to 2 °C / min.

[0039] S5. The carbonized catalyst precursor is cooled to room temperature in the furnace to obtain the rGO-PTCAPs-FeNi catalyst.

[0040] Example 3

[0041] This embodiment discloses a method for preparing rGO catalyst, and the specific preparation method is as follows:

[0042] S1. Take 30 mg of reduced graphene oxide (rGO) and place it in a magnetic boat. Heat it to 900 °C under inert gas protection for carbonization for 3 h. The heating rate is set to 2 °C / min.

[0043] S2. The carbonized catalyst precursor is cooled to room temperature in the furnace to obtain the rGO catalyst.

[0044] The present invention also performs performance analysis on the catalysts prepared in the above three embodiments, and the results are as follows: Figure 1-3 As shown:

[0045] (1) Figure 1 This is the TEM image of the rGO-PTCAPs-FeNi-N catalyst. It can be seen from the figure that the transition metal FeNi alloy nanoparticles are uniformly dispersed on the two-dimensional ultra-thin reduced graphene oxide nanosheets. This two-dimensional ultra-thin nanosheet structure has excellent conductivity and can accelerate electron transfer and mass transport in electrocatalytic reactions.

[0046] Figure 2 The ac in the figure is the HRTEM image of the rGO-PTCAPs-FeNi-N catalyst, and the d is the selected area electron diffraction image of the rGO-PTCAPs-FeNi-N catalyst. The morphology and structure of the alloy nanoparticles were analyzed by HRTEM and the edge of the alloy nanoparticles ( Figure 2ac in), it can be seen that the rGO-PTCAPs-FeNi-N electrocatalyst is obviously composed of FeNi alloy nanoparticles and graphite carbon. The alloy nanoparticles are evenly distributed on the graphite carbon matrix, and the FeNi alloy nanoparticles are surrounded by a thin graphene carbon layer. The calculated lattice spacing of 0.34 nm corresponds well to the (002) crystal plane of graphite carbon, proving that graphene oxide is successfully reduced to graphene. The lattice spacings of the two metal particles in the figure are 0.21 nm and 0.20 nm, respectively, corresponding to Fe 0.64 Ni 0.36 The (111) plane of the Fe phase is consistent with the (110) plane of the Fe phase, proving that we have successfully constructed an ideal structure of graphene carbon layer coated FeNi alloy nanoparticles. The bright spots in the selected area electron diffraction (SAED) correspond to the Fe 0.64 Ni 0.36 (111) surface and Fe (110) and (211) surfaces, which proves that the FeNi alloy nanoparticles formed on the reduced graphene oxide sheets are mainly Fe phase Fe 0.64 Ni 0.36 Exist in the form of phase.

[0047] Figure 3 a is the X-ray diffraction pattern of the three catalysts in Examples 1-3, b is the Raman spectrum of the three catalysts, and cf is the X-ray photoelectron spectrum of the three catalysts. The X-ray diffraction pattern (XRD) further clarifies the chemical composition and phase structure of the electrocatalyst. The Raman spectrum shows that the I D :I G The value is 0.84, which is higher than that of rGO-PTCAPs-FeNi(I D :I G =0.82) and rGO catalyst (I D :I G =0.78), indicating that it has more disordered carbon and the highest degree of defects; in addition, compared with the rGO catalyst, the peak of rGO-PTCAPs-FeNi showed a blue shift phenomenon. After the introduction of the N source, the peak of rGO-PTCAPs-FeNi-N showed a tendency to move to high energy, indicating that the introduction of FeNi alloy nanoparticles and N species can significantly change the electronic structure in the carbon matrix and accelerate electron transfer. The X-ray diffraction pattern shows that after the introduction of melamine, in-situ doping of the N element is achieved. Current studies have shown that pyridinic nitrogen and graphitic nitrogen are active species that catalyze ORR. Through analysis, it can be seen that the target catalyst has a higher content of pyridinic nitrogen and graphitic nitrogen, which will become strong evidence of high ORR catalytic activity. Compared with the high-resolution XPS Fe2p spectrum of the rGO-PTCAPs-FeNi catalyst, Fe 2+、Fe 3+ and Fe 0 The binding energy of rGO-PTCAPs-FeNi-N catalysts shifts significantly to a lower energy state, confirming that nitrogen-containing ligands usually anchor transition metals through special coordination and steric hindrance, thereby accelerating the electron transfer and material transport between the alloy and the carbon layer. The synergistic effect of alloy nanoparticles and N sites can effectively improve the ORR / OER catalytic performance of rGO-PTCAPs-FeNi-N catalysts.

[0048] The present invention adopts a three-electrode system to test its catalytic performance in O2-saturated 0.1M KOH seawater electrolyte and natural seawater (filtered) electrolyte. The electrochemical ORR performance of the three different catalysts in this embodiment was tested in a standard three-electrode system at room temperature and pressure, with 0.1M KOH alkaline seawater (pH=13) as the electrolyte, the prepared catalyst as the working electrode, the platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. The testing process was carried out on a Chenhua 660 system. The electrocatalytic behavior of the catalyst for OER was studied in a 1M KOH alkaline seawater solution (pH=14) environment, with the prepared catalyst as the working electrode, the carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The testing process was carried out on a Chenhua 760 system. To verify its application advantages, rGO-PTCAPs-FeNi-N catalyst was used as air cathode catalyst, zinc sheet as anode material, and 6M KOH solution prepared with seawater as electrolyte to assemble rGO-PTCAPs-FeNi-N based alkaline zinc-air batteries (ZABs). The actual application performance was tested. The results are as follows: Figure 4 As shown:

[0049] Figure 4 (a) shows that in 0.1 M KOH alkaline seawater solution, rGO-PTCAPs-FeNi-N has a higher positive onset potential (E onset =0.98V) and half-wave potential (E 1 / 2 =0.88V), which is much higher than that of commercial Pt / C catalyst (E onset =0.92V and E 1 / 2 =0.86V).

[0050] Figure 4 (b) shows that the Tafel slope of the rGO-PTCAPs-FeNi-N catalyst is 40.85 mV dec -1 , lower than rGO-PTCAPs-FeNi (85.98 mV / dec), rGO (43.8 mV / dec) and commercial Pt / C catalyst (55.2 mV / dec).

[0051] Figure 4 As shown in (c), in a 1 M KOH alkaline seawater solution, rGO-PTCAPs-FeNi-N only needs a low overpotential of 456 mV to achieve 100 mA / cm 2 The current density is better than that of rGO-PTCAPs-FeNi(E j＝100 =566mV) and commercial RuO2 catalyst (E j＝100 =477mV).

[0052] Figure 4 (d) The rGO-PTCAPs-FeNi-N-based alkaline seawater ZAB exhibits an open circuit voltage of 1.47 V.

[0053] Figure 4 (e) Using rGO-PTCAPs-FeNi-N based alkaline seawater ZAB at 10 mA cm -2 The specific capacity can reach 634.2 mAh g at a discharge current density of -1 , both higher than commercial Pt / C+RuO2-based alkaline seawater ZABs.

[0054] Figure 4 (f) The rGO-PTCAPs-FeNi-N-based alkaline seawater ZAB exhibited a power of 178.0 mW cm -2 peak power density.

[0055] In addition, the present invention also uses a three-electrode system to evaluate the ORR electrocatalytic performance of the catalyst in a natural seawater environment. Among metal-air batteries (zinc-air, aluminum-air batteries, etc.) with relatively low metal prices, magnesium-air batteries exhibit the best energy density. Therefore, the present invention also selected magnesium-air batteries as the research object. Thanks to the excellent ORR catalytic activity of the rGO-PTCAPs-FeNi-N catalyst in natural seawater, we used it as an air electrode catalyst, natural seawater (filtered) as the electrolyte, and magnesium plate as the anode to assemble a magnesium-seawater dissolved oxygen air battery with a structure similar to that of a zinc-air battery, and tested its actual application performance. The results are as follows Figure 5 As shown:

[0056] from Figure 5 From (a), it can be concluded that rGO-PTCAPs-FeNi-N exhibits a higher onset potential (E onset =0.77V) and half-wave potential (E 1 / 2 =0.63 V), and its ORR catalytic activity is superior to that of other comparative catalysts (rGO-PTCAPs-FeNi, rGO) and is even comparable to that of commercial Pt / C catalysts.

[0057] from Figure 5 From (b), it can be concluded that rGO-PTCAPs-FeNi-N has a lower Tafel slope (72.0 mV / dec), indicating that it has very superior reaction kinetics, further proving that the catalyst has excellent ORR catalytic performance in seawater environment.

[0058] from Figure 5 From (c) in the figure, it can be concluded that after a 20,000s chronoamperometric test, the current retention rate of rGO-PTCAPs-FeNi-N was 73.4%, which is much higher than that of rGO-PTCAPs-FeNi (62.6%) and commercial Pt / C (53.7%), proving that it still has excellent stability in natural seawater environment.

[0059] from Figure 5 From (d) in the figure, it can be concluded that the rGO-PTCAPs-FeNi-N-based seawater magnesium-air battery exhibits an open circuit voltage of 1.78V.

[0060] from Figure 5 (e) in the figure shows that the rGO-PTCAPs-FeNi-N-based seawater magnesium-air battery has a high performance of up to 1616.7 mAhg -1 Specific capacity.

[0061] from Figure 5 From (f) in the figure, it can be concluded that the rGO-PTCAPs-FeNi-N-based seawater magnesium-air battery has a high performance of up to 18.4 mW cm -2 power density.

[0062] The present invention can optimize the electronic arrangement of the carbon layer surface by coating the FeNi alloy nanoparticles with the N-doped carbon layer, expose more active sites, effectively accelerate electron transfer and material transport, and form a built-in electric field between the metal particles and the carbon layer due to the strong electronic coupling effect to repel Cl in seawater. - , reducing Cl - The erosion of the ORR active sites significantly improves the ORR catalytic performance. Furthermore, by effectively repelling the adsorption of Cl- at the active sites, the chlorine oxidation reaction (ClER) that competes with the OER is effectively reduced, thereby improving the OER catalytic activity. Therefore, the catalyst can exhibit excellent ORR / OER bifunctional catalytic activity in highly corrosive extreme seawater environments. These results provide new design criteria and a simple synthetic route for the further development of high-quality and stable cathode electrocatalysts for corrosive seawater electrolytes.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present invention.

Claims

1. A method for preparing a multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst, characterized in that: The steps are as follows: S1, preparation of rGO-PTCAPs-FeNi precursor; S11, dissolving graphene oxide in deionized water at room temperature, and obtaining a uniformly dispersed graphene oxide solution by stirring, which is labeled as solution A; S12, adding potassium perylene carboxylate to solution A, stirring for 24 h in the dark, to modify the edge position of graphene oxide; S13, under magnetic stirring, mixing the FeCl3·6H2O aqueous solution and the NiCl2·6H2O aqueous solution with the suspension in step S12, continuing stirring at room temperature, and finally obtaining the target catalyst precursor by centrifugation, washing, and freeze-drying; S2. The rGO-PTCAPs-FeNi precursor obtained in S1 was ground with melamine at a mass ratio of 1:10 until fully mixed. Under nitrogen protection, the temperature was raised to 900°C at a heating rate of 2°C / min for carbonization for 3 h. S3. The carbonized catalyst precursor is cooled to room temperature in the furnace to obtain the rGO-PTCAPs-FeNi-N catalyst.

2. A multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst, characterized in that: The preparation method according to claim 1 is used for preparation.

3. An application of the multi-layer graphene carbon layer encapsulated FeNi alloy armor catalyst as claimed in claim 2, characterized in that: The prepared catalyst was used as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode; the electrochemical performance was tested in a standard three-electrode system at room temperature, pressure, and room temperature.

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