Conjugated organic polymer electrocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a conjugated organic polymer electrocatalyst and a preparation method and application thereof, and belongs to the technical field of electrocatalytic materials.According to the catalyst, o-phenylenediamine modified by specific substituent groups and trialdehyde phloroglucinol serve as monomers, a Salphen porous organic polymer skeleton is generated in situ on a conductive carbon material Ketjen black through a low-temperature condensation reaction, and the Salphen porous organic polymer skeleton is obtained; and then coordinating with Co or Ni metal salt. The core of the invention lies in that the electronic structure of the metal active center is remotely regulated and controlled through the electronic effect of substituent groups, so that the oxygen reduction and oxygen evolution bifunctional catalytic activity of the catalyst is synchronously improved without depending on high-temperature pyrolysis conditions. The catalyst shows high power density, large specific capacity and long cycle life in a zinc-air battery, the bifunctional activity index (> 0.680-0.711 V) of the catalyst is comprehensively superior to that of a commercial Pt / C + IrO2 mixed catalyst, and the catalyst has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalytic materials, in particular to a conjugated organic polymer electrocatalyst and a preparation method and application thereof. BACKGROUND

[0002] Clean energy technologies such as fuel cells and metal-air batteries have attracted much attention due to their high energy density and zero emission characteristics. Among them, zinc-air batteries have high theoretical energy density and are considered as one of the most promising energy storage devices. However, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) occurring on the air cathode of the battery have slow kinetics and high overpotential, which seriously restricts the overall performance of the battery. Currently, commercial catalysts still rely on noble metal materials, but their high cost, scarce reserves in the earth's crust and poor durability hinder large-scale application.

[0003] In recent years, transition metal-nitrogen-carbon (M-N-C) materials, especially single-atom catalysts, have been considered as potential alternatives due to their high atomic utilization and considerable catalytic activity. However, the preparation of traditional M-N-C catalysts usually requires a high-temperature pyrolysis process, which can lead to disordered active site structures, uneven distribution, and difficulty in accurately controlling the coordination environment of metal centers, which is not conducive to in-depth understanding of the catalytic mechanism and rational design, and also has problems such as high energy consumption and poor repeatability.

[0004] Porous organic polymers (POPs) provide an ideal platform for constructing non-pyrolytic catalysts with well-defined structures due to their designable structure and tunable pore channels. Among them, Salphen (N,N'-bis salicylaldehyde o-phenylenediamine) ligand shows great potential due to its stable N2O2 tetradentate coordination cavity and expandable conjugated structure. However, how to precisely control the electronic structure of the metal active center in Salphen polymer without relying on pyrolysis to simultaneously improve its ORR and OER bifunctional catalytic activity and apply it to high-efficiency and stable zinc-air batteries is still a problem that needs to be solved at present. SUMMARY

[0005] The purpose of the present application is to provide a conjugated organic polymer electrocatalyst and a preparation method and application thereof to solve the above problems.

[0006] The present application provides a conjugated organic polymer electrocatalyst, and the reaction formula for obtaining the electrocatalyst is as follows: The electrocatalyst is obtained by condensation reaction of 3 or 4-substituted (R) o-phenylenediamine and triformylphloroglucin in a conductive carbon material solvent, to obtain a Salphen porous organic polymer skeleton, and then the obtained polymer skeleton is subjected to coordination reaction with a transition metal salt to obtain the electrocatalyst.

[0007] Preferably, the substituent R of the 3 or 4-substituted (R) o-phenylenediamine is selected from one of -F, -Cl, -Br, -CH3 or -OH.

[0008] A preparation method of the conjugated organic polymer electrocatalyst is provided, comprising the following steps: a) dispersing Ketjen black in an organic solvent to form a uniform dispersion; b) adding 3 or 4-substituted o-phenylenediamine and triformylphloroglucinol to the dispersion of step a) and mixing uniformly; c) performing a condensation reaction on the mixture of step b), and after the reaction is completed, separating, washing and drying to obtain a Salphen porous organic polymer skeleton; d) dispersing the intermediate obtained in step c) in an alcohol solvent, adding a transition metal salt, and performing a coordination reaction under heating and reflux conditions; e) after the reaction is completed, separating, washing and drying to obtain an electrocatalyst.

[0009] Preferably, in step c), the condensation reaction is a Schiff base condensation reaction, the reaction temperature is 120°C to 180°C, and the reaction time is 48 hours to 72 hours.

[0010] Preferably, the total mass ratio of the Ketjen black to the 3 or 4-substituted o-phenylenediamine and the triformylphloroglucinol is 1:1 to 3:1.

[0011] Preferably, in step d), the transition metal salt is an iron salt, a cobalt salt or a nickel salt.

[0012] Preferably, the molar ratio of the metal in the transition metal salt to the theoretical N2O2 coordination sites in the Salphen porous organic polymer skeleton is 0.5:1 to 2:1.

[0013] The application of the conjugated organic polymer electrocatalyst is provided, and the electrocatalyst is applied in electrocatalytic oxygen reduction reaction and electrocatalytic oxygen evolution reaction.

[0014] Preferably, the electrocatalyst is applied in a metal-air battery.

[0015] Preferably, the metal-air battery is a zinc-air battery, and the electrocatalyst is used as an air positive electrode catalyst of the zinc-air battery.

[0016] Therefore, the application adopts the above-mentioned conjugated organic polymer electrocatalyst, and a preparation method and application thereof. By rationally selecting the electronic properties of the substituent R on the phenyl ring of the o-phenylenediamine, the electronic cloud density of the N2O2 coordination cavity in the Salphen polymer skeleton formed finally is remotely controlled by using the inductive effect and conjugation effect. When the metal ions such as Fe 2+ , Co 2+ or Ni 2+ coordinate with the coordination cavity, the electronic effect of the substituent will be further transmitted to the metal center, and the d-electron orbital structure thereof is finely adjusted, so that the adsorption / desorption free energy of the ORR and OER reaction intermediates is optimized, and finally the catalytic activity and stability are significantly improved. This precise regulation strategy of functional group-ligand-metal center-catalytic performance realizes the effective enhancement of the intrinsic activity of the catalyst under non-pyrolysis conditions. The catalyst preparation process adopts a low-temperature condensation strategy, which avoids problems such as structural disorder, active site agglomeration and pore collapse caused by high-temperature pyrolysis, and the obtained catalyst has a clear structure, uniform active sites and good preparation repeatability. By rationally introducing substituents R with different electronic effects, the electronic state of the metal active center is remotely, directionally and accurately regulated, which provides a new paradigm for the rational design of high-performance catalysts. The prepared catalyst simultaneously exhibits ORR activity superior to or comparable to commercial Pt / C and OER activity close to IrO2 in alkaline medium, and the bifunctional activity index (ΔE) thereof is between 0.680 V and 0.711 V, which is significantly better than the ΔE = 0.730 V of the Pt / C+IrO2 mixed catalyst. The solid conjugated polymer skeleton and stable M-N2O2 coordination structure enable the catalyst to have excellent long-term running stability and methanol tolerance. The zinc-air battery based on the catalyst exhibits high power density, large specific capacity and long cycle life, and the performance is overall superior to the benchmark battery based on Pt / C+IrO2, which has great practical application value.

[0017] The technical solutions of the application will be further described in detail through examples. DETAILED DESCRIPTION

[0018] In order to better understand the above technical solutions, the above technical solutions will be described in detail by specific embodiments. Obviously, the described embodiments are only part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0019] The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the description of the application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0020] It is also to be noted that the terms "comprising", "comprise" and "comprised of" as used herein are synonymous with "including", "include" or "containing", "contain", and are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0021] The present application provides a conjugated organic polymer electrocatalyst, and a reaction formula for obtaining the electrocatalyst is as follows: The electrocatalyst is obtained by condensation reaction of 3 or 4-substituted (R) o-phenylenediamine and triformylphloroglucin in conductive carbon material kohlen black solvent to obtain a Salphen porous organic polymer skeleton, and coordination reaction of the obtained polymer skeleton with a transition metal salt to obtain the electrocatalyst.

[0022] Preferably, the substituent R of the 3 or 4-substituted (R) o-phenylenediamine is selected from one of -F, -Cl, -Br, -CH3 or -OH.

[0023] The present application provides a preparation method of the conjugated organic polymer electrocatalyst as described above, comprising the following steps: a) dispersing kohlen black in an organic solvent to form a uniform dispersion liquid; b) adding 3 or 4-substituted o-phenylenediamine and triformylphloroglucin to the dispersion liquid of step a) and mixing uniformly; c) condensation reaction of the mixture of step b), and after the reaction is completed, separation, washing and drying to obtain a Salphen porous organic polymer skeleton; d) dispersing the intermediate obtained in step c) in an alcohol solvent, adding a transition metal salt, and performing coordination reaction under heating reflux condition; e) after the reaction is completed, separation, washing and drying to obtain the electrocatalyst.

[0024] Preferably, in step c), the condensation reaction is Schiff base condensation reaction, the reaction temperature is 120°C to 180°C, and the reaction time is 48 hours to 72 hours.

[0025] Preferably, the total mass ratio of the Ketjen black to the 3 or 4-substituted o-phenylenediamine and triformylphloroglucinol is 1:1 to 3:1.

[0026] Preferably, the transition metal salt in step d) is an iron salt, a cobalt salt or a nickel salt.

[0027] Preferably, the molar ratio of the metal in the transition metal salt to the theoretical N2O2 coordination sites in the Salphen porous organic polymer skeleton is 0.5:1 to 2:1.

[0028] Provided is an application of the conjugated organic polymer electrocatalyst as described above in an electrocatalytic oxygen reduction reaction and an electrocatalytic oxygen evolution reaction.

[0029] Preferably, the electrocatalyst is applied in a metal-air battery.

[0030] Preferably, the metal-air battery is a zinc-air battery, and the electrocatalyst is used as an air positive electrode catalyst of the zinc-air battery.

[0031] In order to more clearly and specifically introduce the conjugated organic polymer electrocatalyst provided by the embodiments of the present application, the preparation method and the application thereof, the following will be described in combination with specific embodiments.

[0032] Example 1 The unsubstituted Salphen polymer catalyst is denoted as Co-Salphen / KB; Catalyst preparation: 150 mg KB was dispersed in a mixed solvent containing 20 mL N-methylpyrrolidone (NMP) and 10 mL mesitylene, and ultrasonicated for 30 minutes. Then 65 mg (0.6 mmol) of o-phenylenediamine and 84 mg (0.4 mmol) of triformylphloroglucinol (TPG) were added. After stirring for 30 minutes, 20 mg of p-toluenesulfonic acid (PTSA) was added as a catalyst. The mixture was transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, and reacted at 150°C for 72 hours. After the reaction was completed, it was cooled to room temperature, filtered, washed with NMP, THF and ethanol in sequence, and vacuum dried at 80°C overnight to obtain a Salphen / KB intermediate. 100 mg of the above intermediate was dispersed in 30 mL of ethanol, and an excess of Co(CH3COO)2 4H2O (about 50 mg) was added, and stirred at 80°C for 12 hours under reflux. After cooling, it was filtered, washed with ethanol until the filtrate was colorless, and vacuum dried at 80°C to obtain a Co-Salphen / KB catalyst.

[0033] Characterization and performance test: Structural characterization: XPS showed Co existed in +2 valence state, and there was a Co-N coordination peak in N 1s spectrum. XRD showed it was amorphous structure. BET test showed its specific surface area was ~580 m 2 / g.

[0034] Electrochemical performance: In 0.1 M KOH, ORR half-wave potential (E 1 / 2 ) was 0.860 V (vs. RHE). OER overpotential (η -2 ) at 10 mA cm 10 was 0.331 V. The bifunctional activity index ΔE was 0.711 V.

[0035] Example 2 4-F substituted Salphen polymer catalyst, denoted as Co-4F-Salphen / KB; The preparation method was the same as Example 1, except that o-phenylenediamine was replaced with equimolar 4-fluoro-o-phenylenediamine.

[0036] Characterization and performance: XPS showed that the Co 2p orbital binding energy was slightly positively shifted compared to Example 1, indicating that the electron-withdrawing F group reduced the electron cloud density of the metal center. ORR E 1 / 2 was increased to 0.865 V. OER η 10 was reduced to 0.325 V. ΔE was optimized to 0.690 V.

[0037] Example 3 4-Cl substituted Salphen polymer catalyst, denoted as Co-4Cl-Salphen / KB; The preparation method was the same as Example 1, except that o-phenylenediamine was replaced with equimolar 4-chloro-o-phenylenediamine.

[0038] Characterization and performance: The performance was similar to Co-4F-Salphen / KB, ORR E 1 / 2 was 0.863 V, OER η 10 was 0.327 V. ΔE was 0.694 V.

[0039] Example 4 3-F substituted Salphen polymer catalyst, denoted as Fe-3F-Salphen / KB; The preparation method was the same as Example 2, except that 4-fluoro-o-phenylenediamine was replaced with equimolar 3-fluoro-o-phenylenediamine, and metal salt Co(CH3COO)2 4H2O was replaced with equimolar Fe(CH3COO)2 4H2O.

[0040] Characterization and Performance: ORR E 1 / 2 0.861 V, OER η 10 0.329 V. ΔE is 0.698 V.

[0041] Example 5 4-CH3 substituted Salphen polymer catalyst, denoted as Co-4CH3-Salphen / KB; The preparation method is the same as Example 1, except that the o-phenylenediamine is replaced by equimolar 4-methyl-o-phenylenediamine.

[0042] Characterization and Performance: XPS shows that the Co 2p orbital binding energy is slightly negative compared to Example 1, indicating that the electron-donating CH3 group increases the electron cloud density of the metal center. ORR E 1 / 2 0.868 V. OER η 10 is significantly reduced to 0.322 V. ΔE is optimized to 0.684 V.

[0043] Example 6 4-OH substituted Salphen polymer catalyst, denoted as Co-4OH-Salphen / KB; The preparation method is the same as Example 1, except that the o-phenylenediamine is replaced by equimolar 4-hydroxy-o-phenylenediamine.

[0044] Characterization and Performance: The electron-donating effect and possible additional coordination make it exhibit the best OER performance. ORR E 1 / 2 0.870 V. OER η 10 is further reduced to 0.320 V. ΔE reaches the optimal 0.680 V.

[0045] Example 7 Ni-based catalyst, denoted as Ni-4F-Salphen / KB; The preparation method is the same as Example 2, except that the metal salt Co(CH3COO)2 4H2O is replaced by equimolar Ni(CH3COO)2 4H2O.

[0046] Characterization and Performance: This catalyst also exhibits good bifunctional activity, ORR E 1 / 2 0.858 V, OER η 10 0.332 V. ΔE is 0.704 V.

[0047] Example 8 Stability test of catalyst: accelerated durability test was performed on Example 6 (Co-4OH-Salphen / KB). After 5000 cycles of cyclic voltammetry scan in 0.1 M KOH, the half-wave potential of ORR only shifted negatively by 5 mV. The current retention was over 95% after chronoamperometry test for 10000 seconds. Meanwhile, no obvious fluctuation of current was observed when methanol was injected during ORR test, showing excellent methanol tolerance.

[0048] Example 9 Performance test of zinc-air battery: Example 6 (Co-4OH-Salphen / KB) was used as air cathode catalyst, zinc sheet as anode, and 6 M KOH + 0.2 M Zn(OAc)2 as electrolyte to assemble liquid zinc-air battery.

[0049] Performance data: the open circuit voltage of the battery was 1.48 V. The maximum power density reached 195 mW cm -2 At 10 mA cm -2 The specific capacity was 745 mAh g (Zn) -2 .

[0050] Example 10 Cycle test of rechargeable zinc-air battery: Example 6 (Co-4OH-Salphen / KB) was physically mixed with commercial IrO2 as air cathode catalyst to assemble rechargeable zinc-air battery.

[0051] Performance data: the open circuit voltage of the battery was 1.48 V. The maximum power density reached 195 mW cm -2 The specific capacity was 745 mAh g

[0052] Table 1 Comparison of electrochemical performance of catalysts (electrolyte: 0.1 M KOH)

[0053] Table 2 Comparison of zinc-air battery performance (catalyst: Co-4OH-Salphen / KB + IrO2)

[0054] As shown in Tables 1 and 2, the substituent-controlled catalysts prepared in this invention exhibit bifunctional activity indices ΔE within an excellent range of 0.680 V to 0.711 V. The ΔE values ​​of all catalysts from this invention are significantly lower than those of commercial Pt / C (>1.190 V), commercial IrO2 (>0.880 V), and the physically mixed Pt / C+IrO2 benchmark catalyst (0.730 V). In particular, the electron-donating group-modified Co-4OH-Salphen / KB (ΔE = 0.680 V) and Co-4CH3-Salphen / KB (ΔE = 0.684 V) demonstrate the best performance. Furthermore, the catalysts of this invention exhibit superior electrochemical stability and methanol tolerance. In actual zinc-air battery devices, their power density, specific capacity, and cycle life significantly exceed those of the comparative samples, fully demonstrating their enormous potential as high-performance, low-cost noble metal alternative catalysts.

[0055] Therefore, this invention employs the aforementioned conjugated organic polymer electrocatalyst, its preparation method, and its application. By rationally selecting the electronic properties of the substituent R on the o-phenylenediamine benzene ring, and utilizing its inductive and conjugating effects, the electron cloud density of the N2O2 coordination cavity in the ultimately formed Salphen polymer framework is remotely controlled. When Fe 2+ Co 2+ or Ni 2+ After the metal ion coordinates with the coordination cavity, the electronic effects of the substituent are further transferred to the metal center, finely regulating its d-electron orbital structure. This optimizes the adsorption / desorption free energy of the ORR and OER reaction intermediates, ultimately achieving a significant improvement in catalytic activity and stability. This precise control strategy of functional group-ligand-metal center-catalytic performance effectively enhances the intrinsic activity of the catalyst under non-pyrolysis conditions. The catalyst preparation process employs a low-temperature polycondensation strategy, avoiding problems such as structural disorder, active site aggregation, and pore collapse caused by high-temperature pyrolysis. The resulting catalyst has a well-defined structure, uniform active sites, and good reproducibility. By rationally introducing substituents R with different electronic effects, remote, directional, and precise control of the electronic state of the metal active center is achieved, providing a new paradigm for the rational design of high-performance catalysts. The prepared catalyst exhibits both superior ORR activity and near-IrO2 OER activity in alkaline media compared to commercial Pt / C catalysts. Its bifunctional activity index (ΔE) ranges from 0.680 V to 0.711 V, significantly better than the ΔE = 0.730 V of the Pt / C+IrO2 mixed catalyst. The robust conjugated polymer framework and stable M-N2O2 coordination structure endow the catalyst with excellent long-term operational stability and methanol tolerance. Zinc-air batteries based on this catalyst demonstrate high power density, large specific capacity, and long cycle life, comprehensively outperforming benchmark batteries based on Pt / C+IrO2, and possessing significant practical application value.

[0056] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced equivalently, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A conjugated organic polymer electrocatalyst, characterized in that, The reaction formula for the electrocatalyst is as follows: The electrocatalyst is obtained by condensing 3- or 4-substituted (R) o-phenylenediamine and trialdehyde phloroglucinol in a conductive carbon material Ketjen Black solvent to obtain a Salphen porous organic polymer framework. The obtained polymer framework is then coordinated with a transition metal salt to obtain the electrocatalyst.

2. The conjugated organic polymer electrocatalyst according to claim 1, characterized in that, The substituent R of the 3- or 4-substituted (R) o-phenylenediamine is selected from one of -F, -Cl, -Br, -CH3 or -OH.

3. A method for preparing a conjugated organic polymer electrocatalyst as described in any one of claims 1-2, characterized in that, Includes the following steps: a) Disperse Ketjenblack in an organic solvent to form a uniform dispersion; b) Add 3- or 4-substituted o-phenylenediamine and trialdehyde phloroglucinol to the dispersion from step a), and mix thoroughly; c) The mixture from step b) is subjected to a condensation reaction. After the reaction is complete, the mixture is separated, washed, and dried to obtain the Salphen porous organic polymer framework. d) Disperse the intermediate obtained in step c) in an alcohol solvent, add a transition metal salt, and carry out a coordination reaction under reflux conditions; e) After the reaction is complete, the catalyst is separated, washed, and dried to obtain the electrocatalyst.

4. The method for preparing a conjugated organic polymer electrocatalyst according to claim 3, characterized in that, In step c), the condensation reaction is a Schiff base condensation reaction, the reaction temperature is 120°C to 180°C, and the reaction time is 48 hours to 72 hours.

5. The method for preparing a conjugated organic polymer electrocatalyst according to claim 3, characterized in that, The total mass ratio of Ketjen black to the 3- or 4-substituted o-phenylenediamine and trialdehyde phloroglucinol is 1:1 to 3:

1.

6. The method for preparing a conjugated organic polymer electrocatalyst according to claim 3, characterized in that, The transition metal salt mentioned in step d) is an iron salt, a cobalt salt, or a nickel salt.

7. The method for preparing a conjugated organic polymer electrocatalyst according to claim 3, characterized in that, The molar ratio of the metal in the transition metal salt to the theoretical N2O2 coordination site in the Salphen porous organic polymer framework is 0.5:1 to 2:

1.

8. The application of a conjugated organic polymer electrocatalyst as described in any one of claims 1-2, characterized in that, The electrocatalyst is used in electrocatalytic oxygen reduction reaction and electrocatalytic oxygen evolution reaction.

9. The application of the conjugated organic polymer electrocatalyst according to claim 8, characterized in that, The electrocatalyst is used in metal-air batteries.

10. The application of the conjugated organic polymer electrocatalyst according to claim 9, characterized in that, The metal-air battery is a zinc-air battery, and the electrocatalyst is used as the air positive electrode catalyst of the zinc-air battery.

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