CN115347200B

CN115347200B - Conjugated microporous polymer catalyst and preparation method and application thereof

Info

Publication number: CN115347200B
Application number: CN202211283051.0A
Authority: CN
Inventors: 信静; 于源; 邢松松; 张龙
Original assignee: Shandong Dongyue Organic Silicon Material Co Ltd
Current assignee: Shandong Dongyue Organic Silicon Material Co Ltd
Priority date: 2022-10-20
Filing date: 2022-10-20
Publication date: 2022-12-23
Anticipated expiration: 2042-10-20
Also published as: CN115347200A

Abstract

The invention belongs to the technical field of electrode catalysts, and particularly relates to a conjugated microporous polymer catalyst and a preparation method and application thereof. The conjugated microporous polymer catalyst is obtained by taking hexa- (3,4-dicyanophenoxy) cyclotriphosphazene as a raw material, carrying out self-polymerization in the presence of ferric trichloride, and then carrying out high-temperature carbonization, and is marked as FeP-900. The FeP-900 prepared by the invention is used as an electrochemical catalyst, and has good ORR performance, long-term operation stability and methanol immunocompetence; the domestic zinc-air battery using FeP-900 as cathode catalyst has the features of high specific capacity, high energy density, strong cycle sustainability, etc. and its performance is superior to that of battery with 2 wt% Pt/C catalyst.

Description

Conjugated microporous polymer catalyst, and preparation method and application thereof

Technical Field

The invention belongs to the technical field of electrode catalysts, and particularly relates to a conjugated microporous polymer catalyst and a preparation method and application thereof.

Background

In recent years, environmentally friendly zinc-air batteries (ZABs) with ultra-high energy density have been considered as one of the best choices for new generation renewable energy storage and conversion devices. Despite the superior technical features of ZABs, their application still faces some major challenges, the most critical of which is the retarded kinetics of the Oxygen Reduction Reaction (ORR) occurring at the cathode during energy conversion, which determines the overall efficiency of ZABs. The most advanced catalyst at present is a noble metal Pt-based catalyst, and besides the high cost, the catalyst has the problems of resource scarcity, low stability, poor methanol tolerance and the like, so that the wide application of ZABs is hindered.

The development of low cost non-platinum ORR catalysts with sufficiently high activity and long-term stability has been the focus of research for many years. Over decades of continuous development, various non-noble metal catalysts have been developed, including transition metal oxides/phosphides/nitrides/oxynitrides/sulfides, transition metal alloys, metal-free catalysts, and carbonaceous materials doped with both transition metals and heteroatoms. These materials have in common the characteristic of having a very rough and porous structure, with the aim of maximizing the exposure of the active sites. However, how to finely modify the structure, porosity, conductivity and doping configuration of the catalyst to avoid serious self-aggregation of the metal-based particles is always the focus of research.

In order to solve these problems, it is necessary to study a new catalyst to achieve uniform dispersion and fine encapsulation of metal particles in a porous carbon matrix, ensuring maximum utilization of active sites.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: providing a conjugated microporous polymer catalyst which exhibits good ORR performance in both alkaline and neutral media, has good long-term operating stability and methanol immunity performance, better than 20wt% pt/C catalyst; the invention also provides a preparation method and application in electrochemistry, the catalyst is used as a cathode catalyst of a battery, the specific capacity and energy density of the battery are high, the cycle sustainability is long, and the content is better than that of the battery with the 2 wt% Pt/C catalyst.

The preparation method of the conjugated microporous polymer catalyst comprises the following steps:

(1) Preparation of 4-hydroxyphthalionitrile:

mixing potassium carbonate, sodium nitrite and dimethyl sulfoxide, adding 4-nitrophthalonitrile for reaction, pouring a product into a dilute hydrochloric acid solution after the reaction is finished, performing suction filtration, and sequentially washing and drying the obtained precipitate to obtain 4-hydroxyphthalionitrile;

(2) Preparation of hexa- (3,4) -cyano-phenoxycyclotriphosphazene:

mixing the 4-hydroxyphthalionitrile obtained in the step (1), phosphonitrile trimer chloride, sodium hydride and tetrahydrofuran for reaction, pouring a product into distilled water after the reaction is finished, filtering, and washing and drying the obtained precipitate in sequence to obtain hexa- (3,4) -cyano-phenoxy cyclotriphosphazene;

(3) Preparation of FeP-CMP:

stirring and mixing the hexa- (3,4) -cyano-phenoxy cyclotriphosphazene obtained in the step (2) and anhydrous ferric chloride under an inert gas atmosphere, heating to 90-110 ℃ for reaction for 15-20min, adding quinoline, continuously heating to 110-130 ℃ for reaction for 30-40min, then heating to 150-170 ℃ for continuous reflux reaction for 18-20h, then cooling and filtering, and sequentially washing, soxhlet extracting and drying the obtained precipitate to obtain FeP-CMP;

(4) Preparation of FeP-900:

and (4) heating the FeP-CMP obtained in the step (3) to 900 +/-5 ℃ in an inert gas atmosphere, and carbonizing for 2 to 2.5 hours to obtain a final product, namely the conjugated microporous polymer catalyst, which is recorded as FeP-900.

In the step (1), the molar ratio of the 4-nitrophthalonitrile to the potassium carbonate to the sodium nitrite is 1 (1.1 to 1.2) to 1.1 to 1.2; the mass-to-volume ratio of 4-nitrophthalonitrile to dimethyl sulfoxide (DMSO) is 1g (8~9) mL.

In the step (1), the reaction temperature is 24 to 30 ℃, and the reaction time is 24 to 30h.

In the step (1), the concentration of the dilute hydrochloric acid solution is preferably 0.1 to 0.2 mol/L.

In the step (1), preferably, distilled water is used for washing during washing; when drying, vacuum drying is preferred, and the drying temperature is 80 to 90 ℃, and the drying time is 24 to 36h.

In the step (2), the molar ratio of the phosphonitrile trichloride to the 4-hydroxyphthalic nitrile to the sodium hydride is 1 (6 to 6.5) to 6 (6 to 6.5); the mass volume ratio of the phosphonitrile trichloride to the Tetrahydrofuran (THF) is 1g (43 to 45) mL.

In the step (2), the reaction temperature is 24 to 30 ℃, and the reaction time is 4 to 6 hours.

In the step (2), water, isopropanol and acetone are adopted for washing in sequence during washing; when drying, vacuum drying is preferred, and the drying temperature is 60 to 80 ℃, and the drying time is 24 to 36h.

In the step (3) and the step (4), the inert gas is preferably nitrogen or argon.

In the step (3), the molar ratio of the hexa- (3,4) -cyano-phenoxy cyclotriphosphazene to the anhydrous ferric chloride is 1 (2 to 2.2); the mass-volume ratio of the hexa- (3,4) -cyano-phenoxy cyclotriphosphazene to the quinoline is 1g (7~8) mL.

In the step (3), ethanol, acetone, methanol, tetrahydrofuran and dichloromethane are sequentially adopted for washing during washing; in the Soxhlet extraction, tetrahydrofuran is used as an extracting agent, and the Soxhlet extraction time is 24 to 36h; when drying, vacuum drying is preferred, and the drying temperature is 100 to 110 ℃, and the drying time is 24 to 36h.

The conjugated microporous polymer catalyst is prepared by the preparation method.

The conjugated microporous polymer catalyst of the present invention is used in electrochemistry, preferably as a cathode catalyst of a battery.

Compared with the prior art, the invention has the following beneficial effects:

(1) According to the invention, hexa- (3,4-dicyanophenoxy) cyclotriphosphazene is used as a raw material, self-polymerization is carried out in the presence of ferric trichloride to form a porous phthalocyanine structure with metal, high-temperature carbonization is carried out to obtain a Fe, N and P co-doped carbon matrix and Fe-N-C and FeP nano particles (FeP-900), the preparation process is simple, and the cost is low;

(2) The prepared conjugated microporous polymer catalyst FeP-900 is a novel carbon-based catalyst codoped by transition metal (Fe) and heteroatom (N, P), has good ORR performance, and has good long-term operation stability and methanol immunocompetence in alkaline and neutral media; the domestic zinc-air battery using FeP-900 as cathode catalyst has the features of high specific capacity, high energy density, long cycle life, etc. and is superior to that of battery comprising 2 wt% Pt/C.

Drawings

FIG. 1 is an XRD characterization of FeP-900 prepared in example 1 of the present invention;

FIG. 2 is a Raman spectrum of FeP-900 prepared in example 1 of the present invention;

FIG. 3 is a 77k low temperature nitrogen absorption measurement of FeP-900 prepared in example 1 of the present invention;

FIG. 4 is an NLDFT pore size distribution curve of FeP-900 prepared in example 1 of the present invention;

FIG. 5 is an XPS measurement spectrum of FeP-900 prepared in example 1 of the present invention;

FIG. 6 is a 1s spectrum of high resolution C of FeP-900 prepared in example 1 of the present invention;

FIG. 7 is a 2p spectrum of Fe of FeP-900 prepared in example 1 of the present invention;

FIG. 8 is a 2P spectrum of P for FeP-900 prepared in example 1 of the present invention;

FIG. 9 is a 1s spectrum of N of FeP-900 prepared in example 1 of the present invention;

FIG. 10 is SEM and TEM images of FeP-900 prepared in example 1 of the present invention;

in fig. 10: a. SEM with scale bar of 2 μm; b. TEM with scale bar of 200 nm; c. TEM with scale bar of 100 nm; d. HR-TEM with scale bar 5 nm;

FIG. 11 is a Mapping chart of FeP-900 prepared in example 1 of the present invention;

in fig. 11: a. a transmission electron microscope image under a scale of 1 μm; b. the distribution of C element in FeP-900; c. the distribution of N element in FeP-900; d. the distribution of O element in FeP-900; e. the distribution of P element in FeP-900; f. the distribution of Fe element in FeP-900;

FIG. 12 is a graph at O ₂ In saturated solution, the scanning rate is 5 mV.s ⁻¹ LSV curves for the catalysts prepared in example 1 and comparative examples 1-3 at 1600 rpm;

FIG. 13 shows FeP-900 at O prepared in example 1 of the present invention ₂ In saturated solution, the scanning rate is 5 mV.s ⁻¹ LSV curves at different rotation speeds (rotation speeds from top to bottom increase in sequence);

FIG. 14 is a fitted line corresponding to FeP-900 prepared in example 1 of the present invention;

FIG. 15 is a graph of peroxide yield and electron transfer number at different potentials for catalysts prepared in example 1 and comparative examples 1-3;

FIG. 16 is a durability evaluation of FeP-900 prepared in example 1 of the present invention;

FIG. 17 is a comparison of the methanol tolerance test of 2 wt% Pt/C for FeP-900 prepared in example 1 of the present invention and comparative example 1;

wherein FIGS. 12-17 are representations of the electrochemical performance of the catalyst in KOH solutions of 0.1M concentration;

FIG. 18 shows FeP-900 prepared in example 1 of the present invention at a scan rate of 50 mV. Multidot.s ⁻¹ CV of time;

FIG. 19 is at O ₂ In saturated solution, the scanning rate is 5 mV.s ⁻¹ LSV curves for the catalysts prepared in example 1 and comparative examples 1-3 at 1600 rpm;

FIG. 20 is an LSV curve (sequentially increasing from top to bottom) of FeP-900 prepared in example 1 of the present invention at different rotation speeds of 400 to 2500rpm;

FIG. 21 is a graph of peroxide yield and electron transfer number at different potentials for catalysts prepared in example 1 and comparative examples 1-3;

FIG. 22 is a durability evaluation of FeP-900 prepared in example 1 of the present invention;

FIG. 23 is a methanol tolerance test comparing FeP-900 prepared in example 1 of the present invention with 20wt% Pt/C of comparative example 1;

wherein, FIGS. 19-23 are electrochemical performance characterization of the catalyst in PBS solution (phosphate balanced saline) at a concentration of 0.1M;

fig. 24 is a schematic view of an assembled zinc-air cell with a catalyst prepared in accordance with the present invention;

FIG. 25 is a polarization curve and a power density curve for FeP-900 prepared in example 1 of the present invention and 20wt% Pt/C of comparative example 1 as an air cathode zinc-air cell;

FIG. 26 shows the 10mA cm% of FeP-900 prepared in example 1 of the present invention and the 20wt% Pt/C assembled zinc-air cell of comparative example 1 ^-2 Specific capacity at current density;

FIG. 27 is a graph showing FeP-900 prepared in example 1 of the present invention and 20wt% Pt/C assembled zinc-air cell of comparative example 1 at 10mA · cm ^-2 Long-term stability test at current density;

FIG. 28 is the charge-discharge cycle performance of FeP-900 prepared in example 1 of the present invention and 20wt% Pt/C assembled zinc-air cell of comparative example 1.

Detailed Description

The present invention will be further described with reference to the following examples.

Example 1

The preparation method of the invention is adopted to prepare the FeP-900 catalyst:

(1) Preparation of 4-hydroxyphthalic nitrile:

adding potassium carbonate (2.63g, 19.063mmol), sodium nitrite (1.32g, 19.063mmol) and DMSO (24 mL) into a three-neck flask, mixing and dissolving, then adding 4-nitrophthalonitrile (3g, 17.33mmol), continuously stirring and reacting for 24 hours at 30 ℃, after the reaction is finished, pouring the product into 400mL (0.1 mol/L) of dilute hydrochloric acid solution, collecting precipitated gray solid by adopting a suction filtration method, washing with a large amount of distilled water, and then placing in a vacuum drying box at 80 ℃ for drying for 24 hours to obtain 4-hydroxyphthalic nitrile;

(2) Preparation of hexa- (3,4) -cyano-phenoxycyclotriphosphazene:

respectively adding triphosphazene chloride (2g, 5.75mmol), naH (0.83g, 34.5 mmol), THF (86 mL) and 4-hydroxyphthalionitrile (4.97g, 34.5 mmol) into a three-necked flask, mixing, continuously stirring at 30 ℃ for reacting for 4 hours, filtering and washing a product with water, isopropanol and acetone in sequence after the reaction is finished, and then drying in a vacuum drying box at 60 ℃ for 24 hours to obtain hexa- (3,4) -cyano-phenoxy cyclotriphosphazene;

(3) Preparation of FeP-CMP:

stirring and mixing hexa- (3,4) -cyano-phenoxy cyclotriphosphazene (0.99g, 1mmol) and anhydrous ferric chloride (0.34g, 2mmol) under an argon atmosphere, heating to 100 ℃ for reaction for 15min, adding quinoline (7 mL), continuously heating to 120 ℃ for reaction for 30min, then heating to 160 ℃ for continuous reflux reaction for 18h, then cooling and filtering, sequentially filtering and washing the obtained precipitate with ethanol, acetone, methanol, tetrahydrofuran and dichloromethane, then using tetrahydrofuran as an extractant for soxhlet extraction for 24h, and placing the obtained product in a 100 ℃ vacuum drying oven for drying for 24h to obtain FeP-CMP;

(4) Preparation of FeP-900:

heating FeP-CMP to 900 +/-5 ℃ in an argon atmosphere, and carbonizing for 2h to obtain the final product, namely the FeP-900 conjugated microporous polymer catalyst.

Physical characteristics of FeP-900 prepared in this example are shown in FIGS. 1-9. Wherein FIG. 1 is an XRD characterization of FeP-900; FIG. 2 is a Raman spectrum of FeP-900; FIG. 3 is a 77k low temperature nitrogen absorption measurement of FeP-900; FIG. 4 is an NLDFT pore size distribution curve for FeP-900; FIG. 5 is an XPS measurement spectrum of FeP-900; FIG. 6 is a 1s spectrum of high resolution C of FeP-900; FIG. 7 is a 2p spectrum of Fe of FeP-900; FIG. 8 is a 2P spectrum of P of FeP-900; FIG. 9 is a 1s spectrum of N of FeP-900.

As shown in fig. 1, significant diffraction peaks of FeP (JSPDS 71-2262) can be observed at 22.9, 30.8, 32.7, 34.5, 35.4, 37.1, 37.9, 45.5, 46.2, 46.9, 48.3, 50.3, 55.3, 56.1, 59.6, 74.5 and 79.1, which are (110), (020), (011), (200), (120), (111), (201), (121), (220), (211), (130), (310), (221), (002), (340) and (222), respectively.

FIG. 2 is a Raman spectrum of FeP-900 sample, which can detect distinct D band and G band at 1347cm respectively ^-1 And 1600cm ^-1 The d-band and g-band ratios (ID/IG) of FeP-900, calculated from the peak intensity as the center, were 0.846, respectively.

FIG. 3 shows the low temperature N of a sample of synthetic FeP-900 ₂ Adsorption-desorption isotherms, feP-900, show typical type IV isotherms at low nitrogen pressures (P/P0)<0.01 The adsorption capacity is increased sharply, and obvious hysteresis loops appear on the branches of the adsorption and desorption curves, which indicates that rich micropores and mesopores exist simultaneously; at the same time, in the high-pressure range (P/P0)>0.9 Fast adsorption growth occurs again, which indicates that macropores exist simultaneously, and the hierarchical pore structure of FeP-900 is further characterized based on a pore size distribution isotherm of non-local density functional theory (NLDFT) (figure 4), wherein the main peak takes 1.13nm as the center, and the broad peak is 1.48 to 3.96nm. The BET specific surface area of the FeP-900 is 959.2m ² ·g ^-1 Cumulative total pore volume of 0.722m ² ·g ^-1 And is beneficial to increasing the contact of reactants and active sites.

The overall surface composition and elemental electronic states of the FeP-900 sample, consisting primarily of C, fe, O, P and N elements, were obtained by X-ray photoelectron spectroscopy (XPS) of FIG. 5.

The 1s spectrum for C of FeP-900 in FIG. 6 consists of C-O (290.09 eV), C-N (286.33 eV), C-P (284.76 eV), and C = C/C-C (284.33 eV) peaks. It can be seen that both N and P elements successfully enter the porous carbon matrix, effectively changing the carbon structure and forming active sites favorable for ORR.

The 2p spectrum of high resolution Fe in FIG. 7 can be deconvoluted into 8 peaks distributed at 707.3eV, 711.31eV, 712.54eV, 715.39eV, 718.15eV, 722.49eV, 725.69eV and 728eV, respectively. The two peaks at 715.39eV and 725.69eV belong to Fe respectively ³⁺ 2p of _3/2 And 2p _1/2 Two peaks at 722.49eV and 712.54eV respectively belong to Fe ²⁺ 2p of _3/2 And 2p _1/2 Two peaks at 718.15eV and 728eV are assigned to satellite peaks, two peaks at 711.31eV and 707.3eV are associated with Fe-N and Fe-P, respectively.

The 2P region of P in FIG. 8 shows three peaks at 129.48 (P-Fe), 133.30 (P-C) and 134.14eV (P-O), respectively.

The high resolution XPS spectrum for 1s for N in FIG. 9, can detect distinct peaks at 402.17eV, 400.91eV, 400.46eV, 398.80eV, and 398.10eV, for N oxide, N graphite, pyridine N, fe-N, and pyridine N bond, respectively. Of these N, pyridine-N (17.31%), graphite-N (29.58%) and Fe-N (17.39%) are the common active sites for ORR. N, P codoping and the presence of both FeP and Fe-N atomic sites facilitate electrocatalysis.

SEM and TEM characterization of FeP-900 prepared in this example is shown in FIG. 10, where a is SEM at a scale of 2 μm, b is TEM at a scale of 200nm, c is TEM at a scale of 100nm, and d is HR-TEM at a scale of 5 nm.

As can be seen from fig. 10, the FeP-900 has a bulk of interpenetrated macropores, and it can also be found from the transmission result that the newly formed FeP nanoparticles are uniformly distributed on the carbon matrix. HR-TEM of FeP-900 in fig. d can detect a distinct lattice fringe with d-spacing of 0.199nm, corresponding to the (210) plane of FeP.

Mapping characterization of the FeP-900 prepared in the embodiment is shown in FIG. 11, wherein a is a transmission electron microscope image on a scale of 1 μm, b is a distribution of a C element in the FeP-900, C is a distribution of an N element in the FeP-900, d is a distribution of an O element in the FeP-900, e is a distribution of a P element in the FeP-900, and f is a distribution of an Fe element in the FeP-900.

As can be seen from fig. 11, the mapping of the FeP-900 element further confirms the uniform distribution of N on the porous carbon substrate, while the P and Fe elements are highly concentrated on the sites where the FeP nanoparticles appear. Meanwhile, fe signals belonging to isolated iron atoms dispersed on a carbon matrix can also be detected from Fe element mapping, and the result further reveals that atoms Fe-Nx and FeP are simultaneously introduced into the carbon skeleton.

Example 2

(1) Preparation of 4-hydroxyphthalionitrile:

adding potassium carbonate (2.75g, 19.93mmol), sodium nitrite (1.37g, 19.93mmol) and DMSO (27 mL) into a three-neck flask, mixing and dissolving, then adding 4-nitrophthalonitrile (3g, 17.33mmol), continuously stirring and reacting for 28h at 26 ℃, after the reaction is finished, pouring the product into 400mL (0.15 mol/L) of dilute hydrochloric acid solution, collecting precipitated gray solid by adopting a suction filtration method, washing with a large amount of distilled water, and then placing in a vacuum drying oven at 90 ℃ for drying for 36h to obtain 4-hydroxyphthalic nitrile;

(2) Preparation of hexa- (3,4) -cyano-phenoxycyclotriphosphazene:

respectively adding triphosphazene chloride (2g, 5.75mmol), naH (0.90g, 37.375mmol), THF (90 mL) and 4-hydroxyphthalionitrile (5.39g, 37.375mmol) into a three-neck flask, mixing, continuously stirring at 24 ℃ for reacting for 6 hours, filtering and washing a product with water, isopropanol and acetone in sequence after the reaction is finished, and then drying in a vacuum drying oven at 80 ℃ for 30 hours to obtain hexa- (3,4) -cyano-phenoxy cyclotriphosphazene;

(3) Preparation of FeP-CMP:

stirring and mixing hexa- (3,4) -cyano-phenoxy cyclotriphosphazene (0.99g, 1mmol) and anhydrous ferric chloride (0.36g, 2.1mmol) under the nitrogen atmosphere, heating to 110 ℃ for reacting for 18min, adding quinoline (7.5 mL), continuously heating to 130 ℃ for reacting for 35min, then heating to 170 ℃ for continuously refluxing for 19h, then cooling and filtering, sequentially filtering and washing the obtained precipitate with ethanol, acetone, methanol, tetrahydrofuran and dichloromethane, then performing Soxhlet extraction for 30h by using tetrahydrofuran as an extracting agent, and drying the obtained product in a 105 ℃ vacuum drying oven for 36h to obtain FeP-CMP;

(4) Preparation of FeP-900:

heating FeP-CMP to 900 +/-5 ℃ in an argon atmosphere, and carbonizing for 2.5h to obtain a final product, namely the FeP-900 conjugated microporous polymer catalyst.

Example 3

(1) Preparation of 4-hydroxyphthalionitrile:

adding potassium carbonate (2.87g, 20.79mmol), sodium nitrite (1.43g, 20.79mmol) and DMSO (26 mL) into a three-necked flask, mixing and dissolving, then adding 4-nitrophthalonitrile (3 g, 17.33mmol), continuously stirring at 24 ℃ for reaction for 30h, after the reaction is finished, pouring the product into 400mL (0.2 mol/L) of dilute hydrochloric acid solution, collecting precipitated gray solid by adopting a suction filtration method, washing with a large amount of distilled water, and then placing in a vacuum drying box at 85 ℃ for drying for 30h to obtain 4-hydroxyphthalic nitrile;

(2) Preparation of hexa- (3,4) -cyano-phenoxycyclotriphosphazene:

respectively adding triphosphazene chloride (2g, 5.75mmol), naH (0.86g, 35.65mmol), THF (88 mL) and 4-hydroxyphthalionitrile (5.14g, 35.65mmol) into a three-necked flask, mixing, continuously stirring for reaction at 26 ℃ for 5 hours, filtering and washing the product with water, isopropanol and acetone in sequence after the reaction is finished, and then drying in a vacuum drying oven at 70 ℃ for 36 hours to obtain hexa- (3,4) -cyano-phenoxycyclotriphosphazene;

(3) Preparation of FeP-CMP:

stirring and mixing hexa- (3,4) -cyano-phenoxy cyclotriphosphazene (0.99g, 1mmol) and anhydrous ferric chloride (0.38g, 2.2mmol) under the argon atmosphere, heating to 90 ℃ for reaction for 20min, adding quinoline (8 mL), continuously heating to 110 ℃ for reaction for 40min, then heating to 150 ℃ for continuous reflux reaction for 20h, then cooling and filtering, sequentially filtering and washing the obtained precipitate with ethanol, acetone, methanol, tetrahydrofuran and dichloromethane, then using tetrahydrofuran as an extracting agent for Soxhlet extraction for 36h, and drying the obtained product in a vacuum drying box at 110 ℃ for 30h to obtain FeP-CMP;

(4) Preparation of FeP-900:

heating FeP-CMP to 900 +/-5 ℃ in an argon atmosphere, and carbonizing for 2h to obtain the final product, namely the conjugated microporous polymer catalyst, which is noted as FeP-900.

Comparative example 1

Commercial 20wt% Pt/C catalyst.

Comparative example 2

This comparative example differs from example 1 only in that the carbonization temperature in step (4) is 800. + -. 5 ℃ and the conjugated microporous polymer catalyst obtained is designated FeP-800.

Comparative example 3

This comparative example differs from example 1 only in that the carbonization temperature in step (4) is 1000. + -. 5 ℃ and the conjugated microporous polymer catalyst obtained is designated FeP-1000.

The electrochemical performances of the FeP-900 catalyst and the catalysts of comparative examples 1-3 are examined below, taking example 1 as an example.

All electrochemical tests were performed using a conventional three-electrode system to measure the performance of ORR and OER at room temperature. The counter electrode was made of Pt plate, and the reference electrode was made of KCl saturated Ag/AgCl or SCE (saturated calomel electrode). Reversible Hydrogen Electrodes (RHE) according to Nernst equation (ereh = E) considering the potential correspondence of Ag/AgCl or SCE _Ag/AgCl +0.059×pH+0.197V；ERHE=E _Hg/HgO +0.059 × pH + 0.098V), the measured potential is converted to RHE.

The working electrode is a rotating disk electrode (RRDE) consisting of a glass carbon disk (RDE) with a diameter of 5.0mm or a glass carbon disk (Pt-ring) with a diameter of 3mm and an outer ring (Pt-ring) with an inner diameter of 5mm and an outer diameter of 7 mm. And ultrasonically oscillating 75 muL of deionized water, 375 muL of ethanol, 25 muL of 5wt% Nafion solution and 5mg of catalyst or 20wt% of industrial Pt/C suspension for 0.5h to form homogeneous catalyst ink, coating 8 muL of catalyst ink on the polished glassy carbon substrate serving as a working electrode, and naturally drying for 0.5h to obtain a uniform catalyst layer.

The catalytic activity of the catalyst on ORR was studied at CHI-760 electrochemical workstation using Cyclic Voltammetry (CV) and Rotating Disk Electrode (RDE). All tests were carried out under alkaline (0.1M KOH solution), neutral (0.1M PBS solution). Cyclic Voltammetry (CV) first at Ar ^- And O ₂ ^- Saturated potassium hydroxide solution (concentration 0.1M) 50 mV. S ^-1 Is carried out in (1). At O ₂ In saturated solution, with 5mV s ^-1 Linear Sweep Voltammetry (LSV) of (a) was used to measure the ORR polarization curve (400 to 2500rpm).

The electrochemical performance of the catalyst in 0.1M KOH was characterized as follows:

at O ₂ In saturated solution, the scanning rate is 5 mV.s ⁻¹ The LSV curves of the catalysts prepared in example 1 and comparative examples 1 to 3 at 1600rpm are shown in FIG. 12, and FeP-900 having the best catalytic activity and the initial potential Eonset of 1.03V (current density of 0.1 mA/cm) ^-2 ) Half-wave potential E _1/2 0.823V, comparable to commercial 20wt% Pt/C catalyst (Eonset =1.01V, E1/2= 0.821V), far exceeding the other control catalysts. Limiting Current Density of FeP-900 (5.51 mA cm) ^-2 ) Is also higher than FeP-800 (2.52 mA cm) ^-2 ) And FeP-1000 (2.74 mA. Cm) ^-2 ) Close to Pt/C (5.64 mA cm) ^-2 ). These results indicate that FeP-900 has a higher electrocatalytic activity on ORR in alkaline medium.

FeP-900 prepared in example 1 at O ₂ In saturated solution, the scanning rate is 5 mV.s ⁻¹ The LSV curves (sequentially increasing from top to bottom) at different rotation speeds are shown in fig. 13, and the increase of the rotation speed does not change the initial potential, but rather significantly increases the current density, indicating that the FeP-900 is a diffusion-controlled ORR process in alkaline media.

The fit line corresponding to the FeP-900 prepared in example 1 is shown in FIG. 14, the measured potentials of the FeP-900 at 0.2V to 0.6V are in a good linear relationship, and the calculated average value of n is 3.97, which indicates a one-step 4 e-based transfer process.

The peroxide yields and electron transfer numbers at different potentials for the catalysts prepared in example 1 and comparative examples 1-3 are shown in FIG. 15, at the measured potentials H ₂ O ₂ The yield was low (less than 4.86%), further validating the catalyst as to O ₂ High selectivity of reduction. While the RRDE measurement at 0.6V resulted in an electron transfer number of 3.97, further confirming the four electron oxygen reduction process.

Durability evaluation of FeP-900 prepared in example 1 As shown in FIG. 16, after running for 20000s at the measurement voltage, feP-900 still maintained 86.34% of its initial current value, above 20wt% of Pt/C56.97%.

As shown in FIG. 17, the FeP-900 prepared in example 1 was much less changed compared to the methanol tolerance test of comparative example 1, which was 20wt% Pt/C, by sharp fluctuation of Pt/C when methanol was injected for 400 s. This result indicates that FeP-900 has better immunological competence for methanol.

The electrochemical performance of the catalyst in 0.1M PBS solution is characterized as follows:

FeP-900 prepared in example 1 had a scan rate of 50 mV. Multidot.s ⁻¹ As shown in FIG. 18, the CV of FeP-900 was approximately a rectangular CV curve in saturated Ar solution and in saturated O ₂ A distinct reduction peak occurs in the electrolyte.

At O ₂ In saturated solution, the scanning rate is 5 mV.s ⁻¹ At 1600rpm, the LSV curves of the catalysts prepared in example 1 and comparative examples 1-3 are shown in FIG. 19, where E1/2 of FeP-900 reached 0.703V, exceeding Pt/C and FeP-800 and FeP-1000. The results show that FeP-900 still has higher electrocatalytic activity on ORR in a neutral medium.

LSV curves (sequentially increasing the rotation speed from top to bottom) of FeP-900 prepared in example 1 at different rotation speeds of 400 to 2500rpm are shown in FIG. 20, and the increase of the rotation speed does not change the initial potential but increases the current density under the neutral condition, which indicates that the FeP-900 is also a diffusion control ORR process in the neutral medium.

The yield of peroxide and the number of electron transfer of the catalysts prepared in example 1 and comparative examples 1-3 at different potentials are shown in FIG. 21, the yield of two-electron by-products is less than 2.1% at the measured potential of 0.2 to 0.7V, and the average number of electron transfer is about 3.96, which conforms to the four-electron oxygen reduction process.

Durability evaluation of FeP-900 prepared in example 1 As shown in FIG. 22, the FeP-900 also has much better operation durability in neutral electrolyte than commercial Pt/C, and can maintain 86.2% of its initial value of current after 20000s continuous cycling, which is higher than 70.5% of Pt/C, indicating that the durability of FeP-900 is very good.

Comparison of the methanol tolerance test of 20wt% Pt/C of example 1 with that of comparative example 1 As shown in FIG. 23, the current decay of FeP-900 after injection of a methanol solution having a concentration of 3.0M was also much smaller than that of commercial 20wt% Pt/C, confirming that FeP-900 also has good methanol tolerance capacity under neutral conditions.

The FeP-900 prepared in example 1 is used for preparing a zinc-air battery, a zinc plate is used as an anode, carbon paper loaded with a catalyst is used as an air cathode, KOH solution with the concentration of 6M is used as electrolyte, 5mg of the catalyst is dispersed into 375 mu L of ethanol and 125 mu L of Nafion solution (perfluorosulfonic acid type polymer solution) with the concentration of 5wt% to prepare catalyst ink, then ultrasonic dispersion is carried out for 0.5h, and the ink containing 1.5mg of the catalyst is loaded on the carbon paper to prepare the zinc-air battery. 2% by weight Pt/C of the industry of comparative example 1 as a reference air electrode, a discharge process curve was obtained by an electrochemical workstation of a two-electrode system (CHI-760E) at a current density of 10mA cm on a multi-channel cell test system (LAND CT 2001A) ^-2 In the case of (1), discharging is performed for 10min, charging is performed for 10min, and the discharging-charging performance of the battery is tested.

FIG. 24 is a schematic diagram of the FeP-900 assembled zinc-air cell prepared in example 1, in which the zinc plate is the anode, the FeP-900 supported carbon paper (1 cm. Times.1 cm) is the air cathode, and the electrolyte is KOH solution with a concentration of 6.0M.

FeP-900 prepared in example 1 and 20wt% Pt/C of comparative example 1 As polarization curves and power density curves of air cathode zinc-air cell are shown in FIG. 25, and the maximum discharge power density of the cell equipped with FeP-900Is 208mW cm ⁻² Preferably 20wt% of Pt/C (184 mW. Cm) ⁻² ）。

FeP-900 prepared in example 1 and 20wt% Pt/C of comparative example 1 assembled Zinc-air cell at 10 mA-cm ^-2 The specific capacity at current density is shown in FIG. 26, where the FeP-900 driven cell has a current density of 10mA cm ⁻² The specific capacity is about 801mAh gZn ⁻¹ Higher than the specific capacity of Pt/C catalysis (744 mAh gZn) ⁻¹ ) Close to the theoretical specific capacity of Zn (820 mAh. gZn) ^-1 ）。

FeP-900 prepared in example 1 and 20wt% Pt/C assembled Zinc-air cell of comparative example 1 at 10 mA-cm ^-2 Long term stability test at Current Density As shown in FIG. 27, the constant current discharge curve shows that the FeP-900-based cell can operate continuously for 97h, which is better than the 20wt% Pt/C-based cell (78 h), further confirming its excellent ORR stability.

The charge-discharge cycle performance of FeP-900 prepared in example 1 and that of 20wt% Pt/C assembled zinc-air cell of comparative example 1 are shown in FIG. 28, and it can be clearly seen that the charge-discharge voltage range of FeP-900 is much smaller compared to Pt/C, and the initial discharge and charge voltages are 1.0844V and 2.0046V, respectively, and the 20wt% Pt/C initial discharge and charge voltages are 1.2291V and 2.3791V, respectively. After 1000 long cycles, the discharging and charging voltages of FeP-900 became 1.0298V and 1.9859V, respectively, the discharging and charging voltages of 20wt% Pt/C became 1.0125V and 2.0186V, respectively. The results prove that FeP-900 has good activity and long-term operation stability and is suitable for practical application in ZABs.

Claims

1. A method for preparing a conjugated microporous polymer catalyst, comprising: the method comprises the following steps:

(1) Preparation of 4-hydroxyphthalionitrile:

(2) Preparation of hexa- (3,4) -cyano-phenoxycyclotriphosphazene:

(3) Preparation of FeP-CMP:

(4) Preparation of FeP-900:

and (4) heating the FeP-CMP obtained in the step (3) to 900 +/-5 ℃ in an inert gas atmosphere, and carbonizing for 2 to 2.5 hours to obtain a final product, namely the conjugated microporous polymer catalyst, which is marked as FeP-900.

2. The method of preparing a conjugated microporous polymer catalyst according to claim 1, wherein: in the step (1), the molar ratio of the 4-nitrophthalonitrile to the potassium carbonate to the sodium nitrite is 1 (1.1 to 1.2) to 1.1 to 1.2.

3. The method of preparing a conjugated microporous polymer catalyst according to claim 1, wherein: in the step (1), the mass-to-volume ratio of the 4-nitrophthalonitrile to the dimethyl sulfoxide is 1g (8~9) mL.

4. The method of preparing a conjugated microporous polymer catalyst according to claim 1, wherein: in the step (1), the reaction temperature is 24 to 30 ℃, and the reaction time is 24 to 30h.

5. The method of preparing a conjugated microporous polymer catalyst according to claim 1, wherein: in the step (2), the molar ratio of the phosphonitrile trichloride to the 4-hydroxyphthalic nitrile to the sodium hydride is 1 (6 to 6.5) to 6 (6 to 6.5);

the mass volume ratio of the phosphonitrile trichloride to the tetrahydrofuran is 1g (43 to 45) mL.

6. The method of preparing a conjugated microporous polymer catalyst according to claim 1, wherein: in the step (2), the reaction temperature is 24 to 30 ℃, and the reaction time is 4 to 6h.

7. The method of preparing a conjugated microporous polymer catalyst according to claim 1, wherein: in the step (3), the molar ratio of the hexa- (3,4) -cyano-phenoxycyclotriphosphazene to the anhydrous ferric chloride is 1 (2 to 2.2).

8. The method of preparing a conjugated microporous polymer catalyst according to claim 1, wherein: in the step (3), the mass-to-volume ratio of the hexa- (3,4) -cyano-phenoxy cyclotriphosphazene to the quinoline is 1g (7~8) mL.

9. A conjugated microporous polymer catalyst prepared by the method of any one of claims 1 to 8.

10. Use of the conjugated microporous polymer catalyst of claim 9, wherein: for use in electrochemistry.