CN112259751B

CN112259751B - ORR and OER bifunctional catalyst, and preparation method and application thereof

Info

Publication number: CN112259751B
Application number: CN202011162962.9A
Authority: CN
Inventors: 施志聪; 李冠洲; 叶豪; 黄荣杰; 林冠鸿; 刘家沂
Original assignee: Guangdong University of Technology
Current assignee: Guangdong University of Technology
Priority date: 2020-10-27
Filing date: 2020-10-27
Publication date: 2022-06-14
Anticipated expiration: 2040-10-27
Also published as: CN112259751A

Abstract

The invention discloses a high-efficiency ORR and OER bifunctional catalyst, and a preparation method and application thereof. The preparation method comprises the following steps: s1, dissolving and mixing a nitrogen source and ferric salt, stirring, and drying to obtain a solid after stirring; s2, adding carbon black into the solid obtained in the step S1, grinding uniformly, and calcining at 850-1100 ℃ in a protective atmosphere to obtain powder; and S3, mixing the powder obtained in the step S2, nickel salt and a precipitator in deionized water, uniformly dispersing, carrying out hydrothermal reaction at 110-130 ℃ for 4-12 h, separating, drying, and calcining at 300-600 ℃ in a protective atmosphere to obtain the high-efficiency ORR and OER bifunctional catalyst. The prepared bifunctional catalyst ORR and OER has excellent performance and good stability, and the catalytic activity of the catalyst is improved by the synergistic effect of various active sites, so that the catalyst can be applied to the field of metal-air batteries.

Description

ORR and OER bifunctional catalyst, and preparation method and application thereof

Technical Field

The invention relates to the technical field of electrochemical non-noble metal catalysts, in particular to an ORR and OER bifunctional catalyst and a preparation method and application thereof.

Background

Rechargeable metal-air batteries are considered one of the most promising energy storage and conversion devices due to their low cost, abundant resources, and high energy density. The cathodic discharge process of metal-air batteries is driven by the Oxygen Reduction Reaction (ORR), while the charging process is driven by the Oxygen Evolution Reaction (OER). The ORR/OER performance of the catalyst determines whether the metal-air battery can be normally charged and discharged.

At present, bifunctional (ORR/OER) catalysts can be obtained by compounding different noble metals, such as Pt-based materials and Ru-based materials, and although the catalytic activity of the catalysts is excellent, the commercial development of rechargeable metal-air batteries is seriously affected due to the shortage of noble metal raw materials, high cost and poor durability; the other is carbon/transition metal oxide composite material, the raw material of the catalyst is rich in source and low in price, but the ORR/OER catalytic activity of the catalyst is still to be improved, and the requirement of commercial application is difficult to achieve. In response to this problem, there is an urgent need for the development of ORR and OER dual-function non-noble metal catalysts with low cost and high activity for such energy conversion storage devices.

Chinese patent (CN111313035A) also discloses a bifunctional non-noble metal catalyst, but potassium ferricyanide and dopamine are used as raw materials in the method, wherein potassium ferricyanide is easily decomposed by heating to generate hypertoxic hydrocyanic acid, and dopamine is expensive and is not beneficial to large-scale production.

Disclosure of Invention

The invention aims to provide a preparation method of an ORR and OER difunctional non-noble metal catalyst with low cost and high catalytic activity.

It is another object of the present invention to provide a non-noble metal catalyst that is ORR and OER dual function.

Another object of the present invention is to provide an application of the ORR and OER dual-function non-noble metal catalyst.

The purpose of the invention is realized by the following technical scheme;

a preparation method of an ORR and OER bifunctional catalyst comprises the following steps:

s1, dissolving and mixing a nitrogen source and ferric salt, stirring, and drying to obtain a solid after stirring;

s2, adding carbon black into the solid obtained in the step S1, grinding uniformly, and calcining at 850-1100 ℃ in a protective atmosphere to obtain powder;

s3, mixing the powder obtained in the step S2, nickel salt and a precipitator in deionized water, uniformly dispersing, carrying out hydrothermal reaction at 110-130 ℃ for 4-12 h, separating, drying, and calcining at 300-600 ℃ in a protective atmosphere to obtain the high-efficiency ORR and OER dual-function catalyst;

in the step S1, the molar ratio of the nitrogen source to the iron salt is (2-32): 1; in the step S2, the mass ratio of the solid to the carbon black is (5-20): 1; the mass ratio of the powder, the nickel salt and the precipitant in the step S3 is 1: 2: 3-8: 2: 0.3.

the invention utilizes the inactive Fe formed by iron-nitrogen co-doping carbon catalyst₃C as iron source, then nickel salt and precipitator, and Fe with OER performance through hydrothermal reaction and subsequent calcination₂O₃And compounding NiOOH and NiO on the iron-nitrogen co-doped carbon catalyst to obtain the catalyst with the dual functions of ORR and OER.

Preferably, the molar ratio of the nitrogen source to the iron salt in step S1 is (2-28): 1.

preferably, the mass ratio of the solid to the carbon black in S2 is (5-17): 1.

preferably, the mass ratio of the powder, the nickel salt and the precipitant described in S3 is 1: 2: 3-6: 2: 1.

preferably, the carbon black is one or more of ketjen black, acetylene black or conductive carbon black.

Preferably, the nitrogen source in S1 is one or more of melamine, dicyandiamide or urea; the ferric salt in S1 is one of ferric chloride, ferric nitrate and ferric acetate.

Preferably, the nickel salt in step S3 is at least one of nickel nitrate, nickel chloride or nickel acetate;

preferably, the precipitant is urea and/or ammonia water in step S3.

ORR and OER bifunctional catalysts obtainable by the preparation method described in any of the above.

The ORR and OER bifunctional catalyst prepared by the preparation method is applied to a metal air battery or a fuel battery.

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

firstly, the invention utilizes iron-nitrogen co-doped carbon catalyst as a substrate, and simultaneously forms low ORR active Fe on the surface of the substrate₃C is taken as an iron source, is subjected to hydrothermal reaction and calcination with nickel salt and a precipitator, and Fe with OER performance is formed on the surface of carbon₂O₃The preparation method of the compound of NiOOH and NiO is simple, and the raw materials do not contain toxic or expensive raw materials, thereby being beneficial to industrial production. The bifunctional catalyst prepared by the method has high catalytic activity, good OER activity stability and ORR activity stability.

Drawings

FIG. 1 is an XRD pattern of the catalysts prepared in comparative example 7, comparative example 8 and example 1;

FIG. 2 is an XPS spectrum of the catalyst prepared in example 1;

FIG. 3a shows Pt/C, FNC prepared in comparative example 7, FNC-0.4Ni prepared in example 1, and FNC-acid-0.4Ni prepared in comparative example 8 in O₂LSV profile in saturated 0.1M KOH, RuO in FIG. 3b₂FNC, FNC-0.4Ni and FNC-acid-0.4Ni in the presence of N₂LSV profile in saturated 1M KOH;

FIGS. 4a and b are FNC-0.4Ni and Pt/C in O, respectively, prepared in example 1₂LSV curves before and after 5000 CV cycles in saturated 0.1M KOH, FNC-0.4Ni and RuO in FIGS. 4c and d₂In N₂LSV profile before and after 1000 cycles CV in saturated 1M KOH;

FIG. 5 shows the reaction conditions of Pt/C and FNC-0.4Ni in O prepared in example 1₂I-t plot of 0.7V vs. rhe constant potential in saturated 0.1M KOH for 10 h.

Detailed Description

The invention is further illustrated by the following examples. These examples are intended to illustrate the invention and are not intended to limit the scope of the invention. Experimental procedures without specific conditions noted in the examples below, generally according to conditions conventional in the art or as suggested by the manufacturer; the raw materials, reagents and the like used are, unless otherwise specified, those commercially available from the conventional markets and the like.

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

The following examples and comparative examples were prepared by the following procedure, and the raw material ratios are shown in tables 1 and 2.

Example 1

S1, dissolving and mixing melamine and ferric chloride, stirring, and drying to obtain a solid after stirring;

s2, adding carbon black into the solid obtained in the step S1, grinding uniformly, and calcining at 900 ℃ at a heating rate of 5 ℃/min in an argon atmosphere;

s3, mixing the powder obtained in the step S2, nickel salt and a precipitator in deionized water, uniformly dispersing, carrying out hydrothermal reaction at 120 ℃ for 6 hours, carrying out suction filtration, cleaning and drying, and calcining at 400 ℃ in an argon atmosphere to obtain the high-efficiency ORR and OER dual-function catalyst which is named as FNC-0.4 Ni.

Examples 2 to 6

The raw materials and the preparation method are the same as example 1, and the proportion and content are shown in table 1.

TABLE 1

Example 7

The nitrogen source is urea, the iron source is ferric nitrate, the carbon source is conductive carbon black, the preparation method is the same as example 1, and the mixture ratio content is shown in table 2.

Examples 8 to 9

The raw materials and the preparation method are the same as example 1, and the proportion and content are shown in table 2.

TABLE 2

	Example 7	Example 8	Example 9	Example 10
					Molar ratio of nitrogen source to iron salt	28:1	2:1	20:1	20:1
Mass ratio of solid to carbon black	13:1	17:1	13:1	13:1
					Mass ratio of powder, nickel salt and precipitator	1:1:1	1:1:1	6:2:1	3:2:1

Comparative examples 1 to 6

The preparation method is the same as the embodiment, and the specific proportion is shown in table 3.

Comparative example 7

The preparation method and the proportion are the same as those of the embodiment 1, but the preparation is finished after the calcination at the high temperature of 900 ℃, the subsequent hydrothermal reaction and calcination steps are omitted, and the obtained powder is named FNC.

Comparative example 8

The preparation method and the proportion are the same as example 1, but after high-temperature calcination at 900 ℃, black powder obtained by grinding is soaked in 80mL of hydrochloric acid of 2mol/L, filtration and cleaning are carried out for multiple times after 8 hours, 0.4g of dried and ground powder, 0.4g of nickel nitrate hexahydrate and 0.4g of urea are weighed in 80mL of deionized water, after ultrasonic dispersion is carried out for 30 minutes, hydrothermal reaction is carried out for 6 hours at 120 ℃, the temperature rise speed is 1 ℃/min, the rotating speed is 10rpm, filtration, cleaning and drying are carried out after the reaction is finished, calcination is carried out for 3 hours at 400 ℃ under the argon atmosphere after grinding, the temperature rise speed is 1 ℃/min, and the obtained sample after cooling is named as FNC-acid-0.4 Ni.

TABLE 3

The catalysts prepared in the examples and comparative examples were characterized in the following manner:

as shown in fig. 1, XRD patterns of the catalysts prepared in comparative example 7, comparative example 8 and example 1. As can be seen from the figure, the carbon peaks of the 3 samples are all relatively low and wide, which indicates that the carbon material has certain defects, and the proper amount of defects is beneficial to the generation of catalytic active sites and the improvement of catalytic performance. Presence of Fe in XRD line of FNC₃Diffraction peak of C (PDF #85-1317), but Fe was not found in FNC-0.4Ni prepared after hydrothermal reaction and calcination₃Diffraction peak of C but increased high crystallinity of Fe₂O₃(PDF #39-1346) indicating Fe after hydrothermal reaction and calcination₃Conversion of C to Fe₂O₃. In addition, NiO and NiOOH were found on FNC-0.4NiDiffraction peaks, the presence of these two nickel oxides favours the improvement of OER performance. The FNC-acid-0.4Ni prepared by the acid treatment and the subsequent hydrothermal reaction and calcination has no NiOOH diffraction peak, and Fe₂O₃The intensity of the diffraction peak of (1) is greatly reduced and the existence of metal Ni is found, NiO is retained, which indicates that Fe on FNC₃The existence of C is beneficial to improving the oxidability of hydrothermal reaction, promoting the generation of NiOOH and inhibiting the formation of metallic Ni. Simultaneously, metals Fe and FeN in FNC-acid-0.4Ni_0.0324The change is not so great as to indicate that the two are stably present in the carbon coating, which is advantageous for maintaining the catalytic activity of the ORR.

As shown in FIG. 2, the XPS spectrum of example 1 is shown. FIG. 2a shows an XPS summary spectrum of FNC-0.4Ni, where C, O, N, Fe and the signal of Ni element were detected and the presence of N indicates successful N doping. The C1s map of FIG. 2b can be divided into 4 peaks, each corresponding to sp²-C(284.8eV)、sp³C (285.6eV), C-N (286.6eV) and O-C ═ O (289.4eV), the presence of C-N bonds again confirming the success of N doping. The peaks of the O1s spectrum of FIG. 2c at 530.5eV, 532.4eV, and 534.0eV correspond to Fe₂O₃Lattice oxygen, surface adsorbed water and O-C bonds in NiOOH and NiO. The N1s spectrum of fig. 2d can be divided into 3 peaks at 398.6eV, 400.3eV and 401.3eV, corresponding to pyridine N, pyrrole N and graphite N, respectively, with the largest proportion of pyrrole N, while both pyrrole N and pyridine N possess high ORR catalytic activity. FIG. 2e is the spectrum of Fe2p with two peaks at 711.5eV and 724.6eV corresponding to Fe³⁺The signals of the metals Fe and Fe-Nx are not detected, and may be caused by the small surface content. Ni was detected in Ni2p of FIG. 2f²⁺(855.4eV, 873.1eV) and Ni³⁺(856.7eV, 874.6eV), and two peaks at 862.2eV and 880.4eV belong to the accompanying peaks. Calculation of the area of the peak to obtain Ni³⁺/Ni²⁺Is 2.32, indicating that NiOOH is enriched at the surface, which is beneficial for improvement of OER performance.

As shown in FIG. 3a, for Pt/C, FNC prepared in comparative example 7, FNC-0.4Ni prepared in example 1, and FNC-acid-0.4Ni prepared in comparative example 8, in O₂LSV curve in saturated 0.1M KOH. Table 4 shows the results obtained in FIG. 3aCompared with FNC, the half-wave potential and the limiting current density of FNC-0.4Ni of the composite nickel oxide are reduced in the different samples, but the limiting current density is still close to that of Pt/C, and still shows good ORR activity.

FIG. 3b shows RuO₂FNC prepared in comparative example 7, FNC-0.4Ni prepared in example 1, and FNC-acid-0.4Ni prepared in comparative example 8 were added to N₂LSV curves in saturated 1M KOH, Table 5 for the 10mA cm of each sample in FIG. 3b^-2At the corresponding potential, FNC is shown to be inert to OER, while FNC-0.4Ni shows the most excellent OER performance and is even better than that of the noble metal RuO₂Description of Fe₂O₃The combination of NiOOH and NiO greatly improves the OER performance of the catalyst. In addition, the OER performance of FNC-acid-0.4Ni is reduced, which indicates that Fe₂O₃NiOOH plays an important role in OER.

TABLE 4

TABLE 5

From the examples and comparative examples, only in the case of proper material ratio, when the molar ratio of the nitrogen source to the iron salt is (2-32): 1; in the step S2, the mass ratio of the solid to the carbon black is (5-20): 1; the mass ratio of the powder, the nickel salt and the precipitant in the step S3 is 1: 2: 3-8: 2: 0.3, the high ORR catalytic active sites are exposed, and the oxygen reduction reaction is promoted. Meanwhile, the appropriate material proportion enables the loading capacity of the transition metal oxide on the surface of the catalyst to be in a reasonable range, so that the composite material has excellent OER performance and the ORR activity is in a higher level.

FIGS. 4a and b are FNC-0.4Ni and Pt/C in O, respectively₂LSV curves before and after accelerated aging with 5000 cycles CV of cycling in saturated 0.1M KOH. After 5000 cycles of CV, the half-wave potential of FNC-0.4Ni is only reduced by 18mV and is lower than 21mV of Pt/C, and good ORR activity stability is realized. FIGS. 4c and d are FNC-0.4Ni and RuO, respectively₂In N₂LSV curves before and after accelerated aging of 1000 cycles of CV in saturated 1M KOH, FNC-0.4Ni at 10mA cm^-2The corresponding potential is reduced by only 20mV, while RuO₂OER activity is substantially lost and FNC-0.4Ni shows excellent stability of OER activity.

FIG. 5 is a long-time i-t curve of FNC-0.4Ni and Pt/C at a constant potential of 0.7V vs. RHE in 0.1M KOH, after 10h of work, the FNC-0.4Ni still maintains 93% of current retention rate which is much higher than 78% of that of Pt/C, and the FNC-0.4Ni is verified to have good ORR stability again.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A preparation method of an ORR and OER bifunctional catalyst is characterized by comprising the following steps:

s1, dissolving and mixing the nitrogen source and the ferric salt, stirring, and drying to obtain a solid after stirring;

s3, mixing the powder obtained in the step S2, nickel salt and a precipitator in deionized water, uniformly dispersing the mixture, carrying out hydrothermal reaction at 110-130 ℃ for 4-12 h, separating and drying the mixture, and calcining the mixture at 300-600 ℃ in a protective atmosphere to obtain the high-efficiency ORR and OER dual-function catalyst;

non-active Fe formed by utilizing iron and nitrogen co-doped carbon catalyst₃C as iron source, then nickel salt and precipitator, and Fe with OER performance through hydrothermal reaction and subsequent calcination₂O₃The NiOOH and the NiO are compounded on the iron-nitrogen co-doped carbon catalyst;

2. the method according to claim 1, wherein the molar ratio of the nitrogen source to the iron salt in step S1 is (2-28): 1.

3. the production method according to claim 1, wherein the mass ratio of the solid to the carbon black in step S2 is (5-17): 1.

4. the method according to claim 1, wherein the mass ratio of the powder, the nickel salt and the precipitant in step S3 is 1: 2: 3-6: 2: 1.

5. the preparation method according to claim 1, wherein the carbon black is one or more of ketjen black, acetylene black or conductive carbon black.

6. The method according to claim 1, wherein the nitrogen source in step S1 is one or more selected from melamine, dicyanodiamine and urea; in the step S1, the iron salt is one of ferric chloride, ferric nitrate and ferric acetate.

7. The method according to claim 1, wherein the nickel salt in step S3 is at least one of nickel nitrate, nickel chloride, and nickel acetate.

8. The method according to claim 1, wherein the precipitant is urea and/or ammonia water in step S3.

9. The ORR and OER bifunctional catalyst obtained by the preparation method of any one of claims 1-8.

10. Use of the ORR and OER dual-function catalyst of claim 9 in a metal air cell or a fuel cell.