CN113186508A

CN113186508A - Method for simply preparing nickel atomic cluster oxygen evolution catalyst

Info

Publication number: CN113186508A
Application number: CN202110459157.0A
Authority: CN
Inventors: 凌敏; 吉加鹏; 梁成都
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2021-04-27
Filing date: 2021-04-27
Publication date: 2021-07-30
Anticipated expiration: 2041-04-27
Also published as: CN113186508B

Abstract

The invention discloses a method for simply preparing a nickel cluster oxygen evolution catalyst, which takes nickel acetylacetonate as a precursor and multi-walled carbon nanotubes (MWCNTs) as a carrier, and is prepared by a low-temperature gas migration reaction method, and specifically comprises the following steps: respectively putting nickel acetylacetonate and MWCNTs powder into a quartz test tube, inserting the quartz test tube into a tube furnace, preheating and drying moisture at 100 ℃ under the protection of argon, heating the whole system to 300 ℃ at the speed of 3 ℃/min, and preserving heat for 6 hours; with nickel acetylacetonate powder placed upstream and MWCNTs powder placed downstream. The method can effectively reduce the production cost of the atomic cluster catalyst, the synthesis process is very simple and easy to control, the product uniformity is high, the yield is high, the repeatability is good, the activity of the prepared catalyst is good, the catalyst can be compared with a noble metal catalyst, and the method has an excellent prospect.

Description

Method for simply preparing nickel atomic cluster oxygen evolution catalyst

Technical Field

The invention belongs to the technical field of monatomic catalysts, relates to a nickel cluster oxygen evolution catalyst material and a preparation method thereof, and particularly relates to a method for simply preparing a nickel cluster oxygen evolution catalyst, wherein a multi-walled carbon nanotube is anchored with a nickel cluster.

Background

Since the concept of the monatomic catalyst was first proposed by the academy of billows and colleagues in the university union in 2011, the monatomic catalyst has the advantages of hundreds of theoretical atom utilization rate, unique coordination structure and electronic property, and relatively uniform active sites, and shows excellent activity, selectivity and stability in series of important catalytic reactions such as small molecule activation conversion, organic catalysis, electrocatalysis and the like. However, single metal single atom catalysts lack synergistic effects between metal atoms and are less suitable for multi-step, multi-electron transfer reactions. Therefore, it is necessary to develop a low nuclear cluster catalyst, so as to increase the synergistic effect between metal atoms while achieving high atom utilization rate, and further improve the performance of the atomic-scale catalyst.

At present, the preparation methods of the low nuclear cluster catalyst are reported, and comprise a size selection method, an atomic layer deposition method and a precursor pre-selection synergistic pyrolysis method. But precursors and equipment of a size selection method and an atomic layer deposition method are expensive, the preparation speed is slow, and the yield is low; the precursor pre-selection synergistic pyrolysis method needs expensive organic ligands and high-temperature heat treatment, and is not environment-friendly. Thus, such methods still have significant disadvantages and are difficult to apply on a large scale.

Disclosure of Invention

The invention aims to provide a method for simply preparing a nickel atomic cluster oxygen evolution catalyst aiming at the defects of the prior art. The method is very simple, can be used for mass preparation in a tube furnace, and the oxygen evolution catalyst is obtained by anchoring nickel atom clusters in the multi-wall carbon nano tube.

The invention is realized by the following technical scheme:

a method for simply preparing a nickel atomic cluster oxygen evolution catalyst is characterized in that acetylacetone metal with low boiling point is used as a precursor, multi-walled carbon nanotubes (MWCNTs) are used as carriers, and the nickel atomic cluster oxygen evolution catalyst is prepared by a low-temperature gas migration method; the method has the advantages of low cost, easy control, high uniformity, high yield, good repeatability and good catalytic activity of the product.

The method specifically comprises the following steps:

preparation of multiwalled carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs)

Firstly, nickel acetylacetonate (boiling point: 220-235 ℃) and MWCNTs powder (the mass ratio of the nickel acetylacetonate to the MWCNTs powder is preferably 2:1) are respectively put into a quartz test tube. It is then inserted into a tube furnace quartz tube, preheated to dry moisture (typically 120 minutes at 100 ℃) with the nickel acetylacetonate powder placed upstream and the MWCNTs powder placed downstream. In the low-temperature heat treatment process (preferably, the whole system is heated to 300 ℃ at the speed of 3 ℃/min, and the temperature is kept for 6 hours, too low temperature and too short time are not beneficial to nickel acetylacetonate gasification migration deposition, too high temperature is not beneficial to nickel acetylacetonate and MWCNTs to fully react, and too long heat treatment time is wasted electric energy), the upstream organometallic precursor is gasified and migrated to the vicinity of downstream MWCNTs, and is anchored by defects on the surface of the MWCNTs. The whole process is carried out under the protection of inert argon. After natural cooling to room temperature, the obtained black sample (labeled as Ni-MWCNTs) was taken out for use as an electrocatalyst without any subsequent treatment.

The multi-walled carbon nanotube anchoring nickel cluster catalyst prepared by adopting a low-temperature gas migration method does not need high-temperature or acid treatment, realizes uniform distribution by anchoring nickel clusters by using defects on the carbon nanotube, and has a Ni atomic mass content of about 0.46 percent measured by inductively coupled plasma mass spectrometry. The multi-walled carbon nanotube anchored nickel cluster catalyst prepared by the invention is applied to electrochemical decomposition of water and oxygen evolution, so that excellent electrocatalytic performance is obtained, the electrocatalytic oxygen evolution performance exceeds that of commercial ruthenium oxide under alkaline conditions, and the conversion rate (TOF) of unit time unit site reaches 179 times of that of ruthenium oxide. The method has the characteristics of simple operation, low price, simple equipment and high yield, and is a method for quickly and simply preparing the low-nuclear-cluster catalyst.

Drawings

FIG. 1 is an X-ray diffraction pattern of the multiwall carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs) prepared in example 1, as measured by a LabX XRD-6000 type X-ray diffractometer, manufactured by Shimadzu corporation, Japan, in which: the abscissa X is the diffraction angle (2 θ), and the ordinate Y is the relative diffraction intensity. The product is Ni-MWCNTs.

FIG. 2 is a Raman spectrum analysis measured by laser confocal Raman spectroscopy (Raman) of the multiwalled carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs) prepared in example 1. The product is Ni-MWCNTs.

FIG. 3 is an infrared absorption spectrum of the multiwalled carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs) prepared in example 1, as measured by Fourier transform infrared spectroscopy (FTIR). The product is Ni-MWCNTs.

FIG. 4 is an X-ray absorption spectrum of the multi-walled carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs) prepared in example 1, as measured by X-ray photoelectron spectroscopy (XPS). The product is Ni-MWCNTs.

FIG. 5 is a graph of the morphology of the multiwalled carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs) prepared in example 1, observed by a field emission scanning electron microscope (FE-SEM) model S-4800, Hitachi, Japan. The product is Ni-MWCNTs.

FIG. 6 is a graph of the morphology of the multiwalled carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs) prepared in example 1, observed by a 200kv spherical aberration electron microscope (HAADF-STEM) in Heidelberg, Germany. The product is Ni-MWCNTs.

FIG. 7 is the result of the synchrotron radiation absorption spectrum extension X-ray absorption fine structure R space of Ni element in multi-walled carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs).

FIG. 8 is a polarization curve of multiwall carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs) and commercial ruthenium oxide in 1.0M KOH.

FIG. 9 is a multi-walled carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs) and commercial ruthenium oxide maintained at a current density of 10mA cm in 1.0M KOH^-2Voltage time curve of (c) versus graph.

Detailed Description

The technical solution of the present invention is further specifically described below by way of examples.

Example 1:

first, 100mg of nickel acetylacetonate and 50mg of MWCNTs powder were put into a quartz tube, respectively. And then inserting the powder into a quartz tube of a tube furnace, preheating for 120 minutes at 100 ℃ under the protection of inert argon, and drying moisture, wherein the acetylacetone nickel powder is placed at the upstream, and the MWCNTs powder is placed at the downstream. The whole system was then heated to 300 ℃ at a rate of 3 ℃/min and held for 6 hours. After naturally cooling to room temperature, the obtained black product (labeled as Ni-MWCNTs) was taken out and analyzed as follows.

The Ni-MWCNTs prepared in this example were subjected to X-ray diffraction analysis, and the results are shown in FIG. 1, wherein X is the diffraction angle (2. theta.) and Y is the relative diffraction intensity; in the Ni-MWCNTs sample in figure 1, only the characteristic peak (200) of the fullerene and the characteristic peak (002) of the graphite appear, and the diffraction peaks of the metal nickel and the organic nickel do not appear.

When the Ni-MWCNTs sample prepared in this example was subjected to Raman spectroscopy, as shown in FIG. 2, it can be seen that the G peak and the 2D peak were significantly blue-shifted due to surface doping of nickel clusters.

The Ni-MWCNTs samples prepared in this example were analyzed by infrared absorption spectroscopy. As can be seen from FIG. 3, the Ni-MWCNTs sample prepared in this example exhibited a C ═ O stretching vibration peak (1797 cm)^-1) And C-O stretching vibration peak (1062 cm)^-1) Enhanced, indicating Ni (acac)₂The molecules are successfully adsorbed on the surface of MWCNTs.

The Ni-MWCNTs samples prepared in this example were subjected to X-ray photoelectron spectroscopy. As can be seen from FIG. 4, the Ni 2p high resolution photoelectron spectrum of the Ni-MWCNTs sample prepared in this example is mainly in positive valence state, and no peak of metallic nickel with zero valence appears.

The product prepared in this example is analyzed by SEM, and the obtained SEM image is shown in FIG. 5, from which it can be seen that the Ni-MWCNTs sample prepared in this example still maintains the basic morphology of carbon nanotubes.

The Ni-MWCNTs sample prepared in the embodiment is subjected to high-angle STEM spherical aberration electron microscope analysis, and the obtained electron microscope photo is shown in FIG. 6, and it can be seen from the image that under 5nm Scale bars, the bright spots in the image are Ni clusters, which visually proves the successful preparation of the nickel cluster catalyst.

The Ni-MWCNTs sample prepared in this example was subjected to synchrotron radiation absorption spectroscopy, and the results of the extended X-ray absorption fine structure R space are shown in FIG. 7, in which nickel exists in the form of low nuclear atom clusters, coordinated with oxygen atoms. The results of the synchrotron radiation test prove the successful preparation of the low-nuclear nickel cluster catalyst.

The polarization curve test in 1.0M KOH for the product prepared in this example 1 and commercial ruthenium oxide is shown in fig. 8, and the stability test is shown in fig. 9. The result shows that the Ni-MWCNTs have optimal activity and stability.

XRD, Raman, FTIR, XPS, SEM, HAADF-STEM, and LSV measurements and literature searches indicate: the multiwall carbon nanotube anchored nickel cluster catalyst (Ni-MWCNTs) prepared by the method is an atomic cluster oxygen evolution catalyst which is successfully synthesized by the current simpler method and has low cost, high activity and uniform size, the multiwall carbon nanotube supported nickel cluster is realized by using a low-temperature gas migration method for the first time, and the atomic cluster oxygen evolution catalyst is prepared, so that the method can play a certain role in promoting the further development and application of the low-cost non-noble metal atomic cluster catalyst.

Claims

1. A method for simply preparing a nickel atomic cluster oxygen evolution catalyst is characterized in that nickel acetylacetonate is used as a precursor, multi-walled carbon nanotubes (MWCNTs) are used as carriers, and the nickel atomic cluster oxygen evolution catalyst is prepared by a low-temperature gas migration reaction.

2. The method for simply preparing the nickel cluster oxygen evolution catalyst according to claim 1, which is characterized by comprising the following steps:

respectively putting nickel acetylacetonate and MWCNTs powder into a quartz test tube, inserting the quartz test tube into a tube furnace, preheating and drying moisture under the protection of argon, heating the whole system to at least 300 ℃, and preserving heat for at least 6 hours; with nickel acetylacetonate powder placed upstream and MWCNTs powder placed downstream.

3. The method for simply preparing a nickel cluster oxygen evolution catalyst according to claim 1, wherein the preheating is at 100 ℃ for 120 minutes.

4. The method for simply preparing a nickel cluster oxygen evolution catalyst as claimed in claim 1, wherein the heating rate is 3 ℃/min.

5. The method for simply preparing the nickel cluster oxygen evolution catalyst according to claim 1, characterized in that the sample obtained after the reaction is naturally cooled to room temperature can be used as the electrocatalyst without any post-treatment.

6. The method for simply preparing the nickel cluster oxygen evolution catalyst according to claim 1, characterized in that the mass ratio of the nickel acetylacetonate to the MWCNTs powder is 2: 1.