阅读说明：本技术 一种以生物质碳源为模板负载金属纳米颗粒催化剂及其制备方法和应用 (Metal nanoparticle-loaded catalyst taking biomass carbon source as template and preparation method and application thereof ) 是由 秦伟 侯光耀 贾鑫 卢松涛 康红军 于 2021-09-10 设计创作，主要内容包括：本发明公开了一种以生物质碳源为模板负载金属纳米颗粒催化剂及其制备方法和应用,属于新能源材料技术以及电化学催化领域。本发明将酵母菌作为碳模板,在酵母菌表面包覆金属有机框架(MOF)作为前驱体。该方法可以有效地防止活性位点从基底上脱落从而增强催化剂的稳定性。通过控制金属有机框架的负载量、碳化温度等参数,可以对最终产物的性能起到调节作用。本发明制备的催化剂在1mol/L的KOH电解液中,当电流密度为10mA/cm～(2),反应20h,催化剂的催化活性几乎没有衰减,具有良好的稳定性。(The invention discloses a metal nanoparticle-loaded catalyst taking a biomass carbon source as a template, and a preparation method and application thereof, and belongs to the fields of new energy material technology and electrochemical catalysis. The invention takes saccharomycetes as a carbon template, and coats a Metal Organic Framework (MOF) on the surface of the saccharomycetes as a precursor. The method can effectively prevent the active sites from falling off the substrate, thereby enhancing the stability of the catalyst. The performance of the final product can be adjusted by controlling the parameters such as the loading capacity, the carbonization temperature and the like of the metal organic framework. The catalyst prepared by the invention is in 1mol/L KOH electrolyte, and when the current density is 10mA/cm 2 And after the reaction is carried out for 20 hours, the catalytic activity of the catalyst is hardly attenuated, and the catalyst has good stability.)

1. The catalyst is characterized in that a yeast is taken as a template, ZIF-67 is coated on the outer surface of the yeast to obtain a precursor [email protected] yeast, and the [email protected] yeast is heated and carbonized to obtain the metal NPs @ NPC catalyst taking biomass carbon, nitrogen and phosphorus sources as templates to load metal nanoparticles.

2. The preparation method of the catalyst with the biomass carbon source as the template and the metal nanoparticles, which is described in claim 1, is characterized by comprising the following steps:

step 1, purifying yeast;

dispersing Angel yeast into deionized water, culturing at room temperature for 24h, discarding the upper layer turbid liquid, centrifuging and cleaning with deionized water, centrifuging, and lyophilizing to obtain purified yeast;

step 2, preparing metal ions/yeast;

dispersing the purified yeast obtained in the step 1 in a transition metal salt solution, stirring for 24 hours, and centrifuging to obtain the yeast with metal ions adsorbed on the surface;

step 3, preparing [email protected] yeast;

mixing the yeast with the metal ions adsorbed on the surface obtained in the step 2 with a 2-methylimidazole solution, stirring for 8-12 h, carrying out centrifugal cleaning by using deionized water, and finally centrifuging and freeze-drying to obtain a precursor [email protected] yeast;

step 4, preparing metal NPs @ NPC;

and (3) grinding the precursor [email protected] microzyme obtained in the step (3) into powder, placing the powder in a porcelain boat, placing the porcelain boat in a tubular furnace, heating and carbonizing the powder in an argon atmosphere, and cooling the carbonized powder to room temperature along with the furnace after carbonization is finished to obtain the metal NPs @ NPC catalyst.

3. The method for preparing the catalyst using the biomass carbon source as the template and loading the metal nanoparticles as claimed in claim 2, wherein the transition metal salt solution in the step 2 is cobalt nitrate and/or nickel nitrate solution.

4. The method for preparing the catalyst with the biomass carbon source as the template and the supported metal nanoparticles as claimed in claim 2, wherein the treatment conditions of the heating carbonization in the step 4 are as follows: heating at a heating rate of 3 ℃/min to 350-1000 ℃, and keeping the temperature for 2 h.

5. The preparation method of the catalyst with the biomass carbon source as the template and the metal nanoparticles, as claimed in claim 2, is characterized in that the metal NPs @ NPC catalyst has a particle size of 25 nm-35 nm.

6. The application of the metal nanoparticle catalyst supported by the biomass carbon source as the template in the alkaline electrolysis water anode OER as claimed in claim 1.

Technical Field

The invention relates to a metal nanoparticle-loaded catalyst taking a biomass carbon source as a template, and a preparation method and application thereof, and belongs to the fields of new energy material technology and electrochemical catalysis.

Background

Hydrogen energy is a promising clean energy, and hydrogen production by water electrolysis is a green pollution-free production mode. The electrolytic water reaction includes a cathodic Hydrogen Evolution Reaction (HER) and an anodic Oxygen Evolution Reaction (OER). Although theoretically, only 1.23V is needed to make the water electrolysis reaction proceed smoothly, since OER is a complicated four-electron transfer process, the reaction is slow, and a high overpotential is needed to make the water electrolysis proceed smoothly. The current commercial OER catalyst mainly comprises IrO₂And RuO₂However, these precious metals are scarce in natural reserves, expensive, unstable under acidic or basic conditions, and therefore, it is necessary to develop a stable non-precious metal catalyst.

The preparation method of the prior non-noble metal catalyst comprises the following steps: and (3) carrying out high-temperature calcination treatment on the precursor with the pre-designed morphology to obtain the micro-nano carbon material. After high-temperature carbonization treatment, the electron transmission capability of the material is improved, the catalytic activity is improved, and the method has great application value in the fields of energy conversion/storage and the like. However, the preparation method has high requirements on the selection of precursors.

The transition metal nano-particles are a material capable of replacing a noble metal catalyst, and the transition metal has the following characteristics: compared with precious metal, the natural reserve is rich, the price is low, the preparation is easy, the environment is friendly, and the like. The carbon material widely exists in nature, has high specific surface area, high conductivity, good chemical stability and low cost, and is especially sp²Graphite, graphene, carbon nanotubes and the like formed in a hybrid form have good conductivity and are often used as a conductive substrate for preparing an OER composite catalyst. However, in the composite catalyst, the metal nanoparticles are unevenly distributed in the carbon material, and have the problems of small specific surface area, low catalytic performance and the like.

Disclosure of Invention

The invention aims to solve the technical problems in the prior art and provides a metal nanoparticle catalyst loaded by using a biomass carbon source as a template, and a preparation method and application thereof.

The technical scheme of the invention is as follows:

a biomass carbon source is used as a template to load a metal nanoparticle catalyst, yeast is used as a template, ZIF-67 is coated on the outer surface of the yeast to obtain a precursor [email protected] yeast, and then the [email protected] yeast is heated and carbonized to obtain the metal NPs @ NPC catalyst with biomass carbon, nitrogen and phosphorus sources as templates to load metal nanoparticles.

The preparation method of the metal nanoparticle-loaded catalyst by taking the biomass carbon source as the template comprises the following steps:

step 1, purifying yeast;

dispersing Angel yeast into deionized water, culturing at room temperature for 24h, discarding the upper layer turbid liquid, centrifuging and cleaning with deionized water, centrifuging, and lyophilizing to obtain purified yeast;

step 2, preparing metal ions/yeast;

dispersing the purified yeast obtained in the step 1 in a transition metal salt solution, stirring for 24 hours, and centrifuging to obtain the yeast with metal ions adsorbed on the surface;

step 3, preparing [email protected] yeast;

mixing the yeast with the metal ions adsorbed on the surface obtained in the step 2 with a 2-methylimidazole solution, stirring for 8-12 h, carrying out centrifugal cleaning by using deionized water, and finally centrifuging and freeze-drying to obtain a precursor [email protected] yeast;

step 4, preparing metal NPs @ NPC;

and (3) grinding the precursor [email protected] microzyme obtained in the step (3) into powder, placing the powder in a porcelain boat, placing the porcelain boat in a tubular furnace, heating and carbonizing the powder in an argon atmosphere, and cooling the carbonized powder to room temperature along with the furnace after carbonization is finished to obtain the metal NPs @ NPC catalyst.

Further, in the step 2, the transition metal salt solution is cobalt nitrate and/or a mixed solution of cobalt nitrate and nickel nitrate.

Further limiting, the processing conditions of the heating carbonization in the step 4 are as follows: heating at a heating rate of 3 ℃/min to 350-1000 ℃, and keeping the temperature for 2 h.

Further defined, the metal NPs @ NPC catalyst has a particle size of 25nm to 35 nm.

The catalyst taking the biomass carbon source as the template to load the metal nanoparticles is applied to the alkaline electrolyzed water anode OER.

The invention has the following beneficial effects:

the invention takes saccharomycetes as a carbon template, and coats a Metal Organic Framework (MOF) on the surface of the saccharomycetes as a precursor. The method can effectively prevent the active sites from falling off the substrate, thereby enhancing the stability of the catalyst. The performance of the final product can be adjusted by controlling the parameters such as the loading capacity, the carbonization temperature and the like of the metal organic framework. In addition, the invention also has the following advantages:

(1) the invention adopts yeast containing rich N, P, C elements as a template carrier to prepare the metal NPs @ yeast catalyst, thereby not only improving the distribution uniformity of metal nanoparticles and reducing the overpotential of OER catalytic reaction, but also effectively fixing catalytic active sites and improving the stability of the catalyst, and being an ideal catalyst.

(2) The catalyst prepared by the method is a non-noble metal composite material, the used raw materials are easy to purchase, obtain and prepare, the resource is rich, the price is low, and the method is suitable for large-scale preparation.

(3) The catalyst prepared by the invention is in 1mol/L KOH electrolyte, and when the current density is 10mA/cm²And after the reaction is carried out for 20 hours, the catalytic activity of the catalyst is hardly attenuated, and the catalyst has good stability.

(4) The catalyst prepared by the invention takes a biomass carbon nitrogen phosphorus source as a carrier, and the composite material loaded with metal nano particles has better catalytic activity compared with the non-noble metal OER catalyst reported in the current research.

Drawings

FIG. 1 is an XRD spectrum of [email protected] yeast obtained in example 1 and ZIF-67 obtained in comparative example 2;

FIG. 2 is the XRD patterns of CoNi NPs @ NPC-350 obtained in example 2, CoNi NPs @ NPC-800 obtained in example 3, and CoNi NPs @ NPC-1000 obtained in example 4;

FIG. 3 is a Fourier transform infrared spectrum of the [email protected] yeast obtained in example 1 and the yeast obtained in comparative example 2;

FIG. 4 is an SEM photograph (at different magnifications) of [email protected] yeast obtained in example 1;

FIG. 5 is an SEM image (different positions) of CoNi NPs @ NPC-350 obtained in example 2;

FIG. 6 is an OER linear voltammogram of CoNi NPs @ NPC-350 obtained in example 2, yeast-350 obtained in comparative example 1, ZIF-67-350 obtained in comparative example 3, and bare carbon paper electrode;

FIG. 7 is a Tafel plot of CoNi NPs @ NPC-350 obtained in example 2, yeast-350 obtained in comparative example 1, ZIF-67-350 obtained in comparative example 3, and bare carbon paper electrode;

FIG. 8 is a CV curve of CoNi NPs @ NPC-350 obtained in example 2;

FIG. 9 is a graph of a double layer capacitance fit estimate of CoNi NPs @ NPC-350 obtained in example 2;

FIG. 10 is an impedance plot of CoNi NPs @ NPC-350, yeast-350 obtained in comparative example 1, ZIF-67-350 obtained in comparative example 3, and bare carbon paper electrode;

FIG. 11 is a CoNi NPs @ NPC-350 modified carbon paper electrode at 10mA · cm^-2The following i-t plot.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The experimental procedures used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and apparatus used, unless otherwise specified, are conventional in the art and are commercially available to those skilled in the art.

Example 1:

preparation of [email protected] yeast

(a) Purification of yeast

Prepared according to the method and conditions of step (a) in example 1.

(b)Co²⁺、Ni²⁺Preparation of yeast

Collecting 300mg of purified yeast obtained in step (a), and dispersing into 50mL of a solution containing 5mmol of Co (NO)₃)₂·6H₂O and 5mmol of Ni (NO)₃)₂·6H₂Stirring for 24 hours in the O solution to ensure that Co is added²⁺、Ni²⁺Adsorbed on the surface of yeast. And finally, centrifuging at a certain rotating speed to remove the unadsorbed metal salt solution.

(c) Preparation of [email protected] yeast

Adsorbing Co in the step (b)²⁺、Ni²⁺The yeast is dispersed in 50mL solution containing 1g of 2-methylimidazole, stirred for 12h, and finally repeatedly centrifugally washed for 3 times by deionized water at the rotating speed of 3000rpm, and the solution is freeze-dried and freeze-dried to obtain the [email protected] yeast.

Example 2:

preparation of CoNiNPs @ NPC-350

(a) Purification of yeast

Prepared according to the method and conditions of step (a) in example 1.

(b)Co²⁺、Ni²⁺Preparation of yeast

Collecting 300mg of purified yeast obtained in step (a), and dispersing into 50mL of a solution containing 5mmol of Co (NO)₃)₂·6H₂O and 5mmol of Ni (NO)₃)₂·6H₂Stirring for 24 hours in the O solution to ensure that Co is added²⁺、Ni²⁺Adsorbed on the surface of yeast. And finally, centrifuging at a certain rotating speed to remove the unadsorbed metal salt solution.

(c) Preparation of [email protected] yeast

Adsorbing Co in the step (b)²⁺、Ni²⁺Dispersing the yeast in 50mL solution containing 1g 2-methylimidazole, stirring for 12h, repeatedly centrifuging and cleaning with deionized water at 3000rpm for 3 times, and coolingFreeze-drying, and freeze-drying to obtain [email protected] yeast.

(d) CoNiNPs @ NPC-350 preparation

And (c) placing a certain amount of the [email protected] yeast precursor obtained in the step (c) in a porcelain boat in a tube furnace, heating to 350 ℃ at the heating rate of 3 ℃/min in the argon atmosphere, then preserving heat for 2h, and cooling to room temperature along with the furnace to obtain the CoNi NPs @ NPC-350.

Example 3:

preparation of CoNiNPs-800

The difference between this example and example 2 is that the temperature in step (d) was maintained at 800 ℃ for 2h, and the rest of the operation steps and the parameter settings were the same.

The obtained CoNi NPs-800 catalyst has a current density of 10mAcm^-2The overpotential was 292 mV.

Example 4:

[email protected]

the difference between this example and example 2 is only that in step (d) the temperature is maintained at 1000 ℃ for 2h, and the rest of the operation steps and the parameter settings are the same.

The obtained CoNi NPs-1000 catalyst has a current density of 10mAcm^-2Next, the overpotential was 305 mV.

Comparative example 1:

preparation of Yeast-350

(a) Purification of yeast

Dispersing a certain amount of Angel yeast (containing yeast nutrient matrix) into a certain amount of deionized water, and culturing at room temperature for 24h to consume nutrient substances to obtain relatively pure yeast. And then pouring out the upper layer turbid liquid, repeatedly centrifuging and cleaning the yeast by using deionized water at a certain rotating speed, and then freeze-drying the yeast to obtain the purified yeast after freeze-drying.

(b) Preparation of Yeast-350

Putting a certain amount of the 'pure yeast' precursor obtained in the step (a) into a porcelain boat in a tube furnace, heating to 350 ℃ at the heating rate of 3 ℃/min in the argon atmosphere, then preserving heat for 2h, and cooling to room temperature along with the furnace to obtain the yeast-350.

Comparative example 2:

preparation of ZIF-67

(a) Preparing solution

Preparing a solution A: 2.5mmol Co (NO)₃)₃·6H₂Dissolving O in 50mL of methanol;

preparing a solution B: dissolving 10mmol of 2-methylimidazole in 50mL of methanol;

(b) ZIF-67 preparation

And slowly adding the solution B into the solution A, stirring at room temperature for 30min, standing at room temperature for 12h, centrifuging to obtain a purple precipitate, washing with methanol for 3 times, placing in a vacuum drying oven, and drying to obtain ZIF-67.

Comparative example 3:

preparation of ZIF-67-350

(a) Preparing solution

Preparing a solution A: 2.5mmol Co (NO)₃)₃·6H₂Dissolving O in 50mL of methanol;

preparing a solution B: dissolving 10mmol of 2-methylimidazole in 50mL of methanol;

(b) ZIF-67 preparation

And slowly adding the solution B into the solution A, stirring at room temperature for 30min, standing at room temperature for 12h, centrifuging to obtain a purple precipitate, washing with methanol for 3 times, placing in a vacuum drying oven, and drying to obtain ZIF-67.

(c) ZIF-67-350 preparation

And (3) placing a certain amount of the prepared precursor in a porcelain boat in a tube furnace, heating at the heating rate of 3 ℃/min to 350 ℃ in the argon atmosphere, then preserving heat for 2h, and cooling to room temperature along with the furnace to obtain ZIF-67-350.

The products obtained in the above examples were tested for performance and analyzed:

all electrochemical tests were done on Chenghua electrochemical workstation. In the electrolyte of 1M KOH solution, a three-electrode system is adopted for testing, catalytic powder is loaded on carbon paper to serve as a working electrode, a saturated Ag/AgCl electrode serves as a reference electrode, a carbon rod serves as a counter electrode, and the method is characterized in thatThe potential values of (a) are relative to the reversible hydrogen electrode. N is required to be carried out on the electrolyte before OER performance test₂And (5) saturation treatment.

5mg of the catalysts obtained in example 1, example 2, comparative example 1 and comparative example 2, which were uniformly ground, were dispersed in 970. mu.L of absolute ethanol and 30. mu.L of Nafion solution, and uniformly mixed by sonication for 30min, 100. mu.L of the mixed solution was uniformly applied to 1X 1cm²After they were completely dried, the OER performance was measured on an electrochemical workstation.

FIG. 1 is an XRD pattern of [email protected] yeast obtained in example 1 and ZIF-67 obtained in comparative example 2. FIG. 2 is the XRD patterns of CoNiNPs @ NPC-350 obtained in example 2, CoNiNPs @ NPC-800 obtained in example 3, and CoNi NPs @ NPC-1000 obtained in example 4. As can be seen from fig. 1, distinct ZIF-67 characteristic diffraction peaks appear in the pattern 2 θ ═ 7.52 °, 10.53 °, 12.87 °, 14.86 °, 16.61 ° and 18.16 °, indicating that ZIF-67 is successfully complexed with yeast. After calcination, the characteristic diffraction peak of ZIF-67 is lost, and then diffraction peaks of simple substance Co and simple substance Ni appear, which shows that CoNi nanoparticles (CoNi NPs) synthesized by calcination are loaded on a yeast derivative (CNP) material, namely CoNi NPs @ NPC.

FIG. 3 is a Fourier transform infrared spectrum of [email protected] yeast obtained in example 1 and ZIF-67 obtained in comparative example 2. The FT-IR showed that the wavelengths were 3357, 2930, 1648, 1538, 1400, 1240, and 1066cm^-1All belong to characteristic absorption peaks of yeast surface functional groups, wherein the absorption peak is 3357cm^-1The signal peak of (A) corresponds to the stretching vibration of-OH \ NH overlapped on the surface of the saccharomycete; 2930cm^-1The signal peak of (2) corresponds to CH stretching vibration; 1400cm^-1The signal peak of (a) corresponds to stretching vibration of C ═ O of the carboxyl group; 1648. 1538 and 1240cm^-1The signal peaks of (a) correspond to the oscillations of amide I, amide II and amide III, respectively, indicating the presence of protein in the yeast cell; 1066cm^-1The signal peak of (b) corresponds to the stretching vibration of P ═ O. The abundant functional groups on the surface of the yeast play an important role in the adsorption of metal ions. The wavelength is 1305, 1143, 745, 685cm^-1Both belonging to the characteristic absorption peaks of stretching vibration and bending vibration of the ZIF-67-related functional group, wherein 1305 and 1143cm^-1Signal peak of (2) corresponds to the bend of the imidazole ringPerforming curved vibration; 745cm^-1The signal peak of (a) corresponds to the stretching vibration of Co-N. Through Fourier infrared spectrum analysis, the signal peaks of the two samples are basically completely matched, and the success of compounding the ZIF-67 and the yeast is further proved.

FIG. 4 is an SEM photograph of [email protected] yeast obtained in example 1. As can be seen from the figure, the spherical morphology of the yeast was maintained while the ZIF-67 was loaded on the yeast surface, and the yeast surface became rough. FIG. 5 is an SEM image of CoNi NPs @ NPC-350 obtained in example 2. As can be seen from the figure, the yeast and ZIF-67 derivatives have finely dispersed metal nanoparticles distributed on the surface, and these finely uniform nanoparticles play an important role in oxygen evolution catalytic reactions.

FIG. 6 is an OER linear voltammogram of CoNi NPs @ NPC-350 obtained in example 2, yeast-350 obtained in comparative example 1, ZIF-67-350 obtained in comparative example 3, and bare carbon paper electrode. As shown in FIG. 6, the current density was 10mAcm^-2Under the conditions, NPC obtained by calcining pure yeast has poor OER activity and the initial overpotential is 417 mV. After ZIF-67 is compounded with yeast, the initial overpotential of CoNiNPs @ NPC-350 obtained after calcination is reduced to 296 mV. The main reason is that in the compounding process, metal ions are uniformly adsorbed on the surface of the yeast, and then the metal ions are coordinated with the 2-methylimidazole organic ligand, so that a ZIF-67 'coat' is formed on the surface of the yeast, and the metal ions serving as active sites can be well anchored on the surface of the yeast. High temperature calcination in an inert atmosphere, Co²⁺And Ni²⁺The carbon is converted into CoNi alloy nano particles under the reduction action of carbon, and the conductivity and the electrocatalytic performance are greatly improved due to the existence of the alloy nano particles, so that the low overpotential is shown.

FIG. 7 is a Tafel plot of CoNi NPs @ NPC-350 obtained in example 2, yeast-350 obtained in comparative example 1, ZIF-67-350 obtained in comparative example 3, and bare carbon paper electrode. The slope of the Tafel curve was used to treat the low current region of the resulting LSV polarization curve to evaluate catalyst kinetic performance. As shown in FIG. 7, the Tafel slope of CoNi nanoparticles loaded on yeast derivative NPC is the minimum, and is 58mVdec^-1. The fitting result of Tafel slope further verifies the LSV poleAnd (5) changing the rule obtained by the curve.

FIGS. 8 and 9 are graphs of CV curves and double layer capacitance fit estimates of CoNiNPs @ NPC-350 obtained in example 2, respectively. Cyclic voltammograms at different sweep rates (40mV/s, 60mV/s, 80mV/s, 100mV/s, 120mV/s) for the CoNiNPs @ NPC-350 sample. As can be seen in FIG. 8, as the sweep rate increases, the current density of CoNi NPs @ NPC-350 increases; the electric double layer capacitance can be used for reflecting the size of an electrochemical active area, and under the same sweeping speed, the larger the rectangular area reflects that the larger the electric double layer capacitance is, the reaction active surface area is in direct proportion to the electric double layer capacitance value. The electric double layer capacitance value can pass at 1.362VEstimated from the slope values of the linear fit curve to the scan rate, it can be seen from FIG. 9 that the electric double layer capacitance value of CoNi NPs @ NPC-350 is 6.16 mF-cm^-2。

FIG. 11 shows CoNiNPs @ NPC-800 electrode obtained in example 2 at 10mA · cm^-2Constant current test pattern below. As shown in the figure, after a continuous oxygen evolution process of 20h, the OER potential of CoNiNPs @ NPC-350 is only slightly changed, mainly because oxygen bubbles are continuously evolved to continuously wash the surface of an electrode, and the electrode material is slightly fallen off, so that CoNi NPs @ NPC shows good OER catalytic stability in an alkaline solution and has long service life.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.