Graphene-loaded Pd nanoparticle catalyst and preparation method and application thereof

Abstract

The invention discloses a graphene-loaded Pd nanoparticle catalyst as well as a preparation method and application thereof, and belongs to the technical field of electro-catalysis. According to the preparation method, Lewis base ethylenediamine tetraacetic acid is modified on graphene oxide, Pd < 2 + > is reduced into Pd0 through a redox reaction, the Pd0 is uniformly loaded on the graphene oxide coated with EDTA, and the graphene-loaded Pd nanoparticle catalyst is obtained. And the catalyst shows excellent reduction activity, selectivity and stability, and shows a new idea and possibility that a metal-free molecule functionalized carrier is used for loading a noble metal catalyst to promote a CO2RR reaction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrocatalysis, and particularly relates to a graphene supported Pd nanoparticle catalyst and a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of generally presenting the context of the application. The information disclosed in this Background section is not to be necessarily taken as an acknowledgement or any form of suggestion that this information forms part of the prior art already known to a person skilled in the art.

[0003] Over-consumption of fossil energy leads to a sharp increase in atmospheric CO2 concentration, which exacerbates global climate change. As a resource, CO2 can be converted into high-value C1 and C2 products (such as CO, CH4, HCOOH, C2H4, etc.) through electrocatalytic reduction (CO2RR), but this process faces the bottleneck of low activity, low selectivity and poor stability of the catalyst, which restricts the conversion efficiency. It is urgent to develop efficient and low-cost electrocatalysts to improve the performance of CO2RR, especially to optimize the conversion path of CO2 to CO.

[0004] Among various electrocatalysts, Pd-based nanoparticles have the potential to optimize intermediate adsorption and reaction free energy due to their adjustable d-band electron structure, and are key materials for improving the performance of CO2RR. However, the electrocatalytic reduction activity of palladium nanoparticles needs to be improved due to their easy agglomeration. Unlike metal molecular catalysts, which use metal centers as active sites in the electrocatalytic reduction process, organic molecular catalysts usually promote chemical reactions through Lewis acid or Lewis base groups, but they have not been used to promote electrocatalytic reactions to improve the activity of CO2RR. SUMMARY

[0005] In order to solve the problems of the prior art, the present application aims to provide a graphene supported Pd nanoparticle catalyst and a preparation method and application thereof. The palladium nanoparticles in the catalyst provided by the present application are uniformly distributed without obvious accumulation, avoiding agglomeration, and the electrocatalytic reduction activity of carbon dioxide is high.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows: In a first aspect, the present application provides a graphene supported Pd nanoparticle catalyst, comprising ethylenediaminetetraacetic acid (EDTA) modified graphene oxide (GO) and palladium (Pd) nanoparticles. The palladium nanoparticles are supported on the ethylenediaminetetraacetic acid modified graphene oxide.

[0007] The application utilizes EDTA to modify GO, the addition of EDTA provides coordination sites for the anchoring of metal palladium, and EDTA functionalization can prevent Pd nanoparticle agglomeration and improve the dispersibility of Pd nanoparticles, and such uniform distribution is crucial for improving the activity and stability of the catalyst.

[0008] In some embodiments of the application, the particle size of the palladium nanoparticles is 3-10 nm, and the loading amount is 10-30 wt%. In the catalyst provided by the application, the palladium nanoparticles have small particle size and uniform distribution, and agglomeration is avoided.

[0009] It should be noted that the loading amount refers to the percentage of palladium nanoparticles in the mass of the composite material (i.e. graphene-supported Pd nanoparticle catalyst). For example, 1 g of graphene-supported Pd nanoparticle catalyst contains 1 g * (10-30 wt%) = 0.1-0.3 g of palladium nanoparticles.

[0010] In a second aspect of the application, a preparation method of the above-mentioned graphene-supported Pd nanoparticle catalyst is provided, which comprises: The graphene oxide and ethylenediaminetetraacetic acid are dissolved in an alcohol-water mixed solution, then ultrasonic treatment is performed, and then palladium acetylacetonate (Pd(acac)2) is added. After dissolution, sodium carbonate and a reducing agent are added, stirring is performed, centrifugation is performed, and freeze-drying is performed to obtain the graphene-supported Pd nanoparticle catalyst.

[0011] The application successfully prepares the graphene-supported Pd nanoparticle catalyst by using a two-step method. EDTA is used to modify GO, and the addition of EDTA provides coordination sites for the subsequent anchoring of metal palladium. Pd(acac)2 is added to the GO / EDTA dispersion system, and then a reducing agent is added. Through an oxidation-reduction reaction, Pd 2+ is reduced to Pd 0 which is uniformly supported on the EDTA-modified GO to obtain the graphene-supported Pd nanoparticle catalyst. The catalyst exhibits excellent reduction activity, selectivity and stability, and demonstrates a new idea and possibility of using metal-free molecular functionalization of the carrier to load noble metal catalysts to promote the CO2RR reaction.

[0012] In some embodiments of the application, the concentration of graphene oxide in the alcohol-water mixed solution is 0.1-1 mg / mL.

[0013] It should be noted that the graphene oxide of the application can be purchased or prepared by oneself. For example, the Hummers method can be used for preparation, or the improved Hummers method can be used for preparation. The improved Hummers method comprises the following steps: The graphite powder is used as raw material, and the graphite powder is layer by layer stripped through oxidation treatment, sulfuric acid and potassium permanganate are used as main oxidants, ice bath cooling is used to ensure the complete oxidation reaction, the product is uniformly dispersed by ultrasonic, and then centrifugal cleaning is carried out to remove the residual acid and impurities, so that the graphene oxide dispersion liquid is obtained.

[0014] In some embodiments of the present application, the volume ratio of alcohol and water in the alcohol-water mixed solution is (0.8-1.2):(0.8-1.2).

[0015] In some embodiments of the present application, the alcohol is ethanol.

[0016] In some embodiments of the present application, the alcohol-water mixed solution is a mixed solution of ethanol and water with a volume ratio of 1:1.

[0017] In some embodiments of the present application, the reducing agent is sodium borohydride (NaBH4). As a strong reducing agent, sodium borohydride is used to reduce Pd(acac)2 to generate Pd nanoparticles, the size of which can be controlled in a small range (3-10 nm) and uniformly distributed, avoiding the agglomeration phenomenon.

[0018] In some embodiments of the present application, the mass ratio of graphene oxide, ethylenediaminetetraacetic acid, palladium acetylacetone, sodium carbonate and sodium borohydride is 15-25:90-110:10-15:90-110:90-110. Under this ratio, the reduction activity, selectivity and stability of the obtained catalyst are high.

[0019] In some embodiments of the present application, the mass ratio of graphene oxide, ethylenediaminetetraacetic acid, palladium acetylacetone, sodium carbonate and sodium borohydride is 20:100:10-15:100:100. Under this ratio, the reduction activity, selectivity and stability of the obtained catalyst are higher.

[0020] In some embodiments of the present application, the mass ratio of graphene oxide, ethylenediaminetetraacetic acid, palladium acetylacetone, sodium carbonate and sodium borohydride is 20:100:11-12:100:100. Under this ratio, the reduction activity, selectivity and stability of the obtained catalyst are the highest.

[0021] The third aspect of the present application provides a graphene supported Pd nanoparticle catalyst or a graphene supported Pd nanoparticle catalyst prepared by the above preparation method for use in electrocatalytic reduction of carbon dioxide.

[0022] The graphene supported Pd nanoparticle catalyst provided by the present application exhibits excellent electrocatalytic reduction performance, can completely inhibit the competitive hydrogen evolution reaction (HER), and can efficiently convert carbon dioxide into carbon monoxide.

[0023] The fourth aspect of the present invention provides a method for electrocatalytic carbon dioxide, wherein a three-electrode system is placed in an electrolyte containing carbon dioxide for electrolysis; the working electrode in the three-electrode system contains the above-mentioned graphene-loaded Pd nanoparticle catalyst or the graphene-loaded Pd nanoparticle catalyst prepared by the above-mentioned preparation method.

[0024] In some embodiments of the present invention, the working electrode further comprises Nafion 117. Specifically, isopropyl alcohol, deionized water, Nafion 117 and the above-mentioned graphene-supported Pd nanoparticle catalyst are mixed in a certain proportion to prepare the working electrode.

[0025] The beneficial effects of the present invention are: The present invention provides a graphene-supported Pd nanoparticle catalyst comprising ethylenediaminetetraacetic acid-modified graphene oxide and palladium nanoparticles; the palladium nanoparticles are supported on the ethylenediaminetetraacetic acid-modified graphene oxide. EDTA is used to modify GO. The addition of EDTA provides coordination sites for anchoring metallic palladium. EDTA functionalization prevents Pd nanoparticle agglomeration and improves the dispersion of Pd nanoparticles. This uniform distribution is crucial for improving catalyst activity and stability. The graphene-supported Pd nanoparticle catalyst provided by the present invention exhibits excellent reduction activity, selectivity, and stability, as well as superior electrocatalytic reduction performance, capable of completely suppressing the Her (HER) reaction and efficiently converting carbon dioxide into carbon monoxide.

[0026] The present invention also provides a preparation method of the graphene-supported Pd nanoparticle catalyst. The graphene-supported Pd nanoparticle catalyst is successfully prepared by a two-step method. EDTA is used to modify GO. The addition of EDTA provides coordination sites for the subsequent anchoring of metal palladium. Pd(acac)2 is added to the GO / EDTA dispersion system, and a reducing agent is added to convert Pd into Pd through an oxidation-reduction reaction. 2+ Reduction to Pd 0 The Pd nanoparticles were uniformly loaded onto EDTA-modified GO to form a graphene-supported Pd nanoparticle catalyst. This catalyst exhibited excellent reduction activity, selectivity, and stability, demonstrating a new approach and possibility for promoting CO₂RR reactions by loading precious metal catalysts onto metal-free functionalized supports. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1Morphology characterization of Pd-GO / EDTA obtained in Example 1 of the present application; wherein, a is a synthesis schematic diagram of Pd-GO / EDTA catalyst, b is SEM of GO, c is SEM of Pd-GO / EDTA, d is SEM of Pd-GO, e is TEM of Pd-GO / EDTA, f is a particle size distribution diagram of Pd-GO / EDTA, and g is HRTEM of Pd-GO / EDTA.

[0029] Figure 2 Comparison of Pd-GO / EDTA obtained in Example 1 of the present application and Pd-GO obtained in Comparative Example 1; wherein, a is XRD pattern of Pd-GO / EDTA, Pd-GO and GO, b is Pd 3d XPS spectrum of Pd-GO / EDTA catalyst, c is Pd 3d XPS spectrum of Pd-GO catalyst, and d is N 1s XPS spectrum of Pd-GO / EDTA catalyst.

[0030] Figure 3 Electrocatalytic reduction activity characterization of Pd-GO / EDTA obtained in Example 1 of the present application; wherein, a is LSV comparison chart of CO2RR in H-type electrolytic cell for Pd-GO / EDTA and Pd-GO electrochemical test in CO2-saturated 0.5 M KHCO3 solution, b is comparison chart of product faradic efficiency of catalyst of CO2RR in H-type electrolytic cell for Pd-GO / EDTA and Pd-GO electrochemical test in CO2-saturated 0.5 M KHCO3 solution, c is LSV comparison chart of CO2RR in flow electrolytic cell for Pd-GO / EDTA and Pd-GO electrochemical test, d is comparison chart of product faradic efficiency of catalyst of CO2RR in flow electrolytic cell for Pd-GO / EDTA and Pd-GO electrochemical test, and e is stability of Pd-GO / EDTA catalyst at-0.8 V potential. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples.

[0032] In the following examples and comparative examples, the raw materials used are all conventional commercially available products, which can be obtained by purchase, unless otherwise specified.

[0033] Among them, the graphene oxide used is prepared by a modified method of Hummers, and the specific preparation method is as follows: The graphite powder is used as raw material, and the graphite powder is layer by layer stripped through oxidation treatment. Sulfuric acid and potassium permanganate are used as main oxidizing agents, ice bath cooling is used to ensure the complete oxidation reaction, the product is uniformly dispersed by ultrasonic, and then centrifugal washing is used to remove the residual acid and impurities, so that a brownish black graphene oxide dispersion liquid is obtained. After drying and weighing, the concentration of GO is calculated as 13.9 mg / mL -1 .

[0034] Example 1 A preparation method of a graphene supported Pd nanoparticle catalyst, comprising the following steps: 20 mg of GO and 0.1 g of EDTA are poured into a mixture of 20 mL of ethanol and 20 mL of water, and dispersed under ultrasonic action for 2 h. Then, 11.4515 mg of Pd(acac)2 is added to the mixture dispersion. After being fully dissolved, 0.1 g of Na2CO3 and 0.1 g of NaBH4 are slowly added, and the mixture is stirred at room temperature for 4 hours. After the reaction is completed, the sample is collected by centrifugation, and freeze-dried at -60°C to obtain a graphene supported Pd nanoparticle catalyst, which is denoted as Pd-GO / EDTA. The mass fraction of Pd in Pd-GO / EDTA is about 20 wt%.

[0035] Comparative Example 1 A preparation method of a graphene supported Pd nanoparticle catalyst, which is different from Example 1 in that EDTA is not added, and the remaining steps are exactly the same as those of Example 1. The obtained sample is denoted as Pd-GO. The mass fraction of Pd in Pd-GO is about 20 wt%.

[0036] As Figure 1 As shown in FIG. a, the Pd-GO / EDTA composite catalyst is successfully prepared by the two-step method in Example 1. The specific synthesis process is as follows. First, GO is synthesized, and EDTA is used to modify GO. The addition of EDTA provides coordination sites for the subsequent anchoring of metal palladium. Pd(acac)2 is added to the GO / EDTA dispersion system, and then a strong reducing agent NaBH4 is added to reduce Pd(acac)2 to Pd nanoparticles. The size of the Pd nanoparticles can be controlled within a small range (3-10 nm), and the distribution is uniform, avoiding the agglomeration phenomenon.

[0037] Further explore the structure of the catalyst, the Pd-GO / EDTA prepared in Example 1, the Pd-GO prepared in Comparative Example 1 and GO are subjected to morphology characterization. First, the GO is subjected to scanning electron microscope test, as Figure 1As shown in FIG. 2b, GO presents a layered structure with wrinkles and irregularities, which is due to the fact that the carbon layers are damaged during the oxidation process and the intercalation of concentrated sulfuric acid during the chemical treatment, resulting in a rough GO surface with many wrinkles and irregular shapes.

[0038] Figure 1 FIG. 2c shows a SEM image of Pd-GO / EDTA obtained by loading Pd nanoparticles on GO / EDTA after functionalization of GO with the metal-free molecule EDTA. As can be seen from the image, GO still presents an irregular layered structure, and the functionalization process did not significantly change the basic morphological characteristics of GO. Although GO / EDTA was subjected to a loading process, no Pd nanoparticles were observed to be present and accumulated. This indicates that the smaller size Pd nanoparticles are distributed on the surface or between the layers of GO / EDTA, and EDTA functionalization can prevent the agglomeration of Pd nanoparticles and improve the dispersibility of Pd nanoparticles.

[0039] The morphology of the Pd-GO control sample without EDTA was characterized, as shown in FIG. 2d. Figure 1 The SEM image of FIG. 2d shows that the surface of Pd-GO is slightly smoother than that of Pd-GO / EDTA, which indicates that EDTA functionalization of the GO surface plays an important role, which can be related to the complexation of EDTA. Pd nanoparticles are obviously accumulated on the surface and between the layers of GO, which indicates that EDTA functionalization helps to improve the dispersibility of Pd nanoparticles, and this uniform distribution is crucial for improving the activity and stability of the catalyst.

[0040] TEM was then used to characterize the morphology of the Pd-GO / EDTA sample. Figure 1 FIG. 2e shows that the Pd-GO / EDTA catalyst presents dispersed Pd nanoparticles, which are uniformly dispersed on GO / EDTA. Fifty Pd nanoparticles were selected for statistical analysis, and the average diameter was about 5.95 nm (FIG. 2f). Figure 1 FIG. 2g is a HRTEM image. Figure 1 The 0.232 nm lattice fringes in the image belong to the (111) plane of Pd. This indicates that there are relatively uniformly dispersed Pd nanoparticles on the surface of Pd-GO / EDTA.

[0041] XRD was used to analyze the crystal structure and phase composition of the material, and the typical diffraction pattern of Pd-GO / EDTA is shown in FIG. 2h. Figure 2The diffraction peaks of Pd-GO / EDTA catalyst around 23.5° were attributed to the (002) diffraction peak after C was reduced by NaBH4, which indicated that GO experienced chemical reduction treatment. A characteristic peak around 11° appeared for GO sample, which was a unique structural feature of GO due to its layered structure. For Pd-GO / EDTA and Pd-GO catalysts, the peak at 40.2° corresponded to the (111) plane of the typical face-centered cubic Pd crystal structure (PDF #87-0638), which indicated that Pd nanoparticles were successfully supported on the GO support and the crystal structure of Pd remained the characteristics of face-centered cubic.

[0042] To further analyze the composition and chemical state of the samples, Figure 2 Fig. b and c are the XPS spectra of Pd 3d of the prepared Pd-GO / EDTA and Pd-GO. Among them, the binding energy at 335.93 eV, 337.82 eV, 341.25 eV and 342.97 eV correspond to Pd 0 3d 5 / 2 , Pd 2+ 3d 5 / 2 , Pd 0 3d 3 / 2 , Pd 2+ 3d 3 / 2 and Pd 0 3d 5 / 2 , respectively. The binding energy of Pd 0 3d 5 / 2 is slightly higher than that at the standard Pd 0 3d 2+ , which indicates that there is a certain electronic interaction between Pd nanoparticles and GO and EDTA, resulting in a decrease in Pd electron cloud density and an increase in binding energy. Pd 2+ mainly corresponds to metallic Pd, and Pd 0 mainly corresponds to oxidized Pd. Since Pd is exposed to air, the surface Pd is oxidized to a small double state with high binding energy, which is assigned to Pd 5 / 2 . The binding energy of Pd-GO is 336.02 eV, 336.72 eV, 341.28 eV and 342.07 eV, which corresponds to Pd 2+ 3d 5 / 2 , Pd 0 3d 3 / 2 , Pd 2+ 3d 3 / 2 , respectively. Compared with Pd-GO / EDTA, the Pd 0 3d 5 / 2The higher binding energy indicates that the interaction between Pd and GO is stronger, resulting in charge transfer. Therefore, in Pd-GO / EDTA, EDTA prevents the agglomeration of Pd nanoparticles and reduces their oxidation degree, while affecting the electronic structure of Pd, making its binding energy slightly lower than that of Pd-GO. In Pd-GO, GO contains more oxygen-containing functional groups (such as -COOH, -OH) that may interact strongly with Pd, resulting in Pd 0 3d 5 / 2 and Pd 0 3d 3 / 2 The binding energy increases, and the addition of EDTA affects the electronic structure of Pd, promoting the electrocatalytic CO2RR. EDTA contains N, and the N 1s spectrum of Pd-GO / EDTA can be decomposed into three peaks ( Figure 2 Figure d) shows the presence of pyridinic N (398.5 eV), pyrrolic N (400.05 eV), and graphitic N (401.75 eV). The presence of graphitic N indicates that the N atoms are successfully doped into the carbon skeleton of graphene, rather than adsorbed on the surface. Pyrrolic N enhances CO₂ adsorption and reduces the free energy of COOH intermediate formation, thereby promoting the electrocatalytic CO₂RR.

[0043] Example 2 A method for electrocatalytic carbon dioxide production, performed in an H-type electrolytic cell, comprising: H-type electrolytic cell: All electrochemical experiments were performed at room temperature using a three-electrode system in a Shanghai Chenhua electrochemical workstation (CHI760e). Regarding the proportion and preparation of the working electrode: the purchased YLS-30T commercial carbon paper was cut into 2.5×1 cm 2 The carbon paper surface was washed with deionized water and ethanol to remove surface impurities and dried in a vacuum oven. 8.0 mg of the catalyst (i.e., Pd-GO / EDTA obtained in Example 1) and 4 mg of XC72 conductive carbon black were placed in a mixture of 1680 μL of isopropanol, 480 μL of H2O, and 240 μL of Nafion 117 (5 wt%) and ultrasonically treated for 30 min. 200 μL of the mixture was dropped onto a 1×1 cm 2 Carbon paper was used as the working electrode for H-type electrolysis cell testing. Electrocatalytic experiments for CO₂RR were conducted in a sealed H-type electrolyzer, with the cathode and anode compartments separated by a Nafion 117 proton exchange membrane. Each cell was filled with 30 mL of 0.5 M KHCO₃ solution (pH 7.2) as the electrolyte. A graphite rod (C) and a saturated Ag / AgCl electrode served as the counter and reference electrodes, respectively. All potentials were referenced to the reversible hydrogen electrode (RHE).

[0044] Before the experiment began, 99.995% pure CO₂ was introduced into the solution until saturated. This process continued for approximately 30 minutes until the pH of the solution stabilized at 7.2 (i.e., a 0.5 M KHCO₃ solution saturated with CO₂). During the electrolysis process, the solutions in both electrolytic cells were stirred. The gas products produced at the cathode were quantitatively analyzed online by gas chromatography. During the electrocatalytic reaction, gas samples were collected three times every three minutes and averaged to determine the gas product content and calculate the Faradaic efficiency. Unless otherwise specified, all potential values ​​in this example are based on the reversible hydrogen electrode (RHE).

[0045] Test potential: Figure 3 The potential of the test corresponding to Figure a is relative to the reversible hydrogen electrode (-0.1 V to -1.0 V). Figure 3 The potential of the test corresponding to Figure b is relative to the reversible hydrogen electrode (-0.5 V to -1.0 V). Figure 3 The potential corresponding to the test in Figure e is relative to the reversible hydrogen electrode (-0.8 V).

[0046] Comparative Example 2 A method for electrocatalyzing carbon dioxide is provided, which differs from Example 2 in that Pd-GO / EDTA is replaced with Pd-GO obtained in Comparative Example 1. The remaining steps are identical to those of Example 2.

[0047] The catalyst was characterized in the electrochemical reduction test of CO2. Pd-GO / EDTA and GO-Pd catalyst materials were prepared into working electrodes with isopropanol, deionized water and Nafion 117 solution in a certain proportion. Preliminary tests were first carried out in an H-type electrolytic cell to evaluate the CO2 electrocatalytic reduction performance of Pd-GO / EDTA and Pd-GO. Due to the high ohmic impedance of the H-type electrolytic cell, the actual applied potential may deviate from the set value, affecting the accuracy of the data. Therefore, 90% ohmic voltage drop compensation was given before the test. The linear sweep voltammetry (LSV) results show that the Pd-GO catalyst has a higher geometric current density and a lower starting potential than Pd-GO / EDTA ( Figure 3 However, the Faradaic efficiency of CO is much lower than that of Pd-GO / EDTA. This is due to the influence of the competitive hydrogen evolution reaction (HER). The reaction kinetics of HER is faster than that of CO2RR. At high current density, more electrical energy is used for hydrogen evolution rather than CO2 reduction. This results in a higher current density of Pd-GO than that of Pd-GO / EDTA, and the electrocatalytic CO2 reduction performance is very poor.

[0048] Compared with Pd-GO, Pd-GO / EDTA exhibits excellent electrocatalytic reduction performance such as Figure 3 As shown in Figure b, the experimental results show that at -0.8 V FECO up to 98.4% and maintained near 100% Faradaic efficiency over a wide potential range (-0.6 V to -0.8 V), which indicates that the catalyst almost completely suppresses the HER and efficiently converts CO2 into CO, with a Faradaic efficiency over 87% at the full potential range tested (-0.5 V to -1.0 V), showing excellent catalytic performance, which indicates that the addition of EDTA promotes the electrocatalytic reduction of CO2 to CO.

[0049] To evaluate the long-term stability of Pd-GO / EDTA in the electrochemical reduction of CO2, long-term electrolysis tests were performed in a H-type electrolysis cell with a constant potential of -0.8 V (Figure Figure 3 , during which CO2 was continuously supplied (flow rate of 20 sccm) to ensure sufficient supply of CO2, and the Pd-GO / EDTA catalyst showed excellent stability, with a CO Faradaic efficiency always maintained above 85% and a slow decay rate, during the continuous electrolysis process for up to 20 h.

[0050] Example 3 A method for electrocatalytic reduction of carbon dioxide, tested using a gas diffusion electrode and a flow cell with continuous flow of electrolyte, comprising: A gas diffusion electrode and a flow cell with continuous flow of electrolyte: carbon paper coated with catalyst (i.e. Pd-GO / EDTA obtained in Example 1) with an area of 2.5 cm 2 , and a catalyst mass loading of 1 mg cm -2 was used as the working electrode in the flow cell, with a solid Ag / AgCl electrode and a platinum sheet as the reference electrode and the counter electrode, and the electrolyte was a 1.0 M KOH solution. During the test, CO2 was directly delivered to the back of the working electrode through the anode chamber (the side without active material), while the electrolyte flowed into the working electrode from the other side. The working electrode and the counter electrode were separated by an anion exchange membrane, and the circulation of the electrolyte was driven by a mobile pump, controlled at 20 mL / min to ensure uniform flow.

[0051] Test potential: Figure 3 The test potential corresponding to Figure c was relative to the reversible hydrogen electrode (-0.1 V to -1.0 V), Figure 3 The test potential corresponding to Figure d was relative to the reversible hydrogen electrode (-0.5 V to -1.0 V).

[0052] Comparative Example 3 A method for electrocatalytic reduction of carbon dioxide, which differs from Example 3 in that Pd-GO / EDTA is replaced by Pd-GO obtained in Comparative Example 1. The remaining steps are exactly the same as those of Example 3.

[0053] Given that Pd-GO / EDTA exhibits excellent CO2 reduction selectivity in the H-type electrolytic cell, in order to further evaluate the catalytic ability and practical application potential at high current density, the study used a gas diffusion electrode and a flow cell with continuous flow electrolyte for testing.

[0054] like Figure 3 As shown in Figure c, the current density values ​​of Pd-GO / EDTA and Pd-GO are significantly higher than those in the H-type electrolyzer, but the current density value of Pd-GO / EDTA is always lower than that of Pd-GO, which is attributed to the effect of HER, which is consistent with the experimental results of the H-type electrolyzer. It is worth noting that the Pd-GO / EDTA catalyst still exhibits excellent CO2 electrocatalytic performance in the flow cell, achieving a CO Faradaic efficiency of 98.4% at a potential of -0.7 V ( Figure 3 The selectivity is close to 100% in the middle d figure. And it maintains an extremely high selectivity of more than 90% throughout the entire test potential range (-0.5 V to -1.0 V). ​ This performance index is significantly better than that of most reported Pd-based catalysts, demonstrating excellent electrochemical CO2 reduction performance.

[0055] Example 4 A method for preparing a graphene-supported Pd nanoparticle catalyst is different from Example 1 in that the amount of Pd(acac)2 added is 10 mg, and the remaining steps are exactly the same as those of Example 1.

[0056] Example 5 A method for preparing a graphene-supported Pd nanoparticle catalyst is different from Example 1 in that the amount of Pd(acac)2 added is 11 mg, and the remaining steps are exactly the same as those in Example 1.

[0057] Example 6 A method for preparing a graphene-supported Pd nanoparticle catalyst is different from Example 1 in that the amount of Pd(acac)2 added is 12 mg, and the remaining steps are exactly the same as those of Example 1.

[0058] Example 7 A method for preparing a graphene-supported Pd nanoparticle catalyst is different from Example 1 in that the amount of Pd(acac)2 added is 15 mg, and the remaining steps are exactly the same as those in Example 1.

[0059] Example 8 A method for preparing a graphene-supported Pd nanoparticle catalyst, which differs from Example 1 in that the ethanol-water mixed solution is a mixture of 10 mL of ethanol and 10 mL of water. The remaining steps are identical to those of Example 1.

[0060] Example 9 A preparation method of a graphene supported Pd nanoparticle catalyst, which is different from that of Example 1 in that the ethanol and water mixed solution is a mixed solution of 100 mL of ethanol and 100 mL of water. The remaining steps are completely consistent with those of Example 1.

[0061] It is detected that the graphene supported Pd nanoparticle catalysts obtained in Examples 4-9 have similar morphology to that of the Pd-GO / EDTA obtained in Example 1, the particle size of the palladium nanoparticles is small and uniformly supported on the GO / EDTA, the carbon dioxide reduction activity is high, and the graphene supported Pd nanoparticle catalysts have excellent electrocatalytic activity, selectivity and stability.

[0062] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A graphene-supported Pd nanoparticle catalyst, characterized in that: including ethylenediaminetetraacetic acid-modified graphene oxide and palladium nanoparticles; The palladium nanoparticles are supported on the ethylenediaminetetraacetic acid-modified graphene oxide.

2. A graphene-supported Pd nanoparticle catalyst according to claim 1, characterized in that: The particle size of the palladium nanoparticles is 3-10 nm, and the loading amount is 10-30 wt%.

3. A method for preparing a graphene-supported Pd nanoparticle catalyst according to claim 1 or 2, characterized in that: include: Graphene oxide and ethylenediaminetetraacetic acid are dissolved in an alcohol-water mixed solution, ultrasonicated, and then palladium acetylacetonate is added. After dissolution, sodium carbonate and a reducing agent are added, stirred, centrifuged, and freeze-dried to obtain a graphene-supported Pd nanoparticle catalyst.

4. The preparation method according to claim 3, wherein In the alcohol-water mixed solution, the concentration of graphene oxide is 0.1-1 mg / mL.

5. The preparation method according to claim 3, wherein The volume ratio of alcohol to water in the alcohol-water mixed solution is (0.8-1.2):(0.8-1.2); Preferably, the alcohol is ethanol; Further preferably, the alcohol-water mixed solution is a mixed solution of ethanol and water in a volume ratio of 1:

1.

6. The preparation method according to claim 3, wherein The reducing agent is sodium borohydride.

7. The preparation method according to claim 5, wherein The mass ratio of graphene oxide, ethylenediaminetetraacetic acid, palladium acetylacetonate, sodium carbonate and sodium borohydride is 15-25:90-110:10-15:90-110:90-110; Preferably, the mass ratio of graphene oxide, ethylenediaminetetraacetic acid, palladium acetylacetonate, sodium carbonate and sodium borohydride is 20:100:10-15:100:100; Preferably, the mass ratio of graphene oxide, ethylenediaminetetraacetic acid, palladium acetylacetonate, sodium carbonate and sodium borohydride is 20:100:11-12:100:

100.

8. Use of a graphene-supported Pd nanoparticle catalyst according to claim 1 or 2 or a graphene-supported Pd nanoparticle catalyst prepared by the preparation method according to any one of claims 3 to 7 in electrocatalysis of carbon dioxide.

9. A method for electrocatalytic carbon dioxide production, characterized in that: The three-electrode system is placed in an electrolyte containing carbon dioxide for electrolysis; the working electrode in the three-electrode system contains a graphene-supported Pd nanoparticle catalyst according to claim 1 or 2 or a graphene-supported Pd nanoparticle catalyst prepared by the preparation method according to any one of claims 3-7.

10. The method according to claim 9, wherein The working electrode further comprises Nafion 117.

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