Ni-cu single-atom catalysts, methods of making and using the same

Abstract

The application belongs to the technical field of electrocatalytic materials, and specifically discloses a Ni-Cu double monatomic catalyst, a preparation method and application thereof, the catalyst is a carbon carrier uniformly dispersed with Ni and Cu monatomic sites, an adjacent structure with an average interval of 4.1 angstroms is formed between the Ni and the Cu, the Ni site is a main catalytic site, and the Cu site is an auxiliary site. Compared with a traditional Ni monatomic catalyst, the Ni-Cu double monatomic catalyst of the application has a significant improvement in current density, CO selectivity and stability; through specific adsorption of water molecules by the Cu site, the rigidity of the interface hydrogen bond network is weakened, the CO2 protonation process is accelerated, and the reaction kinetics is improved. By constructing adjacent Ni-Cu collaborative sites, the interface water structure is regulated, the CO2 protonation efficiency is improved, and the CO2 electro-reduction under high selectivity and high current density is realized.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, and in particular to Ni-Cu dual single-atom catalysts, their preparation methods, and applications. Background Technology

[0002] Electrocatalytic carbon dioxide reduction (ECO2RR) is a green energy technology that converts CO2 into high-value-added chemicals and fuels, contributing to carbon recycling. Currently, single-atom catalysts (SACs) have become a research hotspot in ECO2RR due to their high activity, high selectivity, and structural tunability. However, traditional single-atom catalysts (such as NiSACs) suffer from slow reaction kinetics, high onset potential, and low current density in the CO2-to-CO reduction process, limiting their application at industrial-scale current densities.

[0003] In recent years, heteronuclear dual single-atom catalysts (DSACs) have shown potential in improving catalytic performance due to the synergistic effect between adjacent sites. However, the synergistic mechanism between the "main" and "auxiliary" sites in heteronuclear dual single-atom catalysts remains unclear in current technologies, especially in terms of regulating the interfacial water structure and promoting CO2 protonation kinetics. Summary of the Invention

[0004] The purpose of this invention is to provide a Ni-Cu dual single-atom catalyst, its preparation method, and its applications. By constructing adjacent Ni-Cu synergistic sites and regulating the interfacial water structure, the CO2 protonation efficiency is improved, achieving CO2 electroreduction with high selectivity and high current density. This addresses the problems of slow reaction kinetics, low current density, and poor stability of existing Ni-based single-atom catalysts in ECO2RR.

[0005] To achieve the above objectives, the present invention provides a Ni-Cu dual single-atom catalyst, wherein the catalyst consists of uniformly dispersed Ni and Cu single-atom sites on a carbon support, and Ni and Cu form a neighboring structure with an average spacing of 4.1 Å. The Ni site is the main catalytic site, and the Cu site is the auxiliary site.

[0006] Preferably, Ni and Cu exist in coordination structures of Cl-Ni-C3 and Cl-Cu-C3, respectively.

[0007] Preferably, the catalyst is prepared by molten salt-assisted pyrolysis, in which agarose is used as the carbon source and ZnCl2 / NaCl is used as the binary molten salt.

[0008] Preferably, the catalyst can achieve ≥200 mA / cm² under both pH=1 and pH=13 conditions. 2 It has industrial-grade current density and CO selectivity of 90%-100%.

[0009] Preferably, the catalyst exhibits excellent stability in membrane electrode assemblies or flow electrolyzers, with CO selectivity decreasing by less than 10% after 150-170 hours of continuous operation.

[0010] This invention also provides a method for preparing a Ni-Cu dual single-atom catalyst, comprising the following steps: Step 1: Dissolve Ni(NO3)2 and Cu(NO3)2 in an aqueous solution containing agarose and stir until homogeneous; Step 2: Add ZnCl2 / NaCl binary molten salt, and dry to form a gel; Step 3: High-temperature pyrolysis under an inert atmosphere to obtain carbon-supported Ni-Cu dual single-atom catalyst.

[0011] Preferably, in step 3, the temperature of the high-temperature heat connection is 800-900℃.

[0012] This invention also provides the application of Ni-Cu dual single-atom catalysts in electrocatalytic CO2 reduction reactions, which regulate the interfacial water structure, improve CO2 protonation efficiency, and achieve CO2 electroreduction with high selectivity and high current density.

[0013] The advantages and beneficial effects of the present invention using the above-mentioned Ni-Cu dual single-atom catalyst, its preparation method, and its application are as follows: 1. This invention improves CO2 protonation efficiency by constructing adjacent Ni-Cu synergistic sites and regulating the interfacial water structure, thereby achieving high selectivity and high current density CO2 electroreduction. This solves the problems of slow reaction kinetics, low current density, and poor stability of existing Ni-based single-atom catalysts in ECO2RR.

[0014] 2. Compared with traditional Ni single-atom catalysts, the Ni-Cu dual single-atom catalyst of the present invention significantly improves current density, CO selectivity and stability; by specifically adsorbing water molecules at Cu sites, the rigidity of the interfacial hydrogen bond network is weakened, the protonation process of CO2 is accelerated, and the reaction kinetics are improved.

[0015] 3. The catalyst of this invention achieves a single-pass carbon efficiency (SPCE) of up to 67.3% under strong acid conditions, which is superior to the existing technology; it is applicable to various electrolysis systems such as H-type electrolyzers, flow electrolyzers and membrane electrode assemblies (MEAs), and has good prospects for industrial application.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 These are HAADF-STEM images of the Cl-Ni1Cu1-C catalyst of this invention; Figure 2 (a) shows the FT-EXAFS spectra of Ni foil, NiO, NiPc, Cl-Ni1-C and Cl-Ni1Cu1-C at the NiK edge; (b) shows the FT-EXAFS spectra of Cu foil, CuO, CuPc, Cl-Cu1-C and Cl-Ni1Cu1-C at the CuK edge. Figure 3 In Figure 'a', LSV curves of Cl-Cu1-C, Cl-Ni1-C, and Cl-Ni1Cu1-C under CO2 atmosphere are shown, with a scan rate of 10 mV / s. -1 b represents the jCOs of Cl-Cu1-C, Cl-Ni1-C, and Cl-Ni1Cu1-C at different potentials; Figure 4 The present invention is Cl-Ni1Cu1-C in a strong acid (j=200mAcm). -2 The long-term stability test chart is shown in the figure. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0020] The following examples are not intended to limit the invention, but are only for illustration. Unless otherwise specified, the experimental methods used in the following examples are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0021] Example 1 The Ni-Cu dual single-atom catalyst consists of uniformly dispersed Ni and Cu single-atom sites on a carbon support, forming a proximity structure with an average spacing of 4.1 Å between Ni and Cu. Ni sites are the primary catalytic sites, while Cu sites are auxiliary sites. Ni and Cu exist in Cl-Ni-C3 and Cl-Cu-C3 coordination structures, respectively. The catalyst is prepared via molten salt-assisted pyrolysis, using agarose as the carbon source and ZnCl2 / NaCl as the binary molten salt. The catalyst achieves ≥200 mA / cm² under both pH=1 and pH=13 conditions. 2 It achieves industrial-grade current density with CO selectivity approaching 100%. The catalyst exhibits excellent stability in membrane electrode assemblies or flow electrolyzers, with CO selectivity decreasing by less than 10% after 150-170 hours of continuous operation.

[0022] Example 2 The preparation method of Ni-Cu dual single-atom catalyst includes the following steps: Step 1: Dissolve Ni(NO3)2 and Cu(NO3)2 in an aqueous solution containing agarose and stir until homogeneous; Step 2: Add ZnCl2 / NaCl binary molten salt, and dry to form a gel; Step 3: High-temperature pyrolysis (800-900℃) under an inert atmosphere to obtain carbon-supported Ni-Cu dual single-atom catalyst Cl-Ni1Cu1-C.

[0023] Step 4: Ni and Cu were confirmed to exist in single-atom form with a spacing of approximately 4.1 Å by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption spectroscopy (XAS).

[0024] This catalyst exhibits excellent performance in the electrocatalytic CO2 reduction reaction, achieving ≥200 mAcm under both strong acid (pH=1) and strong base (pH=13) conditions. -2 It has an industrial-grade current density, near 100% CO selectivity, and long-term stability of 150–170 hours.

[0025] Example 3 The ECO2RR performance of the catalyst in Example 1 was tested (H-type electrolyzer).

[0026] Electrolyte: 0.5 MkHCO3.

[0027] Potential range: -0.4V to -1.0V (vs. RHE).

[0028] The CO portion current density of Cl-Ni1Cu1-C at -1.0V is -58.3 mA / cm². -2 It is 1.5 times that of NiSAC and 15 times that of CuSAC.

[0029] CO selectivity (FE_CO) is above 90% in the range of -0.5V to -1.0V.

[0030] Example 4 The catalyst of Example 1 was subjected to industrial-grade current density testing (flow electrolysis cell).

[0031] Acidic conditions (pH=1): at 200 mAcm -2 Below, FE_CO>95%, SPCE_CO reaches 67.3%.

[0032] Under alkaline conditions (pH=13): FE_CO>95%, EE reaches 61.1%.

[0033] Stability test: 170h continuous electrolysis, FE_CO decay <10%.

[0034] Example 5 The catalyst of Example 1 was tested using an MEA electrolysis system.

[0035] At 200mAcm -2 At this point, E_cell was 2.68V, FE_CO was 96.5%, and EE was 48%; during the 150h stability test, FE_CO decayed by only 7.7%.

[0036] Figure 1 This is a HAADF-STEM image of the Cl-Ni1Cu1-C catalyst. Figure 1 In the high-resolution HAADF-STEM images, isolated bright spots are attributed to Ni / Cu single atoms. Notably, due to the co-anchoring of Ni and Cu single atoms, the density of single-atom sites in Cl-Ni1Cu1-C is higher than that in Cl-Ni1-C and Cl-Cu1-C, which creates opportunities for the formation of more adjacent Ni-Cu sites.

[0037] Figure 2 The localized coordination structures of single-atom sites in these three catalysts were confirmed using Fourier transform extended X-ray absorption fine structure (FT-EXAFS) spectroscopy. Figure 2 (b) In the FT-EXAFS spectrum of Ni foil, the main peak is located at ~2.19 Å, attributed to the N-Ni bond. For NiO, the two peaks representing Ni-O and Ni-O-Ni bonds are located at ~1.65 Å and ~2.60 Å, respectively. In the FT-EXAFS spectrum of NiPc, the main peak at ~1.49 Å is attributed to the Ni-N bond.

[0038] In FT-EXAFS spectroscopy ( Figure 2 In b), the main peak of Cu foil is located at ~2.24 Å, representing Cu-Cu bonds. For CuO, two distinct peaks are located at ~1.55 Å and ~2.50 Å, belonging to Cu-O and Cu-O-Cu bonds, respectively. In the FT-EXAFS spectrum of CuPc, the prominent peak representing Cu-N bonds is located at ~1.56 Å. For Cl-Cu1-C and Cl-Ni1Cu1-C, the main peak is located at ~1.48 Å, belonging to Cu-C / Cl bonds.

[0039] Figure 3Figure 'a' shows the linear sweep voltammetry (LSV) curve obtained in a CO2-saturated KHCO3 electrolyte. Clearly, compared to Cl-Ni1-C and Cl-Cu1-C, Cl-Ni1Cu1-C exhibits a higher polarization current density in the potential range of -0.4 to -1.1 V (relative to the reversible hydrogen electrode, vs. RHE), indicating that Cl-Ni1Cu1-C possesses higher electrocatalytic activity for CO2RR or the competing hydrogen evolution reaction (HER). Figure 3 Figure b shows that the proximity effect of the Ni-Cu double single-atom sites leads to an optimized jCO of -58.3 mA cm⁻¹ for Cl-Ni1Cu1-C at -1.0 V vs. RHE. -2 It is almost 1.5 times that of Cl-Ni1-C and 15 times that of Cl-Cu1-C. Figure 4 Long-term stability tests verified the stability of Ni1Co1NC in the continuous production of syngas with a CO / H2 ratio of approximately 1:1.

[0040] Therefore, this invention employs the aforementioned Ni-Cu dual single-atom catalyst, its preparation method, and its application. By constructing adjacent Ni-Cu synergistic sites and regulating the interfacial water structure, it enhances CO2 protonation efficiency, achieving high selectivity and high current density CO2 electroreduction. This solves the problems of slow reaction kinetics, low current density, and poor stability of existing Ni-based single-atom catalysts in ECO2RR.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A Ni-Cu dual single-atom catalyst, characterized in that: The catalyst consists of uniformly dispersed Ni and Cu single-atom sites on a carbon support, with Ni and Cu forming a neighboring structure with an average spacing of 4.1 Å. Ni sites are the main catalytic sites, and Cu sites are auxiliary sites. Ni and Cu exist in coordination structures of Cl-Ni-C3 and Cl-Cu-C3, respectively; The Ni-Cu dual single-atom catalyst was prepared by molten salt-assisted pyrolysis, including the following steps: Step 1: Dissolve Ni(NO3)2 and Cu(NO3)2 in an aqueous solution containing agarose and stir until homogeneous; Step 2: Add ZnCl2 / NaCl binary molten salt, and dry to form a gel; Step 3: High-temperature pyrolysis under an inert atmosphere, at a temperature of 800-900℃, yields carbon-supported Ni-Cu dual single-atom catalyst.

2. The Ni-Cu dual single-atom catalyst according to claim 1, characterized in that: The catalyst can achieve ≥200 mA / cm at both pH=1 and pH=13. 2 It has industrial-grade current density and CO selectivity of 90%-100%.

3. The Ni-Cu dual single-atom catalyst according to claim 1, characterized in that: The catalyst exhibits excellent stability in membrane electrode assemblies or flow electrolyzers, with CO selectivity decay of less than 10% after 150-170 hours of continuous operation.

4. The application of the Ni-Cu dual single-atom catalyst according to any one of claims 1-3, characterized in that: It is applied to the electrocatalytic CO2 reduction reaction to regulate the interfacial water structure, improve the CO2 protonation efficiency, and achieve CO2 electroreduction with high selectivity and high current density.

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