Method for achieving efficient electro-catalysis hydrogen production reaction by selectively adsorbing methyl blue molecules on surface of catalyst

Abstract

The invention relates to a method for selectively adsorbing methyl blue molecules on the surface of a catalyst to achieve an efficient electro-catalytic hydrogen production reaction, in particular to an efficient electro-catalytic hydrogen production system synthesized through pi-pi interaction of methyl blue and Pt / rGO (redox graphene oxide), and belongs to the technical field of catalytic energy. Methyl blue (MB) molecules are used, and Pi-Pi interaction exists between MB and rGO. Under the application of external voltage, the Pi-Pi interaction between MB and rGO can lead to high catalytic activity in electro-catalytic hydrogen production (HER). By replacing other molecules with similar structures, the catalytic performance of electro-catalytic hydrogen evolution can also be regulated and controlled. The smooth implementation of the patent provides a universal, simple, convenient and efficient strategy for regulating and controlling the efficiency of the electro-catalytic hydrogen production reaction, solves the problem of unstable structure of the previous system, and provides greater possibility for industrialization in the field of electro-catalytic hydrogen production.

Description

TECHNICAL FIELD

[0001] The application relates to a method for selectively adsorbing methyl blue molecules on the surface of a catalyst to achieve a high-efficiency electrocatalytic hydrogen production reaction, in particular to a high-efficiency electrocatalytic hydrogen production system synthesized by the pi-pi interaction between methyl blue and Pt / rGO, and belongs to the technical field of catalytic energy. BACKGROUND

[0002] Hydrogen energy is considered as a potential alternative to traditional fossil fuels due to its high energy density, abundant resources and environmental friendliness. Electrochemical water splitting is a potential industrial hydrogen production strategy, which has attracted much attention due to its high efficiency, safe equipment and abundant water resources. However, the electrochemical decomposition of water molecules usually needs to overcome a high energy barrier, which limits the reaction efficiency. On the surface of some catalysts (usually transition metals or their composites), this high energy barrier can be reduced. At present, a variety of high-efficiency electrocatalytic hydrogen evolution reaction catalysts have been developed, among which the heterostructure catalyst has unique advantages. First, the interface between different components can form an interface electric field, which helps to promote electron transmission and thus improve the electrocatalytic performance. In addition, there may be a strong synergistic effect between the active sites in different components, thereby improving the reaction kinetics. Compared with single-component catalysts, catalysts based on heterostructures usually exhibit higher catalytic activity and / or selectivity. However, the synthesis of these heterostructures is usually complex and challenging. In recent years, the method of regulating reaction activity and selectivity by physically or chemically adsorbing specific molecules on the surface of catalysts has been proven to be effective. For example, mercaptan molecules adsorbed on the surface of platinum nanoparticles can significantly promote the electrocatalytic hydrogen evolution reaction. Pyridine molecules containing thiol groups are adsorbed on the surface of copper catalysts through copper-sulfur bonds, which can promote the formation of formic acid in the carbon dioxide reduction reaction (CO2RR) by weakening the binding of intermediates to the copper surface. In acidic conditions, amine molecules form coordination bonds with copper atoms to adsorb on the surface of copper, which can improve the selectivity of C 2+ products because amine molecules help to increase the surface coverage of CO intermediates. Other molecules (such as amines) also adjust the electronic structure by adsorbing on the surface of copper catalysts, thereby changing the selectivity and activity in CO2RR. Although certain molecules can improve reaction activity and selectivity by adsorbing on the surface of metal catalysts, direct adsorption of these molecules may block the catalytically active sites, limiting the improvement of catalytic effect. Therefore, it is necessary to improve the molecular adsorption strategy to achieve the improvement of catalytic activity without occupying the active sites.

[0003] Herein, the present application improves the electrocatalytic performance of Pt / rGO by a simple and convenient solution method to adsorb MB on the surface of Pt / rGO nanocomposites (Pt / rGO-MB). The MB molecules are selectively adsorbed on the surface of rGO, which improves the interface charge transfer. The results show that the prepared catalyst exhibits higher catalytic activity in the electrocatalytic hydrogen evolution reaction. Through experimental and simulation results, the mechanism of this catalytic enhancement is systematically studied. In addition, this catalytic enhancement strategy can be applied to various catalytic systems. SUMMARY

[0004] The technical problem solved by the present application is a method for selectively adsorbing methyl blue molecules on the surface of a catalyst to achieve efficient electrocatalytic hydrogen evolution reaction. After MB modification, the output current density at-0.6V(vs.RHE) potential is increased by 1.5 times, reaching-195mA·cm -2 ; 10mA·cm -2 The overpotential corresponding to the current density is optimized from-0.109V to-0.084V(vs.RHE). Through systematic electrochemical tests and theoretical calculations, the improvement of interface charge transfer efficiency is confirmed. This study provides a simple and efficient method for optimizing HER electrocatalytic performance, and this strategy can be conveniently expanded to other catalytic systems.

[0005] To solve the above technical problems, the technical solution proposed by the present application is a method for selectively adsorbing methyl blue molecules on the surface of a catalyst to achieve efficient electrocatalytic hydrogen evolution reaction. The methyl blue molecules are selectively adsorbed on the surface of reduced graphene oxide by π-π interaction, and platinum nanoparticles are uniformly dispersed on the support to form a Pt / rGO-MB catalyst. 0.1mL of 1mg / mL Pt / rGO-MB dispersion is uniformly coated on the surface of carbon paper, and the catalyst is dried at 60-100℃ for 30-60 minutes. The catalyst loading is 0.1mg / cm 2 , and the electrocatalytic hydrogen production experiment is carried out in a three-electrode system using an electrochemical workstation with additional potential.

[0006] Preferably, the preparation process of Pt / rGO is as follows: Pt / rGO composite is synthesized by seed-mediated method. The specific steps are as follows: first, 24mg of PtCl2 is dispersed in 20mL of ethylene glycol, and uniform dispersion is obtained by continuous stirring for 30 minutes; then 45mL of 2mg·mL-1 graphene oxide (GO) dispersion is added to the solution, and stirring is continued at room temperature for 2 hours. The mixed solution is heated to 120℃ and stirred vigorously for 25 minutes to obtain Pt / rGO composite. The obtained black solid is dispersed in 90mL of N,N-dimethylformamide (DMF) for standby.

[0007] Preferably, the preparation process of Pt / rGO-MB: 3 mL of MB solution with a concentration of 1 mg·mL-1 is mixed with 1 mL of Pt / rGO dispersion, and is left to stand for more than 12 hours to ensure sufficient adsorption. Then, the unadsorbed MB molecules are removed by multiple centrifugal washing, and finally the purified Pt / rGO-MB composite is redispersed in 90 mL of DMF.

[0008] Preferably, the process of the electrocatalytic hydrogen production experiment is as follows: the above-mentioned DMF-dispersed Pt / rGO-MB suspension is drop-coated on carbon paper to form a working electrode of a three-electrode electrochemical system. The specific operation is as follows: 0.1 mL of the Pt / rGO-MB suspension is uniformly drop-coated on the surface of 10*20 mm 2 of carbon paper, and then is placed on a hot plate at 100 DEG C for drying for more than 30 minutes. Platinum is used as the counter electrode, an Ag|AgCl electrode (immersed in saturated KCl solution) is used as the reference electrode, and the electrolyte is 0.5 M H2SO4 solution. All the electrochemical tests are performed on a CHI 630E electrochemical workstation (CH Instruments).

[0009] The beneficial effects of the present application are as follows:

[0010] 1. The MB modification significantly optimizes the interface electronic structure and charge transfer efficiency: the MB molecules are selectively adsorbed on the surface of rGO through π-π interaction to form an electron delocalization channel, which significantly reduces the interface charge transfer resistance (R ct from 1738 Ω to 831 Ω) and regulates the double-layer microenvironment to promote proton transport. At the same time, the conjugated structure of MB enhances the electron density distribution on the surface of the catalyst, and the hydrogen adsorption free energy (ΔG *H ) is optimized from -0.372 eV to -0.198 eV, thereby improving the hydrogen evolution reaction kinetics.

[0011] 2. The preparation process is simple and low in cost: the present application adopts a simple solution mixing and centrifugal step, without the need for high temperature, high pressure or complex equipment, and the amount of MB molecules is only 0.3-1% of the mass of the catalyst. The method can be produced on a large scale, is suitable for roll-to-roll coating technology, meets the needs of industrial electrolytic cells, and has significant economic efficiency and practical application potential.

[0012] 3. High and stable electrocatalytic performance: the current density of Pt / rGO-MB in 0.5 M H2SO4 is 195 mA·cm-2 (-0.6 V vs. RHE), which is 1.5 times higher than that of the unmodified sample; the overpotential at 10 mA·cm-2 is reduced from 109 mV to 84 mV. In addition, the current density retention rate is more than 90% after continuous operation for 100 hours, and the catalyst morphology and structure do not change significantly, which shows excellent long-term stability.

[0013] 4. Broad applicability and universality: This strategy can be extended to various molecules (such as fluorescein) and carrier systems (such as Au / rGO) and photocatalytic hydrogen evolution systems. BRIEF DESCRIPTION OF DRAWINGS

[0014] The application will be further described below with reference to the drawings.

[0015] Figure 1 is a schematic diagram of the efficient electrocatalytic hydrogen evolution of Pt / rGO-MB.

[0016] Figure 2 is structural characterization. (a) TEM image of Pt / rGO-MB. (b) Raman spectra of Pt / rGO, MB and Pt / rGO-MB. (c-f) XPS N 1s, C 1s, O 1s and Pt 4f spectra of Pt / rGO and Pt / rGO-MB

[0017] Figure 3 is electrocatalytic activity and stability. (a) LSV curves of Pt / rGO and Pt / rGO-MB in 0.5 M H2SO4. (b) Overpotential of Pt / rGO and Pt / rGO-MB at 10 mA·cm -2 and 50 mA·cm -2 (c) Tafel slope of Pt / rGO and Pt / rGO-MB. (d) ESCAs curves of Pt / rGO and Pt / rGO-MB. e) Comparison of catalytic performance of Pt / C before and after MB adsorption. (f-g) EIS spectra of Pt / rGO and Pt / rGO-MB at 0 V and -0.05 V. (h) Electro-catalytic stability of Pt / rGO-MB.

[0018] Figure 4 Factors affecting the enhancement of HER on Pt / rGO-MB. (a-b) Effect of MB:Pt / rGO mass ratio on catalytic performance. (c-d) LSV curves of Pt / rGO and Pt / rGO-MB at different pH values. (e) Output current ratio of Pt / rGO-MB to Pt / rGO at different pH values. (f) Protonation and deprotonation scheme of MB.

[0019] Figure 5The electrocatalytic HER was regulated by selecting different molecules and this strategy was utilized in other catalytic systems. (a) Molecular structures of methyl violet (MV), nile blue (NB), rhodamine 110 (Rh110) and fluorescein (FL). (b) LSV curves of electrocatalytic HER in the presence of various molecules. (c) EIS spectra of Pr / rGO with adsorption of various molecules. (d) Enhancement of electrocatalytic HER on Au / rGO by surface adsorption of MB molecules. (e) EIS spectra of Au / rGO and Au / rGO-MB at -0.05 V vs. RHE. DETAILED DESCRIPTION

[0020] Example 1

[0021] Pt / rGO composite was synthesized by a seed-mediated method. The specific steps are as follows: first, 24 mg of PtCl2was dispersed in 20 mL of ethylene glycol, and the solution was continuously stirred for 30 minutes to obtain a uniformly dispersed solution; then 45 mL of graphene oxide (GO) dispersion solution with a concentration of 2 mg·mL-1was added to the solution, and the stirring was continued at room temperature for 2 hours. The mixed solution was heated to 120°C and strongly stirred for 25 minutes to finally obtain the Pt / rGO composite. The obtained product was washed with ethanol and deionized water alternately for three times, and then the obtained black solid was dispersed in 90 mL of N,N-dimethylformamide (DMF) for standby.

[0022] Preparation process of Pt / rGO-MB: 3 mL of MB solution with a concentration of 1 mg·mL-1was mixed with 1 mL of Pt / rGO dispersion solution, and it was left to stand for more than 12 hours to ensure sufficient adsorption. Then, the unadsorbed MB molecules were removed by washing through centrifugation for several times, and finally the purified Pt / rGO-MB composite was redispersed in 90 mL of DMF.

[0023] The process of our electrocatalytic hydrogen production experiment is as follows:

[0024] The above Pt / rGO-MB suspension dispersed in DMF was drop-coated on carbon paper and used as the working electrode of a three-electrode electrochemical cell. The specific steps are as follows: 0.1 mL of Pt / rGO-MB suspension was evenly drop-coated on a 10×20 mm 2 carbon paper, and then the carbon paper was placed on a hot stage at 100°C for drying for more than 30 minutes. In the experiment, platinum sheet and Ag|AgCl (stored in saturated KCl solution) were used as the counter electrode and reference electrode, respectively, and the electrolyte was 0.5 M H2SO4. The electrochemical test was completed on an electrochemical workstation (CHI630E, CH Instrument), and all potential values were converted to the reversible hydrogen electrode (RHE) scale. In order to explore the influence of pH value, three kinds of electrolytes were used in the experiment: 0.5 M H2SO4, 1 M NaOH and 1 M PBS.

[0025] As Figure 1 is a schematic diagram of Pt / rGO-MB promoting electrochemical hydrogen evolution.

[0026] As Figure 2 is the structural characterization of Pt / rGO-MB. First, we characterized the obtained Pt / rGO-MB catalyst by TEM, Raman spectra, and XPS spectra. Through scanning transmission electron microscopy images, this aggregation has been successfully observed. Using Raman spectroscopy, it was shown that MB molecules were uniformly adsorbed on the surface of Pt / rGO. Then, photoluminescence spectroscopy measurements were performed to study the interaction between Pt / rGO and MB molecules. We further investigated the interaction between MB and Pt / rGO by X-ray photoelectron spectroscopy (XPS) tests. The appearance of the XPS N 1s spectrum peak and the change of the O 1s spectrum peak in the Pt / rGO-MB composite sample indicate that MB molecules are adsorbed on the surface of Pt / rGO, which is attributed to the fact that MB molecules themselves contain N and O atoms. Among them, the XPS peaks located at 532.1 eV and 533.6 eV correspond to C-O and C-OH bonds, respectively. When the Pt / rGO sample adsorbs MB molecules, the relative intensity of C-OH is enhanced, which may be the result of the presence of MB molecules. In addition, we further explored the interaction between MB and Pt / rGO by analyzing the XPS Pt 4f spectrum of the sample. Compared with the original Pt / rGO without adsorbing MB, there is no obvious peak shift in the sample after adsorbing MB, which indicates that the interaction between Pt and MB is weak. In other words, MB molecules tend to be adsorbed on the surface of rGO sheets rather than on the surface of Pt nanoparticles.

[0027] As Figure 3 shown, the catalytic activity of MB-adsorbed Pt / rGO in electrocatalytic HER in 0.5 M sulfuric acid (H2SO4) solution is improved compared with bare Pt / rGO. The linear sweep voltammetry (LSV) curve of Pt / rGO-MB is significantly lower than that of bare Pt / rGO, indicating that the electrocatalytic HER on MB-adsorbed Pt / rGO is promoted. Further comparison of the overpotential of these two samples, the overpotential of bare Pt / rGO is 109 mV at a current density of 10 mA·cm -2 , while the overpotential of Pt / rGO-MB is significantly reduced to 84 mV. Similar results are observed at a higher current density of 50 mA·cm -2 , where the overpotential on Pt / rGO is reduced from 270 mV to 210 mV after the adsorption of MB molecules. These results show that the simple molecular adsorption of MB on Pt / rGO can lead to a significant increase in the catalytic activity of HER.

[0028] Comparative Example 1

[0029] The amount of MB molecules significantly affects the electrocatalytic hydrogen evolution performance. To verify the role of MB molecules, we performed the following experiments, as shown in Figure 4 We investigated the contribution of MB:Pt / rGO ratio to the obtained catalytic enhancement. As the MB:Pt / rGO mass ratio increased from 0 to 3:1, the electrocatalytic activity of Pt / rGO-MB continuously improved. The output current at -0.8 V increased from -0.19 to -0.28 A cm -2 , an increase of 47%. These results indicate that MB adsorption has a great contribution to the catalytic enhancement of Pt / rGO composites. Further increasing the MB:Pt / rGO mass ratio from 3:1 to 9:1 led to a decrease in the output current to -0.23 A cm -2 . This decrease can be attributed to the blocking of catalytically active sites due to the presence of excess MB molecules. Therefore, the optimal catalytic enhancement was obtained at a MB:Pt / rGO mass ratio of 3:1.

[0030] Comparative Example 2

[0031] The molecular adsorption strategy presented in this work can be fine-tuned by changing the selected molecules, such as methyl violet, nile blue, rhodamine 110, and fluorescein. These molecules all have conjugated structures, and their functional groups are different. Their contributions to the catalytic enhancement of electrocatalytic HER were compared. As shown in Figure 5 Fluorescein was observed to significantly promote the electrocatalytic HER performance of Pt / rGO, while methyl violet and nile blue exhibited inhibitory effects. Apparently, similar to MB molecules, fluorescein molecules are also easily protonated to carry a negative charge in solution. Therefore, this property of MB and fluorescein molecules greatly contributes to the enhancement of Pt / rGO electrocatalytic HER. Similarly, fluorescein-adsorbed Pt / rGO also has a significantly reduced interfacial charge transfer resistance.

[0032] The present application is not limited to the specific technical solutions described in the above examples, and any technical solution formed by equivalent substitution is within the scope of protection required by the present application.

Claims

1. A method for selectively adsorbing methylene blue molecules onto the surface of a catalyst to achieve a highly efficient electrocatalytic hydrogen production reaction, characterized in that: Methylene blue molecules are selectively adsorbed onto the surface of reduced graphene oxide via π-π interactions, and platinum nanoparticles are uniformly dispersed on the support to form a Pt / rGO-MB catalyst. A 0.1 mL dispersion of 1 mg / mL Pt / rGO-MB is uniformly coated onto the surface of carbon paper and dried at 60-100℃ for 30-60 minutes, resulting in a catalyst loading of 0.1 mg / cm³. 2 The electrocatalytic hydrogen production experiment was conducted in a three-electrode system, with an additional potential applied using an electrochemical workstation.

2. The method for selectively adsorbing methylene blue molecules onto the surface of a catalyst to achieve a highly efficient electrocatalytic hydrogen production reaction according to claim 1, characterized in that: Platinum precursor (PtCl2) and graphene oxide (GO) were dispersed in ethylene glycol, stirred and mixed, and then reduced at 120-150℃ for 20-30 minutes. After centrifugation and washing, Pt / rGO was obtained. The Pt / rGO dispersion was mixed with MB solution at a volume ratio of 1:3 and allowed to stand for 12-24 hours. Unadsorbed MB molecules were removed by centrifugation, and after washing and drying, Pt / rGO-MB was obtained.

3. The method for selectively adsorbing methylene blue molecules onto the catalyst surface to achieve a highly efficient electrocatalytic hydrogen production reaction according to claim 1, characterized in that: MB molecules are adsorbed onto the surface of reduced graphene oxide through π-π interactions.

4. The method for selectively adsorbing methylene blue molecules onto the catalyst surface to achieve a highly efficient electrocatalytic hydrogen production reaction according to claim 1, characterized in that: This strategy is applicable to acidic (0.5M H2SO4), neutral (1M PBS), or alkaline (1M NaOH) electrolytes.

5. The method for selectively adsorbing methylene blue molecules onto the catalyst surface to achieve a highly efficient electrocatalytic hydrogen production reaction according to claim 1, characterized in that: The mass ratio of platinum precursor to GO is 1:5, and the volume ratio of ethylene glycol to GO is 1:

2.

6. The method for selectively adsorbing methylene blue molecules onto the catalyst surface to achieve a highly efficient electrocatalytic hydrogen production reaction according to claim 1, characterized in that: The molecules are methyl violet (MV), Nile blue (NB), Rhodamine 110 (Rh110), and fluorescein (FL).

7. The method for selectively adsorbing methylene blue molecules onto the catalyst surface to achieve a highly efficient electrocatalytic hydrogen production reaction according to claim 1, characterized in that: The electrocatalytic hydrogen production experiment was conducted using a standard three-electrode reaction cell, controlled by an electrochemical workstation (CHI 630E, Shanghai Chenhua Instruments). The test system employed a three-electrode configuration: the catalyst-modified electrode served as the working electrode, while the platinum electrode and Ag|AgCl electrode served as the counter and reference electrodes, respectively. High-purity argon gas was continuously purged for 15 minutes before the test. During the formal test, linear sweep voltammetry was used, with a scan rate of 2-10 mV / s and a potential range of 0 to -0.8 V (vs. RHE).

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