New method for deep hydrogenation of atomic hydrogen supply and demand balance mediating small molecules

Abstract

The invention discloses a novel atomic hydrogen supply and demand balance mediated small molecule deep hydrogenation method, which comprises the following steps: introducing a non-metallic element to passivate terminal oxygen atoms of unsaturated coordination in spinel oxide (Co3O4), and constructing a Co3O4-X (X is non-metallic elements such as S, P, Si and the like) cathode electro-catalytic hydrogenation system; the generation rate of atomic hydrogen is effectively regulated and controlled, excessive generation of the atomic hydrogen is inhibited, and supply and demand balance of H * on the surface of the cathode is achieved. According to the method, the H < * > utilization rate is greatly increased, the hydrogen evolution reaction is remarkably inhibited, and the deep hydrogenation efficiency and selectivity of a small molecule target reactant are further improved. The Co3O4-X cathode electro-catalytic hydrogenation system constructed by the invention overcomes the key problem that H * supply and demand balance is difficult, efficiently realizes deep hydrogenation of small molecules, provides a new thought for improving the utilization efficiency of cathode active species in electro-catalytic reduction reaction, and provides technical support for designing and synthesizing efficient and stable electrode materials.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic hydrogenation technology, and in particular to a novel method for deep hydrogenation of small molecules mediated by atomic hydrogen supply and demand balance. Background Technology

[0002] Electrocatalytic hydrogenation is a cornerstone of biomass conversion and environmental pollution control. However, in electrocatalytic hydrogenation, the multiproton and multielectron reduction pathway competes kinetically with the dominant electrochemical water reduction to H2 (HER) pathway, requiring excessively high reduction potentials. Therefore, efforts should be made to suppress HER and improve the selectivity of electrochemical hydrogenation.

[0003]

[0004] Atomic hydrogen (H) * H is a key active species in many electrocatalytic reduction reactions. However, H * The formation of H+ often competes with the hydrogen evolution reaction (Equations 1-5), and the excess H+ produced... * The rapid self-quenching to generate hydrogen (H2) not only reduces the reduction efficiency of the target reactant, leading to low Faraday efficiency, but also damages the cathode material structure due to H2 bubble precipitation, causing a significant decrease in the stability of the reaction system. Theoretically, without self-quenching, H... * Effective utilization of [the catalyst] can improve the reduction efficiency of the target reactant and inhibit HER. Currently, the traditional strategy is to load noble metals (such as Pd, Ru, Ag, etc.) onto the cathode, utilizing their reaction with H [reactants]. * The high adsorption energy will H * Stable within the lattice of noble metals, thus extending the H... * The retention time at the cathode interface is limited to prevent self-quenching. However, this method suffers from problems such as complex preparation process, high cost, and slow hydrogenation kinetics, which restricts its large-scale application.

[0005] In electrocatalytic hydrogenation, the effective enrichment of reactants at the cathode is fundamental. Spinel-type oxides (AB₂O₄) possess abundant low-energy bands and a strong ability to interact with reactants, particularly the terminal oxygen sites (O₂O₄). u ) is considered H * The main active sites generated are often used as cathodes in electrocatalytic reduction processes. For example, cyanide (CN) - ) or nitrates (NO3) - It can be efficiently hydrogenated in a Co3O4 cathode system. In this process, due to the interaction between Co3O4 and CN... - / NO3 - The presence of strong forces allows anionic reactants to overcome electrostatic repulsion and accumulate on the cathode surface, thus enabling them to react once H+ is generated.* The reactants can be immediately reduced. However, when excess H+ is produced... * At that time, part of H * Insufficient time for the reactants to react resulted in their rapid recombination into H2, significantly reducing the H2 content. * Utilization rate. Therefore, in the electrocatalytic hydrogenation process, adjusting H... * The generation rate can be adjusted to achieve supply and demand balance, which can greatly improve H * This improves utilization rate, thereby further enhancing the hydrogenation efficiency of the target reactants.

[0006] Therefore, this invention constructs a method for regulating H by non-metal-doped Co3O4 passivated terminal oxygen sites. * Electrocatalytic hydrogenation system with high formation rate. Terminal oxygen (O) in Co3O4. u After bonding with the incorporated nonmetallic element, O u The p-band center shifts downward, thus weakening its interaction with H2O and increasing H2O's efficiency. * The generated free energy effectively regulates H * The generation rate of H was suppressed. * The excessive generation of H was achieved. * This balances supply and demand, thereby further improving the hydrogenation efficiency of small molecule compounds. Summary of the Invention

[0007] The purpose of this invention is to solve the technical problems existing in the prior art and to provide a new method for deep hydrogenation of small molecules mediated by atomic hydrogen supply and demand balance.

[0008] To achieve the above objectives, the technical solution provided by this invention is: a novel method for deep hydrogenation of small molecules mediated by atomic hydrogen supply and demand balance. The novel method includes introducing a non-metallic source element X to passivate the terminal unsaturated oxygen sites of Co3O4, constructing a Co3O4-X cathode electrocatalytic hydrogenation system. The terminal unsaturated oxygen sites of Co3O4 are denoted as O. U The Co3O4-X cathode electrocatalytic hydrogenation system is used for small molecule target reactants; in the Co3O4-X cathode electrocatalytic hydrogenation system, the O of Co3O4... U Co3O4-X cathode materials were constructed by bonding X elements to the top. By controlling the amount of non-metallic source X elements added to the Co3O4-X cathode materials, the H content could be controlled. * O in Co3O4 u Genesis free energy on H, inhibiting H * Excessive generation; that is, to achieve regulation of H * The "supply" of H and the effect of small molecule target reactants on H * To improve the balance between the "demand" and the quantity of demand, and to enhance H * Utilization rate, suppress HER, achieve H* It balances supply and demand and promotes the conversion of small molecules into deeply hydrogenated products.

[0009] Preferably, the small molecule target reactant in the Co3O4-X cathode electrocatalytic hydrogenation system is any one of cyanide, nitrate, carbon dioxide, or oxygen.

[0010] Preferably, the anode material in the Co3O4-X cathode electrocatalytic hydrogenation system is a commercially available stable anode or platinum sheet electrode, and the X element in the cathode material is one of S, P, or Si; and the X element is mainly SO4 in the material. 2- PO4 3- SiO3 2- It exists in the form of functional groups.

[0011] Preferably, the amount of non-metallic source element X added is 0.05~0.5 mmol.

[0012] Preferably, in the Co3O4-X cathode electrocatalytic hydrogenation system, sodium sulfate or sodium chloride is used as the electrolyte solution, and sodium hydroxide solution is used as the pH adjustment solution.

[0013] Preferably, the reaction apparatus for the Co3O4-X cathode electrocatalytic hydrogenation system is a 150 mL or 250 mL quartz electroreactor. The electrocatalytic process in the Co3O4-X cathode electrocatalytic hydrogenation system is provided with a constant voltage by an electrochemical workstation (CHI 660E, Shanghai Chenhua, China), with a voltage of -0.1 to -1.1 V vs. RHE. The residence time of the electrochemical hydrogenation reaction in the Co3O4-X cathode electrocatalytic hydrogenation system is 120 to 360 min.

[0014] Beneficial effects of this invention: This invention, through precise passivation of the active sites of the cathode material, can significantly improve the selectivity and efficiency of small molecule target reactants while significantly suppressing the hydrogen evolution reaction (HER). It effectively resolves the contradiction between reactant conversion and atomic hydrogen self-quenching in electrocatalytic reduction reactions by regulating H... * Achieving "supply and demand balance" to realize efficient and stable electrocatalytic hydrogenation; overcoming H * This breakthrough addresses the critical challenge of balancing supply and demand, achieving efficient deep hydrogenation of small-molecule target reactants. It provides new insights into improving the utilization efficiency of cathode active species in electrocatalytic reduction reactions and offers technical support for the design and synthesis of highly efficient and stable electrode materials. Attached Figure Description

[0015] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0016] Figure 1 The oxygen sites at the S passivation terminal of the Co3O4-S cathode in this invention and their H * Create a schematic diagram; Figure 2 The X-ray diffraction patterns of Co3O4 and Co3O4-S cathode materials in this invention are shown. Figure 3 This is the X-ray energy dispersive spectroscopy (EDS) analysis diagram of the Co3O4-S cathode material in this invention; Figure 4 The Raman spectra of Co3O4 and Co3O4-S cathode materials in this invention are shown. Figure 5 The X-ray photoelectron spectra of S 2p and O 1s of the Co3O4 and Co3O4-S cathode materials in this invention are shown. Figure 6 The content of sulfur (S) and cyanide (CN) in this invention - A linear relationship graph between conversion rates; Figure 7 CN under different voltages in this invention - Comparison of reduction efficiency in Co3O4 and Co3O4-S systems.

[0017] Figure 8 The content of sulfur (S) and nitrate (NO3) in this invention - A linear relationship graph between conversion rates; Figure 9 NO3 under different voltages in this invention - Comparison of reduction efficiency between Co3O4 and Co3O4-S systems; Figure 10 This is a comparison of the reduction efficiency of CO2 in the Co3O4 and Co3O4-S systems under different voltages in this invention; Figure 11 This is a comparison chart of the reduction electron transfer numbers of oxygen (O2) in the Co3O4 and Co3O4-S systems in this invention; Figure 12 This is a linear sweep voltammetry curve of Co3O4-S cathodes with different S contents in a solution without small molecules in this invention; Figure 13 This is a cyclic voltammetry curve of the Co3O4-S and Co3O4 cathodes in the reaction solution in this invention. Detailed Implementation

[0018] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0019] The specific methods for determining the content of each product in this invention are as follows: The change in total nitrogen concentration was determined using the traditional alkaline persulfate oxidation method.

[0020] The concentration change of ammonia nitrogen in the reaction system was determined by Nessler's reagent spectrophotometry. The spectrophotometer used was a U-3900, Hitachi Ltd, Japan.

[0021] The concentration changes of total cyanide and free cyanide in the reaction system were determined by the isonicotinic acid-barbituric acid colorimetric method.

[0022] The concentration change of methylamine in the reaction system was determined by the p-nitroaniline colorimetric method.

[0023] The concentration changes of methane and carbon monoxide in the reaction system were determined by gas chromatography. The gas chromatograph used was a GC-2014, Shimadzu Inc., Japan.

[0024] The changes in the contents of cyanate, nitrite, and nitrate in the reaction system were determined by ion chromatography. The ion chromatograph used was a Dionex-120, Dionex Inc., USA. Example 1

[0025] Sulfur-doped Co3O4 cathode material (Co3O4-S) is used for the hydrogenation conversion of small molecule target reactants.

[0026] In this embodiment, Co3O4-S is used as the cathode material, and the small molecule target reactant is CN. - NO3 - Any one of CO2 and O2.

[0027] First, regarding CN - For reduction, add 100 mL of free cyanide (1.33 mM, pH=11.5) to the electroreactor. Add 100 mM sodium sulfate or sodium chloride to a beaker, stir to dissolve, and then pour the solution into the reactor. Use a commercially available stable electrode as the anode and Co3O4-S as the cathode. Insert the electrode into the solution and maintain it under magnetic stirring for 1 hour to determine the maximum cyanide concentration. After applying a constant voltage, take 2 mL samples at set time points using a 5 mL syringe, filter through a 0.45 μm filter, and place in 5 mL centrifuge tubes.

[0028] For NO3 - For reduction, add 100 mL of nitrate solution (100 mg-N / L) to the electroreactor. Add 50 mM sodium sulfate to a beaker, stir to dissolve, and then pour the solution into the reactor. Use a Pt sheet as the anode and Co3O4-S as the cathode. Before the reaction begins, argon gas is introduced for 30 min to remove dissolved oxygen. Other steps are the same as above.

[0029] For O2 reduction, the number of transferred electrons was measured in 0.1 M KOH solution using a rotating disk electrode (RRDE) to evaluate its hydrogenation effect.

[0030] For CO2 reduction, Pt sheet was used as the anode and Co3O4-S as the cathode. 25 mL of potassium carbonate solution (0.5 M) was added to the H-type reactor. Before the reaction started, CO2 was introduced for 30 min to reach saturation, and then a constant voltage was applied to start the reaction.

[0031] The specific method for preparing the electrode material Co3O4-S in this example is as follows: First, the FTO substrate (1.5 cm × 4 cm) was ultrasonically cleaned with acetone, ethanol and ultrapure water for 15 min each, and then dried for later use.

[0032] Then, 0.582 g of cobalt nitrate and a certain amount of thiourea (0.05 - 0.5 mmol) were dissolved in 10 mL of ethylene glycol and 30 mL of water. 0.5 g of urea, 1.455 g of ammonium fluoride, and 0.05 g of polyvinylpyrrolidone (PVP, K29-32) were added sequentially to the above solution. The mixture was stirred at room temperature for 30 min, and the homogeneous solution was transferred to a 100 mL reactor. Finally, a treated FTO substrate was tilted and immersed in the reaction solution. The autoclave was sealed and reacted at 120 °C for 12 h. After the reaction, the electrode was washed with a large amount of deionized water and dried at 60 °C. The dried electrode material was then calcined in air at 350 °C for 2 h, followed by a further increase to 550 °C and a holding time of 2 h. After cooling to room temperature, it was ready for use. Example 2

[0033] Phosphorus-doped Co3O4 cathode material (Co3O4-P) is used for the hydrogenation conversion of small molecule target reactants.

[0034] In this embodiment, Co3O4-P is used as the cathode material, and the reaction conditions are the same as in Example 1.

[0035] The specific preparation method of the Co3O4-P electrode material in this example is as follows: First, the FTO substrate (1.5 cm × 4 cm) was ultrasonically cleaned with acetone, ethanol, and ultrapure water for 15 min each, and then dried for later use. Next, 0.582 g of cobalt nitrate and a certain amount of ammonium dihydrogen phosphate were dissolved in 10 mL of ethylene glycol and 30 mL of water. Then, 0.5 g of urea, 1.455 g of ammonium fluoride, and 0.05 g of polyvinylpyrrolidone (PVP, K29-32) were added sequentially to the above solution. The mixture was stirred at room temperature for 30 min, and the homogeneous solution was transferred to a 100 mL reaction vessel. Finally, a piece of the treated FTO substrate was tilted and immersed in the reaction solution. The autoclave was sealed and reacted at 120 °C for 12 h. After the reaction, the electrode was washed with a large amount of deionized water and dried at 60 °C. The dried electrode material was then calcined in air at 350 °C for 2 h, followed by a further increase to 550 °C and a 2 h holding period. It was then cooled to room temperature for later use. Example 3

[0036] Silicon-doped Co3O4 cathode material (Co3O4-Si) is used for the hydrogenation conversion of small molecule target reactants.

[0037] In this embodiment, Co3O4-Si is used as the cathode material, and the reaction conditions are the same as in Example 1.

[0038] The specific preparation method of the Co3O4-Si electrode material in this example is as follows: First, the FTO substrate (1.5 cm × 4 cm) was ultrasonically cleaned with acetone, ethanol, and ultrapure water for 15 min each, and then dried for later use. Next, 0.582 g of cobalt nitrate and a certain amount of tetraethyl orthosilicate were dissolved in 10 mL of ethylene glycol and 30 mL of water. Then, 0.5 g of urea, 1.455 g of ammonium fluoride, and 0.05 g of polyvinylpyrrolidone (PVP, K29-32) were added sequentially to the above solution. The mixture was stirred at room temperature for 30 min, and the homogeneous solution was transferred to a 100 mL reaction vessel. Finally, a piece of the treated FTO substrate was tilted and immersed in the reaction solution. The autoclave was sealed and reacted at 120 °C for 12 h. After the reaction, the electrode was washed with a large amount of deionized water and dried at 60 °C. The dried electrode material was then calcined in air at 350 °C for 2 h, followed by a further increase to 550 °C and a 2 h holding period. It was then cooled to room temperature for later use.

[0039] The deep hydrogenation effect of the present invention on small molecules and its mechanism of action are discussed in detail based on the specific experimental results of Example 1 of the present invention.

[0040] like Figure 2-5 As shown, this invention confirms the existence form and bonding sites of sulfur (S) in Co3O4 materials through multi-level characterization methods.

[0041] first, Figure 2-3 The results show that the incorporation of S did not change the crystal structure of Co3O4, and the S element was uniformly distributed in the material, proving that S was successfully introduced and did not cause phase separation; secondly, Raman spectroscopy ( Figure 4 The characteristic vibrational peaks of the Co-S bond did not appear in the spectrum, but the characteristic peaks of the Co-O bond were redshifted, proving that S did not directly coordinate with the Co atom, but rather affected the lattice environment by weakening the Co-O bond. Figure 5 This provides even more crucial evidence: the characteristic peak with a binding energy of 170.5 eV in the S 2p XPS spectrum belongs to SO bonds (such as SO4). 2- (structure), rather than Co-S bonds; at the same time, the unsaturated coordinated terminal oxygen (O) in the O 1s XPS spectrum u The characteristic peak area of ​​S decreased significantly, and the magnitude of this decrease was linearly related to the increase in the peak area of ​​SO. This directly proves the relationship between S and O. u A bond was formed at the site. Multivariate characterization techniques systematically demonstrated that S was successfully incorporated into Co3O4 and precisely bonded to the terminal oxygen (O). u ) site.

[0042] like Figure 6-11 As shown, in a Co3O4 system where the terminal oxygen is not passivated, H * The ineffective utilization of these components resulted in low hydrogenation efficiency for small molecules. In contrast, in the Co3O4-S cathode electrocatalytic system, the passivation of terminal unsaturated oxygen active sites by sulfur inhibited their interaction with H2O, thus suppressing H2O at its source. * Excessive generation to achieve H * A balance between supply and demand allows for the deep hydrogenation of small molecule reactants. The hydrogenation performance of small molecules is mainly affected by the sulfur doping amount and the potential and voltage. Through experimental condition control, the Co3O4-S cathode electrocatalytic system can effectively control the hydrogenation performance when the sulfur source addition is 0.2 mmol and the sulfur doping content is 0.22 wt%. * The generation of atomic hydrogen (H) * The supply and demand balance mediates the deep hydrogenation of small molecule target reactants. These results indicate that the passivation strategy of unsaturated coordination-terminal oxygen sites can effectively promote H... * This improves utilization and inhibits HER, enabling deep hydrogenation of reactants.

[0043] like Figure 11-12 As shown, linear sweep voltammetry (LSV) and cyclic voltammetry (CV) tests revealed that with increasing S doping concentration, the onset potential of the hydrogen evolution reaction (HER) shifted significantly negatively, and its reduction peak disappeared. This indicates that the introduction of S effectively suppressed HER. Furthermore, the H2O2 at the Co3O4-S cathode... *ads The strength is approximately 2.3 times that of Co3O4, further confirming that the Co3O4-S interface retains more H. * These H atoms that did not self-quench into H2 * It can be further used for the deep hydrogenation of small molecules.

[0044] As can be seen from the above embodiments, this invention achieves the electrocatalytic treatment of cyanide (CN) by constructing a novel Co3O4-S cathode electrocatalytic system based on sulfur passivation of terminal unsaturated oxygen atoms. - ), nitrates (NO3) - This system enables the efficient and deep hydrogenation of various small molecules, including sulfur, carbon dioxide (CO2), and oxygen (O2). By precisely controlling the sulfur doping amount (preferably 0.22 wt%) and the applied potential, atomic hydrogen (H2) can be achieved. * While achieving on-demand generation and supply-demand balance, it effectively suppresses its self-recombination into H2 (HER), thus overcoming the challenge of H2 self-recombination in traditional electrocatalytic hydrogenation processes. * This passivation strategy addresses the key challenges of low utilization and poor selectivity of target products. It not only significantly improves the Faraday efficiency and electron transfer number of various small molecule deep hydrogenation processes, but also, due to its excellent stability and universality, provides a promising technical pathway for the deep purification and resource recovery of highly toxic pollutants.

[0045] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0046] The above description is only a preferred embodiment of the present invention. Any technical solution that achieves the purpose of the present invention by essentially the same means is within the protection scope of the present invention.

Claims

1. A novel method for deep hydrogenation of small molecules mediated by atomic hydrogen supply and demand balance, characterized in that: The novel method involves introducing a non-metallic source element X to passivate the terminal unsaturated oxygen sites of Co3O4, constructing a Co3O4-X cathode electrocatalytic hydrogenation system, where the terminal unsaturated oxygen sites of Co3O4 are denoted as O. U The Co3O4-X cathode electrocatalytic hydrogenation system is used for small molecule target reactants; in the Co3O4-X cathode electrocatalytic hydrogenation system, the O of Co3O4... U Co3O4-X cathode materials were constructed by bonding X elements to the top. By controlling the amount of non-metallic source X elements added to the Co3O4-X cathode materials, the H content could be controlled. * O in Co3O4 u Genesis free energy on H, inhibiting H * Excessive generation; that is, to achieve regulation of H * The "supply" of H and the effect of small molecule target reactants on H * To improve the balance between the "demand" and the quantity of demand, and to enhance H * Utilization rate, suppress HER, achieve H * It balances supply and demand and promotes the conversion of small molecules into deeply hydrogenated products.

2. The novel method for deep hydrogenation of small molecules mediated by atomic hydrogen supply and demand balance according to claim 1, characterized in that: The small molecule target reactant in the Co3O4-X cathode electrocatalytic hydrogenation system is any one of cyanide, nitrate, carbon dioxide, or oxygen.

3. A novel method for deep hydrogenation of small molecules mediated by atomic hydrogen supply and demand balance according to claim 1, characterized in that: In the Co3O4-X cathode electrocatalytic hydrogenation system, the anode material is a commercially available stable anode or platinum sheet electrode, and the X element in the cathode material is one of S, P, or Si; and the X element in the material is mainly SO42-. 2- PO4 3- SiO3 2- It exists in the form of functional groups.

4. A novel method for deep hydrogenation of small molecules mediated by atomic hydrogen supply and demand balance according to claim 1, characterized in that: The amount of nonmetallic source element X added is 0.05~0.5 mmol.

5. A novel method for deep hydrogenation of small molecules mediated by atomic hydrogen supply and demand balance according to claim 1, characterized in that: In the Co3O4-X cathode electrocatalytic hydrogenation system, sodium sulfate or sodium chloride is used as the electrolyte solution, and sodium hydroxide solution is used as the pH adjustment solution.

6. A novel method for deep hydrogenation of small molecules mediated by atomic hydrogen supply and demand balance according to claim 1, characterized in that: The reaction apparatus for the Co3O4-X cathode electrocatalytic hydrogenation system is a 150 mL or 250 mL quartz electroreactor. The electrocatalytic process in the Co3O4-X cathode electrocatalytic hydrogenation system is provided with a constant voltage by an electrochemical workstation, with a voltage of -0.1 to -1.1 V vs. RHE. The residence time of the electrochemical hydrogenation reaction in the Co3O4-X cathode electrocatalytic hydrogenation system is 120 to 360 min.

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