Method for preparing metal nano-powder through room-temperature plasma electrolysis

Abstract

The invention discloses a method for preparing metal micro powder through room-temperature plasma electrolysis. The method aims at solving the problems that an existing metal micro powder preparation method is large in production consumption, long in production process, prone to atom migration and agglomeration, uncontrollable in dispersity and the like. According to the method, an aqueous solution of an adsorption catalytic material containing rich defect sites is added, electrons are injected into the aqueous solution containing metal ions through a non-contact electrode glow discharge plasma electrolysis technology under the conditions of normal temperature and normal pressure, bonding of the electrons and the metal ions is achieved, and the metal atom particles are synthesized. The method is low in raw material cost, simple in reaction operation, high in safety and short in process. Meanwhile, the application range of metal is wide, and scientific research and expanded production of different metal atoms and different catalytic systems are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical metallurgy and powder metallurgy, and relates to a method for preparing metal micropowder by room temperature plasma electrolysis. Background Art

[0002] Metal powders have unique physical and chemical properties, such as good electrical conductivity, thermal conductivity, ductility and toughness. Metal powder catalysts play an important role in chemical industry, environmental protection and energy conversion due to their high atomic utilization and unique catalytic active sites. For example, single atom catalysts (SACs) have shown excellent activity in energy-related applications such as electrocatalysis and photocatalysis.

[0003] The efficient use of metal powders and the development of new materials are driving technological progress and market growth in related industries. As the demand for environmentally friendly and sustainable technologies increases, the application of metal powders in catalysis and energy is expected to continue to expand. This will not only improve production efficiency, but also help reduce dependence on rare metal resources, thus having a positive impact on the social economy.

[0004] At present, the preparation methods of metal micropowders are mainly divided into the following categories: coprecipitation method, impregnation method, atomic layer deposition method, reverse Ostward ripening method, solid phase melting method, etc. In general, most of the above methods involve harsh synthesis conditions, expensive drugs and raw materials, and complex post-processing processes. The present invention creatively starts from cost control and realizes low-cost, low-pollution, and short-process preparation of metal micropowders through a plasma electrolysis reaction synthesis path. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for preparing metal micropowder by room temperature plasma electrolysis.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] The electrode is suspended above the electrolyte. After the voltage is applied, the gas between the cathode and the electrolyte is ionized to form a plasma. The electrons are injected into the electrolyte under the action of the electric field, and bonded with the metal ions in the electrolyte to form metal micropowders. After the atomic nucleus is formed, it is difficult for the crystal nucleus to grow due to the lack of electrode attachment. At the same time, a large number of defect sites are constructed in situ on the carbon carrier. When the metal micropowder moves to the vicinity of the carrier, it is captured by the defect sites on the carbon carrier and further coordinated and anchored by nitrogen species to form a stable M-NX structure, thereby obtaining a single-atom catalyst, and the metal micropowder is obtained after subsequent treatment.

[0008] The specific steps are as follows:

[0009] (1) Pretreatment

[0010] Polish the electrode, and use tungsten wire, tungsten disilicide, Ni-YSZ (yttria-stabilized zirconia), lead-antimony alloy, graphite, platinum, titanium, nickel, copper, and tungsten-copper alloy as the cathode for electrolysis, preferably a tungsten wire with a 1 mm diameter and a conical top as the cathode;

[0011] (2) Preparation of electrolyte

[0012] The electrolyte is an active metal salt solution, preferably with a concentration of 0.2M. Adsorbents and precipitants are added to the electrolyte to enhance the adsorption effect of metal ions and the purity of the solution. The adsorbent is preferably activated carbon, zeolite and other adsorbents, which have high adsorption capacity and can remove impurities in the solution; the precipitant is preferably sodium hydroxide, sodium carbonate and other precipitants, which react with metal ions to form insoluble precipitates, thereby further purifying the solution;

[0013] The active metal includes at least one of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Rh, Pd, Ag, W, Ir, Pt, and Au;

[0014] (3) Assemble the electrolytic cell, with the cathode less than 2 cm, preferably 1 cm, from the liquid surface. The electrolysis voltage of the ion generator is 70-225 V, preferably 200 V; the electrolysis time is 5-200 min, preferably 30 min.

[0015] Compared with the existing technology, the plasma electrolysis method for obtaining metal powder has the following beneficial effects:

[0016] The material preparation method is innovative and uses non-contact electrode glow discharge plasma electrolysis at room temperature and pressure, avoiding the long process and low efficiency problems of traditional methods. Electrons are directly injected into the solution to bond with metal ions to generate metal or oxide nanoparticles dispersed in the electrolyte, which has the characteristics of high efficiency, rapidity and low temperature.

[0017] The product quality is well controllable. Using high-purity soluble metal anodes and high-purity chemical reagents, high-purity products can be obtained. By regulating the electrolysis industry, powder materials with different components (metal powder or metal oxide) and different particle sizes can be obtained. It has the advantages of controllable purity, composition and particle size.

[0018] The preparation conditions are mild and environmentally friendly. This technology can achieve efficient and large-scale production of metal micropowders in aqueous solution, and the preparation process has no pollution emissions.

[0019] High-quality metal powder can be obtained. It plays a great role in energy conversion and storage technology. Metal powder has the advantages of high atomic utilization, adjustable surface characteristics, special electronic structure, etc. It can be used in various fields of energy, as well as to build new optoelectronic devices and sensors, and as a potential information carrier in quantum computing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Different concentrations of CuSO 4 SEM image of particles after electrolysis for 30 min at the corresponding discharge voltage.

[0021] (a)0.2MCuSO 4 , 155V; (b) 0.4MCuSO 4 , 140V; (c) 0.6MCuSO 4 , 125V; (d) 0.8MCuSO 4 , 105V;

[0022] Figure 2 Yes (a) 0.4MH 2 SO 4 and (b) 0.2MCuSO 4 -0.4MH 2 SO 4 SEM characterization of the plasma discharge electrolysis products at 150V in the system.

[0023] Figure 3 It is 0.2MCuSO 4 SEM images of particle morphology obtained by plasma electrolysis at 170 V in solution for different times.

[0024] (a)10min; (b)20min; (c)30min; (d)60min;

[0025] Figure 4 It is 0.2MCuSO 4 SEM images of particles after plasma discharge electrolysis for 30 min at different voltages.

[0026] (a)130V; (b)170V; (c)190V; (d)210V;

[0027] Figure 5 0.2MCoSO at different electrolysis voltages 4 –XRD pattern of the product in 0.086MNaCl electrolyte.

[0028] (a)195V; (b)210V; (c)225V; (d)240V; (e)255V.

[0029] Figure 6 0.2MCoSO at different electrolysis voltages 4 –SEM image of the product in 0.086M NaCl electrolyte.

[0030] (a)210V; (b)240V; (c)255V.

[0031] Figure 7 0.2MCoSO under different electrolysis time 4 –XRD pattern of the product in 0.086MNaCl electrolyte.

[0032] (a) 20min; (b) 30min; (c) 40min; (d) 50min; (e) 60min.

[0033] Figure 8 0.2MCoSO under different electrolysis time 4 –SEM image of the product in 0.086M NaCl electrolyte.

[0034] (a)30min; (b)40min; (c)60min.

[0035] Fig. 9 It is the XRD pattern of the electrolysis products in the two solutions.

[0036] (a) 0.2MCrCl 3 –1% C 2 H 5 OH; (b) 0.2MCrCl 3 –0.2MH 2 SO 4 . DETAILED DESCRIPTION

[0037] The embodiments of the present invention will be clearly and completely described below in combination with the technical solutions and drawings.

[0038] The material characterization instruments are as follows: X-Ray Diffractomer (D / MAX2500PC).

[0039] Example: Method for preparing metal nanopowders by room temperature plasma electrolysis

[0040] 1. Carbon adsorbent was added to the electrolyte of 0.2MCuSO4, 0.4MCuSO4, 0.6MCuSO4 and 0.8MCuSO4. The discharge voltage was 155V, 140V, 125V and 105V respectively. The electrolysis time was 30min. The obtained products were all a mixture of Cu and Cu2O with a particle size of about 40nm.

[0041] 2. In the 0.4MH2SO4 and 0.2MCuSO4-0.4MH2SO4 system, a carbon adsorbent was added, the discharge voltage was 150V, and the electrolysis time was 30min. The product was micron-level copper powder. The SEM results of the product are as follows: Figure 2 .

[0042] 3. Use 0.2MCuSO4 electrolyte, add carbon adsorbent, and discharge at 170V. The electrolysis time is set to 10min, 20min, 30min and 60min. When the discharge electrolysis time is 10min, the product is cuprous oxide, and the average particle diameter is 100nm. However, when the electrolysis time is extended to 60min, the product is cuprous oxide, and the particles have an obvious tendency to aggregate. The particle diameter after aggregation reaches 400nm. The SEM characterization results of the electrolysis product are as follows Figure 3 As shown. Figure 3 It can be seen that when the discharge electrolysis time is 10 minutes, the average diameter of the product particles is 100nm. However, when the electrolysis time is extended to 60 minutes, the particles have an obvious tendency to aggregate, and the diameter of the aggregated particles reaches 400nm.

[0043] 4. In the 0.2MCuSO4 aqueous solution system, carbon adsorbent was added, the electrolysis voltage was set to 130V, 170V, 190V and 210V, and the electrolysis time was 30min. The research results are as follows: Figure 4 When the voltage is 130V (the discharge zone is in a non-luminous state), the product is cuprous oxide with a particle size of about 200nm, and a clear polyhedral shape can be seen. When the electrolysis voltage is increased to 210V, the particles are refined and the size is only about 40nm.

[0044] 5. A carbon adsorbent was added to the CoSO4–0.086MNaCl electrolyte. The discharge electrolysis time was 30 min, the electrolysis voltage was 132 V, and the product was a particle powder with an average size of 100 nm.

[0045] 6. The electrolyte composition was 0.2M CoSO4–0.086M NaCl, and the electrolysis was carried out for 30 minutes at voltages of 195V, 210V, 225V, 240V, and 255V, respectively. The XRD and SEM characterization results of the electrolysis products are shown in Figure 5 and 6 As shown. When the voltage is 210V, the product is a large aggregate with a size of several microns. When the voltage is increased to 240V, some petal-like structures and some fine particles appear. The surface becomes porous with a pore size of about 300nm. When the voltage increases to 255V, the surface becomes smooth, the pore size becomes smaller, and the small particles become smaller, with an average size of 100nm. When the voltage is 195V, the CoO mass fraction in the product is 96.5%. As the voltage increases to 210V, 225V and 240V, the content decreases to 93.4%, 93.0% and 92.6%. When the voltage is 255V, the CoO mass fraction is 92%. As the voltage increases, the CoO content decreases linearly.

[0046] 7. 0.2 M CoSO4–0.086 M NaCl was used as the electrolyte, and the electrolysis voltage was set to 225 V. The electrolysis was performed for 20 min, 30 min, 40 min, 50 min, and 60 min respectively. The XRD and SEM images of the products are shown in Figure 7 and Figure 8 shown.

[0047] 8. The concentrations of CrCl3 electrolyte were 0.05M, 0.1M, 0.2M and 0.4M. When carbon adsorbent was added, the discharge voltage was 210V when the electrolyte concentration was 0.05M; when the electrolyte concentration increased to 0.4M, the discharge voltage dropped to 95V. The electrolysis time was 30min, and the size was spherical small particles of 40–100nm.

[0048] 9. Plasma discharge electrolysis was carried out in two systems: 0.2MCrCl3–1% ethanol (volume ratio) and 0.2MCrCl3–0.2MH2SO4. Carbon adsorbent was added. The voltage was set to 140V and the electrolysis time was 30min. The XRD spectrum of the product was as follows: Fig. 9 As shown. When the electrolysis is carried out in 0.2MCrCl3–1% ethanol, the product is a flake aggregated together, and some small polyhedral particles with a size of 500–800nm ​​can be seen. When the electrolysis process is carried out in the 0.2MCrCl3–0.2MH2SO4 system, the flakes are thinner, and obvious spherical small particles with a size of 40–100nm can be seen. TEM characterization shows that the product obtained by electrolysis is spherical particles with a size of 30–50nm, which is consistent with the SEM results.

[0049] 10. In the electrolyte of 0.1M ammonium perrhenate (NH4ReO4), carbon adsorbent was added, NaCl was added to stabilize the arc and reduce the electrolysis voltage. The discharge voltage was 280V, and the electrolysis was carried out for 30 minutes under the discharge voltage. The product obtained was Re-ReO3 composite powder with a particle size of about 30nm. The discharge cathode was W wire, and the anode was Pt wire with a diameter of 1mm. The Pt wire used in the experiment was heated to 760℃ at a heating rate of 10℃ / min, kept warm for 1h, and then annealed with air cooling to process the Pt wire into a spiral shape.

Claims

1. A method for preparing metal nanopowders by room temperature plasma electrolysis, characterized in that: Here are the steps: (1) Pretreatment Grinding electrodes, using tungsten wire, tungsten disilicide, Ni-YSZ, lead-antimony alloy, graphite, platinum, titanium, nickel, copper, tungsten-copper alloy as cathode for electrolysis; (2) Preparation of electrolyte The electrolyte is an active metal salt solution. Adsorbents and precipitants are added to the electrolyte to enhance the adsorption effect of metal ions and the purity of the solution; the active metals include at least one of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Rh, Pd, Ag, W, Ir, Pt, and Au; (3) Assemble the electrolytic cell, with the cathode less than 2 cm from the liquid surface; the electrolysis voltage of the ion generator is 70-225 V; and the electrolysis time is 5-200 min.

2. The method for preparing metal nanopowder by room temperature plasma electrolysis according to claim 1, further characterized in that: In step (1), a tungsten wire with a 1 mm diameter and a conical top is used as the cathode.

3. The method for preparing metal nanopowder by room temperature plasma electrolysis according to claim 1, further characterized in that: In step (2), the electrolyte is a 0.2M concentration of active metal salt solution.

4. The method for preparing metal nanopowder by room temperature plasma electrolysis according to claim 2, further characterized in that: In step (2), activated carbon or zeolite is selected as the adsorbent; the precipitant is sodium hydroxide or sodium carbonate, which reacts with the metal ions to form an insoluble precipitate, thereby further purifying the solution.

5. The method for preparing metal nanopowder by room temperature plasma electrolysis according to claim 1, further characterized in that: In step (3), the cathode of the electrolytic cell is 1 cm away from the liquid surface.

6. The method for preparing metal nanopowder by room temperature plasma electrolysis according to claim 1, further characterized in that: In step (3), the electrolysis voltage of the ion generating device is 200V.

7. The method for preparing metal nanopowder by room temperature plasma electrolysis according to claim 1, further characterized in that: In step (3), the electrolysis time is 30 min.

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