A method for direct deposition of palladium using solar energy

Abstract

The application discloses a method for depositing and recycling precious metal palladium on a cathode conductive substrate by using solar energy to catalyze a photoanode, and adopts the technical scheme that a cylindrical electrolytic cell device is divided into a half anode chamber and a half cathode chamber, Na2SO4 solution is added into the anode chamber, Pd(NO3)2 solution is added into the cathode chamber, and the two are isolated by a proton exchange membrane; a ZnO photoelectrode is put into the anode chamber as an anode, a conductive substrate is put into the cathode chamber as a cathode, and the anode and the cathode are connected by external wires; and the ZnO photoelectrode is directly irradiated by sunlight for a period of time. According to the method, elemental metal palladium can be deposited on the conductive substrate after the photoelectrode is irradiated by light for a period of time. The method for depositing and recycling precious metal palladium by using solar irradiation without external voltage can provide a new idea for solar energy storage conversion and traditional metal recycling.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a method for directly depositing metallic palladium using solar energy. Background Technology

[0002] With excessive resource consumption and increasingly prominent environmental problems, precious metals, as a valuable non-renewable resource, have limited reserves. Solar energy, a clean, efficient, and sustainable "green energy" source, is inexhaustible and a new type of energy that alleviates energy shortages while protecting the environment. Semiconductor materials with photocatalytic functions are commonly used in photoelectric conversion. Zinc oxide has advantages such as low cost, easy availability, good controllability, and high stability. It exhibits good catalytic performance under both acidic and alkaline conditions, thus its application in photocatalysis is widespread. When a ZnO photoanode is excited by photons with energy greater than or equal to its band gap, electrons in the valence band are excited to the conduction band, forming photogenerated holes and photogenerated electrons. Photogenerated holes participate in the OER (Optical Emission Reduction) of the anode, while photogenerated electrons reach the cathode through an external circuit to carry out the reduction reaction of metal ions. This method, which collects palladium by depositing it on the cathode without applying an external voltage and through photo-irradiation of the anode, further broadens the utilization of renewable energy. It reduces recycling costs through photodeposition while also possessing the advantages of a simple process and environmental friendliness, showing great promise for large-scale industrial applications in the future. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for the pollution-free recovery of palladium by utilizing a photoanode to receive solar energy and simultaneously depositing the precious metal palladium on the cathode. This represents a novel form of solar energy utilization, offering a new approach to solar energy storage and conversion, as well as traditional metal recycling.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for directly depositing palladium using solar energy includes the following steps:

[0006] 1) Add Na2SO4 solution to the anode chamber of the column electrolytic cell and Pd(NO3)2 solution to the cathode chamber of the column electrolytic cell. A proton exchange membrane is provided in the connecting pipe between the anode chamber and the cathode chamber.

[0007] 2) Place the ZnO photoelectrode as the anode in the anode chamber of the column electrolytic cell, and place the conductive substrate as the cathode in the cathode chamber of the column electrolytic cell. Connect the ZnO photoelectrode and the conductive substrate with a wire.

[0008] 3) Directly irradiate the ZnO photoelectrode with sunlight for 20-120 minutes to deposit elemental palladium on the conductive substrate of the cathode.

[0009] Furthermore, in the above-mentioned method for direct deposition of palladium using solar energy, in step 1), the concentration of the Na2SO4 solution is 0.1-2 mol / L.

[0010] Furthermore, in the above-mentioned method for direct deposition of palladium using solar energy, in step 1), the mass concentration of the Pd(NO3)2 solution is 0.005-5%.

[0011] Furthermore, in the above-mentioned method for directly depositing palladium using solar energy, in step 2), the conductive substrate is a pure FTO conductive glass substrate.

[0012] Furthermore, in the above-mentioned method for directly depositing palladium using solar energy, in step 3), the intensity of direct sunlight irradiation is 50-200 mW·cm⁻¹. -2 .

[0013] Furthermore, in the above-mentioned method for directly depositing palladium using solar energy, step 2) of the method for preparing the ZnO photoelectrode includes the following steps:

[0014] 1) Drop an ethanol solution of Zn(NO3)2·2H2O onto the conductive side of the FTO conductive glass. After dropping, place the conductive glass in an oven to dry. Repeat the above steps three times. Place the obtained FTO conductive glass containing Zn into a muffle furnace and anneal at 300-650℃ for 10-25 min to form ZnO crystals. Cool to room temperature.

[0015] 2) Pour the mixture containing Zn(NO3)2·2H2O and hexamethylenetetramine into a reaction vessel containing the FTO conductive glass substrate obtained in step 1). Place the reaction vessel in an oven and react at 90-120℃ for 3-6 hours. Cool to room temperature, wash, and dry to obtain the ZnO photoelectrode.

[0016] Furthermore, in the above-mentioned method for direct deposition of palladium using solar energy, in step 1), the concentration of the ethanol solution of Zn(NO3)2·2H2O is 0.005 mol / L.

[0017] Furthermore, in the above-mentioned method for direct deposition of palladium using solar energy, in step 2), the molar concentration ratio of Zn(NO3)2·2H2O and hexamethylenetetramine is 0.05-0.3:0.1-0.6.

[0018] Preferably, in the above-described method for direct deposition of palladium using solar energy, the molar ratio of Zn(NO3)2·2H2O to hexamethylenetetramine is 1:2.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. The method of the present invention utilizes clean and pollution-free solar energy, avoids the use of additional electrical energy, and reduces the environmental pressure caused by thermal power generation.

[0021] 2. The method of this invention directly converts solar energy into chemical energy, providing a new approach to the storage and conversion of solar energy.

[0022] 3. The method of the present invention deposits the noble metal palladium on the cathode, which can alleviate the energy shortage problem to a certain extent. Attached Figure Description

[0023] Figure 1 These are scanning electron microscope (SEM) images of the ZnO thin film on the ZnO photoelectrode (a) and the elemental palladium deposited on the cathode conductive substrate (b).

[0024] Figure 2 This is the XRD pattern of the FTO conductive glass substrate and the deposited elemental palladium.

[0025] Figure 3 This is the XRD pattern of the ZnO thin film on the ZnO photoelectrode.

[0026] Figure 4 This is the UV-Vis diffuse reflectance spectrum of the ZnO thin film on the ZnO photoelectrode.

[0027] Figure 5 This is the It characteristic curve measured when a ZnO photoelectrode deposits metallic palladium under simulated sunlight.

[0028] Figure 6 This is a comparison diagram of the cathode conductive substrate before and after the performance test of the photochemical cell.

[0029] Figure 7 This is a schematic diagram of a photochemical cell structure, where 1: columnar electrolytic cell, 1-1: anode chamber, 1-2: cathode chamber, 2: proton exchange membrane, 3: ZnO photoelectrode, 4: pure FTO conductive glass substrate, and 5: wire.

[0030] Figure 8 This is a picture of a photochemical cell. Detailed Implementation

[0031] Example 1: Method for Direct Deposition of Palladium Using Solar Energy

[0032] (I) The method is as follows

[0033] 1. Preparation of ZnO photoelectrode:

[0034] 1) Drop a 0.005 mol / L Zn(NO3)2·2H2O ethanol solution onto the conductive side of the FTO conductive glass. After dropping, place the conductive glass in an oven and dry it at 60°C. Repeat the above steps three times. Place the obtained FTO conductive glass containing Zn into a muffle furnace and anneal it at 450°C for 15 min to form ZnO crystals. Cool it to room temperature.

[0035] 2) Pour the mixture containing 0.1 mol / L Zn(NO3)2·2H2O and 0.2 mol / L hexamethylenetetramine (HMT) into a reaction vessel containing the FTO conductive glass substrate obtained in step 1). Place the reaction vessel in an oven and react at 95°C for 4 hours. Cool to room temperature, wash, and dry to obtain a ZnO photoelectrode with a ZnO thin film on its surface.

[0036] 2. Preparation of photochemical cells:

[0037] A schematic diagram of the structure of a photochemical cell is shown below. Figure 7 Actual product image as shown Figure 8 .

[0038] 1) Add 50 mL of 0.5 mol / L Na2SO4 solution to the anode chamber (1-1) of the column electrolytic cell (1); add 50 mL of 0.01% Pd(NO3)2 solution to the cathode chamber (1-2) of the column electrolytic cell (1); a proton exchange membrane (2) is provided in the connecting pipe between the anode chamber (1-1) and the cathode chamber (1-2);

[0039] 2) Place the ZnO photoelectrode (3) as the anode in the anode chamber (1-1) of the column electrolytic cell, and place the pure FTO conductive glass substrate (4) as the cathode in the cathode chamber (1-2) of the column electrolytic cell. Connect the ZnO photoelectrode and the pure FTO conductive glass substrate (4) with wires (5).

[0040] 3) The light intensity is 120 mW·cm -2 The ZnO photoelectrode was irradiated with simulated sunlight for 60 minutes, and elemental palladium was deposited on the pure FTO conductive glass substrate (4) of the cathode.

[0041] (II) Performance Testing

[0042] 1) Scanning electron microscopy

[0043] The prepared ZnO photoelectrode and the elemental palladium deposited on the cathode conductive substrate were scanned using an electron microscope, and the morphology of the ZnO thin film and elemental palladium on the ZnO photoelectrode were characterized. The results are as follows: Figure 1 .Depend on Figure 1As can be seen, the fabricated ZnO photoelectrode shows that the ZnO nanoarray is formed by nanorods perpendicular to the FTO substrate, and its surface has a regular hexagonal edge structure. Figure 1 As can be seen from b, the deposited elemental palladium is granular and tightly arranged on the FTO substrate.

[0044] 2) XRD testing

[0045] The FTO conductive glass substrate and the deposit were characterized, and the results are as follows: Figure 2 The FTO conductive glass substrate was characterized. The FTO conductive glass substrate exhibited six diffraction peaks at 2θ = 26.6°, 33.8°, 37.8°, 51.8°, 61.7°, and 65.7°, corresponding to the (110), (101), (200), (211), (310), and (301) diffraction planes of tin dioxide (JCPDS-No. 46-1088), respectively. The deposited material was characterized. The deposit exhibited three diffraction peaks at 2θ = 40.1°, 46.7°, and 68.1°, corresponding to the (111), (200), and (220) diffraction planes of palladium (JCPDS-No. 05-0681), respectively.

[0046] The ZnO photoelectrode was characterized, and the results are as follows: Figure 3 The ZnO photoelectrode was characterized. The ZnO photoelectrode had eight diffraction peaks at 2θ = 31.8°, 34.4°, 36.3°, 47.5°, 56.6°, 62.9°, 68.0°, and 69.1°, which correspond to the (100), (002), (101), (102), (110), (103), (112), and (201) diffraction planes of zinc oxide (JCPDS-No. 36-1451), respectively.

[0047] 3) Ultraviolet-Visible Diffuse Reflectance Spectroscopy Detection

[0048] The zinc oxide thin film was subjected to UV-Vis diffuse reflectance testing, and the results are as follows: Figure 4 As shown.

[0049] Depend on Figure 4 It can be seen that the absorption edge of zinc oxide is 420nm, and the light absorption is mainly concentrated in the ultraviolet region.

[0050] 4) Performance testing of photochemical cells

[0051] The zinc oxide film was tested, and the results are as follows: Figure 5 and Figure 6 As shown. Figure 5 This is the It characteristic curve measured when a ZnO photoelectrode deposits palladium under simulated sunlight. (From...) Figure 5As can be seen, when ZnO thin films are irradiated with simulated sunlight, the current density of the ZnO photoelectrode remains stable at 0.13-0.15 mA / cm². 2 between. Figure 6 These are before-and-after comparison images of the cathode conductive substrate under simulated sunlight irradiation of a ZnO photoelectrode for 60 minutes. Figure 6 It can be seen that after 60 minutes, elemental palladium was deposited on the conductive substrate of the cathode.

Claims

1. A method for direct deposition of metallic palladium using solar energy, characterized in that, The method comprises the following steps: 1) adding a Na2SO4 solution with a concentration of 0.1-2 mol / L into an anode chamber of a column electrolytic cell, adding a Pd(NO3)2 solution with a mass concentration of 0.005-5% into a cathode chamber of the column electrolytic cell, and arranging a proton membrane in a connecting pipeline between the anode chamber and the cathode chamber; 2) placing a ZnO photoelectrode as an anode into the anode chamber of the column electrolytic cell, placing a conductive substrate as a cathode into the cathode chamber of the column electrolytic cell, and connecting the ZnO photoelectrode and the conductive substrate by wires; 3) directly irradiating the ZnO photoelectrode with sunlight for 20-120 minutes to deposit elemental Pd on the conductive substrate of the cathode; In step 2), the preparation method of the ZnO photoelectrode comprises the following steps: 2.1) dropping an ethanol solution of Zn(NO3)2·2H2O on a conductive side of FTO conductive glass, and then placing the conductive glass into an oven for drying, and repeating the above steps for three times; placing the obtained FTO conductive glass containing Zn element into a muffle furnace, annealing at 300-650 ℃ for 10-25 min to form ZnO crystals, and cooling to room temperature; 2.2) pouring a mixed solution containing Zn(NO3)2·2H2O and hexamethylenetetramine into a reaction kettle containing the FTO conductive glass substrate obtained in step 2.1), placing the reaction kettle into an oven, and reacting at 90-120 ℃ for 3-6 h, cooling to room temperature, washing, drying, and obtaining a ZnO photoelectrode.

2. The method for directly depositing palladium using solar energy according to claim 1, wherein, In step 2), the conductive substrate is a pure FTO conductive glass substrate.

3. The method for directly depositing palladium using solar energy according to claim 1, wherein, In step 3), the direct sunlight irradiation intensity is 50-200 mW•cm -2 .

4. The method for direct deposition of palladium metal using solar energy according to claim 1, wherein, In step 2.1), the concentration of the ethanol solution of Zn(NO3)2·2H2O is 0.005 mol / L.

5. The method for direct deposition of palladium metal using solar energy according to claim 1, wherein, In step 2.2), the molar concentration ratio of Zn(NO3)2·2H2O to hexamethylenetetramine is 0.05-0.3:0.1-0.

6.

6. The method for directly depositing palladium using solar energy according to claim 5, wherein, The molar concentration ratio of Zn(NO3)2·2H2O to hexamethylenetetramine is 1:2.

Images