Construction method of electrolytic tank for hydrogen production synergistic degradation of formaldehyde wastewater by taking manganese-based electrocatalyst as substrate

Abstract

The invention discloses a construction method of an electrolytic tank for hydrogen production synergistic degradation of formaldehyde wastewater by taking a manganese-based electrocatalyst as a substrate, which comprises the following steps: S1, sequentially dissolving a certain amount of KMnO4 and MnSO4 in a certain amount of deionized water, transferring into a high-pressure kettle, adding a current collector into the solution, heating in a drying oven for a certain time, cooling, washing and drying to obtain a manganese-based catalyst; the manganese-based electrocatalyst is obtained; s2, preparing an electrode by taking the manganese-based electrocatalyst prepared in S1 as a material; and S3, constructing a two-electrode system by taking the electrode manufactured in the S2 as a cathode and an anode, constructing a formaldehyde-based electrolytic tank by taking a KOH / HCHO mixed solution as an electrolyte, and applying a certain voltage for electrolysis. Due to the design of the electrolytic tank, the water electrolysis hydrogen production efficiency is effectively improved, and formaldehyde harmful pollutants in a water body are degraded.

Description

Technical Field

[0001] The present invention relates to the technical field of water electrolysis, and in particular to a method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater using a manganese-based electrocatalyst as a substrate. Background Art

[0002] The energy crisis is increasingly recognized as one of the most serious challenges facing modern society. To meet this challenge, the rapid development of environmentally friendly and sustainable energy has become crucial, and hydrogen energy has attracted widespread attention in this context. Hydrogen energy is recognized as an effective energy source that can not only provide clean energy, but also has a wide range of applications in fuel conversion and storage due to its high energy density and clean combustion characteristics. It is in this context that electrochemical water splitting, a hydrogen production method, has become the focus, which produces hydrogen and oxygen through the oxygen evolution reaction and hydrogen evolution reaction at the anode and cathode, respectively. However, hydrogen production through water splitting reaction also faces a huge bottleneck. The high overpotential of at least 1.23 V is required in the anode oxygen evolution process, which greatly reduces the hydrogen production efficiency. Therefore, efficient electrochemical reaction strategies are urgently needed to balance this defect. Recently, researchers have explored innovative methods such as electrochemical reforming, that is, using small molecules with higher oxidation thermodynamics at the anode: methanol, ethanol, glycerol, formaldehyde, urea and other biomass chemicals, etc., to replace the oxidation reaction to strategically replace oxygen release, thereby alleviating the limitations of the traditional high overpotential of the oxygen evolution reaction to improve the efficiency of hydrogen production. In existing reports, Yuan et al. reported a cobalt-based bifunctional electrolytic cell with formaldehyde as the oxidizing molecule (application publication number: CN114941155A), and Hao et al. reported a nickel-based electrocatalyst and hydrogen production synergistic degradation of formaldehyde wastewater electrolytic cell (application publication number: CN114959771A). The researchers have therefore improved the efficiency of electrolytic water electrolysis and hydrogen production in the electrolytic cell. However, in the design of these two, the substrate materials used are cobalt source and nickel source, respectively, which have a high unit price cost. The survey shows that no one has adopted the design strategy of a bifunctional electrolytic cell with manganese as the electrocatalyst and formaldehyde as the oxidizing molecule. The rich, cheap, efficient and stable manganese-based electrocatalyst material will become an important metal substrate material that cannot be ignored in the market. Therefore, this design intends to use cheap manganese oxide as the substrate, and formaldehyde oxidation reaction instead of slow water oxidation, so as to improve hydrogen production while degrading rich formaldehyde pollutants, and use it for hydrogen production with higher energy conversion efficiency and lower energy consumption. It is an environmentally friendly and energy-saving new hydrogen production strategy with obvious practical application value. Summary of the invention

[0003] 1. Technical problems to be solved: The existing base materials used for the electrolysis of formaldehyde wastewater are cobalt source and nickel source, which have a relatively high unit cost. No one has adopted a dual-function electrolytic cell design strategy with manganese as the electrocatalyst and formaldehyde as the oxidizing molecule.

[0004] In view of the above technical problems, the present invention provides a method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst.

[0005] 2. Technical solution: A method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst comprises the following steps: S1: a certain amount of KMnO4 and MnSO4 are dissolved in a certain amount of deionized water in turn, transferred to an autoclave, a current collector is added to the solution, heated in an oven for a certain period of time, cooled, washed and dried to obtain a manganese-based electrocatalyst; S2: Electrodes are made using the manganese-based electrocatalyst prepared in S1 as material; S3: A two-electrode system was constructed using the electrodes made of S2 as cathode and anode, and a formaldehyde-based electrolytic cell was constructed using a KOH / HCHO mixed solution as electrolyte, and a certain voltage was applied for electrolysis.

[0006] Furthermore, the oven temperature of S1 is set to 180°.

[0007] Furthermore, the oven heating time of S1 is 24h.

[0008] Furthermore, the mass ratio of KMnO4 and MnSO4 of S1 is 65:13.

[0009] Furthermore, the mass volume ratio of KMnO4 and deionized water in S1 is 0.65 g:35 mL.

[0010] Furthermore, the current collector is nickel foam.

[0011] Furthermore, when the KOH / HCHO mixed solution is used as the electrolyte, the ratio of KOH to HCHO is 1 mol / L: 10 mg·L -1 .

[0012] Furthermore, the voltage of S3 is 1.8V.

[0013] 3. Beneficial effects: The manganese-based electrocatalyst of the present invention shows excellent electrocatalytic activity comparable to that of precious metals. The manganese-based bifunctional electrolytic cell design significantly increases the current density of the anodic oxidation reaction compared with the traditional water-based electrolytic cell, especially when 10 mg L- -1Under HCHO conditions, the current density of the formaldehyde oxidation reaction is 2.6 times that of the water oxidation reaction. The two-electrode test results show that at a current density of 10 mAcm -2 The formaldehyde-based electrolytic cell can save about 8.7% of electricity. This means that the same amount of hydrogen can be produced by saving about 8.7% of electricity. At the same time, 5 mg / L and 10 mg / L formaldehyde were degraded by 11.6% and 20.2% in the system, respectively. The above results show that the design of this electrolytic cell effectively improves the efficiency of hydrogen production by electrolysis of water and degrades formaldehyde harmful pollutants in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The X-ray diffractometer (XRD) image and morphology image of the manganese-based electrocatalyst successfully prepared in Example 1.

[0015] Figure 2 This is a comparative image of the electrocatalytic performance of the electrocatalyst prepared in Example 1 under electrolysis conditions of different formaldehyde concentration molecules.

[0016] Figure 3 The electrocatalyst prepared in Example 1 is used to compare the performance of a formaldehyde-based electrolyzer and a water-based electrolyzer constructed with a formaldehyde concentration of 10 mg / L. The figure on the right is a diagram of formaldehyde degradation efficiency. DETAILED DESCRIPTION

[0017] The present invention will be described in detail below with reference to the accompanying drawings.

[0018] Embodiment 1: Under magnetic stirring, 0.65 g KMnO4 and 0.13 g MnSO4 were dissolved in 35 mL of deionized water. The solution was then transferred to a 50 mL autoclave, and the current collector nickel foam (NF: 2 cm×4 cm) was added to the solution. The oven temperature was set to 180°C and the heating time was 24 hours. After reacting for 24 hours, the mixture was naturally cooled to room temperature and washed and dried. The obtained sample was subjected to XRD crystal phase test.

[0019] like Figure 1 As shown in a, the characteristic peaks of the standard card PDF#52-0556 match well and no impurity peaks are detected, indicating that the pure phase K 0.27 The MnO2·0.54H2O material was successfully prepared without any other impurities. Figure 1 b and Figure 1 The electron microscope of c revealed the morphological characteristics of the material, which is mainly composed of ultra-thin nanosheets, confirming that its structure is ultra-thin nano-shaped.

[0020] Test Example 1: The test process is as follows: the electrode material prepared in Example 1 is further made into an electrode, and formaldehyde solutions of different concentrations are added to 1 mol / L KOH as an electrolyte solution, and the effect of formaldehyde concentration on the electrocatalytic activity of the sample is measured in a three-electrode system.

[0021] The results are as follows: like Figure 2 As shown in a, the current density is greatly improved after the addition of formaldehyde, and at the same voltage, the current density increases with the increase of the formaldehyde concentration.

[0022] like Figure 2 As shown in b, when the voltage is -0.15 V and -0.2 V respectively ( Figure 2 b) The current densities under 1 mol·L-1 KOH conditions are 4.99 and 7.56 mA·cm -2 ; 1 mol·L -1 KOH+2 mg·L -1 The current densities under HCHO conditions were 13.29 and 31.07 mA cm -2 ; 1 mol·L -1 KOH+5 mg·L -1 The current densities under HCHO conditions were 25.39 and 65.03 mA·cm -2 ; 1 mol·L -1 KOH+10 mg·L -1 The current densities under HCHO conditions reached 24.86 and 73.9 mA·cm -2 .

[0023] In addition, the oxygen evolution reaction performance of the samples in 1 mol / L KOH with different concentrations of formaldehyde solution was evaluated. Figure 2 As shown in Figure c, with the addition of formaldehyde, the electrode exhibits a higher current density and a lower starting potential. The starting potential of the formaldehyde oxidation reaction is 1.61 V (vs. RHE). Under the same conditions, the minimum potential required for the water oxidation reaction is 1.66 V (vs. RHE), indicating that formaldehyde oxidation is easier to occur than water oxidation.

[0024] like Figure 2 As shown in d, when the voltage reaches 1.7 and 1.75 V (vs. RHE), 1 mol·L -1 The anodic current densities under KOH conditions were 51.08 and 125.74 mA·cm -2 ; 1 mol·L -1 KOH+2 mg·L -1The anodic current densities under HCHO conditions were 79.69 and 171.54 mA·cm -2 ; 1 mol·L -1 KOH+5 mg·L -1 The anodic current densities under HCHO conditions were 98.39 and 203.18 mA·cm -2 ; ; 1 mol·L -1 KOH+10 mg·L -1 The anodic current densities under HCHO conditions were 130.46 and 266.67 mA·cm -2 In particular, when 10 mg·L-1 HCHO was added at 1.7 V (vs. RHE), the current density of the formaldehyde oxidation reaction was 2.6 times that of the water oxidation reaction, indicating that the addition of formaldehyde can improve the electrocatalytic activity of the prepared electrode sample.

[0025] Test Example 2: The test process is as follows: the electrode material prepared in Example 1 is further made into electrodes, which are used as cathode and anode respectively. The optimal formaldehyde concentration (10 mg / L) obtained in Test Example 1 is selected to construct a formaldehyde-based electrolytic cell. On this basis, a certain voltage is applied to conduct an electrocatalytic performance test.

[0026] The results are as follows: Figure 3 a shows the polarization curve of the electrolytic cell based on formaldehyde oxidation reaction and water oxidation reaction. It can be seen that compared with 1M KOH+10 mg·L -1 Compared with HCHO as the electrolyte solution, if a specified current density value is to be achieved, 1 M KOH as the electrolyte requires a higher voltage condition. This indicates that the cell voltage of the formaldehyde-based electrolytic cell designed in this study has decreased. At 10 mA·cm -2 At a current density of , the cell voltage with 1 M KOH as the electrolyte was 1.782 V; while 1 M KOH + 10 mg·L -1 The cell voltage of the formaldehyde-based electrolytic cell of HCHO is 1.627 V. Compared with the former, it is 0.155 V lower, which means that after adding formaldehyde, the cell voltage is reduced by 8.7%, indicating that the formaldehyde-based electrolytic cell can save some electrical energy when achieving the same hydrogen production efficiency.

[0027] In addition, under the condition of electrolyte solution containing formaldehyde, a constant voltage of 1.8 V was applied to carry out formaldehyde concentration degradation test, that is, the absorbance value of the generated yellow substance before and after degradation was measured at the maximum absorption wavelength of 414 nm by acetylacetone spectrophotometry, and the degradation rate was further calculated. Figure 3As shown in Figure b, formaldehyde at concentrations of 5 mg / L and 10 mg / L was degraded by 11.6% and 20.2% in the system, respectively, indicating that formaldehyde can be effectively degraded by this electrolysis system. Therefore, this design not only effectively degrades formaldehyde pollutants, but also greatly improves the efficiency of hydrogen production and significantly reduces the cost of hydrogen production. This design provides a new idea for large-scale industrial hydrogen production.

[0028] Although the present invention has been disclosed as above in terms of preferred embodiments, they are not intended to limit the present invention. Anyone skilled in the art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims of this application.

Claims

1. A method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst, characterized in that: The following steps are involved: S1: a certain amount of KMnO4 and MnSO4 are dissolved in a certain amount of deionized water in sequence, transferred to an autoclave, a current collector is added to the solution, heated in an oven for a certain period of time, cooled, washed and dried to obtain a manganese-based electrocatalyst; S2: Electrodes are made using the manganese-based electrocatalyst prepared in S1 as material; S3: A two-electrode system was constructed using the electrodes made of S2 as cathode and anode, and a formaldehyde-based electrolytic cell was constructed using a KOH / HCHO mixed solution as electrolyte, and a certain voltage was applied for electrolysis.

2. The method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst according to claim 1, characterized in that: The oven temperature of S1 was set to 180°.

3. The method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst according to claim 2, characterized in that: The oven heating time of S1 is 24h.

4. A method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst according to any one of claims 1 to 3, characterized in that: The mass ratio of KMnO4 and MnSO4 in S1 is 65:

13.

5. The method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst according to claim 4, characterized in that: The mass volume ratio of KMnO4 and deionized water in S1 is 0.65g:35mL.

6. The method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst according to claim 5, characterized in that: The current collector is nickel foam.

7. The method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst according to claim 1 or 6, characterized in that: When the KOH / HCHO mixed solution is used as the electrolyte, the ratio of KOH to HCHO is 1 mol / L:10 mg·L -1 .

8. The method for constructing an electrolytic cell for producing hydrogen and synergistically degrading formaldehyde wastewater based on a manganese-based electrocatalyst according to claim 7, characterized in that: The voltage of S3 is 1.8V.

Images