MnO / CeO2-C (t) electrocatalyst for two-electron oxygen reduction and preparation method of MnO / CeO2-C (t) electrocatalyst

Abstract

The invention discloses a MnO / CeO2-C (t) electrocatalyst for two-electron oxygen reduction and a preparation method of the MnO / CeO2-C (t) electrocatalyst. The preparation method comprises the following steps: dispersing TPA and Ce (NO3) 26H2O in a specific molar ratio in a mixed solution containing DMF and DI in a specific volume ratio, and carrying out stirring, ultrasonic treatment, hydrothermal reaction, centrifugation and drying to obtain an MIL-53 (Ce) precursor; the MnO / CeO2-C (500) is obtained by calcining the MnO / CeO2, dipping the MnO / CeO2-C (500) in an ethanol solution containing manganese salt, drying by distillation and further calcining, and meanwhile, physically mixing MnO and CeO2 as a contrast. After hydrophobic carbon paper is treated, ink containing a catalyst, naphthol, IPA and DI in a specific proportion is coated on the hydrophobic carbon paper. In a standard three-electrode system and an H-type reactor with a proton exchange membrane, the electrocatalyst can be used for synthesizing H2O2 through an electrocatalytic reaction under specific conditions, has good selectivity and stability, has a good application prospect in the field of electrocatalytic synthesis of H2O2, and provides an efficient electrocatalyst preparation and application scheme for related fields.

Description

Technical Field

[0001] The present invention relates to a MnO / CeO2-C (t) Electrocatalyst and method for preparing the same. Background Art

[0002] Hydrogen peroxide (H2O2) is a clean and mild oxidant with the advantages of the highest active oxygen content, excellent effect in a wide pH range, and non-toxic byproducts (only H2O and O2) produced during the reaction. It has been widely used in various industrial fields such as bleaching, mining and metal processing, detergent applications, wastewater treatment, and chemical organic synthesis. However, from the perspective of global public health safety, meeting the large demand for hydrogen peroxide is challenging.

[0003] Common catalysts for the electrocatalytic two-electron ORR synthesis of H2O2 mainly include precious metal catalysts, single-atom catalysts, transition metal catalysts and carbon-based catalysts. Among them, transition metals have many advantages as electrocatalysts, such as adjustable oxidation state and strong redox ability, high reactivity and selectivity, good conductivity and controllable nanostructure. The most important thing is that compared with precious metal catalysts, their cost is relatively low and their resources are abundant. Rare earth metal oxides have been widely used as co-catalysts to improve the electrocatalytic performance of transition metal active components. Combining two metal oxide catalysts can regulate the active sites and coordination environment through the interaction between the metal oxides, so that the catalyst can better capture oxygen molecules and adjust the adsorption strength of *OOH intermediates, thereby promoting the efficient synthesis of H2O2. Therefore, this paper uses cerium-based carbon materials loaded with transition metal oxides as catalysts, and uses 2e - ORR reaction produces H2O2, and a green and efficient method for preparing H2O2 was invented. Summary of the invention

[0004] The present invention aims to develop a rod-shaped MnO / CeO2-C catalyst for electrocatalytic production of H2O2. (t) The preparation method of the material makes the catalyst in 2e - Excellent H2O2 selectivity was achieved during the ORR process.

[0005] A MnO / CeO2-C (t)The preparation method of the catalyst material is specifically carried out in the following steps: 1) The synthesis of the MIL-53 (Ce) precursor is to disperse TPA and Ce (NO3) 2·6H2O in a certain proportion into a 60 ml mixed solution containing DMF and DI, stir the mixture for 30 minutes to make it uniformly dispersed, and then ultrasonicate it until it is completely dissolved. The solution is transferred to a 100 ml polytetrafluoroethylene stainless steel autoclave and maintained in a hydrothermal oven at a reaction temperature of 100 ° C for 20 hours. After the reaction is completed, the product is collected by centrifugation at a speed of 8000r in deionized water and anhydrous ethanol. The collected sample is dried in an oven at 60°C for 12 hours to obtain a white powder solid sample, that is, the MIL-53 (Ce) precursor is obtained; 2) The MIL-53 (Ce) precursor obtained in the previous step is evenly spread in a covered corundum porcelain boat, placed in a tube furnace, and after exhausting the air, it is heated to 500°C at a heating rate of 3°C / min and kept warm for 2 hours. After the heating is completed, it is cooled to room temperature and the carbonized sample is taken out to obtain MIL-53 (Ce) derived carbon, called CeO2-C (500) ; 3) Weigh 0.1 g Ce-C (500) The composite precursor was prepared by dispersing Mn2(CH3COO)·3H2O in a mass ratio of 2:1 into 30 ml of IPA solution and ultrasonically dissolving it. After stirring for 30 min in a water bath at 80 °C, the sample was allowed to stand for 48 h. The sample was then collected by filtration and dried in an oven at 60 °C to obtain a composite precursor. The composite precursor was placed in a tubular furnace and heated to 500 °C at a heating rate of 3 °C / min and kept warm for 1 h. After heating, it was cooled to room temperature and the sample was taken out and called MnO / CeO2-C (500) .

[0006] The present invention has the following beneficial effects.

[0007] 1. MnO / CeO2-C prepared by the method of the present invention (500) 1:2 cathode catalyst material, by carbonizing CeMOF to obtain a rough carbon-containing carrier so that the metal oxide can be better composited on the surface, making up for the 2e - The disadvantage of poor conductivity of ORR catalysts is that 2e with better conductivity and higher H2O2 selectivity is obtained. - ORR catalyst.

[0008] 2. MnO / CeO2-C prepared by the present invention (500) A series of performance tests of the 1:2 cathode catalyst material showed that the H2O2 selectivity can reach over 98%, and the electron transfer number is close to 2. In the H-type electrolytic cell test, the Faraday efficiency was 86.78%, and the H2O2 yield was 6.8 mol h -1 g cat -1 , with excellent ORR activity.

[0009] 3. MnO / CeO2-C prepared by the method of the present invention (500) The carbonization temperature of the 1:2 cathode catalyst material only needs to reach 500°C, which is relatively low compared to the carbonization temperatures required for other similar materials. During the entire preparation process, energy consumption can be effectively controlled, which is more in line with the pursuit of energy conservation in modern industrial production, has good economic and environmental benefits, and provides strong support for the sustainable development of related industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is (a) MIL-53(Ce) precursor, (b) CeO2-C (500) and (c) MnO / CeO2-C (500) 1:2 SEM images, (b), (d), and (f) are local enlarged images of the catalysts in the three stages, respectively.

[0011] Figure 2 (a) MnO / CeO2-C (500) XRD spectra of 1:10 / 1:5 / 1:2 / 1:1 / Physical blending.

[0012] Figure 3 (a) MnO / CeO2-C (500) and (b) MnO / CeO2-C (500) 1:2 XPS spectrum.

[0013] Figure 4 (a) MnO / CeO2-C (500) 1:2 Peak separation of Ce 3d orbitals and (b) Ce surface before and after loading 3+ Concentration graph.

[0014] Figure 5 MnO / CeO2-C (500) CV curves of 1:10 / 1:5 / 1:2 / 1:1 / Physical blending, graph of the number of transferred electrons n, and H2O2 selectivity.

[0015] Figure 6 MnO / CeO2-C (500) Faradaic efficiency and H2O2 yield of 1:10 / 1:5 / 1:2 / 1:1 / Physical blending.

[0016] Figure 7 MnO / CeO2-C (500) 1:2 as a 10h stability test chart of the catalyst.

[0017] Figure 8 MnO / CeO2-C (500) 1:2 on-site photo of the H-type electrolytic cell. DETAILED DESCRIPTION

[0018] Example 1 MnO / CeO2-C (t) The preparation method of the oxygen reduction reaction catalyst material is specifically carried out according to the following steps.

[0019] 1) Disperse TPA and Ce(NO3)2·6H2O in a certain proportion into a 60ml mixed solution containing DMF and DI, stir the mixture for 30 minutes to make it evenly dispersed, and then ultrasonicate it until it is completely dissolved. Transfer the solution to a 100ml polytetrafluoroethylene stainless steel autoclave and keep it in a hydrothermal oven at a reaction temperature of 100°C for 20 hours. After the reaction is completed, the product is collected by centrifugation at a speed of 8000r in deionized water and anhydrous ethanol. The collected sample is dried in an oven at 60°C for 12 hours to obtain a white powder solid sample, that is, the MIL-53(Ce) precursor is obtained; 2) The MIL-53(Ce) precursor obtained in the previous step is evenly spread in a covered corundum porcelain boat, placed in a tube furnace, and after exhausting the air, it is heated to 500°C at a heating rate of 3°C / min and kept warm for 2 hours. After the heating is completed, it is cooled to room temperature, and the carbonized sample is taken out to obtain MIL-53(Ce) derived carbon, called CeO2-C (500) ;3) Weigh 0.1g CeO2-C (500) and Mn2(CH3COO)·3H2O with a mass ratio of 2:1 were dispersed in 30 ml of IPA solution and dissolved by ultrasound. After stirring for 30 min in a water bath at 80 °C, the sample was allowed to stand for 48 h. The sample was then collected by filtration and dried in an oven at 60 °C to obtain a composite precursor. 4) The composite precursor was placed in a tubular furnace and heated to 500 °C at a heating rate of 3 °C / min and kept warm for 1 h. After heating, it was cooled to room temperature and the sample was taken out and called MnO / CeO2-C (500) .

[0020] Example 2 MnO / CeO2-C (500) 1:10 The specific steps are as follows: Steps 1) and 2) are the same as those in Example 1, except that step 3) is: weigh 0.1 g CeO2-C (500) The precursor was prepared by dispersing Mn2(CH3COO)·3H2O with a mass ratio of 10:1 into 30 ml of IPA solution and ultrasonicating until dissolved. The mixture was stirred for 30 min in a water bath at 80 °C and then allowed to stand for 48 h. The sample was then collected by filtration and dried in an oven at 60 °C to obtain a composite precursor. (500) =1:10.

[0021] Example 3 MnO / CeO2-C (500) 1:5 The specific steps are as follows: Steps 1) and 2) are the same as those in Example 1, except that step 3) is: weigh 0.1 g CeO2-C (500) The precursor was prepared by dispersing Mn2(CH3COO)·3H2O with a mass ratio of 5:1 into 30 ml of IPA solution and ultrasonicating until dissolved. The mixture was stirred for 30 min in a water bath at 80°C and then allowed to stand for 48 h. The sample was then collected by filtration and dried in an oven at 60°C to obtain a composite precursor. (500) =1:5.

[0022] Example 4 MnO / CeO2-C (500) 1:1Specifically, the following steps are performed: Steps 1) and 2) are the same as those in Example 1, except that step 3) is: weigh 0.1 g CeO2-C (500) The precursor was prepared by dispersing Mn2(CH3COO)·3H2O in a mass ratio of 1:1 into 30 ml of IPA solution and ultrasonicating until dissolved. The mixture was stirred for 30 min in a water bath at 80 °C and then allowed to stand for 48 h. The sample was then collected by filtration and dried in an oven at 60 °C to obtain a composite precursor. (500) =1:1.

[0023] Example 5 The catalyst obtained in the above manner was subjected to ORR electrochemical test using an electrochemical workstation (CHI760E, Shanghai Chenhua Instrument Co., Ltd.) to verify its catalytic performance. The test used 0.1 M KOH (alkaline) as the electrolyte solution, a saturated calomel electrode as the reference electrode, and a platinum wire as the counter electrode.

[0024] Preparation of electrochemical working electrode: 5.0 mg of catalyst was weighed and mixed with 100 μL of ethanol and 50 μL of naphthol and ultrasonicated for 30 min to prepare a uniform catalyst ink. 4 μL of the above ink was evenly coated on the glassy carbon electrode to obtain a loading of 0.1 mg. The glassy carbon area of ​​the rotating disk electrode and the rotating ring disk electrode was the same. The ORR performance of the catalyst was evaluated using a rotating disk electrode in an O2-saturated 0.1 M KOH solution using an electrochemical workstation (CHI760E, Shanghai Chenhua Instrument Co., Ltd.).

[0025] The catalytic materials of specific examples 1 to 4 and their corresponding characterization and performance analysis.

[0026] Figure 1The SEM image shows that the surface of the MIL-53 (Ce) precursor is relatively smooth. After carbonization at a certain temperature, the surface of the material presents a rough structure. The roughness of the surface means that the metal oxides loaded later will be more firmly compounded on the surface of the material. After loading MnO, the material forms a heterogeneous structure. The carbonized MOF carrier itself exposes more active sites to the electrolyte and oxygen. After combining with the MnO on the surface, the utilization of oxygen forms a step-by-step conversion, thereby enhancing the ORR reaction kinetics.

[0027] Figure 2 This is the XRD diagram. In the figure, it can be observed that the diffraction peaks of the series of samples are completely corresponding to the standard cards of MnO and CeO2, proving the successful synthesis of MnO and CeO2 in the material.

[0028] Figure 3 Figure 2 is the XPS spectrum of the sample before and after loading. From the overall spectrum, we can observe C peak, O peak, Ce peak and Mn peak, which proves the successful introduction of Mn.

[0029] Figure 4 For Example 1, the peak area of ​​the Ce 3d orbital of the material was calculated and the MnO / CeO2-C (500) 1:2 surface Ce 3+ The concentration is higher than CeO2-C (500) , indicating that the oxygen vacancy content of the loaded material is higher, which is more conducive to the occurrence of 2e-ORR.

[0030] Figure 5 The CV curves, the number of transferred electrons and the H2O2 selectivity of Examples 1 to 4 in 0.1M KOH are shown in the figure. As shown in the figure, the series of materials have a reduction peak between 0.6-0.65V, which symbolizes ORR, and the peak position is higher than that of the physical mixed catalyst, which proves that physical mixing cannot cause the synergistic effect of the two. Only after chemical loading treatment can the synergistic effect be achieved. - ORR has a positive effect, increasing by 2e - ORR activity. The hydrogen peroxide selectivity of MnO / CeO2-C(500) 1:2 reached more than 90% in a wide potential range, and the number of transferred electrons was closest to 2. According to the Sabatier principle, the coordination of the two active sites of the catalyst with a loading of 1:2 is close to the optimal ratio, and its 2e - The ORR performance is the best.

[0031] Figure 6 The Faraday efficiency and H2O2 yield of Examples 1 to 4 are shown in the figure. (500)The Faradaic efficiency of 1:2 reached 90.91%, and the H2O2 yield reached 6.8 mol h -1 g cat -1 It is significantly better than other samples, indicating that this sample has excellent catalytic performance with high activity.

[0032] Figure 7 This is a 10-hour stability test diagram of Example 1 as a catalyst. From the figure, it can be observed that the stability of the catalyst reaches 90.91% in the 10-hour IT test, proving that the catalyst has good stability under chemical compound conditions.

[0033] Figure 8 4 is a site diagram of the H-type electrolytic cell of Example 1.

Claims

1. A MnO / CeO2-C (t) A method for preparing an electrocatalyst, characterized in that The catalyst was prepared by the following steps: 1) TPA and Ce(NO3)2·6H2O were dispersed in a certain proportion into 60 ml of a mixed solution containing DMF and DI, the mixture was stirred for 30 min to make it uniformly dispersed and then ultrasonicated until it was completely dissolved. The solution was transferred to a 100 ml polytetrafluoroethylene stainless steel autoclave and kept in a hydrothermal oven at a reaction temperature of 100°C for 20 h. After the reaction is completed, the product is collected by centrifugation at a speed of 8000r in deionized water and anhydrous ethanol. The collected sample is dried in an oven at 60°C for 12 hours to obtain a white powder solid sample, that is, the MIL-53 (Ce) precursor is obtained; 2) The MIL-53 (Ce) precursor obtained in the previous step is evenly spread in a covered corundum porcelain boat, placed in a tube furnace, and after exhausting the air, it is heated to 500°C at a heating rate of 3°C / min and kept warm for 2 hours. After the heating is completed, it is cooled to room temperature and the carbonized sample is taken out to obtain MIL-53 (Ce) derived carbon, called CeO2-C (500) ; 3) Weigh 0.1g Ce-C (500) and Mn2(CH3COO)·3H2O with a mass ratio of 2:1 were dispersed in 30 ml of IPA solution and dissolved by ultrasound. After stirring for 30 min in a water bath at 80 °C, the mixture was allowed to stand for 48 h. The sample was then collected by filtration and dried in an oven at 60 °C to obtain a composite precursor. 4) 0.1 g Ce-C (500) and Mn2(CH3COO)·3H2O with a mass ratio of 2:1 were dispersed in 30 ml of IPA solution and dissolved by ultrasound. After stirring for 30 min in a water bath at 80 °C, the mixture was allowed to stand for 48 h. The sample was then collected by filtration and dried in an oven at 60 °C to obtain a composite precursor. 5) MnO and CeO2-C (500) Physical blending was performed in a certain proportion, which was named Physical blending; 6) The hydrophobic carbon paper was cut into 1x2cm size, and ultrasonicated with ACE, DI, and EtOH for 20min respectively to remove the surface oil, and finally dried in an oven at 60℃ for 1h. (t) After preparing naphthol, IPA and DI in a certain proportion, ultrasonicate for 1 hour to make them evenly dispersed, and draw a certain amount of ink and evenly coat it on carbon paper.

2. The method for preparing a catalyst according to claim 1, characterized in that In step 1), the molar ratio of TPA:Ce(NO3)2·6H2O is 1:

2.

3. The method for preparing a catalyst according to claim 1, characterized in that In step 1), the volume ratio is DMF:DI=5:

1.

4. The method for preparing the catalyst according to claim 1, characterized in that In step 2), the calcination process is to increase the temperature from room temperature to 350°C / 400°C / 450°C / 500°C / 650°C / 800°C at a heating rate of 3°C / min, and calcine at a constant temperature for 2 hours.

5. The method for preparing the catalyst according to claim 1, characterized in that In step 3), by mass ratio, Mn2(CH3COO)·3H2O:Ce-C (500) =1:10 / 1:5 / 1:

1.

6. The method for preparing the catalyst according to claim 1, characterized in that In step 5), by mass ratio, MnO:CeO2-C (500) =1:2.

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