A method for ultra-fast preparation of noble metal-loaded metal oxide electrocatalysts

Abstract

The present invention relates to the field of preparation of electrochemical materials, and discloses a method for rapidly preparing a noble metal-supported metal oxide electrocatalyst, which comprises the following steps: S1: Weigh solid particles of chloroplatinic acid hexahydrate in deionized water, and fully stir and dissolve to form a Pt precursor solution; S2: Drop the Pt precursor solution onto MoO3 powder, and then place it in an oven for drying; S3: Grind and mix the dried powder and carbon black with a pestle and mortar to obtain a black precursor powder; S4: Heat the precursor powder in an inert atmosphere to obtain a heterostructure electrocatalyst with Pt nanoparticles supported on molybdenum oxide. The electrocatalyst synthesized by the preparation method disclosed in the present invention has a heterostructure. The emergence of the heterostructure can effectively reduce the charge transfer resistance of the catalyst during the catalytic reaction process, and fully expose the reaction active sites, which is beneficial to improving the catalytic activity. The present invention is of great significance for promoting the development of efficient and green hydrogen production.

Description

Technical Field

[0001] The present invention relates to the field of preparation of electrochemical materials, and more specifically, to a method for ultrafast preparation of a noble metal-loaded metal oxide electrocatalyst. Background Art

[0002] The excessive consumption of fossil fuels and the severe climate change caused by a large amount of carbon emissions are becoming increasingly serious. The global energy structure is facing a transformation from traditional fossil energy to clean and efficient energy. Hydrogen energy is a green and clean energy with characteristics such as high calorific value, zero carbon emissions, and wide application, and is considered to be one of the most promising energy sources leading the clean energy transformation in the 21st century. The methods for producing hydrogen include coal gasification, natural gas cracking, biological hydrogen production, and electrolytic water hydrogen production. Among them, electrolytic water hydrogen production is considered to be the most potential hydrogen production method due to its advantages of environmental friendliness, flexible production, and high product purity. However, due to the high reaction potential of the hydrogen evolution reaction in the electrolytic water hydrogen production process and the low electrolytic hydrogen production efficiency, it is difficult to be applied to large-scale industrial production. How to improve the efficiency of electrolytic water hydrogen production and reduce costs has become an urgent problem to be solved in the field of electrolytic water hydrogen production.

[0003] A suitable electrocatalyst can accelerate the electrode reaction, increase the reaction rate, and reduce the overpotential required for the reaction to occur. Currently, Pt-based catalysts are still the most effective catalysts in the electrolytic water hydrogen production reaction process. However, the low reserves, high price of Pt, and the long preparation time and high energy consumption for current preparation of Pt-based catalysts make it difficult to produce Pt-based catalysts on a large scale. Transition metal oxides have relatively good performance in the hydrogen evolution reaction, and when used as a carrier, they often regulate the electronic structure of the metal (Pt) through the interaction between the metal (Pt) and the carrier, so that the hydrogen evolution performance can reach or even exceed that of commercial catalysts under the condition of low noble metal (Pt) loading. Therefore, the rapid and efficient synthesis of advanced Pt-loaded transition metal oxide electrocatalysts is the key to achieving a breakthrough in electrolytic water hydrogen production.

[0004] Researchers have conducted extensive research on the use of transition metal oxide-supported Pt nanoparticles to catalyze the hydrogen evolution reaction. Among them, MoO 3 as a carrier can effectively regulate the electronic structure of Pt, thereby improving its hydrogen evolution performance. However, the synthesis of the above catalysts usually has problems of long preparation time and high energy consumption. In addition, considering that the heterostructure can effectively utilize the interaction and synergistic effect between different components, we propose to use an ultrafast Joule heating synthesis method to heat the precursor to the required temperature within a few seconds, so as to obtain a metal molybdenum oxide electrocatalyst loaded with Pt particles having a heterostructure. Summary of the Invention

[0005] The present invention provides a method for ultra-fast preparation of a noble metal-supported metal oxide electrocatalyst, which can be directly used as an electrocatalyst for hydrogen production by acidic electrolytic water, having excellent HER catalytic activity and high stability. Moreover, the preparation method has an extremely short time, is simple and controllable, and has low cost.

[0006] The present invention provides a method for ultra-fast preparation of a noble metal-supported metal oxide electrocatalyst, comprising the following steps:

[0007] S1: Weigh solid particles of chloroplatinic acid hexahydrate in deionized water, and stir well to dissolve to form a Pt precursor solution;

[0008] S2: Drop the Pt precursor solution obtained in step S1 onto MoO 3 powder, and then place it in an oven for drying;

[0009] S3: Grind and mix the dried powder obtained in step S2 with carbon black using a pestle and mortar to obtain a black precursor powder;

[0010] S4: Weigh the precursor powder obtained in step S3, sandwich it with two pieces of carbon paper, put it in a quartz tube, and then place it in a Joule heating device to heat in an inert atmosphere, finally obtaining a heterostructure electrocatalyst with Pt nanoparticles supported on molybdenum oxide.

[0011] Preferably: In step S1, the molar concentration of the obtained Pt precursor solution is 10 mmol / L.

[0012] Preferably: In step S2, the ratio of the amount of the Pt precursor solution added to MoO 3 powder is: the molar ratio of Pt:Mo = 5:100, and the drying temperature is 40°C - 50°C.

[0013] Preferably: In step S3, the mass of carbon black added is the same as the mass of MoO 3 powder, and the grinding time is 20 - 30 min.

[0014] Preferably: In step S4, each time the weighed precursor powder is 30 - 50 mg, the size of the carbon paper is 5 cm in length and 2 cm in width, and the size of the quartz tube is 3.6 cm in length, 2 cm in inner diameter, and 2.2 cm in outer diameter.

[0015] Preferably: In step S4, the inert atmosphere is Ar gas.

[0016] Preferably: In step S4, the heating voltage of the Joule heating device is 15 - 22 V, the heating time is 0.5 - 1 s, the number of heating times is 8 times, and after each heating, it cools down and waits for about 9 s before the next heating.

[0017] The beneficial effects of the present invention are as follows: The present invention discloses a method for ultra-fast preparation of a noble metal-loaded metal oxide electrocatalyst, which has a very short preparation time, high heat utilization rate, and low cost;

[0018] The synthesized noble metal nanoparticle-loaded transition metal molybdenum oxide electrocatalyst has a heterostructure. The emergence of the heterostructure can effectively reduce the charge transfer resistance of the catalyst during the catalytic reaction, and the interaction between the metal and the support can rearrange the surface metal charges; the synergistic effect of the heterostructure and the metal-support interaction can effectively improve the activity of the electrocatalyst for the hydrogen evolution reaction.

[0019] This application can achieve rapid pyrolysis, avoiding obvious agglomeration of electrocatalyst particles caused by long-term heating, improving the atomic utilization rate of noble metals, greatly reducing the noble metal loading while ensuring catalytic activity, reducing costs, and having certain prospects for application in large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the X-ray diffraction (XRD) pattern of MoOx-F and Pt / MoOx-F in the present invention;

[0021] Figure 2 is the X-ray diffraction (XRD) pattern of Pt / MoO 3 、Pt / MoOx-F, Pt / MoO 2 synthesized under different voltage conditions in the present invention;

[0022] Figure 3 is the high-resolution transmission electron microscope (HRTEM) image of MoOx-F in the present invention;

[0023] Figure 4 is the high-resolution transmission electron microscope (HRTEM) image of Pt / MoOx-F in the present invention;

[0024] Figure 5 is the linear sweep voltammetry (LSV) performance graph of the hydrogen evolution reaction of the electrocatalyst prepared by Joule heating in Examples 2-5 of the present invention.

[0025] Figure 6 is the mass activity graph of the materials prepared in Examples 2, 4, and 5 of the present invention at an overpotential (relative to the hydrogen standard) of 50 mV. DETAILED DESCRIPTION OF THE INVENTION

[0026] Reference will now be made to exemplary embodiments to discuss the subject matter described herein. It should be understood that discussing these embodiments is only to enable those skilled in the art to better understand and thus implement the subject matter described herein. Without departing from the scope of protection of the content of this specification, changes can be made to the functions and arrangements of the elements discussed. Each example can omit, substitute, or add various processes or components as needed. Additionally, the features described relative to some examples can also be combined in other examples.

[0027] Example 1

[0028] In this embodiment, a method for ultra-fast preparation of a noble metal-loaded metal oxide electrocatalyst is proposed, including the following steps:

[0029] S1: Weigh solid particles of chloroplatinic acid hexahydrate in deionized water, and stir well to dissolve to form a Pt precursor solution; the molar concentration of the obtained Pt precursor solution is 10 mmol / L.

[0030] S2: Drop the Pt precursor solution obtained in step S1 onto MoO 3 powder, and then place it in an oven for drying;

[0031] The ratio of the amount of the added Pt precursor solution to the MoO 3 powder is: the molar ratio of Pt:Mo = 5:100. The drying temperature can be selected as 40 °C or 45 °C or 50 °C in this embodiment, and 40 °C is preferred in this embodiment.

[0032] S3: Grind and mix the dried powder obtained in step S2 with carbon black using a pestle and mortar to obtain a black precursor powder; the mass of the added carbon black is the same as the mass of the MoO 3 powder. The grinding time can be selected as 20 min or 25 min or 30 min in this embodiment, and 30 min is preferred in this embodiment.

[0033] S4: Weigh the precursor powder obtained in step S3, sandwich it with two pieces of carbon paper, put it in a quartz tube, and then place it in a Joule heating device to be heated in an inert atmosphere, finally obtaining a heterostructure electrocatalyst with Pt nanoparticles loaded on molybdenum oxide;

[0034] The weight of the precursor powder weighed each time can be selected as 30 mg or 40 mg or 50 mg in this embodiment, 50 mg is preferred in this embodiment. The size of the carbon paper is 5 cm in length and 2 cm in width, and the size of the quartz tube is 3.6 cm in length, 2 cm in inner diameter, and 2.2 cm in outer diameter;

[0035] The inert atmosphere is Ar gas;

[0036] The heating voltage of the Joule heating device can be selected as 15V, 20V or 22V in this embodiment, and 20V is preferred in this embodiment. The heating time can be selected as 0.5s, 0.7s or 1s in this embodiment, and 1s is preferred in this embodiment. The number of heating times is 8 times. After each heating, wait about 9s for cooling and then conduct the next heating.

[0037] Example 2

[0038] In this embodiment, the Pt / MoOx-F electrocatalyst is prepared as follows:

[0039] S1: Accurately weigh 0.518g of H 2 PtCl 6 ·6H 2 O particles, stir and dissolve them in 100 mL of deionized aqueous solution to form a 0.01 mol / L Pt precursor solution.

[0040] S2: Add the Pt precursor solution (17.35 mL) containing 1.735×10 3 mol Pt to 500 mg of MoO -4 (0.00347 mol) powder. Subsequently, place the crucible containing the above sample in an oven at 40℃ - 50℃ for drying.

[0041] S3: Mix the dried powder obtained in step S2 with 500 mg of carbon black, and grind it with a pestle and mortar for 20 - 30 min to obtain the Pt precursor powder.

[0042] S4: Take 30 - 50 mg of the Pt precursor powder obtained in step S3 and compact it between two pieces of carbon paper with a size of 5 cm×2 cm (length×width). Subsequently, place the carbon paper with the sample in a quartz tube. The carbon paper is longer than the quartz tube, so that about 0.6 cm of carbon paper is exposed on both sides of the quartz tube. The edge of the carbon paper is placed on the Cu electrodes on both sides of the Joule heating device and clamped with Cu electrode pieces to complete the sample loading process. Then, conduct Joule heating.

[0043] Pass Ar gas into the Joule heating device, set the voltage at 20V on the Joule heating device, the heating time at 0.5s, the one - pulse time at 10s (heating time 0.5s, cooling time 0.5s and waiting time 9s), the number of pulses at 4 - 8 times. The obtained temperature is about 730 - 750℃ and the current is about 30A. The sample obtained after heating is the Pt / MoOx - F electrocatalyst.

[0044] The prepared Pt / MoOx-F powder sample was formulated into Ink. 5 μL of the Ink was taken and dropped onto a 3-mm glassy carbon electrode. The glassy carbon electrode with the catalyst served as the working electrode. A graphite rod was used as the counter electrode, and Ag / AgCl was used as the reference electrode to construct a three-electrode system for HER performance testing. The electrolyte was 0.5 M H 2 SO 4 solution.

[0045] The method for preparing the Ink was as follows: 2.5 mg of the catalyst, 0.5 mg of conductive carbon black, 0.5 mL of a mixed solvent (V 乙醇 :V 水 = 3:1), and 15 μL of 5 wt.% Nafion were added to a centrifuge tube. After mixing, the mixture was placed in an ultrasonic machine and sonicated for 20 min. The resulting product was the Ink of the catalyst.

[0046] The HER performance testing method for Examples 3 - 5 was the same as that for Example 2.

[0047] Example 3

[0048] In this example, the MoOx-F electrocatalyst was prepared as follows:

[0049] S1: 500 mg of MoO 3 was mixed with 500 mg of carbon black and ground using a pestle and mortar for 20 - 30 min to obtain a precursor powder.

[0050] S2: 30 - 50 mg of the precursor powder obtained in step S1 was placed between two pieces of carbon paper measuring 5 cm * 2 cm (length * width) and compacted. Subsequently, the carbon paper with the sample was placed in a quartz tube. The carbon paper was longer than the quartz tube, such that approximately 0.6 cm of carbon paper was exposed on both sides of the quartz tube. The edges of the carbon paper were placed on the Cu electrodes on both sides of the Joule heating device and clamped with Cu electrode pieces to complete the sample loading process. Subsequently, Joule heating was carried out.

[0051] S3: Ar gas was introduced into the Joule heating device. A voltage of 20 V was set on the Joule heating device, the heating time was 0.5 s, the one - pulse time was 10 s (heating time 0.5 s, cooling time 0.5 s, and waiting time 9 s), and the number of pulses was 4 - 8 times. The resulting temperature was approximately 730 - 750 °C, and the current was approximately 30 A. The sample obtained after heating was the MoOx-F electrocatalyst.

[0052] Example 4

[0053] In this example, the Pt / MoO 3 electrocatalyst was prepared as follows:

[0054] S1: 0.518 g of H 2 PtCl 6·6H 2 O particles were stirred and dissolved in 100 mL of deionized aqueous solution to form a 0.01 mol / L Pt precursor solution.

[0055] S2: To 500 mg of MoO 3 (0.00347 mol) powder was added the Pt precursor solution (17.35 mL) containing 1.735×10 -4 mol of Pt, and then the crucible containing the above sample was placed in an oven at 40 °C - 50 °C for drying.

[0056] S3: The dried powder obtained in step S2 was mixed with 500 mg of carbon black and ground with a pestle and mortar for 20 - 30 min to obtain the Pt precursor powder.

[0057] S4: 30 - 50 mg of the Pt precursor powder obtained in step S3 was taken and compacted between two pieces of carbon paper with dimensions 5 cm×2 cm (length×width). Then the carbon paper with the sample was placed in a quartz tube. The carbon paper was longer than the quartz tube, so that about 0.6 cm of carbon paper was exposed on both sides of the quartz tube. The edges of the carbon paper were placed on the Cu electrodes on both sides of the Joule heating device and clamped with Cu electrode pieces to complete the sample loading process, and then Joule heating was carried out.

[0058] S5: Ar gas was introduced into the Joule heating device. A voltage of 15 V was set on the Joule heating device, the heating time was 0.5 s, the one - pulse time was 10 s (heating time 0.5 s, cooling time 0.5 s and waiting time 9 s), the number of pulses was 4 - 8 times, the obtained temperature was less than 600 °C, the current was about 20 A, and the sample obtained after heating was the Pt / MoO 3 catalyst.

[0059] Example 5

[0060] In this example, the Pt / MoO 2 catalyst was prepared as follows:

[0061] S1: 0.518 g of H 2 PtCl 6 ·6H 2 O particles were accurately weighed and stirred and dissolved in 100 mL of deionized aqueous solution to form a 0.01 mol / L Pt precursor solution.

[0062] S2: To 500 mg of MoO 3 (0.00347 mol) powder was added the Pt precursor solution (17.35 mL) containing 1.735×10 -4 mol of Pt, and then the crucible containing the above sample was placed in an oven at 40 °C - 50 °C for drying.

[0063] S3: Mix the dried powder obtained in step S2 with 500 mg of carbon black, and grind them with a pestle and mortar for 20 - 30 min to obtain Pt precursor powder.

[0064] S4: Take 30 - 50 mg of the Pt precursor powder obtained in step S3 and place it between two pieces of carbon paper with dimensions 5 cm * 2 cm (length * width), then compact it. Subsequently, place the carbon paper with the sample in a quartz tube. The carbon paper is longer than the quartz tube, such that about 0.6 cm of carbon paper protrudes from both sides of the quartz tube. The edges of the carbon paper are placed on the Cu electrodes on both sides of the Joule heating device and clamped with Cu electrode pieces to complete the sample loading process, and then Joule heating is carried out.

[0065] S5: Pass Ar gas into the Joule heating device, set the voltage on the Joule heating device to 22 V, the heating time to 0.5 s, the one - pulse time to 10 s (heating time 0.5 s, cooling time 0.5 s, and waiting time 9 s), and the number of pulses to 4 - 8 times. The resulting temperature is about 825 - 860 °C and the current is about 34 A. The sample obtained after heating is the Pt / MoO 2 catalyst.

[0066] Figure 1 is the X - ray diffraction (XRD) pattern of Examples 2 and 3. This XRD shows that MoOx - F is mainly composed of MoO 2 and MoO 3 two crystal phases. Pt / MoOx - F is consistent with MoOx - F and is also composed of MoO 2 and MoO 3 two crystal phases, and no characteristic peaks of Pt are found in Pt / MoOx - F, probably because the content of Pt is too low (1.85 wt%).

[0067] Figure 2 are the XRD patterns of Pt / MoO 3 , Pt / MoOx - F, Pt / MoO 2 synthesized under different voltage conditions (Examples 4, 2, 5). It can be seen that the three respectively correspond to the crystal phases MoO 3 ; MoO 3 +MoO 2 ; MoO 2 .

[0068] Figure 3 is the high - resolution transmission electron microscope image of MoOx - F. It can be seen that two different lattice fringes appear on MoOx - F, corresponding to MoO 2 and MoO 3 respectively, indicating that MoOx - F is a heterostructure.

[0069] Figure 4HRTEM image of Pt / MoOx-F, on which three different lattice fringes appear, corresponding to Pt, MoO 2 and MoO 3 , which not only illustrates the heterostructure of Pt / MoOx-F but also proves the successful loading of Pt.

[0070] Figure 5 LSV graph of HER for the materials prepared in Examples 2 - 5. Among them, the material prepared in Example 2 exhibits the most excellent HER performance, achieving a current density of 10 mA / cm² with only 19.22 mV and 55.08 mV to reach 2 100 mA / cm². 2

[0071] Figure 6 Mass activity graph of the materials prepared in Examples 2, 4, and 5 at an overpotential (relative to the hydrogen scale) of 50 mV. Among them, the material prepared in Example 2 shows the highest mass activity, which is 6 and 3.67 times that of Pt / MoO 3 and Pt / MoO 2 respectively. This fully proves that under the same potential and the same mass loading of Pt, the material prepared in Example 2 has the highest intrinsic catalytic activity, greatly improving the utilization rate of Pt.

[0072] The above has described the embodiments of this example, but this example is not limited to the above specific implementation manners. The above specific implementation manners are merely illustrative and not restrictive. Under the inspiration of this example, those of ordinary skill in the art can also make many forms, all of which fall within the protection scope of this example.

Claims

1. A method for ultrafast preparation of noble metal-supported metal oxide electrocatalysts, characterized in that: The steps include: S1: Accurately weigh 0.518 g of H2PtCl6·6H2O pellets, stir and dissolve in 100 mL of deionized water to form a 0.01 mol / L Pt precursor solution; S2: Add 1.735*10 -4 17.35 mL of Pt precursor solution of 1 mol Pt was prepared, and then the crucible containing the sample was placed in an oven at 40°C-50°C to dry; S3: Mix the dried powder obtained in step S2: with 500 mg of carbon black, and grind them with a pestle and mortar for 20-30 minutes to obtain a Pt precursor powder; S4: Take 30-50 mg of the Pt precursor powder obtained in step S3 and place it between two pieces of 5 cm long * 2 cm wide carbon paper for compaction. Then place the carbon paper with the sample in a quartz tube. The carbon paper is longer than the quartz tube so that about 0.6 cm of carbon paper is exposed on both sides of the quartz tube. The edge of the carbon paper is placed on the Cu electrodes on both sides of the Joule heating device and clamped with Cu electrode sheets to complete the sample loading process, followed by Joule heating; Ar gas was introduced into the Joule heating device, and the voltage was set to 20 V, the heating time was 0.5 s, the pulse time was 10 s, the heating time was 0.5 s, the cooling time was 0.5 s, and the waiting time was 9 s. The number of pulses was 4-8 times, the obtained temperature was 730-750°C, the current was 30 A, and the sample obtained after heating was Pt / MoOx-F electrocatalyst.

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