A method for preparing a hydrogen evolution catalyst based on Fe2O3

Abstract

This invention discloses a method for preparing a hydrogen evolution catalyst based on Fe2O3. The method includes the following steps: LFPO and Glc·H2O are weighed at a mass ratio of 1:1-5, and ground in an agate mortar for 5-20 min to form a mixture. The mixture is then placed in a muffle furnace and calcined at 500-900℃ in air for 0.5-4 h to obtain a HER catalyst containing Li3Fe2(PO4)3, Fe2O3, and C. I-t curve testing shows that, at a test time of 10 hours, the HER catalytic performance of the prepared catalyst is significantly higher than that of commercial platinum-carbon catalysts, indicating that this metal-free catalyst has excellent hydrogen evolution performance. This invention features a simple preparation process, low cost, and suitability for large-scale commercial production.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, and more specifically, to a method for preparing a hydrogen evolution catalyst based on Fe2O3. Background Technology

[0002] With the continued expansion of the global economy and the ongoing process of industrialization, the global consumption of traditional primary fossil fuels such as oil, coal, and natural gas has reached historical peaks in both scale and rate. Their unrestrained development and excessive consumption have triggered global ecological and environmental crises such as air pollution, thermal pollution, and global warming, and have also led to severe energy security problems such as a sharp decline in non-renewable energy reserves and regional energy supply-demand imbalances. Against this backdrop, the development and efficient utilization of renewable and clean energy has become a core research frontier for solving the global energy dilemma and curbing ecological degradation.

[0003] Compared to traditional fossil fuels, hydrogen has a lower concentration of 142 MJ / kg. -1 With its ultra-high energy density and zero carbon emissions from combustion, it is widely regarded as a highly efficient and clean energy carrier with great potential for future sustainable energy systems. Water electrolysis for hydrogen production, with its inherent advantages of zero by-product pollution throughout the entire process and the ability to be coupled with renewable energy sources such as wind and solar power to achieve closed-loop energy utilization, is recognized as the most promising green hydrogen production technology route currently available.

[0004] Numerous studies have confirmed that the electrocatalytic kinetics of the hydrogen evolution reaction (HER) at the cathode of water electrolysis is the core factor directly determining the energy conversion efficiency and overall production cost of the water electrolysis hydrogen production system. This means that high-performance HER electrocatalysts are crucial for reducing costs and increasing efficiency in water electrolysis hydrogen production processes, promoting their large-scale industrial application, and playing an irreplaceable role. Literature review shows that in alkaline systems, transition metals possess the core advantages of high catalytic activity, low cost, and excellent stability, making them ideal and efficient catalyst candidates to replace precious metals in water electrolysis reactions. Compared to other transition metals, iron (Fe) is widely recognized due to its tunable electronic structure, while also offering higher cost-effectiveness, readily available raw materials, and abundant crustal reserves, making it considered a potential high-efficiency HER catalyst material.

[0005] For example, Yu Zhiyong et al. (CN114000175A) disclosed a nickel-iron alloy hydrogen evolution electrode and its preparation method. This invention, through electrodeposition-alkali washing-redeposition, produces a nickel-iron alloy hydrogen evolution electrode with advantages such as high reaction surface area, strong catalytic activity, and long service life. Carbon-based materials possess excellent conductivity, large specific surface area, tunable porous structure, outstanding chemical and electrochemical stability, and tunable electronic structure. They can accelerate charge transfer and mass transport, effectively anchor active components, and inhibit nanoparticle aggregation and corrosion. Simultaneously, strategies such as heteroatom doping and defect engineering can be used to precisely optimize hydrogen adsorption energy. Therefore, carbon-based materials have wide applications in the field of hydrogen evolution catalysis, serving as ideal supports for loading noble and non-noble metal active substances, or directly constructing metal-free catalysts after modification.

[0006] Xiao Junwu et al. (CN120054523A) disclosed a NiRuM / C catalyst for anion exchange membrane water electrolysis, its preparation method, and its application. In their patent, the carbon material is one or more of carbon black, carbon nanotubes, carbon spheres, and graphene. Jiang Baojiang et al. (CN119121284A) disclosed a preparation method and application of a 3D porous honeycomb NiFeP / C hydrogen evolution catalyst. In their patent, the carbon material is carbonaceous material or carbon cloth. Xu Yao et al. (CN116575073A) disclosed a transition metal-Mo-C hydrogen production catalyst, hydrogen evolution electrode, preparation, and application. Ma Fei et al. (CN110327949A) disclosed a carbon-supported rhodium / rhodium phosphide nanocomposite material, its preparation method, and its application. Nie Ming et al. (CN107262114A) disclosed a preparation method of a PtAuFe / C composite hydrogen evolution catalyst based on sulfuric acid electrolyte. In their patent, the carbon material is carbon powder. In-depth research and analysis of the aforementioned HER catalysts revealed that they generally suffer from drawbacks such as complex preparation processes, high production costs, and difficulties in industrial-scale preparation. Therefore, the development of novel and highly efficient HER catalysts remains a research hotspot and key focus in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a hydrogen evolution catalyst based on Fe2O3.

[0008] The objective of this invention is achieved by preparing a hydrogen evolution catalyst containing Li3Fe2(PO4)3, Fe2O3 and C under suitable conditions through direct calcination of a mixture of lithium iron phosphate and dextrose. In other words, the obtained hydrogen evolution catalyst contains Li3Fe2(PO4)3, Fe2O3 and C.

[0009] Specifically, the preparation method of the present invention includes the following steps: Step 1: Material Preparation Lithium iron phosphate (LFPOO); dextrose (Glc·H2O); 1 mol L -1 KOH solution; 0.1% Nafion solution; glassy carbon electrode; graphite rod; Hg / HgO reference electrode.

[0010] Step 2: Catalyst Preparation Weigh LFPOO and Glc·H2O at a mass ratio of 1:(1~5), grind them in an agate mortar for 5~20 min to form a mixture, and then place the mixture in a muffle furnace and calcine it at 500℃~900℃ in air for 0.5~4 h to obtain the prepared catalyst (Fe / C).

[0011] As preferred conditions, the optimal mass ratio of LFPO and Glc·H2O is 1:1, and the optimal grinding time is 20 min.

[0012] As preferred conditions, the calcination temperature of the mixture after grinding LFPO and Glc·H2O in a muffle furnace is 600℃ and the calcination time is 3 h.

[0013] Step 3: Catalyst Performance Testing (1) Electrode preparation Accurately weigh 2 mg of the catalyst sample Fe / C using an electronic balance and place it in a 1.5 mL centrifuge tube. Add 0.5 mL of Nafion solution and sonicate in a KQ-50DE CNC ultrasonic cleaner for 30 min to obtain a suspension. After sonication, remove the centrifuge tube and shake it evenly. Then, use a pipette to transfer 10 μL of the suspension onto the glassy carbon electrode (working electrode) in two separate additions to obtain the catalyst-modified glassy carbon electrode.

[0014] (2) HER performance test A catalyst-modified glassy carbon electrode was used as the working electrode, a graphite electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode. A CHI660B electrochemical workstation was used at a concentration of 1 mol / L. -1 Electrocatalytic hydrogen evolution performance was tested in an alkaline KOH electrolyte within a voltage range of -0.6 V to -2.0 V. The scan rate for linear sweep voltammetry (LSV) was set to 5 mV / s. -1 The LSV hydrogen evolution polarization curve of the sample was obtained in this way, and the original voltage obtained by the test was the potential relative to the Hg / HgO reference electrode. The current-time (it) stability test adopted the constant potential mode, and the dynamic change of current over time was recorded under a fixed voltage condition. The test was carried out for 100 h to obtain the long-period chronocurrent curve, which was used to evaluate the long-term electrolytic stability of the catalyst.

[0015] The beneficial effects of this invention are as follows: This invention uses a mixture of LFPO and Glc·H2O as raw materials, and obtains a HER hydrogen evolution catalyst containing Li3Fe2(PO4)3, Fe2O3, and C through a simple air calcination method. It features a simple preparation process, low cost, good hydrogen evolution catalytic effect, and suitability for large-scale industrial production. Attached Figure Description

[0016] Figure 1 The XRD pattern of the catalyst in Example 1 of the present invention; Figure 2 These are SEM microstructure images of the catalyst at different scales in Example 1 of the present invention. Figure 2 The scale bar for A in the middle is 1 μm. Figure 2 The scale bar for B in the middle is 100 nm; Figure 3 The EDS elemental analysis spectrum of the catalyst in Example 1 of the present invention; Figure 4 The linear sweep voltammetry (LSV) curve of the catalyst in Example 1 of the present invention; Figure 5 This is a comparison of the 100-h chronocurrent (it) curves of the catalyst and the commercial Pt / C catalyst in Example 1 of the present invention. Detailed Implementation

[0017] The following examples are used to illustrate the present invention.

[0018] Example 1 0.3 g of LFPO and 0.3 g of Glc·H2O were weighed out at a mass ratio of 1:1 and placed in an agate mortar. The mixture was ground for 20 min to form a mixture, which was then placed in a muffle furnace and calcined at 600 °C for 3 h in air to obtain the prepared catalyst (Fe / C). The prepared catalyst was characterized by XRD, SEM, and EDS. The XRD results of the catalyst are shown below. Figure 1 As shown, the microscopic SEM morphology is as follows Figure 2 As shown; detailed EDS energy dispersive spectroscopy (EDS) results can be found in [link to EDS data]. Figure 3 .

[0019] The electrocatalytic hydrogen evolution performance of the prepared Fe / C composite catalyst was tested using the above method. 2 mg of catalyst sample was accurately weighed using an electronic balance and placed in a 1.5 mL centrifuge tube. 0.5 mL of Nafion solution was added, and the mixture was ultrasonically dispersed for 30 min to obtain a uniform catalyst dispersion. A total of 10 μL of the dispersion was pipetted into portions and uniformly drop-coated onto the surface of a glassy carbon electrode. After natural drying, the catalyst-modified working electrode was obtained. Using the modified glassy carbon electrode as the working electrode, a graphite electrode as the counter electrode, and an Hg / HgO electrode as the reference electrode, 1 mol L... -1 A standard three-electrode testing system was constructed using KOH solution as the electrolyte. Using a CHI660B electrochemical workstation, measurements were performed at 5 mV s⁻¹ within the potential range of -0.6 V to -2.0 V (vs. Hg / HgO). -1 Linear scan voltammetry was performed at the scan rate, and LSV polarization curves were acquired to evaluate the hydrogen evolution catalytic activity of the catalyst. The test results are as follows: Figure 4 As shown in the figure. A constant potential of -1.45 V (vs. Hg / HgO) was further set, and the current density was continuously tested for 100 h using the chronoamperometry method to monitor the change in current density over time, thereby investigating the long-term electrolytic stability of the catalyst. The obtained it curve is shown in the figure. Figure 5 As shown.

[0020] Figure 1 The XRD pattern of the prepared Fe / C catalyst is shown. In the XRD pattern, the diffraction peaks at 16.47°, 20.84°, 24.53°, 27.67°, 29.51° and 36.55° match the (111), (002), (031), (221), (202) and (123) crystal planes of Li3Fe2(PO4)3 (JCPDS, NO. 47-107), which indicates that the lithium iron phosphate was partially converted into Li3Fe2(PO4)3 after calcination. The diffraction peaks at 23.29°, 33.30°, 35.75°, 40.73°, 54.24°, and 57.08° match the (012), (104), (110), (113), (116), and (018) crystal planes of Fe2O3 (JCPDS, NO. 13-534), indicating that calcined lithium iron phosphate is partially converted into Fe2O3. Furthermore, the diffraction peak at 44.16° matches the (111) crystal plane of C (JCPDS, NO. 75-410). Figure 1 The catalyst's main components are Li3Fe2(PO4)3, Fe2O3, and C. Literature review shows that there are no reports, either domestically or internationally, on hydrogen evolution reaction (HER) catalysts with these two main components.

[0021] Figure 2The SEM microstructure of the prepared Fe / C catalyst at different scales of 1 μm and 100 nm is shown. Low-magnification images reveal that the sample is generally irregularly shaped with uneven particle size distribution and obvious agglomeration. High-magnification images further demonstrate that the large particle surface is loaded with a large number of fine particles with a size of approximately tens of nanometers, exhibiting typical hierarchical structural characteristics. This rough surface assembled from nanoparticles provides abundant active sites for the electrocatalytic hydrogen evolution reaction and facilitates electrolyte penetration and charge transport, providing a structural basis for its excellent catalytic performance.

[0022] To further confirm the elemental composition of the catalyst, the Fe / C ratio of the prepared catalyst was characterized by EDS energy dispersive spectroscopy. The results are as follows: Figure 3 As shown in the figure, characteristic peaks of four elements, C, O, P, and Fe, appeared in the energy dispersive spectroscopy (EDS) spectrum, corresponding to the elemental composition of the carbon component, phosphate phase, and iron oxide phase in the catalyst. No other impurity element signals were detected, indicating that the prepared catalyst has high purity. The EDS analysis results are consistent with the XRD phase characterization results, confirming the successful synthesis of the target catalyst. The EDS test results show that the catalyst is mainly composed of four elements: Fe, O, P, and C, with Fe having the highest mass percentage (44.01 wt%) and O having the highest atomic percentage (58.63%). It also contains a certain proportion of P (20.58 wt%) and a small amount of C (0.85 wt%). The elemental composition is completely consistent with the theoretical phase (Li3Fe2(PO4)3, Fe2O3, and C), and no other impurity elements were detected, proving that the prepared catalyst has high purity and the target phase was successfully formed.

[0023] Figure 4 The figure shows the linear sweep voltammetry (LSV) curve of the prepared Fe / C catalyst. As can be seen from the figure, at 10 mA cm⁻¹... -2 Under (taking the absolute value of the negative value), the voltage corresponding to catalyst Fe / C is -1.45 V (vs. Hg / HgO).

[0024] Figure 5 The chronocurrent (it) stability curves of Fe / C catalyst and commercial Pt / C catalyst during a 100-h potentiostatic electrolysis process were compared. The tests were conducted continuously at a constant operating potential of -1.45 V (vs. Hg / HgO). The results showed that commercial Pt / C exhibited high initial catalytic activity, with an initial current density reaching 185.14 mA cm⁻¹. -2 However, during long-term electrolysis, a continuous current decay occurred, and after 100 hours, the current density remained at only 49.30 mA cm⁻¹. -2 In contrast, the Fe / C catalyst, despite its low initial activity (initial current density 19.35 mA cm⁻¹), showed promising results.-2 However, Fe / C undergoes continuous in-situ activation during electrolysis, and its catalytic performance steadily improves with increasing reaction time. After approximately 10 hours of electrolysis, its current density surpasses that of commercially available Pt / C. In a 100-hour stability test, Fe / C showed no significant current decay, and its current density consistently increased, reaching 89.30 mA cm⁻¹ at 100 hours. -2 This fully demonstrates that the catalyst has a long-term operational stability and excellent in-situ activation capability that far exceed those of commercial Pt / C.

[0025] Example 2 Weigh 0.3 g of LFPO and 0.3 g of Glc·H2O at a mass ratio of 1:1, place them in an agate mortar, grind for 20 min to form a mixture, and then place the mixture in a muffle furnace and calcine at 500 °C for 4 h in an air atmosphere to obtain the prepared catalyst.

[0026] The LSV hydrogen evolution curve was tested on a CHI660B electrochemical workstation according to the method in Example 1. The results showed that at 10 mA cm⁻¹... -2 At (absolute negative value), the voltage corresponding to the Fe / C catalyst is -1.47 V (vs. Hg / HgO). A 100-hour chronoamperometry test was conducted at a constant potential of -1.47 V (vs. Hg / HgO), and the results showed that the initial current density of Fe / C was 17.82 mA cm⁻¹. -2 The catalytic performance continuously improved as the reaction progressed, surpassing commercial Pt / C at approximately 11.5 h; no significant current decay was observed throughout the 100 h test, and the current density steadily increased to 85.43 mA cm⁻¹. -2 It exhibits excellent long-term electrocatalytic stability and in-situ activation characteristics.

[0027] Example 3 Weigh 0.3 g of LFPO and 0.3 g of Glc·H2O at a mass ratio of 1:1, place them in an agate mortar, grind for 20 min to form a mixture, and then place the mixture in a muffle furnace and calcine at 600 °C for 4 h in air atmosphere to obtain the prepared catalyst.

[0028] The LSV hydrogen evolution curve was tested on a CHI660B electrochemical workstation according to the method in Example 1. The results showed that at 10 mA cm⁻¹... -2At (absolute negative value), the voltage corresponding to the Fe / C catalyst is -1.44 V (vs. Hg / HgO). A 100-hour chronoamperometry test was conducted at a constant potential of -1.44 V (vs. Hg / HgO), and the results showed that the initial current density of Fe / C was 20.16 mA cm⁻¹. -2 The catalytic performance continuously improved as the reaction progressed, surpassing commercial Pt / C at approximately 9.5 h; no significant current decay was observed throughout the 100 h test, and the current density steadily increased to 91.47 mA cm⁻¹. -2 It exhibits excellent long-term electrocatalytic stability and in-situ activation characteristics.

[0029] Example 4 Weigh 0.3 g of LFPO and 0.3 g of Glc·H2O at a mass ratio of 1:1, place them in an agate mortar, grind for 20 min to form a mixture, and then place the mixture in a muffle furnace and calcine at 700 °C for 2.5 h in air atmosphere to obtain the prepared catalyst.

[0030] The LSV hydrogen evolution curve was tested on a CHI660B electrochemical workstation according to the method in Example 1. The results showed that at 10 mA cm⁻¹... -2 At (absolute negative value), the voltage corresponding to the Fe / C catalyst is -1.43 V (vs. Hg / HgO). A 100-hour chronoamperometry test was conducted at a constant potential of -1.43 V (vs. Hg / HgO), and the results showed that the initial current density of Fe / C was 21.47 mA cm⁻¹. -2 The catalytic performance continuously improved as the reaction progressed, surpassing commercial Pt / C at approximately 9 hours; no significant current decay was observed throughout the 100-hour test, and the current density steadily increased to 95.62 mA cm⁻¹. -2 It exhibits excellent long-term electrocatalytic stability and in-situ activation characteristics.

[0031] Example 5 Weigh 0.3 g of LFPO and 0.3 g of Glc·H2O at a mass ratio of 1:1, place them in an agate mortar, grind for 20 min to form a mixture, and then place the mixture in a muffle furnace and calcine at 800 °C for 2 h in air atmosphere to obtain the prepared catalyst.

[0032] The LSV hydrogen evolution curve was tested on a CHI660B electrochemical workstation according to the method in Example 1. At 10 mAcm... -2At (absolute negative value), the voltage corresponding to the Fe / C catalyst is -1.46 V (vs. Hg / HgO). A 100-hour chronoamperometry test was conducted at a constant potential of -1.46 V (vs. Hg / HgO), and the results showed that the initial current density of Fe / C was 15.79 mAcm⁻¹. -2 The catalytic performance continuously improved as the reaction progressed, surpassing commercial Pt / C at approximately 11 h; no significant current decay was observed throughout the 100 h test, and the current density steadily increased to 83.67 mA cm⁻¹. -2 It exhibits excellent long-term electrocatalytic stability and in-situ activation characteristics.

[0033] Example 6 Weigh 0.3 g of LFPO and 0.3 g of Glc·H2O at a mass ratio of 1:1, place them in an agate mortar, grind for 20 min to form a mixture, and then place the mixture in a muffle furnace and calcine at 900 °C for 1 h in air atmosphere to obtain the prepared catalyst.

[0034] The LSV hydrogen evolution curve was tested on a CHI660B electrochemical workstation according to the method in Example 1. The results showed that at 10 mA cm⁻¹... -2 At (absolute negative value), the voltage corresponding to the Fe / C catalyst is -1.42 V (vs. Hg / HgO). A 100-hour chronoamperometry test was conducted at a constant potential of -1.42 V (vs. Hg / HgO), and the results showed that the initial current density of Fe / C was 22.63 mA cm⁻¹. -2 The catalytic performance continuously improved as the reaction progressed, surpassing commercial Pt / C at approximately 8.5 h; no significant current decay was observed throughout the 100 h test, and the current density steadily increased to 97.47 mA cm⁻¹. -2 It exhibits excellent long-term electrocatalytic stability and in-situ activation characteristics.

Claims

1. A method for preparing a hydrogen evolution catalyst based on Fe2O3, characterized in that, Includes the following steps: Step 1: Prepare the following materials: Lithium iron phosphate (LFPO); dextrose (Glc·H₂O); 1 mol L -1 KOH solution; 0.1% Nafion solution; glassy carbon electrode; graphite rod; Hg / HgO reference electrode; Step 2: Catalyst preparation: LFPO and Glc·H2O were weighed at a mass ratio of 1:1~5, and ground in an agate mortar for 5~20 min to form a mixture. The mixture was then placed in a muffle furnace and calcined in air at 500℃~900℃ for 0.5~4 h to obtain the prepared catalyst.

2. The method for preparing the Fe2O3-based hydrogen evolution catalyst according to claim 1, characterized in that: The mass ratio of LFPO to Glc·H2O was 1:1, and the grinding time was 20 min.

3. The method for preparing the Fe2O3-based hydrogen evolution catalyst according to claim 1, characterized in that: The mixture of LFPO and Glc·H2O after grinding was calcined in a muffle furnace at a temperature of 600 °C for 3 h.

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