Hydrogen evolution catalytic material with gamma-prime phase nano-array structure and preparation method thereof

Abstract

The application discloses a hydrogen evolution catalytic material with a gamma prime phase nano array structure, and the hydrogen evolution catalytic material comprises a cobalt-based alloy base and a nano catalytic layer; the cobalt-based alloy base is a Co-xAl-yW alloy; wherein x and y are atomic percentages, the value range of x is 8-10, and the value range of y is 9-10; the nano catalytic layer is in-situ grown on the surface of the cobalt-based alloy base, the nano catalytic layer has a gamma prime phase nano array structure, and the gamma prime phase nano array structure is composed of gamma prime phase nano units in a rectangular array distribution. The hydrogen evolution catalytic material has high-density active sites and optimized hydrogen evolution reaction kinetics characteristics, has excellent catalytic activity, and realizes the double improvement of acid resistance and long-term stability by relying on the oxidation layer protection and the regular array structure, and fundamentally solves the technical pain point that the activity and stability of traditional non-noble metal catalysts are difficult to be considered.

Description

Technical Field

[0001] This invention relates to the field of hydrogen evolution catalytic materials technology, and more specifically to a hydrogen evolution catalytic material having a γ' phase nanoarray structure and its preparation method. Background Technology

[0002] Hydrogen evolution catalysts are widely used in energy, chemical and other fields, and are key to the industrialization of hydrogen energy development and electrochemical hydrogen production technologies. Therefore, developing efficient, stable and low-cost hydrogen evolution catalysts is of great significance and industrial value for breaking through the bottleneck of hydrogen energy utilization and reducing the cost of hydrogen production.

[0003] While noble metal hydrogen evolution catalysts, represented by Pt, are highly active, their scarcity, high cost, and susceptibility to poisoning severely restrict their large-scale industrial application. Therefore, developing high-performance non-noble metal hydrogen evolution catalysts to replace noble metals has become a research hotspot and core direction in the field of hydrogen evolution catalysis.

[0004] Co-based electrocatalysts, due to their tunable electronic structure and excellent corrosion resistance, have become ideal alternatives to noble metal catalysts in acidic electrolytes, showing broad application potential. Based on Brewer's intermetallic bonding model, alloys formed between non-noble metals and Co can enhance hydrogen evolution reaction (HEER) catalytic activity by regulating electronic configuration and increasing bond energy through intermetallic synergistic effects. Transition element W readily interacts with Co, transferring paired d electrons to unfilled d orbitals to generate a synergistic electronic effect, optimizing the HEER reaction pathway. Therefore, Co / W-based alloys, with their excellent catalytic activity and electrochemical stability, have become an important research direction for non-noble metal HEER electrocatalysts, and have been prepared and applied to HEER reactions via electrodeposition, hydrothermal methods, and other techniques.

[0005] However, existing Co-W-based alloy hydrogen evolution catalysts still face numerous technical bottlenecks, hindering their catalytic performance improvement and industrial application. Firstly, the exposed active sites are few and their density is low, preventing the full realization of the Co-W synergistic effect and hindering the effective optimization of hydrogen adsorption free energy. This results in a high hydrogen evolution overpotential, a large Tafel slope, and limited reaction kinetics, leading to activity far inferior to Pt-based catalysts. Secondly, the microstructure has poor controllability, the matrix has poor acid resistance, and it is easily corroded by acidic electrolytes, causing the loss of active sites and failing to meet the long-term stability requirements for industrial hydrogen production.

[0006] In addition, the preparation process has limitations: traditional processes such as electrodeposition and hydrothermal methods have poor controllability and high complexity, making it difficult to accurately control the micro-phase structure, resulting in poor material performance uniformity and large batch-to-batch differences; at the same time, existing materials generally suffer from the problem of "difficulty in achieving both high activity and high stability", and cannot achieve synergistic optimization of the two, and there is still a large gap between them and Pt-based noble metal catalysts.

[0007] In summary, given the problems of insufficient catalytic activity, poor structural stability, weak structural controllability, difficulty in balancing activity and stability, and limitations in preparation processes of existing Co-W-based hydrogen evolution catalysts, the development of hydrogen evolution catalysts that combine high activity, high stability, and low cost has become an urgent technical need to be addressed in this field. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a hydrogen evolution catalyst with a γ' phase nanoarray structure and its preparation method. This material uses non-precious metals as raw materials, resulting in low cost. Through innovative processes, the structure is precisely controllable, exhibiting both high-density active sites and optimized hydrogen evolution reaction kinetics. It demonstrates excellent catalytic activity and achieves dual enhancements in acid resistance and long-term stability through oxide layer protection and a well-organized array structure. This fundamentally solves the technical pain point of traditional non-precious metal catalysts, which struggle to balance activity and stability.

[0009] According to a first aspect of the present invention, a hydrogen evolution catalytic material having a γ' phase nanoarray structure is provided, the hydrogen evolution catalytic material comprising:

[0010] A cobalt-based alloy matrix, wherein the cobalt-based alloy matrix is ​​a Co-xAl-yW alloy; wherein x and y are atomic percentages, with x ranging from 8 to 10 and y ranging from 9 to 10; and

[0011] A nanocatalytic layer is grown in situ on the surface of the cobalt-based alloy substrate. The nanocatalytic layer has a γ' phase nanoarray structure, which is composed of γ' phase nanounits distributed in a rectangular array.

[0012] As an optional implementation, the γ' phase is an intermetallic compound with an L12-type long-range ordered structure, and the intermetallic compound is Co3W; the γ' phase nanounits have a regular rectangular block morphology on the surface of the cobalt-based alloy matrix, and there are nanoscale gaps between each nanounit.

[0013] As an optional implementation, the surface of the γ' phase nanounit is coated with an in-situ generated composite oxide layer, the composition of which includes oxides of cobalt, oxides of tungsten, and oxides of aluminum.

[0014] As an optional implementation, based on the peak fitting calculation of X-ray diffraction pattern, the peak area of ​​the γ' phase diffraction peak accounts for 60% to 70% of the total area of ​​all diffraction peaks.

[0015] As an optional implementation, the nanounit has the following dimensions: length 75 nm to 120 nm, width 45 nm to 85 nm.

[0016] As an optional implementation, the value of x ranges from 9 to 9.2, and the value of y ranges from 9 to 9.2.

[0017] As an optional implementation, the γ' phase nanoarray structure is formed by solution aging of the cobalt-based alloy matrix, utilizing phase separation of the γ phase and γ' phase, and selective etching.

[0018] According to a second aspect of the present invention, a method for preparing the aforementioned hydrogen evolution catalytic material having a γ' phase nanoarray structure is provided, comprising the following steps:

[0019] Cobalt, aluminum and tungsten raw materials are weighed according to atomic percentage and smelted to prepare Co-xAl-yW alloy ingots, wherein the value of x ranges from 8 to 10 and the value of y ranges from 9 to 10.

[0020] The Co-xAl-yW alloy ingot was subjected to solution treatment and aging to obtain a cobalt-based alloy precursor with a two-phase structure of γ and γ'.

[0021] The cobalt-based alloy precursor is placed in an acidic electrolyte for chemical dealloying treatment to selectively remove part of the γ phase, thereby forming a γ' phase nanoarray structure on the surface of the cobalt-based alloy matrix to obtain the hydrogen evolution catalyst material.

[0022] As an optional implementation, the temperature T1 of the solution treatment is in the range of 1200℃ < T1 < 1360℃, and the temperature T2 of the aging treatment is in the range of 870℃ < T2 < 950℃.

[0023] As an optional implementation, the acidic electrolyte is aqua regia or 0.48 M~0.53 M H2SO4; the chemical dealloying time is: 70 h~75 h for H2SO4 treatment, or 5 min~10 min for aqua regia treatment.

[0024] As can be seen from the above technical solutions of the present invention, the hydrogen evolution catalyst material with γ' phase nanoarray structure proposed in this invention has the following advantages:

[0025] (1) Significantly improve hydrogen evolution catalytic activity: This invention forms a large number of lattice defects at the interface through chemical dealloying process, exposing high-density catalytic active sites. At the same time, it utilizes the synergistic electron transfer effect of Co and W bimetals to optimize the hydrogen adsorption free energy and reduce the charge transfer energy barrier of hydrogen evolution reaction, so that the material has an ultra-low Tafel slope. The kinetic efficiency of hydrogen evolution reaction is significantly improved and conforms to the Volmer-Tafel mechanism, effectively solving the technical problems of insufficient activity and limited reaction kinetics of existing Co-W based catalytic materials.

[0026] (2) Achieving synergistic optimization of catalytic activity and stability: W element promotes the formation of an oxide layer on the material surface, which can effectively inhibit H in acidic electrolyte. + Excessive corrosion of Co active sites is prevented, while the well-organized L12-γ'-Co3W rectangular nanoarray structure avoids structural collapse and active phase aggregation under long-term electrochemical cycling or high current density. The material's acid resistance and long-term structural stability are protected by both the protective layer and the structure itself, fundamentally solving the industry pain point that traditional non-precious metal catalysts cannot achieve both activity and stability.

[0027] (3) Achieving precise control over the microstructure of materials: This invention relies on the genetic characteristics of microstructure to make the geometric features of the nanoarray structure highly matched with the precipitated phase after heat treatment, with only a slight reduction in size. The size and morphology of the array can be precisely controlled, which greatly improves the uniformity of the material's performance and effectively improves the problems of poor controllability of the material structure and large batch differences in the existing process.

[0028] (4) It has significant cost advantages: The present invention uses non-precious metals such as Co and W as core raw materials, without the need to use scarce precious metals such as Pt. It avoids the resource restrictions and high cost of precious metals from the source. Moreover, the raw materials are readily available, which greatly reduces the preparation cost of catalytic materials and is suitable for large-scale industrial production.

[0029] (5) The preparation process is easy to industrialize and promote: The present invention adopts a combination process of solution heat treatment-aging heat treatment-chemical dealloying. The process steps are simple and highly controllable. It can be produced based on the existing heat treatment technology of Co-based alloys. No complex special equipment is required. The process has good compatibility and is easy to realize industrialization and promotion.

[0030] (6) It has extremely high industrial application value: The comprehensive performance of the material of this invention is significantly improved compared with the existing Co-W-based catalytic materials. It is an ideal substitute for Pt-based and other noble metal hydrogen evolution catalytic materials in acidic electrolytes. It can promote the industrialization process of energy and chemical technologies such as hydrogen energy development and electrochemical hydrogen production, and has broad application prospects. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the γ' phase nanounit structure of the hydrogen evolution catalytic material exemplified by the present invention and a schematic diagram of its hydrogen evolution reaction process.

[0032] Figure 2 This is a SEM morphology image of the sample from Example 1 of the present invention; wherein, Figure 2 Part a in the image is a low-magnification image; Figure 2 Part b in the image is a high-magnification image.

[0033] Figure 3 These are SEM-EDS test images of the sample from Example 1 of this invention; wherein, Figure 3 Part 'a' in the text refers to SEM. Figure 3 The b part in the equation is the EDS corresponding to a.

[0034] Figure 4 These are SEM images of the sample from Example 2 of this invention; wherein, Figure 4 Part a in the image is a low-magnification image; Figure 4 Part b in the image is a high-magnification image.

[0035] Figure 5 These are SEM-EDS test images of the sample from Example 2 of this invention; wherein, Figure 5 Part 'a' in the text refers to SEM. Figure 5 The b part in the equation is the EDS corresponding to a.

[0036] Figure 6 These are SEM images of the sample from Example 3 of this invention; wherein, Figure 6 Part a in the image is a low-magnification image; Figure 6 Part b in the image is a high-magnification image.

[0037] Figure 7 These are SEM-EDS test images of the sample from Example 3 of this invention; wherein, Figure 7 Part 'a' in the text refers to SEM. Figure 7 The b part in the equation is the EDS corresponding to a.

[0038] Figure 8 These are XRD test images of samples from embodiments of the present invention; wherein, Figure 8 Part a in the text refers to the sample from Example 2. Figure 8 Part b in the text refers to the sample from Example 3.

[0039] Figure 9 This is a graph showing the hydrogen evolution reaction performance of the samples in the embodiments of the present invention; wherein, Figure 9 Part 'a' in the graph is the capacitance fitting plot. Figure 9 Part b in the diagram is the impedance (EIS) plot. Figure 9 Part c in the figure is the linear sweep voltammetry (LSV) plot. Figure 9 The d-part in the figure represents the Tafel slope plot.

[0040] Figure 10 This is a SEM image of the sample from Example 2 of the present invention after 5000 LSV cycles; wherein, Figure 10 Part a in the image is a low-magnification image; Figure 10 Part b in the image is a high-magnification image.

[0041] Figure 11 This is a durability test chart of the sample from Example 2 of the present invention after 5000 LSV cycles; wherein, Figure 11Part a in the figure is a linear sweep voltammetry (LSV) curve plot with 1-5000 cycles. Figure 11 Part b in the diagram is a Tafel slope plot. Detailed Implementation

[0042] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0043] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described below in more detail, can be implemented in any of a number of ways.

[0044] Combination Figure 1 As shown, in one embodiment of the present invention, a hydrogen evolution catalytic material having a γ' phase nanoarray structure is provided, the hydrogen evolution catalytic material comprising a cobalt-based alloy matrix and a nanocatalytic layer.

[0045] The cobalt-based alloy matrix is ​​a Co-xAl-yW alloy, where x and y are atomic percentages, with x ranging from 8 to 10 and y ranging from 9 to 10.

[0046] The nanocatalytic layer is grown in situ on the surface of a cobalt-based alloy substrate. The nanocatalytic layer possesses a γ'-phase nanoarray structure, which is composed of γ'-phase nanounits distributed in a rectangular array. These nanounits are as follows: Figure 1 As shown.

[0047] In some embodiments, the γ' phase nanoarray structure is an L12-γ'-Co3W nanoarray structure, that is, the γ' phase is an intermetallic compound with an L12-type long-range ordered structure, and the intermetallic compound is Co3W; and

[0048] The γ' phase nanounits exhibit a regular rectangular block morphology on the surface of the cobalt-based alloy matrix, and there are nanoscale gaps between each nanounit.

[0049] In some embodiments, the surface of the γ' phase nanounit is coated with an in-situ generated composite oxide layer, the composition of which includes oxides of cobalt, oxides of tungsten, and oxides of aluminum.

[0050] In some embodiments, the oxides of cobalt include CoO and / or Co3O4, the oxides of tungsten include WO3, and the oxides of aluminum include Al2O3.

[0051] In some embodiments, based on the peak fitting calculation of X-ray diffraction patterns, the peak area of ​​the γ' phase diffraction peak accounts for 60% to 70% of the total area of ​​all diffraction peaks.

[0052] In some embodiments, the dimensions of the nanounits are: length 75 nm to 120 nm and width 45 nm to 85 nm.

[0053] In some embodiments, the value of x ranges from 9 to 9.2, and the value of y ranges from 9 to 9.2.

[0054] In some embodiments, the γ' phase nanoarray structure is formed by solution aging of a cobalt-based alloy matrix, utilizing phase separation of the γ phase and γ' phase, and selective etching.

[0055] In another embodiment of the present invention, a method for preparing the aforementioned hydrogen evolution catalytic material having a γ' phase nanoarray structure is provided, comprising the following steps:

[0056] Cobalt, aluminum and tungsten raw materials are weighed according to atomic percentage and smelted to prepare Co-xAl-yW alloy ingots, wherein the value of x ranges from 8 to 10 and the value of y ranges from 9 to 10.

[0057] Co-xAl-yW alloy ingots are subjected to solution and aging treatment. Through solution heat treatment, the γ' phase, which was originally in the precipitated state in the alloy, is fully dissolved into the γ-Co matrix to form a supersaturated solid solution with uniform composition. Subsequently, through aging heat treatment, an ordered L12-γ'-Co3(Al,W) phase is precipitated to form a precursor structure in which γ and γ' coexist.

[0058] The cobalt-based alloy precursor was chemically dealloyed in an acidic electrolyte. The intrinsic difference in electrochemical activity between the γ and γ' phases produced a significant microcouple effect, which drove selective phase dissolution during the dealloying process. The γ-Co matrix phase dissolved preferentially, and the corrosion-resistant L12-γ'-Co3(Al,W) phase formed an L12-γ'-Co3W nanoarray structure, thereby forming a γ' phase nanoarray structure on the surface of the cobalt-based alloy matrix, resulting in a hydrogen evolution catalyst material.

[0059] In some embodiments, the solution treatment temperature T1 ranges from 1200℃ < T1 < 1360℃, and is particularly preferred to be 1280℃ < T1 < 1325℃; the aging treatment temperature T2 ranges from 870℃ < T2 < 950℃; the alloy is solution treated at a temperature T1 below the solidus line, causing the precipitated γ' phase to dissolve into the γ-Co matrix, forming a homogeneous supersaturated solid solution. Subsequently, aging heat treatment is performed at temperature T2 to precipitate the ordered L12-γ'-Co3(Al,W) phase, forming a precursor structure with γ / γ' dual phases coexisting.

[0060] In some embodiments, the acidic electrolyte is 0.48 M~0.53 M H2SO4 or aqua regia; the chemical dealloying time is: 70 h~75 h for H2SO4 treatment, or 5 min~10 min for aqua regia treatment.

[0061] In one example embodiment, the preparation method of the hydrogen evolution catalytic material having a γ' phase nanoarray structure includes the following specific processes:

[0062] (1) The raw materials consist of cobalt particles (99.99%), aluminum particles (99.99%) and tungsten particles (99.99%).

[0063] (2) Weigh the cobalt, aluminum and tungsten particles from step (1) in a ratio of 81~83:8~10:9~10 and prepare Co-xAl-yW alloy ingots by vacuum suspension melting furnace. High-purity Ar gas is introduced into the furnace chamber three times to remove oxygen and prevent oxidation during the melting process. The alloy ingots are repeatedly melted three times to homogenize the composition.

[0064] (3) Cut the alloy ingot from step (2) into small metal blocks of the same area by wire cutting, remove the oxide scale by sanding, and carry out heat treatment in a muffle furnace; control the temperature at T1 (1280℃ < T1 < 1325℃) for solution treatment for 12 h, then water cooling for 5 min, then age at T2 (870℃ < T2 < 950℃) for 10 h, and finally water cooling for 5 min; the metal blocks after solution and aging heat treatment are sanded and polished with sandpaper and polishing machine, and then ultrasonically washed in alcohol.

[0065] (4) Place the heat-treated metal block that has been pretreated in step (3) in an acidic electrolyte for chemical dealloying treatment; wherein, 0.48 M~0.53 M H2SO4 is used for 70 h~75 h, or aqua regia is used for 5 min~10 min.

[0066] Combination Figure 1 As shown, the hydrogen evolution catalyst of the present invention has a γ' phase nanoarray structure, such as... Figure 1 The middle part consists of a single γ' phase nanounit. In acidic solution, the hydrogen evolution reaction first proceeds through the Volmer electrochemical adsorption step, where H in the solution... + Electrons are gained on the catalyst surface, and adsorption forms adsorbed hydrogen atoms (H). * ;

[0067] Subsequently, the adsorbed hydrogen atoms H * Hydrogen generation is achieved via the Heyrovsky or Tafel pathway: In the Heyrovsky reaction, adsorbed hydrogen atoms H... * With free H +The electrons react to generate H2 and then desorb; while in the Tafel reaction, two adjacent adsorbed states of H2... * They combine through chemical reactions to generate H2 and then desorb.

[0068] To facilitate better understanding, the present invention will be further illustrated below with several specific examples, but the preparation process is not limited to these examples, and the content of the present invention is not limited to these examples.

[0069] Unless otherwise specified, the following embodiments are all conventional methods.

[0070] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0071] Example 1

[0072] (1) The raw materials consist of cobalt particles (99.99%), aluminum particles (99.99%) and tungsten particles (99.99%).

[0073] (2) Weigh the cobalt, aluminum and tungsten particles from step (1) in a ratio of 82:9:9 and prepare Co-9Al-9W alloy ingots by vacuum suspension melting furnace. High-purity Ar gas is introduced into the furnace chamber three times to remove oxygen and prevent oxidation during the melting process. The alloy ingots are repeatedly melted three times to homogenize the composition.

[0074] (3) To facilitate subsequent experiments, the alloy ingot from step (2) was cut into small metal blocks of the same area using wire cutting (size 5 mm × 5 mm × 1 mm, cut into 110 blocks), and each metal block was treated as follows:

[0075] The sample was polished sequentially with 240-grit and 400-grit sandpaper for 3-4 minutes to remove the oxide scale. Then, it underwent a heat treatment process in a muffle furnace: solution treatment at 1300℃ for 12 hours, followed by water cooling for 5 minutes, aging at 900℃ for 10 hours, and finally water cooling for 5 minutes. The solution-treated and aged metal block was then polished with sandpaper and a polishing machine (in sequence from 240-grit, 400-grit, 600-grit, 800-grit, 1000-grit, 1200-grit, 1500-grit, and 2000-grit, polishing for 12-15 minutes, rotating the sample 90° each time the sandpaper was changed); subsequently, it was polished on a polishing machine at 500 rpm using silica polishing fluid until the sample surface was free of scratches and impurities). Finally, it was washed twice in alcohol for 3 minutes each time.

[0076] (4) The heat-treated metal block pretreated in step (3) is placed in a 0.5 M H2SO4 corrosion solution for chemical dealloying for 72 h to obtain the desired sample.

[0077] Example 2

[0078] (1) The raw materials consist of cobalt particles (99.99%), aluminum particles (99.99%) and tungsten particles (99.99%).

[0079] (2) Weigh the cobalt, aluminum and tungsten particles from step (1) in a ratio of 82:9:9 and prepare Co-9Al-9W alloy ingots by vacuum suspension melting furnace. High-purity Ar gas is introduced into the furnace chamber three times to remove oxygen and prevent oxidation during the melting process. The alloy ingots are repeatedly melted three times to homogenize the composition.

[0080] (3) To facilitate subsequent experiments, the alloy ingot from step (2) was cut into small metal blocks of the same area using wire cutting (size 5 mm × 5 mm × 1 mm, cut into 110 blocks), and each metal block was treated as follows:

[0081] The sample was polished sequentially with 240-grit and 400-grit sandpaper for 3-4 minutes to remove the oxide scale. Then, it underwent a heat treatment process in a muffle furnace: solution treatment at 1300℃ for 12 hours, followed by water cooling for 5 minutes, aging at 900℃ for 10 hours, and finally water cooling for 5 minutes. The solution-treated and aged metal block was then polished with sandpaper and a polishing machine (in sequence from 240-grit, 400-grit, 600-grit, 800-grit, 1000-grit, 1200-grit, 1500-grit, and 2000-grit, polishing for 12-15 minutes, rotating the sample 90° each time the sandpaper was changed); subsequently, it was polished on a polishing machine at 500 rpm using silica polishing fluid until the sample surface was free of scratches and impurities). Finally, it was washed twice in alcohol for 3 minutes each time.

[0082] (4) Place the heat-treated metal block that has been pretreated in step (3) in aqua regia for chemical dealloying for 5 minutes to obtain the desired sample.

[0083] Example 3

[0084] (1) The raw materials consist of cobalt particles (99.99%), aluminum particles (99.99%) and tungsten particles (99.99%).

[0085] (2) Weigh the cobalt, aluminum and tungsten particles from step (1) in a ratio of 82:9:9 and prepare Co-9Al-9W alloy ingots by vacuum suspension melting furnace. High-purity Ar gas is introduced into the furnace chamber three times to remove oxygen and prevent oxidation during the melting process. The alloy ingots are repeatedly melted three times to homogenize the composition.

[0086] (3) To facilitate subsequent experiments, the alloy ingot from step (2) was cut into small metal blocks of the same area using wire cutting (size 5 mm × 5 mm × 1 mm, cut into 110 blocks), and each metal block was treated as follows:

[0087] The sample was polished sequentially with 240-grit and 400-grit sandpaper for 3-4 minutes to remove the oxide scale. Then, it underwent a heat treatment process in a muffle furnace: solution treatment at 1300℃ for 12 hours, followed by water cooling for 5 minutes, aging at 900℃ for 10 hours, and finally water cooling for 5 minutes. The solution-treated and aged metal block was then polished with sandpaper and a polishing machine (in sequence from 240-grit, 400-grit, 600-grit, 800-grit, 1000-grit, 1200-grit, 1500-grit, and 2000-grit, polishing for 12-15 minutes, rotating the sample 90° each time the sandpaper was changed); subsequently, it was polished on a polishing machine at 500 rpm using silica polishing fluid until the sample surface was free of scratches and impurities). Finally, it was washed twice in alcohol for 3 minutes each time.

[0088] (4) Place the heat-treated metal block that has been pretreated in step (3) in aqua regia for chemical dealloying for 10 minutes to obtain the desired sample.

[0089] Material characterization

[0090] [SEM and EDS]

[0091] SEM and EDS tests were performed on the samples from Examples 1, 2, and 3. The results are as follows: Figures 2-7 As shown.

[0092] Figure 2 The image shows the SEM morphology of the sample from Example 1. Due to the electrochemical differences between the γ / γ′ phases, the Co and Al-rich γ-Co matrix phase preferentially dissolves, and the corrosion-resistant L12-γ'-Co3(Al,W) phase forms an L12-γ'-Co3W nanoarray structure. Quantitative analysis of the geometric characteristics of the nanoarray shows that the length ranges from 86 nm to 109 nm and the width ranges from 61 nm to 76 nm. During the selective dissolution process, the active sites exposed on the surface react with H2SO4 to produce partial dissolution, forming a local concentration gradient at the reaction interface. This causes the Co and W atoms to rearrange, resulting in a reduction in the size of the rectangular nanoarray.

[0093] Figure 3SEM-EDS showed that the relative content of elements in the nanoarray was Co:Al:W = 68.2:6.5:25.3 (at. %). The matrix phase between the nanoarrays was dissolved to form trenches. The SEM morphology showed that the surface of the nanoarray was covered by CoO and / or Co3O4, WO3 and Al2O3 nanosheet oxides to form a passivation film. With long-term selective dissolution, the surface oxides dissolved, exposing more Co and W active sites.

[0094] Figure 4 The image shows the SEM morphology of the sample from Example 2. After selective dissolution of the γ-Co phase, many shallow grooves were formed on the surface. The W-rich L12-γ′-Co3(Al,W) region was subsequently transformed into an L12-γ′-Co3W nanoarray. Quantitative analysis of the geometric characteristics of the nanoarray showed that the length was in the range of 91 nm to 112 nm and the width was in the range of 68 nm to 83 nm. This was slightly smaller than the size of the precipitated phase after heat treatment (length 97 nm to 124 nm, width 72 nm to 93 nm). This size reduction was consistent with the microstructure inheritance mechanism, confirming the phase selective dissolution process.

[0095] Figure 5 SEM-EDS showed that the relative contents of elements were Co:Al:W = 83.03:6.98:9.99 (at. %). The decrease in Al content indicates that the γ-Co phase was preferentially dissolved during the dissolution process. The surface of the L12-γ′-Co3W nanoarray was covered by nanosheet oxide structures (white lines covering the sample surface in the SEM morphology image). These CoO and / or Co3O4, WO3 and Al2O3 oxides are surface passivation films formed after exposure to air.

[0096] Figure 6 The image shows the SEM morphology of the sample from Example 3. Excessive dissolution removes oxides from the surface of the nanoarray, while some nanoarrays are separated by deeper trenches and gaps, forming an L / Z-shaped right-angle structure. Quantitative analysis of the geometric features of the nanoarray shows that the length is in the range of 75 nm to 96 nm and the width is in the range of 47 nm to 68 nm. Over-corrosion at the edges causes the L12-γ'-Co3W nanoarray to become rounded and its size to decrease, which is due to the strong acidity of aqua regia.

[0097] Figure 7SEM-EDS showed that the relative content of elements in the nanoarray was Co:Al:W = 78.8:8.8:12.4 (at. %). As the selective dissolution time was extended to 10 min, the γ-Co phase further dissolved, and the content of Co on the surface decreased from 83.03% to 78.8%. The SEM morphology showed that the nanosheet oxides on the surface of the L12-γ'-Co3W nanoarray gradually disappeared, indicating that the surface oxide content decreased significantly with the deepening of dissolution. The decrease in oxide content led to accelerated surface dissolution and structural instability, resulting in spheroidization of the nanoarray, a decrease in specific surface area, and a decline in HER activity.

[0098] [XRD]

[0099] XRD tests were performed on the samples from Examples 2 and 3, and the results are as follows: Figure 8 As shown.

[0100] The results showed that peak fitting confirmed that both samples possessed both the γ-Co phase and the L12-γ'-Co3W phase; among them, for Figure 8 In part a, chemically de-alloying in aqua regia for 5 min, the L12-γ'-Co3W phase accounted for 66.72%, while γ-Co accounted for 33.28%. This indicates that the L12-γ'-Co3W tetragonal phase was significantly enriched compared with the heat-treated precursor. This phase transformation is due to the preferential dissolution of the Al-rich γ-Co matrix during the de-alloying process.

[0101] for Figure 8 In part b, after chemical dealloying in aqua regia for 10 min, the proportion of the L12-γ'-Co3W phase decreased to 64.08%, while γ-Co accounted for 35.92%. Compared with the L12-γ'-Co3W phase after chemical dealloying for 5 min, the peak area decreased slightly, which is attributed to excessive edge dissolution and partial degradation of the nanoarray due to prolonged exposure in aqua regia, consistent with SEM-EDS observations. The results confirm that selective phase dealloying dominated by microstructure inheritance makes the L12-γ'-Co3W nanoarray the dominant surface phase.

[0102] The above characterization results demonstrate that the present invention has successfully prepared the desired hydrogen evolution catalyst material with a γ' phase nanoarray structure.

[0103] Hydrogen evolution catalytic performance testing and durability testing

[0104] The comparison samples used in the test included:

[0105] Pure cobalt sample: 50μm thick metallic cobalt foil (99.99%) purchased directly.

[0106] Co-9Al-9W@HT: Co-9Al-9W alloy sample after solution treatment and aging heat treatment (not yet de-alloyed, heat treatment conditions are the same as in the example);

[0107] Co-9Al-9W@3 min in AR: The preparation process differs from Example 2 in that it is de-alloyed in aqua regia for 3 min.

[0108] The hydrogen evolution reaction performance of the samples from Examples 1, 2, and 3 was tested. Electrochemical testing employed a three-electrode system: Ag / AgCl as the reference electrode, a platinum sheet as the counter electrode, and the test sample as the working electrode. The electrolyte was 0.5 M H₂SO₄. All experiments were conducted at room temperature (25 °C) using a CS350 electrochemical workstation. Cyclic voltammetry (CV) was used to scan the double-layer capacitance (Cdl) values ​​in 0.5 M H₂SO₄ between -0.31 V and -0.21 V (Ag / AgCl). Electrochemical impedance spectroscopy (EIS) was measured at a voltage of 5 mV in the frequency range of 100 kHz to 0.01 Hz. The LSV scanning potential range was -0.8 V to -0.3 V, and the scan rate was 5 mV·s. -1 The result is as follows Figure 9 As shown.

[0109] The results showed that the sample in Example 1 was at 10 mA·cm⁻¹ -2 Under these conditions, it exhibits an overpotential of 163 mV and a voltage of 63.8 mV·dec. -1 The Tafel slope exhibits excellent performance. During selective dissolution, the dissolution of the surface passivation film exposes more Co and W active sites. The cooperative electronic interaction between Co and W atoms optimizes the adsorption free energy of hydrogen and accelerates the reaction kinetics. Due to the microcouple effect between the L12-γ'-Co3(Al,W) phase and the γ-Co matrix phase, a more complex semi-circular inductive impedance response is observed, which increases the reaction energy barrier and leads to an increase in the Tafel slope. The kinetics of the HER reaction conform to the Volmer-Heyrovsky mechanism.

[0110] During chemical dealloying in aqua regia for 5 min (sample of Example 2), most of the γ-Co matrix phase was removed, while the surface was dominated by the L12-γ'-Co3W nanoarray with a high active surface area rich in catalytically active Co and W. As the solution continued to dealloy inward along the grooves left by the γ-Co matrix phase, this process exposed more Co and W active sites, forming a highly electrocatalytically active region at the interface, thereby improving the HER catalytic activity. In acidic media, the hydrogen evolution reaction on the L12-γ'-Co3W nanoarray mainly proceeded through the Volmer-Tafel mechanism at 10 mA·cm⁻¹. -2Under these conditions, it exhibits an overpotential of 140 mV and a voltage of 28.8 mV·dec. -1 The excellent performance of Tafel slope;

[0111] When the aqua regia is chemically de-alloyed for 10 min (sample of Example 3), some nanoarrays are separated by deeper trenches and gaps, forming L / Z-shaped right-angled structures. At the same time, the edges of the nanoarrays become spherical, reducing the number of active sites, increasing charge transfer resistance, and decreasing hydrogen evolution performance.

[0112] The sample from Example 2 was subjected to a durability test of 5000 LSV cycles, and the results are shown in Figures 10 and 10. Figure 11 As shown.

[0113] Figure 10 The results show that as the number of cycles increases, the nanoarray structure gradually collapses, forming stacked sheet structures and irregular cauliflower-shaped spherical clumps at the ends. Therefore, the structure of the L12-γ'-Co3W nanoarray is destroyed, reducing the number of active sites and hindering the penetration of electrolytes into these sites, thereby reducing HER activity.

[0114] like Figure 11 As shown, after 5000 cycles, the catalyst at 10 mA·cm⁻¹ -2 The overpotential dropped by only 32 mV at 100 mA·cm⁻¹ -2 The overpotential decreased by only 51 mV, and the Tafel slope decreased to 82.4 mV·dec. -1 It exhibits good electrochemical stability.

[0115] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A hydrogen evolution catalytic material with a γ' phase nanoarray structure, characterized in that, The hydrogen evolution catalyst material includes: A cobalt-based alloy matrix, wherein the cobalt-based alloy matrix is ​​a Co-xAl-yW alloy; wherein x and y are atomic percentages, with x ranging from 8 to 10 and y ranging from 9 to 10; and A nanocatalytic layer is grown in situ on the surface of the cobalt-based alloy substrate. The nanocatalytic layer has a γ' phase nanoarray structure, which is composed of γ' phase nanounits distributed in a rectangular array.

2. The hydrogen evolution catalytic material with a γ' phase nanoarray structure according to claim 1, characterized in that, The γ' phase is an intermetallic compound with an L12-type long-range ordered structure, and the intermetallic compound is Co3W; the γ' phase nanounits have a regular rectangular block morphology on the surface of the cobalt-based alloy matrix, and there are nanoscale gaps between each nanounit.

3. The hydrogen evolution catalyst material with a γ' phase nanoarray structure according to claim 1 or 2, characterized in that, The surface of the γ' phase nanounit is coated with an in-situ generated composite oxide layer, the composition of which includes oxides of cobalt, oxides of tungsten, and oxides of aluminum.

4. The hydrogen evolution catalytic material with a γ' phase nanoarray structure according to claim 1, characterized in that, Based on the peak fitting calculation of X-ray diffraction pattern, the peak area of ​​the γ' phase diffraction peak accounts for 60% to 70% of the total area of ​​all diffraction peaks.

5. The hydrogen evolution catalytic material with a γ' phase nanoarray structure according to claim 1, characterized in that, The dimensions of the nanounits are: length 75 nm to 120 nm, width 45 nm to 85 nm.

6. The hydrogen evolution catalytic material with a γ' phase nanoarray structure according to claim 1, characterized in that, The value of x ranges from 9 to 9.2, and the value of y ranges from 9 to 9.

2.

7. The hydrogen evolution catalytic material with a γ' phase nanoarray structure according to claim 1, characterized in that, The γ' phase nanoarray structure is formed by solution aging of the cobalt-based alloy matrix, utilizing phase separation of the γ phase and γ' phase, and selective etching.

8. A method for preparing a hydrogen evolution catalytic material with a γ' phase nanoarray structure as described in any one of claims 1-7, characterized in that, Includes the following steps: Cobalt, aluminum and tungsten raw materials are weighed according to atomic percentage and smelted to prepare Co-xAl-yW alloy ingots, wherein the value of x ranges from 8 to 10 and the value of y ranges from 9 to 10. The Co-xAl-yW alloy ingot was subjected to solution treatment and aging to obtain a cobalt-based alloy precursor with a two-phase structure of γ and γ'. The cobalt-based alloy precursor is placed in an acidic electrolyte for chemical dealloying treatment to selectively remove part of the γ phase, thereby forming a γ' phase nanoarray structure on the surface of the cobalt-based alloy matrix to obtain the hydrogen evolution catalyst material.

9. The method for preparing the hydrogen evolution catalytic material with a γ' phase nanoarray structure according to claim 8, characterized in that, The temperature range of the solution treatment T1 is 1200℃ < T1 < 1360℃, and the temperature range of the aging treatment T2 is 870℃ < T2 < 950℃.

10. The method for preparing the hydrogen evolution catalytic material with a γ' phase nanoarray structure according to claim 8, characterized in that, The acidic electrolyte is aqua regia or 0.48 M~0.53 M H2SO4; the chemical dealloying time is: 70 h~75 h for H2SO4 treatment, or 5 min~10 min for aqua regia treatment.

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