Preparation method of platinum quantum dots loaded on cobalt phosphide nanowire composite electrode and application thereof in hydrogen evolution reaction at all pH values

Abstract

The present invention has developed a preparation method of a platinum quantum dot-cobalt phosphide / carbon cloth composite electrode. Carbon cloth is selected as a self-supporting substrate to prepare Co(OH)F / CC through a hydrothermal reaction; Co(OH)F / CC is transformed into CoP / CC by a low-temperature phosphidation strategy; a Pt-modified Pt-CoP / C composite electrode is prepared by an electroplating method, and a Pt-P bond is constructed between the composites, improving the activity and stability of the catalyst. By using carbon cloth as a self-supporting substrate, the present invention can effectively avoid the use of a binder and the phenomenon of catalyst shedding during the reaction. Its unique nanowire structure can provide more active sites for the reaction, improving the reaction efficiency. The modification of Pt quantum dots can not only improve the kinetics in the hydrogen evolution reaction but also regulate the electronic structure arrangement of CoP. The present invention also discloses the application of the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode. The platinum quantum dot-cobalt phosphide / carbon cloth composite electrode prepared by the preparation method of the present invention exhibits excellent hydrogen evolution performance in a wide pH range.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysis, and particularly to a preparation method and application of a composite electrode in which platinum quantum dots are loaded on a cobalt phosphide nanowire array. Background Art

[0002] With the increasing depletion of traditional fossil fuels and the growing environmental problems, it is crucial to explore emerging energy sources to reduce dependence on traditional fossil fuels and lower pollution. As an emerging energy source, hydrogen energy has the advantages of high energy density and environmental friendliness, and is a good substitute for traditional fossil fuels. The electrolytic water hydrogen production technology, as an important means of obtaining hydrogen energy, has the advantages of high purity and pollution-free hydrogen production. However, limited by the solution resistance and the slow kinetics of the electrode during the hydrogen evolution reaction, the electrolytic water hydrogen production technology faces problems such as too high overpotential and poor stability. Currently, noble metal platinum is considered the most excellent hydrogen evolution reaction catalyst, but its large-scale application is limited due to its low reserves and high price. Therefore, it is crucial to explore and develop low-loading noble metal-based electrocatalysts.

[0003] Currently, transition metal phosphides, especially cobalt phosphide nanocatalysts with a trigonal prism structure, have the advantages of high conductivity, high catalytic activity, and excellent stability, and are considered efficient electrocatalytic hydrogen production catalysts. However, there is still a large gap in their hydrogen evolution performance compared with noble metals. Interface engineering is an effective method to improve the hydrogen evolution ability of cobalt phosphide nanocatalysts. Compared with single cobalt phosphide, the composite materials constructed by interface engineering can exert the synergistic effect between different components and can adjust the internal electronic structure, thereby further improving their electrocatalytic performance. Noble metal platinum can effectively reduce the energy barrier of the hydrogen evolution reaction. Therefore, the introduction of platinum quantum dots can significantly improve the hydrogen evolution performance of the catalyst. The use of Pt quantum dots can not only effectively reduce the amount of noble metal used, but also fully expose the active sites. Summary of the Invention

[0004] In order to overcome the above-mentioned disadvantages and deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of platinum quantum dot-cobalt phosphide / carbon cloth.

[0005] In the technical solution of the present invention, carbon cloth is selected as a self-supporting substrate, and Co(OH)F / CC is prepared by a hydrothermal reaction; Co(OH)F / CC is transformed into CoP / CC by a low-temperature phosphating strategy; a Pt-modified Pt-CoP / C composite electrode is prepared by an electroplating method, and a Pt-P bond is constructed between the composites, improving the activity and stability of the catalyst. The present invention uses carbon cloth as a self-supporting substrate, which can effectively avoid the use of a binder and the shedding of the catalyst during the reaction process. Moreover, as a carrier of the catalyst, carbon cloth has excellent electrical conductivity, which is beneficial to the transfer process of protons and electrons during the reaction process and accelerates the reaction. Its unique nanowire structure can provide more active sites for the reaction and improve the reaction efficiency. Finally, the modification of Pt quantum dots can not only improve the kinetics in the hydrogen evolution reaction but also regulate the electronic structure arrangement of CoP. A Pt-P bond is constructed between the Pt quantum dots and CoP to improve the adsorption-desorption performance of the catalyst, enhance the stability of the catalyst, and increase the number of active sites of the catalyst. The present invention also discloses the application of the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode. The platinum quantum dot-cobalt phosphide / carbon cloth composite electrode prepared by the preparation method of the present invention exhibits excellent hydrogen evolution performance in a wide pH range and can be well applied to the electrolytic water hydrogen evolution reaction in a wide pH range.

[0006] Another object of the present invention is to provide a platinum quantum dot-cobalt phosphide / carbon cloth composite electrode, which improves the activity of the catalyst while reducing the amount of precious metal Pt used.

[0007] Another object of the present invention is to provide the application of the above platinum quantum dot-cobalt phosphide / carbon cloth composite electrode in the electrolytic water hydrogen evolution reaction in a wide pH range.

[0008] The object of the present invention is achieved by the following technical solutions:

[0009] A preparation method of a platinum quantum dot-cobalt phosphide / carbon cloth composite electrode includes the following steps:

[0010] (1) Pretreat the carbon cloth;

[0011] (2) Prepare a cobalt hydroxyfluoride precursor Co(OH)F / CC on the carbon cloth by a hydrothermal reaction. Dissolve cobalt nitrate hexahydrate Co(NO3)2·6H2O, ammonium fluoride NH4F, and urea CO(NH2)2 in deionized water, stir evenly to form a mixed solution, and transfer it to a reaction kettle; vertically immerse the treated carbon cloth in the solution; transfer the reaction kettle to an oven for heat preservation; after cooling to room temperature, wash and dry to obtain Co(OH)F / CC;

[0012] (3) The above Co(OH)F / CC was transformed into a cobalt phosphide electrode CoP / CC grown on carbon cloth through a low-temperature phosphating strategy. The obtained Co(OH)F / CC and sodium hypophosphite were placed in two crucibles respectively and then placed in a tube furnace. They were calcined in an argon atmosphere in the order that the crucible containing sodium hypophosphite was close to the inlet end and the crucible containing Co(OH)F / CC was close to the outlet end. After cooling to room temperature, CoP / CC was obtained.

[0013] (4) A platinum quantum dot-cobalt phosphide / carbon cloth composite electrode Pt-CoP / CC grown on carbon cloth was prepared through an electroplating strategy. First, chloroplatinic acid and sodium citrate were dissolved in deionized water and stirred evenly. After adding anhydrous sodium carbonate to adjust the pH of the mixed solution, it was used as the electroplating solution. Then, an electroplating was carried out using a three-electrode system. The obtained CoP / CC above was used as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode. After the electroplating was completed, it was washed and dried to obtain Pt-CoP / CC.

[0014] Preferably, the pretreatment of the carbon cloth includes the following steps: First, it is placed in 1 M - 3 M hydrochloric acid and kept warm in an air environment at 110~130 °C for 4~6 h; and the carbon cloth is ultrasonically treated with 1 M - 3 M hydrochloric acid, absolute ethanol, and deionized water in turn for 25~30 minutes.

[0015] Preferably, the molar ratio of Co(NO3)2·6H2O:NH4F:CO(NH2)2 is 1~2:3~5:6~10; the stirring time is 15~30 min; the volume of the reaction kettle is 50 ml.

[0016] Preferably, the vertical infiltration method of the carbon cloth is to bind one end of the carbon cloth to a polytetrafluoroethylene plate and clamp the polytetrafluoroethylene plate to the inner wall of the reaction kettle.

[0017] Preferably, the specific conditions for transferring the reaction kettle to the oven for heat preservation are 120~160 °C and heat preservation for 6~12 h.

[0018] Preferably, the washing conditions are to rinse with deionized water for 3 times continuously.

[0019] Preferably, the drying conditions are to place it in an oven at a temperature of 50~70 °C and dry for 6~8 h.

[0020] The dosage relationship between Co(OH)F / CC and sodium hypophosphite is that for every 1 cm of Co(OH)F / CC -2 , the number is 1 - 5 pieces, and the mass of sodium hypophosphite is 0.2 - 5 g.

[0021] Preferably, the heating rate of the calcination condition in an argon atmosphere is 1-5 °C / min, the temperature is 300-350 °C, and the heat preservation duration is 1-3 h.

[0022] Preferably, the mass concentration of chloroplatinic acid in the electroplating solution is 1-20 g / L; the mass concentration of sodium citrate is 0.1-20 g / L.

[0023] Preferably, the specific pH value of the mixed solution adjusted with anhydrous sodium carbonate as the electroplating solution is 6.5-7.3.

[0024] Preferably, the electroplating conditions are that the temperature is 45-65 °C, the CV scanning range is -0.8V to 0.4V, the scanning rate is 20-50 mV / s, and the number of cycles is 5-15 cycles.

[0025] The beneficial effects of the present invention are as follows: The noble metal Pt prepared by the present invention exists in the form of quantum dots, effectively reducing the amount of Pt used, improving the mass activity of the catalyst, and greatly enhancing the utilization rate of Pt active sites. The CoP nanowire array structure can provide support for the loading of Pt quantum dots, preventing the aggregation of Pt quantum dots. In addition, the ordered nanowire array can provide a site for the catalytic reaction, accelerating the transport of reactants / intermediates / products, and facilitating the release of hydrogen bubbles. A Pt-P bond can be generated between Pt and CoP, and this strong coupling effect can effectively reduce the interfacial transport impedance, increase the active sites of the catalyst, prevent the shedding of active substances, thereby improving the stability and activity of the catalyst.

[0026] 1. The present invention provides a preparation method and application of a platinum quantum dot-cobalt phosphide / carbon cloth composite electrode. The preparation method of the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode includes the following steps: Selecting carbon cloth as a self-supporting substrate to prepare Co(OH)F / CC through a hydrothermal reaction; using a low-temperature phosphidation strategy to transform Co(OH)F / CC into CoP / CC; preparing a Pt quantum dot-modified Pt-CoP / C composite electrode through an electroplating method. The present invention uses carbon cloth as a self-supporting substrate, which can effectively avoid the use of binders and the shedding phenomenon of the catalyst during the reaction. And carbon cloth as a carrier of the catalyst has excellent electrical conductivity, which is beneficial to the transfer process of protons and electrons during the reaction, accelerating the reaction kinetics. Its unique nanowire structure can provide more active sites for the reaction, improving the reaction efficiency. Finally, the modification of Pt quantum dots can not only improve the catalytic activity but also adjust the electronic structure arrangement of CoP, improve the adsorption performance of the catalyst, and accelerate the progress of the reaction.

[0027] 2. The catalyst of the present invention can be used for the hydrogen evolution reaction of electrolyzed water within a wide pH range, and its hydrogen evolution performance under neutral and alkaline conditions can be comparable to that of commercial 40% Pt / C, and it has better stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a preparation flow chart of Pt-CoP / CC of the embodiment of the present invention.

[0029] Figure 2 It is an XRD pattern of the Pt-CoP / CC composite electrode prepared in Example 1.

[0030] Figure 3 It is an SEM pattern of the Pt-CoP / CC composite electrode prepared in Example 1.

[0031] Figure 4 It is a TEM pattern of the Pt-CoP / CC composite electrode prepared in Example 1.

[0032] Figure 5 It is a hydrogen evolution reaction polarization curve of the Pt-CoP / CC composite electrode prepared in Example 1 and the control group under alkaline conditions.

[0033] Figure 6 It is a comparison of the hydrogen evolution reaction stability test of the Pt-CoP / CC composite electrode prepared in Example 1 and the control group under alkaline conditions.

[0034] Figure 7 It is a hydrogen evolution reaction polarization curve of the Pt-CoP / CC composite electrode prepared in Example 1 and the control group under neutral conditions.

[0035] Figure 8 It is a comparison of the hydrogen evolution reaction stability test of the Pt-CoP / CC composite electrode prepared in Example 1 and the control group under neutral conditions.

[0036] Figure 9 It is a hydrogen evolution reaction polarization curve of the Pt-CoP / CC composite electrode prepared in Example 1 and the control group under acidic conditions.

[0037] Figure 10 It is a comparison of the hydrogen evolution reaction stability test of the Pt-CoP / CC composite electrode prepared in Example 1 and the control group under acidic conditions.

[0038] Figure 11 It is a linear sweep voltammetry curve of the catalyst prepared with different CV cycles during the electroplating process in Example 6.

[0039] Figure 12 It is a synchrotron radiation extended edge X-ray absorption spectrum of Pt-CoP.

[0040] Figure 13 Hydrogen bubble contact angles and bubble evolution behaviors of Pt-CoP and 40% Pt / C noble metal are compared.

[0041] Figure 14 Impedance spectra of Pt-CoP and CoP are shown.

[0042] Figure 15 Comparison chart of active areas of Pt-CoP and CoP is shown. Specific implementation manners

[0043] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the implementation manners of the present invention are not limited thereto.

[0044] Embodiment 1

[0045] As Figure 1 shown, the preparation method of the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode of this embodiment includes the following steps:

[0046] S1 Prepare Co(OH)F / CC by hydrothermal reaction:

[0047] (1) Pretreat the carbon cloth: 1. Immerse the carbon cloth in 3 M hydrochloric acid and keep it warm in an air environment at 120 °C for 4 h. 2. Then ultrasonically treat the carbon cloth with 3 M hydrochloric acid, absolute ethanol, and deionized water in sequence for 30 minutes;

[0048] (2) Dissolve 1 mmol of cobalt nitrate, 3 mmol of ammonium fluoride, and 6 mmol of urea in 20 ml of deionized water, stir evenly to obtain a mixed solution, and transfer it to a reaction kettle; Bind one end of the carbon cloth to a polytetrafluoroethylene plate and vertically immerse it in the mixed solution, keep it warm at 120 °C for 6 h, rinse the hydrothermally treated carbon cloth with deionized water, repeat 3 times, and place it in an oven at 60 °C to dry for 6 h to obtain Co(OH)F / CC;

[0049] S2 Convert the above Co(OH)F / CC into a CoP / CC electrode by a low-temperature phosphidation strategy:

[0050] Place the obtained Co(OH)F / CC (area 1 cm -2 , quantity 3 pieces) and 2 g of sodium hypophosphite in a tube furnace, heat it at a heating rate of 2 °C / min to 300 °C in the order of sodium hypophosphite near the inlet end and Co(OH)F / CC near the outlet end, and keep it at this temperature for 2 h. After cooling to room temperature, CoP / CC is obtained;

[0051] S3 Prepare a Pt-CoP / CC composite electrode by an electroplating strategy:

[0052] First, dissolve 1.0 g of chloroplatinic acid and 0.19 g of sodium citrate in 250 ml of deionized water, stir well, and add anhydrous sodium carbonate to adjust the pH of the mixed solution to 7.0 as the electroplating solution. Then, electroplate using a three-electrode system. Use the obtained CoP / CC as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode. The scanning range is -0.8 to 0.4 V vs. Ag / AgCl, the scanning rate is 50 mV / s, the number of scanning cycles is 10, and the electroplating temperature is 60 °C. After electroplating, rinse the carbon cloth with deionized water, repeat 3 times, and place it in an oven at 60 °C for drying for 6 h.

[0053] Perform electrochemical tests on the Pt-CoP / CC composite electrode prepared in the above examples. All electrochemical tests are carried out on a CHI660E electrochemical workstation (Shanghai Chenhua). The test parameters are as follows: Use the prepared Pt-CoP / CC composite electrode as the working electrode, a carbon rod electrode as the counter electrode. Under alkaline conditions, the electrolyte is 1.0 M KOH (pH = 14.0), and Hg / HgO is used as the reference electrode. The scanning range of the LSV curve is -0.8 V to -1.45 V vs. Hg / HgO, and the scanning rate is 5 mV s -1 ; Under neutral conditions, the electrolyte is 1.0 M PBS (pH = 7.0), Ag / AgCl is used as the reference electrode, and the scanning range of the LSV curve is -0.52 V to -1.22 V vs. Ag / AgCl, and the scanning rate is 5 mV s -1 ; Under acidic conditions, the electrolyte is 0.5 M H2SO4 (pH = 0.0), Ag / AgCl is used as the reference electrode, and the scanning range of the LSV curve is 0 V to -0.8 V vs. Ag / AgCl, and the scanning rate is 5 mV s -1 . All potentials are converted to the standard hydrogen electrode (RHE) according to the Nernst equation, i.e., E RHE = E Hg / HgO + 0.0592 × pH + 0.098 and E RHE =E Ag / AgCl + 0.0591 × pH + 0.197 for subsequent comparison. Before all LSV curve tests, perform CV scans in the corresponding range for 20 cycles to activate the electrode. The scanning rate of CV is 50 mV s -1 , and the scanning rate when measuring LSV is 5 mV s -1 , and 85% IR compensation is performed for all.

[0054] The preparation of the 40% Pt / C electrode in the control group is as follows: First, dissolve 5.00 mg of 40% Pt / C and 5.00 mg of carbon black in a mixed solution containing 980.0 μL of absolute ethanol and 20.0 μL of naphthol, and ultrasonicate for 30 min at room temperature to obtain a uniform catalyst ink. Then, drop 100.0 μL of the catalyst ink onto a carbon cloth of 1.0 × 1.0 cm 2 and dry it to be used as the working electrode.

[0055] The test and detection results are shown in the attached figures as follows.

[0056] Figure 2 XRD pattern of the Pt-CoP / CC composite electrode prepared in Example 1. The main components of the sample are CoP and Pt.

[0057] Figure 3 SEM image of the Pt-CoP / CC composite electrode prepared in Example 1. The vertical nanowire array structure shown is beneficial for the transfer of intermediate products during the reaction and exposes more active sites.

[0058] Figure 4 TEM image of the Pt-CoP / CC composite electrode prepared in Example 1, further verifying its composite nanowire structure, and Pt exists in the form of quantum dots (circled in yellow).

[0059] Figure 5 Hydrogen evolution reaction polarization curves of the Pt-CoP / CC composite electrode (triangular line) prepared in Example 1 and the control group under alkaline conditions. The 40% Pt / C electrode in the control group (star line) is a carbon cloth dropped with commercial 40% Pt / C catalyst; the CoP / CC electrode (circular line) is the CoP / CC electrode obtained after Step S2; the CC electrode (square line) is the treated carbon cloth. The Pt-CoP / CC electrode only requires overpotentials of 18 mV and 93 mV to reach current densities of 10 mA cm -2 and 100 mA cm -‍2 , which can be comparable to the η 10 = 15 mV and η 100 = 98 mV of the commercial 40% Pt / C electrode, and is significantly better than the η 10 = 84 mV and η 100 = 169 mV of the CoP / CC electrode and the CC electrode. And as the current density gradually increases, the hydrogen evolution performance of the Pt-CoP / CC electrode is significantly better than that of the commercial 40% Pt / C electrode.

[0060] Figure 6Hydrogen evolution reaction stability test comparison of the Pt-CoP / CC composite electrode (triangle-style line) prepared in Example 1 and the control group under alkaline conditions. The control group 40% Pt / C electrode (star-style line) is a carbon cloth dripped with commercial 40% Pt / C catalyst; it can be clearly seen that at a current density of 100 mA cm -2 the Pt-CoP / CC electrode exhibits better stability and lower overpotential.

[0061] Figure 7 Hydrogen evolution reaction polarization curves of the Pt-CoP / CC composite electrode (triangle-style line) prepared in Example 1 and the control group under neutral conditions. The control group 40% Pt / C electrode (star-style line) is a carbon cloth dripped with commercial 40% Pt / C catalyst; the CoP / CC electrode (circle-style line) is the CoP / CC electrode obtained after step S2; the CC electrode (square-style line) is the treated carbon cloth. The Pt-CoP / CC electrode only requires overpotentials of 26.3 mV and 341.3 mV to reach current densities of 10 mA cm -2 and 100 mA cm -‍2 which are better than the η 10 = 31.3 mV and η 100 = 382.3 mV of the commercial 40% Pt / C electrode and the η 10 = 132.3 mV and η 100 = 605.3 mV of the CoP / CC electrode and the CC electrode. And as the current density gradually increases, the hydrogen evolution performance of the Pt-CoP / CC electrode is significantly better than that of the commercial 40% Pt / C electrode.

[0062] Figure 8 Hydrogen evolution reaction stability test comparison of the Pt-CoP / CC composite electrode (triangle-style line) prepared in Example 1 and the control group under neutral conditions. The control group 40% Pt / C electrode (star-style line) is a carbon cloth dripped with commercial 40% Pt / C catalyst; it can be clearly seen that at a current density of 10 mA cm -2 the Pt-CoP / CC electrode exhibits better stability and lower overpotential.

[0063] Figure 9The hydrogen evolution reaction polarization curves of the Pt-CoP / CC composite electrode (triangle-style line) prepared in Example 1 and the control group under acidic conditions. Among them, the control group 40% Pt / C electrode (star-style line) is a carbon cloth dropped with a commercial 40% Pt / C catalyst; the CoP / CC electrode (circle-style line) is the CoP / CC electrode obtained after Step S2; the CC electrode (square-style line) is the treated carbon cloth. The Pt-CoP / CC electrode requires overpotentials of 79 mV and 134 mV respectively to reach current densities of 10 mA cm -2 and 100 mA cm -2 . The performance is slightly worse than that of the commercial 40% Pt / C electrode with η 10 = 56 mV and η 100 = 99 mV, but significantly better than that of the CoP / CC electrode with η 10 = 105 mV and η 100 = 191 mV.

[0064] Figure 10 The comparison of the hydrogen evolution reaction stability tests of the Pt-CoP / CC composite electrode (triangle-style line) prepared in Example 1 and the control group under acidic conditions. Among them, the control group 40% Pt / C electrode (star-style line) is a carbon cloth dropped with a commercial 40% Pt / C catalyst; it can be clearly seen that at a current density of 100 mA cm -‍2 , Pt-CoP / CC exhibits better stability and lower overpotential.

[0065] Example 2

[0066] The difference between this example and Example 1 is that in the process of preparing Co(OH)F / CC by hydrothermal reaction described in Step S1, 1 mmol of cobalt nitrate, 5 mmol of ammonium fluoride, and 10 mmol of urea are dissolved in 20 ml of deionized water and stirred evenly to obtain a mixed solution, which is then transferred to a reaction kettle; one end of the carbon cloth is bound to a polytetrafluoroethylene plate and vertically immersed in the mixed solution and kept at 120 °C for 6 h. The hydrothermally treated carbon cloth is rinsed with deionized water 3 times and placed in an oven at 60 °C for 6 h to obtain Co(OH)F / CC; the others are the same as in Specific Example 1.

[0067] Example 3

[0068] The difference between this example and Example 1 is as follows: In the process of preparing Co(OH)F / CC by hydrothermal reaction in step S1, 1 mmol of cobalt nitrate, 3 mmol of ammonium fluoride, and 6 mmol of urea were dissolved in 20 ml of deionized water, stirred evenly to obtain a mixed solution, and then transferred to a reaction kettle. One end of the carbon cloth was bound to a polytetrafluoroethylene plate and vertically immersed in the mixed solution, and kept at 160 °C for 6 h. After hydrothermal treatment, the carbon cloth was rinsed with deionized water, repeated 3 times, and then placed in an oven at 60 °C and dried for 6 h to obtain Co(OH)F / CC. Others are the same as in Specific Example 1.

[0069] Example 4

[0070] The difference between this example and Example 1 is as follows: In the process of converting the above Co(OH)F / CC into a CoP / CC electrode by using a low-temperature phosphating strategy in step S2, the obtained Co(OH)F / CC and 1 g of sodium hypophosphite were placed in a tube furnace. In the order of sodium hypophosphite close to the inlet end and Co(OH)F / CC close to the outlet end, the temperature was raised to 350 °C at a heating rate of 2 °C / min and kept at this temperature for 2 h. After cooling to room temperature, CoP / CC was obtained. Others are the same as in Specific Example 1.

[0071] Example 5

[0072] The difference between this example and Example 1 is as follows: In the process of converting the above Co(OH)F / CC into a CoP / CC electrode by using a low-temperature phosphating strategy in step S2, the obtained Co(OH)F / CC and 1 g of sodium hypophosphite were placed in a tube furnace. In the order of sodium hypophosphite close to the inlet end and Co(OH)F / CC close to the outlet end, the temperature was raised to 300 °C at a heating rate of 2 °C / min and kept at this temperature for 1 h. After cooling to room temperature, CoP / CC was obtained. Others are the same as in Specific Example 1.

[0073] Example 6

[0074] The difference between this example and Example 1 is as follows: In the electroplating strategy described in step S3, the obtained CoP / CC was used as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode. The scanning range was -0.8~0.4 V vs. Ag / AgCl, the scanning rate was 50 mV / s, the number of scanning cycles was 5, and the electroplating temperature was 60 °C. After electroplating, the carbon cloth was rinsed with deionized water, repeated 3 times, and then placed in an oven at 60 °C and dried for 6 h. Others are the same as in Specific Example 1. Figure 11Linear sweep voltammetry curves of the catalysts prepared with different CV cycle numbers during the electroplating process in Example 6. From the results of the linear sweep voltammetry curves, it can be seen that when the CV cycle number is 10 during the electroplating process, the prepared catalyst exhibits the optimal catalytic performance. When the electroplating cycle number is 5, due to the low Pt loading and insufficient number of active sites, the performance is average. When the electroplating cycle number is 15, due to the excessive Pt loading, some Pt quantum dots agglomerate, resulting in performance degradation. Therefore, 10 electroplating cycles are more appropriate.

[0075] Figure 12 X-ray absorption near edge structure (XANES) spectra of Pt-CoP obtained in Example 6. From the XANES spectra of Pt-CoP, it can be seen that there is a strong coupling between Pt quantum dots and CoP through Pt-P bonds. This strong interaction between heterogeneous phases can effectively reduce the interfacial charge transfer resistance, thereby enhancing the reaction kinetics. In addition, this interfacial chemical bond can increase the active sites of the catalyst, improve the activity of the catalyst, and this strongly coupled chemical bond can prevent the detachment of active substance Pt quantum dots, thus enhancing the overall stability of the catalyst.

[0076] Figure 13 Comparison of the hydrogen bubble contact angles and bubble evolution behaviors of Pt-CoP and noble metal 40% Pt / C obtained in Example 6. From the comparison of the hydrogen bubble contact angles of Pt-CoP and noble metal 40% Pt / C, it can be seen that Pt-CoP has a larger hydrogen bubble contact angle, indicating that the adhesion force of hydrogen bubbles on the surface of the Pt-CoP electrode is weak and it is easy to evolve. The 40% Pt / C electrode shows a tendency of rapid hydrogen bubble adsorption due to its gasophilicity, which indicates that it is difficult for hydrogen bubbles to desorb from the surface of 40% Pt / C. In addition, from the pictures of the bubble evolution behavior, it can be seen that the surface of the 40% Pt / C electrode is easily blocked by the gas film, thus affecting the desorption of hydrogen bubbles. On the Pt-CoP electrode, it can be clearly observed that the formed bubbles are more likely to detach. This phenomenon can be attributed to the fact that the modification of CoP nanowires with Pt quantum dots can effectively increase the electrochemically active area, reduce the electron transfer resistance, and the array structure of CoP nanowires is conducive to the exposure of active sites, which can accelerate the release of hydrogen bubbles.

[0077] Figure 14 Impedance spectra of Pt-CoP / CC and CoP / CC obtained in Example 6. From the impedance spectra of Pt-CoP / CC and CoP / CC, it can be seen that the electron transfer impedance is greatly reduced after the modification of CoP nanowires with Pt quantum dots, which is beneficial to the rapid transfer of electrons during the reaction of the catalyst, confirming that the modification of Pt quantum dots helps to enhance the reaction kinetics.

[0078] Figure 15Figure showing the comparison of the active areas of Pt-CoP / CC and CoP / CC obtained in Example 6. From the comparison figure of the active areas of Pt-CoP and CoP, it can be seen that Pt-CoP has a larger electrochemically active surface area. A large active area is conducive to the exposure of active sites during the hydrogen evolution reaction process, accelerating the reaction. This result confirms that the modification of Pt quantum dots is beneficial to improving the overall performance of the catalyst.

Claims

1. A method for preparing a platinum quantum dot-cobalt phosphide / carbon cloth composite electrode, characterized in that: The following steps are involved: (1) Pretreating the carbon cloth; preparing the hydroxy cobalt fluoride precursor Co(OH)F / CC on the carbon cloth by hydrothermal reaction; (2) converting the Co(OH)F / CC obtained in step (1) into a cobalt phosphide electrode CoP / CC electrode grown on carbon cloth by low temperature phosphating; (3) electroplating platinum quantum dots on the surface of the cobalt phosphide electrode CoP / CC electrode grown on the carbon cloth obtained in step (1) to obtain a platinum quantum dot-cobalt phosphide / carbon cloth composite electrode Pt-CoP / CC grown on the carbon cloth; In step (3), chloroplatinic acid and sodium citrate are dissolved in water, stirred evenly, and anhydrous sodium carbonate is added to adjust the pH of the mixed solution to prepare an electroplating solution, followed by electroplating using a three-electrode system, wherein the CoP / CC obtained above is used as a working electrode, a carbon rod is used as a counter electrode, and Ag / AgCl is used as a reference electrode. After the electroplating is completed, the solution is washed and dried to obtain Pt-CoP / CC; the mass concentration of chloroplatinic acid in the electroplating solution is 1-20 g / L; the mass concentration of sodium citrate is 0.1-20 g / L; The specific pH value of the electroplating solution after adding anhydrous sodium carbonate to adjust the pH of the mixed solution is 6.5-7.3; the electroplating conditions are as follows: the temperature is 45-65° C., the CV scanning range is -0.8V-0.4V, the scanning speed is 20-50mV / s, and the number of circles is 10.

2. The method for preparing the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode according to claim 1, characterized in that: In the step (1), cobalt nitrate hexahydrate Co(NO3)2·6H2O, ammonium fluoride NH4F, and urea CO(NH2)2 are dissolved in water, stirred evenly to form a mixed solution, and transferred to a reactor; the treated carbon cloth is vertically immersed in the mixed solution; the reactor is transferred to an oven for heat preservation; and after cooling to room temperature, the mixture is washed and dried to obtain Co(OH)F / CC.

3. The method for preparing the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode according to claim 1, characterized in that: The molar ratio of Co(NO3)2·6H2O:NH4F:CO(NH2)2 is 1~2:3~5:6~10.

4. The method for preparing the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode according to claim 1, characterized in that: The carbon cloth vertical infiltration method is to bind one end of the carbon cloth to a polytetrafluoroethylene plate and clamp the polytetrafluoroethylene plate to the inner wall of the reactor so that the carbon cloth is vertically immersed below the liquid surface. The hydrothermal reaction temperature is 120-160°C and the hydrothermal reaction time is 6-12h.

5. The method for preparing the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode according to claim 1, characterized in that: In step (2), the obtained Co(OH)F / CC and sodium hypophosphite are placed in two crucibles respectively and placed in a tubular furnace. The crucibles containing sodium hypophosphite are placed close to the gas inlet end and the crucible containing Co(OH)F / CC is placed close to the gas outlet end. The crucibles are calcined in an argon atmosphere and cooled to room temperature to obtain CoP / CC.

6. The method for preparing the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode according to claim 5, characterized in that: The dosage of Co(OH)F / CC and sodium hypophosphite is as follows: -2 The mass of sodium hypophosphite is 0.2-5g; the Co(OH)F / CC is 1-5 pieces; the calcination conditions under the argon atmosphere are a heating rate of 1-5°C / min, a calcination temperature of 300-350°C, and a heat preservation time of 1-3h.

7. The method for preparing the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode according to claim 1, characterized in that: The electrode is prepared by the preparation method of the platinum quantum dot-cobalt phosphide / carbon cloth composite electrode according to any one of claims 1 to 6, wherein the precious metal Pt exists in the form of quantum dots, and the CoP nanowire array structure can provide support for the loading of the Pt quantum dots, thereby preventing the agglomeration of the Pt quantum dots, and generating a Pt-P bond between Pt and CoP.

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