Carbon nanotube loaded platinum-based alloy oxygen reduction catalyst and preparation method thereof
By doping Co on carbon nanotubes and growing uniform PtCo alloy, the problem of low utilization rate and low stability of the cathode oxygen reduction reaction catalyst of fuel cell is solved, and a high-efficiency and low-cost catalyst is achieved, with commercial application potential .
Patent Information
- Application Number
- CN202411568466.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-05
- Publication Date
- 2025-02-14
AI Technical Summary
The existing fuel cell cathode oxygen reduction reaction catalysts have problems such as low platinum utilization, low stability and high cost, which limits the commercial application of fuel cells.
The electrocatalytic performance of the catalyst is improved by doping Co on the carbon nanotube and growing a uniform and stable PtCo alloy by gentle polyol reduction method.
A catalyst with high platinum utilization and low platinum load has high half-wave potential, strong stability and low cost, and has potential in industrial applications.
Smart Images
Figure CN119447340A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of electrocatalysis, and in particular relates to a carbon nanotube-loaded platinum-based alloy oxygen reduction catalyst and a preparation method thereof. Background Art
[0002] Energy is the cornerstone of the continuous development and progress of human civilization. However, with the rapid development of the world economy, the uncontrolled abuse of energy has led to increasingly serious environmental pollution and energy depletion risks. As the core technology of the hydrogen energy industry, fuel cells are energy storage and conversion devices that directly convert chemical energy in fuel into electrical energy. They do not go through the thermal engine process and are not restricted by the Carnot cycle. Therefore, they have high energy conversion efficiency and are pollution-free.
[0003] However, in practical applications, the performance and durability of fuel cells are constrained by the high overpotential and metal corrosion of the cathode oxygen reduction reaction, which seriously limits its large-scale commercial application. To address this problem, platinum metal has been developed as an electrocatalyst for the cathode oxygen reduction reaction, catalyzing and accelerating the charge transfer reaction at the interface between the electrode and the electrolyte. So far, commercial Pt / C catalysts have been widely used, which has greatly reduced the reaction overpotential and improved the kinetic performance of the oxygen reduction reaction. However, the platinum utilization rate of commercial Pt / C catalysts is low and the stability is not high. The cost of its cost material, platinum metal, is also high due to limited global reserves. It is necessary to further develop new platinum-based catalysts with high platinum utilization and low platinum loading, so as to reduce the cost of fuel cells on the one hand and improve battery performance and stability on the other.
[0004] Taking all the above into consideration, platinum-based catalysts greatly reduce the amount of precious metal platinum used and improve the utilization rate of platinum. At the same time, due to the interaction between the metals, the stability of the catalyst can be improved, and it has great potential in industrial application prospects. However, pure platinum-based alloys cannot provide high catalytic activity. If the carrier is designed as a three-dimensional nanostructure, the electrocatalytic performance of the material will be significantly improved. This is because the carrier can improve the activity by interacting with the catalyst, or provide more contact area for the catalyst. Summary of the invention
[0005] In view of the above problems, the present application provides a carbon nanotube-loaded platinum-based alloy oxygen reduction catalyst and a preparation method thereof, which has a simple preparation method, low catalyst cost, and good catalytic effect in oxygen reduction.
[0006] To achieve the above objectives, this application provides the following technical solutions:
[0007] In one aspect of the present application, a carbon nanotube-loaded platinum-based alloy oxygen reduction catalyst is provided, which exhibits good electrocatalytic ORR performance in the oxygen reduction process and has the characteristics of high half-wave potential and strong catalytic stability.
[0008] Another aspect of the present application provides a method for preparing a carbon nanotube-supported platinum-based alloy oxygen reduction catalyst, the steps of which are as follows:
[0009] 1) Dissolve the weighed cobalt salt, nitrogen source and carbon source in acetic acid solution, fully heat and stir, and dry after reaction to obtain precursor 1;
[0010] 2) placing the precursor 1 in a tube furnace and annealing at high temperature under flowing nitrogen to obtain the precursor 2;
[0011] 3) The precursor 2 obtained in step 2) is added to a polyol solution containing a platinum salt, and the pH thereof is adjusted to be alkaline. After condensation and reflux, the solution is washed and dried to obtain an oxygen reduction catalyst.
[0012] Optionally, the cobalt salt in step 1) is cobalt acetate tetrahydrate, and its concentration is 0.045 mmol / L; the nitrogen source and carbon source are urea and chitosan, respectively, and their concentrations are 1.065 mmol / L and 0.062 mmol / L, respectively; and the mass percentage of acetic acid is 2%.
[0013] Optionally, the heating and stirring temperature in step 1) is 50-80°C, the drying time is 1-16h, and the drying temperature is 50-80°C.
[0014] Optionally, in step 2), high temperature annealing under flowing nitrogen is specifically: heating to 600-900° C. at a heating rate of 1-5° C. / min under a flowing N 2 atmosphere, and annealing at this temperature for 1-3 h.
[0015] Optionally, the platinum salt in step 3) is chloroplatinic acid hexahydrate, and its concentration is 20 mg / mL; and the polyol is ethylene glycol.
[0016] Optionally, the pH adjustment in step 3) is specifically as follows: using NaOH solution to adjust the pH value of the solution, the concentration of the NaOH solution is 0.1-2 mol / L, and the pH value of the alkaline reducing solution is 10-13.
[0017] Optionally, the condensation reflux time in step 3) is 1-12 hours, and the temperature is 80-120°C.
[0018] Optionally, the washing solution in step 3) is deionized water, the drying time is 1-12 hours, and the drying temperature is 60-100°C.
[0019] In another aspect of the present application, there is provided an application of a carbon nanotube-loaded platinum-based alloy oxygen reduction catalyst as described in any of the above items and a carbon nanotube-loaded platinum-based alloy oxygen reduction catalyst prepared by the preparation method thereof, wherein the carbon nanotube-loaded platinum-based alloy oxygen reduction catalyst is used for oxygen reduction reaction in an acidic environment.
[0020] The advantages of this application are:
[0021] 1. This catalyst is a PtCo alloy loaded with in-situ Co-doped carbon nanotubes, which can effectively reduce oxygen. It uses Co-doped carbon nanotubes as precursors, grows uniform and stable PtCo alloys through a mild polyol reduction method and the anchoring effect of Co on the precursor on Pt, and has excellent electrocatalyst performance.
[0022] 2. The preparation process of this application is simple to operate, the raw material cost is low, the catalyst performance is good, and it has the potential for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is the LSV curve diagram of ORR test of Example 1 and Comparative Examples 1-3 of the present invention;
[0024] Figure 2 RRDE test diagrams of Example 1 and Comparative Examples 1 and 3 of the present invention;
[0025] Figure 3 The ORR stability diagrams of Example 1 and Comparative Example 3 of the present invention are shown;
[0026] Figure 4 The bar graphs are MA and SA values of Example 1, Comparative Examples 1 and 3 of the present invention;
[0027] Figure 5 This is the SEM image of the catalyst prepared in Example 1;
[0028] Figure 6 TEM image of the catalyst prepared in Example 1;
[0029] Figure 7 The XRD diagrams of the catalysts prepared in Example 1 and Comparative Examples 1-2 are shown. DETAILED DESCRIPTION
[0030] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments described below can be arbitrarily combined to form a new embodiment.
[0031] Embodiment 1:
[0032] A method for preparing a carbon nanotube-supported platinum-based alloy oxygen reduction catalyst comprises the following steps:
[0033] 1) Weighed urea, chitosan and cobalt acetate tetrahydrate were added into a 2% by mass acetic acid solution, completely dissolved by ultrasonication, and then heated and stirred in an oil bath at 70° C. for 16 h.
[0034] 2) The precursor treated in step 1) was transferred to a crucible with a lid and placed in a tube furnace. It was heated to 800°C at a heating rate of 5°C / min in a flowing N2 atmosphere and annealed at this temperature for 2h. The black product obtained was CoNC. It was simply pickled with 1 mol / L sulfuric acid solution to remove unstable cobalt metal, then rinsed repeatedly with deionized water and dried in a vacuum oven at 60°C for 10h.
[0035] 3) The CoNC obtained in step 2) was placed in an appropriate amount of ethylene glycol solution, 1 mol / L NaOH solution was added dropwise to adjust the pH value of the reducing solution to 11, hexahydrate chloroplatinic acid solution was added dropwise, and then condensed and refluxed at 120° C. for 10 h to reduce Pt to CoNC to obtain a PtCo alloy.
[0036] 4) The material obtained in step 3) is cooled and centrifuged to separate the solid and the liquid. The obtained material is repeatedly rinsed with deionized water and placed in a vacuum oven for drying at 60° C. for 6 h to obtain a PtCoNC oxygen reduction catalyst.
[0037] Figure 5 This is the SEM image of the catalyst prepared in Example 1. Figure 6 This is the TEM image of the catalyst prepared in Example 1.
[0038] Comparative Example 1:
[0039] The difference between Comparative Example 1 and Example 1 is that the cobalt salt in step 1) is removed, and the other steps are the same as those in Example 1, thereby obtaining a PtNC material.
[0040] Comparative Example 2:
[0041] The difference between Comparative Example 2 and Example 1 is that steps 3) and 4) are omitted, and the rest is the same as Example 1 to obtain CoNC material.
[0042] Comparative Example 3:
[0043] The difference between Comparative Example 3 and Example 1 is that it is commercial Pt / C.
[0044] Experimental Example 1:
[0045] The products obtained in Example 1 and Comparative Examples 1 to 3 were used as catalysts for ORR test in a solution containing 0.1 mol / L HClO4 as electrolyte. All electrochemical measurements were performed on an electrochemical workstation (CHI760E) using a rotating ring disk electrode (RRDE) system with a glassy carbon electrode as the working electrode (area: 0.1256 cm 2 ), the graphite rod is the counter electrode, and the reference electrode is a saturated Hg / Hg2SO4 electrode. 2 mg of the prepared catalyst was added to 470 μL of isopropyl alcohol, 20 μL of ultrapure water and 10 μL of Nafion (5 wt%), and a uniformly dispersed catalyst ink was prepared after ultrasonic treatment. Then 10 μL of the ink was applied to a glassy carbon rotating electrode polished with alumina and dried at room temperature to obtain a working electrode film coated with the catalyst. Under O2 saturation and N2 saturation conditions, the potential range of 0.2 to 1.1 vs RHE was 5 mV s -1 The linear sweep voltammetry (LSV) polarization curve was recorded at a scan rate of 1600 rpm. The formula Evs.RHE = Evs.Hg / Hg2SO4 + 0.059 × pH + 0.652 (0.1M HClO4, pH = 1) was used to calculate the potential and the potential of the reversible hydrogen electrode (RHE). In the potential range of 0.02 to 1.2 vs RHE, 50 mV s -1 Cyclic voltammetry (CV) was performed at a scan rate of . After obtaining a stable CV curve, the electrochemical surface area (ECSA) was evaluated using the amount of electricity generated by H absorption / desorption (characteristic peak integrated area). The hydrogen adsorption constant was 210 μC cm -2 The stability of ORR was evaluated by measuring the chronoamperometric curve (it) in 0.10 mol / L HClO4 at room temperature and oxygen saturation, where the voltage was 0.7 V vs. RHE and the rotation rate was 1600 rpm.
[0046] The results are shown in the figure, where Figure 1 The ORR performance of Example 1 and Comparative Examples 1-3 shows that the half-wave potential of PtCoNC is the highest, which is 0.893 V. Compared with the comparative example, the limiting current density of PtCoNC is 5.44 mA cm -2 Meanwhile, PtCoNC exhibits a higher onset potential of 1.02V.
[0047] Figure 2 RRDE test diagrams of Example 1, Comparative Examples 1 and 3 show that, compared with PtNC and commercial Pt / C, PtCoNC is a four-electron oxygen reduction reaction pathway in 0.10 mol / L HClO4 solution. In addition, the H2O2 yield of PtCoNC is lower (<5%) at 0.2-0.8 V vs. RHE.
[0048] Figure 3 Chronoamperometric (it) measurements were performed at 1600 rpm in an O2-saturated 0.10 mol / L HClO4 solution to investigate the stability of the catalyst. After 10,000 s of durability testing, PtCoNC showed minimal attenuation (38% loss of current density), and PtCoNC had better stability than Pt / C.
[0049] Figure 4 The bar graphs show the mass activity (MA) and specific activity (SA) of PtCoNC, PtNC and Pt / C at 0.9 V vs. RHE. The MA of PtCoNC is 0.151 A mg Pt -1 , which are 2.3 and 3 times that of PtNC and Pt / C, respectively. Meanwhile, PtCoNC (0.81 mA cm -2 ) are 1.6 and 2.7 times of those of PtNC and Pt / C, respectively.
[0050] Figure 7 The XRD diagrams of the catalysts prepared in Example 1 and Comparative Examples 1-2 are shown.
[0051] In summary, the present application provides a highly active oxygen reduction catalyst having a nanotube morphology with a high specific area, which greatly reduces the oxygen mass transfer resistance, exposes more active sites, and improves the intrinsic activity of ORR. The strong metal-support interaction between the intermetallic compound PtCo and Co-NC sites improves the long-term stability of the catalyst.
[0052] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention are within the scope of protection required by the present invention.
Claims
1. A method for preparing a carbon nanotube-supported platinum-based alloy oxygen reduction catalyst, characterized in that: Here are the steps: 1) Dissolve the weighed cobalt salt, nitrogen source and carbon source in acetic acid solution, fully heat and stir, and dry after reaction to obtain precursor 1; 2) placing the precursor 1 in a tube furnace and annealing at high temperature under flowing nitrogen to obtain the precursor 2; 3) The precursor 2 obtained in step 2) is added to a polyol solution containing a platinum salt, and the pH thereof is adjusted to be alkaline. After condensation and reflux, the solution is washed and dried to obtain an oxygen reduction catalyst.
2. The preparation method according to claim 1, characterized in that: The cobalt salt in step 1) is cobalt acetate tetrahydrate, and its concentration is 0.045 mmol / L; the nitrogen source and carbon source are urea and chitosan, and their concentrations are 1.065 mmol / L and 0.062 mmol / L respectively; the mass percentage of acetic acid is 2%.
3. The preparation method according to claim 1, characterized in that: The heating and stirring temperature of step 1) is 50-80°C, the drying time is 1-16h, and the drying temperature is 50-80°C.
4. The preparation method according to claim 1, characterized in that: In step 2), high temperature annealing under flowing nitrogen is specifically: heating to 600-900° C. at a heating rate of 1-5° C. / min under flowing N 2 atmosphere, and annealing at this temperature for 1-3 hours.
5. The preparation method according to claim 1, characterized in that: The platinum salt in step 3) is chloroplatinic acid hexahydrate, and its concentration is 20 mg / mL; the polyol is ethylene glycol.
6. The preparation method according to claim 1, characterized in that: The pH value of the solution is adjusted by using a NaOH solution with a concentration of 0.1-2 mol / L, and the pH value of the alkaline reducing solution is 10-13.
7. The preparation method according to claim 1, characterized in that: The condensation reflux time in step 3) is 1-12 hours, and the temperature is 80-120°C.
8. The preparation method according to claim 1, characterized in that: The washing solution in step 3) is deionized water, the drying time is 1-12 hours, and the drying temperature is 60-100°C. 9 . The carbon nanotube-supported platinum-based alloy oxygen reduction catalyst prepared by the method for preparing the carbon nanotube-supported platinum-based alloy oxygen reduction catalyst according to any one of claims 1 to 8 .
10. Use of a carbon nanotube-supported platinum-based alloy oxygen reduction catalyst prepared by the method for preparing a carbon nanotube-supported platinum-based alloy oxygen reduction catalyst according to any one of claims 1 to 8, characterized in that: The carbon nanotube-supported platinum-based alloy oxygen reduction catalyst is used for oxygen reduction reaction in an acidic environment.