Preparation method and application of copper-doped carbon nitride loaded PtCu alloy catalyst

Abstract

The invention discloses a preparation method and application of a copper-doped carbon nitride loaded PtCu alloy catalyst, and belongs to the field of electrocatalysis, the preparation method comprises the following steps: dissolving melamine and copper nitrate in ethanol, and drying to obtain a product; the product is subjected to pyrolysis in the N2 atmosphere, and Cu-doped carbon nitride (Cu / g-C3N4) is prepared; then uniformly grinding Cu / g-C3N4 and citric acid, and performing pyrolysis in an N2 atmosphere to prepare Cu / NC; pt4 + is added into Cu / NC, excessive sodium borohydride solution is dropwise added, and the PtCu / NC electrocatalyst is prepared. The nanosheet PtCu / NC electrocatalyst is prepared through pyrolysis and simple reduction, the preparation process of the catalyst is simple, the cost is low, and an electrochemical test shows that the obtained catalyst is good in oxygen reduction performance.

Description

Technical Field

[0001] The present application relates to a preparation method and application of a copper-doped carbon nitride-supported PtCu alloy catalyst, belonging to the field of electrocatalysis. Background Art

[0002] Since the beginning of this century, the energy crisis has been intensifying. The depletion and harm of traditional fossil fuels urgently require the search for a renewable and sustainable fuel. Hydrogen energy is a clean, cheap, high calorific value, and sustainable fuel, and is considered to be an ideal future energy source. Proton exchange membrane fuel cells use hydrogen energy as fuel and are devices that convert chemical energy into electrical energy. They have been widely studied in recent years. The oxygen reduction reaction (ORR), as the cathode reaction of fuel cells, is the reaction that has the greatest impact on the power of fuel cells. Commercial platinum carbon is currently a commonly used cathode catalyst, but its high cost, low activity, and low durability seriously restrict the large-scale commercial use of this fuel cell. For the above reasons, it is particularly important to develop a low-cost, high-durability oxygen reduction catalyst.

[0003] Currently, the commonly used method to reduce costs is to reduce the platinum loading in the catalyst. However, how to reduce the platinum loading and improve its oxygen reduction performance is the most urgent problem to be solved. Summary of the invention

[0004] In order to solve the above problems, the present application proposes a preparation method and application of a copper-doped carbon nitride-loaded PtCu alloy catalyst. A nanosheet PtCu / NC electrocatalyst is prepared by pyrolysis and simple reduction, which makes the catalyst preparation process simple and low-cost. Electrochemical tests show that the obtained catalyst has good oxygen reduction performance.

[0005] According to one aspect of the present application, a method for preparing a copper-doped carbon nitride-supported PtCu alloy catalyst is provided, comprising the following steps:

[0006] (1) Melamine and copper nitrate are dissolved in ethanol respectively, the two solutions are slowly mixed and reacted, and then evaporated to dryness, and the dried product is placed in a tube furnace for pyrolysis under a N2 atmosphere to obtain Cu-doped carbon nitride;

[0007] (2) Grinding Cu-doped carbon nitride and citric acid uniformly, placing them in a tube furnace for pyrolysis under N2 atmosphere to obtain Cu / NC;

[0008] (3) Weigh a certain amount of Cu / NC and disperse it in sodium hydroxide solution. Add Pt 4+ solution, adding an excess amount of sodium borohydride solution dropwise, stirring, centrifuging and washing, and vacuum drying to obtain the PtCu / NC electrocatalyst.

[0009] Optionally, in step (1), the amount of melamine is 6-10 g, the amount of copper nitrate is 0.2-0.8 g, the amount of ethanol is 5-100 ml, the reaction time is 2-6 h, and the pyrolysis temperature is 450-550° C.

[0010] Optionally, in step (2), the amount of copper-doped carbon nitride is 1 to 3 g, the amount of citric acid is 1 to 3 g, the reaction time is 2 to 6 h, and the pyrolysis temperature is 650 to 850° C.

[0011] Optionally, in step (3), Pt 4+ Sodium chloroplatinate is ultrasonically dissolved in 5-10 ml of sodium hydroxide solution, the pH value of the sodium hydroxide solution is 9-12, and the mass ratio of the metal salt substance to water is (1.212-1.302):(10-30).

[0012] Optionally, in step (3), the amount of Cu / NC is 5-15 mg, the amount of sodium hydroxide solution is 5-10 ml; Pt 4+ The amount of the solution is 100-200 μl; the concentration of sodium borohydride is 4-10 mg / ml, the amount added is 20-50 mg, and the reaction time is 30-60 min.

[0013] Optionally, in step (3), the vacuum drying temperature is 40-60° C. and the drying time is 8-14 h.

[0014] According to another aspect of the present application, an application of a copper-doped carbon nitride-supported PtCu alloy catalyst is provided, and the catalyst is applied to an oxygen reduction reaction.

[0015] The beneficial effects of this application include but are not limited to:

[0016] 1. The preparation method of the copper-doped carbon nitride-supported PtCu alloy catalyst provided in the present application can not only produce a lattice strain effect and shorten the Pt-Pt bond by adding a transition metal, but also make the d-band center closer to the Fermi level, which helps to improve the oxygen reduction performance of the catalyst. Using Cu atoms as transition metals, the reserves are abundant and the PuCu alloy catalyst has excellent oxygen reduction activity. Alloying transition metals with platinum can improve the utilization rate of platinum, effectively reduce the platinum loading, and reduce the cost of the catalyst.

[0017] 2. The preparation method of the copper-doped carbon nitride-loaded PtCu alloy catalyst provided in the present application adopts a carbon nitride material with a high specific surface area as a carrier for metal loading, which is conducive to more fully exposing the active sites of the metal and significantly improving the catalytic performance; secondary pyrolysis can further increase the specific surface area of ​​the material.

[0018] 3. The preparation method of the copper-doped carbon nitride-supported PtCu alloy catalyst provided in the present application has a simple and controllable preparation process, low raw material cost, good catalyst performance, and has the potential for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0020] Figure 1 The electrochemical performance test results of the products obtained from Example 1 of the present application and commercial Pt / C are shown in FIG. Figure 1 a is the LSV curve of ORR test, Figure 1 b is the CV graph of ORR test, Figure 1 c and 1d are the MA and SA diagrams of OER test;

[0021] Figure 2 This is a TEM image of the catalyst prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0022] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0023] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions. In addition, any method and material similar or equivalent to the described content can be applied to the method of the present invention. The preferred implementation methods and materials described in this patent are for demonstration purposes only.

[0024] Example 1

[0025] The preparation method of copper-doped carbon nitride-supported PtCu alloy catalyst comprises the following steps:

[0026] (1) 8 g of melamine and 0.488 g of copper nitrate were dissolved in 80 and 5 ml of ethanol, respectively. The two solutions were slowly mixed and stirred at 70 °C for 1 h, and then dried at 100 °C. The dried product was placed in a porcelain boat and calcined in a tube furnace under a nitrogen atmosphere at a temperature of 5 °C min -1 The rate was increased to 550 °C and maintained for 3 h, and then naturally cooled to room temperature.

[0027] (2) 3 g of Cu-doped carbon nitride and 3 g of citric acid were ground evenly, and the ground product was placed in a porcelain boat and calcined in a tube furnace under a nitrogen atmosphere. The temperature was set at 5 °C min -1 The rate was increased to 800 °C and maintained for 2 h, and then naturally cooled to room temperature.

[0028] (3) Disperse 10 mg Cu / NC in 5 mL sodium hydroxide solution (PH = 12), add 160 μL sodium chloroplatinate aqueous solution and then add excess sodium borohydride under stirring, stir for 1 h, collect the product by centrifugation, wash three times with ultrapure water, and vacuum dry at 40 ° C for 12 h.

[0029] Experimental example

[0030] The product obtained in Example 1 was used as a catalyst to carry out oxygen reduction tests in a solution with an electrolyte of 0.1M HClO4. The electrochemical measurement was carried out on an electrochemical workstation (CHI760E) using a standard three-electrode system. In the electrochemical test, a glassy carbon electrode with a diameter of 4 mm was used as the counter electrode, a graphite rod was used as the counter electrode, and a Hg / Hg2SO4 electrode was used as the reference electrode. The glassy carbon electrode was polished with alumina. In order to prepare a uniformly dispersed catalyst ink, 1 mg of Pt / C or 2 mg of the prepared catalyst was dispersed in 20 μL ultrapure water, 470 μL isopropanol and 10 μL Nafion (5 wt.%), and low-temperature ultrasound was applied for 30 minutes to obtain a uniformly dispersed catalyst ink. 5 μL of Pt / C ink or 8 μL of the prepared catalyst ink was dropped on the glassy carbon electrode and then dried under rotation. In 0.1M HClO4 under O2 saturation and N2 saturation conditions, at 50 mV s -1 The cyclic voltammetry (CV) curve of the catalyst was tested at a scan rate of 1600 rpm and 5 mV s. The oxygen reduction performance was tested in oxygen-saturated 0.1 M HClO4 and the background current value under nitrogen was deducted. -1 , the scanning interval was from 0.03 to 1.1 V vs. RHE, and the ring voltage was set to 1.3 V vs RHE. The formula E(vs RHE) = E(vs Hg / Hg2SO4) + 0.652 + 0.059 × pH (0.1 M HClO4, pH = 1) was used to calculate the potential and the potential of the reversible hydrogen electrode (RHE). The accelerated durability test (ADT) was tested in oxygen-saturated 0.1 M HClO4, where the scanning interval was 0.6-1.0 V vs. RHE and the cycle was 3000 cycles.

[0031] Results Figure 1 .

[0032] Figure 1-a is the ORR performance of Example 1 and commercial Pt / C. It can be seen that PtCu / NC has the highest half-wave potential and the best ORR performance.

[0033] Figure 1 -b shows the CV tested under N2 saturation. The mass activity (MA) and specific activity (SA) of the electrocatalyst at 0.9 V vs. RHE were calculated. Figure 1 -c and d, the mass activity of PtCu / NC is the highest, which is 2.39 times that of commercial Pt / C, and its specific activity is also better than that of commercial Pt / C.

[0034] Figure 2 TEM image of the prepared catalyst. Figure 1 -a shows that the material is in the form of nanosheets. Figure 1 -b shows that platinum is evenly loaded on it.

[0035] From the above results, it can be seen that the copper-doped carbon nitride-supported PtCu alloy catalyst prepared by the method of pyrolysis and chemical reduction in this application showed a better half-wave potential in the ORR test under acidic conditions, and the mass activity and specific activity of the catalyst were much higher than those of commercial Pt / C. At the same time, the preparation process of this application is simple and efficient, which solves the shortcomings of complex catalyst preparation process and long cycle.

[0036] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for preparing a copper-doped carbon nitride-supported PtCu alloy catalyst, characterized in that: The following steps are involved: (1) Melamine and copper nitrate are dissolved in ethanol respectively, the two solutions are slowly mixed and then evaporated to dryness, and the dried product is placed in a tube furnace for pyrolysis under a N2 atmosphere to obtain Cu-doped carbon nitride; (2) Grinding Cu-doped carbon nitride and citric acid uniformly, placing them in a tube furnace, and pyrolyzing them under N2 atmosphere to obtain Cu / NC; (3) Weigh a certain amount of Cu / NC and disperse it in sodium hydroxide solution. Add Pt 4+ solution, adding an excess amount of sodium borohydride solution dropwise, stirring, centrifuging and washing, and vacuum drying to obtain the PtCu / NC electrocatalyst.

2. The method for preparing the copper-doped carbon nitride-supported PtCu alloy catalyst according to claim 1, characterized in that: In step (1), the amount of melamine is 6-10 g, the amount of copper nitrate is 0.2-0.8 g, the amount of ethanol is 5-100 ml, the reaction time is 2-6 h, and the pyrolysis temperature is 450-550° C.

3. The method for preparing the copper-doped carbon nitride-supported PtCu alloy catalyst according to claim 1, characterized in that: In step (2), the amount of copper-doped carbon nitride is 1 to 3 g, the amount of citric acid is 1 to 3 g, the reaction time is 2 to 6 hours, and the pyrolysis temperature is 650 to 850°C.

4. The method for preparing the copper-doped carbon nitride-supported PtCu alloy catalyst according to claim 1, characterized in that: In step (3), Pt 4+ The method comprises ultrasonically dissolving a sodium chloroplatinate metal salt in 5-10 ml of a sodium hydroxide solution, wherein the pH value of the sodium hydroxide solution is 9-12, and the mass ratio of the metal salt to water is (1.212-1.302):(10-30).

5. The method for preparing the copper-doped carbon nitride-supported PtCu alloy catalyst according to claim 1, characterized in that: In step (3), the amount of Cu / NC is 5-15 mg, the amount of sodium hydroxide solution is 5-10 ml; Pt 4+ The amount of the solution is 100-200 μl; the concentration of sodium borohydride is 4-10 mg / ml, the amount added is 20-50 mg, and the reaction time is 30-60 min.

6. The method for preparing the copper-doped carbon nitride-supported PtCu alloy catalyst according to claim 1, characterized in that: In step (3), the vacuum drying temperature is 40 to 60° C. and the drying time is 8 to 14 hours.

7. The method for preparing the copper-doped carbon nitride-supported PtCu alloy catalyst according to any one of claims 1 to 6, characterized in that: The catalyst is used for oxygen reduction reaction.

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