A method for passivating a porous carbon support

Abstract

The present application belongs to the technical field of catalyst porous carbon carrier, and particularly relates to a passivation method of porous carbon carrier. In the passivation process of the porous carbon carrier, phosphorus, boron and nitrogen elements are added, and the content of the boron element is 0-10% of the total weight, the content of the phosphorus element is 0-10% of the total weight, and the content of the nitrogen element is 0-5% of the total weight. The added boron, phosphorus, nitrogen and other heteroatoms can obviously improve the service life of the catalyst carbon carrier, improve the high-temperature corrosion resistance of the carbon carrier, reduce the reaction activity of the carbon carrier and oxygen free radicals, and passivate the active groups on the surface of the porous carbon carrier. After the passivation of the porous carbon carrier, the cycle life of the carbon carrier can be improved, and the life is increased by 50%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of porous carbon carrier of catalyst, and particularly relates to a passivation method of porous carbon carrier. BACKGROUND

[0002] The porous carbon carrier is a commonly used carrier material of hydrogen fuel cell catalyst, is in black powder form, has a developed mesopore structure and a high specific surface area. The developed pore structure and the high specific surface area provide binding sites for the support of the catalyst, thereby increasing the dispersibility of the catalyst and improving the mass activity of the catalyst.

[0003] However, due to the high specific surface area, the traditional porous carbon carrier has many active groups on the surface and has high activity. In the start-stop process of the hydrogen fuel cell, the porous carbon carrier is prone to oxidation reaction with oxygen, which causes serious corrosion of the carrier and affects the service life of the porous carbon carrier. SUMMARY

[0004] The present application proposes a passivation technology of porous carbon carrier to solve the problem of short service life of the existing carbon carrier. The porous carbon carrier is used as a base material. The surface of the porous carbon carrier is modified by a passivation agent under high-temperature hydrothermal conditions, and then the porous carbon carrier is subjected to heat treatment in a tube furnace to assist in doping of heteroatoms such as N, P and B. The introduction of these elements passivates the associated functional groups in the preparation process of the porous carbon material, which not only effectively reduces the activity of oxygen functional groups, but also inhibits the oxidation reaction of the porous carbon carrier, thereby improving the service life of the porous carbon carrier.

[0005] To achieve the above-mentioned purpose, the present application is implemented by the following technical solutions:

[0006] A preparation method of passivated porous carbon carrier, comprising the following steps:

[0007] (1) mixing the porous carbon carrier with a passivation agent and then performing a hydrothermal reaction to obtain a passivated intermediate product A by filtration;

[0008] (2) drying the passivated intermediate product A, and uniformly heating it to a specific temperature in an inert or reducing atmosphere;

[0009] (3) keeping the temperature constant, regulating the surface functional groups and carbon layer structure of the carbon carrier, and passivating the surface of the porous carbon carrier.

[0010] Further, the passivation agent in step (1) is one or more of H3PO4, (NH4)2HPO4, (NH4)H2PO4, H3BO3 and B2O3.

[0011] Further, the mixing ratio of the porous carbon carrier to the passivation agent in step (1) ranges from 1:0.1 to 1:2.

[0012] Further, in step (1), the ratio of the total mass of the porous carbon carrier and the passivation agent to the mass of water is 1:1-1:10.

[0013] Further, in step (1), the hydrothermal reaction temperature is 120-240°C, and the reaction time is 4-12h.

[0014] Further, in step (2), the drying of the passivation intermediate A refers to drying the passivation intermediate A in a 120°C air oven until the weight is constant.

[0015] Further, in step (2), the inert or reducing atmosphere is one of an argon atmosphere, a 10% hydrogen atmosphere, and a 20% hydrogen atmosphere.

[0016] Further, in step (2), the uniform temperature rise to a specific temperature refers to a temperature rise of the tube furnace at a rate of 2°C / min to 800-1200°C.

[0017] Further, in step (3), the constant temperature holding time is 2-12h.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] 1. The present application can passivate the porous carbon carrier, improve the service life of the carbon carrier of the catalyst, and increase the cycle life of the carbon carrier by 50%, and the mass activity retention rate is 80% to 4500 cycles.

[0020] 2. The present application introduces N, P, B and other heteroatoms, which can effectively reduce the activity of oxygen functional groups, passivate the active groups on the surface of the porous carbon carrier, and reduce the reaction activity of the carbon carrier with oxygen free radicals.

[0021] 3. The present application can improve the high-temperature corrosion resistance of the carbon carrier.

[0022] 4. The present application can promote the stabilization and transformation of surface functional groups through high-temperature passivation, which further improves the cycle stability of the porous carbon carrier. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 CV curve diagram of the present application before and after 70°C high-temperature 1000 cycles. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present application, the present application will be described more fully below. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0025] Example 1

[0026] (1) The porous carbon carrier is mixed with the passivation agent H3PO4, and the mixing ratio of the porous carbon carrier to the passivation agent is 1:0.1;

[0027] (2) After mixing, it is placed in a hydrothermal kettle, and water is added. Based on the total mass of the porous carbon carrier and the passivation agent, the mass ratio of the total mass of the porous carbon carrier and the passivation agent to the mass of water is 1:10;

[0028] (3) The porous carbon carrier and the passivation agent are subjected to hydrothermal reaction in the hydrothermal reaction kettle, the hydrothermal reaction temperature is 240°C, the reaction time is 4h, and the passivation intermediate A is obtained by filtration;

[0029] (4) The passivation intermediate A is dried in a blast drying oven at 120°C to constant weight;

[0030] (5) After drying, it is placed in a tube furnace, heated to 800°C at a heating rate of 2°C / min under an argon atmosphere, and kept at a constant temperature for 12h.

[0031] Example 2

[0032] (1) The porous carbon carrier is mixed with the passivation agent (NH4)2HPO4, H3BO3, and the mixing ratio of the porous carbon carrier to the passivation agent is 1:2, wherein (NH4)2HPO4:H3BO3 is 1:1;

[0033] (2) After mixing, it is placed in a hydrothermal kettle, and water is added. Based on the total mass of the porous carbon carrier and the passivation agent, the mass ratio of the total mass of the porous carbon carrier and the passivation agent to the mass of water is 1:1;

[0034] (3) The porous carbon carrier and the passivation agent are subjected to hydrothermal reaction in the hydrothermal reaction kettle, the hydrothermal reaction temperature is 120°C, the reaction time is 12h, and the passivation intermediate A is obtained by filtration;

[0035] (4) The passivation intermediate A is dried in a blast drying oven at 120°C to constant weight;

[0036] (5) After drying, it is placed in a tube furnace, heated to 1200°C at a heating rate of 2°C / min under a 10% hydrogen atmosphere, and kept at a constant temperature for 2h.

[0037] Example 3

[0038] (1) The porous carbon carrier is mixed with the passivation agent (NH4)2HPO4, B2O3, and the mixing ratio of the porous carbon carrier to the passivation agent is 1:1, wherein (NH4)2HPO4:B2O3 is 1:1;

[0039] (2) After mixing, it is placed in a hydrothermal kettle, and water is added. Based on the total mass of the porous carbon carrier and the passivation agent, the mass ratio of the total mass of the porous carbon carrier and the passivation agent to the mass of water is 1:5;

[0040] (3) The porous carbon carrier and the passivation agent are subjected to a hydrothermal reaction in a hydrothermal reaction kettle, the hydrothermal reaction temperature is 180°C, the reaction time is 6h, and a passivation intermediate product A is obtained by filtration;

[0041] (4) The passivation intermediate product A is dried in a blast drying oven at 120°C until the weight is constant;

[0042] (5) After drying, the passivation intermediate product A is placed in a tube furnace, heated to 1000°C at a heating rate of 2°C / min under a 20% hydrogen atmosphere, and kept at 1000°C for 6h.

[0043] Example 4

[0044] (1) The porous carbon carrier and the passivation agent H3BO3 are mixed, and the mixing ratio of the porous carbon carrier to the passivation agent is 1:2;

[0045] (2) After mixing, the mixture is placed in a hydrothermal kettle, and water is added, and the mass ratio of the total mass of the porous carbon carrier and the passivation agent to the mass of water is 1:8 based on the total mass of the porous carbon carrier and the passivation agent;

[0046] (3) The porous carbon carrier and the passivation agent are subjected to a hydrothermal reaction in a hydrothermal reaction kettle, the hydrothermal reaction temperature is 200°C, the reaction time is 8h, and a passivation intermediate product A is obtained by filtration;

[0047] (4) The passivation intermediate product A is dried in a blast drying oven at 120°C until the weight is constant;

[0048] (5) After drying, the passivation intermediate product A is placed in a tube furnace, heated to 800°C at a heating rate of 2°C / min under a 10% hydrogen atmosphere, and kept at 800°C for 12h.

[0049] After the carrier is prepared, the general method is used for 40% Pt loading for cycle life test, and the experimental results are shown in Table 1. After the carrier is subjected to the cycle test, the mass activity retention rate of the commercial carbon carrier supported platinum catalyst is more than 80% for 3000 cycles, the mass activity retention rate of Example 1 is more than 80% for 4000 cycles; the mass activity retention rate of Example 2 is more than 80% for 4200 cycles; the mass activity retention rate of Example 3 is more than 80% for 4500 cycles; and the mass activity retention rate of Example 4 is more than 80% for 3800 cycles. Among them, the service life of Example 4 is improved by 50% compared with the commercial carbon carrier.

[0050] In terms of high-temperature corrosion resistance, the experimental results are shown in Table 2. After 70°C high-temperature 1000 cycle, the specific surface area of the commercial carbon carrier supported platinum catalyst is attenuated from 64.42m 2 / gpt to 13.91m 2 / gpt, and the cycle loss is 78.41%; while the specific surface area of Example 4 is attenuated from 56.73m 2 / gpt to 44.28 m 2 / gpt, cycle loss 21.95, showing better cycle stability.

[0051] Table 1 each embodiment of the content of heteroatoms and its cycle life

[0052]

[0053] Table 2 Example 4 and commercial carbon support high temperature corrosion resistance comparison

[0054]

[0055] The above-described embodiments only express specific implementation cases of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the scope of protection of the present application patent should be subject to the appended claims.

Claims

1. A method for preparing a passivated porous carbon support, characterized by, The method comprises the following steps: (1) mixing the porous carbon carrier with a passivation agent and then performing a hydrothermal reaction, and filtering to obtain a passivation intermediate A; (2) drying the passivation intermediate A, and uniformly increasing the temperature to a specific temperature in an inert or reducing atmosphere; (3) keeping the temperature constant, regulating the surface functional groups and carbon layer structure of the carbon carrier, and passivating the surface of the porous carbon carrier; In step (1), the passivation agent is one or more of (NH4)2HPO4, (NH4)H2PO4, H3BO3 and B2O3; the hydrothermal reaction temperature is 120-240 DEG C, and the reaction time is 4-12 h; In step (1), the mixing ratio of the porous carbon carrier and the passivation agent ranges from 1:0.1 to 1:2; In step (1), based on the total mass of the porous carbon carrier and the passivation agent, the mass ratio of the total mass of the porous carbon carrier and the passivation agent to water ranges from 1:1 to 1:10; In step (2), the uniform temperature increase to a specific temperature refers to increasing the temperature to 800-1200 DEG C at a rate of 2 DEG C / min in a tube furnace.

2. The method of claim 1, wherein the method is characterized by, In step (2), the drying of the passivation intermediate A refers to drying the passivation intermediate A in a 120 DEG C air oven until the weight is constant.

3. The method of claim 1, wherein the method is characterized by, In step (2), the inert or reducing atmosphere is one of an argon atmosphere, a 10% hydrogen atmosphere and a 20% hydrogen atmosphere.

4. The method of claim 1, wherein the method is characterized by, In step (3), the temperature keeping time is 2-12 h.

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