CN103904337B - The preparation method of paper-graphite-CoPd membrane electrode - Google Patents

Abstract

The invention provides a method for preparing a paper-graphite-CoPd film electrode. (1) Evenly coat the mixture of graphite and clay on ordinary paper; (2) Keep the graphite-coated paper at 1.0V for 20-30min to activate the coated graphite, and then electrodeposit Co120 at -0.8V ~150min to get the paper-graphite-Co thin film electrode; (3) the paper-graphite-Co thin film electrode at 0.8mmol? L ^-1 PbCl ₂ solution was left to stand for 1 to 3 minutes to obtain a paper-graphite-CoPd film electrode, that is, a graphite-coated paper-supported CoPd catalyst. The invention uses a pencil to coat paper, electro-deposits Co on the surface of conductive graphite-coated paper, and then replaces part of Co with Pd to prepare a CoPd catalyst loaded on graphite-coated paper and improve the electroreduction performance of hydrogen peroxide. It overcomes the disadvantages of high current collector price and hydrogen peroxide decomposition, and solves the problem of poor cathode activity of hydrogen peroxide-based fuel cells.

Description

Preparation method of paper-graphite-CoPd film electrode

technical field

The invention relates to a method for preparing a paper-graphite-CoPd thin film electrode, which is a method for using graphite-coated paper to load CoPd to catalyze the electroreduction performance of hydrogen peroxide.

Background technique

Traditional fuel cells mostly use oxygen in the air as the oxidant. However, in some special cases, such as in water and space, the source of oxygen is greatly limited (in seawater, the concentration of dissolved oxygen is low, which is difficult to achieve as an oxidant. Requirements for power supply; in space, oxygen is thin, and it is also difficult to use). Therefore, if oxygen is used as an oxidizing agent in these environments, it must be carried by itself. _In recent years, H2O2 has been extensively _studied as an oxidizing agent. As an oxidant for underwater power sources, H ₂ O ₂ has many outstanding advantages. (1) H ₂ O ₂ is a liquid at room temperature. Both are more convenient and have less potential safety hazards. At the same time, the products of H ₂ O ₂ decomposition are water and oxygen, which will not cause environmental pollution problems; (2) The direct reduction of H ₂ O ₂ is a 2-electron reaction process, compared with the 4-electron reaction process in oxygen reduction , the activation energy is much lower, and the exchange current density of H ₂ O ₂ direct reduction is 6 orders of magnitude larger than that of oxygen electroreduction. Therefore, using H ₂ O ₂ as an oxidant is easier to obtain better battery performance than oxygen; (3 ) The electroreduction of H2O2 is a solid-liquid _two -phase reaction, while the electroreduction of oxygen is a solid _- liquid-gas three-phase reaction, the two-phase reaction interface region is easier to establish and stabilize than the three-phase interface region, and no gas diffusion layer is required , therefore, the whole battery system will be more stable, simple, compact, convenient and easy to operate. _In addition, H2O2 is produced in large quantities in the hundreds of millions of _pounds per year, is cheap, and overcomes the disadvantages of using oxygen in the air to carbonate the alkaline electrolyte.

The catalytic performance of H ₂ O ₂ electroreduction is an important factor directly related to the performance of fuel cells. Therefore, preparing high-performance catalysts is the key to improving the performance of fuel cells using H ₂ O ₂ as oxidant. Generally, the electrode of a fuel cell is obtained by mixing catalyst powder with a polymer binder and conductive carbon to form a paste, and then coating it on a metal current collector and drying it. Due to the introduction of polymer binders in this traditional way of making electrodes, some catalysts cannot be well contacted with the electrolyte, resulting in disadvantages such as low catalyst utilization and low conductivity. In addition, conductive carbon powder and polymer binder are unstable during long-term testing or under high-current discharge, which will cause shedding, thereby affecting the performance of the electrode. The main problem of the direct electroreduction of H ₂ O ₂ is that the electroreduction activity of H ₂ O ₂ is not high, and the direct electroreduction reaction is shown in formula (1):

HO ₂ ^- +H ₂ O+2e→2OH _ads ^- +OH ^- (1)

可参阅FanYang,KuiCheng,TianhaoWu,YingZhang,JinlingYin,GuilingWang,DianxueCao.Au–PdnanoparticlessupportedoncarbonfiberclothastheelectrocatalystforH ₂ O ₂ electroreductioninacidmedium.JournalofPowerSources,2013,233:252-258，以及KuiCheng,FanYang,YangXu,LinCheng,YanyanBao,DianxueCao,GuilingWang.PddopedCo ₃ O ₄ nanowire array as the H ₂ O ₂ electroreduction catalyst. Journal of Power Sources, 2013, 240:442-447.

Contents of the invention

The purpose of the present invention is to propose a method for preparing a paper-graphite-CoPd film electrode capable of solving the problem of poor cathode activity of a hydrogen peroxide-based fuel cell.

The purpose of the present invention is achieved like this:

(1) Evenly coat the mixture of graphite and clay on ordinary paper;

(2) Keep the graphite-coated paper at a voltage of 1.0V for 20-30min to activate the coated graphite, and then electrodeposit Co120-150min at -0.8V to obtain a paper-graphite-Co thin film electrode;

(3) Put the paper-graphite-Co thin film electrode in 0.8mmolL _- ¹ PbCl2 solution for 1~3 minutes to obtain the paper-graphite-CoPd thin film electrode, that is, the graphite-coated paper supported CoPd catalyst.

The present invention may also include:

1. The electrodeposition solution for electrodepositing Co is an electrodeposition solution obtained by dissolving 5-5.5g of NH ₄ Cl and 1-1.5g of CoCl ₂ in 50mL of water.

2. The graphite and clay mixture is a pencil lead.

3. The plain paper is one of writing paper, wrapping paper, newsprint, printing paper, technical paper, processing base paper or processed paper.

The invention uses a pencil to coat paper, electro-deposits Co on the surface of conductive graphite-coated paper, and then replaces part of Co with Pd to prepare a CoPd catalyst loaded on graphite-coated paper and improve the electroreduction performance of hydrogen peroxide. It overcomes the disadvantages of high current collector price and hydrogen peroxide decomposition, and solves the problem of poor cathode activity of hydrogen peroxide-based fuel cells.

The essence of the present invention is to adopt the cell structure of hydrogen peroxide-based fuel cell and the like, and use graphite-coated paper to support CoPd as a catalyst to form the cathode of the fuel cell. Among them, CoPd includes Co, Pd and CoPd alloys in various proportions.

The invention has the advantage of using the graphite-coated paper to support the CoPd catalyst as the catalyst for the direct electroreduction of hydrogen peroxide, and solves the problems of small discharge current and easy hydrolysis of the hydrogen peroxide electroreduction. No binder and conductive agent are used in the electrode preparation process. More importantly, graphite and clay can form a paper-graphite-clay-CoPd cross-linked compound with Co and Pd under the action of an electric field. High catalytic activity. Pencil-coated paper-loaded CoPd catalysts are not only extremely rich in graphite, clay, and Co, but also low in price, which greatly reduces the cost of electrode preparation. Moreover, it has high catalytic activity, stable performance, easy preparation process, suitable for industrial production, and has industrial applications. prospects and market value.

Detailed ways

The following examples describe the present invention in more detail.

(1) Evenly coat the mixture of graphite and clay on ordinary paper. Graphite and clay mixtures can be directly selected from pencil lead; ordinary paper can be selected from writing paper, wrapping paper, newsprint, printing paper, technical paper, processing base paper or processed paper.

(2) Keep the graphite-coated paper at 1.0V for 20-30 minutes to activate the coated graphite. Then, Co1 is electrodeposited in the electrodeposition solution at -0.8V for 20 to 150 minutes to obtain a paper-graphite-Co film electrode. The electrodeposition solution for electrodepositing Co is an electrodeposition solution obtained by dissolving 5-5.5g of NH ₄ Cl and 1-1.5g of CoCl ₂ in 50mL of water.

(3) Put the paper-graphite-Co thin film electrode in 0.8mmolL _- ¹ PbCl2 solution for 1~3 minutes to obtain the paper-graphite-CoPd thin film electrode, that is, the graphite-coated paper supported CoPd catalyst.

In order to better illustrate the effect of the process of the present invention, it will be illustrated with specific examples below

1. With paper-graphite-CoPd film as working electrode, carbon rod as counter electrode, and Ag/AgCl as reference electrode, in a solution of 2mol/L _NaOH and _0.40mol /L H2O2, -0.4 Under the voltage of Vvs.Ag/AgCl, the chronocurrent density reaches 180mA/cm ² .

2. Using paper-graphite-CoPd film as the cathode of H ₂ O ₂ direct electroreduction, using 3mol/L KOH as catholyte; Nafin-115 proton exchange film as diaphragm; nano-Pt loaded on nickel foam as anode , with 3mol/L KOH as the anolyte solution and 1mol/L sodium borohydride as the fuel; when the concentration of H ₂ O ₂ is 0.6mol/L ^-1 and the concentration of KOH is 3mol/L ^-1 the maximum power density of the battery It is 356mW/cm ^-2 .

3. Use paper-graphite-CoPd film as the cathode of H ₂ O ₂ direct electroreduction, use 3mol/L KOH as catholyte; Nafin-115 proton exchange film as diaphragm; The KOH is the anolyte solution; when the H ₂ O ₂ concentration is 0.6mol/L ¹ and the KOH concentration is 3mol/L, the maximum power density of the battery is 523mW/cm ² .

Claims (3)

1. a preparation method of paper-graphite-CoPd film electrode, is characterized in that: (1) Evenly coat the mixture of graphite and clay on ordinary paper; (2) Keep the graphite-coated paper obtained in step (1) at a voltage of 1.0V for 20-30 minutes to activate the coated graphite, and then electrodeposit Co1 at -0.8V for 20-150 minutes to obtain paper-graphite- Co thin film electrode; (3) Put the paper-graphite-Co film electrode in 0.8mmol·L _- ¹ PbCl2 solution for 1-3 minutes to obtain the paper-graphite-CoPd film electrode, that is, graphite-coated paper-supported CoPd catalyst. 2. The preparation method of paper-graphite-CoPd film electrode according to claim 1, characterized in that: the electrodeposition solution for electrodepositing Co is _5-5.5gNH4Cl and _1-1.5gCoCl2 dissolved in 50mL The electrodeposition solution obtained in water. 3. The method for preparing the paper-graphite-CoPd film electrode according to claim 1 or 2, characterized in that: the mixture of graphite and clay is a pencil lead.