CN110600779B

CN110600779B - Anti-carbon deposition solid oxide fuel cell and preparation method thereof

Info

Publication number: CN110600779B
Application number: CN201910809470.5A
Authority: CN
Inventors: 郭冠伦; 方乐; 陈心彤; 刘俊; 牛斌
Original assignee: Wuhan Hiconics Power Technology Co ltd; Wuhan University of Technology WUT
Current assignee: Wuhan Hiconics Power Technology Co ltd; Wuhan University of Technology WUT
Priority date: 2019-08-29
Filing date: 2019-08-29
Publication date: 2020-12-25
Anticipated expiration: 2039-08-29
Also published as: CN110600779A

Abstract

The invention discloses an anti-carbon deposition solid oxide fuel cell and a preparation method thereof, wherein the anti-carbon deposition solid oxide fuel cell comprises an anode, an electrolyte and a cathode, wherein the anode and the cathode are arranged on two opposite sides in the electrolyte; the anode is a fuel electrode, the anode is made of nickel base, the fuel gas used by the anode is a mixed gas of dimethyl ether and water, and the volume ratio of the dimethyl ether to the water is 1: 1-3; the electrolyte is made of yttrium-stabilized zirconia, the cathode is an air electrode, and the cathode is made of lanthanum strontium cobalt iron; the invention improves the dry dimethyl ether fuel gas into the dimethyl ether and water volume ratio of 1: 1-3, the carbon deposition degree of the anode of the fuel cell can be effectively reduced, and the service efficiency of the cell is further improved; and the output power of the prepared solid oxide fuel cell reaches 862-960 mW^‑2。

Description

Anti-carbon deposition solid oxide fuel cell and preparation method thereof

Technical Field

The invention relates to the technical field of solid oxide fuel cells, in particular to an anti-carbon deposition solid oxide fuel cell and a preparation method thereof.

Background

With the continuous rise of the keeping quantity of internal combustion engine automobiles, the petroleum resources are continuously reduced, the pollution of the environment caused by the inefficient combustion of fossil fuels is increasingly serious, and the search for alternative and clean fuels and the development of more efficient fuels are crucial to the development of sustainable energy. At present, oxygen-containing hydrocarbons such as ethers and alcohols are receiving more and more attention as alternative fuels. Among them, dimethyl ether (DME) is widely used because it is the simplest diethyl ether, and has physical properties similar to those of liquefied petroleum gas. DME, which is present as a gas under normal conditions and is easily liquefied at room temperature at a pressure of 0.6MPa, exhibits a greater volumetric and gravimetric energy density than methanol. In addition, dimethyl ether is free of sulfur, heavy metals and other impurities. The emissions of NOx, SOx, CO, formaldehyde, particulate matter, and non-methane hydrocarbons are expected to be reduced.

In recent years, dimethyl ether has been widely studied as a fuel for high-temperature Solid Oxide Fuel Cells (SOFC). The SOFC can directly convert chemical energy into electric energy in the working process, has the advantages of high energy conversion efficiency, low pollution, high fuel selectivity and the like, and can be used as a power source of automobiles. In the SOFC, YSZ (zirconia solid electrolyte) is mostly used as an electrolyte material, which has good oxygen ion conductivity, and can exhibit good stability in an oxidizing or reducing atmosphere, and at the same time, the production cost is relatively low, and the SOFC is easy to manufacture. In the use of fuel, DME can be used as alternative fuel of SOFC due to the advantages of high heat value, gas at normal temperature and normal pressure, easy transportation and the like. Meanwhile, when DME (dimethyl ether) is used as the fuel of the SOFC, the DME can be directly supplied to the anode for working without an external reforming device, and meanwhile, the fuel cell system can be simplified and the combustion efficiency of the system can be improved. The anode material is Ni/YSZ metal ceramic, but because of the strong catalytic activity of Ni base, when hydrocarbon is used as fuel, the serious carbon deposition phenomenon can be generated on the surface of the anode, and the working performance of the battery is reduced. Su et al (code formation and performance of an intermediate-temperature fuel cell operating on a dimethyl ether fuel, 2011.196 (4): p.1967-. The reversible reactions to form carbon deposits in SOFC devices, using DME fuel as an example, are as follows:

in summary, dimethyl ether can be supplied directly to the anode without an external reformer to operate when used as a fuel for a solid oxide fuel cell, and has high combustion efficiency. When some anode materials with strong catalytic performance are used, serious carbon deposition phenomenon can be generated on the surface of an anode, so that obvious cracks are generated in the operation process of the battery, and the working performance of the battery is reduced. Therefore, in order to better promote the industrialization of SOFC, research on the problem of carbon deposition is needed to find measures for reducing the formation of carbon deposition and to improve the service life of the battery.

How to develop a solid oxide fuel cell with high carbon deposition resistance becomes a technical problem to be solved urgently.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides an anti-carbon deposition solid oxide fuel cell and a preparation method thereof, wherein dry dimethyl ether fuel gas is improved into a fuel cell containing dimethyl ether and water in a volume ratio of 1: 1-3, the carbon deposition degree of the anode of the fuel cell can be effectively reduced, and the service efficiency of the cell is further improved; and the output power of the prepared solid oxide fuel cell reaches 862-960 mW^-2。

The invention is realized by the following steps:

the invention aims to provide an anti-carbon deposition solid oxide fuel cell, which comprises an anode, an electrolyte and a cathode, wherein the anode and the cathode are arranged on two opposite sides in the electrolyte;

the anode is a fuel electrode, the anode is made of nickel base, the fuel gas used by the anode is a mixed gas of dimethyl ether and water, and the volume ratio of the dimethyl ether to the water is 1: 1-3;

the material of the electrolyte is yttrium-stabilized zirconia,

the cathode is an air electrode, and the cathode is made of lanthanum strontium cobalt iron.

Preferably, the volume ratio of the dimethyl ether to the water is 1: 2.

the invention also aims to provide a preparation method of the anti-carbon deposition solid oxide fuel cell, which comprises the following steps:

step 1, adopting a nickel base as an anode material;

step 2, adopting lanthanum strontium cobalt iron as a cathode material;

3, soaking the obtained anode and cathode materials into the electrolyte for soaking;

and 4, introducing a mixture of the anode and the cathode in a volume ratio of 1: 1-3 of a mixed gas of dimethyl ether and water.

Compared with the prior art, the invention has the following advantages and effects:

the invention provides an anti-carbon deposition solid oxide fuel cell and a preparation method thereof, wherein dry dimethyl ether fuel gas is improved to a volume ratio of dimethyl ether to water of 1: 1-3, the effect of reducing the generation of carbon deposition is achieved, the content of the carbon deposition is only 7.6% -16.7%, and the generation of the carbon deposition is greatly reduced compared with the content of 31.8% of the carbon deposition in dry dimethyl ether fuel gas; and the output power of the prepared solid oxide fuel cell reaches 862-960 mW^-2。

Drawings

FIG. 1 is a diagram of a pure DME molecular model construction;

FIG. 2 is a diagram showing the bond breaking and carbon deposition process of DME molecules in chemisorption;

FIG. 3 is the number of carbon atoms deposited on the cell substrate in pure DME;

FIG. 4 is a graph showing the change in the molecular weight of DME at various ratios of water to ether;

FIG. 5 is a graph of the number of carbon atoms deposited on a cell substrate at different ratios of water to ether;

FIG. 6 is a graph of voltage and power density as a function of current density for different water to ether ratios.

Detailed Description

Example 1

1. An anti-carbon deposition solid oxide fuel cell comprises an anode, an electrolyte and a cathode, wherein the anode and the cathode are arranged on two opposite sides in the electrolyte;

the anode is a fuel electrode, the anode is made of nickel base, the fuel gas used by the anode is a mixed gas of dimethyl ether and water, and the volume ratio of the dimethyl ether to the water is 1: 1;

the material of the electrolyte is yttrium-stabilized zirconia,

2. The preparation method of the anti-carbon deposition solid oxide fuel cell comprises the following steps:

step 1, adopting a nickel base as an anode material;

step 2, adopting lanthanum strontium cobalt iron as a cathode material;

and 4, introducing a mixture of the anode and the cathode in a volume ratio of 1: 1 of dimethyl ether and water.

3. The reaction mechanism is as follows: the water-ether ratio is 1: 1, the total reaction formula is CH₃-O-CH₃＋H₂O→2CO＋4H₂

Wherein: ni + H₂O→OH^-＋H⁺

Ni-(CHOCH)-Ni＋OH^-→CO＋Ni-CH-Ni＋2H⁺

According to the reaction process, after water molecules are added, the CHOCH component of the carbon deposition precursor reacts with OH groups, and the other part of the carbon deposition precursor generates carbon deposition on the catalytic base, so that the generation of the carbon deposition is reduced.

Example 2

the anode is a fuel electrode, the anode is made of nickel base, the fuel gas used by the anode is a mixed gas of dimethyl ether and water, and the volume ratio of the dimethyl ether to the water is 1: 2;

the material of the electrolyte is yttrium-stabilized zirconia,

step 1, adopting a nickel base as an anode material;

step 2, adopting lanthanum strontium cobalt iron as a cathode material;

and 4, introducing a mixture of the anode and the cathode in a volume ratio of 1: 2, dimethyl ether and water.

3. The reaction mechanism is as follows: the water-ether ratio is 2: 1, the total reaction formula is: CH (CH)₃-O-CH₃＋2H₂O→CO₂＋CO＋5H₂

Wherein: ni +2H₂O→2OH^-＋2H⁺

Ni-(CHOCH)-Ni＋OH^-→Ni-CO＋Ni-CH-Ni＋2H⁺

Ni-CO＋OH^-→CO₂＋H⁺

Example 3

the anode is a fuel electrode, the anode is made of nickel base, the fuel gas used by the anode is a mixed gas of dimethyl ether and water, and the volume ratio of the dimethyl ether to the water is 1: 3;

the material of the electrolyte is yttrium-stabilized zirconia,

step 1, adopting a nickel base as an anode material;

step 2, adopting lanthanum strontium cobalt iron as a cathode material;

and 4, introducing a mixture of the anode and the cathode in a volume ratio of 1: 3, dimethyl ether and water.

3. The reaction mechanism is as follows: the water-ether ratio is 3: 1, the total reaction formula is: CH (CH)₃-O-CH₃＋3H₂O→2CO₂＋6H₂；

Wherein: ni +3H₂O→3OH^-＋3H⁺

Ni-(CHOCH)-Ni＋3OH^-→2CO₂＋5H⁺

Comparative example 1

1. The comparative example is a solid oxide fuel cell comprising an anode, an electrolyte, and a cathode, the anode and the cathode being disposed on opposite sides within the electrolyte;

the anode is a fuel electrode, the anode is made of nickel base, and the fuel gas used by the anode is dry dimethyl ether;

the material of the electrolyte is yttrium-stabilized zirconia,

2. The conventional direct dimethyl ether fuel cell electrode reaction is as follows:

anode: CH (CH)₃OCH₃+3H₂O→2CO₂+12 H⁺+ 12e^-

Cathode: 3O₂+12 H⁺+ 12e^-→6H₂O

A battery: CH (CH)₃OCH₃+3H₂O+3O₂→2CO₂+6H₂O

Dimethyl ether fuel and water molecules with different proportions are directly added into the battery reaction, and the influence on carbon deposition is obtained through a product result. The reaction mechanism for carbon deposition is as follows:

CH₃-O-CH₃ -Ni→Ni-(CHOCH)-Ni + 2H₂

Ni-(CHOCH)-Ni→Ni-CH-Ni

Ni-CH-Ni→Ni-C＋H⁺

Ni-CO→Ni-C＋CO₂

therefore, the fuel cell of the comparative example generates a severe carbon deposition phenomenon on the surface of the anode, resulting in significant cracks during the operation of the cell, and reducing the operating performance of the cell.

Comparative example 2

The volume ratio of dimethyl ether to water in this comparative example was 1: 4; the rest is the same as in example 1.

Comparative example 3

The volume ratio of dimethyl ether to water in this comparative example was 1: 5; the rest is the same as in example 1.

Experimental example 1

Firstly, constructing a molecular reaction model

1. First, a molecular reaction model was constructed in the Material Studio software, and the specific parameters are shown in fig. 1, and the mechanism of carbon deposition in comparative example 1 was studied from the molecular point of view. The analysis result shows that the carbon deposit formation process of DME molecules on the nickel-based anode of the SOFC is divided into three steps of carbon-containing component adsorption, carbon atom diffusion and carbon atom aggregation; the bond breaking and carbon deposition process of DME molecules in chemisorption is shown in FIG. 2. In the adsorption process, fuel molecules and carbon-containing functional groups formed by pyrolysis of the fuel molecules are adsorbed on the nickel-based surface, the adsorbed carbon-containing components are the source of finally formed carbon, and alkyl in the carbon-containing components is easier to adsorb on the nickel-based surface. As the reaction occurs, the number of carbon atoms deposited on the cell substrate increases (fig. 3), resulting in the formation of carbon deposits in the cell.

2. From the results of the anti-carbon solid oxide fuel cells of examples 1 to 3, it was observed that DME consumption was different at different ratios from the process of generating the corresponding product by bond cleavage and mutual bonding of the molecules in the chemical reaction (fig. 4), and carbon generation was reduced after adding water molecules by following the change of the number of carbon atoms on the reaction substrate (fig. 5).

Second, statistics of carbon deposition content

The reaction of dimethyl ether molecules on the anode side of the solid oxide fuel cell is simulated by reaction molecular dynamics, and water molecules and fuel molecules are respectively blended according to different proportions. The results obtained, in terms of the number of carbon atoms deposited at the anode relative to the total number of carbon atoms fed, are shown in table 1, as a result of the reduction of carbon atoms on the substrate and the statistics of the amount of carbon deposition occurring at the anode of the fuel cell.

Table 1 carbon deposit content

Composition of intake air	100% DME (comparative example 1)	DME +1H2O (example 1)	DME +2H2O (example 2)	DME +3H2O (example 3)	DME +4H2O (comparative example 2)	DME +5H2O (comparative example 3)
							Carbon deposition content (%)	31.8	16.7	11.4	7.6	1.5	1.5

It can be seen from table 1 that the addition of water in different proportions in examples 1-3, and comparative examples 2-3, is indeed effective in reducing the formation of carbon on the anode compared to pure DME fuel (comparative example 1). When the ratio is more than 3: at 1, the effect of inhibiting carbon deposition was no longer evident (Table 1, FIG. 5),

measuring the voltage and power density with the current density curve

The power density curve at 800 c is shown in fig. 6 and the highest output power is tabulated in table 2.

TABLE 2 maximum output Power

Group of	100% DME (comparative example 1)	DME +1H2O (example 1)	DME +2H2O (example 2)	DME +3H2O (example 3)
					Output power (mW.cm-2)	786	920	960	862

In a water-ether ratio of 1: 1 and 2: when 1 hour, the maximum power density of the battery reaches 920mW^-2And 960mW.cm^-2In a water-ether ratio of 3: at 1, the maximum power density of the battery is reduced, and is only 862mW^-2The power of comparative example 2 (water to ether ratio of 4: 1) and comparative example 3 (water to ether ratio of 5: 1) both showed a decrease.

Therefore, the higher the ratio of water to ether, the better the anti-carbon effect, but too high a ratio of water to ether also affects the output of the battery. This is because excess water vapor increases the oxygen partial pressure, which can lead to cell voltage drop and, in extreme cases, re-oxidation of the Ni-base in the SOFC.

Combining the above anti-carbon deposition performance and the power density of the battery, the ratio of water to ether in example 2 was 2: the performance of the battery is the best when 1 is used, and the best embodiment is realized.

The invention is not to be considered as limited to the particular embodiments shown, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The anti-carbon deposition solid oxide fuel cell is characterized by comprising an anode, an electrolyte and a cathode, wherein the anode and the cathode are arranged on two opposite sides in the electrolyte;

the material of the electrolyte is yttrium-stabilized zirconia,

2. The carbon deposition resistant solid oxide fuel cell of claim 1, wherein the volume ratio of dimethyl ether to water is 1: 2.