CN110021771B - Preparation method of Schottky junction fuel cell based on SnO2-SDC semiconductor-ion conductor - Google Patents

Abstract

The present invention belongs to a solid oxide fuel cellIn particular based on SnO₂The preparation method of the Schottky junction fuel cell of the-SDC semiconductor-ion conductor comprises the steps of SDC and SnO₂Grinding at different ratio, coating NCA L slurry on foamed nickel with thickness of 2mm, drying at 120 deg.C for 1 hr in drying oven to obtain Ni-NCA L electrode, and mixing Ni-NCA L layer and SDC-SnO₂The composite powder and the Ni-NCA L layer are sequentially put into a die, and a hydraulic press is used for applying 9MPa pressure to press the three-layer structure into a battery blank sheet, wherein the SDC and the SnO selected in the invention₂Two materials, low price, simple preparation method and the like. And mixing SDC ion conductor and SnO₂After the semiconductor is compounded, high ionic conductivity can be obtained at a lower temperature, which is the fundamental reason that the battery can obtain better battery performance output in a low-temperature region.

Description

Preparation of Schottky Junction Fuel Cell Based on SnO2-SDC Semiconductor-Ion Conductor method

technical field

The invention belongs to the field of solid oxide fuel cells, in particular to a preparation method of a Schottky junction fuel cell based on SnO ₂ -SDC semiconductor-ion conductor.

Background technique

Solid oxide fuel cell (Solid Oxide Fuel Cell, SOFC for short) belongs to the third-generation fuel cell, which is an all-solid-state fuel cell that directly converts chemical energy stored in fuel and oxidant into electrical energy efficiently and environmentally friendly at medium and high temperature. Chemical power plant. With high energy conversion efficiency (up to 50% to 80%), traditional fuel cells consist of three components: electrolyte, cathode, and anode, where the electrolyte is the core of the fuel cell, and its characteristics are important to determine the specific field of the fuel cell crucial, even determining the energy conversion efficiency at a specific temperature. From the research and development process of the electrolyte, since yttrium-stabilized zirconia (YSZ) was discovered and applied for the first time, due to its high ionic conductivity, good electrode matching, and good chemical stability in a hydrogen-oxygen atmosphere Therefore, it is regarded as the most successful electrolyte material and has been dominating the development of electrolyte materials. However, in order to use YSZ as the electrolyte, SOFC needs a working temperature as high as 1000 °C to obtain sufficiently high ionic conductivity, but the battery operating at high temperature will easily lead to high requirements for battery supporting materials and difficult battery sealing, which may easily lead to electrode sintering, Interfacial diffusion and thermal expansion mismatches between the electrolyte and electrodes reduce battery life. Currently, only very few electrolyte materials are capable of operating at low temperatures (<600 °C) with the desired electrical conductivity, so the development and development of new electrolyte materials is strongly demanded in order to operate SOFCs at low temperatures.

The development of electrolyte materials with high ionic conductivity at medium and low temperature (500-800 °C) and their application in the field of fuel cells is an effective way to realize SOFC low temperature operation. The composite two-phase or three-phase material can greatly improve the ionic conductivity of the material, and can effectively reduce the activation energy. Recent studies have shown that semiconductor-ion-conductor composite heterostructures have high ionic conductivity in the mid-low temperature region. J.Garcia-Barriocanal et al. reported that the heterostructure composed of YSZ/SrTiO ₃ multilayer films improved the ionic conductivity by 8 orders of magnitude relative to pure YSZ [JG Arriocanal, ARCalzada, M. Varela, Z. Sefrioui, E. Iborra, C. Leon, SJ Pennycook, S. Santamaria. Science, 2008, 321, 676-680.]. Lin et al. reported that the ionic conductivity of grain boundaries in bulk heterojunction composites composed of Ce _0.8 Gd _0.2 O _2-δ –CoFe ₂ O ₄ was significantly improved compared with single-phase materials [Y.Lin, SMFang, D.Su, KSBrinkman, FL Chen. Nature Communications. 6(2015) 6824.]. It can be seen that it is an indisputable fact that the semiconductor-ion conductor composite heterostructure has an enhanced effect on ion conduction. Although semiconductor-ion conductor heterojunction composites have a large improvement in ionic conductivity compared to pure ion conductors, few literatures report using this material as an electrolyte separator to assemble SOFCs, mainly because according to traditional electrochemical theory, only the intermediate The electrolyte layer has electronic conductivity, and the open-circuit voltage and power output of the battery will be greatly reduced. Therefore, if the semiconductor-ion conductor heterojunction composite material is to be applied to the fuel cell, the traditional cell structure must be improved accordingly. The Schottky fuel cell is a successful case of applying this composite material to a fuel cell. Zhu reported the use of ionic conductor material NSDC (samarium-doped ceria-sodium carbonate composite material) and semiconductor LCN (cobalt-lithium co-doped NiO) to form a Ni/LCN-NSDC/Ag single-component fuel cell, in which LCN was in a reducing atmosphere H Under the action of ₂ , it is reduced to metallic Ni, and forms a Schottky junction with LCN that is not reduced to form a Schottky fuel cell. The performance of the battery with this new structure is twice that of the traditional three-component fuel cell [B.Zhu,PDLund,R.Raza,Y.Ma,LDFan,M.Afzal,J. Patakangas,YJHe,YFZhao,WYTan,QAHuang, J. Zhang, H. Wang. Advanced Energy Materials 5 (2015) 1401895.].

SUMMARY OF THE INVENTION

The main purpose of the present invention is to develop a new SDC- _SnO2 semiconductor-ion conductor composite material with high ionic conductivity at medium and low temperature (500-800°C), and successfully use it as an ion transport layer to construct a Schottky Fuel cells are designed to achieve excellent performance output even at low temperatures.

The preparation steps of the SDC-SnO ₂ semiconductor-ion conductor composite material of the present invention are as follows:

The preparation method of the Schottky junction fuel cell based on SnO ₂ -SDC semiconductor-ion conductor includes the following steps:

1) Synthesize ion conductor material Sm-doped Ce _0.8 Sm _0.2 O _2-δ , namely SDC;

2) Fully grind the prepared SDC and SnO ₂ according to different proportions to obtain SDC/SnO ₂ composite materials with different SnO ₂ contents; the SnO ₂ mass content of the SDC/SnO ₂ composite material is 10%-60%.

3) According to the following weight ratio, add 2g of NCAL powder to 5mL of terpineol, grind for 10min to make the two fully and evenly mix, and prepare NCAL slurry; apply the NCAL slurry on the nickel foam with a thickness of 2mm, then Dry in a drying oven at 120 °C for 1 h to make Ni-NCAL electrodes;

4) Weigh 0.35g of SDC-SnO ₂ semiconductor-ion conductor composite material, put the Ni-NCAL layer, SDC-SnO ₂ composite powder, and Ni-NCAL layer into the mold in turn, apply a pressure of 9 MPa by a hydraulic press, and put the three The layered structure is pressed into a cell blank.

Wherein, synthesizing SDC includes the following steps:

a) According to the Ce ³⁺ :Sm ³⁺ molar ratio of 4:1 in the SDC molecular formula, weigh Ce(NO ₃ ) ₃ .6H ₂ O and Sm(NO ₃ ) ₃ .6H ₂ O in equal proportions, and Dissolve in an appropriate amount of deionized water and stir to make a 1mol/L metal ion mixed solution;

b) According to the ratio of bicarbonate ion: metal ion molar ratio of 3:1, weigh an appropriate amount of NH ₄ HCO ₃ powder, and then dissolve it into deionized water to make 1 mol/L NH ₄ HCO ₃ solution;

c) Slowly add the NH ₄ HCO ₃ solution into the metal ion mixed solution dropwise with a plastic-tip dropper. During this process, keep stirring to form a white precipitate. The precipitate is filtered and washed with deionized water for many times, and then the white precipitate is placed Dry in a drying oven at 120°C for 12h;

d) Finally, the dried product was put into a muffle furnace for sintering at 800° C. for 4 h to obtain SDC powder.

The preparation method of the Schottky junction fuel cell based on SnO ₂ -SDC semiconductor-ion conductor provided by the present invention has the following technical advantages:

(1) The two materials, SDC and SnO ₂ selected in the present invention, have the advantages of low price and simple preparation method. And after the composite of SDC ionic conductor and SnO ₂ semiconductor, high ionic conductivity can be obtained at lower temperature, which is the fundamental reason why this kind of battery can obtain better battery performance output in low temperature region.

(2) Schottky junction fuel cells are by far the simplest fuel cell technology with low-cost materials and simple fabrication processes, requiring only a composite material made of (P or N) semiconductor-ionic materials. Schottky junction fuel cells are also new advanced technologies where physical and electrochemical processes are combined in a synergistic manner to achieve superior device performance.

(3) Tested at 550°C and 500°C, the battery showed good power output. The battery has a high power output in the medium and low temperature region, and successfully lowered the operating temperature of the SOFC to below 600 degrees.

(4) Furthermore, although Schottky junctions are particularly suitable for the fuel cell case here, other potential energy applications may also be envisaged. The invention and the revealing of scientific principles provide a new path for fuel cells and innovative energy technologies, and accelerate the commercialization of fuel cells.

Description of drawings

Figure 1 shows the performance test results of fuel cells with different SDC contents at 550°C in the embodiment;

Figure 2 shows the performance test results of the battery prepared with the best ratio of SDC-SnO ₂ at 500 °C;

3 is a SEM cross-sectional view of the Schottky fuel cell obtained in the embodiment;

FIG. 4 is a rectification curve diagram obtained by applying a scan voltage across the Schottky junction fuel cell obtained in the embodiment.

Detailed ways

The specific technical solutions of the present invention are described with reference to the embodiments.

(1) Synthesize Ce _0.8 Sm _0.2 O _2-δ doped with ionic conductor material Sm, namely SDC, and the method used is co-precipitation method:

a. According to the stoichiometric ratio of each element (Ce and Sm) in the SDC molecular formula, that is, Ce ³⁺ : Sm ³⁺ is 4:1 and equal proportions of Ce(NO ₃ ) ₃ 6H ₂ O and Sm ( NO ₃ ) ₃ ·6H ₂ O, and the above two samples were dissolved in an appropriate amount of deionized water, and after fully stirring, a uniform mixed solution with a concentration of 1 mol/L was prepared;

b. Weigh an appropriate amount of NH ₄ HCO ₃ powder according to the ratio of bicarbonate ion: metal ion to 3:1, and then dissolve it in deionized water to make 1 mol/L NH ₄ HCO ₃ solution;

c. Slowly add the NH ₄ HCO ₃ solution dropwise to the metal ion mixed solution synthesized in step 2 with a plastic-tip dropper (continuous stirring during this process) to form a white precipitate. After thorough stirring, the precipitate was filtered and washed with deionized water for several times, and then the white precipitate was placed in a drying box for drying at 120°C for 12h;

d. Finally, the dried product was put into a muffle furnace for sintering at 800° C. for 4 hours to obtain SDC powder.

SnO ₂ was purchased from Sinopharm Chemical Reagent Co., Ltd.;

(2) Fully grind the prepared SDC and SnO ₂ according to different proportions to obtain SDC-SnO ₂ semiconductor-ion conductors with different SnO ₂ contents (10%, 20%, 30%, 40%, 50%, 60%) composite material.

(3) Manufacturing process of fuel cell:

aBattery preparation:

(a) Add 2 g of NCAL powder to 5 mL of terpineol, grind for 10 min to make the two fully and uniformly mixed to prepare NCAL slurry. The prepared slurry was coated on nickel foam with a thickness of 2 mm, and then dried in a drying oven at 120 °C for 1 h to complete the preparation of Ni-NCAL electrodes;

Ni _0.8 Co _0.15 Al _0.05 LiO _δ (NCAL) was purchased from Tianjin Baomo United High-Tech Company,

(b) Weigh 0.35g of SDC-SnO ₂ semiconductor-ion conductor composite material, put the Ni-NCAL layer, SDC-SnO ₂ composite powder, and Ni-NCAL layer into the mold in turn, and apply a pressure of 9 MPa by a hydraulic press to make the three layers The structure is pressed into a battery blank.

bBattery test:

The pressed green sheets were put into the test furnace and pre-sintered at 550°C for 35 minutes. After the sintering is completed, at the test temperature of 550 °C, the battery performance test is carried out by feeding H ₂ as fuel, air as oxidant, and hydrogen flow control as 120 ml/min. The battery shows good power output and high open circuit voltage; change SDC /SnO ₂ weight percentage, obtained composite materials with different SnO 2 contents, assembled into batteries, and tested the battery performance. The optimum _SnO content is obtained.

Fig. 1 shows the fuel cell composed of SDC-SnO ₂ composite materials with different SDC contents in the example, and the performance test results at 550°C. As shown in Figure 1, the battery performance starts to increase gradually with the increase of SnO2 content, and then decreases. When the SnO2 content is 20%, the battery performance reaches the maximum value of 1059 mW/cm ² . As the content of SnO ₂ further increases, the electron concentration inside the battery increases, SnO ₂ forms a continuous electron conduction channel, and a short circuit occurs to a certain extent, so the battery performance decreases.

Lower the test temperature to 500°C to test the battery performance output. Verify the low temperature operating performance of the battery.

Figure 2 shows the performance test results of the battery prepared with the optimum ratio of SDC-SnO ₂ at 500°C. The battery still has good performance at low temperature (500°C), and can reach 500mW/cm ² .

Figure 3 is a SEM cross-sectional view of the Schottky fuel cell assembled based on the SDC-SnO ₂ semiconductor-ion conductor composite material. The battery has an obvious three-layer structure, with symmetrical nickel foam electrodes coated with NCAL on both sides, and the thickness of both electrode layers is 200 μm. In the middle is the SDC- _SnO2 composite functional layer with a thickness of 500 μm. FIG. 4 is a rectification curve diagram obtained by applying a scanning voltage to both ends of the Schottky junction fuel cell constructed by SnO ₂ -SDC semiconductor-ion conductor.

Claims (3)

1. Based on SnO₂Production of Schottky junction fuel cell of-SDC semiconductor-ion conductorThe preparation method is characterized by comprising the following steps:

1) synthesis of Sm-doped Ce as ion conductor material_0.8Sm_0.2O_2-Namely SDC;

2) mixing the prepared SDC and SnO₂Fully grinding according to different weight proportions to obtain different SnO₂Content of SDC/SnO₂A composite material;

3) adding 2g of NCA L powder into 5m L of terpineol according to the following proportion, grinding for 10min to fully and uniformly mix the powder and the terpineol to prepare NCA L slurry, coating the NCA L slurry on foamed nickel with the thickness of 2mm, and then drying for 1h at 120 ℃ in a drying box to prepare a Ni-NCA L electrode;

4) 0.35g of SDC-SnO is weighed₂The semiconductor-ion conductor composite material comprises Ni-NCA L electrode, SDC-SnO₂And sequentially putting the composite powder and the Ni-NCA L electrode into a die, and pressing the three-layer structure into a battery blank sheet by applying 9MPa pressure by using a hydraulic press.

2. A SnO based according to claim 1₂-method for preparing a SDC semiconductor-ion conductor schottky junction fuel cell, characterized in that SDC is synthesized comprising the steps of:

a) ce in the molecular formula of SDC³⁺:Sm³⁺The molar ratio of 4:1, and the corresponding mass of Ce (NO) is weighed in equal proportion₃)₃·6H₂O and Sm (NO)₃)₃·6H₂Dissolving the mixture into a proper amount of deionized water, and uniformly stirring to prepare a metal ion mixed solution of 1 mol/L;

b) according to the bicarbonate ion: the metal ion molar ratio is 3: 1 weighing appropriate amount of NH₄HCO₃The powder was dissolved in deionized water to make 1 mol/L NH₄HCO₃A solution;

c) NH is dripped by a rubber head dropper₄HCO₃Slowly dripping the solution into the metal ion mixed solution, continuously stirring the solution to form a white precipitate, filtering the precipitate, washing the precipitate with deionized water for multiple times, and then putting the white precipitate into a drying oven to dry for 12 hours at 120 ℃;

d) finally the dried product was placed in a muffle furnace at 800 ℃ and sintered for 4h to obtain SDC powder.

3. A SnO based according to claim 1 or 2₂The preparation method of the Schottky junction fuel cell of the-SDC semiconductor-ion conductor is characterized in that the SDC/SnO in the step (2)₂SnO in composite materials₂The mass content is 10-60%.

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