Metal-air fuel cell based on solid oxide electrolyte employing metal nanoparticle as fuel

Abstract

Disclosed is a metal-air fuel cell based on a solid oxide electrolyte employing metal nanoparticles as fuel. The metal-air fuel cell includes an anode, a cathode, a solid oxide electrolyte and a metal fuel, wherein the metal fuel comprises metal nanoparticles having an average particle diameter ranging from 1 nm to 100 nm. The metal nanoparticles have a low melting point and provide high reactivity. Thus, the metal-air fuel cell forms a metal molten phase at a relatively low temperature thereby improving contactability and has improved reactivity to promote oxidation, thereby enabling highly efficient power generation.

Claims

1. A metal-air fuel cell based on a solid oxide electrolyte, comprising: an anode; a cathode; a solid oxide electrolyte; and a metal fuel, wherein the metel fuel comprises metal nanoparticles dispersed in an organic solvent, the metal nanoparticles having an average particle diameter ranging from 1 nm to 100 nm, wherein a melting point of the metal of the metal nanoparticle is lower than a melting point of the metal at micro or macro scale, and wherein the metal fuel is a metal selected from the group consisting of Sn, V.sub.2O.sub.5, In, Sb, Pb, hi, Ag, and mixtures thereof.

2. The metal-air fuel cell according to claim 1, wherein the metal fuel is a gel phase metal fuel comprising the metal nanoparticles dispersed in an organic solvent.

3. The metal-air fuel cell according to claim 2, wherein the organic solvent is ethylene glycol.

4. The metal-air fuel cell according to claim 2, wherein the metal nanoparticles are present in an amount of 80 parts by weight to 95 parts by weight based on 100 parts by weight of the organic solvent.

5. The metal-air fuel cell according to claim 1, wherein the metal fuel is Sn.

6. The metal-air fuel cell according to claim 1, wherein the anode is a porous nickel-gadolinium doped cerium oxide electrode or a porous nickel-yttria stabilized zirconia electrode.

7. The metal-air fuel cell according to claim 1, wherein the solid oxide electrolyte is yttrium-stabilized zirconia.

8. The metal-air fuel cell according to claim 1, wherein the cathode is composed of lanthanum-strontium-manganate.

9. A metal-air fuel cell based on a solid oxide electrolyte, comprising: an anode, wherein the anode is a porous nickel-gadolinium doped cerium oxide electrode or a porous nickel-yttria stabilized zirconia electrode, a cathode, wherein the cathode is composed of lanthanum-strontium-manganate, a solid oxide electrolyte, wherein the solid oxide electrolyte is yttrium-stabilized zirconia, and a metal fuel wherein the metal fuel is Sn, wherein the metal fuel comprises metal nanoparticles having an average particle diameter ranging from 1 nm to 100 nm, wherein the metal fuel comprises the metal nanoparticles dispersed in an organic solvent, and wherein the metal nanoparticles are present in an amount of 80 parts by weight to 95 parts by weight based on 100 parts by weight of the organic solvent.

10. The metal-air fuel cell according to claim 9, wherein the metal fuel is a gel phase metal fuel.

11. A metal-air fuel cell based on a sold oxide electrolyte, comprising: an anode; a cathode; a solid oxide electrolyte; and a metal fuel comprising metal nanopartieles dispersed in an organic solvent, the metal nanoparticles configured to be oxidized by oxygen to generate electrons for the metal-air fuel cell, wherein the metal nanoparticles have an average particle diameter ranging from 1 nm to 100 nm, wherein the metal of the metal nanoparticles is one selected from the group consisting of Sn, In, Sb, Pb, Bi, Ag, and mixtures thereof, and wherein a melting point of the metal of the metal nanoparticle is lower than a melting point of the metal at micro or macro scale.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other aspects, features, and advantages of the present invention will become apparent from the detailed description of the following embodiments in conjunction with the accompanying drawings, in which:

(2) FIG. 1 is a diagram of a fuel cell according to one embodiment of the present invention;

(3) FIG. 2 is a graph depicting time-related variation of reaction rates of tin nanoparticles according to an inventive example and bulk tin particles, as analyzed by thermogravimetric analysis (TGA);

(4) FIG. 3 shows a table of open circuit voltage (OCV) of fuel cells employing tin nanoparticles according to the inventive example and the bulk tin particles as fuels, respectively; and

(5) FIG. 4 is a graph depicting time-related variation of constant current density of the fuel cell employing the tin nanoparticles according to the inventive example.

DETAILED DESCRIPTION

(6) Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

(7) The present invention provides a metal-air fuel cell based on a solid oxide employing a metal fuel, which is composed of metal nanoparticles having an average particle diameter of 1 nm to 100 nm and a low melting point to facilitate formation of a molten phase, thereby improving contactability. In addition, with the reduced average nano-scale diameter of the metal particles, the fuel cell provides a high oxidation rate, thereby achieving further improved power generation efficiency.

(8) Referring to FIG. 1, a unit fuel cell according to one embodiment includes a cathode inlet 100; a cathode catalyst 200; an electrolyte 300; an anode catalyst 400; a metal fuel 500; an anode inlet 600; a cell sheath 700; an anode collector 800; a cathode collector 900; and a connecting material 1000.

(9) The metal fuel 500 is a gel phase metal fuel which comprises metal nanoparticles dispersed in an organic solvent, and may be prepared by, for example, mixing ethylene glycol and the metal nanoparticles. However, the present invention is not limited to such an organic solvent or phase, and may be realized in various ways, as needed. That is, the kind of organic solvent or the phase of the metal fuel may be arbitrarily selected according to desired powder, liquid, solid or gel phase fuel by those skilled in the art, as needed.

(10) In the metal fuel 500, the metal nanoparticles have an average particle diameter ranging from 1 nm to 100 nm and thus have a low melting point of 250° C. to 1000° C. Although metal particles have a typical melting point at micro or macro scale, the metal particles exhibit significant reduction in melting point at nano scale. Accordingly, the metal-air fuel cell according to the present embodiment forms a molten phase at a relatively low temperature and exhibits improved contactability with the catalyst. In some embodiments, the metal fuel may be selected from the group consisting of Sn, V.sub.2O.sub.5, In, Sb, Pb, Bi, Ag, and mixtures thereof. Particularly, Sn may be used as the metal fuel.

(11) In the metal-air cell according to the embodiment, the anode catalyst 400 may be a porous nickel-gadolinium doped cerium oxide electrode or a porous nickel-yttria stabilized zirconia electrode. In addition, the electrolyte 300 may be yttrium-stabilized zirconia, and the cathode catalyst 200 may be composed of lanthanum-strontium-manganate. However, it should be understood that the present invention is not limited thereto, and may be realized in various ways, as needed.

(12) In one embodiment, the metal nanoparticles may be present in an amount of 80 parts by weight to 95 parts by weight based on 100 parts by weight of the organic solvent.

(13) Next, the present invention will be more clearly understood from the following examples. It should be understood that the following examples are provided for illustration only and are not to be construed in any way as limiting the present invention.

EXAMPLES

(14) Analysis of Reaction Rate According to Particle Diameter

(15) FIG. 2 is a graph comparing temperature-related variation of reaction rates of tin nanoparticles according to an inventive example and bulk tin particles (particle diameter: about 350 μm). Comparison was carried out by thermogravimetric analysis (TGA, TGA-50 A, Shimadzu, Japan) in consideration of mass increase resulting from oxidation. More specifically, the mass change rate was measured in real time while increasing the temperature from 0° C. to 800° C. at a temperature increase rate of 5° C./min and supplying air gas containing 21% O.sub.2. As can be seen from FIG. 2, when the average particle diameter of the metal particles was reduced to the range from 1 nm to 100 nm, oxidation occurred at a very high rate even at a lower temperature than the case of using the bulk metal particles.

(16) Open Circuit Voltage (OCV) Analysis According to Particle Diameter

(17) FIG. 3 shows a table of open circuit voltage (OCV) of the fuel cells employing the tin nanoparticles according to the inventive example and the bulk tin particles (particle diameter: about 350 μm) as fuels, respectively. From about 30 minutes before reaction to completion of the reaction, inert gas such as argon or nitrogen was injected into the fuel cell through the anode inlet 600 to stabilize a reaction atmosphere, and air gas containing 21% O.sub.2 was injected thereto through the cathode inlet 100. As can be seen from FIG. 3, the fuel cell employing the tin nanoparticles having an average particle diameter of 1 nm to 100 nm had a stable and high OCV, as compared with the fuel cell employing the bulk metal particles, which exhibited a relatively unstable and low OCV.

(18) Analysis Result of Constant Current Density

(19) FIG. 4 is a graph depicting time-related variation in constant current density of the fuel cell employing the tin nanoparticles according to the inventive example. Under typical conditions for operation of a solid oxide fuel cell set to 750° C., inert gas was injected at a rate of 30 mL/min through the anode inlet 600, and air was injected at a rate of 50 mL/min through the cathode inlet 100. The fuel cell prepared in the inventive example stably produced an output power of about 12 mW/cm.sup.2 over a long duration after a short stabilization stage.

(20) In the fuel cell prepared in the inventive example, it is considered that Reactions (1) and (2) occurred in the anode catalyst. A solid oxide metal-air fuel cell in the related art requires very high temperature conditions for contact with the anode catalyst due to high melting point of the metal particles. On the contrary, in the fuel cell employing the metal nanoparticles having an average particle diameter of 1 nm to 100 nm as fuel prepared in the inventive example, it is considered that Reaction (1) occurred at low temperature, and Reaction (2) occurred at a very high rate at the same time, thereby allowing the fuel cell to produce high voltage current with stability.
Sn(s).fwdarw.Sn(l ) (melt)  (1)
Sn(l)+2O.sup.2−.fwdarw.SnO.sub.2+4e.sup.−(oxidation)  (2)

(21) As described above, the fuel cell according to the present invention employs metal particles, which have an average particle diameter of 1 nm to 100 nm and have a lowered melting point and high oxidation reactivity, to secure high contactability using the metal nanoparticles easily melted at a relatively low temperature, thereby reducing resistance between the catalyst and the fuel while continuously producing high voltage current through rapid reaction. In addition, the fuel cell according to the present invention allows the metal nanoparticle fuel to be mixed with an organic solvent or other materials to have a solid, liquid, gel or powdery phase as needed, thereby enabling compatibility.

(22) Although some exemplary embodiments have been described herein, it should be understood by those skilled in the art that these embodiments are given by way of illustration only, and that various modifications, variations and alterations can be made without departing from the spirit and scope of the invention. The scope of the present invention should be defined by the appended claims and equivalents thereof.