Porous core-shell catalyst and method for fabricating the same

1. A method of manufacturing a porous core-shell catalyst structure, the method comprising:

preparing a bulk cobalt oxide having a first oxygen content;

providing a first reaction gas containing nitrogen to the bulk cobalt oxide to produce an intermediate product containing a porous cobalt oxide, wherein the intermediate product has a second oxygen content that is lower than the first oxygen content; and

providing a second reaction gas containing sulfur to the intermediate product to produce a porous core-shell catalyst structure including a core formed of the porous cobalt oxide and a shell formed of cobalt sulfide.

2. The method of claim 1 , wherein

the shell includes (a) a first cobalt sulfide having a first sulfur ratio and (b) a second cobalt sulfide having a second sulfur ratio that is higher than the first sulfur ratio, and

a ratio of the first cobalt sulfide and a ratio of the second cobalt sulfide are controlled by a time and a temperature at which the second reaction gas is provided to the intermediate product.

3. The method of claim 1 , wherein the first reaction gas includes an ammonia gas.

4. The method of claim 1 , wherein the second reaction gas includes a hydrogen sulfide gas.

5. The method of claim 1 , wherein, in the core-shell catalyst structure, a ratio of the core and the shell is controlled by time and temperature with which the second reaction gas is provided to the intermediate product.

6. A method of manufacturing a dye-sensitized solar cell, the method comprising:

preparing the porous core-shell catalyst structure according to claim 1 ;

forming a photoelectric conversion layer including an electrode particle and a dye layer adsorbed on a surface of the electrode particle on a first substrate;

forming a guide film on a second substrate by pretreating the second substrate with a basic solution;

forming an electrode film using the porous core-shell catalyst structure on the guide film;

arranging the first substrate and the second substrate so that the electrode film and the photoelectric conversion layer face each other; and

injecting an electrolyte solution between the first substrate and the second substrate.

7. A method of manufacturing a porous core-shell catalyst structure, the method comprising:

preparing a bulk cobalt oxide having a first oxygen content;

providing a first reaction gas containing nitrogen to the bulk cobalt oxide to produce an intermediate product that consists essentially of a porous cobalt oxide and that has a second oxygen content that is lower than the first oxygen content; and

providing a second reaction gas containing sulfur to the intermediate product to produce a porous core-shell catalyst structure including a core formed of the porous cobalt oxide and a shell formed of cobalt sulfide.

8. A method of manufacturing a porous core-shell catalyst structure, the method comprising:

preparing a bulk cobalt oxide having a first oxygen content;

converting, at a first reaction temperature, and using a first reaction gas that includes nitrogen, a first portion of the bulk cobalt oxide to a first porous cobalt oxide having a rock salt structure with a first grain size, thereby producing a first state intermediate product comprising a mixture of the first porous cobalt oxide and a remaining portion of the bulk cobalt oxide, the remaining portion having a spinel structure;

converting, at a second reaction temperature that is higher than the first reaction temperature, the remaining portion of the bulk cobalt oxide to a second porous cobalt oxide having a second grain size that is larger than the first grain size; and

providing a second reaction gas containing sulfur to the second porous cobalt oxide to produce a porous core-shell catalyst structure including a core that includes the second porous cobalt oxide and a shell formed of cobalt sulfide.

9. The method of claim 8 , wherein:

the bulk cobalt oxide is Co 3 O 4 ; and

the first and second porous cobalt oxides are CoO.

10. The method of claim 8 , wherein the shell includes (a) a first cobalt sulfide having a first sulfur ratio and (b) a second cobalt sulfide having a second sulfur ratio that is higher than the first sulfur ratio.

11. The method of claim 8 , wherein the shell includes (a) a first cobalt sulfide having a first electrocatalytic activity and (b) a second cobalt sulfide having a second electrocatalytic activity that is less than the first electrocatalytic activity.

12. The method of claim 8 , wherein the shell includes (a) a first cobalt sulfide having a first electrocatalytic activity that is greater than 82.62% and less than 95.67%, and (b) a second cobalt sulfide having a second electrocatalytic activity that is greater than 4.33% and less than 17.38%.

13. The method of claim 8 , wherein providing the second reaction gas containing sulfur to the second porous cobalt oxide comprises:

in a reaction chamber, providing the second reaction gas to the second porous cobalt oxide during a temperature increasing operation;

after the temperature increasing operation, providing the second reaction gas to the second porous cobalt oxide during a temperature maintaining operation;

after the temperature maintaining operation, performing a temperature reduction operation; and

after the temperature reduction operation, providing nitrogen gas to remove the second reaction gas from the reaction chamber.