Hydrogen production catalyst, method for producing hydrogen and hydrogen production apparatus using the same

1. A hydrogen production catalyst for generating hydrogen, the catalyst comprising a composite metal oxide of cerium oxide and praseodymium oxide, the catalyst being effective to thermochemically split water,

wherein the composite metal oxide has a fluorite-type crystal structure and an average primary particle diameter of the composite metal oxide is in the range of 15 nm or less after being heated in an inert gas atmosphere at 800° C. for 1 hour.

2. The hydrogen production catalyst according to claim 1 , wherein a content ratio of the cerium oxide and the praseodymium oxide in the composite metal oxide is in the range of 95:5 to 5:95 in terms of an atomic ratio ([cerium]:[praseodymium]) of the metal elements.

3. The hydrogen production catalyst according to claim 1 , wherein the composite metal oxide further comprises aluminum oxide.

4. The hydrogen production catalyst according to claim 3 , wherein a content of the aluminum oxide is in the range of 5 to 50% by mass relative to a total amount of the cerium oxide, the praseodymium oxide, and the aluminum oxide.

5. The hydrogen production catalyst according to claim 1 , wherein the composite metal oxide satisfies the following conditions:

a total pore volume of pores having pore diameters in a range from 1 nm to 0.1 μm measured by a nitrogen adsorption method is in the range of 0.18 cm 3 /g or more after being calcined in air at 1100° C. for 5 hours, and

a total pore volume of pores having pore diameters in a range from 0.1 μm to 10 μm measured by a mercury intrusion method is in the range of 0.2 cm 3 /g or more after being calcined in air at 1100° C. for 5 hours.

6. The hydrogen production catalyst according to claim 1 , wherein the specific surface area of the composite metal oxide is in the range of 1 to 200 m 2 /g.

7. The hydrogen production catalyst according to claim 6 , wherein the specific surface area of the composite metal oxide is in the range of 62 to 200 m 2 /g.

8. A method for producing hydrogen by thermochemically splitting water using a hydrogen production catalyst comprising a composite metal oxide of cerium oxide and praseodymium oxide wherein the composite metal oxide has a fluorite-type crystal structure, the method comprising:

thermally reducing the composite metal oxide; and

splitting water by bringing water into contact with the reduced composite metal oxide to thereby generate hydrogen and oxidize the composite metal oxide,

wherein an average primary particle diameter of the composite metal oxide is in the range of 15 nm or less after being heated in an inert gas atmosphere at 800° C. for 1 hour.

9. The method for producing hydrogen according to claim 8 , wherein the composite metal oxide is thermally reduced in an inert gas atmosphere under a temperature in the range of 400 to 900° C.

10. The method for producing hydrogen according to claim 8 , wherein during the splitting, the water is brought into contact with the composite metal oxide under a temperature in the range of 50 to 600° C.

11. A hydrogen production apparatus, comprising:

a hydrogen production catalyst configured to generate hydrogen, the catalyst comprising a composite metal oxide of cerium oxide and praseodymium oxide wherein the composite metal oxide has a fluorite-type crystal structure, the catalyst being effective to thermochemically split water;

a reaction vessel configured to receive the hydrogen production catalyst;

a water supplier connected to the reaction vessel, the water supplier configured to supply water into the reaction vessel;

an inert gas supplier connected to the reaction vessel, the inert gas supplier configured to supply an inert gas into the reaction vessel;

an exhaust pipe connected to the reaction vessel, the exhaust pipe configured to discharge gas in the reaction vessel; and

a heater configured to heat the inside of the reaction vessel, wherein

the reaction vessel, is configured to (i) thermally reduce the composite metal oxide and (ii) split water by bringing water into contact with the reduced composite metal oxide to thereby generate hydrogen and oxidize the composite metal oxide, and

an average primary particle diameter of the composite metal oxide is in the range of 15 nm Of less after being heated in an inert gas atmosphere at 800° C. for 1 hour.

12. The hydrogen production apparatus according to claim 11 , wherein the heater heats the inside of the reaction vessel by utilizing heat of sunlight.