ELECTRICALLY HEATED EXHAUST GAS PURIFICATION CATALYST

1 . An electrically heated exhaust gas purification catalyst comprising:

a substrate;

at least one pair of electrodes provided on the substrate;

an undercoat layer provided on the substrate, the undercoat layer containing an aluminum element as a main component; and

a catalyst layer provided on the undercoat layer, the catalyst layer containing a noble metal element,

wherein the undercoat layer contains a Group 2 element.

2 . The exhaust gas purification catalyst according to claim 1 , wherein an amount of the aluminum element contained in the undercoat layer is 50 mol % or more based on a total molar amount of all metal elements contained in the undercoat layer.

3 . The exhaust gas purification catalyst according to claim 1 , wherein an amount of the Group 2 element contained in the undercoat layer is 1 mol % or more and 40 mol % or less based on a total molar amount of all metal elements contained in the undercoat layer.

4 . The exhaust gas purification catalyst according to claim 1 , wherein a total amount of the aluminum element and the Group 2 element contained in the undercoat layer is 85 mol % or more and 100 mol % or less based on a total molar amount of all metal elements contained in the undercoat layer.

5 . The exhaust gas purification catalyst according to claim 1 , wherein the aluminum element contained in the undercoat layer and the Group 2 element contained in the undercoat layer are in the form of a composite.

6 . The exhaust gas purification catalyst according to claim 1 , wherein the Group 2 element contained in the undercoat layer is selected from a magnesium element, a calcium element, a strontium element, and a barium element.

7 . The exhaust gas purification catalyst according to claim 6 , wherein the Group 2 element contained in the undercoat layer is a magnesium element.

8 . The exhaust gas purification catalyst according to claim 1 , wherein the substrate is an electroconductive ceramic substrate.

9 . The exhaust gas purification catalyst according to claim 8 , wherein the ceramic substrate contains a silicon-element-containing inorganic conductor as a main component.

10 . The exhaust gas purification catalyst according to claim 1 , wherein the noble metal element contained in the catalyst layer is a palladium element.

11 . The exhaust gas purification catalyst according to claim 1 , wherein locations of the Group 2 element and the aluminum element coincide at a correlation coefficient of 50% or more, and wherein the correlation coefficient is obtained by performing a line analysis of the undercoat layer with an electron probe microanalyser, and calculating the correlation coefficient in accordance with the following equation:

Correlation

⁢

coefficient

=

∑

i

=

1

n

⁢

(

x

i

-

x

av

)

⁢

(

y

i

-

y

av

)

∑

i

=

1

n

⁢

(

x

i

-

x

av

)

2

⁢

∑

i

=

1

n

⁢

(

y

i

-

y

av

)

2

×

100

⁢

(

%

)

wherein x i represents a characteristic X-ray intensity of the Group 2 element at location i, x av represents an average value of characteristic X-ray intensities of the Group 2 element, y i represents a characteristic X-ray intensity of the aluminum element at location i, and y av represents an average value of characteristic X-ray intensities of the aluminum element.

12 . The exhaust gas purification catalyst according to claim 1 , wherein the undercoat layer substantially does not comprise a composite oxide containing a cerium element and a zirconium element.

13 . The exhaust gas purification catalyst according to claim 1 , wherein the undercoat layer substantially does not comprise a noble metal element.