The nanoweb includes the nanofibers described above, so that it can have a porosity of 50% or more. As the nanoweb has a porosity of 50% or more, the specific surface area of the porous support 11 is increased, facilitating permeation of the catalyst layer 12. As a result, the efficiency of cells can be improved. Meanwhile, the nanoweb preferably has a porosity of 90% or less. When the nanoweb has a porosity higher than 90%, the subsequent process may not proceed efficiently due to deteriorated shape stability. The porosity may be calculated by the ratio of air volume in the nanoweb to the total volume of the nanoweb in accordance with the following Equation 1. In this case, the total volume is calculated by making a rectangular sample and measuring the width, length and thickness of the material, and the air volume can be obtained by measuring the weight of the sample and subtracting a polymer volume, calculated back from polymer density, from the total volume.
Porosity (%)=(Air volume in nanoweb/Total volume of nanoweb)×100??[Equation 1]

In addition, the nanoweb may have a mean thickness of 5 to 50 μm. When the thickness of the nanoweb is less than 5 μm, mechanical strength may be significantly deteriorated, on the other hand, when the thickness exceeds 50 μm, resistance loss may increase and weight reduction and integration may be deteriorated. More preferably, the nanoweb may have a mean thickness of 10 to 30 μm.

In another embodiment of the present invention, the porous support 11 may include any one selected from the group consisting of carbon paper, carbon cloth, carbon felt and carbon fiber.

The catalyst layer 12 may include a catalyst and a binder resin.