▎ 摘　　要

NOVELTY - The electrode catalyst material (1) comprises a nanocrystal piece (21) that is in flaky shape. The nanocrystal piece has an interval opened, and arranged between the main surfaces (22) on an outer side of the connection aggregate (20). The average thickness of the nanocrystal piece is less than ten nm. The metal oxide is a copper oxide. The average dimension of an orthogonal direction is less than ten nm with respect to the surface direction of the planar unit. The electroconductive material (30) is a graphene. The electrical conductivity of an electrode catalyst material formed on an electrode is four per cent, or more with respect to an electrical conductivity of the layer formed by an electroconductive material on an electrode. USE - Electrode catalyst material for fuel cells. ADVANTAGE - The electrode catalyst material have high catalytic activity in, which platinum fine particles are supported on the surface of carbon particles in an oxygen reduction reaction, without using platinum as a catalyst component. DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of an electrode catalyst material. Electrode catalyst material (1) Connection aggregate (20) Nanocrystal piece (21) Main surfaces (22) Electroconductive material (30)