Electrocatalyst layers include an electrocatalyst having high oxygen reduction activity that is useful as an alternative material to platinum catalysts. Uses of the electrocatalyst layers are also disclosed.The electrocatalyst layer includes an electrocatalyst that is formed of a metal oxide obtained by thermally decomposing a metal organic compound. The metal element forming the electrocatalyst is preferably one selected from the group consisting of niobium, titanium, tantalum and zirconium.