Mesoporous catalysts with enhanced oxygen reduction reaction (ORR) activity for PEM fuel cells are synthesized by alternating sputtering of Pt and Co onto gas diffusion layers with microporous layers. Co is acting as a template for synthesis of a porous Pt nanostructure. For such proposed Pt-Co catalysts the kinetic current in the ORR was found to be increased by a factor of up to 16 and the mass specific current in PEM single cells by a factor of up to 7. Co was found to be deposited at the grain boundary of the Pt layer and dissolves under acidic conditions resulting in a mesoporous Pt catalyst which is advantageous for gas diffusion catalysts. Microstructural and compositional parameters were optimised in order to obtain a high kinetic current and lower onset potential for the ORR. The most favourable Co layer thickness was determined to be 2 nm. The optimal Pt-Co catalyst can be synthesized by continuously varying the Pt layer thickness. The highest Pt mass activity was found at a layer thickness of 30.5 nm. Catalysts were characterised by SEM, EDX, electrochemical half cell and PEM single cell tests. (C) 2014 Elsevier B.V. All rights reserved.