NOVELTY - Core-shell catalyst material comprises: a core material having a core crystal structure; and a shell material encompassing and attached to the core material at a core-shell interface. The shell material comprises a catalytically active material, where a circumferential stress of the shell material ( sigma - theta theta ), at the core-shell interface, is greater than 0 (tensile) or compressive of a lower magnitude than a catalyst material formed solely of the shell material.    USE - The catalyst material is useful in electrochemical devices including proton exchange membrane fuel cells (PEMFC) as cathode and anode catalysts in PEMFC for automotive applications and stationary applications.    ADVANTAGE - The core-shell catalyst material has a reduced degradation time compared to a catalyst of a same size and shape and composed substantially of the catalytically active material, while undergoing active catalyst activity. The catalyst material has biaxial tensile stress in the shell and balancing compressive stress in the core, and exhibits high catalytic activity and excellent stability. The catalyst material allows attainment of a low precious metal loading, thus lowering cost.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method of making a core-shell catalyst, comprising: selecting a core material having a core material lattice and a shell material having a shell material lattice, where the core material lattice and the shell material lattice are similar enough to form a coherent interface; forming a core of the core material; and forming a shell of the shell material encompassing and attached to the core. The shell material is under tensile stress or a compressive stress of a lower magnitude than a catalyst material of common dimensions as the core-shell catalyst and made solely of the shell material.    DESCRIPTION OF DRAWING(S) - The figure shows a core-shell particle.    Core-shell catalyst particle (30)    Precious metal shell (32)    Core (34)