Highly dispersed Pt-based catalysts on a conductive support are commonly used as electrode materials in low-temperature fuel cells. The performance and durability/stability of these catalysts strongly depend on the characteristics of the support. Catalysts supported on high surface area carbon black are widely used in fuel cells (FCs). However, the corrosion of carbon black has been recognized as one of major causes of performance degradation and durability issues of FCs under high-potential conditions. So the need for alternative supports with outstanding physical and mechanical properties to carry out the successful reaction in catalyst layer and give a longer lifetime for the electrocatalysts is inevitable. Development of nanostructure materials in recent years has opened up new avenues of materials development for FCs. This book presents the performance with a variety of carbon based nanostructured materials such as CNFs, CNTs, carbon arogels, GNPs, non-carbonaceous based materials, e.g metal oxides and carbides nanowires , nanorods , the nanostructer of conductive polymers e.g. PAni / PPy nanofibers/ nanowires as well as composites of these materials as catalyst supports.