Energy consumption/production based on the combustion of fossil fuels has a severe environmental impact. In this context, development of efficient electrochemical energy conversion and storage devices are of paramount importance. Fuel cells and secondary batteries are considered to be the most efficient conversion and storage devices respectively with no or minimum emission. The present thesis focused on electrochemical evaluation of catalysts for polymer electrolyte membrane fuel cell and carbon-based composites as electrode materials for lithium-ion and lithium-sulfur batteries