The development of highly active and durable electrocatalysts has been of pivotal importance in renewable energy conversion and storage devices such as fuel cells and electrolyzers. Although precious group metals have been predominantly used as electrocatalysts for such devices during the last several decades, their high costs, declining activity with long-term use, and limited supplies have triggered a great deal of recent efforts toward seeking low-cost alternatives. Our group has been focused on designing nanostructured carbon-based, non-precious metal electrocatalysts for renewable energy conversion reactions, including oxygen reduction, oxygen evolution, and hydrogen evolution reactions (ORR, OER, and HER, respectively). In this talk, I will present our recent efforts in designing new electrocatalysts based on nanoporous/nanostructured carbons with high activity and durability, identifying catalytically active sites in these electrocatalysts by in situ spectroscopic and computational methods, and applying the developed electrocatalysts in system-level devices.