Carbon nanomaterials as metal-free catalysts in next generation fuel cells

The rapid increase in the global energy consumption and the environmental impact of traditional energy resources pose serious challenges to human health, energy security, and environmental protection. One promising solution, providing clean and sustainable power, is fuel cells. Instead of burning fuel to create heat, fuel cells convert chemical energy directly into electricity [1]. This energy conversion technology currently receives intensive research and development focus because of its high energy conversion efficiency (typically, 40–60% or up to 85% efficiency if waste heat is captured for use), virtually no pollution, and potential large-scale applications [2]. By pumping, for example, hydrogen gas onto the anode, hydrogen is split into its constituent electrons and protons. The protons diffuse through the cell toward the cathode while the electrons