Clean energy technologies are poised to play an important role in overcoming fossil fuel exhaustion and global pollution. Among these technologies, electrochemical energy storage and conversion are considered to be the most feasible, sustainable, and environmentally friendly. Proton exchange membrane (PEM) fuel cells are prime examples of electrochemical energy conversion technologies in action. Believed to be ideal sources of clean power, PEM fuel cells are replacing internal combustion and diesel engines in vehicles, as well as Pb-acid batteries and diesel generators in the emergency...