This book extracts the most important information on fuel cells, analyze this information, and assess its scientific value and technical importance. It provides a full yet concise description of all important aspects of fuel cells from historical development and major types of fuel cells to inherent scientific and engineering problems and the commercialization and applications of fuel cells. The introduction establishes what a fuel cell is and its economic significance. The Second Edition adds two new chapters, one on structural and wetting properties of porous fuel cell components and the other on fuel cells with mixed reactant supply. The new edition also updates all chapters with current knowledge for each topic.