World demand for energy is rapidly increasing and is projected to more than double by the year 2050. Finding sufficient supplies of clean energy for the future is one of the major scientific challenges of today. Sunlight accounts for the largest energy input into the earth's surface, providing more energy in one hour than all of the energy consumed by the entire planet in one year. Over more than 2 billion years, plants, algae and cyanobacteria have evolved the most efficient methods to utilize solar energy, by catalyzing the light-driven splitting of water into molecular oxygen, protons and electrons. If the released protons are captured and reduced to molecular hydrogen by a suitable hyrodrogenase enzyme, then a perfect fuel cycle can be achieved, since the combustion of hydrogen with oxygen produces only water. In the search for clean, energy-rich fuel sources, we can take advantage of the natural photosynthetic and hydrogenase systems by applying and adapting the energy conserving principles that Nature has evolved in these systems and use them to guide the development of synthetic photo- and reductive catalysts for solar energy utilization.
The US Department of Energy Basic Sciences Workshops in 2005 on 'Solar Energy Utilization' and in 2007 on 'Catalysis for Energy' identified the development of solar fuels as a key, carbon-neutral, energy resource for the future and hydrogen is one such promising example. The energy released from the combustion of hydrogen with oxygen can be coupled to electrical current generation or the reduction of carbon compounds such as carbon dioxide. If hydrogen could be readily produced from water using solar energy, then an ideal fuel cycle would be possible.
The main aim of the book is to present the latest knowledge and chemical prospects in developing hydrogen as a solar fuel. Using oxygenic photosynthesis and hydrogenase enzymes for bio-inspiration, this book presents the strategies for developing photocatalysts to produce a molecular solar fuel and is divided into five parts. The first part consists of two chapters which give an overall perspective of solar energy utilization and the role that synthetic photocatalysts can play in producing solar fuels. The next three parts summarize current knowledge with respect to the three steps in solar energy utilization: light capture, photochemical conversion, and energy storage in chemical bonds. Each aspect begins with a review of the natural system, emphasizing those biological features which optimize the efficiency of the reactions that it catalyzes. The chapters on the natural systems are then followed by chapters summarizing the latest developments in synthetic chemistry of photo- and reductive catalysts. Finally, the last part gives some future research goals that are important for the practical utilization of solar energy. The book is written by experts from various fields working on the biological and synthetic chemical side of molecular solar fuels to facilitate advancement in this area of research.