Chapter 12: In Vitro Light-Driven Hydrogen Production

In this chapter, we review some of the different approaches to integrate biological hydrogen-activating enzymes, or hydrogenases, as catalysts with both natural and chemical light-harvesting, and charge-separation systems. The transformation of photon energy into chemical bond energy has long been viewed as a renewable and sustainable route to the generation of reduced chemical compounds for use as fuels and other products. Biology accomplishes this process, known as photosynthesis, through the function of supramolecular assemblies that capture light to generate electrochemical gradients that are used to power enzymatic reactions. Some of the fundamental physical and photochemical principles of photosynthetic reactions are being found to also control how chemically derived light-absorbing molecules couple to reduction-oxidation catalysts. We will summarize examples of the work being conducted towards the evolution of functional, solar-based molecular systems; the scientific challenges to developing efficient conversion; and the broader understanding and insights that are emerging for coupling molecules and assemblies to achieve solar-driven fuel production.