A quest for the artificial leaf

It has been estimated that the energy captured in one hour of sunlight that reaches our planet is equivalent to annual energy production by human population globally. To efficiently capture the practically inexhaustible solar energy and convert it into high energy density solar fuels provides an attractive 'green' alternative to running our present day economies on rapidly depleting fossil fuels, especially in the context of ever growing global energy demand. Natural photosynthesis represents one of the most fundamental processes that sustain life on Earth. It provides nearly all the oxygen we breathe, the food we consume and fossil fuels that we so much depend on. Imitating the reactions that occur at the early stages of photosynthesis represents the main challenge in the quest for construction of an efficient, robust, self-renewing and cost-effective 'artificial leaf'. In this review we summarize the main molecular features of the natural solar energy converters, photosystem I and photosystem II, that allow them to operate at high quantum efficiencies, and thus inspire the smart matrix design of the artificial solar-to-fuel devices. We also discuss the main challenges that face the field and overview selected recent technological advances that have tremendously accelerated the race for a fully operational artificial leaf that could serve as a viable alternative to fossil fuels for energy production.