Photochemical Conversion of Solar Energy

Abstract

Energy is the most important issue of the 21st century. About 85% of our energy comes from fossil fuels, a finite resource unevenly distributed beneath the Earth's surface. Reserves of fossil fuels are progressively decreasing, and their continued use produces harmful effects such as pollution that threatens human health and greenhouse gases associated with global warming. Prompt global action to solve the energy crisis is therefore needed. To pursue such an action, we are urged to save energy and to use energy in more efficient ways, but we are also forced to find alternative energy sources, the most convenient of which is solar energy for several reasons. The sun continuously provides the Earth with a huge amount of energy, fairly distributed all over the world. Its enormous potential as a clean, abundant, and economical energy source, however, cannot be exploited unless it is converted into useful forms of energy. This Review starts with a brief description of the mechanism at the basis of the natural photosynthesis and, then, reports the results obtained so far in the field of photochemical conversion of solar energy. The "grand challenge" for chemists is to find a convenient means for artificial conversion of solar energy into fuels. If chemists succeed to create an artificial photosynthetic process, "... life and civilization will continue as long as the sun shines!", as the Italian scientist Giacomo Ciamician forecast almost one hundred years ago.

Highly efficient and robust molecular ruthenium catalysts for water oxidation

“…I n pursuit of sustainable energy systems such as solar fuels, much effort has been spent on water splitting to hydrogen and oxygen since hydrogen is a potential clean energy carrier and water is an abundant and environmentally benign resource (1)(2)(3)(4)(5). Water splitting consists of two half reactions: (i) water oxidation {H 2 O → 1∕2O 2 þ 2H þ þ 2e − [E ¼ 1.23-0.059 × pH V vs. normal hydrogen electrode (NHE)]} and (ii) proton reduction [2H þ þ 2e − → H 2 (E ¼ −0.059 × pH V vs. NHE)].…”

Water oxidation surface mechanisms replicated by a totally inorganic tetraruthenium–oxo molecular complex

“…Our aerobic life is based on this strategy, mastered by the natural Photosystem II enzyme, using a tetranuclear Mn-oxo complex as oxygen evolving center. Within artificial devices, water can be oxidized efficiently on tailored metal-oxide surfaces such as RuO 2 . The quest for catalyst optimization in vitro is plagued by the elusive description of the active sites on bulk oxides.…”

“…artificial photosynthesis | ab initio simulations | X-ray absorption spectroscopy | electrocatalysis P hotocatalytic water splitting offers a bioinspired strategy for replacing fossil fuels with clean energy vectors (1)(2)(3). The overall reaction entails a sequence of light-promoted electron and proton transfers coupled with cleavage and formation of molecular bonds, ultimately splitting H 2 O molecules into O 2 and H 2 .…”

On the interactions between molecules in an off-resonant laser beam: Evaluating the response to energy migration and optically induced pair forces

“…1 RET operates across a chemically diverse and extensive range of material systems. Its most widely known role is in the channeling of electronic excitation in photosynthetic systems [2][3][4] and their biomimetic analogs. [4][5][6][7] The phenomenon also has an important function in the operation of organic light-emitting diodes and luminescence detectors.…”

“…Its most widely known role is in the channeling of electronic excitation in photosynthetic systems [2][3][4] and their biomimetic analogs. [4][5][6][7] The phenomenon also has an important function in the operation of organic light-emitting diodes and luminescence detectors. 8,9 In the realm of molecular biology, the determination of protein structures and the characterization of dynamical processes are furthered by studies of the transfer of energy between chromophores; [10][11][12] several ultrasensitive molecular imaging applications are again based on the same underlying principle.…”