Recent advances in photosynthetic energy conversion

• Photosynthesis can be manipulated for electricity generation in an electrochemical cell.
• The process can be used to generate clean power with only water and sunlight as raw materials.
• The stability of photosynthetic machineries used must be improved greatly for real applications.
• The use of live cells (cyanobacteria) is preferable over isolated photosystems or thylakoids.

Photosynthesis is one of the first natural processes evolved by cyanobacteria, algae and green plants to trap light and CO2 in the form of reduced carbon compounds while simultaneously oxidizing water to oxygen. The photosynthetic energy conversion forms the basis for all the existing life today. The photosynthetic energy is being harnessed in many ways using modern technologies for the production of fuels using photosynthetic organisms, generation of direct electricity using photosystems/photosynthetic organisms in photo-bioelectrochemical cells or through photovoltaic systems. While the production of energy rich carbon fuels (ethanol, propanol) from photosynthetic organisms has already been accomplished due to advancement in understanding microbial physiology and metabolism, the photosynthetic hydrogen production as well as direct electricity generation from light is still at its infancy. Recent advances include combining photosystem complexes with hydrogenases for hydrogen production, using isolated thylakoids, photosystems on nanostructured electrodes such as gold nanoparticles, carbon nanotubes, ZnO nanoparticles for electricity generation. Many challenging optimizations on the immobilization methods, catalyst stability and isolation procedures, electron transfer strategies have acquired momentum leading to the production of more stable and higher current densities and power densities in photosynthetic devices. Further, the use of whole cell microorganisms (cyanobacteria, microalgae) rather than their isolated counterparts has produced promising results. The photosynthetic energy conversion has an enormous potential for renewable energy generation in a sustainable and environment friendly manner.

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