Photosynthesis converts solar energy into what type of energy

Highlights

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This review summarizes the research trends of natural, semi-artificial and artificial photosynthesis in terms of concepts, design, and examples.

Biohydrogen production via photosynthesis and direct energy production, and production of hydrogen in natural systems in vivo.

Semi-artificial system in vitro and the ways of producing biohydrogen in semi-artificial devices.

Relations between structures and photoinduced reactivities of the reported artificial photosynthetic donor-acceptor systems are discussed in relation to the efficiency.

Photocatalytic production of hydrogen peroxide as a more promising solar fuel than hydrogen is discussed in relation with the natural photosynthesis.

Abstract

Solar energy has a great potential as a clean, cheap, renewable and sustainable energy source, but it must be captured and transformed into useful forms of energy as plants do. An especially attractive approach is to store solar energy in the form of chemical bonds as performed in natural photosynthesis. Therefore, there is a challenge in the last decades to construct semi-artificial and artificial photosynthetic systems, which are able to efficiently capture and convert solar energy and then store it in the form of chemical bonds of solar fuels such as hydrogen or hydrogen peroxide, while at the time producing oxygen from water. Here, we review the molecular level details of the natural photosynthesis, particularly the mechanism of light dependent reactions in oxygen evolving organisms, absorption efficiency of solar energy and direct energy production. We then demonstrate the concept and examples of the semi-artificial photosynthesis in vitro. Finally we demonstrate the artificial photosynthesis, which is composed of light harvesting and charge-separation units together with catalytic units of water oxidation and reduction as well as CO2 reduction. The reported photosynthetic molecular and supramolecular systems have been designed and examined in order to mimic functions of the antenna-reaction center of the natural process. The relations between structures and photochemical behaviors of these artificial photosynthetic systems are discussed in relation to the rates and efficiencies of charge-separation and charge-recombination processes by utilizing the laser flash photolysis technique, as well as other complementary techniques. Finally the photocatalytic production of hydrogen peroxide as a more promising solar fuel is discussed in relation with the natural photosynthesis, which also produces hydrogen peroxide in addition to NADPH.

Keywords

Natural photosynthesis

Artificial photosynthesis

Semi-artificial photosynthesis

Mohamed E. El-Khouly was born in Egypt and earned his PhD degree in photochemistry from Tohoku University, Japan (2002). After that, he continued his research in Japan funded from Venture Business Laboratory (2003–2004), Center of Excellence (2004–2006), and Japan Society for the Promotion Science (2006–2008). In the period of 2008–2012, he joined the research group of Prof. Shunichi Fukuzumi at Osaka University as a specially appointed Associate Professor. Sine 2013, he has been a Full Professor at Kafrelsheikh University. His research interests are mainly focused on ultrafast laser photolysis of the molecular and supramolecular light harvesting systems, carbon nanostructures, artificial photosynthesis complexes, material science, and laser chemistry.

Eithar El-Mohsnawy was born in Egypt and received his PhD degree in the Algal Biotechnology from Faculty of Biology and Biotechnology, Ruhr-University Bochum, Germany (2007). He was hired as a Lecturer at Suez Canal University, Egypt on 2007. Since 2014, he moved to Kafrelsheikh University as an Associate Professor. His research interests involved photosystem 1 structure and function, photosynthetic electron transport chain, native and semi-artificial photosynthesis, and biohydrogen production.

Shunichi Fukuzumi earned a bachelor’s degree and PhD degree in applied chemistry at Tokyo Institute of Technology in 1973 and 1978, respectively. After working as a postdoctoral fellow (1978–1981) at Indiana University in USA, he joined the Department of Applied Chemistry, Osaka University, as an Assistant Professor in 1981 and was promoted to a Full Professor in 1994. His research interests are artificial photosynthesis and electron transfer chemistry. He was the leader of an ALCA (Advanced Low Carbon Technology Research and Development) project that started in 2011. He is now a Distinguished Professor of Ewha Womans University, a Designated Professor of Meijo University, a Professor Emeritus of Osaka University.

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