The initial product of photosynthesis is NADPH (dihydronicotinamide adenine dinucleotide phosphate), which is produced from the oxidized form (NADP+) by reduction with two electrons and one proton released from Photosystem I (PSI) via ferredoxin. The proton gradient generated across the thylakoid membrane produces a proton-motive force, which is utilized to synthesize ATP by the use of ATP synthase. NADPH is used as a hydride source in the Calvin–Benson cycle to produce sugars by photosynthesis. In addition to NADP+, PSI can reduce O2 by two electrons with two protons to produce hydrogen peroxide (H2O2), which can be used as a fuel in H2O2 fuel cells. This Minireview focuses on artificial photosynthetic systems to produce the products of natural photosynthesis, such as ATP, NAD(P)H and H2O2 from NAD+ and O2 with water using solar energy, respectively. ATP was produced by use of an artificial photosynthetic membrane, composed of a photosynthetic reaction center mimic that pumps protons into the interior of the liposome, where F-type ATP synthase was incorporated. Solar-driven catalytic water splitting produces hydrogen, which can reduce NAD+ to NADH with an iridium complex catalyst in a slightly alkaline solution at room temperature. H2O2 has been produced by the combination of four-electron oxidation of H2O with four protons to evolve O2 and two-electron/two-proton reduction of O2 under sun-light irradiation. H2O2 can also be produced by direct reaction of H2 and O2 by the combination of an iridium complex catalyst and flavin coenzyme.
Bibliographical noteFunding Information:
The authors acknowledge very much the contributions of their collaborators and co-workers cited in the listed references, and support by a SENTAN project (to S.F.) from Japan Science and Technology Agency (JST), JSPS KAKENHI (No. 16H02268 to S.F.), the NRF of Korea through CRI (NRF-2012R1A3A2048842 to W.N.), GRL (NRF-2010-00353 to W.N.), and Basic Science Research Program (2017R1D1A1B03029982 to Y.-M.L. and 2017R1D1A1B03032615 to S.F.).
. The authors acknowledge very much the contributions of their collaborators and co‐workers cited in the listed references, and support by a SENTAN project (to S.F.) from Japan Science and Technology Agency (JST), JSPS KAKENHI (No. 16H02268 to S.F.), the NRF of Korea through CRI (NRF‐2012R1A3A2048842 to W.N.), GRL (NRF‐2010‐00353 to W.N.), and Basic Science Research Program (2017R1D1A1B03029982 to Y.‐M.L. and 2017R1D1A1B03032615 to S.F.)
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- artificial photosynthesis
- hydrogen peroxide
- water oxidation