Artificial Photosynthesis Sensitized by Metal Complexes : Utilization of a Ubiquitous Element (特集 光触媒を利用した人工光合成研究の最新動向)

Content Provider	Semantic Scholar
Author	Kuttassery, Fazalurahman Mathew, Siby Yamamoto, Daisuke
Copyright Year	2014
Abstract	Artificial photosynthesis is recognized as one of the most probable candidates to provide a realistic system from the viewpoint of renewable energy along with a well-balanced circulation of elements on the earth.1,2 In the discussion on what sort of strategic approaches we could take, however, there might be unexpected confusion about the definition of artificial photosynthesis. Artificial photosynthesis tends to be considered to be an exact mimic of natural photosynthesis, where carbohydrates and oxygen are produced from water and carbon dioxide upon visible light irradiation, since the term “artificial” usually implies making things that already exist in nature. The definition, however, may be too strict and somewhat misleading from a scientific viewpoint. Recent intensive studies on photoredox reactions and catalytic reactions that can be coupled with water oxidation processes strongly suggest that more a general concept should be defined for artificial photosynthesis from the viewpoints of both renewable energy and well-balanced circulation of elements on the earth. Artificial photosynthesis thus should be scientifically defined as a fundamental science and technology that 1) can induce an uphill reaction that leads to energy accumulation as a result of a particular reaction, 2) uses water as the electron donor and the source material, and 3) uses sunlight irradiation. These three factors are indispensable for the definition of artificial photosynthesis. The reaction products should not be limited to reduced forms of carbon dioxide nor oxygen as the oxidized form of water, but include other energystoring materials, such as hydrogen and even ammonia as the reduced products. Hydrogen peroxide and other oxygenated substrates can also be products at the oxidation terminus. The term “solar fuels” expresses more properly the preferable meaning of the reaction products of artificial photosynthesis.1,2 Among various candidates for solving the global energy problem, solar energy is undoubtedly the most probable candidate, leading to a sustainable society with a sound, reasonable source of renewable energy.1,2 The amount of solar energy captured on the globe is nearly 10,000 times larger than the current energy consumption by mankind. On the other hand, the energy density acquired per unit area is rather small (3100mWcm12), with the intensity fluctuating depending upon geographical location, season, time of day, and weather. Utilizing solar energy with such a rarefied intensity and instability should require a sound, strategic decision on whether or not we take an approach to directly go through this obvious barrier or to bypass it, in addition to the simple harvesting and storage of light energy. In this article, the key points in realizing artificial photosynthesis are overviewed. An alternative approach of one-photon-induced two-electron activation of water sensitized by metalloporphyrins to bypass the problem of the low photon flux density of sunlight is postulated. The possibility of utilizing metalloporphyrins with the most easily available element aluminum will be also discussed. Aluminum(III)tetra(4-carboxyphenyl)porphyrin (Al(III)TCPP) was synthesized and its fundamental chemical behavior, including a protolytic reaction of the axial ligands, has been characterized.
Starting Page	475
Ending Page	485
Page Count	11
File Format	PDF HTM / HTML
DOI	10.5796/electrochemistry.82.475
Volume Number	82
Alternate Webpage(s)	https://www.jstage.jst.go.jp/article/electrochemistry/82/6/82_14-6-FE0044/_pdf/-char/en
Alternate Webpage(s)	https://doi.org/10.5796/electrochemistry.82.475
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article