title: Water Will Be the Coal of the Future-The Untamed Dream of Jules Verne for a Solar Fuel.
abstract: This article evokes the futuristic visions of two giants, one a writer,Jules Verne, who foresaw water as the coal of the future, and the other a scientist,Giacomo Ciamician, who foresaw the utilization of solar energy as an energy source with which to drive photochemical and photocatalytic reactions for the betterment of mankind. Specifically, we examine briefly the early work of the 1960s and 1970s on the photosplitting of free water and water adsorbed on solid supports, based mostly on metal oxides, from which both hydrogen and oxygen evolve in the expected stoichiometric ratio of 2 to 1. The two oil crises of the 1970s (1973 and 1979) spurred the interest of researchers from various disciplines (photochemistry, photo-catalysis and photoelectrochemistry) in search of aHoly Grailphotocatalyst, process, or strategy to achieve efficient water splitting so as to provide an energy source alternative to fossil fuels. Some approaches to the photosplitting of water adsorbed on solid insulators (high bandgap materials; Ebg≥ 5 eV) and semiconductor photocatalysts (metal oxides) are described from which we deduce that metal oxides with bandgap energies around 5 eV (e.g., ZrO₂) are more promising materials to achieve significant water splitting on the basis of quantum yields than narrower bandgap photocatalysts (e.g., TiO₂; Ebg≈ 3.0-3.2 eV), which tend to be relatively inactive by comparison. Although proof of concept of the photosplitting of water has been demonstrated repeatedly in the last four decades, much remains to be done to findthe Holy Grailphotocatalyst and/or strategy to achieve significant yields of hydrogen.
authors.affiliation: Faculty of Physics, Saint-Petersburg State University, Ulyanovskaya Str. 1, Petergof, Saint-Petersburg 198504, Russia. v.ryabchuk@spbu.ru.
authors.forename: Vladimir K
authors.initials: VK
authors.lastname: Ryabchuk
authors.affiliation: Faculty of Physics, Saint-Petersburg State University, Ulyanovskaya Str. 1, Petergof, Saint-Petersburg 198504, Russia. vn.kuznetsov@spbu.ru.
authors.forename: Vyacheslav N
authors.initials: VN
authors.lastname: Kuznetsov
authors.affiliation: Faculty of Physics, Saint-Petersburg State University, Ulyanovskaya Str. 1, Petergof, Saint-Petersburg 198504, Russia. alexei.emeline@spbu.ru.|Laboratory of Photoactive Nanocomposite Materials, Saint-Petersburg State University, Ulyanovskaya Str. 1, Petergof, Saint-Petersburg 198504, Russia. alexei.emeline@spbu.ru.
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Emeline
authors.affiliation: Laboratory of Photoactive Nanocomposite Materials, Saint-Petersburg State University, Ulyanovskaya Str. 1, Petergof, Saint-Petersburg 198504, Russia. yurii54@yandex.ru.
authors.forename: Yurii M
authors.initials: YM
authors.lastname: Artem'ev
authors.affiliation: Moscow Engineering Physics Institute, National Research Nuclear University MEPhI, Kashirskoe highway, 31, Moscow 115409, Russia. gvkatayeva@mephi.ru.
authors.forename: Galina V
authors.initials: GV
authors.lastname: Kataeva
authors.affiliation: Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyodaku, Tokyo 102-8554, Japan. horikosi@sophia.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Horikoshi
authors.affiliation: PhotoGreen Laboratory, Dipartimento di Chimica, Universita di Pavia, Via Taramelli 12, Pavia 27100, Italy. nick.serpone@unipv.it.
authors.forename: Nick
authors.initials: N
authors.lastname: Serpone
mesh_terms: D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D055668:Photochemical Processes; D012993:Solar Energy; D014867:Water / Q000737:chemistry*
chemical_list: D008670:Metals; D014867:Water; D006859:Hydrogen; D010100:Oxygen
keywords: alkali halides; hydrogen evolution; metal oxides; photosplitting of adsorbed water; solid supports