One Electron‐Initiated Two‐Electron Oxidation of Water by Aluminum Porphyrins with Earth's Most Abundant Metal. Issue 9 (10th April 2017)

• Record Type: Journal Article
• Authors: Kuttassery, Fazalurahman; Mathew, Siby; Sagawa, Shogo; Remello, Sebastian Nybin; Thomas, Arun; Yamamoto, Daisuke; Onuki, Satomi; Nabetani, Yu; Tachibana, Hiroshi; Inoue, Haruo
• Is Part Of: ChemSusChem. Volume 10:Issue 9(2017)
• Page Start: 1909
• Page End: 1915
• Publication Date: 2017-04-10
• Subjects: aluminum porphyrins -- artificial photosynthesis -- hydrogen peroxide -- molecular catalysts -- water splitting; Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.201700322
• Languages: English
• ISSNs: 1864-5631

Abstract

Abstract: We report herein a new molecular catalyst for efficient water splitting, aluminum porphyrins (tetra‐methylpyridiniumylporphyrinatealuminum: AlTMPyP), containing earth's most abundant metal as the central ion. One‐electron oxidation of the aluminum porphyrin initiates the two‐electron oxidation of water to form hydrogen peroxide as the primary reaction product with the lowest known overpotential (97 mV). The aluminum‐peroxo complex was detected by a cold‐spray ionization mass‐spectrometry in high‐resolution MS (HRMS) mode and the structure of the intermediate species was further confirmed using laser Raman spectroscopy, indicating the hydroperoxy complex of AlTMPyP to be the key intermediate in the reaction. The two‐electron oxidation of water to form hydrogen peroxide was essentially quantitative, with a Faradaic efficiency of 99 %. The catalytic reaction was found to be highly efficient, with a turnover frequency up to ∼2×10 4 s −1 . A reaction mechanism is proposed involving oxygen–oxygen bond formation by the attack of a hydroxide ion on the oxyl‐radical‐like axial ligand oxygen atom in the one‐electron‐oxidized form of AlTMPyP(O − )2, followed by a second electron transfer to the electrode. Abstract : From Earth's crust : A new class of molecular catalysts for efficient water splitting, aluminum porphyrins, containing the Earth's most abundant metal as their central ion. One‐electron oxidation of an aluminum porphyrin initiates the two‐electron oxidation of water to form hydrogen peroxide as the primary reaction product with the lowest known overpotential (97 mV) and a turnover frequency up to ∼2×10 4 s −1 .