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Electric Field‐Assisted Photochemical Water Splitting Should Operate with 287 nm Light
Author(s) -
Bachler Vinzenz,
Gärtner Wolfgang
Publication year - 2016
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12578
Subject(s) - bathochromic shift , electric field , excited state , chemistry , photochemistry , atomic physics , excitation , ultraviolet , water splitting , water dimer , homolysis , ultraviolet light , field (mathematics) , molecule , radical , materials science , hydrogen bond , physics , optoelectronics , optics , fluorescence , biochemistry , organic chemistry , quantum mechanics , photocatalysis , mathematics , pure mathematics , catalysis
The major photoreaction of water is the homolytic splitting of one O–H bond starting from the 1 1 B 1 excited state ( λ max = 167 nm). This reaction produces H• and • OH radicals. The combination of two H• atoms leads to the potential energy carrier dihydrogen. However, the energy required to obtain the photoreactive 1 1 B 1 electronic state is about 7.4 eV , which cannot be effectively provided by solar radiation. The sun light spectrum on earth comprises the visible and ultraviolet region, but shows vanishing intensity near 7 eV (177.1 nm). This work provides theoretical evidence that the photoreactive 1 1 B 1 state of water can be shifted into the ultraviolet ( UV ‐B) light region (≈287 nm) by including explicitly an electric field in the calculations of the water absorption spectrum. To accomplish such bathochromic shift, a large field strength of 3.08 VÅ −1 is required. The field‐dependent excitation energies were calculated by applying the symmetry‐adapted cluster configuration interaction ( SAC ‐ CI ) procedure. Based on this theoretical analysis, we propose that photochemical water splitting can be accomplished by means of 287 nm light provided the water molecule is favorably oriented by an external electric field and is subsequently activated by a reversal of the field orientation.