title: DFT characterization on the mechanism of water splitting catalyzed by single-Ru-substituted polyoxometalates.
abstract: Water oxidation is a key half reaction in the energy conversion scheme. The reaction mechanism for the oxidation of H2O to O2 catalyzed by single-Ru-substituted polyoxometalates, [Ru(III)(H2O)XW11O39](n-) (X = Si(IV), Ge(IV)), was investigated by means of density functional calculations. The electronic structure of the pre-activation intermediates indicates that the aqua ligand is prone to accommodate the proton coupled electron transfer (PCET) process to achieve the active group [Ru(V)=Oa], and the high valent oxo-ruthenium(V) species are responsible for the O-O forming event. Three possible proton acceptors were designed for the rate-determining step (Ob, Oa, and H2O), the calculated results support that the bridge Ob atom of the polytungstate ligand will act as the most favorable proton acceptor in the O-O bond formation, with an energy barrier of 28.43 kcal mol(-1). A detailed information of the peroxidic intermediates in the oxidation process was also characterized, both the peroxo-species [Ru(IV)(OO)SiW11O39](6-) and [Ru(V)(OO)SiW11O39](5-) show the six-coordinate isomer with an open terminal geometry is more favorable than the close seven-coordinate ones. In addition, the replacement of the heteroatom in XO4(n-) can effectively tune the catalytic activity of polyoxometalates, in the order of Ge(IV) > Si(IV).
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, PR China.
authors.forename: Zhong-Ling
authors.initials: ZL
authors.lastname: Lang
authors.forename: Guo-Chun
authors.initials: GC
authors.lastname: Yang
authors.forename: Na-Na
authors.initials: NN
authors.lastname: Ma
authors.forename: Shi-Zheng
authors.initials: SZ
authors.lastname: Wen
authors.forename: Li-Kai
authors.initials: LK
authors.lastname: Yan
authors.forename: Wei
authors.initials: W
authors.lastname: Guan
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Su