Photochemical splitting of water into H2 and O2 using solar energy is a process of great economic and environmental interest. Since the discovery of the first water splitting system based on TiO2 and Pt in 1972 by Fujishima and Honda, over 130 inorganic materials have been discovered as catalysts for this reaction. This review discusses the known inorganic catalysts with a focus on structure–activity relationships.

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Inorganic Materials as Catalysts for Photochemical Splitting of Water

In view of the diminishing oil resources and the ongoing climate change, the use of efficient and environmentally benign technologies for the utilization of renewable resources has become indispensible. Therein, hydrogenolysis reactions offer a promising possibility for future biorefinery concepts. These reactions result in the cleavage of C-C and C-O bonds by hydrogen and allow direct access to valuable platform chemicals already integrated in today's value chains. Thus, hydrogenolysis bears the potential to bridge currently available technologies and future biomass-based refinery concepts. This Review highlights past and present developments in this field, with special emphasis on the direct utilization of cellulosic feedstocks.

Hydrogenolysis Goes Bio: From Carbohydrates and Sugar Alcohols to Platform Chemicals

In this review, for a variety of metals and semiconductors, an attempt is made to generalize observations in the literature on the effect of process conditions applied during photodeposition on (i) particle size distributions, (ii) oxidation states of the metals obtained, and (iii) consequences for photocatalytic activities. Process parameters include presence or absence of (organic) sacrificial agents, applied pH, presence or absence of an air/inert atmosphere, metal precursor type and concentration, and temperature. Most intensively reviewed are studies concerning (i) TiO2; (ii) ZnO, focusing on Ag deposition; (iii) WO3, with a strong emphasis on the photodeposition of Pt; and (iv) CdS, again with a focus on deposition of Pt. Furthermore, a detailed overview is given of achievements in structure-directed photodeposition, which could ultimately be employed to obtain highly effective photocatalytic materials. Finally, we provide suggestions for improvements in description of the photodeposition methods applied when included in scientific papers.

Methods, Mechanism, and Applications of Photodeposition in Photocatalysis: A Review.

Although the use of CO as a reductant had been in the past confined to few reactions, its use in organic synthesis, especially in the reductive carbonylation of nitro aromatics and the oxidative carbonylation of aromatic amines, has increased dramatically. Since the discovery of CO-induced reduction of nitro groups, there has been a wide spread increase of interest in the application and mechanistic understanding of this reaction. In a major review published in 1988 it was noted, that in practice no studies of the mechanism of N-carbonylation of aromatic nitro compounds with alcohols leading to carbamates have been carried out. This review clearly shows a major change since that publication. Indeed, metal-catalyzed reductive carbonylation of nitro aromatics using CO as reducing agent has been in the past 10 years the subject of intense investigation both in academia and in the chemical industry. Several articles and reviews have covered the subject up to the late 1980s. The authors will concentrate on more recent literature, but sometimes older data will be used to establish an understanding of these reactions. 127 refs.

A Review of the Selective Catalytic Reduction of Aromatic Nitro Compounds into Aromatic Amines, Isocyanates, Carbamates, and Ureas Using CO.

Nitrogen dioxide and carbonate radical anion: two emerging radicals in biology.

Deactivation of RuCl2(PPh3)3 during disproportionation of D-glucose in amide solvents

The mechanism of disproportionation of D-glucose catalysed by hydridochlorocarbonyltris(triphenyl-phosphine)ruthenium(II) in tetrahydrofurfuryl alcohol

Flash photolysis of an aqueous solution of sodium metaborate and potassium peroxydisulphate at pH 115 gives rise to a new transient species with an absorption maxima at 590 nm (Iµ= 80 m2 mol–1) and 650 nm (Iµ= 90 m2 mol–1) The laser-Raman and 11B nmr spectra of metaborate solutions at pH 115 are consistent with the presence of the tetrahydroxyborate ion, B(OH)–4 The pKa and reduction potential of the radical B(OH)˙4, produced on flashing a mixture of B(OH)–4 and S2O2–8 are found to be 1075 ± 002 and + 14 V, respectively The rate constants for the oxidation of several amines and phenols by this one-electron oxidant have been determined Salt-effect studies are consistent with the reactive species being B(OH)3O˙–

Redox and acidic properties of the borate radical B(OH)˙4. A flash photolysis study

Spectral evidence for the formation of active intermediates from RuCl3 and RuCl2(PPh3)3 with N-methylmorpholine N-oxide (NMO) and phenyliodosoacetate (PIA) as mild oxidants

The induction period observed in the cis-RuCl 2 (DMSO) 4 catalyzed oxidation of thioethers (S) to sulfoxides by N-methylmorpholine N-oxide (NMO) is attributed to the rate of formation of the active species viz. RuCl 2 (DMSO) 3 S. Cyclic voltammetric studies indicate formation of the Ru IV =0 species. Based on the variable orders in NMO and first order in each of the other reactants, a mechanism is proposed where the active species generated in situ reacts with NMO in a slow step to form Ru IV oxo complex which then decomposes to give the product

J. C. Kuriacose

Papers

Deactivation of RuCl2(PPh3)3 during disproportionation of D-glucose in amide solvents

The mechanism of disproportionation of D-glucose catalysed by hydridochlorocarbonyltris(triphenyl-phosphine)ruthenium(II) in tetrahydrofurfuryl alcohol

Redox and acidic properties of the borate radical B(OH)˙4. A flash photolysis study

Spectral evidence for the formation of active intermediates from RuCl3 and RuCl2(PPh3)3 with N-methylmorpholine N-oxide (NMO) and phenyliodosoacetate (PIA) as mild oxidants

cis‐RuCl2(DMSO)4‐catalyzed oxidation of sulfides by N‐methylmorpholine N‐oxide (NMO)