Quantitative electrochemical kinetics studies of "microelectrodes": catalytic water reduction by methyl viologen/colloidal platinum

Near‐Infrared Light‐Driven Hydrogen Evolution from Water Using a Polypyridyl Triruthenium Photosensitizer

“…[2] Scheme 1illustrates two types of photochemical H 2 -evolving systems consisting of aD(e.g., ascorbate,e thylenediaminetetracetic acid), aP S( e.g.,[ Ru(bpy) 3 ] 2+ , [3] [Ir-(bpy)(ppy) 2 ] + , [4] with bpy = 2,2'-bipyridine and ppy = 2-phenylpyridinate), and acatalyst (e.g., colloidal Pt, [5] Pt II , [6] Rh II [7] and Co II [8] complexes). As shown in Scheme 1, either an oxidative or reductive quenching process triggers the lightdriven electron transfer (ET) processes.I ns pite of the great advancement so far in this area, little efforts have been made to develop PSs capable of driving ET events by making use of awider wavelength range of the solar spectrum.…”

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In order to realizea rtificial photosynthetic devices for splitting water to H 2 and O 2 (2 H 2 O + hn!2H 2 + O 2 ), it is desirable to use awider wavelength range of light that extends to alower energy region of the solar spectrum. Here we report at riruthenium photosensitizer [Ru 3 (dmbpy) 6 (m-HAT)] 6+ (dmbpy = 4,H AT = 1,4,5,8,9,12hexaazatriphenylene), whicha bsorbs near-infrared light up to 800 nm based on its metal-to-ligand charge transfer ( 1 MLCT) transition. Importantly,[ Ru 3 (dmbpy) 6 (m-HAT)] 6+ is found to be the first example of ap hotosensitizer which can drive H 2 evolution under the illumination of near-infrared light above 700 nm.

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“…The electrochemical and photochemical studies reveal that the reductive quenching within the ion-pair adducts of [Ru 3 (dmbpy) 6 (m-HAT)] 6+ and ascorbate anions affords as ingly reduced form of [Ru 3 (dmbpy) 6 (m-HAT)] 6+ , which is used as areducing equivalent in the subsequent water reduction process.Among various recent attempts to fabricate artificial photosynthesis generating hydrogen energy from water and sunlight, [1] molecular systems consisting of as acrificial electron donor (D), aphotosensitizer (PS), an electron relay (A), and aH 2 -evolving catalyst (Cat) have been extensively investigated. [2] Scheme 1illustrates two types of photochemical H 2 -evolving systems consisting of aD(e.g., ascorbate,e thylenediaminetetracetic acid), aP S( e.g.,[ Ru(bpy) 3 ] 2+ , [3] [Ir-(bpy)(ppy) 2 ] + , [4] with bpy = 2,2'-bipyridine and ppy = 2-phenylpyridinate), and acatalyst (e.g., colloidal Pt, [5] Pt II , [6] Rh II [7] and Co II [8] complexes). As shown in Scheme 1, either an oxidative or reductive quenching process triggers the lightdriven electron transfer (ET) processes.I ns pite of the great advancement so far in this area, little efforts have been made to develop PSs capable of driving ET events by making use of awider wavelength range of the solar spectrum.…”

Enhancement of neutralization reaction in colloidal ferric hydrous oxide

“…Refs. (3,4)-and recently with colloidal oxide semiconductors"s6' such as TiOz and a-FezOJ dispersions. The suspected advantage inherent in the small particle size, besides their enormous surface, is the possibility of avoiding recombination of light generated electrons and holes before these reach the surface.…”

Redox Electrocatalysis of Floating Nanoparticles: Determining Electrocatalytic Properties without the Influence of Solid Supports

“…22,28 Examples of redox electrocatalysis date back to the pioneering works of the groups of Henglein, Miesel, Grätzel, Bard and others in late 1970s. Their works involved generating organic and inorganic free-radicals in de-aerated aqueous solutions to charge and discharge colloidal metallic NPs predominantly of Pt, [29][30][31][32][33] Ag 28,[34][35][36] and Au. [37][38][39] Free-radicals may be generated radiolytically via exposure of a mixture of 2-propanol and acetone to γ-irradiation from a 60 Co source 34 or with UV-light.…”