Photoinduced Electron Transfer in Platinum(II) Terpyridyl Acetylide Chromophores:  Reductive and Oxidative Quenching and Hydrogen Production

Abstract

A series of luminescent platinum(II) terpyridyl acetylide complexes, ([Pt(tpy)(CCPh)]ClO4 (1) and [Pt(ttpy)(CC-p-C6H4R)]ClO4, where tpy=terpyridine, ttpy=4'-p-tolylterpyridine, R=H, Cl, Me) (2-4) were studied with regard to excited-state quenching by dialkylated bipyridinium cations as electron acceptors and triethanolamine (TEOA) as an electron donor and the photogeneration of hydrogen from systems containing the chromophore, the dialkylated bipyridinium cations, TEOA, and colloidal Pt as a catalyst. The dialkylated bipyridinium cations include methyl viologen (MV2+) and a series of diquats prepared from 2,2'-bipyridine or 4,4'-dimethyl-2,2'-bipyridine. The quenching rates for the diquats for one of the chromophores (2) are close to the diffusion-controlled limit. The most effective electron acceptor and relay for hydrogen evolution has been found to be 4,4'-dimethyl-1,1'-trimethylene-2,2'-bipyridinium (DQ4) which on photoreduction by the chromohore provides the strongest reducing agent of the diquats studied. The rate of hydrogen evolution depends in a complex way on the concentration of the bipyridinium electron relay, increasing with concentration at low concentrations and then decreasing at high concentrations. The rate of H2 photogeneration also increases with TEOA concentration at low values and eventually reaches a plateau. The most effective system examined to date consists of the chromophore 2 (2.2x10(-5) M), DQ4 (3.1x10(-4) M), TEOA (2.7x10(-2) M), and Pt colloid (6.0x10(-5) M), and has produced 800 turnovers of H2 (67% yield based on TEOA as sacrificial electron donor) after 20 h of photolysis with lambda>410 nm.

A cobalt-based polyoxometalate catalyst for efficient visible-light-driven H2 evolution from water splitting

“…A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 6 Crystal data of sample CoPW 9 has been analyzed by the single-crystal X-ray diffraction. The crystal data of sample CoPW 9 (see Table S1) conform to those of Moreover, Figure S2 shows the UV-vis absorption spectrum of sample CoPW 9 in water.…”

“…Previous studies on the homogeneous systems for light-driven hydrogen production have shown high catalytic activities [3][4][5][6]. These systems typically consist of a catalyst, photosensitizer, and sacrificial electron donor.…”

“…Grätzel and co-worhers have reported the photocatalytic H 2 evolution systems using colloidal platinum as the catalyst, together with Ru(2, 2'-bipyridine) 3 2+ as the photosensitizer and EDTA as the sacrificial electron donor [3,4]. Related systems for the photocatalytic generation of H 2 based on platinum catalysts have been also developed by Du and Eisenberg, in combination with a platinum chromophore and triethanolamine as the sacrificial electron donor [5,6]. For real wide-spread application, catalysts made from elementally abundant and less expensive materials are urgently required.…”

PENGARUH UDARA TERHADAP FOTOLISIS AIR OLEH SERBUK TiO2 DENGAN ADANYA KALIUM IODIDA

“…Apabila reaksi ini berlangsung sempurna maka diduga jumlah ion OH -semakin meningkat dan pH larutan akan naik, sedangkan gas yang diperoleh semakin murni yaitu gas H2. Panguapan gas iodin dapat dicegah dengan penambahan KI dengan konsentrasi yang tidak terlalu encer [11,12,13] .…”

Bio-Inspired H2 Production Catalysts

“…The conversion of protons to H 2 requires a catalyst and currently two best available options are: (1) Platinum (Pt) based materials and (2) the natural enzyme hydrogenases. Both these systems can efficiently catalyze the reaction and can be utilized solar energy driven H 2 production [5,6]. However, both of them have their shortcomings that have limited their usage for worldwide solar H 2 production.…”