M.V.C. Sastri

Photocatalytic hydrogen production by dye-sensitized Pt/SnO2 AND Pt/SnO2/RuO2 in aqueous methyl viologen solution

Abstract Hydrogen photoproduction by a rarely studied, wide band gap semiconductor, SnO2, in powder form loaded with Pt and RuO2 and sensitized by Ru(bpy)32+ and organic dyes or with low band gap semiconductor, CdS, was investigated. Acriflavin, Eosin Blue, Rhodamine B, Rose Bengal and Fluorescein were used as photosensitizers in the presence of methyl viologen and with or without a sacrificial agent, EDTA. The effects of variation in concentrations of Ru(bpy)32+ and MV2+ were studied. The maximum rate of hydrogen production was observed at [Ru(bpy)32+] = 3.75 × 10−5 mol dm−3 and [MV2+] = 2.5 × 10−5 mol dm−3. The efficiency of the sensitizers in hydrogen production was found to decrease in the order: Eosin Blue > Rose Bengal > Ru(bpy)32+ > rhodamine B = acriflavin > fluorescein.

Hydrogen evolution from water with visible radiation in presence of Cu(II)/WO3 and electron relay

Cu(II)-doped WO3 particles in presence of methylviologen and visible radiation are found to evolve hydrogen from water more efficiently. Methylviologen has been used as an electron relay for the transfer of conduction band electron of the semiconductor to the hydrogen ion present in the aqueous solution. Increase in the molar percentage of Cu(II) ions is found to increase the hydrogen evolution rate.

Hydrogen energy research and development in India—an overview

Abstract India is trying hard to improve the standard of living of its peoples, and therefore increase the energy consumption. Amongst the many options. India is also researching the various aspects of the hydrogen energy system. This paper presents an overview of hydrogen energy research and development work in India, starting with a summary of the energy situation in the country.

Photobiocatalysis: hydrogen evolution using a semiconductor coupled with photosynthetic bacteria

Abstract Photobiocatalytic production of hydrogen in the presence of Bi2O3 semiconductor, methyl viologen (MV2+) as an electron mediator and three different bacteria (Rhodopseudomonas capsulata, Rhodospirillum rubrum and Escherichia coli) as hydrogen evolution enzyme catalysts has been carried out in different environments. Addition of intact bacterial cells is found to increase the hydrogen production efficiency. It has been suggested that the nitrogenase enzymes of the bacterial cells catalyze the hydrogen evolution process rather than the hydrogenase enzymes of the bacteria. The presence of carbohydrates (fructose, dextrose and starch) and organic acids (oxalic acid, EDTA and ascorbic acid) as electron donors with the above system further enhances the hydrogen production efficiency due to the reaction of photogenerated valence band holes of the semiconductor with these substrates, thereby preventing the e−-h+ recombination. The effects of loading the semiconductor with RuO2 and Rh2O3 and addition of divalent metal ions, Ca2+, Mg2+ and Mn2+ to the system towards hydrogen production efficiency were also studied and discussed.

Visible light-induced hydrogen production from water with Pt/Bi2O3/RuO2 in presence of electron relay and photosensitizer

Abstract An attempt is made to prepare Pt/Bi 2 O 3 /RuO 2 (PhC) catalyst and to use it for photocatalytic production of hydrogen from water in the presence of: (i) methyl viologen (MV 2+ ) as an electron relay, (ii) Ru(bpy) 3 2+ as a photosensitizer, or (iii) both (i) and (ii) with visible light of λ ⩾ 400 nm. Compared to the undoped γ-Bi 2 O 3 , the above catalyst is more efficient in hydrogen production. The efficiencies of the different systems constituted by the catalyst with MV 2+ or Ru(bbpy) 3 2+ or both, in hydrogen production are in the order PhC  MV 2+ PhC  Ru ( bpy ) 2+ 3 PhC  MV 2+  Ru ( bpy ) 2+ 3 . Suitable explanations and plausible mechanisms and schemes have been provided to account for the observations in each category of the experiment.

India's hydrogen energy program—A status report

Hydrogen energy research in India started in 1976 on the initiative of the Government of India and covers almost all areas of technical relevance to the deployment of hydrogen as an energy vector. Specifically, these include its production from water by electrolysis, photoelectrolysis, photo-catalysis and biophotolysis, its storage as liquid hydrogen and metal hydrides, its consumptive use as engine fuel and thermal fuel and nonconsumptive application in metal hydrides-based chemical heat pumps. All this research is sponsored and supported by the Government of India. The genesis of hydrogen energy research in India and its growth during the first 10 years have already been reviewed at the VI-WHEC (Vienna, 1986). The present review is an update of the previous report

Visible light induced hydrogen production with Cu(II)/Bi2O3 and Pt/Bi2O3/RuO2 from aqueous methyl viologen solution

Abstract γ-Bi 2 O 3 , a rarely studied oxide semiconductor, was doped individually with Cu(II) in different concentrations, Pt and RuO 2 (0.5 wt%) and used as a fine powder for photocatalytic production of hydrogen from water in the presence of methyl viologen (MV 2+ ) as an electron relay. The diffuse absorption spectroscopy of the samples revealed that the doping process improved the absorption of γ-Bi 2 O 3 in the visible region while the XRD spectra indicated no change in crystal structure, but an enhancement in crystallinity. For 90 min irradiation ( λ ≥ 400 nm) of the aqueous slurry of the catalyst in presence of MV 2+ , 0.79 and 0.66 ml of hydrogen were generated by 4 at% Cu(II)/Bi 2 O 3 and Pt/Bi 2 O 3 /RuO 2 respectively. A suitable mechanism involving the reactions of photogenerated e − and h + has been proposed for the photodecomposition of water. The effects of dopant concentration and the catalyst amount on hydrogen production have also been explained.