Rajesh V. Shende

H2 generation from two-step thermochemical water-splitting reaction using sol-gel derived SnxFeyOz

H2 has a great potential to replace fossil fuels and contribute to clean energy by reducing the environmental carbon foot-print. This study reports H2 generation from a thermochemical water-splitting reaction using sol-gel derived SnxFeyOz powders. The sol-gel synthesis involved the addition of SnCl2u2009·u20092H2O and FeCl2u2009·u20094H2O in ethanol followed by gelation using propylene oxide. As-synthesized gels were aged, dried, and heated rapidly upto different temperatures and quenched in air or N2 environment. The calcined powders were characterized using powder x-ray diffraction, BET surface area analyzer, and scanning electron microscopy (SEM). Calcination temperature and environment were found to have a significant effect on phase composition and specific surface area (SSA). The calcined SnxFeyOz powders were placed in a tubular Inconel reactor and four consecutive thermochemical cycles were performed. Water-splitting and regeneration steps were carried out at 900u2009°C and 1100u2009°C, respectively. The powder calcined...

Mesoporous coupled ZnO/TiO2 photocatalyst nanocomposites for hydrogen generation

The present work investigates mesoporous coupled ZnO-TiO2 based nanocomposites towards photocatalytic hydrogen generation. The effect of Zn2+ loadings was examined on the photocatalytic activities of the sol-gel derived ZnO-TiO2 nanocomposites employing a structure-directing template. ZnO-TiO2 nanocomposites were characterized by powder X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, nitrogen isotherm, Raman, and electrochemical impedance spectroscopy (EIS) methods. The photocatalytic H2 evolution of the ZnO-TiO2 suspensions was evaluated in an aqueous methanol medium under UV illumination. The Zn2+ concentrations utilized to prepare ZnO-TiO2 nanocomposites were found to have significant effect on the specific surface area, pore volume, and photocatalytic activity. The H2 evolution results obtained with ZnO-TiO2 nanocomposites were compared with H2 generation using commercial TiO2 P25 and individual ZnO nanoparticles. The photocatalytic activity of ZnO-TiO2 co...

H2 generation from thermochemical water-splitting using yttria stabilized NiFe2O4 core-shell nanoparticles

This investigation reports synthesis of core-shell NiFe2O4/Y2O3 nanoparticles by sol-gel technique and their H2 volume generation ability via thermochemical water-splitting reaction at 900u2009°C–1100u2009°C. Thermochemical water-splitting process involves a cyclic operation of a low-temperature water-splitting step and relatively high temperature regeneration step using redox materials. Because of the cyclic nature of the process, the redox materials undergo thermal fatigue leading to grain growth or sintering, consequently, steady H2 production is not realized in multiple thermochemical cycles. In this study, attempts were made to achieve steady H2 volume generation in multiple thermochemical cycles using core-shell nanoparticles, which were synthesized using precursors such as NiCl2, FeCl2, and YCl3, and pluronic P123 surfactant template. H2 volume generated by NiFe2O4/Y2O3 core-shell nanoparticles was found to be relatively stable over multiple thermochemical cycles. Contrasting to this, the H2 volume generat...

The toxicity of lead to Desulfovibrio desulfuricans G20 in the presence of goethite and quartz

An aqueous mixture of goethite, quartz, and lead chloride (PbCl2) was treated with the sulfate‐reducing bacterium, Desulfovibrio desulfuricans G20 (D. desulfuricans G20), in a medium specifically designed to assess metal toxicity. In the presence of 26 μM of soluble Pb, together with the goethite and quartz, D. desulfuricans G20 grew after a lag time of 5 days compared to 2 days in Pb‐, goethite‐, and quartz‐free treatments. In the absence of goethite and quartz, however, with 26 μM soluble Pb, no measurable growth was observed. Results showed that D. desulfuricans G20 first removed Pb from solutions then growth began resulting in black precipitates of Pb and iron sulfides. Transmission electron microscopic analyses of thin sections of D. desulfuricans G20 treated with 10 μM PbCl2 in goethite‐ and quartz‐free treatment showed the presence of a dense deposit of lead sulfide precipitates both in the periplasm and cytoplasm. However, thin sections of D. desulfuricans G20 treated with goethite, quartz, and PbCl2 (26 μM soluble Pb) showed the presence of a dense deposit of iron sulfide precipitates both in the periplasm and cytoplasm. Energy‐dispersive X‐ray spectroscopy, selected area electron diffraction patterns, or X‐ray diffraction analyses confirmed the structure of precipitated Pb inside the cell as galena (PbS) in goethite‐ and quartz‐free treatments, and iron sulfides in treatments with goethite, quartz, and PbCl2. Overall results suggest that even at the same soluble Pb concentration (26 μM), in the presence of goethite and quartz, apparent Pb toxicity to D. desulfuricans G20 decreased significantly. Further, accumulation of lead/iron sulfides inside D. desulfuricans G20 cells depended on the presence of goethite and quartz. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermodynamic Analysis of Solar Fuel Production via Thermochemical H2O and/or CO2 Splitting Using Tin Oxide Based Redox Reactions

Thermodynamic analysis of the production of solar syngas (a mixture of H 2 and CO with molar ratio equal to 2:1) via SnO 2 /SnO based thermochemical H 2 O and/or CO 2 splitting redox reactions was investigated and presented. Commercially available HSC Chemistry software and databases were used for the thermodynamic modeling of this process. Thermodynamic analysis was performed in two sections, namely, a) equilibrium thermodynamic calculations, and b) second law thermodynamic modeling of the SnO 2 /SnO based thermochemical H 2 O and/or CO 2 splitting process. Results obtained via the computation thermodynamic modeling are presented.