Sol-gel synthesis of nanocrystalline Ni-ferrite and Co-ferrite redox materials for the rmoche mical production of solar fuels

In this contribution, we report the synthesis and characterization of NixFe3-xO4 and CoxFe3-xO4 redox nanomaterials using sol-gel method. These materials will be used to produce solar fuels such as H2 or syngas from H2O and/or CO2 via solar thermochemical cycles (STCs). For the sol-gel synthesis of ferrites, the Ni, Co, Fe precursor salts were dissolved in ethanol and propylene oxide (PO) was added dropwise to the well mixed solution as a gelation agent to achieve gel formation. Freshly synthesized gels were aged, dried, and calcined by heating them to 600°C in air. The calcined powders were characterized by powder x-ray diffractometer (XRD), BET surface area, as well as scanning (SEM) and transmission (TEM) electron microscopy. Their suitability to be used in STCs for the production of solar fuels was assessed by performing several reduction/re-oxidation cycles using a thermogravimetric analyzer (TGA).Scopu

Solar hydrogen production via thermochemical metal oxide - Metal sulfate water splitting cycle

This paper reports the thermodynamic analysis of solar H2 production via two-step thermochemical iron oxide - iron Sulfate (IO-IS) water splitting cycle. The first step belongs to the exothermic oxidation of FeO via SO2 and H2O producing FeSO4 and H2 and second step corresponds to the endothermic reduction of FeSO4 into FeO, SO2, and O2. The products, FeO and SO2 can be recycled to step 1 and hence, reutilized for the production of H2 via water splitting reaction. Thermodynamic equilibrium compositions of the thermal reduction and water splitting reactions were computed as a function of reaction temperatures. Second law thermodynamic analysis was performed to determine the absorption, Qsolar, Qreactor-net, Qre-radiation Qfeo-oxd and nycyle and nsolar respectively.Acknowledgments The authors gratefully acknowledge the financial support provided by the Qatar University Internal Grants QUUG-CENG-CHE-13/14-4 and QUUG-CENG-CHE-14\15-10.Scopu

Solar hydrogen production via thermochemical iron oxide-iron sulfate water splitting cycle

This paper reports the thermodynamic analysis of solar H2 production via two-step thermochemical iron oxide–iron sulfate (IO–IS) water splitting cycle. The first step belongs to the exothermic oxidation of FeO via SO2 and H2O producing FeSO4 and H2 and second step corresponds to the endothermic reduction of FeSO4 into FeO, SO2, and O2. The products, FeO and SO2 can be recycled to step 1 and hence, reutilized for the production of H2 via water splitting reaction. Thermodynamic equilibrium compositions and variations in enthalpy, entropy and Gibbs free energy of the thermal reduction and water splitting reactions were computed as a function of reaction temperatures. Furthermore, the effect of molar flow rate of inert Ar (n˙Ar) on thermal reduction temperature (TR) and equilibrium compositions during the thermal reduction of FeSO4 was also examined. Second law thermodynamic analysis was performed to determine the cycle efficiency (ηcycle) and solar to fuel energy conversion efficiency (ηsolar−to−fuel) attainable with and without heat recuperation for varying n˙Ar (0–30 mol/s) and TR (1280–1510 K). Results obtained indicate ηcycle = 39.56% and ηsolar−to−fuel = 47.74% (without heat recuperation) and ηcycle = 51.77% and ηsolar−to−fuel = 62.43% (by applying 50% heat recuperation) at TR = 1510 K.The authors gratefully acknowledge the financial support provided by the Qatar University internal grant QUUG-CENG-CHE-13/14-4 .Scopu

CO2 capture from fossil fuel power plant flue gas using aqueous solution of renewably prepared alkanolamine

In this study, K2CO3/KHCO3 as hydroxyl radical scavengers was mixed with aqueous EAE to form a new absorbing solvent i.e. EHRS solvent which will be used for the reactive absorption of CO2. Degradation of the EHRS solvent in presence of O2 (oxidative degradation) was examined by employing accelerated experimental conditions at 150°C. The physicochemical properties such as density, viscosity, and diffusivity and solubility of CO2 in EHRS solvent at various experimental conditions were estimated. Furthermore, kinetics of reactive absorption of CO2 in EHRS solvent was explored by using a stirred cell reactor using a fall in CO2 pressure technique.Scopu

CO2 capture from fossil fuel power plant flue gas using aqueous solution of renewably prepared alkanolamine

In this study, K2CO3/KHCO3 as hydroxyl radical scavengers was mixed with aqueous EAE to form a new absorbing solvent i.e. EHRS solvent which will be used for the reactive absorption of CO2. Degradation of the EHRS solvent in presence of O2 (oxidative degradation) was examined by employing accelerated experimental conditions at 150°C. The physicochemical properties such as density, viscosity, and diffusivity and solubility of CO2 in EHRS solvent at various experimental conditions were estimated. Furthermore, kinetics of reactive absorption of CO2 in EHRS solvent was explored by using a stirred cell reactor using a fall in CO2 pressure technique.Acknowledgments Authors wish to acknowledge the University Grants Commission (Government of India), Institute of Chemical Technology (ICT, Mumbai), and Qatar University for the support provided during the course of this study.Scopu

Thermochemical dissociation of CO2 into renewable fuels via CexZryHfzO2 based redox reactions using concentrated solar energy

In this paper we report the co-precipitation synthesis of Ce0.75Zr0.125Hf0.125O2 redox material for the production of solar fuels via thermochemical H2O/CO2 splitting reaction. For the synthesis of Ce0.75Zr0.125Hf0.125O2 via co-precipitation method, Ce, Zr, and Hf metal salts were dissolved in demineralized water and aqueous NH4OH was added until the precipitation was complete. After precipitation, the slurry was filtered and the solids obtained after filtration were dried, crushed, and subsequently heated in a muffle furnace in presence of air. Calcined powders obtained were further characterized using powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and BET surface area analyzer. Solar fuel production ability and thermal stability of the synthesized Ce0.75Zr0.125Hf0.125O2 redox material was investigated by performing multiple thermochemical oxidation and thermal reduction cycles in presence of CO2 and inert Ar using a thermogravimetric analyzer (TGA).Scopu

Solar thermochemical conversion of CO2 into synthetic fuels via ferrite based redox reactions

In this contribution, we report the synthesis NiFe2O4 and CoFe2O4 redox materials via sol-gel method. For the synthesis of these materials via sol-gel approach, the Ni, Co, and Fe precursors were first dissolved in ethanol with the help of sonic energy. Once the metal precursors were dissolved, propylene oxide (PO) was added dropwise to the well mixed solution as a gelation agent to achieve gel formation. As-prepared gels were aged, dried and subsequently calcined in presence air. The calcined powder obtained was characterized towards its phase/chemical composition, particle morphology, and specific surface area (SSA). Derived NiFe2O4 and CoFe2O4 redox materials were further investigated towards thermochemical splitting of CO2 into solar fuels by performing several reduction/re-oxidation cycles using a thermogravimetric analyzer (TGA).Scopu

Thermochemical dissociation of CO2 into renewable fuels via CexZryHfzO2 based redox reactions using concentrated solar energy

In this paper we report the co-precipitation synthesis of Ce0.75Zr0.125Hf0.125O2 redox material for the production of solar fuels via thermochemical H2O/CO2 splitting reaction. For the synthesis of Ce0.75Zr0.125Hf0.125O2 via co-precipitation method, Ce, Zr, and Hf metal salts were dissolved in demineralized water and aqueous NH4OH was added until the precipitation was complete. After precipitation, the slurry was filtered and the solids obtained after filtration were dried, crushed, and subsequently heated in a muffle furnace in presence of air. Calcined powders obtained were further characterized using powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and BET surface area analyzer. Solar fuel production ability and thermal stability of the synthesized Ce0.75Zr0.125Hf0.125O2 redox material was investigated by performing multiple thermochemical oxidation and thermal reduction cycles in presence of CO2 and inert Ar using a thermogravimetric analyzer (TGA).Acknowledgments The authors gratefully acknowledge the financial support provided by the Qatar University (QUUG-CENG-CHE-13/14-4), Indo-Swiss Joint Research Program (ISJRP, grant #138852), and Swiss Federal Office of Energy.Scopu

Solar thermochemical conversion of CO2 into synthetic fuels via ferrite based redox reactions

In this contribution, we report the synthesis NiFe2O4 and CoFe2O4 redox materials via sol-gel method. For the synthesis of these materials via sol-gel approach, the Ni, Co, and Fe precursors were first dissolved in ethanol with the help of sonic energy. Once the metal precursors were dissolved, propylene oxide (PO) was added dropwise to the well mixed solution as a gelation agent to achieve gel formation. As-prepared gels were aged, dried and subsequently calcined in presence air. The calcined powder obtained was characterized towards its phase/chemical composition, particle morphology, and specific surface area (SSA). Derived NiFe2O4 and CoFe2O4 redox materials were further investigated towards thermochemical splitting of CO2 into solar fuels by performing several reduction/re-oxidation cycles using a thermogravimetric analyzer (TGA).Scopu