scholarly journals Solar Thermochemical Hydrogen Production via Terbium Oxide Based Redox Reactions

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Rahul Bhosale ◽  
Anand Kumar ◽  
Fares AlMomani
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Water Splitting ◽  
Thermal Reduction ◽  
Terbium Oxide ◽  
Heat Recuperation ◽  
Solar Thermochemical ◽  
Oxidation By Water ◽  
Heat Released ◽  
Reaction Equilibrium

The computational thermodynamic modeling of the terbium oxide based two-step solar thermochemical water splitting (Tb-WS) cycle is reported. The 1st step of the Tb-WS cycle involves thermal reduction of TbO2into Tb and O2, whereas the 2nd step corresponds to the production of H2through Tb oxidation by water splitting reaction. Equilibrium compositions associated with the thermal reduction and water splitting steps were determined via HSC simulations. Influence of oxygen partial pressure in the inert gas on thermal reduction of TbO2and effect of water splitting temperature (TL) on Gibbs free energy related to the H2production step were examined in detail. The cycle (ηcycle) and solar-to-fuel energy conversion (ηsolar-to-fuel) efficiency of the Tb-WS cycle were determined by performing the second-law thermodynamic analysis. Results obtained indicate thatηcycleandηsolar-to-fuelincrease with the decrease in oxygen partial pressure in the inert flushing gas and thermal reduction temperature (TH). It was also realized that the recuperation of the heat released by the water splitting reactor and quench unit further enhances the solar reactor efficiency. AtTH=2280 K, by applying 60% heat recuperation, maximumηcycleof 39.0% andηsolar-to-fuelof 47.1% for the Tb-WS cycle can be attained.

scholarly journals Computationally Accelerated Discovery and Experimental Demonstration of Gd0.5La0.5Co0.5Fe0.5O3 for Solar Thermochemical Hydrogen Production

2021 ◽  
Vol 9 ◽  
Author(s):  
James Eujin Park ◽  
Zachary J. L. Bare ◽  
Ryan J. Morelock ◽  
Mark A. Rodriguez ◽  
Andrea Ambrosini ◽  
...  
Keyword(s):  
Water Splitting ◽  
Thermal Reduction ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Electron Effective Mass ◽  
Concentrated Solar Energy ◽  
Perovskite Materials ◽  
Oxygen Vacancy Formation ◽  
Solar Thermochemical ◽  
Xrd Patterns

Solar thermochemical hydrogen (STCH) production is a promising method to generate carbon neutral fuels by splitting water utilizing metal oxide materials and concentrated solar energy. The discovery of materials with enhanced water-splitting performance is critical for STCH to play a major role in the emerging renewable energy portfolio. While perovskite materials have been the focus of many recent efforts, materials screening can be time consuming due to the myriad chemical compositions possible. This can be greatly accelerated through computationally screening materials parameters including oxygen vacancy formation energy, phase stability, and electron effective mass. In this work, the perovskite Gd0.5La0.5Co0.5Fe0.5O3 (GLCF), was computationally determined to be a potential water splitter, and its activity was experimentally demonstrated. During water splitting tests with a thermal reduction temperature of 1,350°C, hydrogen yields of 101 μmol/g and 141 μmol/g were obtained at re-oxidation temperatures of 850 and 1,000°C, respectively, with increasing production observed during subsequent cycles. This is a significant improvement from similar compounds studied before (La0.6Sr0.4Co0.2Fe0.8O3 and LaFe0.75Co0.25O3) that suffer from performance degradation with subsequent cycles. Confirmed with high temperature x-ray diffraction (HT-XRD) patterns under inert and oxidizing atmosphere, the GLCF mainly maintained its phase while some decomposition to Gd2-xLaxO3 was observed.

Quantitative Determination of the Distribution between Two Photosystem II-Mediated Oxidation Reactions in Oscillatoria chalybea: A Comparison between Water Oxidation and Hydrogen Peroxide Decomposition

1990 ◽  
Vol 45 (7-8) ◽  
pp. 757-764 ◽  
Author(s):  
K. P. Bader ◽  
G. H. Schmid
Keyword(s):  
Photosystem Ii ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Water Splitting ◽  
Oxygen Evolution ◽  
State System ◽  
Ambient Atmosphere ◽  
High Oxygen Partial Pressure ◽  
Oscillatoria Chalybea ◽  
Light Flashes

Abstract Mass spectromctric analysis reveals that oxygen evolution measured as the consequence of short saturating light flashes in thylakoid preparations of the filamentous cyanobacterium Oscillatoria chalybea consists of two portions, one coming from photosynthetic water splitting and one coming from H2O2 decomposition. This H2O2 decomposition is photosystem II-mediated and it is the S-state system which oxidizes H2O2 to give protons and oxygen. Water is neither intermediate nor seems it to be the origin of the reaction. At the high oxygen partial pressure of normal air H2O2 production and its decomposition exceeds manyfold the H2O splitting reaction. H2O2 production seems to come from photosystem II but is not necessarily produced on the acceptor side of photosystem II in the sense of a Mehler type reaction. From the reaction rate and the observed labeling density, it is inferred that production and decomposition must take place within the same reaction site which might be for both, the production and decomposition, the S-state system. In this sense. H2O2 might be the product of the S-state system and seems somehow associated with S2 or S3. Thus, if oxygen evolution is measured as the consequence of short saturating light flashes in an ambient atmosphere of 21% oxygen, mass spectrometry reveals a flash pattern which bears the oxygen label of the ambient atmosphere and which has not much in common with an usual Kok sequence. Such a pattern might start in the first three flashes more or less as a Kok pattern would, but is then in the pattern portion usually characteristic for steady-state oxygen evolution characterized by a periodicity of two indicating that H2O2 decomposition requires only two light quanta. At high oxygen partial pressure (e.g. in 21% ,16O2) both reaction portions can be quantitatively deter- mined by labeling the assay with H218O and measuring the evolved (16O::18O)/18O2 ratio which is representative for water splitting. The measured evolution of 16O2 (mass 32) represents H2O2 decomposition, if the 16O2 portion calculated from the measured mass 34/36 ratio is subtracted. At low oxygen partial pressure the H2O2 forming and decomposing reaction is largely sup- pressed and oxygen evolution from water-splitting prevails. As a hypothesis, H2O2 production and its decomposition might be a defective performance of photosystem II at high ambient oxygen partial pressure in these cyanobacteria, perhaps due to the principal absence of two of the extrinsic peptides from photosystem II.

Hydrogen Production by Solar Thermochemical Water-Splitting/Methane-Reforming Process

Solar Energy ◽  
2003 ◽  
Author(s):  
Tatsuya Kodama ◽  
Yoshiyasu Kondoh ◽  
Atsushi Kiyama ◽  
Ken-Ich Shimizu
Keyword(s):  
Hydrogen Production ◽  
Metal Oxide ◽  
Water Splitting ◽  
Thermal Energy ◽  
Experimental Studies ◽  
Reduction Process ◽  
Thermal Reduction ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
Solar Thermochemical

Two different routes of solar thermochemical hydrogen production are reviewed. One is two-step water splitting cycle by using a metal-oxide redox pair. The first step is based on the thermal reduction of metal oxide, which is a highly endothermic process driven by concentrated solar thermal energy. The second step involves water decomposition with the thermally-reduced metal oxide. The first thermal reduction process requires very-high temperatures, which may be realized in sun-belt regions. Another hydrogen production route is solar reforming of natural gas (methane), which can convert methane to hydrogen via calorie-upgrading by using concentrated solar thermal energy. Solar reforming is currently the most advanced solar thermochemical process in sun belt. There is also possibility for the solar reforming to be applied for worldwide solar concentrating facilities where direct insolation is weaker than that in sun belt. Our experimental studies to improve the relevant catalytic technologies are shown and discussed.

scholarly journals Effect of Hot-Dip Galvanizing Process on Selective Oxidation and Galvanizability of Medium Manganese Steel for Automotive Application

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1265
Author(s):  
Zhang Chen ◽  
Yanlin He ◽  
Weisen Zheng ◽  
Hua Wang ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Surface Oxidation ◽  
Steel Sample ◽  
Dew Point ◽  
Manganese Steel ◽  
Automotive Application ◽  
Stable Phase ◽  
Annealing Atmosphere ◽  
Medium Manganese Steel

A medium manganese steel with 7.5 wt.% Mn for automobile application was galvanized in a continuous Hot Dip Galvanizing (HDG) simulator under different galvanizing conditions. It was shown that the effects of dew point, annealing temperature and annealing atmosphere on the surface oxidation of steel could be comprehensively evaluated by the consideration of oxygen partial pressure P(O2). Although Mn2SiO4 was a thermodynamic stable phase when P(O2) varied from 10−28 to 10−21 atm, it was difficult to form Mn–Si–O composite oxide because there was no enrichment of silicon on the steel surface. So, this oxide was generally formed in the Fe substrate and had little effect on the galvanizability. With the increase in P(O2) above 10−25 atm, MnO particles in the form of the thermodynamic stable phase became coarser and tended to aggregate, which hindered the formation of a continuous inhibition layer, resulting in the defects of bare spots on the galvanized surface of the steel. When the oxygen partial pressure greater than 10−22 atm, film-like MnO layer was formed on the surface of steel sample, which obviously deteriorated the galvanizability. The galvanizability of the steel can be improved by the regulation of oxygen partial pressure; based on this, the reasonable zinc plating process parameters can be developed.

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