High Pressure Supercritical <i>PVT</i>‐Data of Water‐Sodium Hydroxide Mixtures and of Liquid Sodium Hydroxide to 673 K and 400 MPa

Kerschbaum, S.; Franck, E. U.

doi:10.1002/bbpc.19950990406

Cited by 10 publications

(10 citation statements)

References 2 publications

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“…[108] The data yield ionic activity coefficients that differ greatly from unity at all compositions. In modeling chemical or phase equilibria, the consideration of activity corrections is therefore mandatory.…”

Section: Angewandte Chemiementioning

confidence: 98%

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Supercritical Water as a Solvent

2005

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Water is not restricted to moderate temperatures and low pressures, but can exist up to very high temperatures, far above its critical point at 647 K. In this supercritical regime, water can be gradually compressed from gas-like to liquid-like densities. The resulting dense supercritical states have extraordinary properties which can be tuned by temperature and pressure, and form the basis for innovative technologies. This Review covers the current knowledge of the major properties of supercritical water and its solutions with nonpolar, polar, and ionic compounds, and of the underlying molecular processes.

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Section: Angewandte Chemiementioning

confidence: 98%

“…There are some promising results in this direction, for Figure 12. Excess molar Gibbs energies at 673 K of H 2 O + O 2 (top) [64] and H 2 O + NaOH (bottom) [108] as a function of the mole fractions of the solutes (O 2 and NaOH) at the pressures indicated in the Figure. [44b] x(C 6 H 6 ) is the mole fraction of benzene.…”

Section: Multicomponent Mixturesmentioning

confidence: 99%

Supercritical Water as a Solvent

2005

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“…20,21 This study provides an initial exploration of water splitting in molten hydroxide electrolytes at higher temperatures ranging up to 700…”

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confidence: 99%

Comparison of Alternative Molten Electrolytes for Water Splitting to Generate Hydrogen Fuel

Licht

Liu

Cui

et al. 2016

J. Electrochem. Soc.

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This study explores a new high temperature molten hydroxide domain to electrochemically split water into hydrogen fuel. Hydrogen fuel, if produced without greenhouse gas emissions, is a promising fuel for transportation. This study opens a pathway to low energy water splitting and the electrolytic production of hydrogen fuel without carbon dioxide emission. A wide range of pure and mixed alkali and alkali earth hydroxide electrolytes are explored at temperatures ranging from 200 to 700 • C. Higher temperature leads to improved (lower voltage) water splitting and improved rates of charge transfer, but carries challenges (increased rates of parasitic side reactions as the molten electrolytes dehydrate with increasing temperature). This study extends the range of hydrogen formation in alkaline electrolysis water splitting to over 600 • C, and demonstrates that lithium and/or barium hydroxide electrolytes remain hydrated at high temperatures, and in the high temperature domain are advantageous over sodium or potassium hydroxide electrolytes. In pure LiOH, the coulombic efficiency for hydrogen generation decreases with temperature and is measured respectively at η H 2 = 88%, 21%, 4% and 0%, respectively at 500, 600, 700 and 800 • Hydrogen has advantageous features compared to fossil fuels. It has a higher specific energy, is not polluting, has a combustion product of water, and in particular it does not emit the greenhouse gas carbon dioxide. Challenges of hydrogen storage are being addressed and hydrogen powered vehicles have been introduced to the commercial marketplace.1-4 Unfortunately, the predominant fraction of hydrogen generated today is produced by steam reformation of fossil fuel by reacting the fossil fuel with steam to release H 2 and CO 2 . Steam reformation is a substantial source of CO 2 emissions, negating the climate mitigation effect of using H 2 as a fuel. Thus, a process to efficiently generate hydrogen without carbon dioxide emissions is needed.The development of electrolytic splitting of water dates back to 1802. 5 The electrolysis of water produces hydrogen and oxygen directly without CO 2 emission (if the energy source used to generate the electricity did not release CO 2 ). Utilization of renewable or nuclear energy to generate the electricity for this electrolysis can drive this electrolytic water splitting to produce hydrogen as a fuel without carbon dioxide emissions. The most abundant of renewable energy resource for electrical generation is solar energy, and as early as 2001 we were driving stable solar electrolytic water splitting to hydrogen fuels at over 18% solar to chemical energy conversion by using efficient multiple bandgap solar cells.6 One of the challenges to the use of illuminated junctions to drive electrochemical or photoelectrochemical water splitting is that the bandgap of efficient semiconductors lies in the visible spectrum which generate a photo-potential less than the minimum needed rest potential of 1.23 volt required to split water to hydrogen and oxygen at room te...

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“…One electrolyte of choice, however, is sodium hydroxide, which above its melting point at 321°C is completely miscible with high density water and thus offers a broad homogeneous region at moderate temperatures and pressures. Figure 7 shows the experimental molar volumes at compositions from pure water to pure molten hydroxide at three different pressures [73]. At 400 MPa the molar volume of water is smaller than that of sodium hydroxide.…”

Section: Water-molten Salt Systemsmentioning

confidence: 96%

“…Only below 20 mol percent the conductance increases steeply to values expected for dilute solutions. Using the concept of varying hydration with a semi-empirical equation, we were able to calculate density and conductivity [73,74]. …”

Section: Water-molten Salt Systemsmentioning

confidence: 99%