SEARCH · Engineering Papers
Results for “waters”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Sugar Blowing-Induced Porous Cobalt Phosphide/Nitrogen-Doped Carbon Nanostructures with Enhanced Electrochemical Oxidation Performance toward Water and Other Small Molecules
Finely controlled synthesis of high active and robust nonprecious metal catalysts with excellent catalytic efficiency in oxygen evolution reaction (OER) is extremely vital for making the water splitting process more energy-efficient and economical. Among these noble metal-free catalysts, transition-metal-based nanomaterials are considered as one of the most promising OER catalysts due to their relatively low-cost intrinsic activities, high abundance and diversity in terms of structure and morphology. In this work, we reported a facile sugar-blowing technique and low-temperature phosphorization to generate 3D self-supported metal involved carbon nanostructures, which termed as Co2P@Co/nitrogen-doped carbon (Co2P@Co/N-C). By capitalizing on the 3D porous nanostructures with high surface area, generously dispersed active sites, the intimate interaction between active sites and 3D N-doped carbon, the resultant Co2P@Co/N-C exhibited satisfying OER performance superior to CoO@Co/N-C, delivering 10 mA cm-2 at overpotential of 0.32 V. It is noting that in contrast to the substantial current density loss of RuO2, Co2P@Co/N-C showed much enhanced catalytic activity during the stability test and the 1.8-fold increase in current density was observed after stability test. Furthermore, the obtained Co2P@Co/N-C can also be served as an excellent nonprecious metal catalyst for methanol and glucose electrooxidation in alkaline media, further extending their potential applications.
Trifunctional Single-Atomic Ru Sites Enable Efficient Overall Water Splitting and Oxygen Reduction in Acidic Media
Explore the source record for details and available documents.
Understanding the structural drivers governing glass–water interactions in borosilicate based model bioactive glasses
Not Available
Evaluation of COSMO-SAC method for the prediction of the alcohol-water partition coefficients of the compounds encountered in aqueous phase fructose dehydration
Explore the source record for details and available documents.
Thermoelectric topping cycles for power plants to eliminate cooling water consumption
Explore the source record for details and available documents.
Influence of blending and hot water extraction on the quality of wood pellets
Not provided.
Striving toward noble-metal-free photocatalytic water splitting: The hydrogenated-graphene-TiO 2 prototype
Graphane, graphone and hydrogenated graphene (HG) have been extensively studied in recent years due to their interesting properties and potential use in commercial and industrial applications. The present study reports investigation of hydrogenated graphene/TiO 2-x (HGT) nanocomposites as photocatalysts for H 2 and O 2 production from water without the assistance of a noble metal co-catalyst. By combination of several techniques, the morphologies, bulk/atomic structure and electronic properties of all the powders were exhaustively interrogated. Hydrogenation treatment efficiently reduces TiO 2 nanoparticles, while the graphene oxide sheets undergo the topotactic transformation from a graphene-like structure to a mixture of graphitic and turbostratic carbon (amorphous/disordered) upon altering the calcination atmosphere from a mildly reducing to a H 2 -abundant environment. Remarkably, the hydrogenated graphene-TiO 2-x composite that results upon H 2 -rich reduction exhibits the highest photocatalytic H 2 evolution performance equivalent to low loading of Pt (~0.12 wt%), whereas the addition of HG suppresses the O 2 production. As a result, we propose that such an enhancement can be attributed to a combination of factors including the introduction of oxygen vacancies and Ti 3+ states, retarding the recombination of charge carriers and thus, facilitating the charge transfer from TiO 2 -x to the carbonaceous sheet.
5-Methoxyquinoline Photobasicity Is Mediated by Water Oxidation
A mechanism explaining the photobasicity of 5-methoxyquinoline (5-MeOQ) is proposed on the basis of nonadiabatic molecular dynamics simulations using time-dependent hybrid density functional theory (TDDFT) and fewest switches surface hopping (SH) and analysis of existing ultrafast spectroscopy experiments. According to the TDDFT-SH simulations, the rate-determining step is hole transfer from photoexcited 5-MeOQ to adjacent water molecules within ~5 ps followed by rapid electron-coupled proton transfer and deactivation to the ground state. This fast redox-catalyzed proton transfer mechanism is consistent with simple thermodynamic arguments, correlated wavefunction calculations, and recent isotope substitution time-resolved fluorescence experiments. Although energetically feasible, direct protonation of 5-MeOQ in the S 1 state appears to be too slow to contribute significantly to 5-MeOQ photobasicity in aqueous solution.
Comprehensive Experimental and Computational Spectroscopic Study of Hexacyanoferrate Complexes in Water: From Infrared to X-ray Wavelengths
We present a joint experimental and computational study of the hexacyanoferrate aqueous complexes at equilibrium in the 250 meV to 7.15 keV regime. The experiments include the vibrational spectroscopy of the cyanide ligands, the valence electronic absorption spectra and Fe 1s core hole spectra using X-ray absorption and emission techniques. These experiments are accompanied by density functional theory (DFT) based quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations and spectroscopy calculations of the experiments spanning the IR to X-ray wavelengths. Our simulations, including explicit solvent effects, across this large energy window allows for a systematic comparison of vibrational, valence electronic and core-level spectra. The analysis reveals how the local solvation environment influences the geometric and electronic structure and impacts the line shape and intensity of the observed spectral features in the infrared, optical and X-ray wavelengths.
In Situ Characterization of Mesoporous Co/CeO 2 Catalysts for the High-Temperature Water-Gas Shift
Here, mesoporous Co/CeO 2 catalysts were found to exhibit significant activity for the high-temperature water-gas shift (WGS) reaction with cobalt loadings as low as 1 wt %. The catalysts feature a uniform dispersion of cobalt within the CeO 2 fluorite type lattice with no evidence of discrete cobalt phase segregation. In situ XANES and ambient pressure XPS experiments were used to elucidate the active state of the catalysts as partially reduced cerium oxide doped with oxidized cobalt atoms. In situ XRD and DRIFTS experiments suggest facile cerium reduction and oxygen vacancy formation, particularly with lower cobalt loadings. In situ DRIFTS analysis also revealed the presence of surface carbonate and bidentate formate species under reaction conditions, which may be associated with additional mechanistic pathways for the WGS reaction. Deactivation behavior was observed with higher cobalt loadings. XANES data suggest the formation of small metallic cobalt clusters at temperatures above 400 °C may be responsible. Notably, this deactivation was not observed for the 1% cobalt loaded catalyst, which exhibited the highest activity per unit of cobalt.
Predicted Efficient Visible-Light Driven Water Splitting and Carbon Dioxide Reduction Using Photoredox-Active UiO-NDI Metal Organic Framework
The structural and electronic properties of metal–organic frameworks (MOFs) constructed from stable Zr(IV) oxide-based nodes and naphthalenediimide-based linkers (UiO(Zr)-NDI) can be tuned to make them useful for specific photoredox processes. The NDI linker presents outside, inside, and core positions where functionalization can influence its optical properties, and such substitution in combination with suitable optical band gaps and band edge positions in UiO(Zr)-NDI offers a platform for the design of efficient MOF-based photocatalysts for water splitting and CO 2 reduction. Here, the band gaps and edge positions remain similar for UiO nodes when Zr is substituted with Ti, Th, or Ce. However, in contrast to the case for Zr-, Ti-, and Th-based UiO-NDIs, where photoexcitation remains localized on the NDI linkers owing to the very high energies of unoccupied node-based bands, for UiO(Ce)-NDI, the availability of low-lying empty f orbitals in the metal node offers the potential for energy transfer and exciton migration, which could further boost photocatalytic performance by extending exciton lifetimes.
Water Structure Controls Carbonic Acid Formation in Adsorbed Water Films
Reaction pathways and kinetics in highly structured H2O adsorbed as Ångstroms to nanometers thick layers on mineral surfaces are distinct from those facilitated by bulk liquid water. We investigate the role of interfacial H2O structure in the reaction of H2O and CO2 to form carbonic acid (H2CO3) in thin H2O films condensed onto silica nanoparticles from humidified supercritical CO2. Rates of carbonic acid formation are correlated to spectroscopic signatures of H2O structure using oxygen isotopic tracers and infrared spectroscopy. While carbonic acid virtually does not form in the supercritical phase, the silica surface catalyzes this reaction by concentrating H2O through adsorption at hydrophilic silanol groups. Within measurement uncertainty, we found no evidence that carbonic acid forms when exclusively ice-like structured H2O is detected at the silica surface. Instead, formation of H2C18O16O2 from H218O and C16O2 was found to be linearly correlated with liquid-like structured H2O that formed on the ice-like layer.
Hybrid Polymer/Metal–Organic Framework Films for Colorimetric Water Sensing over a Wide Concentration Range [Hybrid Polymer/MOF Films for Colorimetric Water Sensing over a Wide Concentration Range]
Because of their extraordinary surface areas and tailorable porosity, metal–organic frameworks (MOFs) have the potential to be excellent sensors of gas-phase analytes. MOFs with open metal sites are particularly attractive for detecting Lewis basic atmospheric analytes, such as water. Here, we demonstrate that thin films of the MOF HKUST-1 can be used to quantitatively determine the relative humidity (RH) of air using a colorimetric approach. HKUST-1 thin films are spin-coated onto rigid or flexible substrates and are shown to quantitatively determine the RH within the range of 0.1–5% RH by either visual observation or a straightforward optical reflectivity measurement. At high humidity (>10% RH), a polymer/MOF bilayer is used to slow the transport of H 2 O to the MOF film, enabling quantitative determination of RH using time as the distinguishing metric. Lastly, the sensor is combined with an inexpensive light-emitting diode light source and Si photodiode detector to demonstrate a quantitative humidity detector for low humidity environments.
Water-Fed Hydroxide Exchange Membrane Electrolyzer Enabled by a Fluoride-Incorporated Nickel–Iron Oxyhydroxide Oxygen Evolution Electrode
Here, we have developed a dissolved oxygen and galvanic corrosion method to synthesize vertically aligned fluoride-incorporated nickel–iron oxyhydroxide nanosheet arrays on a compressed Ni foam as an efficient self-supported oxygen evolution electrode. It is integrated with poly(aryl piperidinium) hydroxide exchange membrane and ionomers with high ion exchange capacity into a hydroxide exchange membrane electrolyzer fed with pure water, which achieves a performance of 1020 mA cm –2 at 1.8 V and prevents the detachment of catalysts during continuous operation (>160 h at 200 mA cm –2 ). Furthermore, this work provides a potential pathway for massively producing low-cost hydrogen using intermittent renewable energy sources.