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Unusual Reduction of Graphene Oxide by Titanium Dioxide Electrons Produced by Ionizing Radiation: Reaction Products and Mechanism
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Near-UV light assisted green reduction of graphene oxide films through l-ascorbic acid
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Reflection Optical Imaging to Study Oxygen Evolution Reactions
Discovery of high-efficiency water-splitting catalysts is critical for clean hydrogen fuel generation. Quantitative and reliable chemical imaging methods can play a crucial role in providing critical catalyst efficiency information for materials development and screening. Here, we developed a reflection optical imaging method to map the performance of transition metal oxide catalysts for oxygen evolution reaction (OER). The generated high concentration of oxygen in the electrolyte will decrease the refractive index of the solutions near the electrode and change the reflectivity of optical images. We successfully imaged and measured the OER on cobalt oxide, and the localized current density and overpotential distribution maps have been extracted. The oxidation and reduction of cobalt oxide can be imaged with our reflection optical imaging method as well. These maps showed that the catalytic activities are quite different at different locations, and some regions showed much higher activities. This is due to the non-uniformity created by the catalyst synthesis process and demonstrates the importance of using the optical imaging method to map the localized catalytic efficiency. In addition, the NiFe alloy’s OER catalytic activities have been studied as well. The proposed reflection optical imaging method could find many applications in catalyst activity measurement and screening.
Reduction of nitric oxide emissions from a combustor
A turbojet combustor and method for controlling nitric oxide emissions by employing successive combustion zones is described. After combustion of an initial portion of the fuel in a primary combustion zone, the combustion products of the primary zone are combined with the remaining portion of fuel and additional plenum air and burned in a secondary combustion zone under conditions that result in low nitric oxide emissions. Low nitric oxide emissions are achieved by a novel turbojet combustor arrangement which provides flame stability by allowing stable combustion to be accompanied by low nitric oxide emissions resulting from controlled fuel-lean combustion (ignited by the emission products from the primary zone) in a secondary combustion zone at a lower combustion temperature resulting in low emission of nitric oxide.
Effects of 14 days of spaceflight and nine days of recovery on cell body size and succinate dehydrogenase activity of rat dorsal root ganglion neurons
The cross-sectional areas and succinate dehydrogenase activities of L5 dorsal root ganglion neurons in rats were determined after 14 days of spaceflight and after nine days of recovery. The mean and distribution of the cross-sectional areas were similar to age-matched, ground-based controls for both the spaceflight and for the spaceflight plus recovery groups. The mean succinate dehydrogenase activity was significantly lower in spaceflight compared to aged-matched control rats, whereas the mean succinate dehydrogenase activity was similar in age-matched control and spaceflight plus recovery rats. The mean succinate dehydrogenase activity of neurons with cross-sectional areas between 1000 and 2000 microns2 was lower (between 7 and 10%) in both the spaceflight and the spaceflight plus recovery groups compared to the appropriate control groups. The reduction in the oxidative capacity of a subpopulation of sensory neurons having relatively large cross-sectional areas immediately following spaceflight and the sustained depression for nine days after returning to 1 g suggest that the 0 g environment induced significant alterations in proprioceptive function.
The Isotopic Composition of Molecular Water Formed by Hydrogen Reduction of Iron Oxides: A Proxy for Endogenous Water Formed From Solar Wind Implantation
Many workers have successfully utilized a variety of lunar materials to infer the sources and processing history of volatiles on the Moon. In situ techniques via NanoSIMS have enabled a plethora of hydrogen isotope measurements of isolated grains in regolith and apatite within igneous rocks, revealing an extraordinarily large range of δD values from ~ -900 to +1000‰. The lowest of these δD values are related to the incorporation of solar wind hydrogen, which is pure 1 H. Exposure to solar wind results in structural damage to crystalline phases, forming ubiquitous tens-to-hundreds of nanometer thick amorphous rims on mature regolith grains. Solar wind implantation of H + is also is also thought to result in the formation of nanophase Fe 0 (npFe), a quantitative metric of surface exposure time (e.g., Is/FeO). The formation of npFe can be generally described via the reaction: Fe 2+ O + H 2 = Fe 0 + H 2 O, resulting in the formation of endogenous molecular water reservoirs.
Benefit of China’s reduction in nitrogen oxides emission to natural ecosystems in East Asia with respect to critical load exceedance
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Characterization study of polycrystalline tin oxide surfaces before and after reduction in CO
Polycrystalline tin oxide surfaces have been examined before and after reduction in 40 Torr of CO at 100 and 175 C using Auger electron spectroscopy (AES), electron spectroscopy for chemical analysis (ESCA), ion scattering spectroscopy (ISS) and electron stimulated desorption (ESD). The changes in the surface composition and chemical states of the surface species generally are subtle for the reductive conditions used. However, significant changes do occur with regard to the amounts and the chemical forms of the hydrogen-containing species remaining after both the 100 and 175 C reductions.
Design of Twisted Two-Dimensional Heterostructures and Performance Regulation Descriptor for Electrocatalytic Ammonia Production from Nitric Oxide
The electrocatalytic reduction of nitric oxide (NO) to ammonia (NH 3 ) represents an attractive alternative for valorizing waste NO streams (NORR). However, discovering efficient catalysts for NO-to-NH 3 conversion remains challenging. We have designed metal-intercalated twisted graphene-BN heterostructures, in which metal atoms act as electron-transfer bridges. The twisted configuration facilitates cross-interface charge transfer, redistributing electrons from the graphene–metal interface to the metal–BN interface and BN surface. This electronic modulation enables boron atom adjacent to the metal center in BN to serve as active sites, promoting strong chemisorption and enhanced activation of NO. After high-throughput screening of the stability and NO capture ability of various transition metal-intercalated twisted heterostructures, we have investigated systematically the NORR pathways across 30 candidates. The results show that the rBN-Ti-Gθ and rBN-V-Gθ heterostructures exhibit exceptional NO-to-NH 3 catalytic performance under optimized twisting conditions. Additionally, using sure independence screening and sparsifying operator (SISSO) for model training, we propose a descriptor and establish a relationship between the twist angle and catalytic activity. This study bridges the gap in applying twisted heterostructures to NORR electrocatalysis and provides new insights and strategies for designing high-performance NORR catalysts.
Long-Lived Triplet Excited State in a Heterogeneous Modified Carbon Nitride Photocatalyst
Heterogeneous carbon nitrides have numerous advantages as photocatalysts, including strong light absorption, tunable band edges, and scalability, but their performance and continued development are limited by fast charge recombination and an under-developed mechanistic understanding of photodriven interfacial electron transfer. These shortcomings are a result of complex photophysics, leading to rate asynchrony between oxidation and reduction, as well as redox processes driven out of electronic trap states rather than excited states. We show that a well-defined triplet excited state in cyanamide-modified carbon nitride is realized with appropriately sized particles. The utility of this long-lived excited state is demonstrated by its ability to drive a hydroamidation photoredox cycle. By the tuning of the particle size of CN x , the oxidation–reduction photochemistry of carbon nitride may be balanced to achieve a redox-neutral closed photocatalytic cycle. Here, these results uncover a triplet excited state chemistry for appropriately sized CNx particles that preludes a rich energy and electron transfer photochemistry for these materials.
I. THERMAL STABILITY OF CU-SIO SUB 2 AND CU-AL SUB 2 O SUB 3 ALLOYS. II. PREPARATION OF OXIDE DISPERSION STRENGTHENED NICKELMOLYBDENUM ALLOYS BY SELECTIVE REDUCTION. III. THE MECHANISM OF INTERNAL OXIDATION OF DILUTE NICKEL ALLOYS.
Thermostability of copper-oxide alloys, oxide strengthened alloys, oxidation of alloys
Evidence of alloy formation during reduction of platinized tin oxide surfaces
Ion scattering spectroscopy, Auger electron spectroscopy, and electron spectroscopy for chemical analysis have been used to examine a platinized tin oxide catalyst surface before, during, and after reduction by annealing under vacuum at 250 to 450 C. These techniques were then used to examine the reduced surface after a room-temperature, low-pressure oxygen exposure. The spectral results and the behavior of the reduced surface toward oxygen exposure both indicate that a Pt/Sn alloy is produced during reduction.
Reactive Fe anode for electrolytic reduction of solid metal oxide in molten LiCl-Li 2 O
Iron metal was investigated for use as a consumable anode for electrolytic reduction of solid metal oxides in molten LiCl-Li 2 O (2.0 - 2.4 wt%). Tests were performed where the potential of Fe anodes was increased incrementally from 0.1 to 1.0 V (vs Ni/NiO). Oxide formation on the anode started at a potential of 0.4 V and was identified as FeO via X-ray diffraction. In the absence of a pre-formed oxide layer, severe attack of the anode started at a potential of 0.7 V and was accompanied by an increase in Fe concentration in the salt. When an oxide layer was allowed to form on the anode, the Fe concentration did not increase in the salt. O 2 was detected in the headspace gas at an anode potential of 1.0 V only when an oxide layer was present on the anode. Finally, the results of this study support the idea that an inexpensive sacrificial anode could be an ideal replacement for expensive Pt that is currently widely used for this process.
Reduction of Iron (III) Oxide in Microwaves Toward Gasification Studies
The purpose of this study is to reduce hematite (Fe2O3) using hydrogen (H2), carbon monoxide (CO), and methane (CH4) gases using microwave irradiation. Conventional temperature programmed reduction of iron phase transformation under H2, CO, and CH4 agree with the literature. Furthermore, the activation energy for the iron phase transformation in a conventional reactor was in the order of H2>CO>CH4, suggesting that CH4 was the best reductant to initiate the reduction at a much lower temperature than CO, and CO was significantly better than H2 atmosphere. Due to the uneven temperature distribution, the apparent activation energy of microwave reduction under H2 was approximately 1/4th when compared to the conventional reduction in H2. X-ray diffraction (XRD) analysis showed a mixed oxide phase in microwave reduction as opposed to the clear phase transformation in conventional studies. To combat the temperature measurement issues in microwave studies, fiber optic sensors and Forward Looking InfraRed (FLIR) sensors were used to acquire the actual temperature distribution in the catalyst bed. Therefore, a reasonably accurate activation energy estimation was achieved in the catalyst bed. Combining these with the characterization and quantification of the different iron phases in microwave reduction will provide a blueprint for future microwave-assisted gasification studies.
Acetate concentrations and oxidation in salt marsh sediments
Acetate concentrations and rates of acetate oxidation and sulfate reduction were measured in S. alterniflora sediments in New Hampshire and Massachusetts. Pore water extracted from cores by squeezing or centrifugation contained in greater than 0.1 mM acetate and, in some instances, greater than 1.0 mM. Pore water sampled nondestructively contained much less acetate, often less than 0.01 mM. Acetate was associated with roots, and concentrations varied with changes in plant physiology. Acetate turnover was very low whether whole core or slurry incubations were used. Radiotracers injected directly into soils yielded rates of sulfate reduction and acetate oxidation not significantly different from core incubation techniques. Regardless of incubation method, acetate oxidation did not account for a substantial percentage of sulfate reduction. These results differ markedly from data for unvegetated coastal sediments where acetate levels are low, oxidation rate constants are high, and acetate oxication rates greatly exceed rates of sulfate reduction. The discrepancy between rates of acetate oxidation and sulfate reduction in these marsh soils may be due either to the utilization of substrates other than acetate by sulfate reducers or artifacts associated with measurements of organic utilization by rhizosphere bacteria. Care must be taken when interpreting data from salt marsh sediments since the release of material from roots during coring may affect the concentrations of certain compounds as well as influencing results obtained when sediment incubations are employed.
Addressing Limitations of the Endpoint Slippage Analysis
Some rate of oxidation and reduction side-reactions will inevitably coexist in most rechargeable batteries. While parasitic reduction traps electrons, parasitic oxidation donates electrons to the cell’s inventory and may cause temporary capacity gain. Consequently, capacity measurements can provide unreliable information about the total extent of side-reactions occurring in the cell. The most widely used method to determine the rate of both these parasitic processes involves analyzing the slippage of endpoints, which consists in tracking the termination of cell charge and discharge when data is represented along a cumulative capacity axis. Here, we argue that this approach could lead to inaccuracies when applied to certain systems, which includes Si electrodes in Li-ion batteries and hard carbon in Na-ion batteries. This inaccuracy originates from the smooth nature of the voltage profiles of these materials at low and high alkali-ion content, causing the termination of charge and discharge to be dictated by voltage changes at both the positive and negative electrodes. We analyze this issue in quantitative terms and propose equations that can provide true rates of parasitic processes from experimental endpoint slippage data. This work shows that, in battery science, well-established analytical approaches may not be directly transferrable to new electrode systems.