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Carbon capture and storage (CCS) technologies have the potential for reducing greenhouse gas emissions and creating clean energy solutions. One of the major aspects of the CCS technology is designing energy-efficient adsorbent materials for carbon dioxide capture. In this research, using a combination of first-principles theory, synthesis, and property measurements, we explore the CO

We developed a Zn-doped δ-MnO2 material via a microwave-assisted method for the cathode in aqueous ZIBs. The successive insertion of H+ and Zn2+ and deep two-electron transfer routes mechanism is revealed systematically by ex situ experiments.

The improved performance of the multi-component Cu–Ce–Mn/TNA catalysts over the mono-metallic catalysts demonstrated the synergistic promotion of multi-transition-metal-doped nanoarray catalysts for efficient NO abatement.

HI-NICALON™ Type S SiC fibers are the current state of the art commercially-available silicon carbide ceramic fibers with minimal oxygen content, high strength and creep resistance. While their stoichiometry is near 1:1 C:Si, there is still excess carbon present on the fiber surface, adjacent to the fiber surface, and throughout the fiber, from synthesis, and they are shipped under a sizing of polyvinyl alcohol to prevent damage during handling. For incorporation into a CMC, removal of both the excess carbon and sizing while maintaining the fiber strength is desired. This manuscript aims to perform both surface decarburization and desizing of HI-NICALON™ Type S SiC fiber tows while maintaining strength. A mechanism of the two processes is proposed through the use of TPD-MS and TGA-MS. Based on those thermal results, hydrogen and argon environments at elevated temperatures are used to desize and decarburize these fiber tows. SEM, Auger, and SIMS are used to study the fiber tow surfaces to determine the degree to which desizing and decarburization occurred. Tensile testing of treated fiber tows was performed to determine strength reduction caused by each treatment. A combination of hydrogen and argon at 1000 °C demonstrated the greatest desizing and decarburization, and resulted in little to no strength reduction or oxidation of the SiC fibers.

Herein, a straightforward synthesis method for highly mesoporous molybdenum oxide has been demonstrated via use of inverse micelles and molybdenum-oxo cluster formation. The synthesized catalyst is stable, crystalline, and MoO

Herein, we tailored a series of ultrathin MnO

Mo and V containing oxides are among the most important oxidative dehydrogenation catalysts. The effects of differences in structure and compostion among SiO2 supported VOx, unsupported V2O5 and MoO3 and M1 phase MoV mixed oxide catalysts on catalytic properties are probed using their reactivity and dehydrogenation selectivity in oxidative conversion of ethane (C2H6) and cyclohexane (C6H12). The C2H6 and C6H12 activation rates are nearly insensitive to VOx loading on SiO2 at low loadings that predominantly form monovanadate species, but decrease at high loadings due to the formation of V2O5 nanoparticles with low V dispersion. The C–H activation enthalpies are lower at high loadings and in unsupported V2O5, suggesting that intrinsic reactivity of V2O5 nanoparticles is higher than monovanadates. The C2H6/C6H12 rate ratios are below 0.01 on all VOx/SiO2 catalysts, consistent with weaker C–H bonds in C6H12, but are higher on V2O5 nanoparticles than on low loading VOx/SiO2 samples. MoO3 samples exhibit lower rates and higher activation energies than VOx/SiO2 and V2O5 samples, and similar C2H6/C6H12 rate ratios as V2O5. M1 phase MoVTeNb and MoV mixed oxides contain one-dimensional micropores of size similar to C2H6 but much smaller than C6H12; preparation methods significantly affect their elemental composition, accessible micropore volumes and surface areas. Post-synthesis treatment of MoVTeNbO with H2O2 improves M1 phase purity, and increases in C2H6 and C6H12 activation rates are consistent with increase in their intrapore and external surface areas. The C2H6 and C6H12 activation rates in MoVO without Te and Nb are higher than values predicted from MoVTeNbO and their surface micropores and external surface areas, because higher V content in MoVO increases their reactivity by slightly decreasing activation energies. The C2H6/C6H12 rate ratios in these samples are much higher than VOx/SiO2, V2O5, and MoO3 and roughly correlate with internal/external surface ratios, which is consistent with C2H6 and C6H12 activation occurring inside and outside the pores, respectively. The M1 phase samples exhibit much higher selectivity than VOx/SiO2, V2O5, and MoO3, but among the M1 phase samples the selectivity is slightly lower in MoVO than in MoVTeNbO. Local structure and composition affect reactivity in M1 phase oxides and oxides without heptagonal micropores, but C2H6/C6H12 rate ratios and C2H4 selectivities are much higher in the M1 phase, which confirms for a broad range of oxides previously proposed roles of micropores in activating C2H6 selectively.

Herein, we report a synthesis method for highly porous molybdenum oxide via molybdenum-oxo cluster formation under acidic conditions providing extraordinary stability. Synthesized materials indicat...

Efficient and long-term stable electrocatalysts for the hydrogen evolution reaction (HER) via water splitting are urgently desired to ease the energy crisis and develop the sustainability of human society. However, the HER performance of state-of-the-art Pt in non-acidic solutions is unsatisfactory due to the severely sluggish kinetics. Here, DFT theoretical calculations reveal that the Ru/RuO2 composites enable high HER activity to be pursued under non-acidic conditions because of the distinctive Ru and RuO2 interface, which possess not only a strong capability to adsorb and dissociate water but also appropriate binding energies of H and OH. Therefore, we employ a simple strategy, including heating under an oxygen-poor environment and/or in situ electrochemical reduction, to partially reduce RuO2. The formed Ru/RuO2 interfaces demonstrate superior HER activities (e.g. η10 = 17 mV, 35 mV dec−1 in 1 M KOH) than Pt/C (e.g. η10 = 27 mV, 58 mV dec−1 in 1 M KOH) at both small (10–100 mA cm−2) and large (1 A cm−2) current densities in alkaline solution and even real seawater. Comprehensive experiments were conducted to investigate the structure-HER performance relationships. Moreover, benefiting from the bifunctional character of RuO2, a two-electrode system based on Ru/RuO2 composites and RuO2 exhibits the lowest cell voltage for water splitting in both 1 M KOH and 0.5 M H2SO4, respectively. A 300 h-stability test at 10 mA cm−2 without an obvious decay demonstrates the industrial prospects of the Ru/RuO2 composites to generate green energy.

One-dimensional titanium dioxide (TiO2) nanostructure arrays (nanoarrays) are important metal oxide nanomaterials that can be synthesized via facile solvothermal methods. The properties of the organic solvents can impose significant effects on the microstructures and properties of the final products. However, the discussions were limited to the homogeneously nucleated TiO2 nanomaterials in free-standing powder form, while the solvent effects are less understood during the heterogeneous growth of TiO2 nanoarrays on a substrate surface. In this work, six organic compounds, namely 2-butanone, n-decane, n-hexane, toluene, ethylene glycol and ethanol, were selected as the solvents for the solvothermal synthesis of TiO2 nanoarrays on the cordierite monolithic substrates. Special attentions are paid to the morphology, crystallinity, specific surface area, and porosity of the samples. The heterogeneous growth of TiO2 nanoarrays on substrate surfaces is found to favor the solvents with moderate dielectric constants, which can be partially dissolved in the aqueous solution and modulate the reaction rate during the solvothermal synthesis. Organic solvents with low dielectric constants may result in a complete separation between the precursors and aqueous solution, and therefore slow down the overall reaction, causing the insufficient growth of the nanoarrays. The TiO2 nanoarrays are obtained with optimum morphology from the combination of 2-butanone and titanium (IV) butoxide as solvent and precusor, respectively, with a high specific surface area up to 56 m2/g including cordierite substrate given a micron thickness. When loaded with Pt catalyst, the TiO2 nanoarray-based monolithic catalysts show excellent low-temperature catalytic activity and hydrothermal stability for the CO and hydrocarbon oxidation under the simulated exhausted conditions. This work shall shed light on a better understanding of the growth mechanism and rational design of TiO2 nanoarrays for high-performance catalytic converters.

Heterointerface engineering is a desirable way to rationally design efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER). Herein, urchin-like Co9S8@NiFe layered double hydroxide (Co9S8@NiFe LDH) heterostructured hollow spheres are assembled from Co9S8 hollow spheres as the core and porous NiFe LDH nanowires as the shell. The heterostructured hollow spheres show a small overpotential of 220 mV at a current density of 10 mA cm−2, a low Tafel slope of 52.0 mV dec−1, and robust stability, which is better than that of commercial IrO2 and most reported non-precious electrocatalysts. Density functional theory (DFT) calculations show that the synergetic effect at the interface could improve the electrical conductivity of Co9S8@NiFe LDH, induce electron transfer from NiFe LDH to Co9S8, and lower the energy barriers of intermediates for the OER, leading to enhanced electrocatalytic activity. Meanwhile, the urchin-like hollow structure with nanopores and super-hydrophilicity can provide desired structural stability, facilitate ion penetration and release bubbles, improving the accessibility of active sites and thereby boosting OER catalytic performance. This work provides a viable route to develop high performance electrocatalysts for the OER.

Catalytic oxidation reaction using green oxidants plays an important role in modern chemical engineering; however, the in situ generated active species and the related catalytic mechanism need to be understood in depth. For this purpose, Cr-substituted aluminoborate Cr-PKU-8 catalysts were synthesized and applied as recyclable heterogeneous catalysts for the oxidation of aliphatic and aromatic alcohols using tert-butylhydroperoxide (TBHP). Both high efficiency and selectivity (>99%) were achieved during the dehydrogenation of various sec-alcohols into acetone in H2O solvent medium. From the analyses using isotopic tracer, molecular probe and cyclic voltammetry strategies, the chromium ions were observed to undergo a Cr3+–Cr2+–Cr3+ redox cycle. DFT calculations suggest that t-BuOO* is more energetically favourable for hydrogen abstraction from sec-alcohol than t-BuO*, and probably acts as the key active species. Accordingly, the reaction scheme was proposed to interpret the catalytic process based on the observed results.

Silicon carbide (SiC)-based ceramic matrix composites (CMCs) are utilized for their refractory properties in the aerospace industry. The composition and structure of these materials are crucial to maintaining the strength, toughness, oxidation, and creep resistances that are desired of silicon carbide. This work analyzes the chemical composition of the matrix in batches of SiC/SiC (silicon carbide fiber-reinforced silicon carbide matrix) minicomposites that are processed by chemical vapor infiltration of the BN interphase and SiC matrix on single Hi-Nicalon Type S fiber tows using a range of processing parameters. The analysis was performed here to investigate the potential causes of variation in matrix tensile strength in the various batches of minicomposites. Six different morphologies present in the silicon carbide matrix were observed: smooth, nodular, rough nodular, bumpy, nucleated, and plate-like. It was found that high-matrix tensile strength minicomposite batches contained solely the smooth morphology, while low-matrix tensile strength minicomposite batches contained a variety of other morphologies. FIB/TEM was used to study the atomic and crystal character of each individual morphology. Smooth SiC is oriented by the (111) planes and is primarily SiC, while the other morphologies are randomly oriented and contain significant oxygen. These results match the tensile strength tests, which pointed to smooth SiC as the strongest matrix material.

Hydrogen evolution reaction (HER) is the cathodic reaction in electrochemical water splitting that produces H2 in a renewable pathway, primarily to be used in fuel cells. K-OMS-2, a manganese octah...

Herein, we report syntheses of microporous and mesoporous mixed metal oxides templated via an anionic surfactant. The effects of acid treatment, solvent type, and the amount of metal incorporation ...

Effective methane utilization for either clean power generation or value-added chemical production has been a subject of growing attention worldwide for decades, yet challenges persist mostly in re...

Silicon carbide coated onto Hi-Nicalon Type S fiber is of great interest to the aerospace industry. This work focuses on tuning the reaction parameters of atmospheric pressure SiC CVI using CH3SiCl...

Improving charge transfer is the key to the performance of non-noble metal semiconductor-based surface enhanced Raman scattering (SERS) substrates. In this work, the O-incorporated 1T-MoS2 nanosheets with rich sulfur defects (ID-MoS2) are obtained by simple calcination of 1T-MoS2 nanosheets in air atmosphere. Using rhodamine 6G (R6G) as typical probe molecules, ID-MoS2 nanosheets show ultrahigh Raman enhancement effects with an enhancement factor of 1.24 × 107 due to sulfur defects and O incorporation in the 1T-MoS2 lattice. First-principle density functional theory calculations suggest that the existence of sulfur defects and O incorporation significantly increase the Fermi energy level (Ef) and electronic density of states of ID-MoS2. Moreover, O incorporation can enhance the interactions between the substrate and the adsorbed molecules through electrostatic and hydrogen bonding. All these improve the charge transfer resonance and result in the remarkable SERS activity of ID-MoS2 nanosheets. This is the first study on the increasing SERS performance of semiconductor substrates by simultaneously employing defect and dopant incorporation. This study provides an approach to optimize the performance of semiconductor-based SERS substrates.

Methylammonium lead iodide (CH3NH3PbI3, MAPbI3) belongs to the group of organic–inorganic halide perovskites (OIHPs) that exhibit exceptional electrical and optical behavior suitable for photovolta...

Nitrosamine metabolites resulting from cigarette smoking and E-cigarette (E-cig) vaping cause DNA damage that can lead to genotoxicity. While DNA adducts of metabolites of nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-nitrosonornicotine (NNN) are well-known tobacco-related cancer biomarkers, only a few studies implicate NNN and NNK in DNA oxidation in humans. NNK and NNN were found in the urine of E-cigarette users who never smoked cigarettes. This paper proposes the first chemical pathways of DNA oxidation driven by NNK and NNN metabolites in redox reactions with Cu2+ and NADPH leading to reactive oxygen species (ROS). A microfluidic array with thin films of DNA and metabolic enzymes that make metabolites of NNN and NNK in the presence of Cu2+ and NADPH was used to estimate relative rates of DNA oxidation. Detection by electrochemiluminescence (ECL) employed a new ECL dye [Os(tpy-benz-COOH)2]2+ that is selective for and sensitive to the primary DNA oxidation product 8-oxo-7,8-dihydro-2-deoxyguanosine (8-oxodG) in DNA. Enzyme-DNA films on magnetic beads were used to produce nitrosamine metabolites that enter ROS-forming redox cycles with Cu2+ and NADPH, and liquid chromatography-mass spectrometry (LC-MS) was used to quantify 8-oxodG and identify metabolites. ROS were detected by optical sensors. Metabolites of NNK and NNN + Cu2+ + NADPH generated relatively high rates of DNA oxidation. Lung is the exposure route in smoking and vaping, human lung tissue contains Cu2+ and NADPH, and lung microsomal enzymes gave the highest rates of DNA oxidation in this study. Also, E-cigarette vapor contains 6-fold more copper than that in cigarette smoke, which could exacerbate DNA oxidation.

Thin film coatings of titanium carbide (TiC) were deposited onto carbon fibers via atmospheric pressure chemical vapor infiltration (CVI) using TiCl4, CH4, and H2 gases. Three CVI parameters were optimized to obtain high quality coatings: temperature, total gas flow rate, and H2/CH4 flow ratio. Scanning electron microscopy was used to assess the quality and morphology of the coatings, including the roughness, uniformity, fiber coverage, and fiber adhesion. The temperature was optimized to 900 °C, which yielded complete fiber coverage with minimal fiber bridging and good adhesion. Minimizing the total gas flow rate to 37.5 standard cubic centimeters per minute reduced the roughness of the TiC coating. Finally, maximizing the ratio of H2/CH4 to 4:1 was optimal for all coating qualities. Selected area electron diffraction confirmed the presence of crystalline TiC. A combination of transmission electron microscopy and fiber tow tensile testing revealed that the outer layer of carbon fiber becomes damaged by the CVI process, causing loss of strength. To circumvent this surface degradation, it is necessary to protect the fibers with a pyrolytic carbon interphase coating before depositing TiC. This method of depositing TiC onto carbon fibers proves to be competitive in terms of coating quality, deposition temperature, reaction time, and fiber strength compared to other TiC deposition methods including reactive-CVI and molten salt synthesis.

A novel approach is introduced to synthesize multivalent, mesoporous metal oxides with high surface area using zero oxidation state precursors. Herein, the synthesis and comprehensive characterization of the metal oxides of s block, p block, transition metal, and lanthanide series elements are reported. Some of the synthesized metal oxides showed mixed phases at relatively low temperatures which is advantageous over single-phase materials. The initial metal dissolution process allows this method to be extended to any metal in the periodic table and metal alloys. A green and highly efficient catalytic sp2-sp2 C–C coupling reaction is carried out using high surface area MoO3 (142 m2/g) where complete conversion is observed within one hour.