Search

The green electrochemical synthesis of ammonia (NH3) through solid electrolysis has been intensively investigated. This research reported an improvement of NH3 production rate using in situ exsolution of ruthenium (Ru) atoms into lanthanum strontium chromium ferrite perovskite (LaxSr1−xCryFe1−yO3−δ) catalyst. The in situ Ru exsolution was achieved by reducing the optimized stoichiometric La0.33Sr0.67Cr0.33Fe0.52Ru0.15O3−δ (LSCrFRu) powders obtained in 10‐vol% H2/Ar at 800°C for 1.0 h. These Ru nanoparticles (NPs) were embedded on the surface of the LSCrFRu matrix, evenly distributed with a size varying from 4.4 ± 0.5 nm. With the exsolution of Ru atoms, greater oxygen vacancies were formed in ex‐LSCrFRu and gadolinium‐doped ceria (GDC) composite than those in LSCrF‐GDC electrocatalyst, beneficial to N2 gas adsorption and triple bond cleavage. These Ru‐modified LSCrFRu‐GDC catalysts showed a synthesis rate of 4.73 × 10−10 mol s−1 cm−2 at 550°C under 1.6 V, doubling the rate using LSCrF‐GDC catalyst. The improved ammonia synthesis kinetic is mainly attributed to embedded Ru NPs and the increased oxygen vacancies formed during the in situ exsolution process. More active sites and higher activity for H2O and N2 adsorption and activation collectively advanced facile transportation of O2− that further promotes the cleavage of covalent bonds in H2O, providing more H+ for the hydrogenation in the nitrogen reduction reaction. This research will open a new paradigm for the electrochemical synthesis of ammonia with mitigating the drawbacks of traditional NH3 production. [ABSTRACT FROM AUTHOR]

To drive the next 'technical revolution' towards commercialization, we must develop sustainable energy materials, procedures, and technologies. The demand for electrical energy is unlikely to diminish over the next 50 years, and how different countries engage in these challenges will shape future discourse. This perspective summarizes the technical aspects of nanomaterials' design, evaluation, and uses. The applications include solid oxide fuel cells (SOFCs), solid oxide electrolysis cells (SOEC), microbial fuel cells (MFC), supercapacitors, and hydrogen evolution catalysts. This paper also described energy carriers such as ammonia which can be produced electrochemically using SOEC under ambient pressure and high temperature. The rise of electric vehicles has necessitated some form of onboard storage of fuel or charge. The fuels can be generated using an electrolyzer to convert water to hydrogen or nitrogen and steam to ammonia. The charge can be stored using a symmetrical supercapacitor composed of tertiary metal oxides with self-regulating properties to provide high energy and power density. A novel metal boride system was constructed to absorb microwave radiation under harsh conditions to enhance communication systems. These resources can lower the demand for petroleum carbon in portable power devices or replace higher fossil carbon in stationary power units. To improve the energy conversion and storage efficiency, we systematically optimized synthesis variables of nanomaterials using artificial neural network approaches. The structural characterization and electrochemical performance of the energy materials and devices provide guidelines to control new structures and related properties. Systemic study on energy materials and technology provides a feasible transition from traditional to sustainable energy platforms. This perspective mainly covers the area of green chemistry, evaluation, and applications of nanomaterials generated in our laboratory with brief literature comparison where appropriate. The conceptual and experimental innovations outlined in this perspective are neither complete nor authoritative but a snapshot of selecting technologies that can generate green power using nanomaterials. [ABSTRACT FROM AUTHOR]

Fundamental research has been carried out to define optimal “green” synthesis conditions for the production of titania (TiO2) and silver (Ag) nanocomposites (TANCs) ranging from 12.7–22.8 nm in diameter. A bottom-up colloidal approach was employed to accurately control TANC monodispersity and composition. TANCs were found to be effective at inactivating Escherichia coli(E. coli) in water. The presence of Ag in the nanocomposites induced a decrease in TiO2band gap energy, which favoured valence to conduction band electron transfer and allowed for electron excitation using visible light. Aggregation of ultra-fine particles was prevented through the use of a long-chain polymer as evidenced by electrophoretic mobility studies. The TANCs catalyzed oxidation of bacterial membranes and cell death or disinfection. Theoretically, the TANC mode of E. colidisinfection is viawater photolysis, which results in production of hydroxyl radicals and hydrogen peroxide. These interact with the outer membrane polysaccharides and lipids, leading to lipid peroxidation, membrane weakening and resulted in cell death. Our overarching goals were to optimize the variables involved in TANC “green” synthesis and to characterize its nanostructure. High resolution (HR) transmission and scanning electron microscopic (TEM and SEM) studies demonstrated that TANCs were highly crystalline and mono-dispersive. Elemental composition of Ag and Ti, as measured by X-ray energy dispersive (EDS) and X-ray photoelectron spectroscopy (XPS) confirmed sample purity. Ultraviolet-visible (UV-VIS) spectroscopy showed that the energy band-gap of Ag modified TiO2was in the visible range. [ABSTRACT FROM AUTHOR]

A tailored chitosan crosslinked isovanillin (CCIV) polymeric adsorbent generated using homogeneous catalysis was applied for the extraction and removal of direct yellow dye 50 (DY 50), through rapid adsorption due to an electrostatic attraction between the dye molecules and CCIV frameworks. The removal efficiency of DY 50 was systematically investigated to determine the effect of contact time, incubation temperature, pH of the solution, initial dye concentration, and adsorbent mass. The adsorbent also appeared to exert a novel tribocatalytic energy effect for dye decompositions, which is confirmed through comparison of removal from agitation (friction) which is thought to promote the generation of reactive oxygen species. The DY 50 adsorption was almost instantaneous, where up to 83.3% of the initial DY 50 load was removed within and up to 10 min, and then to 90–97.9% by physicochemical adsorption after 45–180 min using 0.05 g of CCIV bio sorbents under ambient temperature. The variations of DY 50 initial concentrations, contact time, and temperatures allowed us to implement three isotherm models, kinetics, and thermal dynamic studies. The comparison of adsorption equilibrium data of DY 50 on the CCIV surfaces was obtained from Langmuir, Freundlich, and Temkin isotherms models, indicating the "monomer to bilayer" is favorable through van der Waals interaction. Validation of the kinetic models was obtained through the ratio of 95% and 5% extraction time (t 95 /t 5 = 19.42) and residual sum of squares (RSS < 0.01). These statistical tolerance analyses confirmed the kinetics was consistent with a pseudo-second-order adsorption kinetic profile. The thermodynamic state functions and operational parameters (Δ H , Δ S , and Δ G) were calculated, suggesting DY 50 adsorption underwent a spontaneous and exothermic process. [ABSTRACT FROM AUTHOR]

Water remediation using semiconductor photocatalysts under visible light (VL) irradiance appears as a more sustainable technology option due to the greater penetration depth. Consequently, the overall band spectrum of VL has received significant attention to providing solutions to secure clean water resources over the past few decades. This research developed an innovative approach to enhancing the visible light susceptibility of semiconductor-based photocatalytic composites Ag 10 Si 4 O 13 /TiO 2 (ASO/TO). The intrinsic properties of TO and electron donor ability of ASO lend synergistically to the generation of a narrow bandgap semiconductor. A feasible wet-chemistry method was found to engineer the electronic properties of ASO/TO under VL for rapid decolorization of methylene blue (MB). Inhibition experiments with several agents confirmed that the decolorization proceeds through the generation of hydroxyl radical species assisted by hole carrier generation at the ASO junction. The rate of MB decomposition followed a pseudo-first-order kinetic profile (98.2% within 35 mins under ambient conditions with 5 ppm of 2:1 ASO/TO and 20 ppm of MB). The XRD/XPS spectroscopic analysis confirms the electronic polarization of distorted SiO 4 tetrahedral units coordinated to Ag-O, forming a double dumbbell double-helical structure. The staggered bandgap of these composite photocatalysts is associated with the Ag-Ag d10/sp hybridization and dispersive conduction band. At the same time, the 2p orbitals of TiO 2 showed a less dispersive band due to the availability of d -orbitals. The generated Ag 10 Si 4 O 13 (ASO) based ferroelectric materials allow amplifying its frequency due to internal polarization along the c-axis. The electrochemical evaluation also showed that the interface charge transfer resistance was lowered relative to TiO 2 , facilitating the efficacy of photocatalytic reactivity, where the generation of holes as charge carriers was the rate-limiting step. The novel nano-engineering strategy providing highly active photocatalysis can open new horizons for VL applications. [Display omitted] • Unique d10 and sp/p configurations in its electronic structure, yield high photocatalysis. • Ferroelectric p-block photocatalyst fabrication, by bandgap engineering. • The efficient charge due to electric field in ASO from distorted SiO 4 chain structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel SOEC with oxygen ionic electrolyte was designed for ammonia production. • Macro-porous structure LSCrF-GDC cathodes were fabricated using the ball milling method. • The effects of Fe amount and cathode thickness on R p was investigated. • The r N H 3 reached 3.0 × 10−10 mol s-1 cm-2 at 600 °C under 1.8 V applied voltage. This study indicated that joining two different types of solid-state materials, co-doped lanthanum strontium chromium ferrite (LSCrF, La 0.33 Sr 0.67 Cr 1-x Fe x O 3-δ) perovskite oxide, and gadolinium-doped ceria (GDC, Ce 0.9 Gd 0.1 O 2-δ) fluorite, yielded series of unique electrocatalytic composites, enabling a green production of ammonia (NH 3, (g)) via nitrogen (N 2, (g)) and steam (H 2 O, (g)) reaction at the cathode compartment. An optimized ball milling approach was implemented to produce the cathodic composites with different formulations to respond to the environmental stimuli changes of operational temperature and applied voltage. The solid oxide electrolysis cells (SOECs) were then assembled and used for NH 3 production with optimized synthesis and electrochemical measurement variables. As a result, these engineered cathodic catalysts maximized the efficacy of NH 3 production due to the formation of oxygen vacancies, high interactivity between catalysts and reactants, and gas channeling through the macro-porous structure. To tune the macro-porous structure of the cathodic composites, the group invented an in-situ templating using a porogen (PMMA, polymethylmethacrylate, (C 5 O 2 H 8) n) with a controllable size to facilitate gas diffusion and adsorption along with the interfaces of phase boundaries. Electrochemical analyses such as the measurement of impedance demonstrated that the macro-porous structured (LSCrF-GDC) electrode exhibited superior electrocatalytic kinetics. Consequently, the formation rate of NH 3 was found to achieve 3.0 × 10−10 mol⋅s-1⋅ cm-2 when the SOEC technology was implemented under an applied voltage of 1.8 V and operating temperature at 600 °C. The mechanistic study of electrochemical performance and interactivity between cathodic catalysts and reactants indicated that an optimized NH 3 production pathway was carried out below thermoneutral enthalpy to achieve high efficiency. This goal was achieved through adjustment of the ratio between the enthalpy flow of produced hydrogen and the input of electrical power. The contribution of this study lies in the optimized methodology to enhance interactive electrocatalysis applied for the green synthesis of ammonia. [ABSTRACT FROM AUTHOR]

Degradation efficiency of tetracycline was improved using reduced graphene oxide coordinated titania photocatalyst under different irradiations. Mechanistic study indicated a biphasic model was followed with the holes as dominant factor to directly oxidize tetracycline. • Structured TiO 2 -RGO-TiO 2 catalyst was produced using a cost sol-gel method. • Graphene scaffolding provided improved efficiency for photodegradation of TCH. • Generation of surface defeats resulted in hole creation for photodegradation of TCH. • Another dominant route for photodegradation of TCH was via reactive oxygen species. The compound tetracycline hydrochloride (TCH) is an antibiotic used in the veterinary and medical application, however, it's over usage and accidental release into riverine and estuaries raising up serious threats to the ecology, environment and public health. This study focused on developing a low-cost catalyst to photodegrade TCH. Different formulations of TiO 2 photocatalysts scaffolded with reduced graphene (denoted as TiO 2 -RGO-TiO 2) were produced using a cost-effective sol-gel method. The mesoporous structured TiO 2 -RGO-TiO 2 was tuned using citric acid as a complexing agent, Pluronic P-123 as a grafting agent and graphene oxide (GO) as structural "core" to guide the TiO 2 growth. Our findings documented that the TiO 2 -RGO-TiO 2 catalysts displayed high degradation efficiency towards TCH. This efficiency was determined to be improved by 22.8% under ultraviolet light and 32.80% under simulated solar energy within 2 h exposure respectively, relative to catalysis by TiO 2 alone. It was found that 6 wt percent GO resulted in the highest degradation percentage (˜ 94%) due to the synergistic effects of inhibition of the electron-hole (e− and h+) recombination and improvement of effective reactive sites. The holes were found to the major factor in facilitating the photocatalytic degradation of TCH (75.4%), while the reactive oxygen species (ROS) accounted for the remaining 24.63%. Another factor to contribute to the superior performance of the TiO 2 -RGO-TiO 2 compared to TiO 2 alone lies in the decrease of the band gap energy of TiO 2 from 3.20 to 2.87 eV upon introduction of reduced GO. [ABSTRACT FROM AUTHOR]