Synthesis and Characterization of Stable Cu-Pt Nanoparticles under Reductive and Oxidative Conditions.

We report a synthesis method for highly monodisperse Cu-Pt alloy nanoparticles. Small and large Cu-Pt particles with a Cu/Pt ratio of 1:1 can be obtained through colloidal synthesis at 300 °C. The fresh particles have a Pt-rich surface and a Cu-rich core and can be converted into an intermetallic phase after annealing at 800 °C under H2. First, we demonstrated the stability of fresh particles under redox conditions at 400 °C, as the Pt-rich surface prevents substantial oxidation of Cu. Then, a combination of in situ scanning transmission electron microscopy, in situ X-ray absorption spectroscopy, and CO oxidation measurements of the intermetallic CuPt phase before and after redox treatments at 800 °C showed promising activity and stability for CO oxidation. Full oxidation of Cu was prevented after exposure to O2 at 800 °C. The activity and structure of the particles were only slightly changed after exposure to O2 at 800 °C and were recovered after re-reduction at 800 °C. Additionally, the intermetallic CuPt phase showed enhanced catalytic properties compared to the fresh particles with a Pt-rich surface or pure Pt particles of the same size. Thus, the incorporation of Pt with Cu does not lead to a rapid deactivation and degradation of the material, as seen with other bimetallic systems. This work provides a synthesis route to control the design of Cu-Pt nanostructures and underlines the promising properties of these alloys (intermetallic and non-intermetallic) for heterogeneous catalysis.

Arsenic adsorption study in acid mine drainage using fixed bed column by novel beaded adsorbent.

The downflow fixed-bed column adsorption-desorption of arsenic by the beaded coal mine drainage sludge-Youngdong (BCMDS-YD) adsorbent was experimentally studied. The specific surface area of BCMDS-YD synthesized using inorganic binding was 178 m2 g-1, and the pHIEP was 5.32. The XRD analysis revealed that it was composed of calcite and schwertmannite. As a result, an increase in the inflow rate resulted in an earlier column exhaustion. The breakthrough curve indicated that a smaller adsorbent particle size and lower influent pH prolonged the column life span. Thomas logistic model was applied to fit the breakthrough curve by linear and nonlinear regression. Under the condition of an influent flow rate of 2.65 mL min-1 (EBCT 40 min), an influent arsenic average concentration of 0.5-1 mg L-1, an influent pH of 7.6, an adsorbent mass of 100 g, an adsorbent grain size of 1.40-1.70 mm, and an operating temperature of 25 °C, the equilibrium adsorption capacity reached 4.56 mg g-1. The mechanism of arsenic adsorption is adsorption and precipitation. As a result of the adsorbent reuse experiment, it was judged that it could be reused with good results in all three cycle experiments. The cost of treating arsenic with the BCMDS-YD adsorbent was 0.145 $ per m-3. The results of this study show examples of sustainable development concepts in mining drainage, and BCMDS-YD can effectively remove arsenic and other heavy metals from acid mine drainage.

Unveiling the key factor for the phase reconstruction and exsolved metallic particle distribution in perovskites.

To significantly increase the amount of exsolved particles, the complete phase reconstruction from simple perovskite to Ruddlesden-Popper (R-P) perovskite is greatly desirable. However, a comprehensive understanding of key parameters affecting the phase reconstruction to R-P perovskite is still unexplored. Herein, we propose the Gibbs free energy for oxygen vacancy formation in Pr0.5(Ba/Sr)0.5TO3-δ (T = Mn, Fe, Co, and Ni) as the important factor in determining the type of phase reconstruction. Furthermore, using in-situ temperature & environment-controlled X-ray diffraction measurements, we report the phase diagram and optimum 'x' range required for the complete phase reconstruction to R-P perovskite in Pr0.5Ba0.5-xSrxFeO3-δ system. Among the Pr0.5Ba0.5-xSrxFeO3-δ, (Pr0.5Ba0.2Sr0.3)2FeO4+δ - Fe metal demonstrates the smallest size of exsolved Fe metal particles when the phase reconstruction occurs under reducing condition. The exsolved nano-Fe metal particles exhibit high particle density and are well-distributed on the perovskite surface, showing great catalytic activity in fuel cell and syngas production.

Two-Dimensional Perovskite Crystals Formed by Atomic Layer Deposition of CaTiO3 on γ-Al2O3.

CaTiO3 films with an average thickness of 0.5 nm were deposited onto γ-Al2O3 by Atomic Layer Deposition (ALD) and then characterized by a range of techniques, including X-ray Diffraction (XRD) and High-Resolution, Transmission Electron Microscopy (HRTEM). The results demonstrate that the films form two-dimensional crystallites over the entire surface. Lattice fringes from HRTEM indicate that the crystallites range in size from 5 to 20 nm and are oriented in various directions. Films of the same thickness on SiO2 remained amorphous, indicating that the support played a role in forming the crystallites.

Enhancing Thermocatalytic Activities by Upshifting the d-Band Center of Exsolved Co-Ni-Fe Ternary Alloy Nanoparticles for the Dry Reforming of Methane.

Dry reforming of methane (DRM) is a feasible solution to address the reduction of greenhouse gases stipulated by the Paris Climate Agreement, given that it adds value by converting trivial gases, CO2 and CH4 , simultaneously into useful syngas. However, the conventional Ni catalyst undergoes deactivation due to carbon coking and particle agglomeration. Here we demonstrate a highly efficient and durable DRM catalyst: exsolved Co-Ni-Fe ternary alloy nanoparticles on the layered perovskite PrBaMn1.7 Co0.1 Ni0.2 O5+δ produced by topotactic exsolution. This method readily allows the generation of a larger number of exsolved nanoparticles with enhanced catalytic activity above that of Ni monometallic and Co-Ni bimetallic particles. The enhancement is achieved by the upshift of the d-band center of Co-Ni-Fe relative to those of Co-Ni and Ni, meaning easier charge donation to the adsorbate. Furthermore, the exsolved catalyst shows exceptional stability, with continuous DRM operation for about 350 hours.

Resistance-Breaking Tomato Spotted Wilt Virus Variant that Recently Occurred in Pepper in South Korea is a Genetic Reassortant.

Tomato spotted wilt virus (TSWV) is a destructive viral pathogen in various crops, including pepper. Although the single dominant gene Tsw has been utilized in pepper breeding to confer resistance to TSWV, the occurrence of TSWV variants that overcome Tsw-mediated resistance has been reported in various countries after several years of growing resistant cultivars. In this study, we determined the complete genome sequence of a resistance-breaking TSWV variant (TSWV-YI) that recently emerged in pepper in South Korea. TSWV-YI infected all of the resistant pepper cultivars tested. The phylogenetic and recombination analyses of the complete TSWV-YI genome sequence showed that it is a reassortant that acquired its L and M RNA segments from the existing South Korean TSWV population and its S RNA in an isolate from another country. Given that TSWV-YI is a resistance-breaking variant, it appears that reassortment of the S RNA led to the emergence of this variant that breaks the Tsw gene in pepper grown in South Korea. Our results suggest that resistance-breaking TSWV variants are a potential threat to pepper production in South Korea and that strategies to manage these variants should be developed to ensure sustainable pepper production.

Rare earth real wastewater treatment by pilot scale using new concept continuous treatment process.

Rare earth (RE) containing radioactive species and a variety of toxic pollutants The treatment of real wastewater is very important for environmental protection. In this study, a new concept of continuous process consisting of precipitation, adsorption, and oxidation was developed without the use of chemicals. In the sedimentation step, waste oyster shell(WOS) and a PE tube diffuser(PE250) containing Na2S (PECa/S), PECa/S were prepared, which were used to precipitate heavy metals with a removal efficiency of 97% or more. In the adsorption step, fluorine (F), arsenic (As), and thorium (Th) were precipitated and removed when heavy metals were removed using coal mine drainage sludge (CMDS) and an adsorbent (PUCMDS) made of polyurethane (PU). Running a semi and pilot scale continuous process using PECa/S, PUCMDS and O3/HC systems resulted in a semi and pilot scale operating period of 120 and 62 days, and 60.26, 797.84, 46.94, 78.62 g, and 7.120 kg and 266.35, 42556.8, 191.95, 3108.43 g and 629.84 kg for As, F, Th, Pb and CODcr has been removed respectively. In addition, the removal efficiencies of As, F, Th, Pb and CODcr were 99.75, 99.98, 93.60, 99.99, and 88.82%, respectively, when treating real RE wastewater using the pilot scale system. Without the use of agitated reactors and regulators, the new concept of continuous process can effectively treat RE real wastewater, and the quality of the process outlet has met the pollutant limits recommended by EPA and China for irrigation.

Interpreting complex geochemistry of groundwater in a coastal paddy field near a mine using isotopic signatures of sulfate and water.

In the area around the abandoned Seoseong mine, South Korea, coastal paddy fields undergo seawater intrusion and possible sulfate reduction. Here, channel water is used for irrigation, fertilizers are applied, and some paddy fields are contaminated by mining activities, which subsequently contaminate a groundwater well with arsenic. In this complex environment, the isotopic signatures of sulfate and water in water samples were assessed to reveal sources of sulfate, water and processes in the groundwater system. Sulfur and oxygen isotopes of sulfate indicated three major sources of sulfate-namely the mine including tailings, intruded seawater, and fertilizer-and an additional process of sulfate reduction. The sulfate sources and sulfate reduction could be distinguished more clearly after the variable of sulfate contribution from seawater was introduced. According to the analysis results of hydrogen and oxygen isotopes of water, areas affected by irrigation from a reservoir and its downstream channel were distinguished, possibly because the reservoir underwent evaporation effect. A schematic diagram was proposed to explain complex sources and processes in the studied area. Especially, a suggested plot of δ34SSO4 against the sulfate contribution from seawater [f(SO42-seawater)] could efficiently differentiate various contamination sources (e.g., mining activity and fertilizer) and processes (e.g., seawater intrusion and sulfate reduction) in coastal aquifer.

Determination of soil contamination sources in mining area using Zn/Cd ratios with mobile Cd.

Paddy fields near metalliferous mining area are sometimes contaminated by tailings or mine water. In the contaminated paddy fields around the abandoned Seoseong mine, South Korea, groundwater, surface water, and soil samples were assessed to infer sources (tailings and/or mine water) of soil contamination. Major contaminants in the soil included As and Pb which were not detected in the adit water. Moreover, δ34SSO4 values of groundwater at contaminated downstream paddy fields were higher than those of ground and surface water in the mining area, which indicated water-derived contamination is not evident. The Zn/Cd ratios of soil were assessed to verify the source (tailings) of soil contamination. Plots of the Zn/Cd ratio against Zn and As contents showed that soil samples contaminated from tailings had Zn/Cd ratios (108-247) which were similar with the Zn/Cd range of the tailings. In contrast, the ratios of the soil samples were different from the Zn/Cd range of contaminated water samples. The Zn/Cd ratios were determined using 0.1 M HCl-extractable Cd, and the fraction of 0.1 M HCl-extractable Cd in aqua regia-digestible Cd increased with increasing aqua regia-digestible Cd content. These observations suggest that Zn/Cd ratios in contaminated soil are primarily controlled by 0.1 M HCl-extractable Cd, possibly due to the greater exchangeability of 0.1 M HCl-extractable Cd than that of total Cd. This suggests that Zn/Cd ratios determined using 0.1 M HCl-extractable Cd can be especially sensitive and useful for determining sources of soil contamination in mining areas such as tailings or contaminated water.

Arsenic adsorption on two types of powdered and beaded coal mine drainage sludge adsorbent.

The aim of this study was to evaluate the performance of a new adsorbent in terms of beading the sludge generated from coal mine drainage or arsenic removed from water is treated by electro-purification (EP) and chemical-precipitation (CP) methods. Batch experiments were conducted to study the influence of experimental parameters such as pH and temperature, as well as the mechanism of arsenic adsorption with the new adsorbent. The porosity of coal mine drainage sludge (CMDS)-beaded adsorbent made of chitosan and alginate was optimized by adding NaHCO3 powder to generate CO2 gas during the preparation process. Two types of adsorbents, beaded EP Najeon CMDS (BCMDSEP-NJ) and beaded CP Yeongdong CMDS (BCMDSCP-YD), were prepared by heating. The specific surface areas of the powdered adsorbents CMDSEP-NJ and CMDSCP-YD were 104 and 231 m2 g-1, respectively. The prepared beaded adsorbents BCMDSEP-NJ and BCMDSCP-YD had good porosity and specific surface areas of 16.8 and 21.2 m2 g-1, respectively. The X-ray diffraction results showed that the structure was goethite (aragonite) and schwertmannite. The pseudo second-order, intra-particle, and Langmuir models were used to explain the adsorption process. The qmax values of As(III) with BCDMSEP-NJ and BCMDSCP-YD adsorbents are 4.31 and 4.58 mg g-1, respectively and those of AS(V) are 9.31 and 10.93 mg g-1, respectively. The adsorption capacity for As(III) increased with increasing pH, whereas that for As(V) decreased. The activation energy was 8 kJ mol-1 or more. The mechanism of adsorption of arsenic using a beaded adsorbent was chemical adsorption followed by diffusion. The results of the present study suggest that new adsorbents can be effectively utilized for arsenic removal from water.

Estimates of particulate matter inhalation doses during three-dimensional printing: How many particles can penetrate into our body?

Harmful emissions including particulates, volatile organic compounds, and aldehydes are generated during three-dimensional (3D) printing. Ultrafine particles are particularly important due to their ability to penetrate deep into the lung. We modeled inhalation exposure by particle size during 3D printing. A total of six thermoplastic filaments were used for printing under manufacturer's recommended conditions, and particle emissions in the size range between 10 nm and 10 µm were measured. The inhalation exposure dose including inhaled and deposited doses was estimated using a mathematical model. For all materials, the number of particles between 10 nm and 1 µm accounted for a large proportion among the released particles, with nano-sized particles being the dominant size. More than 1.3 × 109 nano-sized particles/kgbw/g (95.3 ± 104.0 ng/kgbw/g) could be inhaled, and a considerable amount was deposited in respiratory regions. The total deposited dose in terms of particle number was 3.1 × 108 particles/kgbw/g (63.6% of the total inhaled dose), and most (41.3%) were deposited in the alveolar region. The total mass of particles deposited was 19.8 ± 16.6 ng/kgbw/g, with 10.1% of the total mass deposited in the alveolar region. Given our findings, the inhalation exposure level is mainly determined by printing conditions, particularly the filament type and manufacturer-recommended extruder temperature.

Metal Exsolution to Enhance the Catalytic Activity of Electrodes in Solid Oxide Fuel Cells.

Exsolution is a novel technology for attaching metal catalyst particles onto ceramic anodes in the solid oxide fuel cells (SOFCs). The exsolved metal particles in the anode exhibit unique properties for reaction and have demonstrated remarkable stabilities under conditions that normally lead to coking. Despite extensive investigations, the underlying principles behind exsolution are still under investigation. In this review, the present status of exsolution materials for SOFC applications is reported, including a description of the fundamental concepts behind metal incorporation in oxide lattices, a listing of proposed mechanisms and thermodynamics of the exsolution process and a discussion on the catalytic properties of the resulting materials. Prospects and opportunities to use materials produced by exsolution for SOFC are discussed.

Probing One-Dimensional Oxygen Vacancy Channels Driven by Cation-Anion Double Ordering in Perovskites.

Visualizing the oxygen vacancy distributions is highly desirable for understanding the atomistic oxygen diffusion mechanisms in perovskites. In particular, the direct observation of the one-dimensional oxygen vacancy channels has not yet been achieved in perovskites with dual ion (i.e., cation and anion) ordering. Here, we perform atomic-resolution imaging of the one-dimensional oxygen vacancy channels and their structural dynamics in a NdBaCo2O5.5 double perovskite oxide. An in situ heating transmission electron microscopy investigation reveals the disordering of oxygen vacancy channels by local rearrangement of oxygen vacancies at the specific temperature. A density functional theory calculation suggests that the possible pathway of oxygen vacancy migration is a multistep route via Co-O and Nd-Ov (oxygen vacancy) sites. These findings could provide robust guidance for understanding the static and dynamic behaviors of oxygen vacancies in perovskite oxides.

Highly active dry methane reforming catalysts with boosted in situ grown Ni-Fe nanoparticles on perovskite via atomic layer deposition.

With the need for more stable and active metal catalysts for dry reforming of methane, in situ grown nanoparticles using exsolution are a promising approach. However, in conventional exsolution, most nanoparticles remain underneath the surface because of the sluggish diffusion rate of cations. Here, we report the atomic layer deposition (ALD)-combined topotactic exsolution on La0.6Sr0.2Ti0.85Ni0.15O3-δ toward developing active and durable catalysts. The uniform and quantitatively controlled layer of Fe via ALD facilitates the topotactic exsolution, increasing finely dispersed nanoparticles. The introduction of Fe2O3 yields the formation of Ni-Fe alloy owing to the spontaneous alloy formation energy of -0.43 eV, leading to an enhancement of the catalytic activity for dry methane reforming with a prolonged stability of 410 hours. Overall, the abundant alloy nanocatalysts via ALD mark an important step forward in the evolution of exsolution and its application to the field of energy utilization.

In-situ local phase-transitioned MoSe2 in La0.5Sr0.5CoO3-δ heterostructure and stable overall water electrolysis over 1000 hours.

Developing efficient bifunctional catalysts for overall water splitting that are earth-abundant, cost-effective, and durable is of considerable importance from the practical perspective to mitigate the issues associated with precious metal-based catalysts. Herein, we introduce a heterostructure comprising perovskite oxides (La0.5Sr0.5CoO3-δ) and molybdenum diselenide (MoSe2) as an electrochemical catalyst for overall water electrolysis. Interestingly, formation of the heterostructure of La0.5Sr0.5CoO3-δ and MoSe2 induces a local phase transition in MoSe2, 2 H to 1 T phase, and more electrophilic La0.5Sr0.5CoO3-δ with partial oxidation of the Co cation owing to electron transfer from Co to Mo. Together with these synergistic effects, the electrochemical activities are significantly improved for both hydrogen and oxygen evolution reactions. In the overall water splitting operation, the heterostructure showed excellent stability at the high current density of 100 mA cm-2 over 1,000 h, which is exceptionally better than the stability of the state-of-the-art platinum and iridium oxide couple.

Evaluation of Hazardous Chemicals with Material Safety Data Sheet and By-products of a Photoresist Used in the Semiconductor-Manufacturing Industry.

BACKGROUND: The photolithography process in the semiconductor industry uses various chemicals with little information on their constitution. This study aimed to identify the chemical constituents of photoresist (PR) products and their by-products and to compare these constituents with material safety data sheets (MSDSs) and analytical results. METHODS: A total of 51 PRs with 48 MSDSs were collected. Analysis consisted of two parts: First, the constituents of the chemical products were identified and analyzed using MSDS data; second, for verification of the by-products of PR, volatile organic compounds were analyzed. The chemical constituents were categorized according to hazards. RESULTS: Forty-five of 48 products contained trade secrets in amounts ranging from 1 to 65%. A total of 238 ingredients with multiple counting (35 ingredients without multiple counting) were identified in the MSDS data, and 48.7% of ingredients were labeled as trade secrets under the Korea Occupational Safety and Health Act. The concordance rate between the MSDS data and the analytical result was 41.7%. The by-product analysis identified 129 chemicals classified according to Chemical Abstracts Service No., with 17 chemicals that are carcinogenic, mutagenic, and reprotoxic substances. Formaldehyde was found to be released from 12 of 21 products that use novolak resin. CONCLUSION: We confirmed that several PRs contain carcinogens, and some were not specified in the toxicological information in the MSDS. Hazardous chemicals, including benzene and formaldehyde, are released from PRs products as by-products. Therefore, it is necessary to establish a systematic management system for chemical compounds and the working environment.

Synergistic Coupling Derived Cobalt Oxide with Nitrogenated Holey Two-Dimensional Matrix as an Efficient Bifunctional Catalyst for Metal-Air Batteries.

Developing cost-effective, efficient bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the heart of metal-air batteries as a renewable-energy technology. Herein, well-distributed nanopolyhedron (NP) Co3O4 grown on iron (Fe) encapsulated in graphitic layers on a nitrogenated, porous two-dimensional (2D) structure, namely, a C2N matrix, (NP Co3O4/Fe@C2N), presents an outstanding bifunctional catalytic activity with a comparable overpotential and Tafel slope to those of benchmark Pt/C and IrO2. The rationally designed atomic configuration of Co3O4 on the C2N matrix has a well-controlled NP morphology with a (111) plane, leading to bifunctional activities for the ORR and OER. Interestingly, the specific interaction between the NP Co3O4 nanoparticles and the C2N matrix introduces synergistic coupling and changes the electronic configuration of Co atoms and the C2N framework. Benefiting from the synergistic coupling of Co3O4 with the C2N matrix, the NP Co3O4/Fe@C2N electrocatalyst exhibits exceptionally high stability and an even lower charge-discharge overpotential gap of 0.85 V at 15 mA cm-2 than that of the Pt/C+IrO2 catalyst (1.01 V) in Zn-air batteries. This work provides insights into the rational design of a metal oxide on a C2N matrix for bifunctional, low-cost electrochemical catalysts.

Cation-swapped homogeneous nanoparticles in perovskite oxides for high power density.

Exsolution has been intensively studied in the fields of energy conversion and storage as a method for the preparation of catalytically active and durable metal nanoparticles. Under typical conditions, however, only a limited number of nanoparticles can be exsolved from the host oxides. Herein, we report the preparation of catalytic nanoparticles by selective exsolution through topotactic ion exchange, where deposited Fe guest cations can be exchanged with Co host cations in PrBaMn1.7Co0.3O5+δ. Interestingly, this phenomenon spontaneously yields the host PrBaMn1.7Fe0.3O5+δ, liberating all the Co cations from the host owing to the favorable incorporation energy of Fe into the lattice of the parent host (ΔEincorporation = -0.41 eV) and the cation exchange energy (ΔEexchange = -0.34 eV). Remarkably, the increase in the number of exsolved nanoparticles leads to their improved catalytic activity as a solid oxide fuel cell electrode and in the dry reforming of methane.

Characterization and Control of Nanoparticle Emission during 3D Printing.

This study aimed to evaluate particle emission characteristics and to evaluate several control methods used to reduce particle emissions during three-dimensional (3D) printing. Experiments for particle characterization were conducted to measure particle number concentrations, emission rates, morphology, and chemical compositions under manufacturer-recommended and consistent-temperature conditions with seven different thermoplastic materials in an exposure chamber. Eight different combinations of the different control methods were tested, including an enclosure, an extruder suction fan, an enclosure ventilation fan, and several types of filter media. We classified the thermoplastic materials as high emitter (>1011 #/min), medium emitters (109 #/min -1011 #/min), and low emitters (<109 #/min) based on nanoparticle emissions. The nanoparticle emission rate was at least 1 order of magnitude higher for all seven filaments at the higher consistent extruder temperature than at the lower manufacturer-recommended temperature. Among the eight control methods tested, the enclosure with a high-efficiency particulate air (HEPA) filter had the highest removal effectiveness (99.95%) of nanoparticles. Our recommendations for reducing particle emissions include applying a low temperature, using low-emitting materials, and instituting control measures like using an enclosure around the printer in conjunction with an appropriate filter (e.g., HEPA filter) during 3D printing.