High Surface Concentration Research Articles

Porous PrFeO3 perovskite oxides derived from anionic cyanide-bridged framework for efficient persulfate activation: High surface B-site content and nonradical pathway

Rare-earth-based perovskite oxides are emerging as promising catalysts for peroxymonosulfate (PMS)-driven oxidation. In this study, a porous PrFeO3 perovskite oxide was developed utilizing a self-template strategy, where an anionic PrFe cyanide-bridged framework was constructed and served as the precursor. The self-template process of high-temperature conversion resulted in the creation of abundant mesoporous structures and a high surface concentration of B-site on the tubular PrFeO3 (PrFe500, calcinated at 500℃), thus ensuring the full exposure of active sites on its surface. As a result, PrFe500 exhibited superior catalytic activity for PMS-driven norfloxacin (NOR) degradation, with a low activation energy (Ea) of 17.62 kJ/mol. The main reactive oxygen species generated in the PrFeO3/PMS system for NOR degradation was identified as 1O2, originating from the activation of PMS on the surface active B-site (Fe) with the assistance of surface oxygen. The nonradical pathway not only circumvented the inhibitory effect of anions but also converted it into a positive promoting effect at high concentration of Cl−, enhancing the production of HOCl and 1O2 in the PrFe500/PMS system and thereby synergistically aiding in the degradation of NOR. This study presents a novel approach to constructing porous Pr-based perovskite oxides with exceptional activity for PMS-driven oxidation.

Effect of ocean dynamic processes on the temporal-spatial pattern of persistent organic pollutants (PCB-153 and BDE-47) in the shelf seas

Field observations of persistent organic pollutants (POPs) in shelf seas presented abnormal phenomena such as high-concentration patches in offshore areas and different vertical profiles of POPs at the same location. We assumed that these phenomena were associated with the presence of bottom cold water mass (BCWM) in shelf seas and used a hydrodynamic-ecosystem-POP coupled model to confirm this hypothesis. Based on model results, with the formation of BCWM during summer, POPs accumulated inside BCWM due to their transport across the thermocline by the sorption to sinking particles. With the intensification of vertical mixing during winter, the release of POPs from BCWM induced high-concentration patches of POPs on the surface layer. Meanwhile, the low water temperature in winter was favorable for the gas deposition of POPs, which led to high surface concentrations of POPs. Because the accumulation of POPs in BCWM depended on the sorption of dissolved POPs by particles, not all types of POPs accumulated in BCWM. Some POPs even accumulated at the sea surface above the BCWM due to large gaseous deposition and weak sorption by particles. Using this feature, we proposed a prediction function for the accumulation of POPs in BCWM.

Structure, orientation, and dynamics of per- and polyfluoroalkyl substance (PFAS) surfactants at the air-water interface: Molecular-level insights

HypothesisUnderstanding the intricate molecular-level details of toxic per- and polyfluoroalkyl substances (PFAS) partitioning to the air–water interface holds paramount importance in evaluating their fate and transport, as well as for finding safer alternatives for various applications, including aqueous film forming foams. The behavior of these substances at interfaces strongly depends on molecular architecture, chemistry, and concentration, which define molecular packing, self-assembly, interfacial diffusion, and the surface tension. SimulationsModeling of three PFAS surfactants, namely, longer-tail (perfluorooctanoate (PFOA)) and shorter-tail (perfluorobutanoate (PFBA) and 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy) propanoate (GenX)) has been conducted using atomistic molecular dynamics simulations. A systematic comparison between these representative PFAS of different sizes and structure reveals factors influencing their association behavior, mechanism of surface tension reduction, and interfacial mobility as a function of surface coverage. FindingsShorter-chain PFAS surfactants (GenX or PFBA) require lower surface coverage compared to longer chain (PFOA) PFAS to achieve the same decrease in surface tension. However, a higher concentration of GenX and PFBA is necessary in the bulk aqueous solution to achieve the same surface coverage as PFOA, due to their higher solubility in water. The PFAS molecular orientation and mobility at the interface are found to be vastly influenced by the length and architecture of the hydrophobic fluorocarbon tail. A significant ordering of the water dipole moment near the anionic headgroup is apparent at high surface concentration. A direct correlation is established between the PFAS interfacial properties and PFAS-PFAS, PFAS-counterion, and PFAS-water interactions.

Substoichiometric La0.8MnO3-based nanocomposites for PGM-free activation of CH4: Ni or Cu? Surface or bulk?

Methane is a renewable fuel when derived from biogas upgrading or by CO2 capture and utilization, with the possibility of fully replacing natural gas in the already established gas infrastructure and engines. However, being a potent greenhouse gas, its use as fuel demands a sustainable activation procedure, to convert any residual traces of unburned CH4 into CO2, a challenging reaction especially at near-stoichiometric conditions typical of Three-Way Catalytic systems (TWC). To avoid expensive noble metals, we developed cheaper alternative catalysts: A-site deficient LaMnO3-based nanocomposites incorporating Ni and Cu. These elements were introduced either as B-site dopants in the perovskite lattice or deposited via Ammonia-driven Deposition-Precipitation (ADP) on the perovskite surface, in both cases yielding metal nanoparticles (NPs) after a reductive treatment. Characterization encompassed various techniques: XRD, N2 physisorption, SEM-EDX, XPS, H2-TPR, HAADF STEM-EDX. CH4 oxidation to CO2 under stoichiometric O2 served as the probe reaction, as model for TWC conditions in methane-fed engines. The LaMn-perovskite itself displayed a promising activity thanks to favourable morphological and redox features (50 % and 90 % CH4 conversion at 581 °C and 678 °C, respectively); further improvements could be obtained upon Ni and Cu loading. The best performances were achieved by: i) the catalyst prepared by Ni-ADP (50 % and 90 % CH4 conversion at 517 °C and 635 °C), featuring high Ni surface concentration and NPs density and a synergy with the perovskite support, as opposed to the low Ni surface concentration on B-site doped samples; ii) the reduced Cu-doped catalyst (50 % and 90 % CH4 conversion at 508 °C and 645 °C), thanks to the high activity of reduced Cu species, the low NPs size and good metal-support interaction, in contrast to the strong NPs agglomeration of the Cu-ADP catalyst. Among the two most active catalysts, a better long-term stability was retained by the Cu-doped sample. This work laid the foundation for the development of alternative CH4 oxidation catalysts at the stoichiometric air-to-fuel ratio, cheaper than commercial Pd-based ones.

A circular economy approach for utilization of tannery fleshing hydrolysate and kitchen wastes into organic fertilizer through enzymatic decomposition

This study presents a sustainable method for converting tannery fleshing waste (FH) into organic fertilizer using enzymatic decomposition with crude protease. After extracting fat from the enzymatic hydrolysis, the enzyme-rich residue was mixed with dried kitchen waste (KW) and allowed to decompose for 45 days, producing nutrient-rich fertilizer. FT-IR spectroscopy confirmed the presence of important functional groups, including hydroxyl, aliphatic hydrocarbons, esters, and amide-I linkages. The organic fertilizers had higher nutrient content, with nitrogen (1.08-1.67%), phosphorus (0.78–0.98 %), potassium (0.1–0.76 %), and magnesium (239–259.5 ppm) which is higher than commercial fertilizers. FESEM-EDX analysis revealed a dense, porous structure with a high surface concentration of calcium, which enhances nutrient release in the soil. Dissolution tests showed that nutrients from the organic fertilizer were released gradually over 36 hours, whereas commercial NPK fertilizers released nutrients within 150 minutes in simulated soil-water conditions. Field trials with a Randomized Complete Block Design (RCBD) demonstrated improved growth in Malabar spinach, particularly with fertilizer sample S-5, which had an optimal flesh to kitchen waste (FH to KW) ratio of 1:10. Although S-5 had a lower nitrogen content (1.08 %), it contained higher levels of phosphorus (0.98 %), potassium (0.765 %), and magnesium (259.5 ppm), contributing to enhanced plant growth. The organic fertilizer resulted in a shoot length of 38.8 ± 2.0 cm, root length of 16.33 cm, 31 ± 3 leaves, and 95.12 % dry matter of the plant. Heavy metal analysis of the plant confirmed that levels of chromium (Cr), iron (Fe), nickel (Ni), cadmium (Cd), copper (Cu), and lead (Pb) were within WHO safety limits. Phytotoxicity tests of the fertilizer also showed no negative impact on Malabar spinach seed germination.

Creating High Yield Stress Particle-Laden Oil/Water Interfaces Using Charge Bidispersity.

Interfacial engineering has been increasingly used to stabilize Pickering emulsions in commercial products and biomedical applications. Pickering emulsion stabilization is aided by interfacial viscoelasticity; however, typically the primary means of stabilization are steric hindrances between high surface concentration shells of particles around the drops. In this work, the concept of creating large interfacial viscoelastic yield stresses with low particle surface concentrations (<50%) using bidisperse charged particle systems is tested to evaluate their potential efficacy in emulsion stabilization. To explore this hypothesis, interfacial rheology and visualization experiments are conducted at o/w interfaces using positively charged amidine, negatively charged carboxylate, and negatively charged sulfate-coated latex spheres and compared to a model based on interparticle forces. Bidisperse particle systems have been observed to create more networked structures than monodisperse systems. For surface concentrations of <50%, bidisperse interfaces created measurable viscoelastic moduli ∼1 order of magnitude larger than monodisperse interfaces. Furthermore, these interfaces have measurable yield stresses on the order of 10-4 Pa·m when monodisperse systems have none. Bidispersity impacts surface viscoelasticity primarily by increasing the overall magnitude of attraction between particles at the interface and not due to changes in the microstructure. The developed model predicts the relative surface fraction that creates the largest moduli and shows good agreement with the experimental data. The results demonstrate the ability to create large viscoelastic moduli for small surface fractions of particles, which may enable stabilization using fewer particles in future applications.

Fabrication of Nanobioengineered Interfaces Utilizing Quaternary Nanocomposite for Highly Efficient and Selective Electrochemical Biosensing of Urea.

Nanobioengineered interfaces have gained attention owing to their small size and high surface area-to-volume ratio for utilization as a platform for highly selective and sensitive biosensing applications owing to the integration of biological molecules with engineered nanomaterials/nanocomposites. In this work, a novel Ag-complex, [(PPh3)2Ag(SCOf)]-based quaternary Ag-S-Zn-O nanocomposites (NCs), was synthesized through an environmentally-friendly process. The results revealed the formation of the NCs with an average crystallite size and particle size of 36.08 and 40.22 nm, respectively. In addition, this is the first study to utilize such NCs synthesized via a single-source precursor method, offering enhanced sensor performance due to their unique structural properties. Further, these NCs were used to fabricate a urease (Ur)/Ag-S-Zn-O NCs/ITO nanobioengineered electrode for precise and sensitive electrochemical biosensing of urea. The interfacial kinetic studies revealed quasi-reversible processes with high electron transfer rates and linear current responses, indicating efficient reaction dynamics. A high diffusion coefficient and low surface concentration suggested a fast diffusion-controlled process, affirming the electrode's potential for rapid and sensitive urea detection. The biosensor demonstrated notable sensing properties such as high sensitivity (12.56 μA mM-1 cm-2) and a low detection limit (0.54 mM). The fabricated bioelectrode was highly selective and reproducible and demonstrated stability for up to 60 days. These results validate the potential of this nanobioengineered interface for next-generation biosensing applications, paving the way for advanced point-of-care diagnostics and real-time health monitoring.

Random close packing of semi-flexible polymers in two dimensions: Emergence of local and global order.

Through extensive Monte Carlo simulations, we systematically study the effect of chain stiffness on the packing ability of linear polymers composed of hard spheres in extremely confined monolayers, corresponding effectively to 2D films. First, we explore the limit of random close packing as a function of the equilibrium bending angle and then quantify the local and global order by the degree of crystallinity and the nematic or tetratic orientational order parameter, respectively. A multi-scale wealth of structural behavior is observed, which is inherently absent in the case of athermal individual monomers and is surprisingly richer than its 3D counterpart under bulk conditions. As a general trend, an isotropic to nematic transition is observed at sufficiently high surface coverages, which is followed by the establishment of the tetratic state, which in turn marks the onset of the random close packing. For chains with right-angle bonds, the incompatibility of the imposed bending angle with the neighbor geometry of the triangular crystal leads to a singular intra- and inter-polymer tiling pattern made of squares and triangles with optimal local filling at high surface concentrations. The present study could serve as a first step toward the design of hard colloidal polymers with a tunable structural behavior for 2D applications.

Synthesis of Gold Nanoparticles over CoAl Mixed Oxide for Ethanol Oxidation Reaction.

Catalytic total oxidation is an effective technique for the treatment of industrial VOCs principally resulting from industrial processes using solvents and usually containing mono-aromatics (BTEX) and oxygenated compounds (acetone, ethanol, butanone). The aim of this work is to deposit gold nanoparticles on CoAl mixed oxide issued from layered double hydroxide (LDH) precursor by using the deposition precipitation (DP) method, which is applied with two modifications, labeled method (A) and method (B), in order to enhance the interaction of the HAuCl4 precursor with the support. Method (A) involves the hydrolysis of the HAuCl4 precursor after addition of the support, while in method (B), the gold precursor is hydrolyzed before adding the support. The two methods were applied using as support the CoAl mixed oxide and the LDH precursor. Samples were characterized by several physical chemical techniques and evaluated for ethanol total oxidation. Method (B) allowed the ethanol oxidation activity to be enhanced for the resulting Au/CoAlOx catalysts thanks to the high surface concentration of Co2+ and improved reducibility at low temperature. The presence of gold permits to minimize the formation of by-products, notably, methanol, allowed for a total oxidation of ethanol at lower temperature than the corresponding support.

Highly Efficient Iridium-Iron-Molybdenum Catalysts Condensed on Boron Nitride for Biomass-Derived Diols' Hydrogenolysis to Secondary Monoalcohols.

A trade-off of activity-selectivity exists in primary C-O hydrogenolysis of biomass-derived diols to secondary alcohols over bimetallic catalysts, especially the combination of noble metal and early transition metal in the metallic state and metal oxide state, respectively. Herein, the combination of high surface concentration of boron nitride (BN)-supported metals and the addition of Mo as third metal broke the trade-off. High yields (>50%) of secondary alcohols were obtained with robust productivity up to 25-fold based on Ir over Ir-Fe0.13-Mo0.08/BN (Ir = 20 wt %, Fe/Ir = 0.13, Mo/Ir = 0.08) than previously reported Ir-Fe catalysts. In contrast, simply increasing the loading amount of Ir-Fe catalysts or the addition of Mo species only enhanced the productivity by <2-4-fold. Various characterizations showed that large Ir loading enables the formation of condensed nanostructures (∼2 nm) on the BN support, which further alloy with Mo and Fe to form an face centred cubic (fcc)-type trimetallic alloy with surface enrichment of Fe. On the other hand, in Ir-Fe0.25-Mo0.08/BN with lower Ir (5 wt %) and lower Ir-based activity, the Mo species were rather bound on the support surface possibly as the MoBx state. These structures were formed by simple impregnation and reduction with H2 at the reaction temperature (453 K). The high activity of Ir-Fe0.13-Mo0.08/BN (20 wt % Ir) is derived from two aspects: (1) the formation of condensed nanostructures (∼2 nm) exposing more active sites and (2) alloying with Mo to modify the electronic state of Ir to enhance the H2 activation ability, as shown by the decreased Ea (82-84 → 67 kJ mol-1).

Phosphorus emitter profile control for silicon solar cell using the doss diffusion technique

The Doped Oxide Solid Source (DOSS) diffusion technique is well suited for fine-tuning of the surface concentration. The dopant surface concentration is important during phosphorus emitter diffusion due to the opposite requirements of a lowly doped emitter for good blue response and a sufficiently high surface concentration for a good ohmic contact. The sources are made in the laboratory using the standard POCl3 diffusion technique. DOSS Diffusions were carried out in the temperature range 850-1050°C using sources with different doping levels obtained by varying the POCl3 partial pressure from 0.004 % to 4.28 %. The electrical profiles were measured using the Stripping Hall profiling technique. Phosphorus diffusion profiles with the complete elimination of the dead layer have been obtained over a large range of source concentrations for all investigated diffusion temperatures. The residual diffusion oxide thickness increased with both temperature and source doping level within the range 7.5-30 nm. XPS profiling indicated that the composition of the residual glass was a mixture of P2O5 and SiO2.

Operando insights into correlating CO coverage and Cu-Au alloying with the selectivity of Au NP-decorated Cu2O nanocubes during the electrocatalytic CO2 reduction.

Electrochemical reduction of CO2 (CO2RR) is an attractive technology to reintegrate the anthropogenic CO2 back into the carbon cycle driven by a suitable catalyst. This study employs highly efficient multi-carbon (C2+) producing Cu2O nanocubes (NCs) decorated with CO-selective Au nanoparticles (NPs) to investigate the correlation between a high CO surface concentration microenvironment and the catalytic performance. Structure, morphology and near-surface composition are studied via operando X-ray absorption spectroscopy and surface-enhanced Raman spectroscopy, operando high-energy X-ray diffraction as well as quasi in situ X-ray photoelectron spectroscopy. These operando studies show the continuous evolution of the local structure and chemical environment of our catalysts during reaction conditions. Along with its alloy formation, a CO-rich microenvironment as well as weakened average CO binding on the catalyst surface during CO2RR is detected. Linking these findings to the catalytic function, a complex compositional interplay between Au and Cu is revealed in which higher Au loadings primarily facilitate CO formation. Nonetheless, the strongest improvement in C2+ formation appears for the lowest Au loadings, suggesting a beneficial role of the Au-Cu atomic interaction for the catalytic function in CO2RR. This study highlights the importance of site engineering and operando investigations to unveil the electrocatalyst's adaptations to the reaction conditions, which is a prerequisite to understand its catalytic behavior.

Study on selective emitter fabrication through an innovative pre‐diffusion process for enhanced efficiency in TOPCon solar cells

AbstractTOPCon (tunnel oxide passivated contact) solar cell is the mainstream high‐efficiency crystalline silicon solar cell structure. However, the lack of efficient passivation contact mechanisms on the front surface restricts the electrical performance ability to improve further. Selective emitter (SE) technology, considered a potential solution, needs to be more mature. This work provides a unique thermal pre‐diffusion approach combined with laser treatment and post‐oxidation annealing to create SE structures in TOPCon solar cells. Times for the high‐temperature process are equivalent to those for a traditional homogenous emitter. The innovative thermal pre‐diffusion process created a unique boron doping profile, achieving a high surface concentration of nearly 1 × 1020 cm−3 with a shallow junction depth of approximately 0.25 μm. Laser treatment further activated boron and facilitated its diffusion, influenced by the boron silicate glass layer and surface boron atoms. Adjustments were made to improve the pre‐diffusion recipe, including an additional boron deposition step, increasing non‐activated boron atoms. Introducing larger pyramidal microstructures also improved the junction depth and surface concentration in the heavily doped region. Compared to homogeneous emitters, the SE structures exhibited lower surface concentration in the lightly doped region, reducing the recombination current density in the passivation region J0,pass values. The SE structures achieved higher junction depths, limiting metal atom diffusion and reducing the current recombination density in the metal contact region J0,metal values. The contact resistivity between metal and silicon was also decreased. Overall, introducing SE structures resulted in a batch‐average efficiency improvement of 0.26%, reaching an average efficiency of 25.22% for TOPCon solar cells, and has industrial mass‐producible.

Push-pull mechanics of E-cadherin ectodomains in biomimetic adhesions

E-cadherin plays a central role in cell-cell adhesion. The ectodomains of wild-type cadherins form a crystalline-like two-dimensional lattice in cell-cell interfaces mediated by both trans (apposed cell) and cis (same cell) interactions. In addition to these extracellular forces, adhesive strength is further regulated by cytosolic phenomena involving α and β catenin-mediated interactions between cadherin and the actin cytoskeleton. Cell-cell adhesion can be further strengthened under tension through mechanisms that have not been definitively characterized in molecular detail. Here we quantitatively determine the role of the cadherin ectodomain in mechanosensing. To this end, we devise an E-cadherin-coated emulsion system, in which droplet surface tension is balanced by protein binding strength to give rise to stable areas of adhesion. To reach the honeycomb/cohesive limit, an initial emulsion compression by centrifugation facilitates E-cadherin trans binding, whereas a high protein surface concentration enables the cis-enhanced stabilization of the interface. We observe an abrupt concentration dependence on recruitment into adhesions of constant crystalline density, reminiscent of a first-order phase transition. Removing the lateral cis interaction with a “cis mutant” shifts this transition to higher surface densities leading to denser, yet weaker adhesions. In both proteins, the stabilization of progressively larger areas of deformation is consistent with single-molecule experiments that show a force-dependent lifetime enhancement in the cadherin ectodomain, which may be attributed to the “X-dimer” bond.

Estimating Surface Concentrations of Calanus finmarchicus Using Standardised Satellite-Derived Enhanced RGB Imagery

Calanus finmarchicus is a keystone zooplankton species that is commercially harvested and is critical in sustaining many important fisheries in the North Atlantic. However, due to their patchy population distributions, they are notoriously difficult to map using traditional ship-based techniques. This study involves the use of a combined approach of standardized ocean colour imagery and radiative transfer modelling to identify reflectance anomalies potentially caused by surface swarms of C. finmarchicus in the northern Norwegian Sea. Here, we have standardized satellite eRGB imagery that depicts a distinct ‘red’ patch, which coincides with in situ measurements of high surface concentrations of C. finmarchicus. Anomaly mapping using a novel colour matching technique shows a high degree of anomaly within this patch compared to the surrounding waters, indicating the presence of something other than the standard bio-optical model constituents influencing the optics of the water column. Optical closure between modelled and satellite-derived reflectance signals is achieved (and the anomaly is significantly reduced) through the addition of C. finmarchicus absorption into the model. Estimations of the surface concentrations of C. finmarchicus suggest between 80,000 and 150,000 individuals m−3 within the extent of the identified red patch. Furthermore, analysis of the impact of C. finmarchicus absorption on the OC3M algorithm performance points to the potential for the algorithm to over-estimate chlorophyll concentrations if C. finmarchicus populations are present in the surface waters.

Retrieval analysis of the Essure® micro insert female sterilization implant: Methods for metal ion and microscopic analysis.

The Essure® Device is a female sterilization implant comprised of four alloys (Ni-Ti, 316L SS, Pt-Ir and Sn-Ag) and Dacron fibers. As part of the mandated 522 post-market surveillance study, implant retrieval and metal-ion analysis methods were developed separate from patient clinical data, to quantify trace metal ions found in tissue and to assess implant degradation present. Three segments of tissue (proximal implant, distal implant, and tissue distal from the implant) stored in neutral buffered formalin, were retrieved. Tissue was prepared for metal ion analysis using inductively coupled mass spectrometry (ICP-MS). Implant sections from four patients, were analyzed using digital optical microscopy (DOM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Image analysis showed Sn-Ag solder corroded and elevated Sn ion levels in tissue proximal to the solder compared to tissues more remote in all cases observed. The 316L SS exhibited signs of degradation with high surface concentrations of molybdenum and chromium and low iron compared to the parent alloy. Evidence of elevated iron, chromium and nickel within the tissues and storage solutions combined with precipitation of an iron-calcium-phosphorous material on some implants indicate evidence of SS corrosion. Ni-Ti, Pt-Ir and Dacron appear to have no major damage. This study includes preliminary results as part of the ongoing 522 study and therefore no final conclusions regarding the device or patient data can be drawn from this present study until the entire 522 study is complete. STATEMENT OF SIGNIFICANCE: The Essure Device is a female sterilization implant that was implanted into approximately 750,000 women. The device is composed of polyethylene terephthalate fibers and 4 metal alloys, 316L stainless steel, Nickel-Titanium, Tin-Silver and Platinum-Iridium. Following an increase in patient reported adverse events, the FDA required a 522-post market surveillance study. As part of this study, implants are retrieved from patients via salpingectomy or hysterectomy. This study focuses on the development of the implant retrieval methods following surgery, with focus on measuring local tissue metal ions, their distribution and assessing the degradation of the implant without correlation to patient clinical condition.

Effect of CeO2 redox properties on the catalytic activity of Pt-CeOx over irreducible SiO2 support for methylcyclohexane (MCH) dehydrogenation

A highly reducible CeO2 surface was prepared on a SiO2 support to investigate the effect of redox properties of CeO2 on the catalytic activity of Pt/CeO2-SiO2 for MCH dehydrogenation. Characterization of the Pt/CeO2-SiO2 catalyst revealed a significantly higher Pt dispersion than Pt/micro-sized CeO2 and Pt/SiO2. The well-dispersed Pt particles averaging 1.1 nm in size (Pt/CeO2-SiO2) were primarily attributed to the high surface concentration of oxygen vacancies, which provided abundant defect sites that stabilized the Pt particles from sintering. Hydrogen released from MCH dehydrogenation was approximately 5–6 times greater with high selectivity towards toluene products for Pt/CeO2-SiO2 compared to its counterparts. The excellent catalytic activity of Pt/CeO2-SiO2 was attributed to the presence of rich oxygen vacancies on the CeO2 surface, which was significantly reduced under MCH dehydrogenation conditions, resulting in faster toluene desorption.

Distribution and physical–biological controls of dimethylsulfide in the western tropical Indian Ocean during winter monsoon

New field observation on distribution, turnover, and sea–air flux of three dimethylated sulfur compounds (dimethylsulfide (DMS), dimethylsulfoniopropionate, and dimethylsulfoxide) in the western tropical Indian Ocean (WTIO; 4°N–10°S, 61°–65°E) were conducted under the major Global Change and Air–Sea Interaction Program during the 2021/2022 Northeast Monsoon (December 21, 2021 to January 11, 2022). Significantly high surface concentrations of DMS were identified in the region of the Seychelles–Chagos Thermocline Ridge (SCTR; 5°–10°S). This occurred because the shallow thermocline/nitracline and associated upwelling fueled biological production of DMS in the subsurface, which was brought to the surface through vertical mixing. The calculated sea–air DMS flux was also significantly strong in the SCTR region during the Northeast Monsoon owing to combination of high wind speed and high surface concentration of DMS. This finding is similar to results obtained previously during the Southwest Monsoon, suggesting that the SCTR region is an area of active DMS emission during both the Northeast Monsoon and the Southwest Monsoon. Microbial consumption was the dominant pathway of DMS removal, accounting for 74.4% of the total, whereas the processes of photolysis (17.7%) and ventilation (7.9%) were less important. Future work should be undertaken in the WTIO to establish how DMS emission is linked to aerosol properties and climate change.

Sources of air pollution-related health impacts and benefits of radially applied transportation policies in 14 US cities

As the world becomes increasingly urbanized, growing populations are exposed to poor ambient air quality and at risk of the associated health outcomes. Urban air quality is affected both by local sources of air pollution and sources outside city borders. Policy-makers who develop air quality policies need to know whether it is most effective to focus on local policies or to spend resources fostering larger regional air quality management cooperation. Identifying the fraction of air pollution exposure from emissions as a function of distance from the city is a critical element of air quality management design. We estimate the health burden associated with exposure to fine particulate matter (PM2.5), ozone (O3), and nitrogen dioxide (NO2) from county-level anthropogenic sources in and around 14 US cities; this analysis is a test-bed to conduct future global analyses. We use adjoint sensitivities calculated from the chemical transport model GEOS-Chem, high resolution satellite-derived surface concentrations of PM2.5 and NO2, and health impact assessment methods. For the 70.2 million people living in these cities, we estimate that 27,740 PM2.5- and O3-related premature deaths and 126,600 NO2-related new asthma cases were attributable to air pollution exposure in 2011. Development within the GEOS-Chem adjoint framework enables sectoral attribution and policy analysis in addition to the rote assessment of impact. We find that 70% of deaths and nearly 100% of these asthma cases were attributable to anthropogenic emissions. There is great variability in the sources of the anthropogenically-related health impacts; within-urban emissions make up 5% in Austin to 56% in Los Angeles and Phoenix (median: 31%) of urban premature deaths and 18% in Austin to 82% in Los Angeles (median: 59.5%) of new asthma cases, with the remaining portions attributable to emissions from outside the urban area. For each city, we estimate the air quality related health benefits associated with the adoption of a vehicle-miles-traveled fee in that city and in multiple spatial regions surrounding the city. The findings suggest that the proportion of urban air pollution that is regional is greater for premature deaths than new asthma cases and for the eastern US than the western US.

Silica modulated palladium catalyst with superior activity for the selective catalytic reduction of nitrogen oxides with hydrogen

A significant promotion effect of colloidal SiO2 on Pd/TiO2 catalyst for improving the activity and N2 selectivity in the selective catalytic reduction of NO with H2 (H2-SCR) was reported, both before and after hydrothermal aging. The SiO2 addition not only benefited the formation of more oxygen vacancies but also increased Pd dispersion and created rich Pd-SiO2 interfaces on Pd-SiO2/TiO2 catalyst. The H2-SCR of NO on both Pd/TiO2 and Pd-SiO2/TiO2 followed a Langmuir-Hinshelwood mechanism, in which the adsorbed bridging bidentate nitrates on TiO2 could react with dissociated H2 species on Pd sites at Pd-TiO2 interface. Particularly, on the promoted Pd-SiO2/TiO2, the Pd-TiO2 interface could facilitate NO adsorption and activation, and the created Pd-SiO2 interface could benefit H2 adsorption and dissociation, thus contributing to its significantly improved H2-SCR activity. Furthermore, the active Pd species (which should be Pd0 under reaction condition with higher surface concentration) within Pd-SiO2/TiO2 could be well stabilized during long-term hydrothermal aging process through the formation of rich Pd-SiO2 interfaces.