Environment-related Applications Research Articles

A Decade of Electrocatalysis with Metal Aerogels: A Perspective

Nowadays, great efforts have been spent on addressing concerns over energy and environmental crises. Among these efforts, electrocatalysis is widely recognized and studied for its high efficiency and easy processability. As a class of emerging electrocatalysts, metal aerogels (MAs) stand out in the last decade. In virtue of their three-dimensional conductive pathways, their library of catalytically/optically active sites, and their robust network structures, MAs have unique advantages in electrocatalysis. However, due to the short history of MAs, there is insufficient research on them, leaving significant room for material design and performance optimization. This perspective will mainly focus on electrocatalysis with MAs, aiming to summarize the state-of-the-art progress and to guide the on-target design of efficient MAs-based electrocatalysts towards energy- and environment-related applications.

Silicotungstic acid as electron transfer mediator in Z-scheme g-C3N4/H4SiW12O40/Ag3PO4: Accelerated charge interface transportation for high-efficient photocatalysis

Photocatalytic degradation of organic pollutants has shown its promise in wastewater purification, however the photocatalytic activity on most catalysts are still unsatisfactory due to the poor reactive oxygen species production as a result of sluggish charge separation. Here, an innovative silicotungstic acid mediated charge transfer system over the Z-scheme g-C3N4/H4SiW12O40/Ag3PO4 photocatalyst is proposed, exhibiting remarkable photocatalytic activity toward oxygen activation for reactive oxygen species generation. We verify that the H4SiW12O40 with the unique Keggin units could serve as charge transfer mediator to speed up charge transportation between g-C3N4 and Ag3PO4, as a result showing dramatically enhanced charge separation efficiency. By virtue of the aforementioned advantages, the as-prepared Z-scheme photocatalyst of g-C3N4/H4SiW12O40/Ag3PO4 shows excellent photocatalytic performance toward carbamazepine degradation, where the pseudo-first-order rate constant is estimated to be 78, 18, and 9 times higher than that of g-C3N4, Ag3PO4, and g-C3N4/Ag3PO4. The innovative design of using H4SiW12O40 as solid charge transfer mediator offers new viewpoints in designing high-efficient photoctalysts for environmental related applications.

High reusability of green-synthesized Fe3O4/TiO2 photocatalyst nanoparticles for efficient degradation of methylene blue dye

This study investigates photocatalytic degradation performance of Fe 3 O 4 /TiO 2 nanoparticles (NPs) green-synthesized using Moringa oleifera leaf extract. A coprecipitation synthesis method was successfully used to synthesize NPs of various concentrations and the magnetic properties of the photocatalyst was further explored so that it could be reused. X-ray diffraction and selected area electron diffraction showed that TiO 2 has a tetragonal structure and Fe 3 O 4 has an inverse spinel cubic structure. The prepared transmission electron microscopy image of Fe 3 O 4 /TiO 2 showed that it was almost spherical, not uniform, and slightly dispersed under agglomerated conditions due to the presence of a TiO 2 boundary. Besides, the chemical elements are confirmed by energy-dispersive X-ray spectroscopy . Fourier-transform infrared spectra showed functional groups namely C–H, C=O, C=C, and C–N which indicating successful green synthesis. In addition, the presence of Fe–O functional groups at 551.8–620.3 cm −1 and Ti-O at 400–600 cm −1 also suggests the formation of NPs. A vibrating sample magnetometer showed that the Fe 3 O 4 /TiO 2 NPs exhibited saturation magnetization in the range of 11.15–30.38 emu/g, with a coercivity value of approximately 55 Oe. The degradation efficiency of methylene blue (MB) was optimal for Fe 3 O 4 :TiO 2 at a concentration of 1:7 which reached 99.9% degradation for two hours for uptake every 20 minutes. Owing to the magnetic potential of the synthesized NPs, they could be recycled up to four times without significant loss of activity. Therefore, green synthesis of Fe 3 O 4 /TiO 2 NPs is promising for effective and efficient removal of organic pollutants in various environment-related applications. • Fe3O4/TiO2 NPs were synthesized using coprecipitation method with MO extract • Green-synthesized Fe3O4/TiO2 NPs have superior photocatalytic activity up to 99.9% • kapp value between the theoretical model and the experimental data has a good match • After 4 repetitions, the photocatalyst showed excellent stability and reusability • A conceivable photocatalytic mechanism has been proposed

Novel Ag-bridged dual Z-scheme g-C3N4/BiOI/AgI plasmonic heterojunction: Exceptional photocatalytic activity towards tetracycline and the mechanism insight

Rational design and synthesis of highly efficient and robust photocatalysts with positive exciton splitting and interfacial charge transfer for environmental applications is critical. Herein, aiming at overcoming the common shortcomings of traditional photocatalysts such as weak photoresponsivity, rapid combination of photo-generated carriers and unstable structure, a novel Ag-bridged dual Z-scheme g-C3N4/BiOI/AgI plasmonic heterojunction was successfully synthesized using a facile method. Results showed that Ag-AgI nanoparticles and three-dimensional (3D) BiOI microspheres were decorated highly uniformly on the 3D porous g-C3N4 nanosheet, resulting in a higher specific surface area and abundant active sites. The optimized 3D porous dual Z-scheme g-C3N4/BiOI/Ag-AgI manifested exceptional photocatalytic degradation efficiency of tetracycline (TC) in water with approximately 91.8% degradation efficiency within 165 min, outperforming majority of the reported g-C3N4-based photocatalysts. Moreover, g-C3N4/BiOI/Ag-AgI exhibited good stability in terms of activity and structure. In-depth radical scavenging and electron paramagnetic resonance (EPR) analyses confirmed the relative contributions of various scavengers. Mechanism analysis indicated that the improved photocatalytic performance and stability were ascribed to the highly ordered 3D porous framework, fast electron transfer of dual Z-scheme heterojunction, desirable photocatalytic performance of BiOI/AgI and synergistic effect of Ag plasmas. Therefore, the 3D porous Z-scheme g-C3N4/BiOI/Ag-AgI heterojunction had a good prospect for applications in water remediation. The current work provides new insight and useful guidance for designing novel structural photocatalysts for environment-related applications.

Current Scenario of MXene-Based Nanomaterials for Wastewater Remediation: A Review

Rapid urban and industrial sectors generate massive amounts of wastewater, creating severe ecological disruption and harming living organisms. The number of harmful pollutants such as dyes, heavy metals, antibiotics, phenolic compounds, and volatile and several organic chemicals discharged into aquatic systems varies depending on the effluent composition of various sectors. MXene-based composites with unique characteristics were spotlighted as newly developed nanomaterials specifically for environmental-related applications. Therefore, this review broadly discusses the properties, basic principles of MXene, and synthesis routes for developing different MXene-based nanomaterials. The most current strategies on the energy and environmental applications of MXene-based nanomaterials, particularly in photocatalysis, adsorption, and water splitting, were deeply explored for the remediation of different pollutants and hydrogen (H2) evolution from wastewater. The detailed mechanism for H2 evolution and the remediation of industrial pollutants via photocatalysis and adsorption processes was elaborated. The multi-roles of MXene-based nanomaterials with their regeneration possibilities were emphasized. Several essential aspects, including the economic, toxicity and ecological power of MXene-based nanomaterials, were also discussed regarding their opportunity for industrialization. Finally, the perspectives and challenges behind newly developed MXene and MXene-based nanomaterials for environmental pollution were reviewed.

Industry-compatible covalent organic frameworks for green chemical engineering

In order to move towards sustainable development, the discovery of energy-efficient and environmentally friendly materials has become increasingly imperative. Covalent organic frameworks (COFs) as emerging designable crystalline porous materials have captured increasing attention for a wide array of clean-energy and environmental applications, attributed to their attractive advantages of low density, high surface area, adjustable and periodic pores, and functional skeletons. This review attempts to highlight the key advancements made in the green synthesis of COFs, processing of COFs, energy and environment-related applications, including gas storage, water treatment, the separation of gas mixture and organic molecules, catalysis, supercapacitors, fuel cell, and rechargeable batteries. Finally, a perspective regarding the remaining challenges and future directions on the synthesis and promising application for green chemical engineering of COFs has also been presented based on current achievements.

Dual-Purpose Sensing Nanoprobe Based on Carbon Dots from o-Phenylenediamine: pH and Solvent Polarity Measurement.

Today, the development of nanomaterials with sensing properties attracts much scientific interest because of the demand for low-cost nontoxic colloidal nanoprobes with high sensitivity and selectivity for various biomedical and environment-related applications. Carbon dots (CDs) are promising candidates for these applications as they demonstrate unique optical properties with intense emissions, biocompatibility, and ease of fabrication. Herein, we developed synthesis protocols to obtain CDs based on o-phenylenediamine with a variety of optical responses depending on additional precursors and changes in the reaction media. The obtained CDs are N-doped (N,S-doped in case of thiourea addition) less than 10 nm spherical particles with emissions observed in the 300–600 nm spectral region depending on their chemical composition. These CDs may act simultaneously as absorptive/fluorescent sensing probes for solvent polarity with up to 85, for from 0.099 to 1.0 and for pH values in the range of 3.0–8.0, thus opening an opportunity to check the pH in non-pure water or a mixture of solvents. Moreover, CDs preserve their optical properties when embedded in cellulose strips that can be used as sensing probes for fast and easy pH checks. We believe that the resulting dual-purpose sensing nano probes based on CDs will have high demand in various sensing applications.

Smoke detection in video using convolutional neural networks and efficient spatio-temporal features

Fire detection in its early stages is of a great importance in different environmental related applications. Among the visual signs of fire, smoke appears earlier than the flames in many cases, and quickly reaches the environment. Thus, it can be used for early detection of fire using machine vision techniques. Existing approaches have tried to do it either by traditional machine learning methods applying various combinations of color, texture, and motion features, or by deep learning-based methods that can automatically capture the smoke features from images. However, the former approaches face number of challenges due to the transparent nature of smoke and its variant visual appearance in different environments, and the later ones are not able to capture motion characteristics of smoke, so, their efficiency in various environmental conditions is still problematic and often cause false alarms. In this study, we aim to introduce a hybrid approach that is based on deep learning, spatio, and spatio-temporal characteristics of the smoke. Doing so, we use all the strengths of these techniques to detect the smoke as accurately as possible. The proposed method consists of four stages: 1) moving pixels are extracted from input images by an efficient motion detection scheme; 2) the extracted moving areas are given individually to a tailored convolutional neural network to identify candidate smoke regions; 3) an efficient combination of spatial and spatio-temporal features is extracted from each candidate region based on the distinct characteristics of smoke; 4) a support vector machine classifier is used to further classify real smoke from non-smoke regions using the extracted features. The proposed method is implemented using Python programming language, and extensive experiments conducted on “Visor”, “Bilkent”, and “Yuan” benchmark datasets which show it has high performance and accuracy. The results also indicate that its reliability is far better than the competitors in terms of false alarm rate. The average accuracy and false positive rates obtained on 10 testing videos are 97.63% and 3.8%, respectively. Also, the proposed method is able to detect both white and black smokes which, to our best knowledge, has not been addressed in any of the related researches.

Efficient solar-driven interfacial water evaporation enabled wastewater remediation by carbonized sugarcane

Solar-driven interfacial water evaporation has great potential in wastewater remediation. Carbonized biomass materials emerged as attractive solar evaporators due to their excellent solar harvesting, solar-thermal converting, and water delivering capabilities. In this study, antimony doped tin oxide (ATO) was loaded to sugarcane that was then carbonized to obtain composite solar evaporator CS@ATO which delivered a solar absorption of 99 %, a solar evaporation rate of 1.43 kg m−2 h−1 and an efficiency of 95.3 %. Treated with CS@ATO, the concentrations of heavy metal ions in wastewater were reduced by 3–4 orders, and dyes in wastewater were removed almost completely. For seawater desalination with CS@ATO, the contents of the main cations in the collected fresh water were lower than the levels in drinking water defined by WHO. CS@ATO also exhibited long-term service capability in both wastewater remediation and seawater desalination. These results suggested great potential of CS@ATO in the aforementioned environment related applications.

Advances in facet-dependent photocatalytic properties of BiOCl catalyst for environmental remediation

Abstract Bismuth chloride oxide (BiOCl) is a typical V-VI-VII ternary oxide material, which is one of the widely studied metal oxides due to its unique surface, electronic and photocatalytic properties. However, the broad bandgap and the large number of photogenerated electron-hole pair complexes of BiOCl limit its photocatalytic efficiency. Since the photocatalytic performance of BiOCl is highly dependent on its exposed crystallographic facets, research attention has increasingly focused on the different structures and properties possessed by different crystallographic facets of BiOCl. This article reviews the basic principles of using different crystalline surfaces of BiOCl materials to enhance photocatalytic activity, summarizes the applications of BiOCl single-crystal catalysts and composite catalysts in the environmental field, and provides an outlook on the challenges and new research directions for future development in this emerging frontier area. It is hoped that the crystalline surface-related photocatalysis of BiOCl can be used to provide new guidance for the rational design of novel catalysts for various energy and environment-related applications.

Accelerated organic pollutants mineralization in interlayer confined single Pt atom photocatalyst for hydrogen recovery

Photocatalytic H2 recovery from organic wastewater degradation has been considered as a promising way to alleviate the energy shortage and to deal with environmental pollution. However, the achievement of H2 production from organic pollutants mineralization still remains a huge challenge. Herein, a novel solar energy trigged water-energy-system over Pt single atom catalyst (confined by the interlayer subnanospace of carbon nitride, PtSA/g-C3N4) is proposed, exhibiting remarkable photocatalytic performance toward organic pollutants degradation coupled with hydrogen generation. We found that the well confined interlayer environment not only reduces the H2 evolution energy barrier to accelerate H2 evolution, but also blocks the introduced O2 accessing the interlayer confined Pt atoms. Furthermore, the introduced O2 could be activated by the surface layers of carbon nitride, which accelerates the mineralization of hole-oxidized pollutants into H2O and CO2. As a result, PtSA/g-C3N4 exhibits excellent photocatalytic activity toward H2 production coupled with p-chlorophenol mineralization, where more than 9 μmol of H2 is generated with the total organic carbon removal reaches 70% within 4 h photocatalysis. The conceptual study shown here may offer new viewpoints in designing high-efficient photocatalyst for environmental related applications.

Biobased hierarchically porous carbon featuring micron-sized honeycomb architecture for CO2 capture and water remediation

Hierarchically porous carbon (HPC) has exhibited exceptional performance in environmental-related applications; however, the synthesis of high-efficient biobased HPCs remains a challenge because of the inherent structure and chemical composition complexities of biomass. Here, we prepare high-efficient biobased HPC sorbents featuring uniform micron-sized (~20 µm) honeycomb cells and abundant meso- and micropores through combining the selection of biomass precursors and the corresponding synthetic strategies. Cork is selected as the precursor because of its distinctive hollow polyhedral cellular structure and unique chemical composition composed of suberin. ZnCl2 is selected as the activation reagent due to its mild activation effect with less carbon etching and recyclability. The sequential low-temperature pretreatment and ZnCl2 activation processes produce high-efficient HPC sorbent for CO2 capture and water decontamination. Results show that cork-based HPC poses high carbon yield (> 80 wt%), large specific surface area (up to 1853 m2/g), and high pore volume (up to 0.839 cm3/g). Accordingly, cork-based HPC exhibit high CO2 capture performance (e.g., 4.64 mmol/g at 0 °C), superior adsorption capacity for methylene blue (887.7 mg/g) and lead ion (Pb2+, 74.3 mg/g), and fast uptake speed for contaminants (i.e., < 5 min). Moreover, approximately 80% of ZnCl2 can be recycled and reused. This study demonstrates a sustainable and cost-effective process for producing high-efficient HPCs from cork for environmental applications.

Reticular Chemistry for Highly Porous Metal-Organic Frameworks: The Chemistry and Applications.

Current global crises related to clean energy and the environment entail the development of materials that are capable of addressing these challenges. Metal-organic frameworks (MOFs), a class of functional materials assembled from metal-containing nodes and organic ligands via coordination bonds, have been successfully developed for various applications, including catalysis, toxic chemical removal, and gas storage and separation, as a result of their highly tailorable nature and precisely engineered pore structures. In particular, the exceptionally high surface areas and porosities of MOFs are two of their most attractive characteristics and place them among the best porous materials for the storage of clean energy gases, such as hydrogen and methane. Reticular chemistry stands out as a prominent approach to the design of MOFs as this strategy allows for the rational top-down design of frameworks guided by topological nets to afford extended framework structures with precise architectural arrangements at the molecular level. Bridging the gap between reticular chemistry design strategies and highly porous MOFs can facilitate the development of next-generation high-performance materials through state-of-the-art chemical design.In this Account, we summarize our group's efforts over the past few years toward the synthesis and applications of highly porous MOFs inspired by reticular chemistry. First, we describe how we leveraged reticular chemistry to synthesize NU-1500, which is based on the 6-connected edge-transitive acs net, from the assembly of triptycene-based ligands and high-valent metal trimers. This delicate design is amenable to isoreticular expansion, and including an additional phenyl group in the rigid triptycene-based ligand of NU-1500 yields NU-1501. Importantly, NU-1501-Al exhibits both a high gravimetric Brunauer-Emmett-Teller (BET) area of 7310 m2 g-1, which is the current record after satisfying the four BET consistency criteria, and a volumetric BET area of 2060 m2 cm-3. The high porosity and surface area place NU-1501 among the most promising adsorbents for the storage of methane and hydrogen. Second, we illustrate the rational synthesis of highly porous and stable Zr-MOFs based on edge-transitive nets: (1) the successful isoreticular expansions of NU-1000 (a 4,8-connected csq net) form hierarchical mesoporous MOFs with pore sizes of up to 6.7 nm; (2) the assembly of Zr6 clusters and tetracarboxylates yields the NU-1100 series (4,12-connected ftw net) with BET areas of 4300-6500 m2 g-1; and (3) the use of hexacarboxylates in combination with Zr6 clusters results in the formation of the NU-1600 series (a 6,12-connected alb net) with BET areas of 2000-4500 m2 g-1. Third, we leveraged a reticular exploration strategy to access mesoporous uranium-based MOFs, NU-1300 (a 3,4-connected tbo net, 2100 m2 g-1) and NU-1301 (a 3-connected nun net, 4750 m2 g-1). In particular, we investigated the structurally complex NU-1301, which formed serendipitously from the combination of uranyl clusters and triangular carboxylates to afford a structure with the largest unit cell among all reported MOFs.Finally, we provide an overview of potential applications of these highly porous MOFs, including water capture, catalysis, methane storage, hydrogen storage, and the separation of organic dyes and biological macromolecules. We hope that this Account may serve as a blueprint and stimulate researchers to develop the next generation of highly porous materials for energy- and environment-related applications and beyond.

Upcycling the barbeque grease into carbon nanomaterials

Carbon nanomaterials (CNMs) have been a remarkable material and impacted today's technology in various fields, such as enhancing agents for host material and environment-related applications. Green synthesis of CNMs gains attention as it requires low cost and less energy during the fabrications. In addition, the starting material is either environmental-friendly or a waste carbon compound that can be obtained from the household or catering industry. In this research, CNMs such as carbon nanotubes (CNTs) and graphitic carbon layers were synthesised using barbeque grease as carbon precursor via the chemical vapour deposition technique (CVD). The oil waste was analysed with gas chromatograph-mass spectrometry (GC–MS), and it showed that the oil waste contained a high amount of hydrocarbon chain such as pentadecane and 1-nonadecene, which decomposed into simple hydrocarbon bonding during the deposition and grew CNMs on the catalyst. SEM and TEM results showed that the CNTs with a diameter range of 42 ± 17 nm (outer) and 3.5 ± 0.5 nm (inner) were synthesised using the Ni catalyst. Raman and SEM revealed that the graphitic carbon layers with a D to G peak intensity ratio (I D /I G ) is 0.9898 were fabricated using Cu foil as the substrate. This research aims to discover novel and low-cost carbon precursors for the CVD system, to produce high-quality CNMs.

Realizing Toluene Deep Mineralization by Coupling Nonthermal Plasma and Nitrogen-Enriched Hollow Hybrid Carbon

Achieving excellent efficiency to mineralize volatile organic compounds (VOCs) under nonthermal plasma catalysis (NTP-catalysis) systems tremendously relies on the catalyst design. Herein, we report a dual-template strategy for synthesizing a core-shell structured nitrogen-enriched hollow hybrid carbon (N-HHC) by a facile pyrolysis of a Mn-ZIF-8@polydopamine core-shell precursor. N-HHC exhibits a remarkable plasma synergy effect and superior degradation efficiency for toluene (up to 90% with a specific input energy of 281 J/L), excellent CO2 selectivity (>45%), and byproduct-inhibiting capability. Such outstanding functionality of the developed N-HHC is uniquely attributed to its hollow multistage and channeling structure, high concentration of O3-decomposing species (pyrrolic and oxide pyridinic-N), and abundant ZnO active sites. Shedding light on an efficient synthetic strategy for designing an advanced nanocatalyst with enhanced VOC destruction in the NTP-catalysis system, the present results could be extended to design other N-doped metal/metal oxide-decorated hollow porous carbons for environment-related applications.

Insights into CO2 hydrates formation and dissociation at isochoric conditions using a rocking cell apparatus

In order to study the hydrate-liquid–vapour-equilibria (HLVE), the isochoric pressure search method is one of the most sought-after methods through which the characteristics of the hydrate formation and dissociation processes of a given hydrate-former substance can be traced. This method contains three temperature driven segments that are known as: (i) fast cooling step, (ii) isothermal step and (iii) a slow heating step applied to a given water + hydrate-former system under closed conditions. In this work, we have carried out a study to determine the effect of various variables on the formation/dissociation process of CO2 + H2O hydrate systems such as cooling rate, heating rate, isothermal segment temperature and its length, rocking rate, initial pressure and operating temperature. These variables may influence the characteristic shape of the p-T loops and thereby might affect the precise determination of kinetics and thermodynamics parameters. The experiments have been conducted using a rocking cell apparatus where nearly 50 experiments using 10 different versions of the isochoric pressure search method have been carried out. This work primarily shows practicalities of how to obtain the hydrate equilibrium curve more efficiently and accurately. The large number of experiments provide qualitative indications of the combined mass transfer and kinetics. This information might have implications towards the use of hydrate technology for energy and environmental related applications.

Exploring the effect of morphology and surface properties of nanoshaped Pd/CeO2 catalysts on CO2 hydrogenation to methanol

Catalytic CO2 hydrogenation to methanol is one of the important reactions for environmental-related applications. Pd/CeO2 catalysts with four different ceria morphologies, i.e. polyhedral, rod, cube and polygonal, and 5 wt% Pd loading were synthesized, and their catalytic characteristics and reaction mechanism were studied. Combining the results of N2 physisorption, XRD, Raman, CO2-TPD, Py-TPD and H2-TPR analyses suggests that PdO and PdxCe1−xO2-δ linkages are present in the Pd/CeO2 catalysts, which have different interactions with different exposed planes. Pd functionalized ceria with polyhedral morphology denoted as Pd/CeO2-NPH shows the highest specific surface area with exposed facets ({111}+{110}), responsible for the formation of more oxygen vacancy and higher extent of surface oxygen mobility, and higher number of acidic-basic sites on the catalysts surface, which contributed to improved catalytic activity and selectivity. XRD and Raman spectroscopy results revealed strong metal-support interactions for the most active catalyst by forming the PdxCe1−xO2-δ linkage, which improved the formation of surface oxygen vacancies and CO2 activation on the CeO2 support and promoted dissociation of H2 on the Pd metal. In-situ DRIFTS examination provided clear evidence for the formate reaction pathway of methanol synthesis. From a mechanistic point of view, the decomposition of surface carbonate species resulted in the formation of formate, which was further hydrogenated to form crucial methoxy species followed by methanol and CO as reaction products.

Assessment and Intercomparison of NOAA Daily Optimum Interpolation Sea Surface Temperature (DOISST) Version 2.1

AbstractThe NOAA Daily Optimum Interpolation Sea Surface Temperature dataset (DOISST) has recently been updated to v2.1 (January 2016–present). Its accuracy may impact the climate assessment, monitoring and prediction, and environment-related applications. Its performance, together with those of seven other well-known sea surface temperature (SST) products, is assessed by comparison with buoy and Argo observations in the global oceans on daily 0.25° × 0.25° resolution from January 2016 to June 2020. These seven SST products are NASA MUR25, GHRSST GMPE, BoM GAMSSA, UKMO OSTIA, NOAA GPB, ESA CCI, and CMC. Our assessments indicate that biases and root-mean-square difference (RMSDs) in reference to all buoys and all Argo floats are low in DOISST. The bias in reference to the independent 10% of buoy SSTs remains low in DOISST, but the RMSD is slightly higher in DOISST than in OSTIA and CMC. The biases in reference to the independent 10% of Argo observations are low in CMC, DOISST, and GMPE; also, RMSDs are low in GMPE and CMC. The biases are similar in GAMSSA, OSTIA, GPB, and CCI whether they are compared against all buoys, all Argo, or the 10% of buoy or 10% of Argo observations, while the RMSDs against Argo observations are slightly smaller than those against buoy observations. These features indicate a good performance of DOISST v2.1 among the eight products, which may benefit from ingesting the Argo observations by expanding global and regional spatial coverage of in situ observations for effective bias correction of satellite data.

Controlled preparation of magnetically separable BiOBr/BiFeO3 heterostructures by chemical etching process with enhanced visible light photocatalytic activities and anti-photocorrosion

ABSTRACT Novel magnetically separable BiOBr/BiFeO3 heterostructures were fabricated via a facile in situ hydrothermal chemical etching process using cetyltrimethyl-ammonium bromide (CTAB) and sulphuric acid as etching agents to react with BiFeO3 particles. The effects of solution pH and CTAB amount on the structure, morphology, and optical properties of the as-prepared samples were investigated. It was found that the best acidity of solution is pH = 3.0 for the formation of BiOBr/BiFeO3 heterostructures from BiFeO3 powder. Their photocatalytic activities and anti-photocorrosion behaviour were measured by the photocatalytical reduction of heavy metal ion Cr (VI) under visible-light irradiation. Experimental results show that the molar ratio of BiOBr to BiFeO3 contributed to different morphologies and photocatalytic activities of BiOBr/BiFeO3 composites. The optimised molar ratio in BiOBr/BiFeO3 composites was found to be 1:1. The photocatalytic reduction rate of Cr(VI) over 1:1 BiOBr/BiFeO3 composites was found to be 4.9 and 3.0 times higher than that of pure BiFeO3 and BiOBr, respectively. The hybridisation of BiOBr with BiFeO3 can markedly inhibit the photocorrosion of semiconductor BiFeO3. No obvious catalytic activity decrement can be found after five consecutive photocatalytic Cr (VI) reduction, which demonstrates the high structural stability of 1:1 BiOBr/BiFeO3. Furthermore, a possible photogenerated charge transfer process was proposed. The obviously enhanced photocatalytic activity could be ascribed to the formation of BiOBr-BiFeO3 heterojunction, accelerating the effective separation of photoexcited electron−hole pairs. This study suggests that the magnetically separable BiOBr/BiFeO3 heterostructures can be a promising photocatalyst for environment-related applications.

Engineering Co Vacancies for Tuning Electrical Properties of p-Type Semiconducting Co3O4 Films.

Spinel oxide Co3O4 has attracted more and more attention for energy- and environment-related applications. In order to tune the electrical properties of Co3O4, p-type semiconducting Co3O4 films were fabricated on the Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT), MgAl2O4 (MAO), and SrTiO3 substrates by reactive magnetron sputtering. The Co3O4 film on the MAO substrate exhibits perfect epitaxial growth. However, the Co3O4 film on the PMN-PT substrate presents dislocation defects between the [011] and [112] orientations. The special ferroelectric domain shape surface and phase transition of the PMN-PT substrate induce the higher concentration of Co vacancies in the Co3O4 film, which further reduce the resistivity by several orders of magnitude. The calculated results indicate that introducing Co vacancies can enhance the electrical properties of Co3O4 by building impurity levels near the Fermi level, which is beneficial to form free-moving holes in the valence band. The free-moving holes can also be accumulated/dissipated by the ferroelectric field effect of PMN-PT substrates, leading to upward/downward bending of conduction, valence bands, and low/high-resistance states. This work helps us to tune and improve the electrical properties of Co3O4.