Double Columnar Structure with a Nanogradient Composite for Increased Oxygen Diffusivity and Reduction Activity

The cathodic performances that can be achieved in solid oxide fuel cells (SOFCs), particularly in terms of oxygen diffusion, need to be improved so that high power densities can be produced at intermediate temperatures. Here, to improve the cathodic performance, a double columnar functional interlayer (DCFL) consisting of Sm_0.2Ce_0.8O_2?δ (SDC) and Sm_0.5Sr_0.5CoO_3?δ (SSC) is fabricated between a La_0.9Sr_0.1Ga_0.8Mg_0.2O_3?δ electrolyte film and a SSC cathode film with pulsed laser deposition. The DCFL has a rough surface morphology consisting of nanosized grains (with diameters less than 5 nm), and it is formed of small columns that grow at an angle of ca. 45° from the substrate. Inserting the DCFL causes the electrical conductivity of the cathode to increase significantly, and the power density obtained by using it in a metal‐supported SOFC is increased. Atomic resolution scanning transmission electron microscopy (TEM) images and density functional theory calculations confirm that the samarium atoms in the SDC columns and cobalt atoms in the SSC columns are located at the interfaces between SDC and SSC columns. Therefore, it is possible a SmCoO_3?δ nanogradient is formed, which may cause lattice distortions. The ¹⁸O₂ concentration is actually much higher in the DCFL than in either of SSC or SDC films.     

Creating Highly Active Atomic Layer Deposited NiO Electrocatalysts for the Oxygen Evolution Reaction

Atomic layer deposition (ALD) provides a promising route for depositing uniform thin coatings of electrocatalysts useful in many technologies, including the splitting of water. For materials such as NiO _x that readily form hydrous oxides, however, the smooth, compact films deposited by ALD may result in higher overpotentials due to low catalyst surface area compared to other deposition methods. Here, the use of ALD–NiO thin films as oxygen evolution reaction (OER) electrocatalysts is explored. Thin films of crystalline ALD­–NiO are deposited and OER activity is tested using cyclic voltammetry (CV). Fe incorporated from the electrolyte can increase the activity of NiO, and it is shown that the turnover frequency (TOF) increases tenfold by going from an Fe‐poor to Fe‐rich KOH electrolyte. Applying a potential exfoliates the NiO, increasing the number of electrochemically accessible Ni sites. Interestingly, by X‐ray photoelectron spectroscopy (XPS) and CV, it is found that an Fe‐rich electrolyte reduces the amount of restructuring and oxidation is found. It is shown that a high surface area, high TOF catalyst may be created by using a two‐step process in which the sample is sequentially conditioned in Fe‐poor then Fe‐rich KOH. This work highlights the importance of pretreatment on catalytic activity for compact NiO films deposited by ALD.     

Overcoming Electrode‐Induced Losses in Organic Solar Cells by Tailoring a Quasi‐Ohmic Contact to Fullerenes via Solution‐Processed Alkali Hydroxide Layers

It is shown that the performance of inverted organic solar cells can be significantly improved by facilitating the formation of a quasi‐ohmic contact via solution‐processed alkali hydroxide (AOH) interlayers on top of n‐type metal oxide (aluminum zinc oxide, AZO, and zinc oxide, ZnO) layers. AOHs significantly reduce the work function of metal oxides, and are further proven to effectively passivate defect states in these metal oxides. The interfacial energetics of these electron collecting contacts with a prototypical electron acceptor (C₆₀) are investigated to reveal the presence of a large interface dipole and a new interface state between the Fermi energy and the C₆₀ highest occupied molecular orbital for AOH‐modified AZO contacts. These novel interfacial gap states are a result of ground‐state electron transfer from the metal hydroxide‐functionalized AZO contact to the adsorbed molecules, which are hypothesized to be electronically hybridized with the contact. These interface states tail all the way to the Fermi energy, providing for a highly n‐doped (metal‐like) interfacial molecular layer. Furthermore, the strong “light‐soaking” effect is no longer observed in devices with a AOH interface.     

Biosynthesis of au nanoparticles by a marine bacterium and enhancing their catalytic activity through metal ions and metal oxides

The authors report that a marine Shewanella sp. CNZ-1 is capable of producing Au NPs under various conditions. Results showed that initial concentration of Au(III), pH values and electron donors affected nucleation of Au NPs by CNZ-1, resulting in different apparent color of the as-obtained bio-Au NPs, which were further characterized by UV-Vis, TEM, XRD, and XPS analyses. Mechanism studies revealed that Au(III) was first reduced to Au(I) and eventually reduced to EPS-coated Au⁰ NPs. FTIR and FEEM analyses revealed that some amides and humic acid-like matters were involved in the production of bio-Au NPs through CNZ-1 cells. In addition, the authors also found that the catalytic activity of bio-Au NPs for 4-nitrophenol (4-NP) reduction could be enhanced by various metal ions (Ca²⁺, Cu²⁺, Co²⁺, Fe²⁺, Fe³⁺, Ni²⁺, Sr²⁺, and Cr³⁺) and metal oxides (Fe₃O₄, Al₂O₃, and SiO₂), which is beneficial for their further practical application. The maximum zero-order rate constant k ₁ and first-order rate constant k₂ of all metal ions/oxides supplemented systems can reach 99.65 mg/(L^.min) and 2.419 min⁻¹, which are 11.3- and 12.6-fold higher than that of control systems, respectively. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2727, 2019.     

Abortiporus biennis tolerance to insoluble metal oxides: oxalate secretion, oxalate oxidase activity, and mycelial morphology

The ability of Abortiporus biennis to tolerate and solubilize toxic metal oxides (Cu₂O, Al₂O₃, ZnO, CuFe₂O₄Zn, CdO, and MnO₂) incorporated into agar media was investigated and the growth rate, oxalic acid secretion, and mycelial morphology were monitored. Among the tested metal oxides, formation of clear zones underneath the mycelium growing on Cu₂O- and ZnO-amended plates was observed. ZnO, CdO and Cu₂O caused the highest rate of fungal growth inhibition. An increased level of oxalic acid concentration was detected as a response of A. biennis to the presence of Cu₂O, MnO₂, ZnO and CuFe₂O₄Zn in growth medium. The oxalate oxidase (OXO) was found to be responsible for oxalic acid degradation in A. biennis cultivated in metal-amended media. An increased level of OXO was observed in media amended with Cu₂O, ZnO and MnO₂. Confocal microscopy used in this study revealed changes in mycelial morphology which appeared as increased hyphal branching, increased septation and increased spore number.     

Improved Performance and Reliability of p‐i‐n Perovskite Solar Cells via Doped Metal Oxides

Perovskite photovoltaics (PVs) have attracted attention because of their excellent power conversion efficiency (PCE). Critical issues related to large‐area PV performance, reliability, and lifetime need to be addressed. Here, it is shown that doped metal oxides can provide ideal electron selectivity, improved reliability, and stability for perovskite PVs. This study reports p‐i‐n perovskite PVs with device areas ranging from 0.09 cm² to 0.5 cm² incorporating a thick aluminum‐doped zinc oxide (AZO) electron selective contact with hysteresis‐free PCE of over 13% and high fill factor values in the range of 80%. AZO provides suitable energy levels for carrier selectivity, neutralizes the presence of pinholes, and provides intimate interfaces. Devices using AZO exhibit an average PCE increase of over 20% compared with the devices without AZO and maintain the high PCE for the larger area devices reported. Furthermore, the device stability of p‐i‐n perovskite solar cells under the ISOS‐D‐1 is enhanced when AZO is used, and maintains 100% of the initial PCE for over 1000 h of exposure when AZO/Au is used as the top electrode. The results indicate the importance of doped metal oxides as carrier selective contacts to achieve reliable and high‐performance long‐lived large‐area perovskite solar cells.     

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO₃ (001) and DyScO₃ (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca₂Nb₃O₁₀^- nanosheets were used, prepared by delamination of their layered parent compound HCa₂Nb₃O₁₀. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.     

V2O5 Nano‐Electrodes with High Power and Energy Densities for Thin Film Li‐Ion Batteries

Nanostructured V₂O₅ thin films have been prepared by means of cathodic deposition from an aqueous solution made from V₂O₅ and H₂O₂ directly on fluorine‐doped tin oxide coated (FTO) glasses followed by annealing at 500°C in air, and studied as film electrodes for lithium ion batteries. XPS results show that the as‐deposited films contained 15% V⁴⁺, however after annealing all the vanadium is oxidized to V⁵⁺. The crystallinity, surface morphology, and microstructures of the films have been investigated by means of XRD, SEM, and AFM. The V₂O₅ thin film electrodes show excellent electrochemical properties as cathodes for lithium ion intercalation: a high initial discharge capacity of 402 mA h g^?1 and 240 mA h g^?1 is retained after over 200 cycles with a discharging rate of 200 mA g^?1 (1.3 C). The specific energy density is calculated as 900 W h kg^?1 for the 1^st cycle and 723 W h kg^?1 for the 180^th cycle when the films are tested at 200 mA g^?1 (1.3 C). When discharge/charge is carried out at a high current density of 10.5 A g^?1 (70 C), the thin film electrodes retain a good discharge capacity of 120 mA h g^?1, and the specific power density is over 28 kW kg^?1.     

Adsorption of Cu and Zn onto Mn/Fe Oxides and Organic Materials in the Extractable Fractions of River Surficial Sediments

The roles of the extractable components (Mn oxides, Fe oxides, and organic materials) of surficial sediments in controlling metals adsorption were investigated. Cu and Zn adsorptions were conducted before and after the surficial sediments extracted with hydroxylamine hydrochloride, an oxalate solution, and H ₂ O ₂ , respectively. The extraction removed target components with extraction efficiencies from 63 to 98%. Nonlinear regression analyses of Cu and Zn adsorptions based on the assumption of additive Langmuir adsorption isotherm were employed to estimate the relative contributions of sediment components to Cu and Zn adsorptions. The results indicate that the greatest contribution to total Cu and Zn adsorption to the surficial sediments on a molar basis was from Mn oxides in the extractable fractions. Both Cu and Zn adsorption capacities of Mn oxides exceeded those of Fe oxides by approximately one order of magnitude, fewer roles were attributed to the adsorption of organic material (OM), and the estimated contribution of the residual fraction to total Cu and Zn adsorption was insignificant. These information implied that the roles of metal oxides (Fe and Mn oxides) in the extractable form of the surficial sediments, especially Mn oxides, was the most important component in controlling heavy metal transportation in aquatic environments.     

Overcoming the “Light‐Soaking” Issue in Inverted Organic Solar Cells by the Use of Al:ZnO Electron Extraction Layers

A common phenomenon of organic solar cells (OSCs) incorporating metal‐oxide electron extraction layers is the requirement to expose the devices to UV light in order to improve device characteristics – known as the so‐called “light‐soaking” issue. This behaviour appears to be of general validity for various metal‐oxide layers, various organic donor/acceptor systems, and regardless if single junction devices or multi stacked cells are considered. The requirement of UV exposure of OSCs may impose severe problems if substrates with limited UV transmission, UV blocking filters or UV to VIS down‐conversion concepts are applied. In this paper, we will demonstrate that this issue can be overcome by the use of Al doped ZnO (AZO) as electron extraction interlayer. In contrast to devices based on TiO_x and ZnO, the AZO devices show well‐behaved solar cell characteristics with a high fill factor (FF) and power conversion efficiency (PCE) even without the UV spectral components of the AM1.5 solar spectrum. As opposed to previous claims, our results indicate that the origin of s‐shaped characteristics of the OSCs is the metal‐oxide/organic interface. The electronic structures of the TiO_x/fullerene and AZO/fullerene interfaces are studied by photoelectron spectroscopy, revealing an electron extraction barrier for the TiO_x/fullerene case and facilitated electron extraction for AZO/fullerene. These results are of general relevance for organic solar cells based on various donor acceptor active systems.     

Enhanced Cyclability of Lithium–Oxygen Batteries with Electrodes Protected by Surface Films Induced via In Situ Electrochemical Process

Although the rechargeable lithium–oxygen (Li–O₂) batteries have extremely high theoretical specific energy, the practical application of these batteries is still limited by the instability of their carbon‐based air‐electrode, Li metal anode, and electrodes, toward reduced oxygen species. Here a simple one‐step in situ electrochemical precharging strategy is demonstrated to generate thin protective films on both carbon nanotubes (CNTs), air‐electrodes and Li metal anodes simultaneously under an inert atmosphere. Li–O₂ cells after such pretreatment demonstrate significantly extended cycle life of 110 and 180 cycles under the capacity‐limited protocol of 1000 mA h g^?1 and 500 mA h g^?1, respectively, which is far more than those without pretreatment. The thin‐films formed from decomposition of electrolyte during in situ electrochemical precharging processes in an inert environment, can protect both CNTs air‐electrode and Li metal anode prior to conventional Li–O₂ discharge/charge cycling, where reactive reduced oxygen species are formed. This work provides a new approach for protection of carbon‐based air‐electrodes and Li metal anodes in practical Li–O₂ batteries, and may also be applied to other battery systems.     

Atomic Layer Deposition of Tin Monosulfide Thin Films

Thin film solar cells made from earth‐abundant, non‐toxic materials are needed to replace the current technology that uses Cu(In,Ga)(S,Se)₂ and CdTe, which contain scarce and toxic elements. One promising candidate absorber material is tin monosulfide (SnS). In this report, pure, stoichiometric, single‐phase SnS films were obtained by atomic layer deposition (ALD) using the reaction of bis(N,N′‐diisopropylacetamidinato)tin(II) [Sn(MeC(N‐ⁱPr)₂)₂] and hydrogen sulfide (H₂S) at low temperatures (100 to 200 °C). The direct optical band gap of SnS is around 1.3 eV and strong optical absorption (α > 10⁴ cm^?1) is observed throughout the visible and near‐infrared spectral regions. The films are p‐type semiconductors with carrier concentration on the order of 10¹⁶ cm^?3 and hole mobility 0.82–15.3 cm²V^?1s^?1 in the plane of the films. The electrical properties are anisotropic, with three times higher mobility in the direction through the film, compared to the in‐plane direction.     

Use of surface analysis techniques to determine the mechanisms of metal corrosion in animal buildings

Recognizing the severity of metal corrosion problems in animal buildings has prompted an attempt to finally determine the fundamental causes of corrosion. Based on a two-year field test, this paper investigated the corrosion mechanisms of various metal products exposed in three animal buildings by analyzing the composition of corrosion products, using advanced material surface analysis techniques, including energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analyses. Data from these analyses showed that the corrosion products were mainly iron oxides (Fe₂O₃, Fe₃O₄, and FeO) on uncoated 1010 carbon steel and zinc oxides, sulfides, and carbonates on galvanized steel and galvalume (ZnO, ZnS, Zn(CO)₃, and Al₂O₃). Thus, it could be concluded that the fundamental mechanisms of metal corrosion in animal buildings are similar to the classic corrosion mechanisms and the high corrosion rates of metal products in animal buildings are due to the presence of high moisture levels.     

Constructing a AZO/TiO2 Core/Shell Nanocone Array with Uniformly Dispersed Au NPs for Enhancing Photoelectrochemical Water Splitting

Constructing core/shell nanostructures with optimal structure and composition could maximize the solar light utilization. Here, using an Al nanocone array as a substrate, a well‐defined regular array of AZO/TiO₂ core/shell nanocones with uniformly dispersed Au nanoparticles (AZO/TiO₂/Au NCA) is successfully realized through three sequential steps of atomic layer deposition, physical vapor deposition, and annealing processes. By tuning the structural and compositional parameters, the advantages of light trapping and short carrier diffusion from the core/shell nanocone array, as well as the surface plasmon resonance and catalytic effects from the Au nanoparticles can be maximally utilized. Accordingly, a remarkable photoelectrochemical (PEC) performance can be acquired and the photocurrent density of the AZO/TiO₂/Au NCA electrode reaches up to 1.1 mA cm^?2 at 1.23 V, versus reversible hydrogen electrode (RHE) under simulated sunlight illumination, which is five times that of a flat AZO/TiO₂ electrode (0.22 mA cm^?2). Moreover, the photoconversion of the AZO/TiO₂/Au NCA electrode approaches 0.73% at 0.21 V versus RHE, which is one of the highest values with the lowest applied bias ever reported in Au/TiO₂ PEC composites. These results demonstrate a feasible route toward the scalable fabrication of well‐modulated core/shell nanostructures and can be easily applied to other metal/semiconductor composites for high‐performance PEC.     

Computational Design and Preparation of Cation‐Disordered Oxides for High‐Energy‐Density Li‐Ion Batteries

Cation‐disordered lithium‐excess metal oxides have recently emerged as a promising new class of high‐energy‐density cathode materials for Li‐ion batteries, but the exploration of disordered materials has been hampered by their vast and unexplored composition space. This study proposes a practical methodology for the identification of stable cation‐disordered rocksalts. Here, it is established that the efficient method, which makes use of special quasirandom structures, correctly predicts cation‐ordering strengths in agreement with accurate Monte‐Carlo simulations and experimental observations. By applying the approach to the composition space of ternary oxides with formula unit LiA_0.5B_0.5O₂ (A, B: transition metals), this study discovers a previously unknown cation‐disordered structure, LiCo_0.5Zr_0.5O₂, that may function as the basis for a new class of cation‐disordered cathode materials. This computational prediction is confirmed experimentally by solid‐state synthesis and subsequent characterization by powder X‐ray diffraction demonstrating the potential of the computational screening of large composition spaces for accelerating materials discovery.     

Mixed Valence Tin Oxides as Novel van der Waals Materials: Theoretical Predictions and Potential Applications

Van der Waals (vdW) heterostructures, which can be assembled by combining 2D atomic crystals in a precisely chosen sequence, enable a wide range of potential applications in optoelectronics, photovoltaics, and photocatalysis. However, the difficulty of peeling isolated atomic planes and the lattice mismatch between different materials is the main obstacle to hinder vdW materials from more practical applications. In this work, the mixed valence tin oxides, Sn_xO_y (0.5 < x/y < 1), are proposed as a new member of vdW materials and these mixed valence tin oxides show promise to overcome the above‐mentioned obstacle. Density‐functional theory calculations are combined with an evolutionary algorithm to predict the crystal structures of a series of previously reported tin oxides (Sn₂O₃, Sn₃O₄, Sn₄O₅, and Sn₅O₆), unreported compositions (Sn₇O₈, Sn₉O₁₀, and Sn₁₁O₁₂), and a new β ‐ SnO phase. These structures consist of β‐SnO, Sn₂O₃, and Sn₃O₄ monolayers. Their band gaps can be engineered in the 1.56–3.25 eV range by stacking the monolayers appropriately. The band gap depends linearly on the interlayer distance, as understood from interlayer Sn²⁺–Sn²⁺ and intralayer Sn²⁺–O interactions. Sn_xO_y structures exhibit high photoabsorption coefficients and suitable band‐edge positions for photoexcited H₂ evolution; this indicates potential for environmentally benign solar energy conversion in photovoltaic and photocatalytic applications.     

Characterization of Gaseous Ozone Decomposition in Soil

Laboratory scale batch experiments were performed to investigate the decomposition characteristics of gaseous ozone in porous media. The decomposition rates of gaseous ozone in several solid media were determined, and the relationship of moisture content with sorbed ozone molecules was evaluated. Ozone decomposition in control and glass beads packed columns followed second-order reaction kinetics, while ozone consumption in a sand-packed column demonstrated first-order kinetics with a rate constant of 0.0109 min^?1 and half-life of 1.0 h. The presence of typical metal oxides in the soil resulted in ozone consumption rates in the following order: hematite (Fe₂O₃) > silica-alumina (SiO₂Al₂O₃) > alumina (Al₂O₃) > silica (SiO₂). Ozone decomposition was highly dependent upon soil moisture content. Over 90% of the total ozone mass decomposed in the field soil with moisture content at less than 1 wt%, whereas as low as 5–15% of the total ozone mass degraded with moisture content at more than 2 wt%. In conclusion, ozone decomposition in soils was primarily controlled not only by soil organic matter but also by reactive metal oxides on the soil surface. These two factors were shown to be highly dependent upon soil moisture content.     

Retarded Charge–Carrier Recombination in Photoelectrochemical Cells from Plasmon‐Induced Resonance Energy Transfer

N‐type metal oxides such as hematite (α‐Fe₂O₃) and bismuth vanadate (BiVO₄) are promising candidate materials for efficient photoelectrochemical water splitting; however, their short minority carrier diffusion length and restricted carrier lifetime result in undesired rapid charge recombination. Herein, a 2D arranged globular Au nanosphere (NS) monolayer array with a highly ordered hexagonal hole pattern (hereafter, Au array) is introduced onto the surface of photoanodes comprised of metal oxide films via a facile drying and transfer‐printing process. Through plasmon‐induced resonance energy transfer, the Au array provides a strong electromagnetic field in the near‐surface area of the metal oxide film. The near‐field coupling interaction and amplification of the electromagnetic field suppress the charge recombination with long‐lived photogenerated holes and simultaneously enhance the light harvesting and charge transfer efficiencies. Consequently, an over 3.3‐fold higher photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) is achieved for the Au array/α‐Fe₂O₃. Furthermore, the high versatility of this transfer printing of Au arrays is demonstrated by introducing it on the molybdenum‐doped BiVO₄ film, resulting in 1.5‐fold higher photocurrent density at 1.23 V versus RHE. The tailored metal film design can provide a potential strategy for the versatile application in various light‐mediated energy conversion and optoelectronic devices.     

中亚热带山区土壤不同形态铁铝氧化物对团聚体稳定性的影响

以福建省三明市本底条件一致的三片林分的土壤作为研究对象,采用湿筛法测定了水稳定性团聚体粒径分布,分析了不同形态铁铝氧化物含量与0.25 mm大团聚体数量及团聚体平均重量直径(MWD)的关系。结果表明:(1)不同形态铁铝氧化物含量呈现出米槠次生林米槠人工林杉木人工林,游离结晶态(Fed、Ald)无定形(Feo、Alo)络合态(Fes、Als)。(2)0.25 mm大团聚体含量呈现米槠次生林米槠人促林杉木人工林,林分之间差异显著,MWD值的趋势与之相似。(3)线性回归分析表明:不同形态铁铝氧化物均与0.25 mm水稳定性大团聚体数量及MWD值达到显著甚至极显著相关,但通过分析相关系数R和显著性P说明氧化铝可能比氧化铁更有助于大团聚体的形成与稳定,无定形及络合态铁铝氧化物比游离态铁铝氧化物更能促进大团聚体的形成与稳定。