Search

Photoelectrochemical (PEC) technology has been proved a promising approach to solve the problems of energy shortages and environmental pollution damages. It can convert unlimited solar energy resources into energy forms needed by mankind. The development of highly efficient photoanodes is a key step in realizing the large-scale practical application of PEC systems. However, the development of PEC photoanodes has been severely hindered by the issues of easy recombination of photo-generated charge carriers, low photon-to-electron conversion efficiency, poor photo-corrosion resistance, and low catalytic activity. Therefore, constructing high-performance and stable photoanodes is an urgent research field to promote the progress of PEC technology. The atomically thin molybdenum disulfide (AT-MoS2) with unique physical and chemical properties has been widely applied in the fabrication of PEC photoanodes. The AT-MoS2 based photoanodes have exhibited excellent PEC performance, which providing promising candidates for ideal PEC application. Here, we summarize the fundamental natures of MoS2 and present the research efforts in the preparation of AT-MoS2 based photoanodes. Strategies for the fabrication of high-efficient AT-MoS2 based photoanodes are emphasized to provide guidelines to advance emerging PEC photoanodes. Besides, perspectives for the development of more efficient AT-MoS2 based photoanodes are proposed.

Defect sites on oxide semiconductors play a crucial role in promoting photocatalytiperformance and modulating the bandgap structure of photocatalysts. However, the role of interfacial coordinatively unsaturated defect sites between metal and oxide in photocatalysis is still under debate. So, we designed an experiment to probe the role of interfacial coordinatively unsaturated defect sites. In this work, a series of Ti/TiO2 photocatalysts with varying concentrations of interfacial Ti3+ sites were prepared through an epitaxial growth method under hydrothermal conditions. Through experimental and computational investigations, the roles of interfacial defect sites were discussed in detail. On the one hand, the interfacial coordinatively unsaturated Ti3+ sites could act as visible-light-responsive sites in photocatalytic reactions due to the overlap and hybridization of multiple electronic orbitals. On the other hand, the Ti/TiO2 interface exhibited a certain degree of metallic character near the Fermi level because of the partial delocalization and redistribution of electrons, facilitating the charge migration and separation across the metal-oxide interface. Consequently, the obtained Ti/TiO2 catalysts showed notably enhanced charge transfer efficiency and visible light photocatalytic activity compared to their pristine counterparts. This work may provide a new perspective to interfacial defect engineering in classic metal/oxide heterojunction photocatalysts and figure a more precise direction to synthesize higher effective photocatalysts for environmental governance.

Ion-irradiated FeCr alloys are useful for understanding and predicting neutron damage in the structural steels of future nuclear reactors. Previous studies have largely focused on the structure of irradiation induced defects, probed by transmission electron microscopy (TEM), as well as changes in mechanical properties. Across these studies, a wide range of irradiation conditions has been employed on samples with different processing histories, which complicates the analysis of the relationship between defect structures and material properties. Furthermore, key properties, such as irradiation-induced changes in thermal transport and lattice strain, are little explored. Here we present a systematic study of Fe3Cr, Fe5Cr and Fe10Cr binary alloys implanted with 20 MeV Fe3+ ions to nominal doses of 0.01 dpa and 0.1 dpa at room temperature. Nanoindentation, transient grating spectroscopy (TGS) and X-ray micro-beam Laue diffraction were used to study the changes in hardness, thermal diffusivity and strain in the material as a function of damage and Cr content. Our results suggest that Cr leads to an increased retention of irradiation-induced defects, causing substantial changes in hardness and lattice strain. However, thermal diffusivity varies little with increasing damage and instead degrades significantly with increasing Cr content in the material. We find significant lattice strains even in samples exposed to a nominal displacement damage of 0.01 dpa. The defect density predicted from the lattice strain measurements is significantly higher than that observed in previous TEM studies, suggesting that TEM may not fully capture the irradiation-induced defect population. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

It is well-known that steels always oxidize faster in the environments containing water vapour than in dry oxygen. Due to the difficulties in obtaining necessary experimental scale of observations, the mechanisms responsible for the steam-accelerated oxidation are still unclear. Through a combination of multiscale characterization techniques, the surface oxide film formed on an Fe-17Cr-9Ni stainless steel after exposure to high-temperature steam has been studied in detail. The characterization results obtained in this study reveal that the inner oxide layer actually consists of two phases Fe-Ni austenite and FeCr2O4 oxide, which formed due to internal oxidation. The classic internal oxidation model underestimates the thickness of the inner oxide layer by one order of magnitude. This difference can be explained by the existence of fast diffusion channels in the inner oxide layer. This study provides direct evidence of a high density of nanopores in the oxide phase of the internal oxide layer, which can act as fast-diffusion channels if interconnected, and proposes their mechanisms of formation, a consequence of water dissociation-induced protons promoting the formation, migration, and clustering of both cation and anion vacancies.

A coupled electrochemical system (CES) for the electroreduction of CO2 to formate (ERCF) and simultaneous degradation of organic pollutants is a promising approach for CO2 conversion. Cathode material is a critical component of CES. However, the poor performance and complexity of synthesis limit its real application. Here, we report a Bi-based binder-free gas diffusion electrode (EBGDE) as a high-performance cathode for CES. The EBGDE was fabricated via direct electrodeposition of Bi nanosheets on a gas diffusion layer. By optimizing the deposition time of Bi nanosheets, a good Faraday efficiency (91.46 ± 6.58%) and formate production rate (1849.96 ± 127.69 μmol m−2 s−1) were obtained. Simultaneously, the methyl orange decolorization efficiency and chemical oxygen demand removal efficiency reached 100% and 55.25 ± 6.87%, respectively. This performance towards ERCF is better than recently reported ERCF electrodes. It probably results from the excellent performance of associated Bi-nanosheets catalysts, a high electroactive surface area, as well as fast electron transfer in the EBGDE. This work offers design rules to fabricate high-performance cathode materials for CES in industrial applications.

In-situ heavy ion (1 MeV Kr2+) irradiation was carried out to investigate the evolution of irradiation induced lattice defects at room temperature and the stability of β-Zr under irradiation at temperatures ranging from 150 to 350 °C. It was found that the irradiation induced defects started to appear at a dose between 0.5 dpa and 0.75 dpa, which is relatively high compared to the case for α-Zr. The number density of dislocation loops increased exponentially with fluence, with an exponential index ∼3.52. The statistical results show that the electron beam with which in-situ observation was carried out had an influence on the size of the dislocation loops. The g·b analysis shows that dislocation loops with Burgers vector ½ 1 ¯ 11> and are both present in the sample after irradiation to 1.5 dpa. ω phase particles precipitate out during irradiation at 250 and 350 °C, as a result of the combination of the thermal treatment and irradiation enhanced concentration of point defects.

A direct comparison between the microstructural evolution during the annealing of a TEM thin foil (thickness ~100 nm) and the bulk material of Zr-2.5Nb-0.5Cu alloy is presented. The results indicate that at an intermediate temperature, (550 °C), diffusion-controlled phenomena such as boundary migration and precipitate coarsening are retarded in the thin foil due to a thickness effect. At high temperature, (815 °C), the chain of transformations a) Widmanstatten → α + β, b) precipitate dissolution in the matrix and c) precipitation at the β phase is observed in the bulk material. In the thin foil, however, sufficient activation energy for the first transformation is not provided; consequently, growth of the initial precipitates with a smaller energy barrier progresses. Possible transformation retardation mechanisms in thin foils are discussed.

A series of solid electrolyte cells with La0.8Sr0.2MnO3 (LSM)-Ce0.8Sm0.2O1.9 (SDC) composite cathodes was fabricated for the electrochemical decomposition of nitric oxide (NO). The LSM and SDC powders were synthesized by a combined EDTA-citrate method. Thermogravimetry with differential scanning calorimetry, X-ray diffraction analysis, scanning and transmission electron microscope with electron diffraction were performed to characterize the synthesized powders. The NO conversions and power consumptions of the solid electrolyte cells with the cathodes sintered at 900–1200 °C were evaluated. The electrochemical properties, microstructures, and crystalline phases of the cathodes were further studied by electrochemical impedance spectrum, scanning electron microscope and X-ray diffraction, respectively. The NO conversions and electrochemical performances of the cells at different operating temperature were also investigated. It was concluded that the LSM and SDC powders calcined at 900 °C both showed good crystal structures with high purity. The cell with the cathode sintered at 1100 °C had the highest NO conversion of 65.4% and the lowest power consumption of 0.2024 W under 80 mA applied current. The total polarization resistances of the cells with the cathodes sintered at 900–1200 °C were 63.32, 41.75, 38.11 and 97.57 Ω cm2 in 800 ppm NO, respectively. The cathode sintered at 900 °C had an incompact structure and connected with the electrolyte loosely, thereby impeding the NO adsorption on the cathode surface and the transfer of O2− from three phase boundary (TPB) to electrolyte. The excess sintering temperature of 1200 °C resulted in a dense structure of cathode and La2Zr2O7 formation at the interface between the cathode and electrolyte, thereby leading to a poor NO decomposition performance. This study also found that the NO conversion increased with the rise of operating temperature and 600 °C was not suitable for operation because of the electrode degradation caused by the overvoltage.

NOx is a significant atmospheric pollutant triggering haze weather. The existing DeNOx technology has drawbacks of needing additional reducing agent and high working temperature. In order to overcome those defects, a novel La0.6Sr0.4Fe0.8Mn0.2O3 (LSFM)-modified gas diffusion electrode (GDE) was prepared to establish an in-situ electrochemical DeNOx process. The DeNOx efficiency was enhanced by increasing Nafion and polytetrafluoroethylene (PTFE) content in the GDE within an appropriate range. Nafion created the proton transport pathway of electrolyte-Nafion-three phase interfaces (TPIs) and PTFE improved the hydrophobic gas channels. The highest DeNOx efficiency of 71.1% was obtained with inlet NOx of 1000 ppm under ambient temperature (25 °C) when the mass ratio of LSFM:Nafion:PTFE was 1:0.117:0.23. In the electrochemical DeNOx process, i) NOx was absorbed by the gas diffusion layer and then transferred to the catalyst layer through the hydrophobic channels; ii) NOx was electrochemically decomposed to N2 and O2− under the catalysis of LSFM; iii) O2− was transformed to OH− on the TPIs by combining with H+ and oxidized to O2 in the anode. Simultaneously N2 was released. Its advantages of no reducing agent, mild operating condition and high energy-efficiency indicate great potential for practical application.

In this paper, 40 MeV Zr ion irradiation of Zr-2.5Nb pressure tube alloy was carried out, delivering a damage layer 6.5 μm deep. Uniaxial micropillar compression experiments along the tube axial (AD) and transverse directions (TD) were conducted. Irradiation was found to alter the deformation mechanisms and to increase the yield strength more in the AD oriented pillars than TD pillars for irradiation up to 0.6 dpa. This anisotropy in response is discussed in terms of the limitations of the micropillar compression method and the different deformation mechanisms which are activated in each orientation. The anisotropic hardening effect of -type dislocation loops on prismatic , basal , and pyramidal slip systems is also discussed. The micropillar compression results were also compared with nanoindentation results conducted on the same material.

Combining spatially resolved X-ray Laue diffraction with atomic-scale simulations, we observe how ion-irradiated tungsten undergoes a series of non-linear structural transformations with increasing irradiation exposure. Nanoscale defect-induced deformations accumulating above 0.02 displacements per atom (dpa) lead to highly fluctuating strains at ~0.1 dpa, collapsing into a driven quasi-steady structural state above ~1 dpa. The driven asymptotic state is characterized by finely dispersed vacancy defects coexisting with an extended dislocation network, and exhibits positive volumetric swelling due to the creation of new crystallographic planes through self-interstitial coalescence, but negative lattice strain., Comment: 9 pages, 9 figures, in print with PRL

With the aim of relieving the serious environmental and climate issues arising from excessive emission of anthropogenic CO2, extensive solid absorbents have been developed for CO2 capture. Among them, porous boron nitride (BN) is considered an ideal candidate due to its high specific surface area, abundant structural defects, low density, and outstanding chemical inertness. Herein, BN absorbents were synthesized from pyrolysis of melamine-boric acid precursors, and the effect of pyrolysis temperature (900, 1000, 1050 and 1100 °C) on the properties and performances was investigated. Various characterizations were performed to evaluate the physicochemical properties and CO2 uptake capacities of BN absorbents. The result demonstrated that a carbon-doped BN structure was achieved instead of a pure BN material, and the carbonization degree was enhanced with the increase of pyrolysis temperatures. BN absorbent pyrolyzed at 1100 °C exhibited the highest CO2 adsorption capacity of 3.71 mmol/g (273 K). The reason should be that the doping of carbon in the framework of BN contributed to the formation of abundant micropores, which enhanced the physical adsorption by offering more adsorption sites. At the same time, more negative charges on BN were induced by structural defects, which favored the chemical adsorption of CO2 by invoking charge-induced chemisorption interaction. This study clarified the role of pore structure and electronic structure defects in CO2 adsorption capacity of carbon-doped BN, which would open up more spacious avenues for the development of promising BN-based absorbents, or even catalysts.

Coupling of nano-indentation and crystal plasticity finite element (CPFE) simulations is widely used to quantitatively probe the small-scale mechanical behaviour of materials. Earlier studies showed that CPFE can successfully reproduce the load-displacement curves and surface morphology for different crystal orientations. Here, we report the orientation dependence of residual lattice strain patterns and dislocation structures in tungsten. For orientations with one or more Burgers vectors close to parallel to the sample surface, dislocation movement and residual lattice strains are confined to long, narrow channels. CPFE is unable to reproduce this behaviour, and our analysis reveals the responsible underlying mechanisms.

Using transient grating spectroscopy (TGS) we measure the thermal diffusivity of tungsten exposed to different levels of 20 MeV self-ion irradiation. Damage as low as 3.2 x 10^-4 displacements per atom (dpa) causes a measurable reduction in thermal diffusivity. Doses of 0.1 dpa and above, up to 10 dpa, give a degradation of around 55% from the pristine value at room temperature. Using a kinetic theory model, the density of irradiation-induced point defects is estimated based on the measured changes in thermal diffusivity as a function of dose. These predictions are compared with point defect and dislocation loop densities observed in transmission electron microscopy (TEM). Molecular dynamics (MD) predictions are combined with the TEM observations to estimate the density of point defects associated with defect clusters too small to be probed by TEM. When these "invisible" defects are accounted for, the total point defect density agrees well with that estimated from TGS for a range of doses spanning 3 orders of magnitude. Kinetic theory modelling is also used to estimate the thermal diffusivity degradation expected due to TEM-visible and invisible defects. Finely distributed invisible defects appear to play a much more important role in the thermal diffusivity reduction than larger TEM-visible dislocation loops. This work demonstrates the capability of TGS, in conjunction with kinetic theory models, to provide rapid, quantitative insight into defect densities and property evolution in irradiated materials., The following article has been revised and submitted to Acta Materialia. After it is published, it will be found at https://www.journals.elsevier.com/acta-materialia

Developing a comprehensive understanding of the modification of material properties by neutron irradiation is important for the design of future fission and fusion power reactors. Self-ion implantation is commonly used to mimic neutron irradiation damage, however an interesting question concerns the effect of ion energy on the resulting damage structures. The reduction in the thickness of the implanted layer as the implantation energy is reduced results in the significant quandary: Does one attempt to match the primary knock-on atom energy produced during neutron irradiation or implant at a much higher energy, such that a thicker damage layer is produced? Here we address this question by measuring the full strain tensor for two ion implantation energies, 2 MeV and 20 MeV in self-ion implanted tungsten, a critical material for the first wall and divertor of fusion reactors. A comparison of 2 MeV and 20 MeV implanted samples is shown to result in similar lattice swelling. Multi-reflection Bragg coherent diffractive imaging (MBCDI) shows that implantation induced strain is in fact heterogeneous at the nanoscale, suggesting that there is a non-uniform distribution of defects, an observation that is not fully captured by micro-beam Laue diffraction. At the surface, MBCDI and high-resolution electron back-scattered diffraction (HR-EBSD) strain measurements agree quite well in terms of this clustering/non-uniformity of the strain distribution. However, MBCDI reveals that the heterogeneity at greater depths in the sample is much larger than at the surface. This combination of techniques provides a powerful method for detailed investigation of the microstructural damage caused by ion bombardment, and more generally of strain related phenomena in microvolumes that are inaccessible via any other technique., Comment: Please refer to the supplementary information and movies SM1-3 for data visualisation

The microstructure of the surface oxide film formed on an Fe-9Cr Ferritic-Martensitic (F-M) steel after exposure to deaerated high-temperature steam at 600°C for 100 h has been analyzed in detail by advanced characterization techniques. The surface oxide film has been revealed to have a triplex structure, including an outer oxide layer, an inner oxide layer, and an internal oxide layer. Although the outer and inner oxide layers are continuous, the internal oxide layer has been proved to consist of interconnected metallic and chromite phases, which is a typical feature of internal oxidation. The formation mechanisms of each layer have been discussed, finding that, contrary to what the available space model suggests, an external oxidation is not the controlling oxidation mechanism of F-M steels in high-temperature steam. The higher resolution used in this study confirms that the controlling mechanism is internal oxidation.

Displacive transformations have been widely reported in metals, alloys and ceramics, but rarely reported to be important in the aqueous corrosion of alloys. We report here our analysis of the formation of the hexagonal-ZrO suboxide during the aqueous corrosion of α-Zr alloys and propose this to be a paraequilibrium displacive transformation with the rate controlled by oxygen diffusion. Two orientation relationships were identified between α-Zr and hexagonal-ZrO, ( 0002 ) α − Z r ∥ ( 1 ¯ 011 ) h − Z r O and [ 2 ¯ 110 ] α − Z r ∥ [ 10 1 ¯ 2 ] h − Z r O or ( 0002 ) α − Z r ∥ ( 22 4 ¯ 1 ¯ ) h − Z r O and [ 2 ¯ 110 ] α − Z r ∥ [ 1 1 ¯ 01 ] h − Z r O , with the first one more commonly observed. No specific orientation relationships between either hexagonal-ZrO and monoclinic-ZrO2 or α-Zr and monoclinic-ZrO2 were identified, which suggests that the formation of often-reported bulk oxide texture during aqueous corrosion is not related directly to the texture of the metallic substrate. These results provide a guideline for understanding the mechanisms of crystallographic evolution during oxide growth on commercial zirconium alloys, and also demonstrate the capability of transmission Kikuchi diffraction to investigate orientation relationships in nano-scale materials.

Morphology and facet engineering have been proved efficient strategies to prepare high-performance photoelectrochemical (PEC) materials. WO3/BiVO4 heterojunction photoanodes with different morphologies were prepared by simply controlling the amount of electrodeposited charge. The coral-like WO3/BiVO4 photoanode with the orientation growth of {110} and {011} active facets of BiVO4 exhibited the optimal PEC performance due to significantly enhanced separation and transfer of photogenerated charge carriers, while the exposure of {−121} facets showed negative effects. 4.71 mA·cm−2 and 2.9 mA·cm−2 of photocurrent densities were obtained for sulfite and water oxidation, respectively, superior to most reported results. Subsequently, a photoelectrochemical-chlorine (PEC-Cl) system was constructed for antibiotic wastewater detoxification with hydrogen recovery. The analysis results indicated that the system can quickly and effectively remove sulfamethoxazole and reduce its toxicity concurrent with high hydrogen yield. The reactive chlorine species (RCS), especially Cl2·− and ClO·, dominated the sulfamethoxazole removal. Possible degradation pathways of sulfamethoxazole were also elucidated.

A novel S-scheme photocatalytic heterojunction composite nanomaterial is developed by integrating zero-dimensional WO3 quantum dots (WQDs) on two-dimensional ultrathin CdIn2S4 (CIS) nanosheets with the aim of fostering carrier separation, enhancing the performance of carrier interface transport, minimizing carrier distance transport, and achieving effective photocatalytic CO2 reduction. The composite photocatalyst WQDs/CdIn2S4 (WCIS) allows for the efficient photocatalytic reduction of CO2 to CO and CH4, as shown by product analysis and isotopic measurement. The photogenerated electrons in WQDs recombine with the holes in CIS nanosheets, and the left electrons in CIS have stronger CO2 reduction abilities. The highest yields of CO and CH4 achieved with the WCIS photocatalyst are 8.2 and 1.6 μmol g-1h−1 ––2.6 and 8 times higher than those for CIS, respectively. Moreover, the S-scheme WCIS possesses a stable crystal structure and recycling ability. Finally, the S-scheme charge transfer path on the WCIS composite is proposed according to theoretical calculation, in-situ irradiated X-ray photoelectron spectroscopy, and electron paramagnetic resonance (ESR) analyses.

In-situ electrocatalytic flue gas desulfurization (FGD) using a carbon black (CB)-based gas diffusion electrode (GDE) is efficient with no secondary pollution. However, higher desulfurization efficiency and energy conservation are demanded. In this work, CB-based GDEs were modified with poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate)-multi-walled carbon nanotubes (PEDOT: PSS-MWCNTs) for H2O2 production from two-electron oxygen reduction reaction (2e-ORR) during in-situ FGD. The results showed that the GDE modified with 100 mg 5% PEDOT: PSS-MWCNTs obtained the highest desulfurization efficiency (100.0%) and the lowest energy consumption (1.07 kW h kg−1), as 2e-ORR efficiency is improved from balancing ORR catalysis, pore structure, hydrophilicity, conductivity of the GDE, and the noncovalent interaction between MWCNTs and PEDOT: PSS. While excess PEDOT: PSS in the PEDOT: PSS-MWCNTs composite would cause reduced total pore area and porosity and excessive hydrophily which is harmful to O2 transfer for the GDE, hindering the 2e-ORR and desulfurization. This compact in-situ FGD system has advantages in desulfurization efficiency, energy consumption and durability, showing great potential in future industrial application.

Cr-coatings processed for different times were synthesized on the surface of AISI 5140 steel by double glow plasma surface alloying (DGPSA). The microstructures, microchemistry and phases of the coating were characterized by backscattering electron imaging (BSEI), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD). The results show that the Cr-coating prepared by DGPSA consists of three layers: a deposited-layer, a diffusion-layer and an affected-layer. With increasing DGPSA processing time, the relative thickness, microstructure and phase composition of the three layers vary greatly. The deposited-layer is mainly composed of pure-Cr, the diffusion-layer consists of Cr-Fe solid solution (Cr-Fe SS) and/or Cr-Fe intermetallic compound (Cr-Fe IMs), while the affected-layer is composed of high-Cr pearlite. After depositing Cr by DGPSA, the corrosion potential is improved and the corrosion current is reduced. Subsequent annealing not only promotes the precipitation of the multiple carbides particles within the pure-Cr coating, but also promotes the transformation of Cr-Fe IMs into Cr-Fe SS. However, these changes have little effect on the hardness and corrosion resistance of the coatings. Keywords: Double glow plasma surface alloying, Chromizing, Hardness, Corrosion resistance, Annealing

Coupled electrochemical system (CES) for electroreduction of CO2 and simultaneous degradation of organic pollutants is a promising CO2 conversion method. However, its performance is severely restrained by insufficient reactants and low electroactive surface areas on the cathode material. Here, a series of novel Sn-based carbon nanotubes (CNTs)/carbon black hybrid gas diffusion electrodes (CNTx/ESGDEs) were fabricated and used as cathodes to enhance the performance of the CES with methyl orange (MO) as a target pollutant. The results show that at an appropriate content of CNTs, the CNTx/ESGDEs offered increased total pore area, porosity, electroactive surface area, and decreased charge transfer resistances. The current density, Faraday efficiency, formic acid production rate, MO removal efficiency, and COD removal efficiency were improved by 140%, 92%, 404%, 76%, and 131%, respectively, at 40 wt% CNTs probably due to enhancement in the electroactive surface area as well as reactant transfer. This study benefits the large-scale applications of CES.

Converting austenite to martensite is a very effective and low-cost strategy for steel strengthening, but it results in a significant loss of ductility. In this study, we propose a novel method which simultaneously strengthens and toughens austenitic steels by introducing a gradient of martensite phase. We find that a gradient of deformation-induced martensite (α′-M) particles, with a volume fraction increasing from core to surface can be obtained in cylindrical AISI 304 stainless steel (304 SS) rods by applying free-end-torsion (FET). We compared the microstructures and tensile properties of gradient-structured 304 SS prepared by unidirectional-torsion (UT) and cyclic forward/reverse torsion (CFRT). It appears that piled-up dislocations formed near the core region during FET processing play a key role in the subsequent tensile deformation, and control the strain-hardening ability of the FET treated samples. The gradient α′-M enhances the strength of the surface layer and improves the tensile properties of the FET treated samples as a whole. Compared to UT, CFRT is more effective in inducing martensitic transformation, and enhances the gradient distribution of the α′-M. These findings provide a pathway for developing high strength and good ductility steels and other alloyed metals via gradient distributed second phase particles. Keywords: Gradient-structured metals, Gradient martensite, Torsion, Deformation-induced martensite, Mechanical properties

This article presents a novel quasi in-situ analysis, which allowed for examining the same microstructural area before and after irradiation, in two distinct facilities. One facility is used for the irradiation, and one for the energy dispersive X-ray spectroscopy (EDX) in a transmission electron microscope (TEM). The material studied is an austenitic oxide dispersion strengthened (ODS) stainless steel, modeled after commercial grade 310 L (25Cr 20Ni 2Mo-0.02C-0.4N-0.35Y2O3-0.5Ti-bal.Fe), which is synthesized from a powder metallurgy fabrication route using hot isostatic pressing. ODS materials are suitable for applications in: structural, highly corrosive, nuclear, and electromagnetic field environments. In fact, new generation fusion systems represent all four of these demands at the same time. The 310-ODS material is irradiated to ∼1.5dpa at 520OC with 1 MeV Kr2+ 7.5 × 1014 ions cm−2 (∼1.25 × 10−3 dpa/s). Quasi in-situ EDX line scans are presented, focusing on the interactions of: Fe, Cr, Ni, Y, Ti, and O. The examined particles are two Ti-rich structures, which present themselves as non-stoichiometric oxides (>200 nm) embedded within the iron matrix. The Y/Ti at% ratios in both observed particles decreased slightly from 0.34 ± 0.07 and 0.28 ± 0.04, to 0.26 ± 0.08 and 0.20 ± 0.06 respectively, suggesting a dissolution mechanism has initiated under this irradiation condition. It is often a question of dissolution vs. amorphization in these materials. Included is a detailed discussion of these two mechanisms as a function of temperature, fluence, and irradiating energy, with contrast to the current literature. Furthermore, attached is a data-in-brief (DiB), which includes the EDX spectrum and raw data captured from the experiment.

Electrochemical removal of nitrogen oxides (NOx) by solid electrolyte cells (SECs) is a promising technology due to no required reductant. Herein, a series of La0.8Sr0.2Mn1−xNixO3 (0 ≤ x ≤ 0.5) perovskites were first synthesized and utilized as the electrode materials of SECs. The role of Ni substitution in electrode performance and NOx reduction mechanism were revealed by various experimental characterization and first-principle calculations. The results indicate that the moderate Ni substitution (x ≤ 0.3) increased the NOx conversion of electrodes while reduced the polarization resistance. The further investigation shows that this improvement was attributed to the more surface oxygen vacancies, better reducibility and higher Mn4+ proportion of the Ni-substituted perovskites. The electrochemical impedance spectroscopy (EIS) shows that these changes facilitated the NOx adsorption and dissociation processes on the electrode. According to first-principle calculations, the Ni-substituted perovskite had a lower formation energy of surface oxygen vacancy, while the NO molecule adsorbed on defect surface gained more electrons thus was easier to be reduced and dissociated. Finally, the electrode performance at different operating temperatures and the operational stability were verified.

This study explored the depth treatment of desphenly chloridazon (DPC) wastewater by a novel synergetic dual-electrodes electrocatalytic (SDEs) system which consisted of Ni–Sb–SnO2/Ti anode (NSSTA) and PEDOT/PSS-CNTs modified activated carbon air diffusion cathode (PP-CNTs AC ADC). NSSTA exhibited an enhanced capability to produce reactive oxygen species (·OH and O3), its O3 production increased to 6.54 mg/L. PP-CNTs AC ADC was observed to have improved activity of catalyzing oxygen reduction reaction (ORR) with 648.23 mg/L H2O2 generated. Owing to the synergetic effect of O3 and H2O2, additional ·OH was obtained in SDEs system through the electro-peroxone reaction. Compared with the single-electrode electrocatalytic (SE) systems, the SDEs system showed superior pesticide degradation performance, higher mineralization current efficiency (MCE) and lower energy consumption (EC). In the SDEs system, the optimal 91.7% of DPC removal efficiency and 90.7% of DPC mineralization efficiency were obtained within 150 min by electrocatalytic oxidation of 17.5 ppm and 25 ppm pesticide wastewater at the current density of 11.94 mA/cm2, respectively. The treated water showed reduced acute toxicity than that of the raw wastewater, which suggested that the SDEs system is a promising technology for depth treatment of the pesticide industry effluent with simultaneous decontamination and detoxification realized.

In this study, induction heating chromizing (IHC) and box-type furnace heating chromizing (BFHC) were conducted on commercial AISI 5140 steels, respectively. Microstructure, microhardness and wear resistance of the chromized samples were characterized. The results show that the IHC samples have thicker Cr coating layer and stronger interface bond due to pre-compressive stress among the packed powders. Three kinds of microstructures including alloyed cementite (AC-layer), fine pearlite zone (FP-zone) and carbon-poor zone (CP-zone) are formed near the interface in the IHC samples. The main reason given for this is that different contents of Cr and C have different effects on pearlite phase and morphology. The IHC sample shows better wear properties due to its stronger interface bonding strength than that of the BFHC sample. The formation mechanism of CP-zone and its influences on microhardness and wear resistance are also discussed.

In this paper, a dual phase Zr-Sn-Nb-Mb alloy was studied with TEM after thermal treatment and high-temperature tensile deformation. Plate and pressure tube material, manufactured through different processing routes, were used in this study. The overall average concentrations of Mo and Nb in the β phase are higher in the pressure tube than in the plate. It was revealed that these concentrations have significant effects on the subsequent stability of the β and ω phases as well as on the precipitation behavior of the α phase from the β phase. That is, the higher the concentrations, the more stable the β and ω phases are, and hence there is a reduced tendency for precipitation of α phase. Aging treatments cause the transformation of athermal ω to isothermal ω, as expected. The most striking finding is the product of the decomposition of the isothermal ω particles during aging treatment is determined as not being α phase, even though the structure of it is, as-yet, not fully determined. The non-uniform morphology of the β grains in the plate material provides us a unique opportunity to investigate the effects of morphology on the aging response of the β phase. It was found that thin β filaments suppress the precipitation of isothermal ω particles but enhance the precipitation of α phase at α/β interfaces. The effect of the Burgers orientation relationship between α and β grains on the precipitation of the α phase at the α/β interface is discussed. Applied high-temperature stress/strain has been found to enhance the decomposition of isothermal ω phase but suppress α precipitation inside the β grains. The suppression of α precipitation by applied stress/strain is discussed in terms of the ω assisted α precipitation. Implications of these findings for the in-service application of the alloy are discussed.

The thermodynamically equilibrium precipitates that form in the Zr-Excel alloy after long-term (2500 h) annealing at 550 °C were investigated with transmission electron microscopy and X-ray diffraction techniques. The equilibrium precipitates were found to be a form of cubic Zr(Mo,Nb,Fe) 2 with about 26.5 at.% Mo substituted by Nb. Differential scanning calorimetry (DSC) heating curves show that the phase transformation sequence is αZr + Zr(Mo,Nb,Fe) 2 → αZr + Zr(Mo,Nb,Fe) 2 + βZr → αZr + βZr → βZr upon heating the long-term annealing alloy. With the heating rate of 10 °C/min, the αZr is found to transform into βZr at 530 °C, and Zr(Mo,Nb,Fe) 2 completely dissolves at a temperature higher than 771 °C, while the αZr disappears at 969 °C.

In this study, hot-extruded copper rods were subjected to free-end-torsion and subsequent annealing. The microstructures and mechanical properties of the deformed samples and annealed samples were investigated. The results show that torsion can introduce gradient lamellar dislocation substructures (LDS) into the copper rods, suggesting a gradient distribution of stored energy from core to surface. Different degrees of recrystallization were formed in the same torsional rod after recrystallization annealing due to such gradient stored energy. Annealing can change the microstructure inversely from deformed gradient into annealed gradient distribution via fully recrystallization in the surface layer and incomplete recrystallization in the middle layer. Therefore, gradient structured copper rods with soft core and hard shell or hard core and soft shell could be obtained by torsion or the combination of torsion and subsequent annealing, respectively. The tensile yield strength of such gradient structured rods has a linear relationship with the volume fraction of hard and soft regions no matter where the hard region is located, core or surface. The incomplete recrystallization mechanisms of gradient structured copper rods induced by torsion were also discussed.

This study reportsin situobservations of the formation of the δ′-ZrO phase, occurring during the annealing of transmission electron microscopy (TEM) thin foils of both pure Zr and a Zr–Sn–Nb–Mo alloy at 973 K in a transmission electron microsope. The lattice parameters of δ′-ZrO were measured and determined to be similar to those of the ω-Zr phase. The orientation relationship between the δ′-ZrO and α-Zr phases has been identified as either {(11 \overline{2}0)}_{\rm ZrO}//{(0002)}_{\alpha} and {[0002]}_{\rm ZrO}//{[11 \overline{2}0]}_{\alpha} or {(\overline{1}011)}_{\rm ZrO}//{(0002)}_{\alpha} and {[01{\overline 1}1]_{{\rm{ZrO}}}}//{[11{\overline 2}0]_\alpha} depending on the orientation of the α grain relative to the TEM thin-foil normal. The nucleation and growth of δ′-ZrO were dynamically observed. This study suggests a new and convenient way to study oxidation mechanisms in Zr alloys and provides a deeper understanding of the properties of the newly reported δ′-ZrO. Since δ′-ZrO has a Zr sublattice which is identical to that of ω-Zr, the orientation relationships between the α and δ′-ZrO phases may also shed light on the orientation relations existing between α- and ω-Zr, and hence α- and ω-Ti.

The thermodynamically equilibrium state was achieved in a Zr-Sn-Nb-Mo alloy by long-term annealing at an intermediate temperature. The fcc intermetallic Zr(Mo, Nb) 2 enriched with Fe was observed at the equilibrium state. In-situ 1 MeV Kr 2+ heavy ion irradiation was performed in a TEM to study the stability of the intermetallic particles under irradiation and the effects of the intermetallic particle on the evolution of type dislocation loops at different temperatures from 80 to 550 °C. Chemi-STEM elemental maps were made at the same particles before and after irradiation up to 10 dpa. It was found that no elemental redistribution occurs at 200 °C and below. Selective depletion of Fe was observed from some precipitates under irradiation at higher temperatures. No change in the morphology of particles and no evidence showing a crystalline to amorphous transformation were observed at all irradiation temperatures. The formation of type dislocation loops was observed under irradiation at 80 and 200 °C, but not at 450 and 550 °C. The loops were non-uniformly distributed; a localized high density of type dislocation loops were observed near the second phase particles; we suggest that loop nucleation is favored as a result of the stress induced by the particles, rather than by elemental redistribution. The stability of the second phase particles and the formation of the type loops under heavy ion irradiation are discussed.

Novel ternary nanocomposites with facet coupled structure were synthesized by using modified g-C 3 N 4 , TiO 2 nanosheets and nano-ZnO. Nanosheet/nanosheet heterojunction structure was investigated by TEM, XPS and XRD. FT–IR and Nitrogen adsorption were illustrated for chemical/physical structure analyses. Solution of p -Toluenesulfonic acid ( p -TSA) was chosen as target pollutant for visible light photodegradation and the excellent removal efficiency was achieved by this structurally modified g-C 3 N 4 /TiO 2 /ZnO hybrid. The visible light absorption improvement and quantum efficiency enhancement, which were testified by UV–vis DRS, PL and p -TSA photodegradation measurements, due to the facet coupled structure and appropriate quantity of modified g-C 3 N 4 in the nanocomposites.

Synchrotron X-ray diffraction, scanning electron microscopy, and transmission electron microscope bright field and high angle annular dark field were employed to investigate the microstructure and precipitates of a Zr-2.5Nb-0.5Cu alloy wire, with potential application as a spacer in the CANDU® reactor design. Results show that three types of microstructure co-exist in the alloy: Widmanstatten structure, α-Zr grains without precipitates and α-Zr grains with precipitates. In the meantime, three types of second phase particles are detected: β-Nb, Zr2Cu and Zr2Fe, which have different distributions within the microstructure. The β-Nb precipitates are observed to be extensively distributed among the α plate boundaries and twin interfaces in the Widmanstatten structure, whereas the Zr2Cu and Zr2Fe precipitates are only found in the α plate boundaries. The orientation relations of the Zr2Cu precipitates with respect to the α-Zr and β-Nb are found to be ( 013 ) Zr 2 Cu / / ( 0001 ) α ( 013 ) Zr 2 Cu / / ( 0001 ) α , [ 0 3 ¯ 1 ] Zr 2 Cu / / [ 1 ¯ 100 ] α and ( 013 ) Zr 2 Cu / / ( 011 ) β − Nb , [ 0 3 ¯ 1 ] Zr 2 Cu / / [ 2 ¯ 1 ¯ 1 ] β − Nb respectively.

With aim to develop an efficient heterogeneous metal-free cathodic electrochemical advance oxidation process (CEAOP) for persistent organic pollutants (POPs) removal from wastewater under mild conditions, electrochemically reduced graphene oxide (ERGO)-modified gas diffusion electrode (GDE) was prepared for oxygen-containing radicals production via electrochemical oxygen reduction reaction (ORR). A detailed physical characterization was carried out by SEM, Raman spectroscopy, XRD and XPS. The electrocatalytic behavior for ORR was investigated by electrochemical measurements and electrolysis experiments under constant current density. Bisphenol A (BPA) of 20 mg L −1 was used as a model of POPs to evaluate the performance of the CEAOP with ERGO-modified GDE. The results showed that the defects concentration and electrochemical active sites of the ERGO was increased as the reduction time (30 min, 60 min and 120 min), leading to different catalysis on ORR. O 2 generation via one-electron ORR was found under the electrocatalysis of ERGO (60 min and 120 min), contributing to a complete degradation of BPA within 20 min and a mineralization current efficiency (MCE) of 74.60%. An alternative metal-free CEAOP independent of Fenton reaction was established based on ERGO-modified GDE for POPs removal from wastewater under mild conditions.

Tungsten is the main candidate material for plasma-facing armour components in future fusion reactors. In service, bombardment with energetic neutrons will create collision cascades that leave behind lattice defects. Helium, injected from the plasma and produced by transmutation, strongly interacts with these defects, modifying their behaviour and retention. Helium-ion-implantation provides an effective tool for examining helium-defect interactions and their effect on the properties of tungsten armour. We use nano-indentation to probe the mechanical properties of the shallow helium-ion-implanted layer. Comparison of spherical indents in unimplanted and helium-implanted regions of the same single crystal shows a large increase in hardness and substantial pile-up in the implanted material. The complex lattice distortions beneath indents are probed non-destructively using 3D-resolved synchrotron X-ray micro-diffraction. Reduced lattice rotations and indentation-induced residual strains in the ion-implanted material indicate a more confined plastic zone. This is confirmed by HR-EBSD and TEM observations. Together our results suggest that dislocation motion is initially obstructed by helium-induced defects. The obstacle strength of these defects is reduced by the passage of dislocations, leading to a strain-softening and slip channel formation. A constitutive law for 3D crystal plasticity finite element simulations is developed based on this hypothesis. Simulations of the indentation process successfully capture the helium-implantation induced changes in deformation behaviour observed in experiments. Importantly, the effects we observe are markedly different from previous observations for self-ion-implanted tungsten, highlighting that the exact nature of the implantation damage plays a critical role in determining mechanical property change.

We observe large-scale surface terraces in tungsten oxidised at high temperature and in high vacuum. Their formation is highly dependent on crystal orientation, with only {111} grains showing prominent terraces. Terrace facets are aligned with {100} crystallographic planes, leading to an increase in total surface energy, making a diffusion-driven formation mechanism unlikely. Instead we hypothesize that preferential oxidation of {100} crystal planes controls terrace formation. Grain height profiles after oxidation and the morphology of samples heat treated with limited oxygen supply are consistent with this hypothesis. Our observations have important implications for the use of tungsten in extreme environments.

The Fe-3Ti-xB-4C (x = 1.71, 3.42, 5.10, 6.85 wt. %) hardfacing alloys are deposited on the surface of a low-carbon steel by plasma transferred arc (PTA) weld-surfacing process. Microstructure, hardness and wear resistance have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Rockwell hardness tester and abrasive wear testing machine, respectively. The results show that the microstructure in all alloys is composed of austenite, martensite, Fe23(C,B)6, Ti(C,B) and Fe2B. The volume fraction of eutectic borides and Ti(C,B) carbides increases with increasing B content. Many brittle bulk Fe2B phase arises when the boron content increases to 6.85%, which causes the formation of microcracks in the hardfacing layer. The microhardness of the hardfacing alloys is significantly improved with the B addition, however, the wear resistance of hardfacing alloys increases firstly and then decreases with increasing of B content. The hardfacing alloy with the 5.10% B content has the best wear resistance, which is attributed to high volume fraction of eutectic borides and fine Ti(C,B) particles distributed in the austenite and lath martensite matrix with high hardness and toughness. The formation of brittle bulk Fe2B particles in the hardfacing alloy with the 6.85% B leads to the fracture and spalling of hard phases during wear, thus, reducing the wear resistance.

A co-electrolysis system of CO2 and organic pollutants (CES) is promising for CO2 conversion and organic pollutant removal. However, it is still challenging to achieve the simultaneous efficient CO2 conversion and organic pollutant removal by tuning the electrode potential. Herein, we report a novel electrolysis mode for the CES. The anode potential was controlled by a potentiostat, while the cathode potential was controlled by changing the cathode surface area. By controlling the anode potential at 1.8 V and the cathode surface area at 0.1 cm2 (i.e., the anode/cathode surface area ratio was 10), both the anode and cathode potential values in the CES could be maintained to where CO2 reduction to formate and organic pollutant (p-nitrophenol in this study) removal were favored. The efficiencies for formate production and p-nitrophenol removal were almost the same as their optimal values in the individual electrochemical processes. Moreover, compared to the conventional electrolysis mode, our proposed electrolysis mode increased the current efficiency 1.25–1.41 times. Overall, this study clearly demonstrated that our proposed electrolysis mode is a feasible strategy to obtain simultaneous efficient formate production and organic pollutant removal in the CES, which can accelerate the use of the CES in industrial applications.

Sn-based gas diffusion electrodes (GDEs) are promising for electroreduction of CO2 to formate (ERCF) as they can alleviate CO2 mass transfer limitations. However, current electrodes suffer from large catalyst size or poor electron and/or ion connections. This limits ERCF performance. Here, we report a Sn-based GDE (IE-Sn) for ERCF fabricated via deposition of Sn nanoparticles onto a gas diffusion layer by using an impregnation-electroreduction method. The characterization results showed that the IE-Sn has small Sn catalyst size (16 nm) and excellent electronic and ionic transfer properties. Moreover, the faradaic efficiency (87.12 ± 4.28%) and partial current density for formate (62.79 ± 5.33 mA cm−2) obtained from the IE-Sn is 2.45-fold and 4.86-fold, respectively, of those of the traditional electrode. This ERCF performance is one of the best among recently reported Sn-based GDEs under similar conditions. Further analyses reveal that the enhanced ERCF performance of the IE-Sn is linked to the large electroactive surface area, enhanced adsorption capacity and chemisorption ability of CO2, better stabilization of CO2.– intermediate, and excellent ion/electron transfer. This study offers design rules to fabricate high-performance electrode materials for ERCF.

Predicting the dramatic changes in mechanical and physical properties caused by irradiation damage is key for the design of future nuclear fission and fusion reactors. Self-ion irradiation provides an attractive tool for mimicking the effects of neutron irradiation. However, the damaged layer of self-ion implanted samples is only a few microns thick, making it difficult to estimate macroscopic properties. Here we address this challenge using a combination of experimental and modelling techniques. We concentrate on self-ion-implanted tungsten, the frontrunner for fusion reactor armour components and a prototypical bcc material. To capture dose-dependent evolution of properties, we experimentally characterise samples with damage levels from 0.01 to 1 dpa. Spherical nano-indentation of grains shows hardness increasing up to a dose of 0.032 dpa, beyond which it saturates. Atomic force microscopy (AFM) measurements show pile-up increasing up to the same dose, beyond which large pile-up and slip-steps are seen. Based on these observations we develop a simple crystal plasticity finite element (CPFE) model for the irradiated material. It captures irradiation-induced hardening followed by strain-softening through the interaction of irradiation-induced-defects and gliding dislocations. The shear resistance of irradiation-induced-defects is physically-based, estimated from transmission electron microscopy (TEM) observations of similarly irradiated samples. Nano-indentation of pristine tungsten and implanted tungsten of doses 0.01, 0.1, 0.32 and 1 dpa is simulated. Only two model parameters are fitted to the experimental results of the 0.01 dpa sample and are kept unchanged for all other doses. The peak indentation load, indent surface profiles and damage saturation predicted by the CPFE model closely match our experimental observations. Predicted lattice distortions and dislocation distributions around indents agree well with corresponding measurements from high-resolution electron backscatter diffraction (HR-EBSD). Finally, the CPFE model is used to predict the macroscopic stress-strain response of similarly irradiated bulk tungsten material. This macroscopic information is the key input required for design of fusion armour components.

Neutron diffraction line profile analysis (DLPA) and transmission electron microscopy were used to characterize the components of the bimodal microstructure of Zr-Excel (Zr–3.5Sn–0.8Mo–0.8Nb), a nuclear structural material. The dual microstructure, consisting of equiaxed primary grains and martensitic domains both having hexagonal close-packed (h.c.p.) α crystal structure, forms when the as-received Zr-Excel alloy is heat treated at a high temperature and subsequently quenched,i.e. is solution treated. Because both microstructure components have the same crystal structure the reflections from the two components overlap significantly. The article presents how the multi-phase analysis capability of modern DLPA methods can be used to model the measured neutron diffraction patterns as the sum of two sub-patterns corresponding to the components of such a bimodal microstructure, which can be found in many hexagonal alloys relevant for industrial applications. The results show that the large equiaxed primary h.c.p. α grains have a highly correlated low-density dislocation structure and large sub-grains (∼300 nm), while the large martensitic domains have a randomly arranged very high density dislocation structure and sub-grains the size of ∼30 nm. The significantly different defect structures of the primary and martensitic phases manifest as large differences in the hardness and ductility of the individual components. As a result of this duality of the mechanical properties, solution-treated Zr-Excel materials can be considered as analogous to metal matrix composites where a softer ductile matrix contains a harder brittle reinforcing phase.

Zr-Excel alloy (Zr-3.5Sn-0.8Nb-0.8Mo, wt.%) has been proposed as a candidate material of pressure tubes in the CANDU-SCWR design. It is a dual-phase alloy containing primary hcp α-Zr and metastable bcc β-Zr. Metastable hexagonal ω-Zr phase could form in β-Zr as a result of aging during the processing of the tube. A synchrotron X-ray study was employed to study the lattice properties of the metastable phases in as-received Zr-Excel pressure tube material. In situ heavy ion (1 MeV Kr 2+ ) irradiations were carried out at 200 °C and 450 °C to emulate the stability of the metastable phase under a reactor environment. Quantitative Chemi-STEM EDS analysis was conducted on both un-irradiated and irradiated samples to investigate alloying element redistribution induced by heavy ion irradiation. It was found that no decomposition of β-Zr was observed under irradiation at both 200 °C and 450 °C. However, ω-Zr particles experienced shape changes and shrinkage associated with enrichment of Fe at the β/ω interface during 200 °C irradiation but not at 450 °C. There is a noticeable increase in the level of Fe in the α matrix after irradiation at both 200 °C and 450 °C. The concentrations of Nb, Mo and Fe are increased in the ω phase but decreased in the β phase at 200 °C. The stability of metastable phases under heavy ion irradiation associated with elemental redistribution is discussed.

The influences of pre-torsion deformation on microstructure and tensile strength of commercial as-extruded Cu rods with cylindrical shape have been investigated in this study by twisting the rods to different numbers of revolutions. The results indicated that the pre-torsion can significantly enhance the tensile yield strength of the as-extruded Cu rods without changing their shape and size. The increase in tensile yield strength is mainly due to the gradient lamellar dislocation substructures (LDS) embedded in elongated fiber grains introduced by pre-torsion pure shear deformation. Keywords: Copper, Torsion, Deformation properties, Gradient microstructure

A series of mesoporous Sn/Cr-MnOx nanomarerials with highly ordered three-dimensional channels were successfully prepared by the “nanocasting” method, which were used as selective catalytic reduction (SCR) catalysts to remove NOx with NH3 in a low-temperature range (150–300 °C). All of the mesoporous catalysts exhibited highly ordered mesoporous structure and high surface areas, and the SnOx nanoparticles were well dispersed in the mesoporous channels. Among all the Sn/Cr-MnOx samples, the 0.16-Sn/Cr (0.1)-MnO2 sample showed the best activity, giving the near 100% NOx conversion at 150–250 °C. From the XPS results, it can be found that doped Sn element significantly increased the proportion of Cr3+/Cr2+ and Mn3+/Mn4+ that may improve the N2 selectivity. Moreover, higher content of adsorbed oxygen and improved surface reducibility were also observed. In addition, Sn modified catalysts showed excellent SO2 resistance.

With a view to balancing light absorption and redox capabilities, narrowing band gap and adjusting bandgap structure, a novel tubular Bi12O17ClxBr2−x (BCxB2−x) solid solution structure was fabricated using a facile polyvinylpyrrolidone K30 assisted solvothermal strategy. Photocatalytic degradation experiments were conducted under visible light, utilizing tetrachlorobiphenyl A (TCBPA) as the target pollutant. Within 120 min of irradiation, the Bi12O17ClBr (BCB) solid solution nanotubes exhibited approximately 92.8 % TCBPA degradation efficiency. Moreover, the active radical trapping experiments and electron spin resonance measurements show that superoxide and hydroxyl radicals play important roles. Importantly, BCB solid solution photocatalysts have a stable crystal structure and good recycling ability after five cycles of photodegradation. The work presents a feasible synthesis method for the design of solid solution materials and introduction of oxygen vacancies to improve visible-light photocatalytic ability for the treatment of environmentally refractory organic pollutants.

Development of UV/H2O2 in practical application has been obviously constrained by inflexible H2O2 doping and less security and high cost from H2O2 transport and store. In-situ generating H2O2 via electrochemical oxygen reduction reaction (ORR), named electro-UV/H2O2 system, may provide an alternative way to enhance its efficiency and decrease its cost, especially for dealing with high-salinity organic wastewater. Electro-UV/H2O2 system was constructed with graphite-based air diffusion cathode (GADC) to enhance efficiency and economy of the traditional UV/H2O2 system. For creating extra benefit by the UV radiation, reduced graphene oxide (RGO) was attempted to modify the GADC via inner mixture (RGO@GADC-1) and further superficial deposition (RGO@GADC-2). One-step electrochemical reduction with anhydrous graphene oxide (GO) dispersion was developed for superficial modification of RGO with high-efficiency and good uniformity. The physical–chemical and electrochemical characterization showed little change of porous structure by RGO-doping and increased hydrophily and electrocatalytic activity by surface deposition of RGO. Average H2O2 production of 187.5 ~ 243.7 mg L-1h-1cm−2 were obtained, which were explained according to the potential energy barrier and desorption energy from DFT calculation. RGO@GADC-2 enhanced the TOC removal efficiency and mineralization current efficiency (MCE) of penicillin sodium (PGS) by 79.13% and 49.3% to 91.13% and 56.8%, respectively. The photocatalysis of RGO was confirmed to provide additional oxidative free radicals via reactions including donating UV-excited electrons for (i) one-electron ORR and (ii) H2O2 decomposition and (iii) UV-excited holes for water-splitting were evaluated.

Symmetric solid electrolyte cells with La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM)-Ce0.8Sm0.2O1.9 (SDC) composite electrodes are employed for nitric oxide (NO) removal. The LSCM powders are synthesized and the cells with LSCM-SDC composite electrodes are fabricated successfully. The results show that moderate SDC addition in LSCM electrode improves the cell performance due to the expansion of three phase boundaries (TPBs). The electrode with 30 wt% SDC has the highest NO conversion of 69.2% and the lowest polarization resistance at 750 °C in 1000 ppm NO. The cathodic polarization activates the cathode because of the Cr/Mn ions reduction, more surface oxygen vacancies and Cr metal exsolution. The cell has good tolerances for H2O, CO2, and SO2, but excess O2 competes with NO for TPBs seriously. The sufficient stability and flexible operation mode of the cell are also proved. Finally, the NO adsorption mechanism on LSCM surface is revealed by density functional theory (DFT) calculations.