Crystal Lattice Research Articles

Counter-Doping Effect by Trivalent Cations in tin-based Perovskite Solar Cells.

Sn-based perovskite solar cells normally show low open circuit voltage due to serious carrier recombination in the devices, which can be attributed to the oxidation and the resultant high p-type doping of the perovskite active layers. Considering the grand challenge to completely prohibit the oxidation of Sn-based perovskites, a feasible way to improve the device performance is to counter-dope the oxidized Sn-based perovskites by replacing Sn2+ with trivalent cations in the crystal lattice, which however has been rarely reported. Here, we present the introduction of Sb3+, which can effectively counter-dope the oxidized perovskite layer and improve the carrier lifetime. Meanwhile, Sb3+ can passivate deep-level defects and improve carrier mobility of the perovskite layer, which are all favourable for the photovoltaic performance of the devices. Consequently, the target devices yield a relative enhancement of the power conversion efficiency (PCE) of 31.4% as well as excellent shelf-storage stability. This work provides a novel strategy to improve the performance of Sn-based perovskite solar cells, which can be developed as a universal way to compensate for the oxidation of Sn-based perovskites in optoelectronic devices. This article is protected by copyright. All rights reserved.

Self-Trapped Exciton Emission in Highly Polar 0D Hybrid Ammonium/Hydronium-Based Perovskites Triggered by Antimony Doping.

Various monovalent cations are employed to construct metal halide perovskites with various structures and functionalities. However, perovskites based on highly polar A-site cations have seldom been reported. Here, a novel hybrid 0D (NH4)x(OH3)3-xInCl6 perovskite with highly polar hydronium OH3+ cations is introduced in this study. Upon doping with Sb3+, hybrid 0D (NH4)x(OH3)3-xInCl6 single crystals exhibited highly efficient broadband yellowish-green (550 nm) and red (630 nm) dual emissions with a PLQY of 86%. The dual emission arises due to Sb3+ occupying two sites within the crystal lattice that possess different polarization environments, leading to distinct Stokes shift energies. The study revealed that lattice polarity plays a significant role in the self-trapped exciton emission of Sb3+-doped perovskites, contributing up to 25% of the Stokes shift energy for hybrid 0D (NH4)x(OH3)3-xInCl6:Sb3+ as a secondary source, in addition to the Jahn-Teller deformation. These findings highlight the potential of Sb3+-doped perovskites for achieving tunable broadband emission and underscore the importance of lattice polarity in determining the emission properties of perovskite materials.

In situ/Operando Synchrotron Radiation Analytical Techniques for CO2/CO Reduction Reaction: From Atomic Scales to Mesoscales.

Electrocatalytic carbon dioxide/carbon monoxide reduction reaction (CO(2)RR) has emerged as a prospective and appealing strategy to realize carbon neutrality for manufacturing sustainable chemical products. Developing highly active electrocatalysts and stable devices has been demonstrated as effective approach to enhance the conversion efficiency of CO(2)RR. In order to rationally design electrocatalysts and devices, a comprehensive understanding of the intrinsic structure evolution within catalysts and micro-environment change around electrode interface, particularly under operation conditions, is indispensable. Synchrotron radiation has been recognized as a versatile characterization platform, garnering widespread attention owing to its high brightness, elevated flux, excellent directivity, strong polarization and exceptional stability. This review systematically introduces the applications of synchrotron radiation technologies classified by radiation sources with varying wavelengths in CO(2)RR. By virtue of in situ/operando synchrotron radiationanalytical techniques, we also summarize relevant dynamic evolution processes from electronic structure, atomic configuration, molecular adsorption, crystal lattice and devices, spanning scales from the angstrom to the micrometer. The merits and limitations of diverse synchrotron characterization techniques are summarized, and their applicable scenarios in CO(2)RR are further presented. On the basis of the state-of-the-art fourth-generation synchrotron facilities, a perspective for further deeper understanding of the CO(2)RR process using synchrotron radiation analytical techniques is proposed.

In situ/Operando Synchrotron Radiation Analytical Techniques for CO2/CO Reduction Reaction: From Atomic Scales to Mesoscales

AbstractElectrocatalytic carbon dioxide/carbon monoxide reduction reaction (CO(2)RR) has emerged as a prospective and appealing strategy to realize carbon neutrality for manufacturing sustainable chemical products. Developing highly active electrocatalysts and stable devices has been demonstrated as effective approach to enhance the conversion efficiency of CO(2)RR. In order to rationally design electrocatalysts and devices, a comprehensive understanding of the intrinsic structure evolution within catalysts and micro‐environment change around electrode interface, particularly under operation conditions, is indispensable. Synchrotron radiation has been recognized as a versatile characterization platform, garnering widespread attention owing to its high brightness, elevated flux, excellent directivity, strong polarization and exceptional stability. This review systematically introduces the applications of synchrotron radiation technologies classified by radiation sources with varying wavelengths in CO(2)RR. By virtue of in situ/operando synchrotron radiationanalytical techniques, we also summarize relevant dynamic evolution processes from electronic structure, atomic configuration, molecular adsorption, crystal lattice and devices, spanning scales from the angstrom to the micrometer. The merits and limitations of diverse synchrotron characterization techniques are summarized, and their applicable scenarios in CO(2)RR are further presented. On the basis of the state‐of‐the‐art fourth‐generation synchrotron facilities, a perspective for further deeper understanding of the CO(2)RR process using synchrotron radiation analytical techniques is proposed.

Factors responsible for Witwatersrand gold mineralisation

Abstract The exceptional gold mineralisation in quartz pebble conglomerates of the Witwatersrand Basin is attributed to a combination of factors. These factors are linked to the co-evolution of the atmosphere, hydrosphere, lithosphere and biosphere, at a very specific time in Archaean geological history and the evolution of the Kaapvaal Craton. Following craton stabilisation and its subaerial emergence, intense chemical weathering and erosion of large volumes of granitoid-greenstone basement released detrital and dissolved gold. Shallow-marine reworking in a long-lived and slowly subsiding basin subjected to episodic compressional deformation and relative sea-level oscillations led to sedimentary concentration of detrital gold. The interaction between acidic, anoxic, and sulfurous surface runoff and more oxidizing marine waters in a near-coastal oxygen oasis supported microbially mediated diagenetic pyrite formation and incorporation of dissolved gold in the pyrite crystal lattice. Erosion and reworking of diagenetic pyrite gave rise to detrital pyrite that characterise most reefs. Abundance of detrital uraninite in conglomerates, derived from erosion of Mesoarchaean granites, and episodes of hydrocarbon migration through sedimentary strata during deep burial set the scene for further enhancement of gold grades in the reefs. Granular and seam pyro-bitumen formed by radiation-induced polymerisation of hydrocarbons around detrital uraninite. Gold dissolved in migrating hydrothermal fluids was then reduced and precipitated upon interaction with the reef pyro-bitumen during hydrothermal placer modification.

Optimization of near-infrared luminescence performance in Cr3+-doped double perovskite Sr2ScTaO6 phosphor by Nb5+ ion substitution

Here, Nb5+ were partially substituted for Ta5+ in the double perovskite Sr2ScTaO6: Cr3+ phosphor to improve its luminescence performance and finally obtained the optimized phosphor Sr2ScTa0.6Nb0.4O6: Cr3+. The structure, substitution mechanism, luminescence optimization mechanism, crystal field, and thermal stability of the phosphor were all thoroughly explored. The results indicate that introducing Nb5+ into Sr2ScTaO6: Cr3+ can cause lattice distortion in the host, and the distorted crystal lattice can break the forbidden transition of Cr3+, thereby enhancing its absorption of excitation light. At the same time, the full width at half maximum of the phosphor emission increased from 176.4 nm to 179.7 nm. And the internal quantum efficiency, absorption efficiency, and external quantum efficiency of the optimized Sr2ScTa0.6Nb0.4O6: Cr3+ phosphor can reach 86.3%, 49% and 42.3%, respectively. The photoelectric conversion efficiency of the optimized pc-LED increased from 5.63% to 7.80%@100 mA, indicating the introduction of Nb5+ in Sr2ScTaO6: Cr3+ improved the luminescence performance of phosphor. The above results provide directions for the development of more efficient and promising double-perovskite NIR phosphors.

Gas Migration through the Crystal Lattice of Gas Hydrates during Sedimentation in Geological Time Scale

Gas Migration through the Crystal Lattice of Gas Hydrates during Sedimentation in Geological Time Scale

B-Factor Rescaling for Protein Crystal Structure Analyses

The B-factor, also known as the atomic displacement parameter, is a fundamental metric in crystallography for quantifying the positional flexibility of atoms within crystal lattices. In structural biology, various developments have expanded the use of B-factors beyond conventional crystallographic analysis, allowing for a deeper understanding of protein flexibility, enzyme manipulation, and an improved understanding of molecular dynamics. However, the interpretation of B-factors is complicated by their sensitivity to various experimental and computational factors, necessitating rigorous rescaling methods to ensure meaningful comparisons across different structures. This article provides an in-depth description of rescaling approaches used for B-factors. It includes an examination of several methods for managing conformational disorder and selecting the atom types required for the analysis.

Microstructural study on in-situ high-entropy (NbMoTaWV)C reinforced nanocrystalline NbMoTaWVC refractory high entropy alloys prepared by mechanically alloying

Refractory high-entropy alloys (RHEAs) can be commonly regarded as the best candidates for potentially substituting for the nickel-based superalloys practically used in the areas of aviation and nuclear industry, which can significantly endure in high-temperature and harsh environment. In this work, a nanocrystalline NbMoTaWVC RHEA is successfully produced by mechanical alloying method and X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and spherical aberration corrected transmission electron microscopy (AC-TEM) are employed to systematically characterized the microstructural details of NbMoTaWV and NbMoTaWVC RHEAs mechanically alloyed powders. Our results can support the evidence that the observable minimum nanoparticle sizes of the NbMoTaWV and NbMoTaWVC RHEAs considerably decrease to approximately ∼100 nm. Furthermore, the average grain sizes are gradually refined and thus notably drop to around of 30–50 nm, and five elemental powders can be found to be homogeneously alloyed. The evidence can be confirmed that the order of solid solution may be proposed as follows: Nb → Mo → V → Ta → W. The chemical short-range order occurred at the local nanoscale of NbMoTaWV and NbMoTaWVC RHEAs. Meanwhile, further microstrutural analysis can demonstrate that NbMoTaWV and NbMoTaWVC RHEAs powders with ultrafined grain have a bcc phase structure and bcc + bct matrix phases combined with high-entropy tungsten carbides (NbMoTaWV)C and (NbMoTaWV)2C of nano-precipitated phases, respectively, suggesting that the martensitic transformation probably occurred. The NbMoTaWV and NbMoTaWVC RHEAs powders of locally crystal lattice distortion rates reached approximately 8.07% and 6.33%.

THE ROLE OF ATOMIC SCATTERING FACTORS IN DETERMINING THE MINERAL COMPOSITION OF THE BAZHENOV SUITE'S ROCKS

For the first time, it was demonstrated, that the use of standard atomic-structural parameters of minerals in X-ray diffraction (XRD) analysis to determine the phase composition in the Bazhenov suite's core is incorrect and most often leads to inaccurate information when calculating their quantitative ratio. In particular, by decomposing the XRD — based quantitative data on the mineral composition of the core of the Bazhenov suite into the main rock-forming oxides and further comparing them with reliable X-ray fluorescence spectrometry (XRF) data, an unsatisfactory convergence between them was established. At the same time, significant differences in the results of XRD and XRF have been shown in terms of oxides of silicon, sodium, magnesium, potassium, and iron, both at large and small mass fractions. It has been found that even with perfect XRD, achieved by optimizing the standard mineral structure parameters (lattice period, crystallite size, crystal lattice microdistortion, absorption coefficient, crystallographic texture, background) and achieving a very high degree of convergence (more than 95%) of experimental and theoretical diffractograms, the differences between oxide forms are still significant. It is shown, that the results of XRD of Bazhenov suite are questioned due to detected inconsistencies in oxide forms. Using the analysis of multiple factors and data from diffractograms of many samples, it has been established that the identified differences are primarily caused by the use of incorrect initial atomic-structure parameters of minerals in modeling. It is shown that rock minerals in the Bazhenov suite are primarily characterized by significant changes in the values of atomic scattering factors and significant displacements of atomic positions in the nodes of the crystal lattice, caused by the action of the high pressures and temperatures in the formation. For the first time, the XRD algorithm that has been developed, is presented and implemented in Bazhenov suite rocks, with consideration of the state of atoms in the analyzed mineral. Furthermore, it was found that the authors XRD approach enables the identification and quantification of the Bazhenov suite minerals with a relatively low content, which are challenging to identify during traditional XRD.

[Ti{η5-1-(SiMe3)-3-(R)-C9H5}Cl2(OEt)] half-sandwich complexes: Synthesis, solid-state structure, hirshfeld surface analysis and theoretical studies

Indenyl-titanium trichloride complexes of type [Ti{η5-1-(SiMe3)-3-(R)-C9H5}Cl3] (R = SiMe3 (3a); R = tBu (3b)) were obtained by treatment of Li[1-(SiMe3)-3-(R)-C9H5] (R = SiMe3 (1a); R = tBu (1b)) with titanium tetrachloride (2) in a 1:1 molar ratio in the presence of isopropanol and SOCl2. Compounds [Ti{η5-1-(SiMe3)-3-(R)-C9H5}Cl2(OEt)] (R = SiMe3 (4a); R = tBu (4b)) are accessible by reacting 1a,b (R = SiMe3 (1a); R = tBu (1b)) with TiCl4 (2) in the presence of ethanol and SOCl2, or when 3a,b were treated with equimolar amounts of EtOH in refluxing benzene. Spectroscopic methods and single crystal X-ray diffraction analysis confirmed the piano-stool geometry of 3a and 4b in the solid state. Hirshfeld surface analysis using 2D fingerprint plots of 3a and 4b were conducted to elaborate non-covalent, intermolecular interactions existing in the solid state, which accounted for the strengthening of the crystal lattice. The molecular structures of the 3 and 4 were further investigated by quantum-chemical calculations. The geometries of the compounds were optimized at the B3LYP/6-31G(d)+LANL2DZ level of theory, and their related molecular parameters including frontier orbital energy gap and molecular electrostatic surface potential have also been calculated to better understand their properties.

Analysis of the Structure of Heavy Ion Irradiated LaFeO3 Using Grazing Angle X-ray Absorption Spectroscopy.

Crystalline ceramics are candidate materials for the immobilization of radionuclides, particularly transuranics (such as U, Pu, and Am), arising from the nuclear fuel cycle. Due to the α-decay of transuranics and the associated recoil of the parent nucleus, crystalline materials may eventually be rendered amorphous through changes to the crystal lattice caused by these recoil events. Previous work has shown irradiation of titanate-based ceramics to change the local cation environment significantly, particularly in the case of Ti which was shown to change from 6- to 5-fold coordination. Here, this work expands the Ti-based study to investigate the behavior in Fe-based materials, using LaFeO3 as an example material. Irradiation was simulated by heavy ion implantation of the bulk LaFeO3 ceramic, with the resulting amorphous layer characterized with grazing angle X-ray absorption spectroscopy (GA-XAS). Insights into the Fe speciation changes exhibited by the amorphized surface layer were provided through quantitative analysis, including pre-edge analysis, and modeling of the extended X-ray absorption fine structure (EXAFS), of the GA-XAS data.

Ingenious approach for retrieving valuable metals from gypsum via dehydration–rehydration two-step phase transition

Retrieving valuable metals (VMs) from industrial waste is an attractive approach to reduce the continuous consumption of metallic resources and prevent the environmental contamination by heavy metals. However, metal extraction efficiencies are extremely low due to their entrapment in crystal lattices. Herein, a universal strategy for extracting VMs from gypsum (CaSO4·2H2O), a common industrial waste, was reported using a two-step phase transition of dehydration–rehydration; metal extraction was achieved by designing an appropriate phase transition route and controlling the phase transformation kinetics. As the phase transition route to CaSO4·0.5H2O (path-0.5) proceeded faster than that to CaSO4 (path-0), higher extraction efficiencies were realized for Cr (99.9%) and Cd (98.8%) from gypsum. Mechanistic investigations indicated that during the selected path-0.5 dehydration, water molecule loss from gypsum initiated a direct solid-state transformation, triggering the first rearrangement of local atoms and excluding partially incorporated metals toward the edge of the CaSO4·0.5H2O lattice. The subsequent rehydration from CaSO4·0.5H2O to CaSO4·2H2O, with a phase transition rate faster than that of path-0, triggered the secondary atom rearrangement. The synergism between the two atomic rearrangements finally led to the complete release of trapped metals. Additionally, this strategy was used for retrieving other metals (e.g., Pb, Zn, Hg, As, and Sr) from gypsum, thereby potentially offering a new approach for designing an appropriate phase transition route for extracting VMs from other hydrous minerals.

Development of BaMnO3 nanoparticles embedded on rGO nanosheets via facile hydrothermal route to improve water oxidation

In light of environmental problems such as the depletion of hydrocarbon resources and global warming, the use of environment-friendly power production has become crucial nowadays. Hydrogen can serve as a globally friendly energy source because the byproduct of hydrogen combustion is only water. By a hydrothermal approach, we synthesized barium manganese oxide (BaMnO3) embedded on reduced graphene oxide (rGO) as a competent electrocatalyst for OER. We utilized X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive x-rays (EDX), Brunauer Emmette Teller (BET) and Raman to determine the crystal structure, morphology, elemental composition, surface area and lattice phenomena of the fabricated rGO/BaMnO3 nanocomposite. The BaMnO3 agglomerated nanoparticles were incorporated into the mesoporous hollow carbon nanosheets to form amorphous textured embedded rGO/BaMnO3. This enhanced the intrinsic reactivity of rGO/BaMnO3 nanocomposite for the oxygen evolution reaction (OER) in addition to increasing the effective surface area of the electrolyte. The electrochemical outcomes demonstrate that synthesized nanocomposite exhibited an impressive Tafel slope (36 mV dec−1), lowest overpotential (202 mV) and remarkable stability over 35 h. Therefore, the fabricated nanocomposite displayed exceptional efficiency in OER process as well as for numerous other future applications.

Effect of hetero-valence ions on structural and electrical properties of La2Ni(Mn0.5Ti0.5)O6 ceramics

The study of powder X-ray diffraction of La2Ni(Mn0.5Ti0.5)O6 (0.5LNMT) confirms a multi-phasic composition. The monoclinic P21/n phase content dominates. Occurrence of minor rhombohedral R3‾c phase and precipitates of MnO2 and La2MnO4 were detected. The morphology was analyzed using a SEM test and ceramics showed a porous structure and variation in the grain size below 4 μm. Dielectric permittivity of marked magnitude varies from ∼30 to ∼100 000 when temperature increases. Dielectric loss coefficient frequency dependence exhibits well-defined dielectric relaxation peaks, which were found to obey the Arrhenius law with the activation energy of 0.29 eV, below the presumed phase transition. Two sets of relaxation peaks in the imaginary part of electric modulus spectra relate to relaxations of different activation energies of 0.28 eV and 0.38 eV. An optical gap magnitude of 0.8 eV was determined from the diffuse reflectance spectrum in the Vis-NIR range. It compares with the band gap estimated from the X-ray photoelectron spectroscopy test. We also compare the influence of doping ions on the crystal lattice of the surface and the bulk ceramics. Electrical conductivity relaxation processes were attributed to the electron hopping mechanism between multi-valence Mnk+ and Nin+ ions’ states, which were determined from XPS analysis. The dc resistivity shows thermally generated dependence. Activation energy Edc magnitude varies between 0.27 and 0.37 eV which indicates the occurrence of defects and structural disorder. Such disorder correlates to the variable range hopping of small polarons involved in electrical conductivity. The density of states near Fermi energy was estimated N(EF) = 2.1 × 1025 eV−1 m−3. The 0.5LNMT application prospects were discussed.

Superior ionic conductivity of W-doped NASICON-type Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

NASICON-structured Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte has low grain boundary conductivity, which impedes its practical application. Herein, W was adopted to partially replace the Al element in LATP to improve its grain boundary conductivity. The W doping reduces the crystal lattice of the electrolyte, which is detrimental to the grain conductivity. But the doping of W can make the grains closely connect and reduce the voids between the grains, which can greatly enhance the grain boundary conductivity. The LATP sample with the W doping content of 0.03 (LATWP003) exhibits the highest total ionic conductivity of 1.186 mS/cm at 30 ℃, which results from the optimum grain boundary conductivity of 2.315 mS/cm. Moreover, the LATWP003 electrolyte displays a negligible electronic conductivity of 2.01×10−9 S/cm. The LiFePO4/LATWP003/Li battery with PVDF-HFP polymer protective layer can be charged and discharged. Therefore, the W doped LATP sample is a promising electrolyte for lithium-ion batteries.

Effects of doping with selected rare-earth elements (Eu3+, Dy3+, Eu3+/Dy3+) on the structural characteristics as well as electrical and luminescent properties of K0.5Na0.5NbO3.

The effects of adding Eu3+, Dy3+, and Eu3+/Dy3+ rare-earth elements on the microstructural, optical and electrical properties of lead-free piezoelectric materials based on K0.5Na0.5NbO3 (KNN) were investigated. A series of fine powders were synthesized via a modified Pechini route utilizing citric acid. Relatively large amounts of rare-earth elements were successfully incorporated into the crystal lattice of KNN. A combination of X-ray diffraction, X-ray absorption spectroscopy, energy-dispersive X-ray and scanning electron microscopy were used to characterize the structure and chemical composition of the powders and sinters. XRD patterns indicated the formation of a single-phase orthorhombic structure in the co-doped sinter. X-ray absorption spectroscopy revealed the nominal 3+ valence states of Eu and Dy in KNN ceramic sinters. The Mott model and group symmetry theory were used to discuss the characteristics of Raman spectra obtained for the EuDy:KNN ceramics. The ceramics exhibited good dielectric permittivity (ε≃1300) and low dielectric loss (tan δ=0.03) in the temperature range of 170-240°C. The electrical properties of the ceramics showed that the basic mechanism of conduction and relaxation was thermal activation, and that small polaron hopping was responsible for charge carrying. The Eu3+ and Dy3+ ions displayed characteristic red and orange emissions in sinters when excited with light in the wide ultraviolet spectra range (380-420nm).

A systematic investigation of solution and technological parameters for the fabrication and characterization of poly (vinyl alcohol–chitosan electrospun nanofibers

AbstractNanomaterials, particularly nanofibers are demonstrating exceptional potential for medical applications considered as promising systems for the integration of drug molecules, providing an enhancement of drug effectiveness and safety, while reducing drug side effects. Nanofibers based on two polymeric matrices poly(vinyl alcohol) (PVA) and chitosan (CS) have been demonstrated to be safe and promising materials for the drug integration and targeted drug delivery. This article studied the factors influencing on the fabrication and properties of PVA–CS nanofibers, including the impact of solution components on solution structure, rheological properties, electrospinning technology parameters, as well as the structure and thermomechanical properties of the obtained nanofibers have been investigated in details. The increasing of acetic acid concentration has the effect of pH lowering as well as electrical conductivity while heightening its viscosity. The pH, conductivity, and viscosity values of the solution rises as the CS concentration increases. Based on the Hildebrand‐Scatchard solubility theory, calculated Teas diagrams that account intermolecular interactions allow to predict low‐defect nanofibers based on PVA–CS in binary solvent systems with a greater concentration of hydrogen bonds. The optimal solution content and electrospinning parameters were determined. Infrared spectroscopy confirmed that the two polymer materials have a good interaction and the acetic acid was completely separated from the PVA–CS nanofibers. The XRD spectrum reveals that the crystal lattice parameters of the nanofibers change according to the polymer ratio. The polymers ratio also influence on the thermal and tensile properties. Such biosafe polymer materials may be considered as the promising drug delivery systems with the targeted mode of action.

Lattice strain engineered reactive oxygen species generation of NaNbO3 ferroelectric

The generation of reactive oxygen species (ROS) using ambient mechanical energy with piezoelectric materials is emerging as a promising method for producing renewable green oxidants. However, the low piezoelectricity and limited electron-hole pair separation efficiency significantly hinder its productivity. Here, non-stoichiometric Na1-xNbO3-δ perovskites with lattice strain and ferroelectric enhancement were successfully designed to boost the piezo-catalytic activity. Significantly, hydrogen peroxide (H2O2), superoxide radicals (•O2-), and hydroxyl radicals (•OH) were powerfully generated by the Na0.95NbO2.975 piezo-catalyst through redox reaction with rates of 362.4, 69.3, and 65.0 µmol∙g-1∙h-1, respectively, and the yield of H2O2 was approximately three times higher than that of the stoichiometric NaNbO3. The elevated piezoelectricity and polarization electric field effects induced by lattice strain could promote the generation of electron-hole pairs and drive them to separate facilely. The distribution of sodium vacancies and oxygen vacancies in the crystal lattice enhanced the diffusion of carriers for fast migration to the opposite surface of the catalyst. Furthermore, the presence of Na defects enhanced the adsorption of O2 on the Na1-xNbO3-δ surface and contributed to the catalytic generation of H2O2. This work provides a novel and effective methodology for the design of high-performance piezo-catalysts with lattice-strained engineering and broadens the strategy for improved H2O2 evolution efficiency.

Strategic Ni integration to study its impact on the photoluminescence and photocatalytic performances of SnO2 nanorod architecture

The sol-gel process was utilized to fabricate SnO2 nanoparticles, both in their pure form and with the addition of Ni dopants. The nanoparticles obtained were further examined to ascertain the characteristics associated with their structure, alterations in band gap, and photocatalytic performance. The insertion of nickel ions into tin sites hinders the formation of grain growth in tin oxide. The variation in the valence states and ionic radius of Sn4+ and Ni2+ ions, as revealed by X-ray diffraction (XRD) study, accounts for this disparity. FTIR measurements indicate the existence of stretching vibrations of metal-oxygen bonds that include Ni ions in the doped samples. The photoluminescence (PL) analysis reveals that the introduction of nickel doping alters the band structure of SnO2, leading to the creation of additional defect states, such as oxygen vacancies inside the crystal lattice. A study was undertaken to investigate the photocatalytic (PC) activity of SnO2 in the presence of Ni dopants. The results revealed a noticeable improvement in the efficiency of photodegradation. The degradation of Congo red (CR) dye using Ni-SnO2 nanocrystals achieves an efficiency of 94.88 % within a duration of 180 minutes. An analysis has been conducted on the impact of dye content, photocatalyst dosage, and pH on the degradation efficiency. As per the study, lower dose of Ni-SnO2 has shown better degradation efficiency in comparison to other studies. The improved performance of Ni-SnO2 can be ascribed to two main factors: the inhibition of carrier recombination due to the inclusion of defective states, and the production of hydroxyl radicals (OH•). The stability and reusability of these photocatalysts have been noted in their efficient application for environmental remediation.