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Entropy stabilized oxide of MgNiCoCuZnO5, also known as J14, is a material of active research interest due to a high degree of lattice distortion and tunability. Lattice distortion in J14 plays a crucial role in understanding the elastic constants and lattice thermal conductivity within the single-phase crystal. In this work, a neuroevolution machine learning potential (NEP) is developed for J14, and its accuracy has been compared to density functional theory calculations. The training errors for energy, force, and virial are 5.60 meV/atom, 97.90 meV/Å, and 45.67 meV/atom, respectively. Employing NEP potential, lattice distortion, and elastic constants is studied up to 900 K. In agreement with experimental findings, this study shows that the average lattice distortion of oxygen atoms is relatively higher than that of all transition metals in entropy-stabilized oxide. The observed distortion saturation in the J14 arises from the competing effects of minimum site distortion, which increases with increasing temperature due to enhanced thermal vibrations, and maximum site distortion, which decreases with increasing temperature. Furthermore, a series of molecular dynamics simulations up to 900 K are performed to study the stress–strain behavior. The elastic constants, bulk modulus, and ultimate tensile strength obtained from these simulations indicate a linear decrease in these properties with temperature, as J14 becomes softer owing to thermal effects. Finally, to gain some insight into thermal transport in these materials, with the so-developed NEP potential, and using non-equilibrium molecular dynamics simulations, we study the lattice thermal conductivity (κ) of the ternary compound MgNiO2 as a function of temperature. It is found that κ decreases from 4.25 W m − 1 K − 1 at room temperature to 3.5 W m − 1 K − 1 at 900 K. This suppression is attributed to the stronger scattering of low-frequency modes at higher temperatures. [ABSTRACT FROM AUTHOR]

Entropy stabilized oxide of MgNiCoCuZnO5, also known as J14, is a material of active research interest due to a high degree of lattice distortion and tunability. Lattice distortion in J14 plays a crucial role in understanding the elastic constants and lattice thermal conductivity within the single-phase crystal. In this work, a neuroevolution machine learning potential (NEP) is developed for J14, and its accuracy has been compared to density functional theory calculations. The training errors for energy, force, and virial are 5.60 meV/atom, 97.90 meV/Å, and 45.67 meV/atom, respectively. Employing NEP potential, lattice distortion, and elastic constants is studied up to 900 K. In agreement with experimental findings, this study shows that the average lattice distortion of oxygen atoms is relatively higher than that of all transition metals in entropy-stabilized oxide. The observed distortion saturation in the J14 arises from the competing effects of minimum site distortion, which increases with increasing temperature due to enhanced thermal vibrations, and maximum site distortion, which decreases with increasing temperature. Furthermore, a series of molecular dynamics simulations up to 900 K are performed to study the stress–strain behavior. The elastic constants, bulk modulus, and ultimate tensile strength obtained from these simulations indicate a linear decrease in these properties with temperature, as J14 becomes softer owing to thermal effects. Finally, to gain some insight into thermal transport in these materials, with the so-developed NEP potential, and using non-equilibrium molecular dynamics simulations, we study the lattice thermal conductivity (κ) of the ternary compound MgNiO2 as a function of temperature. It is found that κ decreases from 4.25 W m − 1 K − 1 at room temperature to 3.5 W m − 1 K − 1 at 900 K. This suppression is attributed to the stronger scattering of low-frequency modes at higher temperatures. [ABSTRACT FROM AUTHOR]

The dynamics of spin and charge-ordered phases in La1.67Sr0.33NiO4 single crystal have been investigated using high-frequency dielectric spectroscopy. The measurements were carried out in frequencies between 0.156 and 316 MHz and temperatures from 50 to 320 K. The intrinsic part of the response by excluding the Maxwell–Wagner relaxation region is obtained below TSDW ∼ 120 K. The intrinsic frequency-dependent real dielectric constant ɛ′ and conductivity σ′ can be well described in terms of the constant phase element revealing a complex charge-hopping process. Our results are in agreement with the spin-density-wave puddles' picture observed by the scanning micro-x-ray diffraction technique. These demonstrate that high-frequency dielectric spectroscopy can be utilized for investigating the various order phases in other transition metal oxides by considering their intrinsic responses. [ABSTRACT FROM AUTHOR]

Layered manganese transition metal oxides, such as NaMnO2, have attracted great interest due to the low cost and high capacity. However, complex phase transitions in NaMnO2 lead to poor cycling stability. The introduction of Li doping has been confirmed to improve the performance of NaMnO2. O3-type NaLi1/3Mn2/3O2 (NLMO), synthesized in 2021, has demonstrated excellent electrochemical performance. Notably, irreversible Li interlayer migration (Li migrates from the transition metal layer to the alkali metal layer) has been observed during cycling, which is related to the electrochemical performance. Therefore, it is crucial to understand the mechanism underlying Li interlayer migration in O3-NLMO. However, the environment of Li interlayer migration on cycling is complex and involves interlayer spacing, Na-ion concentration, the degree of O-ion oxidation, and phase transition. Here, in this work, we utilized the first-principles method to decouple the coupling factors influencing the Li interlayer migration. Through analyzing the impact of the single-factor on Li interlayer migration, we aim to identify the crucial factors affecting this process. Our results show that a decrease in Na-ion concentration and an increase in O-ion oxidation degree promote the Li interlayer migration, while the O–P phase transition suppresses the Li interlayer migration. Interlayer spacing was found to play a less influential role in Li interlayer migration. Our investigations provide effective strategies for the subsequent regulation of Li interlayer migration. [ABSTRACT FROM AUTHOR]

Modern electronic and optoelectronic devices rely on the development of the complementary pair of n-type and p-type semiconductors. However, it is often seen that n-type semiconductors are easier to realize and offer superior performances than their p-type counterparts, with p-type semiconductors showing much lower hole mobility and inefficient carrier doping. Here, by using first-principles studies, we demonstrate that lattice strain engineering can be a universal approach to enhance the hole mobility and dopability in p-type semiconductors. A broad class of p-type semiconductors, including anion p orbital derived valence band compounds (nitrides, oxides, halides, and chalcogenides), s orbital based post-transition metal oxides (e.g., SnO), and d-orbital based transition metal oxides (e.g., NiO), have been applied on strain to demonstrate their valence band modulation ability for the purpose of increasing the hole mobility and p-type dopability. We show that compressive lattice strain generally results in an upshifted valence band edge and reduced effective hole mass, leading to enhanced p-type dopability and increased hole mobility. Our work highlights strain engineering as a universal and effective approach for achieving better performed p-type compound semiconductors. [ABSTRACT FROM AUTHOR]

The prospect of creating ferroelectric or high permittivity nanomaterials provides motivation for investigating complex transition metal oxides of the form Ba(Ti, MV)O3, where M = Nb or Ta. Solid state processing typically produces mixtures of crystalline phases, rarely beyond minimally doped Nb/Ta. Using a modified sol-gel method, we prepared single phase nanocrystals of Ba(Ti, M)O3. Compositional and elemental analysis puts the empirical formulas close to BaTi0.5Nb0.5O3−δ and BaTi0.5Ta0.5O3−δ. For both materials, a reversible temperature dependent phase transition (non-centrosymmetric to symmetric) is observed in the Raman spectrum in the region 533–583 K (260–310 °C); for Ba(Ti, Nb)O3, the onset is at 543 K (270 °C); and for Ba(Ti, Ta)O3, the onset is at 533 K (260 °C), which are comparable with 390–393 K (117–120 °C) for bulk BaTiO3. The crystal structure was resolved by examination of the powder x-ray diffraction and atomic pair distribution function (PDF) analysis of synchrotron total scattering data. It was postulated whether the structure adopted at the nanoscale was single or double perovskite. Double perovskites (A2B′B″O6) are characterized by the type and extent of cation ordering, which gives rise to higher symmetry crystal structures. PDF analysis was used to examine all likely candidate structures and to look for evidence of higher symmetry. The feasible phase space that evolves includes the ordered double perovskite structure Ba2(Ti, MV)O6 (M = Nb, Ta) Fm-3m, a disordered cubic structure, as a suitable high temperature analog, Ba(Ti, MV)O3Pm-3m, and an orthorhombic Ba(Ti, MV)O3Amm2, a room temperature structure that presents an unusually high level of lattice displacement, possibly due to octahedral tilting, and indication of a highly polarized crystal. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is a two-dimensional, mechanically strong, and chemically tunable material for separations. Elucidating GO–ion–water interactions at the molecular scale is highly important for predictive understanding of separation systems. However, direct observations of the nanometer region by GO surfaces under operando conditions are not trivial. Therefore, thin films of GO at the air/water interface can be used as model systems. With this approach, we study the effects of alkali metal ions on water organization near graphene oxide films at the air/water interface using vibrational sum frequency generation (SFG) spectroscopy. We also use an arachidic acid Langmuir monolayer as a benchmark for a pure carboxylic acid surface. Theoretical modeling of the concentration-dependent sum frequency signal from graphene oxide and arachidic acid surfaces reveals that the adsorption of monovalent ions is mainly controlled by the carboxylic acid groups on graphene oxide. An in-depth analysis of sum frequency spectra reveals at least three distinct water populations with different hydrogen bonding strengths. The origin of each population can be identified from concentration dependent variations of their SFG signal. Interestingly, an interfacial water structure seemed mostly insensitive to the character of the alkali cation, in contrast to similar studies conducted at the silica/water interface. However, we observed an ion-specific effect with lithium, whose strong hydration prevented direct interactions with the graphene oxide film. [ABSTRACT FROM AUTHOR]

Photoredox properties of several earth-abundant light-harvesting transition metal complexes in combination with cobalt-based proton reduction catalysts have been investigated computationally to assess the fundamental viability of different photocatalytic systems of current experimental interest. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations using several GGA (BP86, BLYP), hybrid-GGA (B3LYP, B3LYP*), hybrid meta-GGA (M06, TPSSh), and range-separated hybrid (ωB97X, CAM-B3LYP) functionals were used to calculate relevant ground and excited state reduction potentials for photosensitizers, catalysts, and sacrificial electron donors. Linear energy correction factors for the DFT/TD-DFT results that provide the best agreement with available experimental reference results were determined in order to provide more accurate predictions. Among the selection of functionals, the B3LYP* and TPSSh sets of correction parameters were determined to give the best redox potentials and excited states energies, ΔEexc, with errors of ∼0.2 eV. Linear corrections for both reduction and oxidation processes significantly improve the predictions for all the redox pairs. In particular, for TPSSh and B3LYP*, the calculated errors decrease by more than 0.5 V against experimental values for catalyst reduction potentials, photosensitizer oxidation potentials, and electron donor oxidation potentials. Energy-corrected TPSSh results were finally used to predict the energetics of complete photocatalytic cycles for the light-driven activation of selected proton reduction cobalt catalysts. These predictions demonstrate the broader usefulness of the adopted approach to systematically predict full photocycle behavior for first-row transition metal photosensitizer–catalyst combinations more broadly. [ABSTRACT FROM AUTHOR]

The acidic (pKa ≈ 1.5 – 2.5) and hygroscopic nature of poly(3,4-ethylene dioxythiophene) polystyrene sulfonate, used as a common hole-injection layer in optoelectronic devices, has a detrimental effect on device stability and is associated with well established device failure mechanisms. In this work, a process with a high green index hole-injection layer material (V 2 O 5) and low surface roughness (RMS roughness ≈ 1.3 nm) was developed for demonstrating a hybrid polymer–inorganic perovskite light-emitting diode. Test devices with the new hole-injection layer demonstrate nearly identical maximum current efficiencies (4.23 vs 4.19 cd/A), and luminous efficacies (2.99 vs 2.32 lm/W) when compared to a control device fabricated with the conventional hole-injection layer. Furthermore, the peak brightness was achieved at a current density one-third of the value for the control device. To examine the transport of holes in the above hole-injection layer, we carried out device simulations based on a physical charge control model, including defect-assisted tunneling for hole injection. Close agreement for current–voltage characteristics is observed. Experimentally measured mobility in the device and measured radiative lifetimes were found to be sufficient to achieve this agreement without resorting to the introduction of a sheet charge at the injection interface. Despite the use of a bulk-heterojunction device architecture, the model predicts high radiative recombination rates [ ≈ 5.6 × 10 22 /(cm 3 s)] in the emissive layer, consistent with the measured photophysical properties for the active film, suggesting effective passivation of non-radiative surface states. [ABSTRACT FROM AUTHOR]

A guided ion beam tandem mass spectrometer was employed to study the reactions of U+ + CO2, UO+ + O2, and the reverse of the former, UO+ + CO. Reaction cross sections as a function of kinetic energy over about a three order of magnitude range were studied for all systems. The reaction of U+ + CO2 proceeds to form UO+ + CO with an efficiency of 118% ± 24% as well as generating UO2+ + C and UCO+ + O. The reaction of UO+ + O2 forms UO2+ in an exothermic, barrierless process and also results in the collision-induced dissociation of UO+ to yield U+. In the UO+ + CO reaction, the formation of UO2+ in an endothermic process is the dominant reaction, but minor products of UCO+ + O and U+ + (O + CO) are also observed. Analysis of the kinetic energy dependences observed provides the bond energies, D0(U+–O) = 7.98 ± 0.22 and 8.05 ± 0.14 eV, D0(U+–CO) = 0.73 ± 0.13 eV, and D0(OU+–O) = 7.56 ± 0.12 eV. The values obtained for D0(U+–O) and D0(OU+–O) agree well with the previously reported literature values. To our knowledge, this is the first experimental measurement of D0(U+–CO). An analysis of the oxide bond energies shows that participation of 5f orbitals leads to a substantial increase in the thermodynamic stability of UO2+ relative to ThO2+ and especially transition metal dioxide cations. [ABSTRACT FROM AUTHOR]

Antiferromagnetic spintronics is intrigued due to its unique properties that could break through the restrictions in ferromagnets. A 3d/5d transition metal oxide heterostructure is a good platform in antiferromagnetic spintronics research since the strong spin–orbit coupling in 5d oxides may bring about delicate interaction with the correlation energy and motivate unconventional phenomena. Here, the transport and magnetic characters of bilayers composed of antiferromagnetic 3d perovskite NdNiO3 and 5d perovskite SrIrO3 were investigated. The decreased metal–insulator transition and Néel temperature associated with suppressed negative magnetoresistance, emerged spin-glass like phenomenon, and the humped nonlinear Hall effect were observed in NdNiO3/SrIrO3 bilayers, which were absent in NdNiO3 and SrIrO3 pure films. It suggests the important role of interfacial interaction between NdNiO3 and SrIrO3 in modulating heterostructure transport and magnetic behavior and also manifests that complex magnetic structures might be realized in NdNiO3/SrIrO3 bilayers. [ABSTRACT FROM AUTHOR]

Transition metal oxides provide opportunities to induce and modulate the superconducting state, due to the delicate interplay between charge, spin, orbital, and lattice order. In this work, 5d transition metal oxide SrTaO3 films were deposited by pulsed laser deposition, and an anomalous negative resistance was observed. The negative resistance can be ascribed to the nonuniform conductivity, associated with nonuniform electronic states in the SrTaO3 thin films, as confirmed by conductive atomic force microscopy and x-ray photoelectron spectroscopy. Moreover, a sharp drop in the resistance together with a decrease in magnetization was observed at around 40 K. This might imply a possible superconducting state. The negative resistance can be well explained based on an equivalent circuit comprising normal and superconductive states, also supporting the possible superconducting state in SrTaO3 thin films. This work promotes the exploring and revealing of the mechanism in tantalates superconductivity. [ABSTRACT FROM AUTHOR]

Pseudopotential locality errors have hampered the applications of the diffusion Monte Carlo (DMC) method in materials containing transition metals, in particular oxides. We have developed locality error free effective core potentials, pseudo-Hamiltonians, for transition metals ranging from Cr to Zn. We have modified a procedure published by some of us in Bennett et al. [J. Chem. Theory Comput. 18, 828 (2022)]. We carefully optimized our pseudo-Hamiltonians and achieved transferability errors comparable to the best semilocal pseudopotentials used with DMC but without incurring in locality errors. Our pseudo-Hamiltonian set (named OPH23) bears the potential to significantly improve the accuracy of many-body-first-principles calculations in fundamental science research of complex materials involving transition metals. [ABSTRACT FROM AUTHOR]

A real-space method using generating integers is used to determine possible commensurate lattice Moiré patterns for a bilayer of two equal hexagonal lattices, which can in principle be extended to lattice mismatched bilayers. These Moiré patterns can be classified by a pair of relatively prime integers (n , m) , wherein a rotation θ (n , m) of the top hexagonal lattice maps its lattice vector (n , m) to (m , n) of the bottom lattice. Within this formulation, the area of the commensurate supercell is proportional to (n 2 + m 2 + n m) and the number of coincident lattice sites per supercell is given by (n − m) 2. Taking bilayer boron nitride (BN) as an example, we present how to systematically generate Moiré patterns and explore the differences in local chemistry in the interstitial region by impurity intercalation. Systematic calculations of the properties of intercalated 3d transition metals were performed in an h-BN (4 , 3) bilayer, corresponding to a rotation of 9.43 degrees. These calculations reveal that local symmetry in the intercalated region significantly affect the energetics and magnetization of the intercalated species. These results highlight that Moiré pattern physics is not limited to optoelectronic/electronic phenomena, such as interfacial exciton formation or magic angle superconductivity, but it also produces chemical and magnetic atomic site selectivity, which may play important roles in adsorption, catalysis, or quantum information. [ABSTRACT FROM AUTHOR]

Optoelectronic functional materials with flexible and in-plane anisotropic properties has been a significant development direction of nanotechnology due to wearable and polarized optoelectronic applications. Herein, the elasticity, global band dispersion, optical dielectric properties of environmentally friendly IVB-VIA layered transition metal trichalcogenides (MX3, M = Zr, Hf; X = S, Se) are investigated systematically by density functional theory with different kinds of van der Waals correction and hybrid functional. The low elastic modulus suggests that they are appropriate for the design of flexible optoelectronic devices. Originating from the effect of d states of chalcogens and s states of transition metals, the dispersion of the valence band edge of monolayer MX3 shows that the effective mass of carriers along the wave vector kx is much heavier than that of carriers along the wave vector ky. This means that the mobility of carriers exhibits obvious in-plane anisotropy. Meanwhile, the optical dielectric properties of monolayer MX3 as well as absorbed photon flux (Jabs) of the related heterostructures display noteworthy in-plane anisotropy in the visible-IR region. The ratio of Jabs from different direction reaches up to 1.7. This work could not only promote understanding of rich photophyiscal properties of transition metal trichalcogenides, but also provide a theoretical reference for the invention of high-performance optoelectronic devices with high flexibility and anisotropy. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) ultra-thin materials are more crucial than their bulk counterparts for the covalent functionalization of their surface owing to atomic thinness, large surface-to-volume ratio, and high reactivity of surface atoms having unoccupied orbitals. Since the surface of a 2D material is composed of atoms having unoccupied orbitals, covalent functionalization enables one to improve or precisely modify the properties of the ultra-thin materials. Chemical functionalization of 2D materials not only modifies their intrinsic properties but also makes them adapted for nanotechnology applications. Such engineered materials have been used in many different applications with their improved properties. In the present Perspective, we begin with a brief history of functionalization followed by the introduction of functionalized 2D materials. Our Perspective is composed of the following sections: the applications areas of 2D graphene and graphene oxide crystals, transition metal dichalcogenides, and in-plane anisotropic black phosphorus, all of which have been widely used in different nanotechnology applications. Finally, our Perspectives on the future directions of applications of functionalized 2D materials are given. The present Perspective sheds light on the current progress in nanotechnological applications of engineered 2D materials through surface functionalization. [ABSTRACT FROM AUTHOR]

Although two-dimensional (2D) transition metal oxide monolayers have shown potential for applications in metal-ion batteries, the heterostructures of this family are yet to be studied in details for energy storage applications. In this work, we have made the heterostructure by taking half-metallic ferromagnetic 2D transition metal oxide CoO 2 and semiconducting MnO 2 monolayers and demonstrated its potential application as a cathode material in lithium and sodium-ion batteries by performing first-principles calculations using density functional theory approach. We have systematically studied the electronic structure and stability of the MnO 2 / CoO 2 heterostructure. We have carefully examined the adsorption and diffusion behavior of metal ions (lithium and sodium). Our structure has offered a maximum adsorption energy of − 3.84 eV, which is greater than the adsorption energy of individual monolayers. We found that the lowest diffusion barrier is 0.4 eV for lithium ion and 0.32 eV for sodium ion. Also, our system has shown a maximum open circuit voltage of 2.18 V for lithium ion battery and 0.32 V for Na-ion battery. The specific capacity is found to be 584 mAh g − 1 for lithium ion and 529 mAh g − 1 for sodium ion battery. These findings can serve as a proof that the MnO 2 / CoO 2 heterostructure should be considered as a potential cathode for lithium- and sodium-ion batteries. [ABSTRACT FROM AUTHOR]

In this study, a novel aptasensor based on a transition metal oxide–modified pencil graphite electrode (PGE) was developed for the diagnosis of early-stage prostate cancer (PCa) via monitoring the prostate-specific antigen (PSA), which is the main biomarker for PCa. Single-use PGEs modified with pulsed deposited manganese oxide (MnOx) film were used to attach the amino-terminated aptamer specific to the PSA via carbodiimide chemistry. The designed aptasensor was placed in an electrochemical cell containing ferri/ferrocyanide ions as a redox probe to measure the charge transfer resistances (Rct) of the electrode surface by electrochemical impedance spectroscopy (EIS) to follow the response of each modification step. The effect of the medium pH on the ionic structure of the aptamer molecule according to its pI value and, thus, the reversing of the direction of the response (ΔRct) by the pH change was also discussed. The level of PSA secreted from PCa cells was investigated using impedimetric transduction. The specificity of the aptasensor was validated through selectivity studies against non-specific tumor markers like VEGF and different cancer cell lines including breast cancer and androgen-insensitive prostate cancer. The developed system showcases a label-free, fast, specific, and cost-effective approach for PSA detection, highlighting the importance of medium pH and the electrostatic environment on the aptamer's response. Our work emphasizes the potential for such aptasensors in clinical diagnostics and paves the way for further exploration into using transition metal oxides in biosensing applications. [ABSTRACT FROM AUTHOR]

Transition metal sulphides and oxides have been identified as potential cathode materials for lithium-ion batteries with high initial capacity and high selectivity. Nevertheless, the low ground conductivity and volume expansion have constituted significant obstacles to the advancement of this field of study. In this study, the heterostructure CoMn₂O₄/MnS₂@C1-2-2 of MnS₂ and CoMn₂O₄ was obtained through high-temperature (Ar. 450 °C) calcination of a novel red single crystal [CoMn(TDC)] n precursor. The resulting structure exhibited excellent lithium-ion transport properties. The biphasic heterostructure with a porous carbon framework is capable of forming a multitude of phase interfaces and conductive pathways, which facilitate charge migration, enhance conductivity, and expand the contact area with the electrolyte, thereby augmenting the charge transfer capability. The CoMn 2 O 4 MnS 2 @C1-2-2 composite displays remarkable lithium storage capabilities, with a specific capacity of 689 mA h g−1 even after 400 cycles at 0.5 A g−1. The heterostructure CoMn₂O₄MnS₂@C1-2-2, comprising a transition metal sulfide (MnS₂) and oxide (CoMn₂O₄), has been constructed by employing a novel type of MOF monocrystal {CoMn(TDC)}n as a precursor. The incorporation of surfactants and the heterogeneous structure of the modifiers with metal-ligand ratios has been demonstrated to enhance the transport performance of lithium ions as anodes for lithium-ion batteries. [Display omitted] • Rhombic red novel bimetallic CoMn-MOF single crystals was synthesized by hydrothermal method. • Derivatives of CoMn-MOF single crystals were used as anode materials with excellent performance for LIBs. • Heterogeneous interface between MnS 2 and CoMn 2 O 4 were constructed to boost rapid lithium ions transport. [ABSTRACT FROM AUTHOR]

In order to develop advanced energy storage devices, it is necessary to manufacture supercapacitor electrode that have both long electrochemical cycle lifetimes and high energy densities. These properties can only be obtained by developing heterostructure pseudo-capacitive materials. The combination of MnO 2 nanorods and ZnCr 2 O 4 nanoparticles resulted in a synergistic effect, which increased the electroactive surface area for charge storage. This effect was not observed when each component utilized individually. The material ZnCr 2 O 4 nanoparticles facilitated the MnO 2 nanorods. In present study, ZnCr 2 O 4 , MnO 2 and their composite was fabricated by simple sonication process. These fabricated samples were tested by using different techniques which includes X-ray diffraction (XRD), Raman analysis, Brunauer Emmett Teller (BET) and scanning electron microscopy (SEM). Electrochemical analysis of fabricated materials exhibited an exceptional specific capacitance (C sp = 1175.35 F g−1), energy density (E d = 15.95 Wh Kg−1) and power density (P d = 869.4 W kg−1). These materials are anticipated to act as the support for electrochemical energy storage devices that utilize an ideal electrode structure, meticulously select the appropriate transition metal oxide (TMO) and analyse electrochemical characteristics for supercapacitive performance. This study exhibits the remarkable efficiency of the nanostructured ZnCr 2 O 4 /MnO 2 electrode in supercapacitors with high energy density (E d). [ABSTRACT FROM AUTHOR]

Graphene has emerged as one of the most promising materials for next‐generation gas sensor platforms due to its high flexibility, transparency, and hydrophobicity. However, graphene shows inherent low selectivity in gas sensing. This has led to extensive development of noble‐metal decoration on graphene to modulate its surface chemistry for enhanced selectivity. While noble metals such as Pt, Pd, and Au have widely been employed to functionalize graphene surface, non‐noble metal decoration of graphene has remained underexplored. Here, an unprecedented room‐temperature self‐activated graphene gas sensor functionalized by NiO nanoparticles and its application to wearable devices monitoring ammonia gas in daily life are demonstrated. NiO‐functionalized graphene micropatterns show ultra‐high selectivity to ammonia with a low detection limit of 2.547 ppt. Density functional theory (DFT) calculations reveal that the strong attraction between NiO and NH3 induced by charge depletion and the vertex region of NiO accelerate the adsorption of NH3 molecules. Furthermore, a wearable graphene device demonstrates the capability to detect ammonia emissions from beef, triggering an alarm call when a specific threshold is exceeded. This work proposes the functionalization of graphene with transition metal oxides, extending beyond the conventional noble metal decoration, and the potential utilization of the graphene for wearable devices. [ABSTRACT FROM AUTHOR]

P2‐type layered transition metal oxides are potential cathodes for sodium‐ion batteries (SIBs), but they commonly suffer from severe capacity degradation owing to multiple phase transitions and Na+/vacancy ordering during the extraction/insertion process. An anionic/cationic co‐doping strategy at high sodium contents is proposed to effectively achieve high‐rate and long‐term stability of P2‐Na0.67Ni0.33Mn0.67O2. The resulting Na0.75Mg0.1Ni0.23Mn0.67O1.95F0.05 (NMNMOF) cathode delivers a reversible capacity of 116 mAh g−1 at 75 mA g−1 and maintains an initial capacity of 73% at 1500 mA g−1 after 1000 cycles. The Mg/F anionic/cationic co‐doping strategy impacts the local environment of the surrounding transition metal and oxygen, regulates the electron distribution, and modifies the initial diffusion state of Na sites, enhancing the diffusion ability of Na+. Moreover, the phase transition of P2‐O2 is well suppressed and the decrease in Mn3+ content greatly alleviates the Jahn–Teller effect to enhance structural stability. The full‐cell devices with NMNMOF cathode and hard carbon anode demonstrate a high capacity of 80 mAh g−1 at 10 C and an excellent cycle life of over 500 cycles for applications. The anionic/cationic co‐doping strategy will inspire the rational design of P2‐type layered oxides and provide a new perspective for advanced SIBs. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs) are recognized as high‐efficiency electrocatalyst systems for restraining the shuttle effect in lithium‐sulfur (Li−S) batteries, owing to their robust adsorption capabilities for polysulfides. However, the sluggish catalytic conversion of Li2S redox and severe passivation effect of TMOs exacerbate polysulfide shuttling and reduce the cyclability of Li−S batteries, which significantly hinders the development of TMOs electrocatalysts. Here, through the anion‐cation doping approach, dual incorporation of phosphorus and molybdenum into MnO2 (P,Mo‐MnO2) was engineered, demonstrating effective mitigation of the passivation effect and allowing for the simultaneous immobilization of polysulfides and rapid redox kinetics of Li2S. Both experimental and theoretical investigations reveal the pivotal role of dopants in fine‐tuning the d‐band center and optimizing the electronic structure of MnO2. Furthermore, this well‐designed configuration processes catalytic selectivity. Specifically, P‐doping expedites rapid Li2S nucleation kinetics by minimizing reaction‐free energy, while Mo‐doping facilitates robust Li2S dissolution kinetics by mitigating decomposition barriers. This dual‐doping approach equips P,Mo‐MnO2 with robust bi‐directional catalytic activity, effectively overcoming passivation effect and suppressing the notorious shuttle effect. Consequently, Li−S batteries incorporating P,Mo‐MnO2‐based separators demonstrate favorable performance than pristine TMOs. This design offers rational viewpoint for the development of catalytic materials with superior bi‐directional sulfur electrocatalytic in Li−S batteries. [ABSTRACT FROM AUTHOR]

Layered transition metal oxide (LTMO) cathode materials of sodium‐ion batteries (SIBs) have shown great potential in large‐scale energy storage applications owing to their distinctive periodic layered structure and 2D ion diffusion channels. However, several challenges have hindered their widespread application, including phase transition complexities, interface instability, and susceptibility to air exposure. Fortunately, an impactful solution has emerged in the form of a high‐entropy doping strategy employed in energy storage research. Through the implementation of high‐entropy doping, LTMOs can overcome the aforementioned limitations, thereby elevating LTMO materials to a highly competitive and attractive option for next‐generation cathodes of SIBs. Thus, a comprehensive overview of the origins, definition, and characteristics of high‐entropy doping is provided. Additionally, the challenges associated with LTMOs in SIBs are explored, and discussed various modification methods to address these challenges. This review places significant emphasis on conducting a thorough analysis of the research advancements about high‐entropy LTMOs utilized in SIBs. Furthermore, a meticulous assessment of the future development trajectory is undertaken, heralding valuable research insights for the design and synthesis of advanced energy storage materials. [ABSTRACT FROM AUTHOR]

Partial replacement of one structural element in a solid with another of a similar size was conducted to impart functionality to the solids and modify their properties. This phenomenon is found in nature in coloured gemstones and clay minerals and is used in materials chemistry and physics, endowing materials with useful properties that can be controlled by incorporated heteroelements and their amounts. Depending on the area of research (or expected functions), the replacement is referred to as "isomorphous substitution", "doping", etc. Herein, elemental replacement in two-dimensional (2D) oxides and hydroxides (nanosheets or layered materials) is summarised with emphasis on the uniqueness of their preparation, characterisation and application compared with those of the corresponding bulk materials. Among the 2D materials (graphene, metallenes, transition metal chalcogenides, metal phosphate/phosphonates, MXenes, etc.), 2D oxides and hydroxides are characterised by their presence in nature, facile synthesis and storage under ambient conditions, and possible structural variation from atomic-level nanosheets to thicker nanosheets composed of multilayered structures. The heteroelements to be doped were selected depending on the target application objectively; however, there are structural and synthetic limitations in the doping of heteroelements. In the case of layered double hydroxides (single layer) and layered alkali silicates (from single layer to multiple layers), including layered clay minerals (2 : 1 layer), the replacement (commonly called isomorphous substitution) is discussed to understand/design characteristics such as catalytic, adsorptive (including ion exchange), and swelling properties. Due to the variation in their main components, the design of layered transition metal oxide/hydroxide materials via isomorphous substitution is more versatile; in this case, tuning their band structure, doping both holes and electrons, and creating impurity levels are examined by the elemental replacement of the main components. As typical examples, material design for the photocatalytic function of an ion-exchangeable layered titanate (lepidocrocite-type titanate) and a perovskite niobate (KCa2Nb3O10) is discussed, where elemental replacement is effective in designing their multiple functions. [ABSTRACT FROM AUTHOR]

NiFe2O4, as an anode material for lithium-ion batteries, has attracted extensive attention due to its high theoretical capacity. However, its practical application is greatly restricted due to the serious volume expansion that occurs during electrochemical reactions. A novel NiO@NiFe2O4/reduced graphene oxide (rGO) architecture was self-assembled by using a facile hydrothermal method and annealing treatment, and its electrochemical lithium-ion storage performance was studied. The results indicate that the NiO@NiFe2O4/rGO electrode exhibits superior rate capability and cycling performance, with a high specific capacity of 930.12 mA h g−1 at 0.1 A g−1 after 100 cycles and 663.72 mA h g−1 at 0.5 A g−1 after 300 cycles. In addition, it still delivers large specific capacities of 342.6 and 213.55 mA h g−1 after 1000 cycles with a coulombic efficiency of more than 99% at high current densities of 2 and 5 A g−1, respectively. This distinguished electrochemical performance is ascribed to the unique and stable structure of the self-assembled NiO@NiFe2O4/rGO electrode material and the synergistic effect between NiO, NiFe2O4 and rGO. This work provides the possibility of improving the lithium-ion storage capacity of transition metal oxides by the facile self-assembly construction of an electrode material architecture. [ABSTRACT FROM AUTHOR]

The sluggish reaction kinetics of the anodic oxygen evolution reaction (OER) and the inadequate catalytic performance of non‐noble metal‐based electrocatalysts represent substantial barriers to the development of anion exchange membrane water electrolyzer (AEMWE). This study performed the synthesis of a three‐dimensional (3D) nanoflower‐like electrocatalyst (CFMO) via a simple one‐step method. The substitution of Co with Fe in the structure induces a localized oxide path mechanism (LOPM), facilitating direct O−O radical coupling for enhanced O2 evolution. The optimized CFMO‐2 electrocatalyst demonstrates superior OER performance, achieving an overpotential of 217 mV at 10 mA cm−2, alongside exceptional long‐term stability with minimal degradation after 1000 h of operation in 1.0 M KOH. These properties surpass most of conventional noble metal‐based electrocatalysts. Furthermore, the assembled AEMWE system, utilizing CFMO‐2, operates with a cell voltage of 1.65 V to deliver 1.0 A cm−2. In situ characterizations reveal that, in addition to the traditional adsorbate evolution mechanism (AEM) at isolated Co sites, a new LOPM occurred around the Fe and Co bimetallic sites. First‐principles calculations confirm the LOPM greatly reduced the energy barriers. This work highlights the potential of LOPM for improving the design of non‐noble metal‐based electrocatalysts and the development of AEMWE. [ABSTRACT FROM AUTHOR]

The development of lithium–metal batteries (LMBs) has emerged as a mainstream approach for achieving high‐energy‐density energy storage devices. The stability of electrochemical interfaces plays an essential role in realizing stable and long‐life LMBs. Despite extensive and comprehensive research on the lithium anode interface, there is limited focus on the cathode interface, particularly regarding high‐voltage transition metal oxide cathode materials. In this review, the challenges associated with developing stable high‐voltage cathode materials are first discussed. Characterization techniques for understanding the composition and structure of the cathode–electrolyte interphase (CEI) are then introduced. Subsequently, recent developments in electrolyte design and interface modification for constructing a stable CEI are summarized. Finally, perspectives on future research trends for understanding and developing the high‐voltage CEI are discussed. This review can offer valuable guidance for understanding and designing the high‐voltage CEI, pushing forward the development of high‐energy‐density LMBs. [ABSTRACT FROM AUTHOR]

Rechargeable sodium‐ion batteries are promising sustainable energy storage systems, owing to their low cost and high energy density. However, the existing cathode chemistries, particularly layered sodium transition metal oxides, exhibit restricted electrochemical performance, which hinders their extensive applications. To overcome challenges, originating from kinetically limited structural transformations, various cation substitutions are reported in the literature. Especially the partial Na–K replacement is discussed recently, which can increase bulk Na‐diffusivity and suppress undesirable phase transitions. Here, a critical study of potassium doping in different layered materials P3‐K0.5Co0.33Mn0.67O2 and P3‐K0.5Co0.33Mn0.67O2*0.5H2O with redox‐active Co (and Mn), and P2‐Na0.7Co0.8Ti0.2O2 and P2‐K0.1Na0.7Co0.8Ti0.2O2 with Co activity is presented. It is found that the presence of K significantly enhances the moisture sensitivity: P3‐K0.5Co0.33Mn0.67O2*0.5H2O is quickly formed in the air from K0.5Co0.33Mn0.67O2, while Na0.7Co0.8Ti0.2O2 remains stable under the same conditions. In electrochemical Na‐cells, a partial K–Na cation exchange in P3‐K0.5Co0.33Mn0.67O2 and P3‐K0.5Co0.33Mn0.67O2*0.5H2O occurs without applying current. The electrochemical performance of P3‐K0.5Co0.33Mn0.67O2 is slightly increased in comparison to K‐free P2‐Na0.67Co0.33MnO.67O2 from the literature, staying, however, behind the performance of Na0.7Co0.8Ti0.2O2. K0.1Na0.7Co0.8Ti0.2O2 shows weaker rate capability than isostructural Na0.7Co0.8Ti0.2O2, reflecting a negative impact of K on Na‐diffusivity. Therefore, effect of K‐incorporation in layered structures on the battery performance strongly depends on the cathode composition. [ABSTRACT FROM AUTHOR]

Biomass derived carbon is considered as a promising carbon because it contains abundant channel and pore structure and is not easy to degrade. Double transition metal oxides show abundant valence states, good biocompatibility, conductivity, high stability and satisfactory catalytic properties. In addition, a large number of waste biomass such as the fruit peel could cause the waste of resources and environmental pollution. Therefore, we used waste grape skins as a carbon source for assembly with double transition metal oxides. After calcination at high temperature, N-doped biomass-derived carbon loaded with double transition metal oxide composite was formed. The waste grape skins carbon substrate with large pores and large specific surface area provides more channels for ion migration and electron transport, promotes charge transfer, and further improves the ability to reduce NB. The material shows excellent electro-catalytic activity for nitrobenzene (NB), the limit of detection (LOD) is as low as 0.143 μM, the linear response range is wide (0.47–1798.71 μM), the sensitivity is high, the reproducibility, the selectivity and the stability are good. In addition, the sensing assembled from this material has achieved a recovery rate of 97–102.6 % in testing the NB content in actual water sample. This work provides a new idea for the detection of NB, and also finds a greener and more meaningful treatment method for waste biomass. [ABSTRACT FROM AUTHOR]

This work comprises a generalization of a simple geometric model originally developed to describe coupled rotations of corner-sharing octahedra in the surface layer of S r 2 RuO4 under uniaxial compression. The main objective of the model is to establish a link between the experimental global strain configuration and the possible microscopic mechanisms and compatible geometries by which the octahedra accommodate the applied strain. In achieving this, a useful and intuitive parametrization of four-site two-dimensional systems of corner-sharing octahedra has been established, which can be readily extended to three dimensions and N > 4 inequivalent sites or directly employed to analyze the octahedral configuration of many perovskites, transition metal oxides (TMOs), and layered compounds. [ABSTRACT FROM AUTHOR]

The development of flexible electronics technology has led to the creation of flexible energy storage devices (FESDs). In recent years, flexible self‐supporting cathodes have gained significant attention due to their high energy density, excellent mechanical performance, and strong structural plasticity among various cathode materials. Flexible self‐supporting cathodes enable larger active material loading capacity and conductive networks for electrodes, thereby perfectly meeting the mechanical and electrochemical performance requirements of FESDs. Currently, the focus of flexible self‐supporting cathodes lies in exploring flexible substrates or novel binders to enhance the flexibility of conventional cathode materials. However, the flexibility of cathode poses challenges as they are primarily composed of transition metal oxides, resulting in limited research on their flexibility. A comprehensive review and prospective analysis are of utmost importance to effectively advance the progress of flexible self‐supporting cathodes and propel their development forward. Herein, the present discourse delves into the latest advancements concerning flexible self‐supporting cathode, focusing on synthesis methodologies, structural design approaches, and characterization parameters. Examining the current progress, the inherent advantages, existing challenges, and potential prospects of these materials are comprehensively elucidated and emphasized. [ABSTRACT FROM AUTHOR]

Developing suitable cathodes of sodium‐ion batteries (SIBs) with robust electrochemical performance and industrial application potential is crucial for the commercialization of large‐scale stationary energy storage systems. Layered sodium transition metal oxides, NaxTmO2 (Tm representing transition metal), possessing considerable specific capacity, high operational potential, facile synthesis, cost‐effectiveness, and environmentally friendly characteristics, stand out as viable cathode materials. Nevertheless, the prevailing challenge of air‐induced degradation in most NaxTmO2 significantly increases costs associated with production, storage, and transportation, coupled with a rapid decay in reversible capacity. This inherent obstacle inevitably impedes the advancement and commercial viability of SIBs. To address this challenge, it is essential to decode the chemistry of degradation caused by air exposure and develop protective strategies accordingly. In this review, a comprehensive and in‐depth understanding of the fundamental mechanisms associated with air‐induced degradation is provided. Additionally, the current state‐of‐the‐art effective protective strategies are explored and discuss the corresponding sustainability and scalability features. This review concludes with an outlook on present and future research directions concerning air‐stable cathode materials, offering potential avenues for upcoming investigations in advancing alkali metal layered oxides. [ABSTRACT FROM AUTHOR]

Research on novel ultrafast photonic devices with wide adaptability has become important scientific technical means to realize both scheme innovation and performance breakthrough in fiber laser generation. As types of transition metal oxide, manganese dioxide (MnO2) materials exhibit remarkable properties including high photothermal stability, strong oxidation resistance, and excellent optical properties, making them promising candidate for utilization as modulation devices in nonlinear optics and ultrafast optics fields. We investigate the impact of MnO2-based saturable absorber (SA) on the pulse characteristics. The experiment reveals that MnO2-based SA supports effectively pulsed laser generation in wide pump power range and large dispersion parameter space with signal-to-noise ratio more than 85 dB. As far as we know, the pump power response range is outstanding among the most of the reported pulsed lasers, which is attributed to the large modulation depth of MnO2 SA. We also investigate the impact of dispersion on the characteristics of laser output, which is not involved in other similar works. This research indicates that MnO2 as a photonic device has vast potential in advanced ultrafast optics. [ABSTRACT FROM AUTHOR]

Electronic configuration regulation is usually a feasible strategy to boost the electrocatalytic performance for transition metal oxides. Herein, a simple high-temperature annealing method is employed to optimize the electrocatalytic activity towards hydrogen evolution reaction (HER) for spinel oxide Co 3 O 4. The experimental results indicate the simple thermal treatment partially drives the structure reversal in spinel Co 3 O 4 , and it induces the redistribution of cobalt ions at tetrahedral and octahedral sites. Thereby, the electronic configuration regulation occurs, and the e g occupation of cobalt ions at octahedral sites increases up to 1, optimizing the HER reaction kinetics. The sample treated at 900 °C exhibits the highest activity, with overpotential of 335 mV at current density of 10 mA cm−2, and Tafel slope value of 99.3 mV dec−1. This work offers a new way of tuning the electronic configuration in spinel oxides to boost HER electrocatalytic activity. • A simple high-temperature annealing method was adopted to partially drive the structure reversal in Co 3 O 4. • Partial structure reversal can induce redistribution of cobalt ions, and effectively modulate electronic configuration. • Complex spinel exhibited better HER activity than that of normal spinel. [ABSTRACT FROM AUTHOR]

Fuel cells are promising fossil fuel alternatives that are both environmentally friendly and powerful. Direct methanol fuel cells are particularly suitable for lightweight cars and portable electronics. Developing efficient, cost-effective, and eco-friendly catalysts for energy storage and conversion devices is vital for long-term energy security. Numerous studies have explored using metal oxides and modifications to mixed transition metal oxide (MTMO)-based catalysts to enhance the methanol oxidation process. Coupling transition metals (Mn, Co, Ni, Fe, Zn, etc.) in MTMOs improves redox processes and electronic conductivity, advancing electrochemical applications. Among these, nickel cobaltite (NiCo₂O₄) stands out due to its material stability and higher electronic conductivity compared to single-component metal oxides NiO and Co₃O₄. NiCo₂O₄ shows great potential as a composite-based material for fuel cell applications. This paper reviews studies on NiCo₂O₄ as composite-based materials for electrocatalysts, including various methods for synthesizing nanostructures suitable for direct methanol fuel cells. It also highlights the challenges and potential benefits of using NiCo₂O₄ in practical energy storage systems, offering valuable perspectives and insights for early-stage researchers focused on future research and development in composite-based materials for energy applications. [ABSTRACT FROM AUTHOR]

The emergence of new functionalities in transition metal oxides and their interfaces poses an important challenge. Many recent discoveries regarding the polar/nonpolar interface between perovskite oxides open new avenues for modern applications. SrTiO3/LaCrO3 heterostructures are particularly intriguing due to a polar discontinuity along the [001] direction, giving rise to two distinct and controllable interface structures, TiO2-LaO and SrO-CrO2, which exhibit new and promising electronic and thermoelectric transport properties. Through a combination of first-principles simulations based on density functional theory and the Boltzmann transport equation, we have calculate and discuss the structural, electronic, valence band offset, and thermoelectric properties of SrTiO3, LaCrO3, and SrTiO3/LaCrO3 heterostructures. The temperature dependence of the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and figure of merit is determined. Furthermore, we highlight the effect of the interface between the polar perovskite LaCrO3 and the nonpolar SrTiO3(001) on the thermoelectric properties, wherein we observed a change in the metal–semiconductor transport behavior. These results constitute an important advancement in our understanding of the thermoelectric properties at polar/nonpolar perovskite oxide interfaces. [ABSTRACT FROM AUTHOR]

Transition metal oxide semiconductors, noted for their stability and suitable bandgap, are promising photoanodes for water splitting. Surface engineering is critical to tackle issues like low carrier mobility and charge recombination, stemming from atomic arrangement and Fermi level differences. While exposing dominant crystal facets boosts photocatalytic capability, it can hinder carrier injection into the electrolyte. In this study, BiVO4 films with various facet exposures were synthesized and characterized using scanning electron microscopy and x-ray diffraction to confirm their morphology and crystalline structure. Mott–Schottky analysis was employed to investigate changes in the band structure near the semiconductor–electrolyte interface, revealing that high (010)-BiVO4 facet exposure enhances carrier separation but reduces injection efficiency. The results from photoconductive atomic force microscopy tests demonstrated that enhanced band bending at the semiconductor interface improves hole transfer. Coating the (010)-BiVO4 photoanode with MoS2 and an amorphous ZrO2 interlayer yielded a photocurrent density of 0.6 mA cm−2 at 1.2 V (vs RHE) under AM 1.5 G illumination, tripling the pristine photoanode's performance and nearly tripling water splitting efficiency. Mechanism revealing the improved photoelectrochemical performance is attributed to a greater band bending on the BiVO4 surface, enhancing hole injection dynamics. This work provides a feasible strategy for a deeper understanding of the intrinsic mechanisms of facet engineering and improving the activity of photoanodes. [ABSTRACT FROM AUTHOR]

The anomalous Hall effect (AHE), a hallmark of broken time–reversal symmetry, serves as a powerful tool for probing magnetic states and elucidating complex spin–orbit interactions in transition metal oxides. It is reported here that the emergence of AHE signals and interfacial ferromagnetism is directly observed from broken–symmetry integrated perovskite PrCoO3 and brownmillerite SrCoO2.5 superlattices. Through the strategic combinations of these two complex oxide systems onto the substrates with tailored lattice parameters, squared AHE hysteresis loops with perpendicular magnetic anisotropy are found under compressive strain in the optimized superlattices, and the magnitude of the loops is more than three times greater compared to those under tensile strain. The manifestation of AHE in these superlattices is attributed to an extrinsic mechanism involving spin–polarized scattering of charge carriers, with the mismatched perovskite/brownmillerite interfaces acting as the primary scattering centers. These discoveries suggest a promising avenue for the development of artificial materials with controllable AHE properties. [ABSTRACT FROM AUTHOR]

NiO and ZnO mixed nanocomposites were manufactured using the solution combustion process. As-prepared samples were analyzed using XRD. The XRD shows an average crystallite size of 35–40 nm. The elemental composition determined by EDS indicates a nearly equal proportion of Ni and Zn, with an atomic ratio of Ni/Zn = 0.96. The specific capacitances of NiO is 295.5 Fg-1, ZnO is 117.3 Fg-1 and ZnO/NiO nanocomposites is 561.75 Fg-1 which are more than NiO and ZnO alone. This study shows that constructing binary oxide nanocomposites is an approach for developing high-performance supercapacitor electrode materials. Experimental observations on catalytic activity revealed that NiO/ZnO increased catalytic activity. Furthermore, adding NiO to ZnO in the composite increased the overall amount of oxygen vacancies in the samples. Our research lays the door for a simple, inexpensive, nontoxic, and quick technique to synthesize binary transition metal oxide-based electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

2D transition metal halide oxides (TMHOs) have attracted much interest due to their intriguing ferroelectrics and excellent nonlinear optics, however, their susceptibility to oxidation makes their basic research and practical application a challenge. Therefore, it is crucial to understand the oxidation mechanism and explore effective strategies for protection. Here, taking van der Waals (vdWs) ferroelectric NbOI2 as an example, oxidation mechanisms and tuning the oxidation behaviors of NbOI2 and its heterostructures by a variety of in situ experiments and first‐principles calculations are discovered. The ambient‐pressure X‐ray photoelectron spectra reveal a self‐limiting oxidation in isolated NbOI2, driven by spontaneously formed iodine vacancies that react with oxygen molecules due to their lower formation and adsorption energies. For the heterostructures with a lower Fermi level (such as WSe2) than transition state VI@NbOI2 (NbOI2 rich in I‐vacancies), the charge transfer from NbOI2 to WSe2 drives the continuous and complete oxidation of NbOI2 flakes. Moreover, the heterostructures with a higher Fermi level (such as graphene) than VI@NbOI2 can weaken the oxidation of NbOI2. By linking the energy band structures to oxidation behavior, the work offers a new oxidation mechanism of 2D air‐sensitive materials and a crucial strategy for improving their chemical stability. [ABSTRACT FROM AUTHOR]

Low rate activation process is always used in conventional transition metal oxide cathode and fully activates active substances/electrolyte to achieve stable electrochemical performance. However, the related working mechanism in lithium‐sulfur (Li‐ battery is unclear due to the multiple complex chemical reaction steps including the redox of sulfur and the dissolution of polysulfides intermediate. Hence, the influencing mechanism of activation process on Li‐S battery is explored by adopting different current densities of 0.05, 0.2, and 1 C in initial three cycles before long‐term cycling tests at 0.2 C (denoted by 0.05, 0.2, and 1‐battery). 0.05‐battery presents the highest initial capacity in activation process, while 0.2‐battery presents superior electrochemical performances after 150 cycles. The similar trend can be found in more long‐term cycling rates such as 0.02, 0.1, 0.5, and 1 C. Potentiostatically Li2S precipitation test demonstrates that rapid generation of Li2S is achieved at higher current density, and S8‐Li2Sn‐Li2S conversion is accelerated according to Tafel plots. However, interfacial electrochemical and physical characterizations suggest that serious lithium dendrite growth will be induced under high current density. Therefore, considering the reaction kinetics and interfacial properties, low rate activation process is unnecessary when cycling current lower than 1 C for Li‐S battery. [ABSTRACT FROM AUTHOR]

ABSTRACT The rational design of noble metal‐free electrocatalysts represents one of the basic stones for fuel cell development. With the exploration of eco‐friendly nanomaterials for the investigated alcohol oxidation process, nickel‐based electrodes have been recognized as the most auspicious anodes with promoted activity and stability. In this work, a series of NiCo2O4 nanoparticles were deposited onto graphite sheets (NiCo2O4/T) introducing varied proportions of cobalt oxide species. Co‐precipitation protocol of the respective metallic hydroxides onto the carbonaceous support was followed with consecutive annealing in an air atmosphere at 400°C. The fabricated mixed metallic oxide nanopowder was physically studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X‐ray analysis (EDX), X‐ray photoelectron spectroscopy (XPS), and selected area electron diffraction (SAED). Uniformly arranged nanoparticles were observed on graphite surface as evidenced by SEM and TEM. The cubic lattice structure of formed NiCo2O4 crystals was also confirmed by XRD through the defined peaks of binary metallic oxides clarifying their successful preparation scheme. The electrocatalytic properties of these NiCo2O4/T nanocatalysts were evaluated for oxidizing ethanol molecules in basic solution. Pronounced oxidation current densities were remarkably measured at NiCo2O4/T electrodes in relation to that at NiO/T. Differing the introduced cobalt oxide content into the synthesized nanocatalyst significantly controlled its catalytic performance. NiCo2O4/T‐20 exhibited the highest activity and stability among the prepared nanomaterials. Much decreased charge transfer resistances were also recorded at this electrode demonstrating its promoted electron transfer characteristics. This work could provide a reasonable route for the simple synthesis of comparable transition metallic oxides with promising attitudes for energy generation purposes. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs) are increasingly viable choices for catalytic applications because of their tendency to exhibit variable oxidation states depending on the chemical environment and the possibility of enhancing surface activity through morphology control. The development of efficient and cost-effective methods for the synthesis of TMOs with meso-to nanoscale morphologies and improved characteristics remains a significant challenge. Herein, we report a template-free synthesis strategy for the preparation of perforated mesoporous manganese(III) oxide microcubes (PMOM) through a morphology-conserved transformation of the precursor method. The formation of PMOM with cubic structures and pore sizes in the range of 20 nm was confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Mn2O3 samples exhibited a Swiss cheese-like porous structure with a particle size of 0.70 to 1.2 μm. Furthermore, the catalytic activity of the synthesized PMOM samples on the thermocatalytic decomposition of ammonium perchlorate (AP), an oxidizer used in solid propellants, was investigated. The transition between Mn3+ to Mn2+ oxidation states facilitates the transfer of electrons, allowing the metal surface to act as an electron acceptor during the oxidation of water molecules. Due to the oxidation–reduction cycle occurring on the surface, a considerable number of electrons are available for promoting surface reactions. Thus, the (211) surface of PMOM enhanced the thermal decomposition of AP, and a plausible mechanism for this catalytic activity was proposed. [ABSTRACT FROM AUTHOR]

The document is the contents list for an issue of the journal Chemical Communications. It includes articles on various topics such as the synthesis of chiral systems, progress in extractants for actinides and lanthanides separation, and the design of sulfonimide anions for rechargeable lithium batteries. The journal is published by The Royal Society of Chemistry and aims to connect the world with the chemical sciences. [Extracted from the article]

Layered transition metal oxides (TMOs), like the P2-type Na2/3Ni1/3Mn2/3O2, are promising cathodes for sodium-ion batteries but suffer rapid capacity degradation at high voltages. Surface engineering is a popular strategy to modify the high-voltage stability of cathode materials, yet its efficacy for sodium layered TMOs remains elusive, especially given the deleterious layer-gliding phase transition during high-voltage operation. Here, we examined the effect of surface coatings on the high-voltage cycling stability of Na2/3Ni1/3Mn2/3O2, finding that they suppress high-voltage polarization but do not significantly affect capacity retention, which is mainly impacted by bulk structure degradation. Hence, surface engineering must be complemented with bulk structure modification to stabilize high-voltage cycling. [ABSTRACT FROM AUTHOR]

Na‐ion batteries (NIBs) have received considerable attention as promising alternatives to lithium‐ion batteries, particularly for low‐speed electric vehicles and large‐scale energy storage applications. Currently, layered oxide compounds are considered the most important cathode materials for NIBs. However, they suffer from reduced capacity and a shortened lifespan when exposed to water vapor during storage or battery assembly. This article elaborates on the structural and chemical evolution of NaNi1/3Fe1/3Mn1/3O2 (NFM) cathode at the atomic scale in a pure water vapor environment. The Na+/H+ exchange induces the formation of a spinel‐like phase via a multi‐site nucleation mechanism. This transition preferentially occurs either at the cathode surface or along planar defects such as twin boundaries and grain boundaries. Additionally, numerous microcracks perpendicular to <003> direction appear inside NFM grains, further exacerbating the structural deterioration. Upon prolonged exposure to water vapor, NFM grains decompose into a mixture of Na2O and transition metal oxide nanoparticles (FeO, NiO, and MnO), accompanied by the generation of oxygen gas. This research provides a comprehensive atomic‐scale insight into the water vapor instability mechanism of layered oxide cathodes, offering guidance for the design and manufacture of the next generation of water vapor‐tolerant layered oxide cathodes in NIBs. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) nonlayered metal compounds with porous structure show broad application prospects in electrochemistry‐related fields due to their abundant active sites, open ions/electrons diffusion channels, and faradaic reactions. However, scalable and universal synthesis of 2D porous compounds still remains challenging. Here, inspired by blowing gum, a metal‐organic gel (MOG) rapid redox transformation (MRRT) strategy is proposed for the mass production of a wide variety of 2D porous metal oxides. Adequate crosslinking degree of MOG precursor and its rapid redox with NO3− are critical for generating gas pressure from interior to exterior, thus blowing the MOG into 2D carbon nanosheets, which further act as self‐sacrifice template for formation of oxides with porous and ultrathin structure. The versatility of this strategy is demonstrated by the fabrication of 39 metal oxides, including 10 transition metal oxides, one II‐main group oxide, two III‐main group oxides, 22 perovskite oxides, four high‐entropy oxides. As an illustrative verification, the 2D transition metal oxides exhibit excellent capacitive deionization (CDI) performance. Moreover, the assembled CDI cell could act as desalting battery to supply electrical energy during electrode regeneration. This MRRT strategy offers opportunities for achieving universal synthesis of 2D porous oxides with nonlayered structures and studying their electrochemistry‐related applications. [ABSTRACT FROM AUTHOR]

Industrialisation has led to unprecedented levels of outdoor air pollution, posing a significant health risk to human beings. Consequently, there is an urgent need to replace fossil fuels with sustainable energy sources, thereby mitigating these risks and providing a safer outdoor and indoor environment. Titanium dioxide is a versatile transition metal oxide with applications ranging from energy conversion to environmental remediation. However, it faces limitations, particularly in its absorption spectrum and charge separation efficiency, and enhancing these properties remains a significant challenge. In this research work, we have decorated the surface of TiO2 hybridising it with noble‐metal and/or noble‐metal oxides (Ag and/or CuO) to improve the photocatalytic performances (monitoring the removal of nitrogen oxides and benzene, and hydrogen generation from water splitting) under simulated solar‐light irradiation. Our results showed that titania modified with an Ag : Cu molar ratio equal to 1 : 1, not only exhibited the most promising performance in terms of nitrogen oxides and benzene removal, it was the optimum amount for the light‐induced generation of hydrogen from water splitting. [ABSTRACT FROM AUTHOR]

The development of cost-effective and high-performance electrocatalysts for oxygen evolution reaction (OER) would be beneficial to future renewable energy storage. Herein, sulfate modified Fe(OH) x nanosheets grown on nickel foam (S–Fe(OH) x /NF) with rich undercoordinated atom centers and oxygen vacancies were fabricated through a facile hydrothermal method. The optimal sample S 2 –Fe(OH) x /NF exhibits outstanding OER activity with an ultralow overpotential of 261 mV to obtain a current density of 200 mA cm−2. The impressive catalytic activity is primarily attributed to the introduction of the undercoordinated atom (Fe) center, which offer rich active sites, as well as the creation of oxygen vacancies (Vo) that enhance the electron density and the intrinsic conductivity. This work opens up an in-depth understanding of transition metal oxides for OER mechanism by sulfate-decorated and a new prospect for designing highly efficient electrocatalysts. [Display omitted] • The facile solvothermal approach is adopted to achieve the SO 4 2- modified Fe(OH) x /NF nanosheets. • The prepared electrode showed an overpotential of only 261 mV at a current density of 200 mA cm−2. • The impressive catalytic activity is primarily attributed to the introduction of the undercoordinated atom (Fe) centers and Vo. [ABSTRACT FROM AUTHOR]