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Nickel ferrites have served as electrode materials in energy storage applications such as batteries and supercapacitors in comparison to other metal oxides, they have a higher theoretical capacitance range. Pristine metal oxides are poor candidates as electrode components in electrochemical applications because of their tendency to aggregate and their less specific surface areas. Herein, we reported wet impregnation method to incorporate Nickel Ferrite (NiFe2O4) to multiwalled carbon nanotubes (MWCNTs) for improved electrochemical performance of nickel ferrites (NiFe2O4). The synthesized materials attained good crystallinity confirmed by X-ray diffraction (XRD). NiFe2O4 nanoparticle adhesions on multiwalled carbon nanotubes have been confirmed by scanning electron microscopy (SEM). UV-DRS was used to measure the bandgap for optical studies. Cyclic Voltammetry (CV), Galvanostatic Charge/Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS) investigations for supercapacitor applications revealed that synthesized materials demonstrated good electrochemical potential, but MWCNTs supported NiFe2O4 composite attained exceptionally high specific capacitance (CV: 830 F g−1 at 5 mV s−1, GCD:343 F g−1 at current density of 0.1 A g−1) with capacitance retention of 98% at the current density of 0.8 A g−1 after 3500 stability cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • NH 4 PF 6 dual beneficial role, hinders the dendritic growth and accelerate the SEI formation. • Stable lithium deposition stripping over 1500 cycles. • Operando confocal Raman spectroscopy demonstrates the electrolyte degradation in forming the SEI. Lithium-ion batteries (LiBs) with graphite as an anode and lithiated transition metal oxide as a cathode are approaching their specific energy and power theoretical values. To overcome the limitations of LiBs, lithium metal anode with high specific capacity and low negative redox potential is necessary. However, practical application in rechargeable cells is hindered by uncontrolled lithium deposition manifesting, for instance, as Li dendrite growth which can cause formation of dead Li, short circuits and cell failure. The electrochemical behaviour of a protic additive (NH 4 PF 6) in a carbonate-based electrolyte has been investigated by operando confocal Raman spectroscopy, in situ optical microscopy, and X-ray photoelectron spectroscopy, elucidating its functional mechanism. The ammonium cation promotes a chemical modification of the lithium metal anode-electrolyte interphase by producing an N -rich solid electrolyte interphase and chemically modifying the lithium surface morphology by electrochemical pitting. This novel method results in stable lithium deposition and stripping by a decreasing the local current density on the electrode, thus limiting dendritic deposition. [ABSTRACT FROM AUTHOR]

[Display omitted] • The intrinsic mechanism of the external electric field effects on the N 2 adsorption and NN* dissociation performances of three-atom transition metal clusters (TATMCs) is investigated. • Electric fields regulate the charge transfer between TATMCs and NN*, thus affecting the N−N bond activation. • The ICOHP values of two N atoms and E N are not limited by the linear relationship under different electric fields. Three-atom transition metal clusters (TATMCs) with remarkable catalytic activities, especially Nb 3 , Zr 3 , and Y 3 , are proven to be suitable candidates for efficient ammonia production. The pursuit of effective strategies to further promote the ammonia synthesis performance of TATMCs is necessary. In this study, we systematically investigate the effect of external electric fields on tuning the N 2 adsorption and NN* activation performances of Nb 3 , Zr 3 , and Y 3. Our findings demonstrate that the medium and low positive fields promote the N 2 adsorption performance of Nb 3 , while both positive and negative fields enhance nitrogen adsorption on Zr 3. Additionally, electric fields may impede N 2 fixation on Y 3 , yet the N 2 adsorption performance of Y 3 remains considerable. Negative electric fields enhance the NN* activation performance of Nb 3 and Y 3. But only high negative fields weaken the N N bond on Zr 3 , which is attributed to the promotion of the charge accumulation around two N atoms. Notably, Nb 3 and Zr 3 are identified as two TATMCs with the potential for simultaneous optimization of their E N and ICOHP values. This work sheds light on the field effects on the N 2 adsorption and NN* activation performances of TATMCs and guides the design of catalysts for achieving more sustainable ammonia synthesis. [ABSTRACT FROM AUTHOR]

The demand for susceptible and selective hydrogen gas sensors is growing in fuel cells, chemical production, and automotive industries. Detecting H 2 gas at the ppm or ppb level is crucial due to its colourless, odourless, tasteless nature, as well as its flammability and explosiveness. Transition metal dichalcogenides (TMDs) and metal oxide (MO) semiconductors-based hybrid structures have garnered attention in recent years as promising candidates for gas sensing applications owing to their unique properties, including a high surface area, tunable bandgap, and strong gas adsorption. This paper aims to offer insights into the potential of TMD-MO hybrid structures as the next generation of hydrogen gas sensing platforms, contributing to developing highly sensitive and selective gas sensors for diverse industrial applications. TMD-MO hybrid structures are vital for detecting hydrogen gas with high sensitivity and selectivity, which are essential for safe and efficient hydrogen-based systems. Furthermore, these hybrid structures hold significant potential for further customization and enhancement to suit specific applications. Overall, TMD-MO hybrid structures offer a promising avenue for developing next-generation hydrogen gas sensors useable in various industrial applications and promoting a safe and sustainable hydrogen economy. [ABSTRACT FROM AUTHOR]

Nowadays metal oxide nanoparticles and transition metal dichalcogenides play a vital role in various areas like optical sensors, solar cells, energy storage devices, gas sensors and biomedical applications. In the current research work, we synthesized ZrSe2 nanoparticles by hydrothermal method. The ZrSe2 nanoparticles were synthesis using precursors such as ZrOCl2.8H2O and Na2SeO3.5H2O in the addition of surfactant cetyl trimethyl ammonia bromide CTAB and reductant hydrazine hydrate, respectively. Synthesized ZrSe2 nanopowder thick films were developed on a glass substrate using the screen printing method. The structural properties of ZrSe2 powder were studied by X-ray diffraction (XRD). The X-ray diffraction analysis revealed that the hexagonal crystal structure and crystalline size were found to be 55.75 nm. The thick films of ZrSe2 were characterized by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDAX). The surface morphological analysis of ZrSe2 nanostructured thick film shows hierarchical nanoparticles. The energy band gap of synthesized powder was calculated using a Tauc plot from UV-visible spectroscopy. The gas-sensing properties of ZrSe2 thick films were studied. The developed ZrSe2 thick films show maximum sensitivity and selectivity towards the ammonia NH3 gas at an operating temperature of 120°C and the gas concentration was 500 ppm. The developed thick films show fast response and recovery time. [ABSTRACT FROM AUTHOR]

Binary transition metal chalcogenides and reduced graphene oxide exhibit significant potential for energy storage devices due to their superior electronic conductivity and capacity, surpassing that of single-metal sulfides, owing to their more extensive redox reactions. In this report, we introduce a novel synthesis method for producing a mixed-phase MnSe2/CoSe2 nanocomposite wrapped with reduced graphene oxide (rGO) sheets, designed specifically for supercapacitor applications. The MnSe2/CoSe2 hybrid material was synthesized using an ultrasonic assisted hydrothermal technique, followed by the preparation of the rGO/MnSe2/CoSe2 hybrid composite. The structural characterization was conducted employing x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and Raman techniques. Brunauer–Emmett–Teller (BET) analysis demonstrated a significant specific surface area (66.5 m2/g) and a pore size distribution of 28.4 nm in rGO-MnSe2/CoSe2. The interconnected ultrathin rGO nanosheets and conductive carbon layer contributed to the exceptional conductivity and stability achieved by the rGO/MnSe2/CoSe2 composite electrode. The electrochemical performance was assessed using a three-electrode setup in a 3 M KOH solution, with nickel foam as the current collector. The working electrode, consisting of rGO/MnSe2/CoSe2, acetylene black and PVDF in an 80:15:5 weight ratio, demonstrated specific capacitance of 1214 F g−1 and cycling stability of 88% retention after 5000 cycles at 1 A g−1. An asymmetric supercapacitor, constructed using a tailored electrode composition, achieved energy density of 28.6 Wh kg−1 at 2100 W kg−1 and high power density of 888 W kg−1 at 49.7 Wh kg−1. [ABSTRACT FROM AUTHOR]

Tunable optical information storage is crucial in artificial retinal systems for mimicking neurobiological visual characteristics. The perception and storage of light signals rely heavily on the regulation of the conductivity states of memristor materials (e.g., transition metal oxides). Controlling light memristor behavior via defects and polymorphic phases remains underexplored and differs from traditional plasticity training via repeated testing. In this study, defect‐driven ultraviolet light perception and memristor storage with phase transitions in vanadium dioxide (VO2) thin films are presented. The effects of oxygen defects and the corresponding polymorphic phases on ultraviolet light memristors are investigated. The dependence of phonon vibrations and insulator–metal transition behavior on defect levels are revealed. Self‐doping and polymorphs enable VO2 to exhibit distinct ultraviolet memristor performance. It is anticipated that defect‐driven light memristors significantly contribute to the realization of artificial synaptic devices and the implementation of advanced electronic neuron systems. [ABSTRACT FROM AUTHOR]

Renewable and non-renewable energy harvesting and its storage are important components of our everyday economic processes. Lithium-ion batteries (LIBs), with their rechargeable features, high open-circuit voltage, and potential large energy capacities, are one of the ideal alternatives for addressing that endeavor. Despite their widespread use, improving LIBs' performance, such as increasing energy density demand, stability, and safety, remains a significant problem. The anode is an important component in LIBs and determines battery performance. To achieve high-performance batteries, anode subsystems must have a high capacity for ion intercalation/adsorption, high efficiency during charging and discharging operations, minimal reactivity to the electrolyte, excellent cyclability, and non-toxic operation. Group IV elements (Si, Ge, and Sn), transition-metal oxides, nitrides, sulfides, and transition-metal carbonates have all been tested as LIB anode materials. However, these materials have low rate capability due to weak conductivity, dismal cyclability, and fast capacity fading owing to large volume expansion and severe electrode collapse during the cycle operations. Contrarily, carbon nanostructures (1D, 2D, and 3D) have the potential to be employed as anode materials for LIBs due to their large buffer space and Li-ion conductivity. However, their capacity is limited. Blending these two material types to create a conductive and flexible carbon supporting nanocomposite framework as an anode material for LIBs is regarded as one of the most beneficial techniques for improving stability, conductivity, and capacity. This review begins with a quick overview of LIB operations and performance measurement indexes. It then examines the recently reported synthesis methods of carbon-based nanostructured materials and the effects of their properties on high-performance anode materials for LIBs. These include composites made of 1D, 2D, and 3D nanocarbon structures and much higher Li storage-capacity nanostructured compounds (metals, transitional metal oxides, transition-metal sulfides, and other inorganic materials). The strategies employed to improve anode performance by leveraging the intrinsic features of individual constituents and their structural designs are examined. The review concludes with a summary and an outlook for future advancements in this research field. [ABSTRACT FROM AUTHOR]

Increasing the energy density and power of supercapacitors through hybrids of carbonaceous materials and metal oxides continues to be the subject of numerous research works. The correlation between specific capacitance and the properties of materials used as electrodes attracts great interest. In the present study, we investigated composites (GO/Mn3O4) prepared by the hydrothermal method with a variable ratio of GO/Mn3O4 and tested them as supercapacitor electrode materials in three- and two-electrode cells. The chemical characterization carried out by X-ray photoelectron spectroscopy and the adsorption techniques used allowed the determination of the surface carbon and oxygen content, as well as its textural properties. In this work, we analyzed the contribution of the double layer and the Faradaic reactions to the value of the final capacitance of the synthesized materials. Beyond empirically obtaining the electrochemical properties, these have been related to the physicochemical characteristics of the hybrids to help design materials with the best performance for supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

Transition metal oxides such as molybdenum oxide (MoOx) demonstrate significant potential as efficient hole‐selective passivating contacts in silicon heterojunction solar cells. Achieving efficient hole collection necessitates precise control over the optical and electrical properties of MoOx films. In this study, the effects of oxygen flow rate (FO2$F_{O_{2}} $) on the growth, optical properties, and electrical properties of thermally evaporated MoOx films are investigated. In the Kelvin probe force microscopy results, it is indicated that MoOx thin‐film deposition followed an island‐to‐layer growth model. X‐ray photoelectron spectroscopy shows that MoOx films exhibit stoichiometric composition with fully oxidized Mo6+ ions, without additional oxygen. Notably, the O 1s orbital peak shifts toward higher binding energy with increased FO2$F_{O_{2}} $, indicating defect introduction. Consequently, the work function of MoOx films decreases from 5.93 to 5.51 eV as FO2$F_{O_{2}} $ increases from 0 to 8 sccm. The maximum optical bandgap of the MoOx films exceeds 3.60 eV. As a proof of concept, FO2$F_{O_{2}} $'s impact on MoOx as a front buffer layer for dopant‐free silicon solar cells is analyzed. An efficiency of 20.8% was achieved for dopant‐free silicon solar cells after optimized MoOx film deposition, with an open‐circuit voltage of 713.7 mV, short‐circuit current density of 39.1 mA cm−2, and fill factor of 74.6%. [ABSTRACT FROM AUTHOR]

As an ideal transition metal oxide, Co3O4 is a P-type semiconductor with excellent electrical conductivity, non-toxicity and low cost. This work reports the successful construction of Co3O4 materials derived from metal-organic frameworks (MOFs) using a surfactant micelle template-solvothermal method. The modified electrodes are investigated for their ability to electrochemically detect Pb2+ and Cu2+ in aqueous environments. By adjusting the mass ratios of alkaline modifiers, the morphological microstructures of Co3O4-X exhibit a transition from distinctive microspheres composed of fiber stacks to rods. The results indicate that Co3O4-1(NH4F/CO(NH2)2 = 1:0) has a distinctive microsphere structure composed of stacked fibers, unlike the other two materials. Co3O4-1/GCE is used as the active material of the modified electrode, it shows the largest peak response currents to Pb2+ and Cu2+, and efficiently detects Pb2+ and Cu2+ in the aqueous environment individually and simultaneously. The linear response range of Co3O4-1/GCE for the simultaneous detection of Pb2+ and Cu2+ is 0.5–1.5 μM, with the limits of detection (LOD, S/N = 3) are 9.77 nM and 14.97 nM, respectively. The material exhibits a favorable electrochemical response, via a distinctive Co3O4-1 microsphere structure composed of stacked fibers. This structure enhances the number of active adsorption sites on the material, thereby facilitating the adsorption of heavy metal ions (HMIs). The presence of oxygen vacancies (OV) can also facilitate the adsorption of ions. The Co3O4-1/GCE electrode also exhibits excellent anti-interference ability, stability, and repeatability. This is of great practical significance for detecting Pb2+ and Cu2+ in real water samples and provides a new approach for developing high-performance metal oxide electrochemical sensors derived from MOFs. [ABSTRACT FROM AUTHOR]

The three-dimensional (3D) nanosized compactness of devices is in high demand for the spintronic-device applicability. However, very few self-organized, periodic magnetic 3D nanostructures of transition metal oxides are known. Here, we report the direct microscopic evidence of a self-assembled, square-shaped, periodic array of coherent orthogonal nanoblock-type structure in an epitaxial SrRuO3 (SRO) thin film (∼90 nm thickness) grown on (001) LaAlO3 (LAO) using pulsed-laser deposition technique. The evolution of different growth facets of SRO over the LAO single crystalline substrate with different thickness are observed. The combined effect of substrate-induced strain and misfit is utilized to grow such self-assembled, ordered nanostructure. The spontaneous formation of such ordered ferromagnetic nano-devices can fill the gap of a miniaturized spintronic device for magnetic memory-based applications. [ABSTRACT FROM AUTHOR]

Second-order Møller-Plesset perturbation theory (MP2) often breaks down catastrophically in small-gap systems, leaving much to be desired in its performance for myriad chemical applications such as noncovalent interactions, thermochemistry, and dative bonding in transition metal complexes. This divergence problem has reignited interest in Brillouin-Wigner perturbation theory (BWPT), which is regular at all orders but lacks size consistency and extensivity, severely limiting its application to chemistry. In this work, we propose an alternative partitioning of the Hamiltonian that leads to a regular BWPT perturbation series that, through the second order, is size-extensive, size-consistent (provided its Hartree–Fock reference is also), and orbital invariant. Our second-order size-consistent Brillouin-Wigner (BW-s2) approach can describe the exact dissociation limit of H2 in a minimal basis set, regardless of the spin polarization of the reference orbitals. More broadly, we find that BW-s2 offers improvements relative to MP2 for covalent bond breaking, noncovalent interaction energies, and metal/organic reaction energies, although rivaling coupled-cluster with single and double substitutions for thermochemical properties. [ABSTRACT FROM AUTHOR]

Tuning interphase chemistry to stabilize high-voltage NaNi 1/3 Fe 1/3 Mn 1/3 O 2 cathode via bonding superionic conductor interface. [Display omitted] • NASICON-type Na 3 V 2 (PO 4) 3 is bonded on NaNi 1/3 Fe 1/3 Mn 1/3 O 2 surface. • The coating layer inhibits surface parasitic reactions and TMs dissolution. • Fast Na+ kinetic and high rate capacity are achieved for the composite electrode. Unstable cathode/electrolyte interphase and severe interfacial side reaction have long been identified as the main cause for the failure of layered oxide cathode during fast charging and long-term cycling for rechargeable sodium-ion batteries. Here, we report a superionic conductor (Na 3 V 2 (PO 4) 3 , NVP) bonding surface strategy for O3-type layered NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM) cathode to suppress electrolyte corrosion and near-surface structure deconstruction, especially at high operating potential. The strong bonding affinity at the NVP/NFM contact interface stabilizes the crystal structure by inhibiting surface parasitic reactions and transition metal dissolution, thus significantly improving the phase change reversibility at high desodiation state and prolonging the lifespan of NFM cathode. Due to the high-electron-conductivity of NFM, the redox activity of NVP is also enhanced to provide additional capacity. Therefore, benefiting from the fast ion transport kinetics and electrochemical Na+-storage activity of NVP, the composite NFM@NVP electrode displays a high initial coulombic efficiency of 95.5 % at 0.1 C and excellent rate capability (100 mAh g−1 at 20 C) within high cutoff voltage of 4.2 V. The optimized cathode also delivers preeminent cyclic stability with ∼80 % capacity retention after 500 cycles at 2 C. This work sheds light on a facile and universal strategy on improving interphase stability to develop fast-charging and sustainable batteries. [ABSTRACT FROM AUTHOR]

A carbon nanotube and N -doped graphene quantum dot modified (NiMn) Co 2 O 4 composite film was successfully prepared to improve the performance of supercapacitor electrode materials. [Display omitted] • A carbon nanotube and N -doped graphene quantum dot modified (NiMn)Co 2 O 4 composite film was successfully prepared. • The CNT/P-(NiMn)Co 2 O 4 @NGQD electrode shows the excellent specific capacity of 2172.0 F g−1. • The embedding of NGQD provides abundant redox sites and improves the electrochemical performance of CNT/P-(NiMn)Co 2 O 4 @NGQD. • The asymmetric supercapacitor devices CNT/P-(NiMn)Co 2 O 4 @NGQD//AC delivers a high energy density of 94.44 Wh kg−1. The integration of ternary metal oxides into carbon materials is anticipated to significantly boost the electrochemical performance of supercapacitor electrodes. This article synthesized carbon nanotubes (CNT)/(NiMn)Co 2 O 4 composite materials using a straightforward hydrothermal method and subsequently prepared composite thin films of CNT/P-(NiMn)Co 2 O 4 @NGQD by phosphating and incorporating nitrogen-doped graphene quantum dots (NGQD). These films served as the functional electrode material for supercapacitors, enhancing their performance capabilities. The specific capacity of CNT/P-(NiMn)Co 2 O 4 @NGQD was measured at 2172.0 F g−1 at a current density of 1 A g−1, maintaining a capacitance of 1954.0 F g−1 at 10 A g−1, thus demonstrating excellent rate performance. Electrochemical impedance spectroscopy (EIS) further revealed enhancements in electrolyte flow dynamics and capacitance behavior post-NGQD introduction. The energy density of the composite material reached 94.4 Wh kg−1 at power density of 800 W kg−1, demonstrating superior electrochemical performance. The enhancement in these electrochemical properties is attributed to the high specific surface area and active sites of CNT/P-(NiMn)Co 2 O 4 @NGQD films, along with the synergistic effects of NGQD and metal ions facilitating rapid electrons and charge transfer. This work provides new insights into developing high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Ov-Co 2 NiO 4 /NC nanoflowers were successfully synthesized using a straightforward method, targeting high-performance PIHCs. The nanoflower architecture increases the contact area between the active material and the electrolyte. DFT calculations reveal that oxygen vacancies enhance the charge density across the Fermi level in Co 2 NiO 4 and increase the interatomic distance between adjacent cobalt and nickel atoms to 3.370 Å. Additionally, N-doped carbon supports facilitate faster charge transfer, augment electrostatic energy storage, and prevent the structural collapse of Co 2 NiO 4. These structural enhancements improve electrochemical reaction kinetics, increase K+ binding energy (−2.87 eV), and mitigate structural changes during K+ storage. [Display omitted] • A facile synthesis approach to fabricate nitrogen-doped carbon-supported oxygen vacancy-rich Co 2 NiO 4 nanoflowers. • Oxygen vacancies could expand the interatomic distances between adjacent cobalt and nickel atoms to 3.370 Å. • N-doped carbon carriers further accelerate charge transfer, increase the electrostatic energy storage and inhibit the structural collapse of Co 2 NiO 4. • Ov-Co 2 NiO 4 /NC NF exhibits a specific capacitance of 1104 F g−1 at 0.5 A g−1 and capacitance retention of 91.48 % after 6500 cycles in 6 M KOH electrolyte. • The assembled potassium-ion hybrid supercapacitors demonstrates an energy density of 47.8 Wh kg−1 and an ultra-high power density of 376 W kg−1. Transition metal oxides represent a promising category of pseudocapacitive materials for potassium-ion hybrid supercapacitors (PIHCs) characterized by high energy density. Nevertheless, their utility is hindered by intrinsic low conductivity, restricted electrochemical sites, and notable volume expansion, all of which directly contribute to the degradation of their electrochemical performance, thereby limiting their practical applicability in supercapacitor systems. In this study, we present a facile synthesis approach to fabricate nitrogen-doped carbon-supported oxygen vacancy-rich Co 2 NiO 4 nanoflowers (Ov-Co 2 NiO 4 /NC NFs) featuring tunable surface layering and electron distribution. The nanoflower structure augments the contact area between the material and the electrolyte. Density functional theory (DFT) calculations reveal oxygen vacancies could bring an enhanced charge density across the entire Fermi level in Co 2 NiO 4 and expand the interatomic distances between adjacent cobalt and nickel atoms to 3.370 Å. N-doped carbon carriers further accelerate charge transfer, increase the electrostatic energy storage and inhibit the structural collapse of Co 2 NiO 4. These structural modifications serve to improve electrochemical reaction kinetics, augment the binding energy of K+ (−2.87 eV), and mitigate structural variations during K+ storage. In a 6 M KOH electrolyte, Ov-Co 2 NiO 4 /NC NF exhibits a specific capacitance of 1104 F g−1 at a current density of 0.5 A g−1, with a remarkable capacitance retention rate of 91.48 % after 6500 cycles. Furthermore, the assembled PIHCs demonstrate an energy density of 47.8 Wh kg−1 and an ultra-high power density of 376 W kg−1, alongside notable cycle stability, retaining 90.13 % of its capacitance after 8000 cycles in a 6 M KOH electrolyte. [ABSTRACT FROM AUTHOR]

Entropy-induced high-density grain boundaries is favorable for improved capacity and cycling stability. [Display omitted] • Co-free high entropy oxide was synthesized by a simple solution combustion method. • HEO anode exhibits high capacity (1374 mAh g−1) and excellent cycling stability. • High-density grain boundaries contribute to improved capacity and cycling stability. Transition metal oxides (TMOs) with high discharge capacity are considered as one of the most promising anodes for lithium-ion batteries. However, the practical utilization of TMOs is largely limited by cycling stability issues arising from volume expansion, structural collapse. In this study, we synthesized a high-entropy spinel oxide material (FeCrNiMnZn) 3 O 4 using a solution combustion method. With the implementation of five cations through high-entropy engineering, the agglomeration and expansion of the electrode materials during charging and discharging are suppressed, and the cycling stability is enhanced. The results demonstrate that entropy-induced high-density grain boundaries and the reversibility of spinel structure contribute to improved capacity and cycling stability. Herein, (FeCrNiMnZn) 3 O 4 provides a high capacity (1374 mAh g−1) at 0.1 A g−1 and superior cycling stability (almost 100 %) during 200 cycles with a current density of 0.5 A g−1. The study provides valuable understanding for designing the high entropy oxides anode electrodes. [ABSTRACT FROM AUTHOR]

A self-supporting film embedded with nitrogen doped graphene quantum dots into (Ni 0.5 Co 0.5) 3 V 2 O 8 nanosheets has been successfully prepared for high-performance supercapacitors. [Display omitted] • A self-supporting film embedded with (NGQD) into (Ni 0.5 Co 0.5) 3 V 2 O 8 nanosheets has been successfully prepared. • The (Ni 0.5 Co 0.5) 3 V 2 O 8 /NGQD@CNT electrode shows the excellent specific capacity of 3018.2 F g−1. • The embedding of NGQD provides abundant redox sites and improves the electrochemical performance of (Ni 0.5 Co 0.5) 3 V 2 O 8. • The asymmetric supercapacitor devices (Ni 0.5 Co 0.5) 3 V 2 O 8 /NGQD@CNT//AC delivers a high energy density of 166.2 Wh kg−1. To improve the electrochemical performance of positive electrode materials, constructing graded nanostructures is a worthwhile approach. This study successfully synthesized nitrogen-doped graphene quantum dots (NGQD) modified (Ni 0.5 Co 0.5) 3 V 2 O 8 on a carbon nanotube (CNT) substrate to construct self-supporting electrodes for high-performance supercapacitors. The (Ni 0.5 Co 0.5) 3 V 2 O 8 nanosheets were successfully wrapped onto the CNT surface through a solution impregnation process, which increased the specific surface area and interlayer spacing of the material. Furthermore, the electrochemical properties of the electrode material underwent significant enhancement due to the synergistic interplay between metal ions and the numerous redox centers. The embedding of the NGQD enriched the materials with active sites and further improved its specific capacity without compromising the structure intergrity of the layer configuration. Using CNT as the substrate ensured the self-supporting nature of the electrode. Consequently, the (Ni 0.5 Co 0.5) 3 V 2 O 8 /NGQD@CNT composite exhibits an ultra-high specific capacitance of 3018.2 F g−1 at 1 A g−1 and 2332 F g−1 at 10 A g−1. The asymmetric supercapacitor constructed with (Ni 0.5 Co 0.5) 3 V 2 O 8 /NGQD@CNT and activated carbon (AC) presented an impressive energy density of 160.2 Wh kg−1 at a power density of 800 W kg−1. After 8000 charge–discharge cycles, the capacity retention rate was 78.5 %, with a Coulo mbic efficiency consistently above 98 %. [ABSTRACT FROM AUTHOR]

New SCR catalysts based on Mn supported on simple or mixed aerogel oxides (Mn/ZrO2, Mn/CeO2-ZrO2 and Mn/CeO2-ZrO2-SO42−) were prepared for selective catalytic reduction of nitrogen oxide by ammonia (NO-SCR by NH3). One step sol gel method followed by supercritical drying process were used for elaborating the catalytic supports, however, Mn species were incorporated into aerogels via impregnation method. Structural, textural, acidic and redox properties of samples were studied using XRD; BET and porosity measurements; NH3-TPD and H2-TPR techniques. The results revealed that Mn/ZrO2 and Mn/CeO2-ZrO2 solids develop mesoporous texture, good crystallinity of zirconia tetragonal phase and nano-sized particles but exhibit a poor NO-SCR activity. The addition of SO42− induces a disorder in ZrO2 structure but it generates very active strong acid sites for the high temperature NO reduction. 100% NO conversion into N2 was achieved above 400 °C over the new Mn/CeO2-ZrO2-SO42− catalytic system. [ABSTRACT FROM AUTHOR]

[Display omitted] The design and fabrication of high-performance, inexpensive and durable electrocatalyst toward hydrogen evolution reaction (HER) is supremely significant for alleviating energy crisis and environmental concerns, but still remaining challenging. Herein, we develop an experimental work based on etching and reduction strategy to reveal the remarkable effect of cation/anion co-doping in CoMoO 4 on its intrinsic HER activity. The CoMoO 4 with Fe and B incorporation (Fe/B-CoMoO 4) exhibits a current density of 10 mA cm−2 with strikingly low potential of 38 mV coupling with Tafel slope of 51 mV dec-1, and manifesting a robust durability for 100 h with no attenuation, which is comparable to the state-of-the-art commercial Pt/C catalyst. The collective experimental and theoretical findings concomitantly illustrate that the enhanced performances are due to the strong synergistic effect resulting from the co-doping of Fe and B, which plays a pivotal role in finely tuning the electronic structure of CoMoO 4 , further optimizing the adsorption free energy of H intermediates and shifting the center of the d -band of Fe/B-CoMoO 4 away from the Fermi level. This fantastic work highlights the critical role of foreign element incorporating for optimizing electronic structure of transition metal oxides toward HER, and offers valuable guiding principles for rational design of more efficient energy conversion devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defectivation of Bi 2 O 3 and compositing with rGO is simultaneously realized by a one-step reducing method. • The Bi 2 O 3 -rGO-100 anode exhibits a high specific capacitance of 1053F/g at 1 A/g. • The Ni 3 Co 2 -rGO//Bi 2 O 3 -rGO-100 battery-type pouch-cell supercapacitor achieves an energy density of 118.5 Wh kg−1 at a power density of 850 W kg−1. • Two series-connected pouch-cell supercapacitor successfully illuminate 88 LED lamps for 12 min. We prepare bismuth oxide-reduced graphene oxide (Bi 2 O 3 -rGO) composite anode using a one-step chemical precipitation/reduction method. Under a reducing atmosphere, oxygen atoms on the surface of Bi 2 O 3 are gradually removed and neighboring oxygen atoms migrate to the surface, leaving oxygen vacancies. Defective Bi 2 O 3 enhances the number of active sites, providing additional pseudocapacitive performance. The transition metal oxide-based Bi 2 O 3 acts as an anode, providing capacitive performance that far exceeds that of conventional carbon materials. Moreover, the introduction of rGO forms a conductive network for Bi 2 O 3 , improving capacitive contribution and ion diffusion capabilities for the electrode. The Bi 2 O 3 -rGO-100 (GO added at 100 mg) exhibits a high specific capacitance of 1053F/g at 1 A/g, significantly higher than that of Bi 2 O 3 (866F/g). The Bi 2 O 3 -rGO-100 anode and Ni 3 Co 2 -rGO cathode are assembled into a battery-type supercapacitor. The coin-cell device achieves an energy density of 88.2 Wh kg−1 at a power density of 850 W kg−1. The Ni 3 Co 2 -rGO//Bi 2 O 3 -rGO-100 pouch-cell device demonstrates an extremely low R ct of 0.77 Ω. At a power density of 850 W kg−1, the energy density reaches 118.5 Wh kg−1, and remains 67.4 Wh kg−1 at 8500 W kg−1. [ABSTRACT FROM AUTHOR]

• Ca-based, non-Ca-based additives and recycled solid wastes reduce PI and enhance TD. • These active ingredients improve soil texture via cation exchange and flocculation. • Transition metal oxides catalyze TD of nonchlorinated POPs via two mechanisms. • We also reviewed alkali, solid wastes and nano metals as catalysts to enhance TD. • Additives in photo- and photo-thermal-catalysis and their mechanisms are reviewed. High temperatures and providing sufficient time for the thermal desorption of persistent organic pollutants (POPs) from contaminated clay soils can lead to intensive energy consumption. Therefore, this article provides a critical review of the potential additives which can improve soil texture and increase the volatility of POPs, and then discusses their enhanced mechanisms for contributing to a green economy. Ca-based additives have been used to reduce plasticity of bentonite clay, absorb water and replenish system heat. In contrast, non-Ca-based additives have been used to decrease the plasticity of kaolin clay. The soil structure and soil plasticity can be changed through cation exchange and flocculation processes. The transition metal oxides and alkali metal oxides can be applied to catalyze and oxidize polycyclic aromatic hydrocarbons, petroleum and emerging contaminants. In this system, reactive oxygen species (•O 2 − and •OH) are generated from thermal excitation without strong chemical oxidants. Moreover, multiple active ingredients in recycled solid wastes can be controlled to reduce soil plasticity and enhance thermal catalysis. Alternatively, the alkali, nano zero-valent iron and nano-TiN can catalyze hydrodechlorination of POPs under reductive conditions. Especially, photo and photo-thermal catalysis are discussed to accelerate replacement of fossil fuels by renewable energy in thermal remediation. [Display omitted] [ABSTRACT FROM AUTHOR]

A synergism between CoMo and Fe 2 O 3 dominating the prominent HER and OER performance is demonstrated. [Display omitted] • Novel CoMo/Fe 2 O 3 /NF nanoarchitecture is designed for overall water splitting. • The optimized CoMo/Fe 2 O 3 /NF exhibits outstanding HER and OER catalytic activity. • The constructed overall water-splitting cell attains 10mA cm−2 at 1.5 V. • The synergistic effect between multiple metals dominates the high catalytic activity. Constructing bifunctional non-precious metal electrocatalysts with advanced industrial value and excellent electrocatalytic performance to achieve efficient overall water splitting is important but difficult. Herein, a heterogeneous electrocatalyst comprising of CoMo alloys anchored Fe 2 O 3 nanosheets was prepared by hydrothermal and electrodeposition methods. The strongly coupled interfaces between the CoMo alloys and Fe 2 O 3 nanosheets promote charge redistribution, which could improve electron transfer efficiency and accelerate reaction kinetics, potentially optimizing reactant adsorption energy. Further density functional theory (DFT) calculations reveal that the construction of CoMo/Fe 2 O 3 /NF heterostructured catalyst facilitates to promote interfacial charge redistribution and enhance charge transfer capacity, thus boosting the catalytic performance. Benefiting from this, the optimal CoMo/Fe 2 O 3 /NF heterostructure demonstrates a minimal overpotential of 71 mV at 10 mA cm−2 for the HER and 266 mV at 50 mA cm−2 for the OER. Remarkably, the catalyst served as a bifunctional electrode for water splitting, resulting in a cell voltage down to 1.5 V at a current density of 10 mA cm−2. This research provides an effective way for the construction of non-precious iron oxides-based bifunctional electrocatalysts using alloy/metal oxide interfacial engineering strategy. [ABSTRACT FROM AUTHOR]

Zeolite imidazole framework −8 (ZIF-8) was used as the encapsulation layer to improve the stability and activity of ZnO nanoparticles. Under the voltage of 2.0 V vs.RHE, the stability test could be carried out for 60 h, and the yield of H 2 O 2 did not decrease significantly. [Display omitted] A promising method of producing hydrogen peroxide (H 2 O 2) is the electrochemical two-electron water oxidation reaction (2e− WOR). In this process, it is important to design electrocatalysts that are both earth abundant and environmentally friendly, as well as offering high stability and production rates. The research of WOR catalysts, such as the extensively used transition metal oxides, is mainly focused on the modification of transition metal elements. Few studies pay attention to the protective heterostructure of metal oxides. Here, we demonstrate for the first time an organometallic skeleton protection strategy to develop highly stable WOR catalysts for H 2 O 2 generation. Unlike the pure ZnO and zeolite imidazole framework-8 (ZIF-8) catalysts, ZnO@ZIF-8 enabled the production of hydrogen peroxide at high voltages. The experimental results demonstrate that the ZnO@ZIF-8 catalyst stably generates H 2 O 2 even under a high voltage of 3.0 V vs. RHE, with a yield reaching 2845.819 μmolmin−1 g−1. ZnO@ZIF-8 shows a relatively low overpotential, with a current density of 10 mA cm−2 and an overpotential of 110 mV. The ZnO@ZIF-8 catalyst's maximal FE value was 4.72 %. Moreover, the ZnO@ZIF-8 catalyst exhibits remarkable durability even after an extended 60-hour stability test. Operando Raman and theoretic calculation analyses reveal that the metal–organic skeleton being encapsulated on the metal oxide surface synergizes with each other, not only expanding the electrochemical surface area, but also adjusting the catalyst metal sites' adsorption capacity. A novel approach to the modification of 2e− WOR metal oxide catalyst is presented in this work. [ABSTRACT FROM AUTHOR]

Samples in the La 2 MoO 6 – Sm 2 MoO 6 – MoO 3 system were obtained using the solid-state synthesis method. The phase formation in the given compositional section was firstly studied, and the homogeneity region of the fluorite-like lanthanum-samarium molybdate was determined, as confirmed by XRD analysis including Rietveld refinement and SEM with energy-dispersive microanalysis. The fluorite-like phase contains less molybdenum than the isostructural neodymium molybdate Nd 5 Mo 3 O 16+δ. The homogeneity region of fluorite-like solid solutions has been determined, which corresponds to the La 5-x Sm x Mo 2.75 O 15.75 section in the composition range 2.5 ≤ x ≤ 3.5. The crystal structure is characterized by the splitting of cation positions and the presence of excess oxygen in the octahedral voids of the structure. Oxygen atoms in the octahedral positions are displaced from the center of the voids and enter into the molybdenum coordination sphere. The density of single-phase ceramic samples increases with the increase in samarium content. The conductive properties of single-phase ceramics were investigated in an air atmosphere using impedance spectroscopy. The total conductivity was ∼10−2 S cm−1 for La 2.5 Sm 2.5 Mo 2.75 O 15.75 at 800 °C. The grain bulk conductivity exhibits a break at a temperature of approximately 600 °C, which may be explained by the depletion of charge carriers in the structure. [ABSTRACT FROM AUTHOR]

Nanocomposites of SrBi (2-X) (CF) X Nb 2 O 9 (SBNCF) (CF=CoFe 2 O 4 for X = 0.0 to 0.5 with a step increment of 0.1) were synthesized using the hydrothermal method and characterized for their structural, morphological, elastic, and optical properties. The incorporation of CF into SrBi 2 Nb 2 O 9 (SBN) resulted in hybrid composites with tailored properties. X-ray Diffraction (XRD) with Rietveld refinement analysis confirmed the formation of orthorhombic SBN and spinel CF phases. Field Emission Gun Scanning Electron Microscopy (FEG-SEM) revealed that SBN exhibits a plate-like morphology, with the incorporation of CF into the SBN matrix resulting in both plate-like and octahedral-shaped grains. The Brunauer–Emmett–Teller (BET) method was used to determine the pore radius and surface area, both of which were found to have increased, indicating an enhancement in photocatalytic performance. The presence of the constituent elements in the prepared compositions was confirmed by Energy Dispersive Spectroscopy (EDS). Fourier Transform Infrared Spectroscopy (FTIR) spectra were used to determine elastic properties, suggesting potential applications in electronic noise filtering. From Diffuse Reflectance Spectroscopy (DRS), a recognizable semiconducting behavior and band gap bowing were noticed in SBNCF nanocomposites on the obtained energy band gap values (2.20 eV–1.56 eV) compared to the SBN host matrix (3.16 eV). The materials exhibited strong emission peaks at 470 nm, 528 nm, 584 nm, and 703 nm upon the excitation of 425 nm light using Photoluminescence (PL) spectroscopy. The white emission was predominant at room temperature in all the produced samples and the corresponding color temperature values range from 5865.93 K to 7599.05 K from the CIE diagram. The SBNCF materials are promising candidates in photocatalytic reactions and white light-emitting diodes (w-LEDs) based on their enhanced optical properties. [ABSTRACT FROM AUTHOR]

Chromism, the phenomenon of color change in response to external stimuli, encompasses various mechanisms, including electro-, photo- and thermo-chromism. These phenomena find applications in technologies like smart windows and displays. Transition metal oxides, such as VO2, are known for chromic applications, generally the metal-insulator transition in VO2 accompanied by a structural phase transition, making it a potential candidate for smart windows. This study demonstrates a different approach to chromism in VO2 by proton doping thin films through the Pt catalyst effect. This method significantly alters the crystal structure and tunes the bandgap, resulting in a color change from brown to transparent with enhanced transmittance compared to the conventional metal-insulator transition chromism in VO2. Hydrogen concentration in the thin film was investigated using elastic recoil detection analysis, revealing insights into the amount of protons. Successful proton doping induces a remarkable transition in crystal structure, generating lattice elastic energy at interstices, triggering micro-level changes. The controllability of this effect holds promise for applications in smart windows with instantaneous color changes and dynamic optical devices. [ABSTRACT FROM AUTHOR]

The article explores the orientation-dependent electrochemical response of LaSrNiO4 (LSNO) epitaxial films by investigating the influence of growth orientation on electrochemical reactions. The study reveals that the resistance of (100)-oriented LSNO films can be modulated significantly by electrochemical reactions, while the resistance of (001)-oriented films remains largely unaffected. The results suggest that oxygen vacancies are produced in the NiO2 layer of LSNO during electrochemical reactions, with diffusion of oxygen ions occurring preferentially within the NiO2 layer. [Extracted from the article]

Glasses formed from transition metal oxides have shown tailorable electrical and optical properties depending on the valence state and individual element. Vanadate glasses have received specific attention for their high conductivities as compared to most glass families. In this study, the frequency‐dependent capacitance and direct current (dc) conductivity properties of alkaline earth vanadate glasses were investigated. Glasses in the xSrO–(100 − x)V2O5 and xBaO–(100 − x)V2O5 systems, where x = 30, 40, and 50 in mol%, were prepared via melt‐quench synthesis. Capacitance measurements were used to calculate dielectric constants, dielectric loss, and alternating current (ac) conductivity for each sample. Dielectric constants varied between 10–13 and 14–16 for SrO–V2O5 and BaO–V2O5 glasses, respectively, at 1 MHz. Current measurements were made as a function of temperature and voltage for each glass sample. A strong dependence on vanadate content was noted where temperature had a less strong effect. Activation energies were calculated to describe electrical transport mechanisms. All samples showed activation energies governed by electron hopping mechanisms. Such vanadate glasses have properties suitable for applications as cathode materials for batteries, solid state electrolytes, and conductive glass paste with potential for electro‐optic effects involving nonlinear processes. [ABSTRACT FROM AUTHOR]

[Display omitted] Water splitting is a promising technique for clean hydrogen production. To improve the sluggish hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), the development of efficient bifunctional electrocatalysts for both HER and OER is urgent to approach the scale-up applications of water splitting. Nowadays transition metal oxides (TMOs) are considered as the promising electrocatalysts due to their low cost, structural flexibility and stability, however, their electrocatalytic activities are eager to be improved. Here, we synthesized waxberry-like hydrophilic Co-doped ZnFe 2 O 4 electrocatalysts as bifunctional electrocatalysts for water splitting. Due to the enhanced active sites by electronic structure tuning and modified super-hydrophilic characteristics, the spinel ZFO-Co 0.5 electrocatalyst exhibits excellent catalytic activities for both OER and HER. It exhibits a remarkable low OER overpotential of 220 mV at a current density of 10 mA cm−2 and a Tafel slope of 28.2 mV dec-1. Meanwhile, it achieves a low overpotential of 73 mV at a current density of 10 mA cm−2 with the Tafel slope of 87 mV dec-1 for HER. In addition, for water electrolysis device, the electrocatalytic performance of ZFO-Co 0.5 ||ZFO-Co 0.5 surpasses that of commercial IrO 2 ||Pt/C. Our work reveals that the hydrophilic morphology regulation combined with metallic doping strategy is a facile and effective approach to synthesize spinel TMOs as excellent bifunctional electrocatalyst for water splitting. [ABSTRACT FROM AUTHOR]

Transition metal oxide (TMO) anodes show inferior sodium ion storage performance compared with that of lithium ion storage owing to the larger radium size and heavier elemental mass of Na+ than Li+. Effective strategies are highly desired to improve the Na+ storage performance of TMOs for applications. In this work, using ZnFe2O4@xC nanocomposites as model materials for investigation, we found that by manipulating the particle sizes of the inner TMOs core and the features of outer carbon coating, the Na+ storage performance can be significantly improved. The ZnFe2O4@1C with a diameter of the inner ZnFe2O4 core of around 200 nm coated by a thin carbon layer of around 3 nm shows a specific capacity of only 120 mA h g−1. The ZnFe2O4@6.5C with a diameter of the inner ZnFe2O4 core of around 110 nm embedding in a porous interconnected carbon matrix displays a significantly improved specific capacity of 420 mA h g−1 at the same specific current. Furthermore, the latter shows an excellent cycling stability of 1000 cycles with a capacity retention of 90% of the initial 220 mA h g−1 specific capacity at 1.0 A g−1. TEM, electrochemical impedance spectroscopy, and kinetic analysis show that the inner ZnFe2O4 core with reduced particle size and the outer thicker and interconnected carbon matrix synergistically improve the active reaction sites, integrity, electric conductivity, and pseudocapacitive-controlled contribution of ZnFe2O4@xC nanocomposites, thus leading to an overall enhanced Na+ storage performance. Our findings create a universal, facile, and effective method to enhance the Na+ storage performance of the TMO@C nanomaterials. [ABSTRACT FROM AUTHOR]

The peculiar potential transition metal dichalcogenides in regard to sensor and device applications have been exhibited by both experimental and theoretical studies. The use of these materials, thermodynamically stable even at elevated temperatures, particularly in nano- and optoelectronic technology, is about to come true. On the other hand, the distinct electronic and thermal transport properties possessing unique coherency, which may result in higher thermoelectric efficiency, have also been reported. However, exploiting this potential in terms of power generation and cooling applications requires a deeper understanding of these materials in this regard. This perspective study, concentrated with this intention, summarizes thermoelectric research based on transition metal dichalcogenides from a broad perspective and also provides a general evaluation of future theoretical investigations inevitable to shed more light on the physics of electronic and thermal transport in these materials and to lead future experimental research. [ABSTRACT FROM AUTHOR]

The structural, mechanical, and electronic properties of Ni–Co-based layered transition oxide LiNixCo1−xO2 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9) (LNCO) have been investigated using the first-principles method. The results show that the effect of Ni/Co mixing on the structural property is slight. For the case of the mechanical property, the elastic constant, elastic modulus, such as Young's modulus (Y), Poisson's ratio (v), Pugh's ratio (B/G), and Cauchy pressure (C′) of LNCO have been carefully analyzed based on the strain-energy method. The results demonstrate that the mechanical strength of LNCO materials is weaker than that of pure LiCoO2 (LCO) and LiNiO2 (LNO). However, the B/G ratio and Poisson's ratio of LNCO are greater than that of the pure LCO and LNO, which means that Ni/Co mixing can improve the ductility of pure LCO and LNO. In addition, Cauchy pressure and anisotropy are also discussed, and as cathode materials, LNCO still exhibits good electrical conductivity. Our results provide a feasible way to realize mechanical property modulation by Ni–Co-based layered transition metal oxides LCO. Furthermore, our study is also helpful to reveal the formation mechanism of intra-lattice microcracks in electrode materials. [ABSTRACT FROM AUTHOR]

While the dissociative recombination (DR) of ground-state molecular ions with low-energy free electrons is generally known to be exothermic, it has been predicted to be endothermic for a class of transition-metal oxide ions. To understand this unusual case, the electron recombination of titanium oxide ions (TiO+) with electrons has been experimentally investigated using the Cryogenic Storage Ring. In its low radiation field, the TiO+ ions relax internally to low rotational excitation (≲100 K). Under controlled collision energies down to ∼ 2 meV within the merged electron and ion beam configuration, fragment imaging has been applied to determine the kinetic energy released to Ti and O neutral reaction products. Detailed analysis of the fragment imaging data considering the reactant and product excitation channels reveals an endothermicity for the TiO+ dissociative electron recombination of (+4 ± 10) meV. This result improves the accuracy of the energy balance by a factor of 7 compared to that found indirectly from hitherto known molecular properties. Conversely, the present endothermicity yields improved dissociation energy values for D0(TiO) = (6.824 ± 0.010) eV and D0(TiO+) = (6.832 ± 0.010) eV. All thermochemistry values were compared to new coupled-cluster calculations and found to be in good agreement. Moreover, absolute rate coefficients for the electron recombination of rotationally relaxed ions have been measured, yielding an upper limit of 1 × 10−7 cm3 s−1 for typical conditions of cold astrophysical media. Strong variation of the DR rate with the TiO+ internal excitation is predicted. Furthermore, potential energy curves for TiO+ and TiO have been calculated using a multi-reference configuration interaction method to constrain quantum-dynamical paths driving the observed TiO+ electron recombination. [ABSTRACT FROM AUTHOR]

Transition metal oxides, especially cobalt oxides and hydroxides, are of great interest as precious metal free electrode materials for the oxygen evolution reaction (OER) in electrochemical and photoelectrochemical water splitting. Here, we present detailed studies of the potential‐ and pH‐dependent structure and structural stability of Co3O4 and CoOOH in neutral to alkaline electrolytes (pH 7 to 13), using operando surface X‐ray diffraction, atomic force microscopy, and electrochemical measurements. The experiments cover the pre‐OER and OER range and were performed on epitaxial Co3O4(111) and CoOOH(001) films electrodeposited on Au(111) single crystal electrodes. The CoOOH films were structurally perfectly stable under all experimental conditions, whereas Co3O4 films exhibit at all pH values reversible potential‐dependent structural transformations of a sub‐nanometer thick skin layer region at the oxide surface, as reported previously for pH 13 (F. Reikowski et al., ACS Catal. 2019, 9, 3811). The intrinsic OER activity at 1.65 V versus the reversible hydrogen electrode decreases strongly with decreasing pH, indicating a reaction order of 0.2 with respect to [OH−]. While the Co3O4 spinel is stable at pH 13, intermittent exposure to electrolytes with pH≤10 results in dissolution as well as gradual degradation of its OER activity in subsequent measurements at pH 13. [ABSTRACT FROM AUTHOR]

A Ni x Co 1-x O/HCS catalyst with superior water-splitting is presented. High water-splitting reaction kinetics and enhanced durability were observed. The structure-function relationship was investigated with XPS, which demonstrated the presence of dominant Ni2+ and Co2+ species and a functionalized HCS support where nucleation of small metal oxide nanoparticles occurred. The PDF showed broadened Nickel/Cobalt-oxide bonds and expansion of the metal-metal pair distances. The alteration of the Metal-Oxide and Metal-Metal-Oxide bonds favored better HER and OER electrocatalysis, also as supported by DFT. EXAFS showed the existence of the bimetallic oxide catalyst and the stretching of the Ni–O bonds due to the coordination of the Ni–O with the Co. The composite exhibited higher activity and enhanced electrocatalytic mechanism towards water splitting through higher exchange current densities (0.615 and 0.886 mA cm−2) and low charge transfer resistance (14 and 10 Ω) respectively. Chronoamperometry proved the catalyst's stability during prolonged electrolysis. [Display omitted] • Successful preparation of homogeneously dispersed Ni x Co 1-x O nanoparticles supported on porous and graphitic hollow carbon spheres (HCS). • Characterization of materials demonstrated short-range order crystallinity of the Ni x Co 1-x O bimetallic transition metal oxides. • Pair distribution function (PDF), Extended x-ray absorption fine structure (EXAFS), and powder x-ray diffraction (PXRD) data elucidated the structure of the materials and proposed a mechanism attributed to the improved overall water splitting. • The small domain size of the bimetallic oxide catalysts and synergistic effects between Ni and Co oxides significantly contribute to the observed activity and durability of the catalysts. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs) are promising cathode materials for aqueous zinc ion batteries (ZIBs), however, their performance is hindered by a substantial Hubbard gap, which limits electron transfer and battery cyclability. Addressing this, we introduce a heteroatom coordination approach, using triethanolamine to induce axial N coordination on Mn centers in MnO2, yielding N‐coordinated MnO2 (TEAMO). This approach leverages the change of electronegativity disparity between Mn and ligands (O and N) to disrupt spin symmetry and augment spin polarization. This enhancement leads to the closure of the Hubbard gap, primarily driven by the intensified occupancy of the Mn eg orbitals. The resultant TEAMO exhibit a significant increase in storage capacity, reaching 351 mAh g−1 at 0.1 A g−1. Our findings suggest a viable strategy for optimizing the electronic structure of TMO cathodes, enhancing the potential of ZIBs in energy storage technology. [ABSTRACT FROM AUTHOR]

Transition metal oxides/hydroxides exhibit reasonable oxygen activity in alkaline electrolytes and have been identified as potential electrocatalysts. Some highly active transition metal oxides or hydroxides can alter their surface chemistry in response to the electrolyte environment. This review presents the performance of some of the recently developed transition metal‐based oxides in electrocatalytic oxygen evolution reaction (OER). Despite the promising catalytic activity of many transition metals and their alloys due to their incompletely filled d orbitals, their low corrosion resistance in alkaline media barriers their use as electrocatalysts. Metallic glasses (MGs), with their disordered atomic structure, have many unique and exciting properties that cannot be found in crystalline metals. Metallic glasses′ unique chemical activity and corrosion resistance stem from their metastable and defective nature, as well as their structural and chemical homogeneity. In the case of Zr‐based MGs, the presence of MG−OHads and MG−Ox species on the surface for oxygen evolution enables rapid electron transfer to chemisorbed OH− with an "activated" MG surface leading to the generation of an amorphous Zr‐rich layer. Zr‐rich oxide layer formation favors the OER understood by decreased Tafel slope and highly stable nature during open circuit potential measurements in the alkaline solution. Unlike the as‐spun counterpart, the relatively small impedance magnitude and characteristic frequency for the post‐OER electrode corroborate the enhancement of oxygen evolution kinetics after electrochemistry. Compared with the early discovered electrodes, the MG‐oxide assembly outperforms many transition and precision metal‐based oxides and their composite forms regarding oxygen electroactivity and stability. [ABSTRACT FROM AUTHOR]

Thermal switches that switch the thermal conductivity (κ) of the active layers are attracting increasing attention as thermal management devices. For electrochemical thermal switches, several transition metal oxides (TMOs) are proposed as active layers. After electrochemical redox treatment, the crystal structure of the TMO is modulated, which results in the κ switching. However, the κ switching width is still small (<4 W m−1 K−1). In this study, it demonstrates that LaNiOx‐based solid‐state electrochemical thermal switches have a κ switching width of 4.3 W m−1 K−1. Fully oxidized LaNiO3 (on state) has a κ of 6.0 W m−1 K−1 due to the large contribution of electron thermal conductivity (κele, 3.1 W m−1 K−1). In contrast, reduced LaNiO2.72 (off state) has a κ of 1.7 W m−1 K−1 because the phonons are scattered by the oxygen vacancies. The LaNiOx‐based electrochemical thermal switch is cyclable of κ and the crystalline lattice of LaNiOx. This electrochemical thermal switch may be a promising platform for next‐generation devices such as thermal displays. [ABSTRACT FROM AUTHOR]

Discovering sources of transition metals, such as Ni, Co, and Mn, has become crucial due to their broad applicability, particularly as electrocatalysts for the oxygen evolution reaction (OER). Upcycled spent batteries have emerged as alternatives for transition metal sources for the OER electrocatalysts. In this work, Ni–Co–Mn oxalates were extracted from the spent LiNixCoyMnzO2 (NCM) cathode of lithium-ion batteries. The extracted oxalates were further processed via ball milling as a rapid and scalable mechanochemical route to engineer their structures. After calcination, Ni–Co–Mn oxides with nanosized granules on the surface that mainly consist of MnCo2O4 were obtained. With a correlation of morphology and trimetallic oxide formation with the OER catalytic performance, Ni–Co–Mn oxides exhibit OER overpotentials of 367 and 732 mV in alkaline and neutral media, respectively, showing OER catalytic activity in a wide pH range. The results indicate that ball milling can induce particle size reduction and bond formation between metals to facilitate mixed-metal oxide formation. Furthermore, the resulting material is also applicable as the catalyst in the air cathode of Zn-air batteries, where the battery achieved a power density of 85.42 mW cm–2 and 100 h of cycling stability, showing comparability with a battery with a Pt/C–Ir/C catalyst. [ABSTRACT FROM AUTHOR]

Transition metal oxide nanocomposites with heterostructures have gained a lot of attention for use in supercapacitors owing to their low cost, high surface area, fast transport of ions and electrons and high specific capacitance due to efficacious interplay between the electrode and the electrolytes. In this study, we fabricated tri-metallic Cu, Mn, Ni(CMNO), bi-metallic Mn, Ni(MNO) and mono-metallic Ni(NO) oxides through a facile hydrothermal route. All the fabricated materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDX), and their electrochemical properties were studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge (GCD). The CMNO material showed remarkable electrochemical performance with a specific capacitance of 790.63 F g−1 at a current density of 1 A g−1, surpassing the performance of MNO (438.4 F g−1) and NO (290.82 F g−1). Furthermore, CMNO showed high cycling stability with a retention of 96.7% specific capacitance after 8000 cycles. Based on remarkable and unique properties, the CMNO material is regarded as a promising material for new-generation pseudo-capacitor applications. [ABSTRACT FROM AUTHOR]

The development of green hydrogen generation technologies is increasingly crucial to meeting the growing energy demand for sustainable and environmentally acceptable resources. Many obstacles in the advancement of electrodes prevented water electrolysis, long thought to be an eco‐friendly method of producing hydrogen gas with no carbon emissions, from coming to fruition. Because of their great electrical conductivity, maximum supporting capacity, ease of modification in valence states, durability in hard environments, and high redox characteristics, transition metal oxides (TMOs) have recently captured a lot of interest as potential cathodes and anodes. Electrochemical water splitting is the subject of this investigation, namely the role of transition metal oxides as both active and supportive sites. It has suggested various approaches for the logical development of electrode materials based on TMOs. These include adjusting the electronic state, altering the surface structure to control its resistance to air and water, improving the flow of energy and matter, and ensuring the stability of the electrocatalyst in challenging conditions. In this comprehensive review, it has been covered the latest findings in electrocatalysis of the Oxygen Evolution Reaction (OER) and Hydrogen Evaluation Reaction (HER), as well as some of the specific difficulties, opportunities, and current research prospects in this field. [ABSTRACT FROM AUTHOR]

Developing efficient, low-cost and bifunctional catalysts with predominant durability for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is an extraordinary challenge in the preparation of green hydrogen energy by electrochemical water splitting. Three-dimensional (3D) transition metal compounds have become a research hotspot as OER electrocatalysts, which can replace noble metal oxides such as RuO 2 and IrO 2 to reduce application costs. Herein, we synthesized a novel three-dimensional pine-tree-like bimetallic sulfide arrays on nickel foam (FeCoS/NF) using various optimization strategies such as morphology optimization, in situ growth and introduction of heterogeneous structures. The as-synthesized FeCoS/NF electrocatalyst only requires relatively low overpotential of 156 mV to achieve a current density of 20 mA cm−2 for OER, with a Tafel slope of only 37 mV dec−1. It also has a small charge transfer resistance, an electrochemical surface area and good electrochemical stability in alkaline electrolytes. The excellent performance of FeCoS/NF can be attributed to the synergistic effect and amorphous phase of FeCoS as well as the well-defined pine-tree-like array architecture with a large surface area, abundant active sites, and sufficient gas and electrolyte diffusion channels. [Display omitted] • A 3D pine-tree-like structure of FeCoS/NF electrocatalyst was synthesized. • The FeCoS/NF exhibits excellent electrocatalytic activity for OER. • FeCoS/NF-based zinc-air battery shows an open-circuit voltage of 1.27 V. [ABSTRACT FROM AUTHOR]

Highlights: Oxygen-vacancy-rich SiC@MoO3 nanocomposite with strong reflection loss (− 50.49 dB at 1.27 mm thickness) and broadband absorption band (8.72 GHz at 2.68 mm thickness) were constructed via in situ etching strategy. The presence of oxygen vacancy leads to an increased conductive loss and defect-induced dipole polarization, which plays significant role in attenuating the incident electromagnetic wave. Defect engineering in transition metal oxides semiconductors (TMOs) is attracting considerable interest due to its potential to enhance conductivity by intentionally introducing defects that modulate the electronic structures of the materials. However, achieving a comprehensive understanding of the relationship between micro-structures and electromagnetic wave absorption capabilities remains elusive, posing a substantial challenge to the advancement of TMOs absorbers. The current research describes a process for the deposition of a MoO3 layer onto SiC nanowires, achieved via electro-deposition followed by high-temperature calcination. Subsequently, intentional creation of oxygen vacancies within the MoO3 layer was carried out, facilitating the precise adjustment of electromagnetic properties to enhance the microwave absorption performance of the material. Remarkably, the SiC@MO-t4 sample exhibited an excellent minimum reflection loss of − 50.49 dB at a matching thickness of 1.27 mm. Furthermore, the SiC@MO-t6 sample exhibited an effective absorption bandwidth of 8.72 GHz with a thickness of 2.81 mm, comprehensively covering the entire Ku band. These results not only highlight the pivotal role of defect engineering in the nuanced adjustment of electromagnetic properties but also provide valuable insight for the application of defect engineering methods in broadening the spectrum of electromagnetic wave absor ption effectiveness. SiC@MO-t samples with varying concentrations of oxygen vacancies were prepared through in-situ etching of the SiC@MoO3 nanocomposite. The presence of oxygen vacancies plays a crucial role in adjusting the band gap and local electron distribution, which in turn enhances conductivity loss and induced polarization loss capacity. This finding reveals a novel strategy for improving the absorption properties of electromagnetic waves through defect engineering. [ABSTRACT FROM AUTHOR]

The absence of adequate methods for hydrogen storage has prevented the implementation of hydrogen as a major source of energy. Graphene-based materials have been considered for use as solid hydrogen storage, because of graphene's high specific surface area. However, these materials alone do not meet the hydrogen storage standard of 6.5 wt.% set by the United States Department of Energy (DOE). They can, however, be easily modified through either decoration or doping to alter their chemical properties and increase their hydrogen storage capacity. This review is a compilation of various published reports on this topic and summarizes results from theoretical and experimental studies that explore the hydrogen storage properties of metal-modified graphene materials. The efficacy of alkali, alkaline earth metal, and transition metal decoration is examined. In addition, metal doping to further increase storage capacity is considered. Methods for hydrogen storage capacity measurements are later explained and the properties of an effective hydrogen storage material are summarized. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs) are important anode materials in sodium-ion batteries (SIBs) due to their high theoretical capacities, abundant resources, and cost-effectiveness. However, issues such as the low conductivity and large volume variation of TMO bulk materials during the cycling process result in poor electrochemical performance. Nanosizing and compositing with carbon materials are two effective strategies to overcome these issues. In this study, spherical MnFe2O4@xC nanocomposites composed of MnFe2O4 inner cores and tunable carbon shell thicknesses were successfully prepared and utilized as anode materials for SIBs. It was found that the property of the carbon shell plays a crucial role in tuning the electrochemical performance of MnFe2O4@xC nanocomposites and an appropriate carbon shell thickness (content) leads to the optimal battery performance. Thus, compared to MnFe2O4@1C and MnFe2O4@8C, MnFe2O4@4C nanocomposite exhibits optimal electrochemical performance by releasing a reversible specific capacity of around 308 mAh·g−1 at 0.1 A·g−1 with 93% capacity retention after 100 cycles, 250 mAh·g−1 at 1.0 A g−1 with 73% capacity retention after 300 cycles in a half cell, and around 111 mAh·g−1 at 1.0 C when coupled with a Na3V2(PO4)3 (NVP) cathode in a full SIB cell. [ABSTRACT FROM AUTHOR]

Carbon nitrides can form coordination compounds or metallic oxides in the presence of transition metals, depending on the reaction conditions. By adjusting the pH to basic levels for mild synthesis with metals, composites like g-C3N4-M(OH)x (where M represents metals) were obtained for nickel (II) and manganese (II), while copper (II) yielded coordination compounds such as Cu-g-C3N4. These materials underwent spectroscopic and electrochemical characterization, revealing their photocatalytic potential to generate superoxide anion radicals—a feature consistent across all metals. Notably, the copper coordination compound also produced significant hydroxyl radicals. Leveraging this catalytic advantage, with band gap energy in the visible region, all compounds were activated to disinfect E. coli bacteria, achieving total disinfection with Cu-g-C3N4. The textural properties influence the catalytic performance, with copper's stabilization as a coordination compound enabling more efficient activity compared to the other metals. Additionally, the determination of radicals generated under light in the presence of dicloxacillin supported the proposed mechanism and highlighted the potential for degrading organic molecules with this new material, alongside its disinfectant properties. [ABSTRACT FROM AUTHOR]

The detection of trimethylamine (TMA) is critically important due to its toxic and flammable nature, which poses significant risks to human health and the environment. However, achieving high response, rapid kinetics, selectivity, and low operating temperatures in TMA sensing remains challenging. In this study, WS2/WO3 nanohybrids with flower-like hierarchical structures were synthesized via an in situ sulfurization process, utilizing varying amounts of thioacetamide to control the sulfurization state of WO3. These novel hierarchical WS2/WO3 nanohybrids exhibit remarkable selectivity towards TMA, as well as rapid response and recovery characteristics. Specially, the optimal WS2/WO3 sensor, composed of 5% WS2/WO3 nanohybrids, demonstrates exceptional TMA sensing performance, including a high response (19.45 at 10 ppm), good repeatability, reliable long-term stability, and a low theoretical detection limit (15.96 ppb). The superior sensing capabilities of the WS2/WO3 nanohybrids are attributed to the formation of p-n heterojunctions at the interface, the unique hierarchical structures, and the catalytic activity of WS2. Overall, this work provides a straightforward and versatile approach for synthesizing multifunctional nanomaterials by combining metal oxide micro-flowers with transition metal dichalcogenide nanoflakes for applications in monitoring TMA in complex environments. [ABSTRACT FROM AUTHOR]

[Display omitted] Researchers are interested in single-atom catalysts with atomically scattered metals relishing the enhanced electrocatalytic activity for nitrogen reduction and 100 % metal atom utilization. In this paper, we investigated 18 transition metals (TM) spanning 3d to 5d series as efficient nitrogen reduction reaction (NRR) catalysts on defective 2D SiP V layered structures through first-principles calculation. A systematic screening identified Mo@SiP V , Nb@SiP V , Ta@SiP V and W@SiP V as superior, demonstrating enhanced ammonia synthesis with significantly lower limiting potentials (−0.25, −0.45, −0.49 and −0.15 V, respectively), compared to the benchmark −0.87 eV for the defective SiP. In addition, the descriptor Δ G *N was introduced to establish the relationship between the different NRR intermediates, and the volcano plot of the limiting potentials were determined for their potential-determining steps (PDS). Remarkably, the limiting voltage of the NRR possesses a good linear relationship with the active center TM atom Ɛ d , which is a reliable descriptor for predicting the limiting voltage. Furthermore, we verified the stability (using Ab Initio Molecular Dynamics − AIMD) and high selectivity (U L (NRR)- U L (HER) > -0.5 V) of these four catalysts in vacuum and solvent environments. This study systematically demonstrates the strong catalytic potential of 2D TM@SiP V (TM = Mo, Nb, Ta, W) single-atom catalysts for nitrogen reduction electrocatalysis. [ABSTRACT FROM AUTHOR]