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Lithiated transition metal oxides are the most important cathode materials for lithium‐ion batteries. Many efforts have been devoted in recent years to improving their energy density, stability, and safety, as demonstrated by thousands of publications. However, the commercialization of several promising materials is limited due to obstacles like stability limitations. To overcome the limitations of energetically high‐voltage or high‐capacity cathode materials, unconventional solutions for their surface engineering were suggested; among them, metal–organic frameworks (MOFs) and zeolites have been employed. MOFs possess favorable characteristics for stabilization goals, including manageable structures, topological control, high porosity, large surface area, and low density. This review article explores promising strategies for improving the electrochemical behavior of favorable cathode materials through surface modifications by using MOFs and zeolites. Investigating the potential of this frameworks‐based surface engineering for high energy density batteries' electrodes is essential for optimal control of their surface chemistry. It may be highly effective to upgrade the performance of high‐energy cathode materials, thus extending the practical use of very high energy density rechargeable batteries. [ABSTRACT FROM AUTHOR]

The electrocatalytic oxygen evolution reaction (OER) is an arduous step in water splitting due to its slow reaction rate and large overpotential. Herein, we synthesized glycerate-anion-intercalated nickel–iron glycerates (NiFeGs) using a one-step solvothermal reaction. We designed various NiFeGs by tuning the molar ratio between Ni and Fe to obtain Ni4Fe1G, Ni3Fe1G, Ni3Fe2G, and Ni1Fe1G, which we tested for their OER performance. We initially analyzed the catalytic performance of powder samples immobilized on glassy carbon electrodes using a binder. Ni3Fe2G outperformed the other NiFeG compositions, including NiFe layered double hydroxide (LDH). It exhibited an overpotential of 320 mV at a current density of 10 mA cm–2 in an electrolytic solution of pH 14. We then synthesized carbon paper (CP)-modified Ni3Fe2G as a self-supported electrode (Ni3Fe2G/CP), and it exhibited a high current density (100 mA cm−2) at a low overpotential of 300 mV. The redox peak analysis for the NiFeGs revealed that the initial step of the OER is the formation of γ-NiOOH, which was further confirmed by a post-Raman analysis. We extensively analyzed the catalyst's stability and lifetime, the nature of the active sites, and the role of the Fe content to enhance the OER performance. This work may provide the motivation to study metal-alkoxide-based efficient OER electrocatalysts that can be used for alkaline water electrolyzer applications. [ABSTRACT FROM AUTHOR]

The high concentration of antibiotics in aquatic environments is a serious environmental issue. In response, researchers have explored photocatalytic degradation as a potential solution. Through chemical vapor deposition (CVD), we synthesized copper selenide (β-Cu2−xSe) and found it an effective catalyst for degrading tetracycline hydrochloride (TC-HCl). The catalyst demonstrated an impressive degradation efficiency of approximately 98% and a reaction rate constant of 3.14 × 10−2 min−1. Its layered structure, which exposes reactive sites, contributes to excellent stability, interfacial charge transfer efficiency, and visible light absorption capacity. Our investigations confirmed that the principal active species produced by the catalyst comprises O2− radicals, which we verified through trapping experiments and electron paramagnetic resonance (EPR). We also verified the TC-HCl degradation mechanism using high-performance liquid chromatography–mass spectrometry (LC-MS). Our results provide valuable insights into developing the β-Cu2−xSe catalyst using CVD and its potential applications in environmental remediation. [ABSTRACT FROM AUTHOR]

Raman spectroscopy in transition metal dichalcogenides (TMDCs) helps determine their structural information and layer dependency. Because it is non‐destructive and fast, it is an archetypal spectroscopic technique to investigate the structure and defects in TMDCs. In our earlier study, we used a metal‐dielectric coating to enhance Raman signal of WS2 because the Raman Spectra measured from WS2 coated on the standard Si/SiO2 was significantly lower. This metal‐dielectric coating allowed access to the otherwise unavailable E12g and A1g modes of WS2. In this study, we compare the Raman spectra of WS2 on a Si/SiO2 to that of metal layers (Au [200 nm] and Al [200 nm]). A significant enhancement in the Raman signal of 2‐3L WS2 is observed for both the Au and Al coatings. Although 200 nm Au coating enhances the Raman Signal better than the 10 nm Au coating, it does not resolve the other signature vibrations other than E12g and A1g. Whereas, coating based on Al (200 nm) and Al (10 nm) both enhance the Raman signal of WS2. In the case of Al coating, we report well‐resolved vibrational modes such as the ones below <300 cm−1in a few layered WS2. This enhancement allows us to quantify the number of layers and also investigate the presence of defects. Photoluminescence measurements on 2–3L and 15L WS2 on Al (200 nm) confirm this. [ABSTRACT FROM AUTHOR]

Enormous potential loss and sluggish kinetics of the oxygen evolution reaction (OER) limit the practical implementation of water electrolyser systems. We attempt to address these technical challenges through the synthesis of cobalt-chromium-layered double hydroxide nanosheets (CoCr LDH) on oxidized-carbon nanotube (O-CNT) backbones as efficient OER electrocatalysts. Microscopic and elemental distribution analysis suggests that interconnected sheets of CoCr LDH masks over O-CNTs. We tested various compositions of the CoCr LDH_O-CNT hybrid (by varying the molar ratios of Co and Cr) along with the weight adjustment between CoCr LDH and O-CNTs to obtain an optimal OER activity. Due to the synergistic effect, the CoCr-LDH(3:1)_O-CNT (2:1) exhibits the lowest overpotential of 290 mV at 10 mA cm-2 with a corresponding smaller Tafel slope of 42 mV dec-1, which outperforms the other tested materials. The catalytically active site of Co2+ is boosted by Cr3+ as a charge transfer site owing to the spin-spin coupling between 3d7 of Co and 3d3 of Cr3+, which is evidenced by electron paramagnetic resonance results. Furthermore, the mildly oxidized carbon nanotubes offer the conducting channels to CoCr-LDH for faster charge transfer during OER. [ABSTRACT FROM AUTHOR]

We designed a heterostructure of Fe3S4@Ni3S2, as a potent oxygen evolution reaction (OER) electrocatalyst in an alkaline medium. Intriguingly, Fe3S4@Ni3S2 exhibits low onset potential of 290 mV and overpotential of 360 mV at a current density of 10 mA cm−2. We examined the OER kinetics of Fe3S4@Ni3S2 using distribution function of relaxation times (DFRT), which are attained with the help of impedance spectroscopy genetic programming (ISGP). ISGP reveals the occurrences of three events of OER, manifested as peaks in the DFRT, such as active material or pores (P2), charge transfer (P1'), and production rate of intermediates (P1) in case of Fe3S4@Ni3S2 at different faradic overpotentials. The effective resistance of each phenomenon can be easily calculated. It decreases with an increase in conductivity at high overpotentials for all the three, which suggests the high performance of the as‐synthesized composite due to faster kinetics. Further, structural investigation of the catalyst employing x‐ray photoelectron spectroscopy is elaborated and it is suggested that the catalyst activation takes place by the constant exchange of anions between electrode and electrolyte during electrochemical oxidation. [ABSTRACT FROM AUTHOR]

A novel electroless technique is employed for synthesizing Cu-YSZ cermet with discrete deposition of Cu onto 8 mol% yttria-stabilized zirconia (YSZ) and alloyed with 90 weight % Ni using electroless Ni-YSZ cermet by mechanical mixing and heat treatment under controlled atmosphere for the application as solid oxide fuel cell anode. X-ray diffractograms using Lorentzian fits revealed a shift of Ni-Cu (111) and Ni-Cu (200) peaks suggesting the solid solution of the bimetallic phases. Unique core-shell microstructures for both Cu-YSZ and Ni-Cu-YSZ with YSZ as core and Cu/Ni-Cu as shell are observed. EDAX analyses confirms 90:10 weight ratios (Ni:Cu) in the shell position for the alloy cermet. While only 23 vol% of metal content in Cu-YSZ gives electrical conductivity of 700 S cm −1 , a reasonably high value of 490 S cm −1 is obtained with 32 vol% of metal in Ni-Cu-YSZ. Electroless Ni-Cu-YSZ exhibits 98% efficiency towards methane reforming in simulated biogas environment and also shows significant tolerance to H 2 S (upto 25 ppm) in the input stream of the gas. [ABSTRACT FROM AUTHOR]

Recently, graphene and its derivatives have been extensively investigated for their interesting properties in many biomedical fields, including tissue engineering and regenerative medicine. Nonetheless, graphene oxide (GO) and reduced GO (rGO) are still under investigation for improving their dispersibility in aqueous solutions and their safety in different cell types. This work explores the interaction of GO and rGO with different polymeric dispersants, such as glycol chitosan (GC), propylene glycol alginate (PGA), and polydopamine (PDA), and their effects on human chondrocytes. GO was synthesized using Hummer's method, followed by a sonication-assisted liquid-phase exfoliation (LPE) process, drying, and thermal reduction to obtain rGO. The flakes of GO and rGO exhibited an average lateral size of 8.8 ± 4.6 and 18.3 ± 8.5 µm, respectively. Their dispersibility and colloidal stability were investigated in the presence of the polymeric surfactants, resulting in an improvement in the suspension stability in terms of average size and polydispersity index over 1 h, in particular for PDA. Furthermore, cytotoxic effects induced by coated and uncoated GO and rGO on human chondrocytes at different concentrations (12.5, 25, 50 and 100 µg/mL) were assessed through LDH assay. Results showed a concentration-dependent response, and the presence of PGA contributed to statistically decreasing the difference in the LDH activity with respect to the control. These results open the way to a potentially safer use of these nanomaterials in the fields of cartilage tissue engineering and regenerative medicine. [ABSTRACT FROM AUTHOR]

Transition-metal dichalcogenides (TMDCs) are unique layered materials with exotic properties. So, examining their structures holds tremendous importance. 2H-MoSe 2 (analogous to MoS 2 ; Gr. 6 TMDC) is a crucial optoelectronic material studied extensively using Raman spectroscopy. In this regard, low-frequency Raman (LFR) spectroscopy can probe this material's structure as it reveals distinct vibration modes. Here, we focus on understanding the microstructural evolution of different 2H-MoSe 2 morphologies and their layers using LFR scattering. We grew phase-pure 2H-MoSe 2 (with variable microstructures) directly on a Mo foil using a two-furnace ambient-pressure chemical vapor deposition (CVD) system by carefully controlling the process parameters. We analyzed the layers of exfoliated flakes after ultrasonication and drop-cast 2H-MoSe 2 of different layer thicknesses by choosing different concentrations of 2H-MoSe 2 solutions. Further detailed analyses of the respective LFR regions confirm the presence of newly identified Raman signals for the 2H-MoSe 2 nanosheets drop-cast on Raman-grade CaF 2 . Our results show that CaF 2 is an appropriate Raman-enhancing substrate compared to Si/SiO 2 as it presents new LFR modes of 2H-MoSe 2 . Therefore, CaF 2 substrates are a promising medium to characterize in detail other TMDCs using LFR spectroscopy., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

We report a facile and robust room-temperature NO 2 sensor fabricated using bi- and multi-layered 2H variant of tungsten di-selenide (2H-WSe 2 ) nanosheets, exhibiting high sensing characteristics. A simple liquid-assisted exfoliation of 2H-WSe 2 , prepared using ambient pressure chemical vapor deposition, allows smooth integration of these nanosheets on transducers. Three sensor batches are fabricated by modulating the total number of layers (L) obtained from the total number of droplets from a homogeneous 2H-WSe 2 dispersion, such as ∼2L, ∼5-6L, and ∼13-17L, respectively. The gas-sensing attributes of 2H-WSe 2 nanosheets are investigated thoroughly. Room temperature (RT) experiments show that these devices are specifically tailored for NO 2 detection. 2L WSe 2 nanosheets deliver the best rapid response compared to ∼5-6L or ∼13-17L. The response of 2L WSe 2 at RT is 250, 328, and 361% to 2, 4, and 6 ppm NO 2 , respectively. The sensor showed nearly the same response toward low NO 2 concentration even after 9 months of testing, confirming its remarkable long-term stability. A selectivity study, performed at three working temperatures (RT, 100, and 150 °C), shows high selectivity at 150 and 100 °C. Full selectivity toward NO 2 at RT confirms that 2H-WSe 2 nanosheet-based sensors are ideal candidates for NO 2 gas detection.

We report a facile two-furnace APCVD synthesis of 2H-WSe 2 . A systematic study of the process parameters is performed to show the formation of the phase-pure material. Extensive characterization of the bulk and exfoliated material confirm that 2H-WSe 2 is layered (i.e., 2D). X-ray diffraction (XRD) confirms the phase, while high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM) clarify the morphology of the material. Focused ion beam scanning electron microscopy (FIB-SEM) estimates the depth of the 2H-WSe 2 formed on W foil to be around 5-8 μm, and Raman/UV-vis measurements prove the quality of the exfoliated 2H-WSe 2 . Studies on the redox processes of lithium-ion batteries (LiBs) show an increase in capacity up to 500 cycles. On prolonged cycling, the discharge capacity up to the 50th cycle at 250 mA/g of the material shows a stable value of 550 mAh/g. These observations indicate that exfoliated 2H-WSe 2 has promising applications as an LiB electrode material., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)