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The gravest oxidation of MXenes has become a critical problem due to the formation of metal oxides, leading to the loss of their intrinsic properties. Herein, bimetallic cobalt–manganese organic framework (CMT) directly grown on a Ti3C2Tx MXene sheet via solvothermal treatment to obtain strong oxidation resistance in an open structured application and to enhance electrocatalytic properties for oxygen evolution and reduction reaction is reported. Inspired by ligand chemistry, the carboxyl acids in tetrakis(4–carboxyphenyl)porphyrin acting as an organic linker are grafted with the surface terminators of Ti3C2Tx MXene through the Fischer esterification and substitution reaction of fluorine, thereby greatly enhancing the antioxidation stability. Furthermore, the as‐formed metalloporphyrin structure and unpaired electrons, produced between CMT and Ti3C2Tx MXene during solvothermal treatment, improve their electrocatalytic activity, durability, and electrical conductivity through an electron hopping mechanism. Consequently, the CMT@MXene demonstrates high stability as a bifunctional electrocatalyst at a fixed specific capacity of 1000 mAh g−1 and a current density of 500 mA g−1 for 247 cycles in lithium–oxygen (LiO2) battery. This approach suggests new strategies for the synergistic coupling of MXenes and MOFs for future open structured applications. [ABSTRACT FROM AUTHOR]

The shuttling effect of lithium polysulfide (LiPS), which leads to the gravest capacity degradation, is one of the critical problems to hindering the commercialization of lithium–sulfur batteries (LSBs). Here, collectively exhaustive Ti3C2Tx MXene and graphene oxide (GO) multilayers are reported to suppress the shuttling effect by utilizing both physical inhibition of micro/mesoporous and chemical absorption of surface functional groups. The abundant surface functional groups of GO and MXene attract the positively charged lithium ion (Li+) and eject the negatively charged polysulfides (Sn2–) through electrostatic affinity and repulsion. A simple approach using vacuum filtration is utilized to encapsulate elemental sulfur (S8) between GO and MXene film (GSM), acting as a permselective separator and functionalized current collector, respectively. The functionally antagonistic GSM directly plays a role in a cathode for LSBs and exhibits a specific capacity of 1425 mAh g–1 at 0.1C in the initial cycle. The abundant functional groups, which can chemisorb the LiPSs, result in a high cyclic retention of ≈85.1% after 500 cycles. Furthermore, a flexible LSB is demonstrated with a PEO‐LiTFSI electrolyte based on the flexibility of the exceptionally thin GSM due to the 2D nanomaterials, MXene and graphene oxide. [ABSTRACT FROM AUTHOR]

Preparation of semiconductor nanomaterials with controlled morphology and uniform porous surface is of great interest for enhanced photocatalytic applications. In the work presented herein, uniform sphere-like niobium pentoxide (Nb2O5) nanostructures were synthesized by a one-pot solvothermal method using ammonium niobate oxalate and octadecylamine as precursor and surfactant, respectively. The synthesized Nb2O5 nanostructures were then employed as photocatalyst for degradation of methylene blue (MB) and rose bengal (RB) dyes under ultraviolet (UV) light. It was found that the prepared Nb2O5 nanostructures could degrade up to 87 % and 62 % of MB and RB dye after irradiation for 90 and 180 min, respectively. [ABSTRACT FROM AUTHOR]

Recently, considerable attention has been paid to the exfoliation of 2D inorganic layered materials as their physicochemical properties are significantly different from the bulk. However, the exfoliated 2D nanosheets readily undergo restacking and form a bulk-like structure due to van der Waals forces. Therefore, functionalization or decoration with foreign materials on the 2D nanosheets has been suggested to prevent the extent of restacking and tune their band gaps for emerging applications. Here, for the first time, we demonstrate the decoration of cube-shaped α-Fe2O3 nanoparticles on exfoliated h-BN nanosheets using a solvothermal method. Remarkably, the growth of the α-Fe2O3 particles was suppressed by the h-BN nanosheets, which resulted in the formation of a controlled size of the α-Fe2O3 nanoparticles over the exfoliated BN nanosheets. However, an increased lateral size was observed in the bare α-Fe2O3 nanoparticle synthesis. Then, the synergistic interaction between the α-Fe2O3 nanoparticles and the exfoliated BN nanosheets was identified by FT-IR analysis. XRD and Raman analysis further confirms the in situ formation of the phase pure α-Fe2O3 nanoparticles on the exfoliated BN nanosheets. The distribution of cube-shaped α-Fe2O3 nanoparticles over exfoliated BN nanosheets was characterized by SEM and HR-TEM analysis. [ABSTRACT FROM AUTHOR]

Fabrication of highly crystalline BN-MoS2 heterostructure with >95% yield was demonstrated using one-pot supercritical fluid processing within 30 min. The existence of 20-50 layers of BN-MoS2 in the prepared heterostructure was confirmed by AFM analysis. The HR-TEM imaging and mapping analysis revealed the well-melded BN and MoS2 nanosheets in the heterostructure. The drastic reduction in XRD line intensities corresponding to the (002) plane and broadening of the peaks for the BN system over MoS2 indicated the effective exfoliation and lateral size reduction in BN nanosheets during SCF processing. Also, the exfoliated MoS2 nanosheets are preferentially exposed rather than BN nanosheets; consequently, the MoS2 nanosheets sturdily covered BN nanosheets in the heterostructure. The exfoliated BN and MoS2 nanosheets with nanoscale roughness make the surface highly hydrophobic in nature. As a result, the BN-MoS2 heterostructure showed superior superhydrophobic performance with high water contact angle of 165.9°, which is much higher than the value reported in the literature. [ABSTRACT FROM AUTHOR]

We demonstrate electrochemical cycling-induced reduction of MoO3 to monoclinic molybdenum dioxide and molybdenum sub-oxides (MoO3−x), which exhibit excellent electrochemical hydrogen evolution reaction (HER) activity. The conversion of MoO3 during cycling was probed; after 250 cycles, the redox peaks were found to diminish with an onset potential shift and increased HER current density. At 400 cycles, the insertion/deinsertion processes observed in the initial cycles are completely absent and the HER current density is enhanced to the maximum. The effect of MoO3 morphology and size on the electrochemical reduction of MoO3 was also studied. [ABSTRACT FROM AUTHOR]

For the first time, we present a simple, rapid and one-pot exfoliation of layered bulk MoS2 into luminescent MoS2 nanoscrolls by supercritical fluid processing using dimethyl formamide as a solvent and with a short reaction time of 30 min. The exfoliated nanoscrolls were characterized using PXRD, UV-visible, Raman, FE-SEM and TEM. The MoS2 nanoscrolls exhibit photoluminescence over the emission wavelength ranges from 420 to 600 nm, which is attributed to the size reduction and polydisperse nature. [ABSTRACT FROM AUTHOR]

In this work, an organic-inorganic hybrid crystal, violet-crystal (VC), was used to etch the nickel foam (NF) to fabricate a self-standing electrode for the water oxidation reaction. The efficacy of VC-assisted etching manifests the promising electrochemical performance towards the oxygen evolution reaction (OER), requiring only ~356 and ~376 mV overpotentials to reach 50 and 100 mA cm -2 , respectively. The OER activity improvement is attributed to the collectively exhaustive effects arising from the incorporation of various elements in the NF, and the enhancement of active site density. Furthermore, the self-standing electrode is robust, exhibiting a stable OER activity after 4,000 cyclic voltammetry cycles, and ~50 h. The anodic transfer coefficients (α a ) show that the first electron transfer step is the rate-determining step on the surface of NF-VCs-1.0 (NF etched by 1 g of VCs) electrode, while the chemical step involving dissociation following the first electron transfer step is identified as the rate-limiting step in other electrodes. The lowest Tafel slope value observed in the NF-VCs-1.0 electrode indicates the high surface coverage of oxygen intermediates and more favorable OER reaction kinetics, as confirmed by high interfacial chemical capacitance and low charge transport/interfacial resistance. This work demonstrates the importance of VCs-assisted etching of NF to activate the OER, and the ability to predict reaction kinetics and rate-limiting step based on α a values, which will open new avenues to identify advanced electrocatalysts for the water oxidation reaction., (© 2023 Wiley-VCH GmbH.)

Fabrication of highly crystalline BN-MoS 2 heterostructure with >95% yield was demonstrated using one-pot supercritical fluid processing within 30 min. The existence of 20-50 layers of BN-MoS 2 in the prepared heterostructure was confirmed by AFM analysis. The HR-TEM imaging and mapping analysis revealed the well-melded BN and MoS 2 nanosheets in the heterostructure. The drastic reduction in XRD line intensities corresponding to the (002) plane and broadening of the peaks for the BN system over MoS 2 indicated the effective exfoliation and lateral size reduction in BN nanosheets during SCF processing. Also, the exfoliated MoS 2 nanosheets are preferentially exposed rather than BN nanosheets; consequently, the MoS 2 nanosheets sturdily covered BN nanosheets in the heterostructure. The exfoliated BN and MoS 2 nanosheets with nanoscale roughness make the surface highly hydrophobic in nature. As a result, the BN-MoS 2 heterostructure showed superior superhydrophobic performance with high water contact angle of 165.9°, which is much higher than the value reported in the literature.

We demonstrate electrochemical cycling-induced reduction of MoO 3 to monoclinic molybdenum dioxide and molybdenum sub-oxides (MoO 3-x ), which exhibit excellent electrochemical hydrogen evolution reaction (HER) activity. The conversion of MoO 3 during cycling was probed; after 250 cycles, the redox peaks were found to diminish with an onset potential shift and increased HER current density. At 400 cycles, the insertion/deinsertion processes observed in the initial cycles are completely absent and the HER current density is enhanced to the maximum. The effect of MoO 3 morphology and size on the electrochemical reduction of MoO 3 was also studied.