We review emerging trends and the state-of-the-art in 2D transition metal phosphorus chalcogenides (MPX3, X = S, Se), including their emergent applications, physicochemical properties and growth methodologies, and a perspective on future directions.

Room-temperature stabilization of metastable β-NiMoO is achieved through urea-assisted hydrothermal synthesis technique. Structural and morphological studies provided significant insights for the metastable phase. Furthermore, detailed electrochemical investigations showcased its activity toward energy storage and conversion, yielding intriguing results. Comparison with the stable polymorph, α-NiMoO, has also been borne out to support the enhanced electrochemical activities of the as-obtained β-NiMoO. A specific capacitance of ∼4188 F g (at a current density of 5 A g) has been observed showing its exceptional faradic capacitance. We qualitatively and extensively demonstrate through the analysis of density of states (DOS) obtained from first-principles calculations that, enhanced DOS near top of the valence band and empty 4d orbital of Mo near Fermi level make β-NiMoO better energy storage and conversion material compared to α-NiMoO. Likewise, from the oxygen evolution reaction experiment, it is found that the state of art current density of 10 mA cm is achieved at overpotential of 300 mV, which is much lower than that of IrO/C. First-principles calculations also confirm a lower overpotential of 350 mV for β-NiMoO

The research interest in wearable sensors has tremendously increased in recent years. Amid the different biosensors, electrochemical biosensors are unparalleled and ideal for the design and manufacture of such flexible and wearable sensors because of their various benefits, including convenient operation, quick response, portability, and inherent miniaturization. A number of studies on flexible and wearable electrochemical biosensors have been reported in recent years for invasive/non-invasive and real-time monitoring of biologically relevant molecules such as glucose, lactate, dopamine, cortisol, and antigens. To attain this, novel two-dimensional nanomaterials and their hybrids, various substrates, and detection methods have been explored to fabricate flexible conductive platforms that can be used to develop flexible electrochemical biosensors. In particular, there are many advantages associated with the advent of two-dimensional materials, such as light weight, high stretchability, high performance, and excellent biocompatibility, which offer new opportunities to improve the performance of wearable electrochemical sensors. Therefore, it is urgently required to study wearable/flexible electrochemical biosensors based on two-dimensional nanomaterials for health care monitoring and clinical analysis. In this review, we described recently reported flexible electrochemical biosensors based on two-dimensional nanomaterials. We classified them into specific groups, including enzymatic/non-enzymatic biosensors and affinity biosensors (immunosensors), recent developments in flexible electrochemical immunosensors based on polymer and plastic substrates to monitor biologically relevant molecules. This review will discuss perspectives on flexible electrochemical biosensors based on two-dimensional materials for the clinical analysis and wearable biosensing devices, as well as the limitations and prospects of the these electrochemical flexible/wearable biosensors. Graphical abstract

Applying first principles electronic structure calculations and molecular dynamics (MD) simulations we have studied the structural stability, hydrogen adsorption capability and hydrogen desorption kinetics of Y-decorated single walled carbon nanotube (SWCNT). We have predicted that a single Y atom attached on SWCNT can physisorb up to six hydrogen molecules which is not reported so far. Our MD simulations with four Y atoms placed at the alternate hexagons of SWCNT showed no clustering effect of Y atoms at room temperature and also we found that the system is stable even at higher temperature (700 K). For the first time we showed that 100% desorption at comparatively lower temperature can be achieved in a transition metal-decorated SWCNT system. Therefore the Y-decorated SWCNT has the potential to become a promising hydrogen storage device.

The present work explores the electrochemical energy storage performance of Ti3C2T x (MXene) and 1T-VS2 nanosheet hybrids synthesized by a simple in situ hydrothermal method. Different analytical methods such as X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared, Raman spectroscopy, and Brunauer–Emmett–Teller were employed to explore the structural and morphological properties and composition of electrode materials. Furthermore, the electrochemical characterization of 1T-VS2/MXene hybrid electrode materials with different concentrations of MXene was investigated systematically. The all pseudocapacitive asymmetric supercapacitor cell was fabricated by combining the best performing 1T-VS2/MXene and MXene, which displayed the highest specific capacitance of 115.7 F/g at a current density of 0.8 A/g in an expanded potential range of 1.6 V. Additionally, the highest energy density achieved was 41.13 W h kg–1 at a maximum power density of 793.50 W kg–1. The asymmetric supercapacitor was able to achieve a high capacitance retention of 85% and a coulombic efficiency of 100% after 5000 galvanostatic charge–discharge cycles. Moreover, the synergistic effect and charge storage kinetics of the 1T-VS2/MXene hybrid pseudocapacitive electrode material were investigated in detail using experimental and density functional theory calculations. Based on the results, we have further demonstrated the usage of 1T-VS2/MXene and MXene as a high-performance energy storage material for supercapacitor application with the dominating intercalation mechanism. The lower diffusion energy barrier for electrolytic ions in the case of hybrid 1T-VS2/MXene supports the higher charge storage. The enhanced density of states and lower diffusion barrier justify the superior charge storage performance for hybrid 1T-VS2/MXene.

This work explored a promising supercapacitor electrode material (WO 3 -rGO hybrids) synthesized via a simplistic one-pot hydrothermal synthesis route. Various analytical studies (X-ray diffraction study, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer−Emmett−Teller analysis) were employed in furtherance to explore the structural, morphological, compositional, and surface areal properties of the prepared materials. The enhancement in electrochemical supercapacitive properties were evaluated from pure hexagonal phase WO 3 to the various hybrids, depending on the concentration of GO introduced into it, using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The WG-80 composite revealed the high rise in capacitance value of 801.6 F/g overcoming the individual capacitance of rGO (71.11 F/g) and WO 3 (94.22 F/g) at a current density of 4 A/g with good cycling stability (75.7%) over 5000 cycles. We have presented quantum capacitance from ab initio calculations and provided theoretical explanation from the orbital interactions.

Supercapacitors are widely accepted as one of the energy storage devices in the realm of the sustainable and renewable energy storage world. Supercapacitors emerge as good alternate for traditional capacitors...

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