As a contemporary and futuristic alternative to batteries, conventional supercapacitors (SCs) offer a potential candidate for renewable energy applications. Nevertheless, research present in this report focuses on the fabrication of high-performance quasi-solid-state supercapacitors (QSSCs) by hydrothermal means of nickel-doped MoS2 pompom-like nanostructures with varying nickel dopant concentrations (0, 1, 5, 10, and 20%). Optimal nickel concentrations are used to tune electrical conductivity, which affects electrochemical (EC) performance. With an excellent cycling stability of 77.83% after 5000 cycles, the 10% Ni-doped device presents an excellent specific capacitance of 156.8 mF cm(-2) at 4 mA cm(-2). The excellent EC properties of Ni-doped MoS2 pompom nanostructures allow them to be used as efficient electrode materials for SC applications and other related areas.

ZnO based piezoelectric nanogenerators (PENG) hold immense potential for harvesting ambient vibrational mechanical energy into electrical energy, offering sustainable solutions in the field of self-powered sensors, wearable electronics, human–machine interactions etc. In this study, we have developed flexible ZnO-based PENGs by incorporating ZnO microparticles into PDMS matrix, with ZnO concentration ranging from 5 to 25 wt%. Among these, the PENG containing 15 wt% ZnO exhibited the best performance with an open-circuit output voltage/short-circuit current of ~ 42.4 V/2.4 µA. To further enhance the output performance of PENG, p-type NiO was interfaced with ZnO in a bulk hetero-junction geometry. The concentration of NiO was varied from 5 to 20 wt% with respect to ZnO and incorporated into the PDMS matrix to fabricate the PENGs. The PENG containing 10 wt% NiO exhibits the best performance with an open-circuit output voltage/short-circuit current of ~ 65 V/4.1 µA under loading conditions of 30 N and 4 Hz. The PENG exhibiting the best performance demonstrates a maximum instantaneous output power density ~ 37.9 µW/cm2 across a load resistance of 20 MΩ under loading conditions of 30 N and 4 Hz, with a power density per unit force and Hertz of about ~ 0.32 µW/cm2·N·Hz. The enhanced output performance of the PENG is attributed to the reduction in free electron concentration, which suppresses the internal screening effect of the piezopotential. To assess the practical utility of the optimized PENG, we tested the powering capability by charging various commercial capacitors and used the stored energy to illuminate 10 LEDs and to power a stopwatch displays. This work not only presents a straightforward, cost-effective, and scalable technique for enhancing the output performance of ZnO-based PENGs but also sheds light on its underlying mechanism.

Wearable pH sensors for sweat analysis have garnered significant scientific attention for the detection of early signs of many physiological diseases. In this study, a MoS2-polyaniline (PANI) modified screen-printed carbon electrode (SPCE) is fabricated and used as a sweat biosensor. The exfoliated MoS2 nanosheets are drop casted over an SPCE and are functionalized by a conducting polymer, polyaniline (PANI) via the electropolymerization technique. The as-fabricated biosensor exhibits high super-Nernstian sensitivity of -70.4 +/- 1.7 mV pH(-1) in the linear range of pH 4 to 8 of 0.1 m standard phosphate buffer solution (PBS), with outstanding reproducibility. The sensor exhibits excellent selectivity against the common sweat ions including Na+, Cl-, K+, and NH4+ with tremendous long-term stability over 180 min from pH 4 to 6. The enhanced active surface area and better electrical conductivity as a consequence of the synergistic effect between MoS2 and PANI are correlated with the boosted performance of the as-produced biosensor. The feasibility of the sensor is further examined using an artificial sweat specimen and the successful detection confirms the potential of the biosensor for a real-time noninvasive, skin attachable, and flexible wearable pH sensor.

Hybrid nanostructures of quaternary composite of transition metal oxides (QCTMO) are fabricated by sputter depositing nano-dots of silver oxide or chromium oxide over flower-like nanostructures of manganese-cobaltcopper (MCC) ternary metal oxide. QCTMO electrodes are fabricated by magnetron assisted DC sputtering using different plasma powers. The presence of four different multivalent metal ions increases the redox sites, while the hybrid nature of the nanostructures increases the electrochemically active surface area. The synergistic effects result in enhancing the performance of the electrode. We showed that plasma power can be used to control the morphology and electrochemical properties of QCTMO electrodes. Chromium oxide nano-dots sputter deposited over MCC at 65 W showed the best performance with specific capacitance of 2261 F g-1 at a scan rate of 1 mV s-1 and specific capacity of 603 C g-1 at 5 mA cm-2. Solid-state symmetric supercapacitor fabricated with this electrode shows a retention in capacitance of 93 % after 4000 charge-discharge cycles and high energy density of 106 W h kg-1 at 3236.3 W kg-1 of power density.

Hybrid nanostructures of quaternary-composite metal oxide catalyst consisting of silver oxide nanodots over flower-like nanostructures of ternary metal oxide (MnCoCuOx) were synthesized by a hydrothermal method, followed by DC magnetron sputtering. Multimetal ions in spinel structures are efficient OER catalysts as they have large number of active sites, enhancing the electron transfer process. The sputter decorated silver oxide nanodots enhances the electrochemically active surface area (ECSA) of the electrode, which further enhances the OER performance. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spec-troscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), and Raman spectroscopy were used to validate the structure and composition of synthesized material. Oxygen evolution reaction (OER) activities of the synthesized catalysts were investigated by conducting linear scan voltammetry (LSV) at sweeping rate of 5 mV/s, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD). Quaternary-composite metal oxide catalysts were synthesized at various plasma powers, keeping other sputtering parameters fix. Silver oxide nanodots sputter decorated at 45 W over MnCoCuOx, showed the best catalytic properties for OER, having an overpotential of 83 mV via anodic scan and 110 mV via cathodic scan, Tafel slope of 65 mVdec-1, ECSA of 826 cm2, mass activity of 143.7 A g-1, and a turn over frequency (TOF) of 0.039 s-1. The symmetric device fabricated using the best performing electrode as cathode and anode displayed efficient water splitting activity, achieving a current density of 10 mA/cm2 at 1.37 V vs RHE, which is close to thermodynamic value of 1.23 V.

HYPOTHESIS:Fluidic micelles and reverse micelles have served as exfoliation mediums. However, an additional force, such as extended sonication, is required. Gelatinous cylindrical micelles that are formed once desired conditions are achieved can be an ideal medium for the quick exfoliation of 2D materials without the need for any external force. The quick formation of gelatinous cylindrical micelles can rip off layers from the 2D materials suspended in the mixture leading to the quick exfoliation of 2D materials.EXPERIMENTS:Herein, we introduce a quick universal method capable of delivering high-quality exfoliated 2D materials cost-effectively using CTAB-based gelatinous micelles as an exfoliation medium. The approach is devoid of harsh treatment, such as prolonged sonication and heating, and a quick exfoliation of 2D materials is completed using this approach.FINDINGS:We successfully exfoliated four 2D materials (MoS2, Graphene, WS2, and BN) and investigated their morphology, chemical, and crystal structure along with optical and electrochemical properties to probe the quality of the exfoliated product. Results revealed that the proposed method is highly efficient in exfoliating 2D materials in a quick time without causing any significant damage to the mechanical integrity of the exfoliated materials.

The advancement of renewable energy technologies like water electrolysis and hydrogen fuel cells relies on the fabrication of effective and reliable catalysts for the hydrogen evolution process (HER). In this regard, we report gold nanoparticles embedded in laser-induced graphene electrodes for regulation of overpotential and electrocatalytic performance of hydrogen evolution reaction. Gold nanoparticles were deposited onto the LIG surface using electrode deposition via cyclic voltammetry (CV) at different cycle lengths. The catalyst fabrication technique enables the manipulation of many electrochemical parameters, such as overpotential value, charge transfer resistance, electrochemical active surface area, and tafel slope, through the adjustment of cyclic voltammetry (CV) cycles. The LIG-Au@50 sample demonstrates remarkable electrocatalytic characteristics, as evidenced by its low overpotential of 141 mV at a current density of 10 mA/cm2 and reduced tafel slope of 131 mV/decade in an acidic environment. Furthermore, the presence of an augmented electrochemical active surface area, a mass activity of 8.80 A/g, and a high turnover frequency of 0.0091 s−1 suggest elevated and significant accessibility to plentiful active sites. A significant decrease in charge transfer resistance resulted in an enhanced rate of the water-splitting reaction.

Since the discovery of triboelectric nanogenerators (TENGs), a significant body of research work has been undertaken for the modification of material properties to enhance their efficiency. These efforts have focused on judicious materials choice (large differences in work functions), enhanced charge-exchange density via hybridization (plasmonic, photo-enhancement, piezoelectric effect), enhanced contact area via nanostructuring and new device architectures. Whilst these efforts have led to a significant increase in the power density, but the rudimentary choice of metal electrode selection and subsequent charge transfer mechanism still demand attention. As such, low-dimensional carbon nanomaterials and in particular, graphene and its derivatives have been explored in the literature to overcome some of the drawbacks of the conventional metallic electrodes including fatigue and corrosion, especially in high humidity environments. Graphene with its exceptionally high surface area, high electrical conductivity and flexibility make itself an excellent material for enabling wearable electronics. In this review, we discuss the impact of graphene, graphene-based composite electrodes, doped graphene electrodes and laser-induced graphene (LIG) electrodes to improve the performance of TENGs. Also, the basic mechanism of charge transfer between different electrodes of the TENG device has been explained. Among all graphene-based electrodes for TENG, laser-induced graphene electrodes show excellent performance owing to output power density 240 times higher than that of pristine graphene and 120 times more than graphene-based composite electrodes. Such use of functionalized graphene electrodes establishes the new steps towards the realization of flexible and transparent triboelectric nanogenerators.