CsPbI3-PVDF Composite-Based Multimode Hybrid Piezo-Triboelectric Nanogenerator: Self-Powered Moisture Monitoring System.

For several decades, the development of potential flexible electronics, such as electronic skin, wearable technology, environmental monitoring systems, and the internet of Things network, has been emphasized. In this context, piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs) are highly regarded due to their simple design, high output performance, and cost-effectiveness. On a smaller scale, self-powered sensor research and development based on piezo-triboelectric hybrid nanogenerators have lately become more popular. When a material in the TENG is a piezoelectric material, these two distinct effects can be coupled. Herein, we developed a multimode hybrid piezo-triboelectric nanogenerator using the CsPbI3-PVDF composite. The addition of CsPbI3 to PVDF significantly enhances its electroactive phase and dielectric property, thereby enhancing its surface charge density. 5 wt % CsPbI3 incorporation in poly(vinylidene difluoride) (PVDF) results in a high electroactive phase (FEA) value of >90%. Moreover, CsPbI3-PVDF composite-based PENGs were fabricated in three modes, viz., nanogenerators in contact-separation mode (TECS), single electrode mode (TESE), and sliding mode (TES), and the output performance of all the devices was investigated. The fabricated TECS, TESE, and TES reveal peak output powers of 3.08, 1.29, and 0.15 mW at an external load of 5.6 MΩ. Through analysis of the contact angle measurement and experimental quantification, the hydrophilicity of the composite film has been identified. The hydrophobicity and moisture absorption capacity of CsPbI3-PVDF film make it an attractive option for self-powered humidity monitoring. The TENGs effectively powered several low-powered electronic devices with just a few human finger taps. This study offers a high-performance PTENG device that is reliant on ambient humidity, which is a helpful step toward creating a self-powered sensor.

Highly exfoliated graphitic carbon nitride for efficient removal of wastewater pollutants: Insights from DFT and statistical modelling.

The present work entails the synthesis of thermally modified graphitic carbon nitride (GCN) using a two-step thermal treatment procedure and its subsequent use in the photocatalytic reduction of toxic pollutants such as rhodamine B dye (RhB) and chromium (VI) (Cr(VI)) from aquatic environments. The as-synthesised exfoliated GCN (GCNX) is characterised by X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller analysis (BET), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). These characterisations helped to elucidate the phase formation, chemical structure, composition, surface area, optical properties, and morphology of the sample. With assistance from a visible light source, GCNX can degrade RhB dye within 30 min in the presence of hydrogen peroxide (H2O2) and reduce Cr(VI) to Cr(III) in under 2 h in the presence of formic acid (FA/HCOOH). Variations in different catalytic parameters, including catalyst amount, pH of the solution, initial RhB or Cr(VI) concentration, and variation in H2O2 or FA concentration, are performed to inspect their effects on the photodegradation activity of GCNX. Moreover, the GCNX catalyst exhibits impressive stability and reusability. A thorough statistical evaluation follows the response surface methodology to understand the complex interaction between the factors contributing to the catalytic activity. The band alignment of differently functionalised GCN blocks in their pristine form and their H2O2/FA-adsorbed states is investigated using first-principles calculations to provide a further understanding of the RhB and Cr(VI) reduction mechanisms. The modified GCN can thus be effectively employed as a low-cost material for removing contamination from aquatic environments.

Significant enhancement of lattice thermal conductivity of monolayer AlN under bi-axial strain: a first principles study.

Using rigorous ab initio calculations within the framework of phonon Boltzmann transport theory, we have carried out a detailed investigation to probe the effects of uniform bi-axial strain and finite size on the lattice thermal conductivity (κ) of monolayer AlN. We show that implementation of bi-axial tensile strain can shoot up the value of κ of monolayer AlN by a large amount unlike in the case of analogous 2D materials. The value of κ for monolayer AlN is calculated to be 306.5 W m-1 K-1 at room temperature (300 K). The value of κ can be raised by one order of magnitude to up to 1500.9 W m-1 K-1 at 300 K by applying a bi-axial strain of about 5%. A similar trend persists when the finite size effect is incorporated in the calculation. As the sample size is varied from 10 nm to 10 000 nm along with increasing tensile strain, a huge variation of κ (from 20.7 W m-1 K-1 to 558.9 W m-1 K-1) is observed. Our study reveals that the major part of the lattice thermal conductivity of monolayer AlN comes from the contribution of the flexural acoustic (ZA) phonon modes. The anomalous trend of drastic increment in the value of κ with tensile strain is found to be a direct effect of interaction between nitrogen lone-pair electrons and bonding electrons in the ionic lattice which results in the reduction of phonon anharmonicity with increasing tensile strain. Our study provides a detailed analysis of the strain modulated and size-tuned thermal transport properties of monolayer AlN revealing that it is an impactful 2D material to be used in thermal management devices.

Mechanism of Oxygen Reduction Reaction in Alkaline Medium on Nitrogen-Doped Graphyne and Graphdiyne Families: A First Principles Study.

Using extensive first principles protocols, a systematic investigation is performed to probe the oxygen reduction reaction (ORR) mechanism on nitrogen (N) doped graphynes (Gys, e. g. αGy, ßGy, γGy and 6,6,12Gy) and graphdiyne (Gdy) in alkaline medium. We considered both associative and dissociative pathways, as well as two distinct intermediate forks for each of them depending on the first protonation site(s). Following the dissociative approach, the activation energy to form an O2 dissociated configuration is found as a function of the distances migrated by the O atoms over the catalyst surface and the amount of charge transferred from the C atoms linked to N. N doped αGy and 6,6,12Gy emerged as the best electrocatalyst comparing both pathways having lowest overpotentials of 0.88 and 0.82 V, respectively. The rate-limiting steps for the two different intermediate routes are observed to be dependent on the first protonation site(s) and related to the desorption of the OH radical from the sp hybridized C atom site(s) linked to N. Hence, the OH adsorption energy is identified as a descriptor for the efficiency of the ORR for the considered systems. The stabilities of the ORR intermediates are further elaborated in terms of pH and electrode potential.

CsPbBrCl2/g-C3N4 type II heterojunction as efficient visible range photocatalyst.

Photocatalytic activity of low band gap semiconductor largely restrained by high recombination rate of photogenerated charge carriers. To enhance the catalytic performance numerous protocols were adopted amongst which designing of novel hybrid via coupling of semiconductors are very intriguing from modest application point of view. Here, we report facile realization of type II heterojunctions embracing polymeric graphitic carbon nitride (g-C3N4/GCN) and all-inorganic cesium lead halide perovskite (CsPbBrCl2) for degradation complex organic effluents under visible-light illumination. Synthesized hybrid presented much improved performance in toxic cationic and anionic dyes degradation as compared to individual building units. Signature of favorable staggered gap junction's formation at interface was confirmed via Mott-Schottky analysis. Such kind of junctions delay the recombination of photogenerated electron holes and facilitates active radical generation at catalyst surface thereby ensures improved photocatalytic performance. Charge transfer process in heterojunction further illustrated via Density functional theory (DFT) based calculations. Several scavenger tests have been performed to examine the impact of different active radicals in the photocatalysis which suggests manifold performance improvement in the presence of very small concentrations of EDTA. A plausible photocatalytic mechanism in accordance with the type II junction has been proposed.

Band edge tuned ZnxCd1-xS solid solution nanopowders for efficient solar photocatalysis.

This work highlights the synthesis of zinc blende ZnxCd1-xS ternary solid solutions with a tunable bandgap. Composition dependent band gaps are realized due to the effective band edge tuning of the solid solutions which in turn show decent photocatalytic behaviour. The bandgap of ZnxCd1-xS increases as Zn composition increases. It is interesting to note that the highest catalytic activity is observed for Zn0.8Cd0.2S (Eg = 2.83 eV) in the visible spectra due to the presence of defect states in the bandgap around 2.35 eV which has been explicated according to the results of photoluminescence spectra. Density of states (DOS) analysis provides further theoretical insight into the more negative conduction band edge for x = 0.8 than other samples. It also determines generation of intermediate states due to sulfur vacancy which is responsible for more electron-hole generation and the highest rate of Methyl Orange (MO) degradation under natural sunlight irradiation.

Perovskites beyond photovoltaics: field emission from morphology-tailored nanostructured methylammonium lead triiodide.

Herein, methylammonium lead triiodide (CH3NH3PbI3) nanorods and nanocrystals were prepared by a facile room-temperature wet chemical method via simple variation of the synthesis parameters. Proper phase formation was confirmed by X-ray diffraction studies, whereas the morphological features were investigated using field emission scanning electron microscopy and transmission electron microscopy. The bonding information and the presence of organic functional groups within the synthesized nanostructures were confirmed using Fourier transform infrared spectroscopy. The work function of the material was calculated using first principles studies. In an attempt to explore the potential of the perovskites beyond photovoltaic applications, the field emission performance of the nanostructured CH3NH3PbI3 was investigated. The turn-on field (electric field corresponding to a 10 µA cm-2 current density) was obtained as 4.2 V µm-1 with the current density reaching up to 96 µA cm-2 for an inter-electrode spacing of 200 µm for the nanorod samples. The emission current stability was tested to be good enough for as long as 2 hours. Finally, finite element-based simulations were performed using ANSYS to obtain a theoretical perception of our experimental findings.

Implications of boron doping on electrocatalytic activities of graphyne and graphdiyne families: a first principles study.

Dispersive force corrected density functional theory is used to map the oxygen reduction reaction (ORR) kinetics of six kinds of graphyne (Gy) and graphdiyne (Gdy) systems (namely αGy, ßGy, γGy, δGy, 6,6,12Gy, RGy and Gdy) with substitutional boron (B) atom doping. To this end, the most favorable sites for B doping of each structures are determined by comparing their formation energies and then the best configuration for di-oxygen (O2) adsorption is computed by analyzing the corresponding adsorption energies. Even though oxygen adsorption is found to be energetically favorable on all of these and all Gys and Gdy are found to distinctly favor the four electron pathways for ORR, a reaction scheme with monotonically exothermic ΔG is observed only for B doped RGy. Further computations performed by varying electrode potential indicated this monotonically exothermic nature of the ΔG of B doped RGy to persist in the range 0-0.22 V and also indicated the first (H(+) + e) transfer step to be the rate limiting step.