Ambient particulate matter air pollution has become a serious environmental issue and poses grave threats to public health globally. The indoor and outdoor air protection could be achieved by ...filtering devices and facial masks. The development of air filter to eliminate particulate matter pollution from the air is necessary for human safety. To realize this, here a class of nanofiber air filter is reported with high efficiency and very low pressure drop. By controlling the surface chemistry through cetyltrimethylammonium bromide, it is achieved a >99.9% removal efficiency under extreme hazardous air-quality conditions for PM2.5 with quality factor of 0.469 Pa–1 and low ∼11 Pa pressure drop. The dipole moment and intermolecular interaction between the nanofibers and PM2.5 are investigated by density functional theory calculations. A long-term 15 day filtration test has proven that the nanofiber air filter maintains an excellent efficiency of 99%. This work pushes forward a significant step toward the design and development of high efficiency and a very low pressure drop air filter for various applications.
Summary
Using first‐principles calculations, we investigate a family of doped graphene nanoribbons (GNRs) for their suitability as cathode hosts in lithium‐sulfur batteries. We probe the role played ...by the lone pairs of the dopants in confining the lithium polysulfides (LiPS) to understand the mechanism of binding. Our results show that the Li bond between the polysulfides and the doped GNRs is analogous to a hydrogen bond and also dipole‐dipole interactions play a key role in anchoring the polysulfides. A critical donor‐Li‐acceptor angle of 180° is found to be essential for proper adsorption of LiPS, highlighting the importance of the directionality of lone pairs. The charge lost by the sulfur atom of the polysulfide upon adsorption and shape of the lone pair basins and the value of Electron Localization Function (ELF) at the dopant position can provide a quick estimate of the strength of the bond. Significant contractions in the ELF profiles are also observed upon Li2S adsorption, further providing evidence for the hydrogen bond‐like nature of the Li bond. Our results corroborate the fact that all acceptors capable of forming hydrogen bonds can be employed as suitable dopants for carbon‐based cathode hosts in Li‐S batteries.
The lithium bond between the lithium polysulfides and doped GNRs is found to be analogous to a hydrogen bond with unique directional properties. Shape of the lone pair basins and value of Electron localization function at the position of dopant are identified to reveal the adsorption strength. Employing good hydrogen bond acceptors as suitable dopants for graphene‐based cathode hosts is a promising strategy in the design of lithium sulfur batteries.
The development of two-dimensional (2D) material or heterostructure as an anode material is necessary to enhance the electrochemical performance of Li-ion batteries (LIBs) but finding the correct ...combination is a challenge. In the present work, using First principles study, we have proposed borophosphene (BP-ML) and graphene-based multilayer heterostructure as a possible anode material. We have found that BP-ML and graphene-based heterostructure are conductive in nature. Here, we have also investigated the role of Pz (π) and Py (σ) atomic orbital bands of BP-ML and graphene. On Li intercalation, charge transfer is mainly site and interface definitely which helps to improve the specific capacity. The specific capacity of the proposed heterostructure varies from 546 to 427 mA h/g. For maximum Li confirmation, the volume expansion of these heterostructures is about 14–16%. The presence of graphene helps to maintain the open-circuit voltage (OCV) of heterostructure on an average 0.7 V. Also, helps to support the diffusion barrier energy in the range of 0.27–0.71 eV. This proposed 2D heterostructure could be the future material for the LIB's anode material.
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•BP-ML/Gr-ML heterostructure as prospective anode material for LiBs.•Specific capacities in the range of 543 to 427 mA h-gm−1.•Higher charge transfer from Li to B and P atoms of BP-ML.•Open circuit Voltage (OCV) of about 0.7 V for BP-ML/Gr-ML heterostructure.•Minimal structure distortion during Li intercalation/deintercalation process.
Development of an inexpensive electrocatalyst for hydrogen evolution (HER) and oxygen evolution reactions (OER) receives much traction recently. Herein, we report a facile one-pot ethyleneglycol (EG) ...mediated solvothermal synthesis of orthorhombic Co2P with particle size ~20–30 nm as an efficient HER and OER catalysts. Synthesis parameters like various solvents, temperatures, precursors ratios, and reaction time influences the formation of phase pure Co2P. Investigation of Co2P as an electrocatalyst for HER in acidic (0.5 M H2SO4) and alkaline medium (1.0 M KOH), furnishes low overpotential of 178 mV and 190 mV, respectively to achieve a 10 mA cm−2 current density with a long term stability and durability. As an OER catalyst in 1.0 M KOH, Co2P shows an overpotential of 364 mV at 10 mA cm−2 current density. Investigation of Co2P NP by XPS analysis after OER stability test under alkaline medium confirms the formation of amorphous cobalt oxyhydroxide (CoOOH) as an intermediate during OER process.
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•Co2P nanoparticles synthesized by one step solvothermal method.•HRTEM confirms the formation of nanoparticles with ~20–30 nm in size.•The Co2P catalyst exhibits high catalytic activity for HER and OER.•Co2P electrode shows excellent stability and durability during HER and OER.
The design and development of new and light weight two-dimensional (2D) heterostructures as anode materials to enhance the electrochemical properties for Li-ion batteries (LIB's) is a challenge. In ...this work, using first-principles study, we have demonstrated that the ratio of two-dimensional polyaniline (C
N) and graphene in the multilayer heterostructures plays a major role to define the Li storage properties and to provide metallicity for easy conduction of electrons. We have found that charge transfer between Li and the host depends on the interface and site, which helps in the improvement in specific capacity. The proposed heterostructures shows specific capacity varies from 558 mAh/gm to 423 mAh/gm. The specific capacity is high for heterostructures with more graphene in ratio which is correlated to higher charge accumulation in the host. Also, graphene helps to minimize the open-circuit voltage (OCV) of C
N and maintained an average of 0.4 V. The volume expansion for fully lithiated heterostructures is within 22 %. Li diffusion barrier energy varies in the range of 0.57 to 0.25 eV. The proposed 2D heterostructures could be a future material for anode in LIB's and the description of the interface effect on Li storage properties will help for further development of 2D heterostructure materials.
Particulate matter (PM) in air frequently poses a serious threat to human health. Smaller PM can easily enter into the alveolus and blood vessels with airflow. This work reports the first ...polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP) polymer blend nanofiber filter media for effectively capturing PM. Density functional theory (DFT) calculations are used to investigate the effect of the blending of two polymers on the dipole moment and the electrostatic potential. Based on the DFT calculations of the intermolecular interactions between nanofibers and PM, the PAN/PVP heteromolecular percentage is considered for experimental synthesis, which can provide better performance in the filtration of pollutants. The composite PAN/PVP fiber network was successfully developed and optimized to cope with complex environments during the actual filtration process. The role of the blending ratio of PAN and PVP in wt % was explored on PM2.5 capture, and the refined ratio overcame the conflict between high filtration efficiency and low air pressure resistance. The air filter medium PAN/PVP (6:2) possesses an extremely high air filtration efficiency of 92% under a very low pressure drop of 18 Pa for a 0.5 g m–2 basis weight. Both polar and nonpolar functional groups in blend nanofibers promoted significantly the electrostatic attraction and improved the filtration efficiency under static and dynamic airflow. The PAN/PVP nanofiber membranes maintain outstanding air filtration under different temperature and humidity conditions. This study will shed light on the fabrication of high-efficiency low-basis weight nanofiber filter media as an end product.
