Nanoporous carbon (NPC) materials with high specific surface area have attracted considerable attention for electrochemical energy storage applications. In the present work, we have designed novel symmetric supercapacitors based on NPC by direct carbonization of Zn-based metal-organic frameworks (MOFs) without using an additional precursor. By controlling the reaction conditions in the present study, we synthesized NPC with two different particle sizes. The effects of particle size and mass loadings on supercapacitor performance have been carefully evaluated. Our NPC materials exhibit excellent electrochemical performance with a maximum specific capacitance of 251 F g-1 in 1 M H2SO4 electrolyte. The symmetric supercapacitor studies show that these efficient electrodes have good capacitance, high stability, and good rate capability.

Fabrication of symmetric supercapacitors based on MOF-derived nanoporous carbons

Biological cell template synthesis of nitrogen-doped porous hollow carbon spheres/MnO2 composites for high-performance asymmetric supercapacitors

Piezoelectric materials and devices have drawn extensive attention for energy harvesting due to their excellent electromechanical conversion properties. With increasing concerns about environmental problems in traditional lead-based piezoelectric materials, it is imperative to develop lead-free piezoelectric alternatives. This paper is intended to give a brief review on the most recent advances in both inorganic (with an emphasis on piezoelectric ceramics and ZnO nanostructures) and organic (i.e. polyvinylidene difluoride (PVDF) and its copolymers and their composites, and biopolymers) lead-free piezoelectric materials. State-of-the-art piezoelectric devices, namely, nanogenerators, sensors, and transducers, are also introduced with detailed examples. Finally, the challenges and perspectives of lead-free piezoelectric materials and devices are given.

An overview of lead-free piezoelectric materials and devices

Nickel selenide (NiSe) nanoparticles were grown on graphene nanosheets (GN) with different mass ratios to obtain their corresponding NiSe/GNx (x = 0.25 to 1.00) nanohybrids by a facile in situ hydrothermal process to integrate the advantages of the high specific surface area of graphene and the homogeneously immobilized catalytic sites of NiSe. The nanohybrid with a mass ratio of 1 : 0.50 (i.e., NiSe/GN0.50) exhibited higher electrocatalytic activity and electrolyte diffusion. Thus, NiSe/GN0.50 exhibited an improved photo-conversion efficiency (PCE) of 12% (η = 8.62%) compared to a standard Pt (η = 7.68%)-based dye-sensitized solar cell (DSSC). This improved PCE mainly originated from the catalytic ability of NiSe and the multiple interfacial electron transfer pathways of graphene, resulting in enhanced charge transfer and fast tri-iodide reduction kinetics at the counter electrode/electrolyte interface. The results obtained from the cyclic voltammetry (CV), electrochemical AC-impedance (EIS) and Tafel polarization studies validated the synergistic effects of NiSe and GN and the high potential of this nanohybrid as an efficient counter electrode (CE) for DSSCs.

Optimizing graphene content in a NiSe/graphene nanohybrid counter electrode to enhance the photovoltaic performance of dye-sensitized solar cells

The removal of wastes through solar-induced technologies is gaining extensive momentum over the last few years. Photocatalytic (PC) removal of dyes and other waste products from the main stream and aquatic media is considering industrially feasible technologies. Photocatalytic degradation (PD) could economically convert complex molecules into smaller, non-toxic, and lower molecular weight species through photo-assisted redox reactions. Mechanistically, PD process is based on the production of highly reactive, photogenerated hydroxyl and superoxide anion radicals that attack dye molecules and completely mineralize it into more unaffected species, such as CO2 and H2O. This advance technology has advantages over other conventional methods in terms of simplicity, complete pollutants mineralization, no harmful byproducts, cost-effectiveness and reducing contaminants at parts per million (ppm) and parts per billion (ppb) level. The aim of this review is to provide a thorough overview of heterogeneous PD with the literature support. The first section of the review will address the basic principle and materials utilization. This will be followed by a brief section on the different mechanisms reported for PD over the years with suitable examples. Finally, an overview will be provided to various parameters, which influence the process and mechanism pathway. This review aims to not only educate the beginners in the field of PD but also target experienced researchers, who are involved in heterogeneous PD and predicting mechanistic studies.

Heterogeneous photodegradation of industrial dyes: An insight to different mechanisms and rate affecting parameters

In this study, the new material Fe3O4@BTCA has been synthesized by immobilization of 1,2,4,5-Benzenetetracarboxylic acid (BTCA) on the surface of Fe3O4 NPs, obtained by co-precipitation of FeCl3.6H2O and FeCl2.4H2O in the basic conditions. Characterization by P-XRD, FE-SEM, and TEM confirm Fe3O4 has a spherical crystalline structure with an average diameter of 15 nm, which after functionalization with BTCA, increases to 20 nm. Functionalization also enhances the surface area and surface charge of the material, confirmed by BET and zeta potential analyses, respectively. The dye adsorption capacity of Fe3O4@BTCA has been investigated for three common dyes; Congo red (C.R), Methylene blue (M.B), and Crystal violet (C.V). The adsorption studies show that the material rapidly and selectively adsorbs C.R dye with very high adsorption capacity (630 mg/g), which is attributed to strong H-bonding ability of BTCA with C.R dye as indicated by adsorption mechanism study. The material also shows excellent recyclability without any considerable loss of adsorption capacity. Adsorption isotherm and kinetic studies suggest that the adsorption occurs by the Langmuir adsorption model following pseudo-second-order adsorption kinetics.

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Selective and Recyclable Congo Red Dye Adsorption by Spherical Fe 3 O 4 Nanoparticles Functionalized with 1,2,4,5-Benzenetetracarboxylic Acid

A 3D porous Cu(II)-MOF (1), having Lewis acid−base dual-functional sites, has been utilized, whose frameworks have two types of 1D channels decorated with both axially water-bound metal sites and weak base, i.e., tertiary amine groups in the crystallographic c-axis. Upon activation under a high vacuum at 120 °C, the axial water molecule is removed and affords a solvent-free and unsaturated Lewis acidic Cu(II) containing framework (1′). The piperazine functionalities from the linkers enhance the selective adsorption of CO2 which, in turn, facilitate the further interaction with the open Cu(II) metal centres, leading to catalytic chemical fixation of CO2 into five-membered cyclic carbonates, in the presence of epoxides and co-catalyst TBAB, under mild and solvent-free reaction conditions. The significance of dual functionalization and the synergy with TBAB on adeptly catalyzed CO2 fixation are explored using several epoxides, and substantial conversion is achieved. Moreover, the catalyst 1′ displays satisfactory stability and easy recyclability for five consecutive cycles without any appreciable loss in its catalytic activity. The results are compared with various MOFs based catalysts at the closest reaction conditions and, based on literature and experimental inferences, a possible mechanism of chemical fixation of CO2 with epoxide catalyzed by 1′ has been proposed.

A Three-Dimensional Cu(II)-MOF with Lewis acid−base dual functional sites for Chemical Fixation of CO2 via Cyclic Carbonate Synthesis

Nitrogen-rich Cu-MOF decorated on reduced graphene oxide nanosheets for hybrid supercapacitor applications with enhanced cycling stability

The influence of various ionic liquids such as 1,3-dimethyl imidazolium iodide (DMImI), 1-propyl-3-methyl imidazolium iodide (PMImI), 1-butyl-3-methyl imidazolium iodide (BMImI) and 1-hexyl-3-methyl imidazolium iodide (HMImI) embedded electrospun PVdF-HFP membrane electrolytes (esPMEs) on the photovoltaic performances of Dye-sensitized solar cells (DSSCs) were investigated. The influence of alkyl chain length of imidazolium and the concentration of ionic liquid electrolytes on the charge diffusion and electron transport kinetics were investigated by electrochemical impedance and Tafel polarization studies. Among the DSSCs fabricated with esPME of various ionic liquids, DSSC with 0.5M BMImI-esPME exhibited highest photoconversion efficiency of 7.08% with excellent long-term stability.

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Influence of Various Ionic Liquids Embedded Electrospun Polymer Membrane Electrolytes on the Photovoltaic Performance of DSSC

Stepwise synthesis of aminotetrazole functionalized MgO–SiO2 (MSNT) nanocomposites has been achieved by a simple wet chemical method. The as-synthesized nanomaterial is investigated for the removal...

Sarathkumar Krishnan

Papers

Selective and Recyclable Congo Red Dye Adsorption by Spherical Fe 3 O 4 Nanoparticles Functionalized with 1,2,4,5-Benzenetetracarboxylic Acid

A Three-Dimensional Cu(II)-MOF with Lewis acid−base dual functional sites for Chemical Fixation of CO2 via Cyclic Carbonate Synthesis

Nitrogen-rich Cu-MOF decorated on reduced graphene oxide nanosheets for hybrid supercapacitor applications with enhanced cycling stability

Influence of Various Ionic Liquids Embedded Electrospun Polymer Membrane Electrolytes on the Photovoltaic Performance of DSSC

Aminotetrazole-Functionalized SiO2 Coated MgO Nanoparticle Composites for Removal of Acid Fuchsin Dye and Detection of Heavy Metal Ions