Recent Developments in Electrodeposition of Transition Metal Chalcogenides-Based Electrode Materials for Advance Supercapacitor Applications: A Review.

High-performance supercapacitive electrode materials have received significant attention from researchers worldwide, thus aiming for comparable performance similar to the extensively used rechargeable batteries. For emerging energy storage technologies like flexible supercapacitors, transition metal chalcogenides (TMCs) have been in the spotlight due to their promising electrochemical features compared to other electrode materials. Among the synthesis techniques, electrodeposition-mediated preparation of thin films of TMCs offered an affordable binder-free approach for electrode fabrication that effectively improved the supercapacitor performance. Hence, this review mainly focussed on the electrodeposition-based syntheses of single/ multinary chalcogenides and their composites for supercapacitors applications. Further, the effects of different deposition parameters were discussed for boosting the supercapacitor performance. Finally, this review outlined the existing challenges and future perspectives in this research domain, which will assist the upcoming exploration in the energy storage field.

Advance Technologies in Biodegradable Flexible Solid-State Supercapacitors: A Mini Review on Clean and Sustainable Energy.

In the recent times research towards solid state supercapacitors (SSS) have increased drastically due to the promising performance in futuristic technologies particularly in portable and flexible electronics like smart watches, smart fabrics, foldable smartphones and tablets. Also, when compared to supercapacitors using liquid electrolyte, solid electrolyte has several advantages like high energy density, safety, high cycle life, flexible form factor, and less environmental impact. The crucial factor determining the sustainability of a technology is the eco-friendliness since the natural resources are being exploited in a wide scale. Numerous studies have focused on biodegradable materials for supercapacitor electrodes, electrolytes, and other inactive components. Making use of these biodegradable materials to design a SSS enables the technology to sustain for a very long time since biodegradable materials are not only environment friendly but also, they show relatively high performance. This review focuses on recent progress of different biodegradable electrodes, and electrolytes along with their properties, electrochemical performance and biodegradable capabilities for SSS have been analyzed and provides a concise summary enabling readers to understand the importance of biodegradable materials and to narrow down the research in a more rational way.

Bacterial chromate reductase, a potential enzyme for bioremediation of hexavalent chromium: a review.

Hexavalent chromium is mobile, highly toxic and considered as a priority environmental pollutant. Chromate reductases, found in chromium resistant bacteria are known to catalyse the reduction of Cr(VI) to Cr(III) and have recently received particular attention for their potential use in bioremediation process. Different chromate reductases such as ChrR, YieF, NemA and LpDH, have been identified from bacterial sources which are located either in soluble fractions (cytoplasm) or bound to the membrane of the bacterial cell. The reducing conditions under which these enzymes are functional can either be aerobic or anaerobic or sometimes both. Enzymatic reduction of Cr(VI) to Cr(III) involves transfer of electrons from electron donors like NAD(P)H to Cr(VI) and simultaneous generation of reactive oxygen species (ROS). Based on the steps involved in electron transfer to Cr(VI) and the subsequent amount of ROS generated, two reaction mechanisms, namely, Class I "tight" and Class II "semi tight" have been proposed. The present review discusses on the types of chromate reductases found in different bacteria, their mode of action and potential applications in bioremediation of hexavalent chromium both under free and immobilize conditions. Besides, techniques used in characterization of the Cr (VI) reduced products were also discussed.

Poly Meta-Aminophenol (PmAP) as a Solid-State Electron Mediator in the Z-Scheme, Ag3PO4/CoFe2O4 Heterojunction: Mineralization of Highly Concentrated Bisphenol-A and Reactive Dyes Water Pollutants.

This study demonstrated the effectiveness of poly meta-aminophenol (PmAP) as a solid electron mediator in the Z-scheme photocatalytic system for organic pollutants (viz. bisphenol-A and reactive dyes) mineralization and also illustrated how PmAP transported the photogenerated electrons from an O2-emitting photocatalyst (Ag3PO4) to a H2-emitting photocatalyst (CoFe2O4) enabling enhanced photocatalytic activity under visible light irradiation. The PmAP/Ag3PO4-CoFe2O4 (PAC-10), was prepared by a two-step process and characterized by various analytical methods to assess the impact of PmAP on optical, photocatalytic, and electrochemical characteristics of the CoFe2O4 (CFO)/Ag3PO4 composite. The morphological investigation revealed that the PmAP sheet was nicely decorated with evenly distributed Ag3PO4 and CoFe2O4 particles. The M-S plot and impedance analyses were used to assess the electrochemical capabilities of the catalyst. Z-scheme charge transfer pathways were well supported by the radical trapping experiment and HRTEM analysis of Pt photodeposited PAC-10 photocatalysts during the photoreaction. Because of its magnetic nature and ease of synthesis, the PAC-10 offers an easily recyclable Z-scheme photocatalytic system that has the potential for purifying wastewater with high concentrations (up to 100 mg/L) of organic pollutants within 30 min of visible light exposition.

Synergistic cobalt oxide/reduced graphene oxide/biochar nano-composite catalyst: harnessing the power of the catalyst for sustainable remediation of organic dyes and chromium(vi).

The exponential growth of industrial activities has led to a significant rise in the release of organic effluents, containing hazardous heavy metals and dyes, into the environment. These pollutants exhibit resistance to conventional biodegradation processes and are associated with carcinogenic properties, posing a severe threat to living organisms. In this context, the present research endeavours to address this environmental challenge through the development of an affordable and efficient photocatalyst, the Co3O4/reduced graphene oxide/biochar (CBG-10) heterostructure. The structural analysis of CBG-10, conducted through various techniques such as XRD, XPS, SEM, and optical property measurements, demonstrates its potential as a highly effective and easily recoverable catalyst for the mineralization of persistent pollutants like methylene blue, malachite green, and hexavalent Cr(vi). The recyclability of CBG-10 was confirmed through XRD studies, highlighting its stability and practical usability in wastewater purification. The photocatalytic behaviour of the catalyst was attributed to the generation of hydroxyl (˙OH) and superoxide radicals (˙O2-) during visible light illumination, as revealed by quenching experiments. The cost-effectiveness and stability of CBG-10 position it as a promising solution for addressing the challenges associated with the removal of stubborn organic contaminants from wastewater, thereby contributing to environmental protection and public health.

Mini-review on remediation of plastic pollution through photoreforming: progress, possibilities, and challenges.

The increasing plastic pollution has raised significant concerns about the environment and the destruction of its precious resources. Making value-added products out of plastic waste is an effective way to reduce plastic pollution and use it as a valuable resource. Plastic reforming driven by sunlight offers a quick and low-energy way to produce hydrogen from waste. Photoreforming of plastic waste is an emerging technology that cannot only break down plastic polymer waste into value-added chemicals but also produce solar fuel cell quality H2. Technologies, such as pyrolysis, combustion, and advanced oxidation, are right now being studied for converting plastic pollution into energy. A thorough summary and comparison of different technologies have not yet been published. Open dumping and combustion are two main steps to deal with waste plastics, but these processes experience inefficiencies and cannot adequately address the challenges. In this mini-review, we aimed to provide a short overview of the recently reported conventional and novel plastic waste treatment methods. The current research on the photoreforming of plastics conducted by various groups and some advantages and disadvantages of this practice has been discussed thoroughly. Also, some notes were made on the prospective future scope present in this particular research area to achieve a carbon-free fuel system. The purpose of this review is to encourage the utilisation of plastic garbage as an alternative source of energy.

Heterojunction assembled CoO/Ni(OH)2/Cu(OH)2 for effective photocatalytic degradation and supercapattery applications.

Mixed multimetallic-based nanocomposites have been considered a promising functional material giving a new dimension to environmental remediation and energy storage applications. On this concept, a hybrid ternary CoO/Ni(OH)2/Cu(OH)2 (CNC) composite showing sea-urchin-like morphology was synthesized via one-pot hydrothermal approach, and its photocatalytic and electrochemical performances were investigated. The photocatalytic performance was explored using Congo red (CR) as a dye pollutant under visible light illumination. The presence of mixed phases of ternary metal ions could minimize the recombination efficacy of photogenerated charge carriers on the basis of the heterojunction mechanism, resulting in 90% degradation of CR dye (40 mg L-1). The effect of scavengers coupled with electrochemical experiments revealed O2-. radical as the predominating species responsible for the degradation of CR. From the electrochemical analysis of CNC, the well-distinguished redox peaks indicated the redox-type nature with a specific capacity of 405 C g-1. For practical applications, an supercapattery (CNC( +)|KOH|AC( -)) was assembled furnishing an energy density of 42 W h kg-1 at a power density of 5160 W kg-1 at 5 A g-1 along with a high capacity retention and coulombic efficiency of 98.83% over 5000 cycles.

CZTS (Cu2 ZnSnS4 )-based Nanomaterials in Photocatalytic and Hydrogen Production Applications: A Recent Progress towards Sustainable Environment.

A variety of unique compounds have been examined to accommodate the current demand for useful multi-functional nanomaterials, copper-based quaternary CZTS semiconductors are one of them. Due to their special characteristic features like non-toxicity, cheap, and abundance, they have been recommended in recent literature for various applications. Apart from individual CZTS, different hetero-structures have also been prepared with different compounds which is well discussed and elaborated in this article. Additionally, their preparation methods, properties, and application viability have also been discussed comprehensively. The application of CZTS such as photocatalytic dye degradation and hydrogen evolution reaction has been elaborated on in this article identifying their benefits and challenges to give readers a thorough visualization. Apart from that, challenges reported in studies, a few approaches are also mentioned to possibly counter them.

Role of polyaniline in accomplishing a sustainable environment: recent trends in polyaniline for eradicating hazardous pollutants.

Attaining a sustainable environment has become a prime area of research interest, as it is an utmost necessity for a healthy life. Hence, ample studies have been carried out in adopting different processes and utilizing various materials to attain the goal. Herein, we present an exclusive discussion on one such material, i.e., polyaniline (PANI) and its derivatives. Being an intrinsic conducting type, it has grabbed more attention due to its durability in different doped/un-doped states, promptness in structural alteration, and solution processability. This review presents an exhaustive discussion on published reports showing utilization of PANI and its derivative in various forms like pure and composites, for cleaning the environment through adsorption, photodegradation, etc., and the various methods adopted in order to achieve an optimum operating condition to obtain the maximum outcome. In addition to these merits and demerits, various technical challenges faced with materials have been also presented. Therefore, it is expected that this piece of work, presenting the exhaustive discussion on PANI and; its derivatives would help to develop a better understanding of this excellent conducting polymer PANI and provide a state of art on the role of this material for attaining sustainable surroundings for the living beings.

Polymer Composites with Quantum Dots as Potential Electrode Materials for Supercapacitors Application: A Review.

Owing to the nanometer size range, Quantum Dots (QDs) have exhibited unique physical and chemical properties which are favourable for different applications. Especially, due to their quantum confinement effect, excellent optoelectronic characteristics is been observed. This considerable progress has not only uplifted the singular usage of QDs, but also encouraged to prepare various hybrid materials to achieve superior efficiency by eliminating certain shortcomings. Such issues can be overcome by compositing QDs with polymers. Via employing polymer composite with QDs (PQDs) for supercapacitor applications, adequate conductivity, stability, excellent energy density, and better specific capacitance is been achieved which we have elaborately discussed in this review. Researchers have already explored various types of polymer nanocomposite with different QDs such as carbonaceous QDs, transition metal oxide/sulphide QDs etc. as electrode material for supercapacitor application. Synthesis, application outcome, benefits, and drawbacks of these are explained to portray a better understanding. From the existing studies it is clearly confirmed that with using PQDs electrical conductivity, electrochemical reactivity, and the charge accumulation on the surface have prominently been improved which effected the fabricated supercapacitor device performance. More comprehensive fundamentals and observations are explained in the current review which indicates their promising scopes in upcoming times.

Adsorption of some bivalent heavy metal ions from aqueous solutions by manganese nodule leached residues.

The leached residue, generated after selective extraction of Cu, Ni, and Co in sulfur dioxide-ammonia leaching of manganese nodules, was characterized and batch isothermal adsorption experiments were conducted at ambient temperature to evaluate the effectiveness of the water-washed leached residue for removal of different bivalent metal ions from aqueous synthetic solutions. The effects of pH, initial metal ion concentrations, amount of adsorbent, interfering ions, and heat treatment were also investigated. The uptake of metal ions increased with increasing pH. Under identical conditions the adsorption capacity increased in the order Cd(2+)

Defluoridation of drinking water using activated titanium rich bauxite.

The potential of thermally activated titanium rich bauxite (TRB) for adsorptive removal of excess fluoride from drinking water was examined. Adsorption with respect to variation of pH, adsorbent dose, initial fluoride concentration, presence of interfering ions and heat treatment were investigated by batch equilibrium experiments. Thermal activation at moderate temperatures (300-450 degrees C) greatly increased the adsorption capacity of TRB. The rate of adsorption was rapid and maximum level was attained within 90 min. The uptake of fluoride increased with increasing pH, reached to a maximum at pH 5.5-6.5 and thereafter decreased. The adsorption kinetics was found to follow first order rate expression and the experimental equilibrium adsorption data fitted reasonably well to both Langmuir and Freundlich isotherm models. The presence of common interfering ions in drinking water did not greatly affect the uptake of fluoride from aqueous solution indicating F specific sorption behaviour of TRB. Nearly complete desorption of adsorbed fluoride from loaded bauxite was achieved by treating with aqueous solutions of pH > or =11.1 ([NaOH] > or =0.015 mol/dm(3)).

Investigation on mechanism of Cr(VI) reduction and removal by Bacillus amyloliquefaciens, a novel chromate tolerant bacterium isolated from chromite mine soil.

A strain CSB 9 isolated from chromite mine soil of Sukinda, India was identified as Bacillus amyloliquefaciens based on biochemical and 16S rRNA gene sequencing. The strain exhibited relatively high tolerance to Cr(VI) (⩽900mgL(-1)) and fast reduction rate of 2.22mg Cr(VI) L(-1)h(-1), under optimized conditions of 100mgL(-1) Cr(VI), pH 7 and temperature 35°C within 45h. Mechanism of Cr(VI) reduction as well as nature and fate of the reduced product were studied to determine the scope of removal of reduced Cr(III) end product. AAS analyses of the culture products treated with Cr(VI) for 45h showed the distribution of Cr(III) in pellet and culture supernatant to be 37.4±1.7 and 62.6±3.4mgL(-1), respectively. In SEM images, the bacterial pellets with Cr(VI) treatment appeared coagulated, rough and porous whereas the pellets without Cr(VI) treatment appeared regular, smooth and non-porous in structure. SEM-EDX of the bacterial precipitates under Cr(VI) treatment revealed immobilization of Cr(III) species on the bacterial cell surface. Further Raman spectroscopy analysis confirmed the presence of Cr(III) species, with characteristic peak at around 600cm(-1). TEM-EDX study of the bacterial precipitates under Cr(VI) treatment showed intracellular deposition of Cr(III) which are in nanometric range. Further characterization of reduced product by XRD, FT-IR and SAED analyses suggested the formation of poorly crystalline end products. A Cr(VI) removal mechanism considering both the surface immobilization and intracellular accumulation of Cr(III) along with the formation of coagulated cell precipitate by living B. amyloliquefaciens was suggested.

Reduction of selenite to red elemental selenium by moderately halotolerant Bacillus megaterium strains isolated from Bhitarkanika mangrove soil and characterization of reduced product.

Two Gram (+) bacterial strains, BSB6 and BSB12, showing resistance and potential for Se(IV) reduction among 26 moderately halotolerant isolates from the Bhitarkanika mangrove soil were characterized by biochemical and 16S rDNA sequence analyses. Both of them were strictly aerobic and able to grow in a wide range of pH (4-11), temperature (4-40°C) and salt concentration (4-12%) having an optimum growth at 37°C, pH ∼7.5 and 7% salt (NaCl). The biochemical characteristics and 16S rDNA sequence analysis of BSB6 and BSB12 showed the closest phylogenetic similarity with the species Bacillus megaterium. Both the strains effectively reduced Se(IV) and complete reduction of selenite (up to 0.25 mM) was achieved within 40 h. SEM with energy dispersive X-ray and TEM analyses revealed the formation of nano size spherical selenium particles in and around the bacterial cells which were also supported by the confocal micrograph study. The UV-Vis diffuse reflectance spectra and XRD of selenium precipitates revealed that the selenium particles are in the nanometric range and crystalline in nature. These bacterial strains may be exploited further for bioremediation process of Se(IV) at relatively high salt concentrations and green synthesis of selenium nanoparticles.