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In the present study, we have proposed the phosphorus (P)-doped CoS2 electrocatalyst through a simple hydrothermal route and utilized as an economical and earth-abundant electrocatalyst for hydrogen evolution reaction (HER). A sequence of P-doped CoS2 electrocatalysts were obatined by using different NaH2PO4 contents. The as-synthesized samples were characterized by XRD, SEM, HR-TEM, element mapping, and XPS analyses. It is found that these P-doped CoS2 materials composed of high purity nanoparticles and stacked in a block structure. The electrochemical performance has been investigated in 0.5-M H2SO4 electrolyte. The results indicate that the doping of phosphorus can significantly increase the electrocatalytic hydrogen evolution activity of CoS2. Among the different samples, the P-doped CoS2 attained with 5 mmol of NaH2PO4 contents offers the highest HER performance with a minimum overpotential of 109 mV at 10 mA cm-2, the smallest Tafel slope of 48 mV dec-1, and an excellent long-term durability over 1,000 cycles. The analysis results illustrate that the doped phosphorus may change the internal properties of CoS2, which promotes the ability of charge transfer and electrochemical active sites, resulting in the significantly increased HER activity compared with bare CoS2. Therefore, this work demonstrates that a proper doping of phosphorus is a suitable approach to improve the catalytic ability of metal sulfides for HER application.

The need for clean energy production and utilization is urgent and continues to grow due to the serious issues of human population growth and environmental pollution. The energy crisis is driving the demand for novel and innovative materials for the development of alternative energy sources and the fabrication of innovative energy storage devices. Supercapacitors are emerging electrochemical energy devices for future clean energy technologies. Supercapacitors have several distinctive features, such as rapid charging rates, high power densities, long cycle lives, and simple configurations. Thus, supercapacitors can serve as bridges to span the power gap between conventional capacitors and batteries or fuel cells. The current state of supercapacitor research is summarized in this review, and rapid progress in the basic development and practical application of supercapacitors is highlighted. A concise review of the technologies and working mechanisms of different supercapacitors is presented along with recent developments in the application of transition metal sulfide-based materials in electrochemical supercapacitors. Nanostructured transition metal sulfides have gained prominence as advanced electrode materials for an electrochemical supercapacitor due to their outstanding properties. These include good electrical conductivity, high specific capacity, low electronegativity, unique crystal structures, and high redox activity. The electrochemical performance of transition metal sulfides is superior to that of transition metal oxides which is attributed to the replacement of oxygen atoms with sulfur atoms. In this context, special emphasis is placed on nickel, cobalt, molybdenum, tin, manganese, and tungsten metal sulfides and their composites as advanced electrode materials for supercapacitor applications. Finally, the benefits and challenges of using transition metal sulfide-based electrode materials for future clean energy storage are discussed.

Herein, we propose a new concept of energy storage system composed of a nonpolarized electrode and a polarized electrode (PPE) with an impressive energy density. It offered nearly 4 times higher energy density than that of carbon-based supercapacitor. Among the suggested potential PPE system, we introduced an electrodeposited nanozinc on the copper foam as the nearly nonpolarized electrode and a Zn-2,5-dihydroxyterephthalic acid (DHTA) metal-organic framework (MOF)-derived activated porous carbon as a nearly polarized electrode in KOH-ZnO electrolyte to constitute the C|Zn PPE system prototype. The C|Zn system achieved an impressive energy density of 84.5 Wh kg-1 at 1000 W kg-1, 4 times higher than that of the C|C supercapacitor. It also shows a high capacitance retention rate of 94.5% at 10 A g-1 after 10 000 cycles. Therefore, the amazing results indicate that the PPE energy system integrates the advantages of supercapacitors and secondary batteries. It will be a promising and effective energy device for higher-performance electric vehicles.

In the present study, we propose a novel electrode material of β-nickel hydroxide covering nickel/aluminum layered double hydroxides via a facile complexation–precipitation method. The as-obtained materials with 3-dimensional nanostructures are further utilized as highly capable electrode material in nickel–metal hydride batteries. The electrochemical test results demonstrated the β-nickel hydroxide covering nickel/aluminum-layered double hydroxides with 28% of β-nickel hydroxide provided a superior specific capacity value of 452 mA·h·g−1 in a current density of 5 A·g−1 using 6 M KOH as electrolyte as compared with other materials. In addition, the optimized sample displays an outstanding cyclic stability along with a huge specific capacity value of 320 mAh·g−1, and very small decay rate of 3.3% at 50 A·g−1 after 3000 cycles of charge/discharge test. These indicate that the newly designed material with nanostructures not only provides an efficient contact interface between electrolyte and active species and facilitates the transport of electrons and ions, but also protects the 3-dimensional nickel/aluminum layered double hydroxides, achieving a high specific capacity, fast redox reaction and excellent long-term cyclic stability. Therefore, the β-nickel hydroxide covering nickel/aluminum layered double hydroxides with superior electrochemical performance is predictable to be a gifted electrode material in nickel–metal hydride batteries.

In the present study, we have fabricated a new Z-scheme BiFeWO6/MoS2 composite for photocatalytic elimination of organic contaminants from the waste-water. A series of BiFeWO6/MoS2 composites were obtained by changing the amounts of BiFeWO6 from 1 to 10 mg through a facile hydrothermal method. The phase structures and morphologies of these BiFeWO6/MoS2 composites were analyzed by SEM, HR-TEM, XRD, UV–vis DRS, element mapping and XPS techniques. Afterward, the dye-degradation experiments were conducted for the removal of Rhodamine B (RhB) using as-obtained BiFeWO6/MoS2 composite samples under visible-light illumination to evaluate their photocatalytic activity. It is found that the BiFeWO6/MoS2 composites exhibited great photocatalytic behavior than the pure BiFeWO6 and MoS2 samples. In particular, the BiFeWO6/MoS2 composite with 5 mg of BiFeWO6 showed a quickly complete photocatalyst degradation ability of RhB in 75 min with high photo-stability and reusability behavior. This superior catalytic response of BiFeWO6/MoS2 composite may be contributed by its high light harvesting capacity as well as fast separation and movement of photo-generated electron-hole pairs. This proposed BiFeWO6/MoS2 composite is a very promising photocatalyst for environmental remediation work.

Herein, various rare-earth metal (Eu, Gd, and Sm) ion-doped ZnSe/FeS2 double-layer thin films were deposited on an ITO plate via a quick and facile electrochemical deposition (ECD) method. X-ray diffraction (XRD) studies confirmed that the fabricated double-layer thin films exhibited sharp diffraction peaks which indicate their well crystalline nature. Scanning electron microscopy (SEM) showed that the double layer of ZnSe/FeS2 films was well deposited on the ITO substrate. The electron paramagnetic resonance (EPR) spectra indicated one weaker peak center at 335 mT and one high-instance very sharp peak center around 157 mT for the different metal-doped ZnSe/FeS2 double-layer thin films. From the Raman spectra, it was found that a broad peak centered at 2778 cm−1, which revealed the characteristic vibration of the ZnSe/FeS2 double layer. Electrochemical impedance spectroscopy (EIS) suggested that the Gd3+-doped ZnSe/FeS2 sample possesses a lower charge transfer resistance (Rct) of 39 Ω when compared with Eu3+- and Sm3+-doped ZnSe/FeS2 samples, demonstrating the excellent conductivity of Gd3+-doped ZnSe/FeS2 films. Moreover, the photoelectrochemical study indicates that the Gd3+-doped ZnSe/FeS2 thin film displayed a higher photocurrent than the other samples. This higher photocurrent of Gd3+-doped ZnSe/FeS2 films is mainly owing to its efficient charge separation efficiency to produce more photo-excited electron-hole pairs. Therefore, the attained Gd3+-doped ZnSe/FeS2 double-layer thin film is a promising material for photoelectrochemical device application.

Hydrogen evolution reaction has been recognized as a green technology in the field of electrochemical energy conversion and storage devices. Nevertheless, it is necessary task to finding an economical and effective electrocatalysts for HER. Among the different HER catalysts, the cobalt disulfide (CoS2) showed an excellent HER activity owing to its low cost, easy to synthesize and good stability. Hence, in this work, we prepared a series of CoS2/CNT composites with different contents CNT from 4 to 12 wt% by a simple one-step hydrothermal method to investigate the influence of CNT on HER activity of CoS2. The structural and morphological properties of the obtained samples were analyzed through XRD, SEM, HR-TEM, and XPS. The SEM images of CoS2/CNT composite showed the spherical-shaped CoS2 covered by the CNT nanostructure. In addition, the electrochemical tests were carried out using 0.5 M H2SO4 solution in order to assess their HER activity. The attained electrochemical results showed that the CoS2/CNT composite with 8% CNT offers an outstanding HER activity with the smallest overpotential of 155 mV at 10 mA cm−2 and lowest Tafel slope of 59 mV dec−1 when compared with other composites. Also, the optimized CoS2/CNT composite provided excellent stability in the acidic medium after 1000 cycles. Therefore, the as-synthesized CoS2/CNT composite will be an efficient, low-cost and Pt-free electrocatalyst for HER application.

In this work, we first time reported the BiFeWO6/α-AgVO3 composite as photocatalyst for waste-water treatment. Firstly, the BiFeWO6 nanoparticles were synthesized by a simple solvothermal route. Afterwards, a sequence of the BiFeWO6/α-AgVO3 composites was synthesized with various amounts of BiFeWO6 through a cost-effective co-precipitation route. The visible-light photocatalytic behaviors of these BiFeWO6/α-AgVO3 composites were further assessed through the removal of Rhodamine B (RhB) dye. It is indicates that BiFeWO6/α-AgVO3 composite displays a higher photocatalytic response than that of pure α-AgVO3 and BiFeWO6. This enhanced response of BiFeWO6/α-AgVO3 composite is mainly owing to the fast separation and migration of the photo-generated charge carriers via the creation of heterojunction between the BiFeWO6 and α-AgVO3. The recycling experiments demonstrate that BiFeWO6/α-AgVO3 possesses a better photostability and reusability character. Furthermore, a possible photocatalytic mechanism of BiFeWO6/α-AgVO3 composite for removal of RhB was also presented. Therefore, this fabricated BiFeWO6/α-AgVO3 composite can be a promising photocatalytic material for environmental remediation work.

In this study, we synthesized nitrogen-doped Mo2C@carbon nanotube (N-Mo2C@CNT) composites via a facile one-pot method of solvothermal followed by calcination. The SEM and TEM results of N-Mo2C@CNT composites show that the sphere-shaped N-Mo2C is covered by CNTs. In addition, the electrocatalytic performances of the as-obtained N-Mo2C@CNT composites were examined towards the hydrogen evolution reaction (HER) in acidic media. It is revealed that the N-Mo2C@CNT composite with optimum content of CNTs (30 mg) exhibits an excellent catalytic activity with less overpotential of 183 mV at 10 mA cm−2 and smaller Tafel slope of 73.95 mV dec−1 as compared with pure Mo2C. Furthermore, it has a good cycling stability after 1000 cycles. This enhanced activity due to the creation of more active sites, large specific surface area by better synergistic effect between the N-Mo2C and CNT. Consequently, the N-Mo2C@CNT composite is a viable alternative to the noble metal electrocatalysts for HER.

In this work, a visible-light-driven WO3/AgCl composite photocatalyst was synthesized by a facile single-pot hydrothermal method using α-Ag2WO4 and HCl as precursors. A series of WO3/AgCl composite photocatalysts were synthesized with the addition of different amount (0.5, 1.0, 1.5 and 2.0 mL) of 2 M HCl solution to α-Ag2WO4. Afterwards, the photocatalytic abilities of the WO3/AgCl composite photocatalysts were investigated towards the photodegradation of Rhodamine B (RhB) under visible-light illumination. Results show that the WO3/AgCl composite exhibits an outstanding photocatalytic activity as compared with those pure WO3 and AgCl. This enhancement may be due to the fast charge separation efficiency of the photoexcited electron-holes pairs. However, among various composites, the WO3/AgCl composite obtained with the addition of 1 mL of HCl is found to display the highest photocatalytic activity. This optimized composite shows a complete degradation of RhB within 30 min. Furthermore, the WO3/AgCl composite has an excellent photostability. Finally, a possible photocatalytic degradation mechanism of RhB degradation using WO3/AgCl composite is also proposed. Therefore, these high photocatalytic activity and stability results reveal that the WO3/AgCl composite is a promising material for wastewater treatment and other environmental remediation applications.

In this study, a new porous-like amorphous carbon is obtained via zinc-based fluorinated metal-organic framework as carbon rich source by a template free thermal treatment at 750 °C under the nitrogen atmosphere. This porous-like amorphous carbon is further used as cathode material for high-performance supercapacitors. The porous carbon possesses a huge specific surface area of 1234 m2 g−1 with ordered mesoporous arrangement. The electrochemical activities of the fabricating materials are assessed by cyclic voltammetry and charge-discharge analysis in 6 M KOH electrolyte. Results reveal that porous-like amorphous carbon displays a superior specific capacitance of 360 and 322 F g−1 at a scan rate of 1 mV s−1 and current density of 1 A g−1, respectively with specific energy density of 70 Wh kg−1 at a current density of 1 A g−1, which are much better than the reported porous carbons in the literatures. In addition, this carbon material shows an excellent capacitance retention of 98.6% and 95.8% at the ultra-high current densities of 50 and 100 A g−1, respectively after 100,000 cycles. Therefore, the outstanding capacitive characteristics with high electrochemical stability of the novel porous-like amorphous carbon demonstrate that it will be a promising electrode material for ultra-fast supercapacitors.

In this work, nickel-iron layered double hydroxides nanoflakes are grown on nickel foam by a facile in-situ complexation precipitation method. The fabricated nickel-iron layered double hydroxides/nickel foam with special 3D structure with large electrochemical activated surface area is proposed as a greatly enhance electrode material for oxygen evolution reaction. The electrochemical properties of the as-fabricated nickel-iron layered double hydroxides/nickel foam electrode are evaluated using 1 mol L−1 KOH as electrolyte. The obtained electrochemical results show that the fabricated nickel-iron layered double hydroxides/nickel foam electrode exhibits a low overpotential of 245 mV at current density of 10 mA cm−2 with small Tafel slope of 27 mV dec−1. Also, it displays a much longer durability of 20 h with very small decay of 0.02% as compared with 3D nickel foam, IrO2 and the related catalysts reported. Therefore, this study indicates that the nickel-iron layered double hydroxides/nickel foam is a promising electrode material for oxygen evolution reaction due to its facile preparation method, low cost and environmentally friendly nature.

The advancement of heterostructured visible-light active metal oxide based semiconductor photocatalysts have received an enormous consideration in the field of environmental remediation due to their excellent growth with unique surface morphology, tunable properties, suitable for absorbing more visible region in the solar radiation. The several categories of organic pollutants are released into the earth by an expanding insurgency in agricultural and industrial areas. The solar-light driven photocatalytic degradation is an efficient process for the elimination of toxic pollutants from wastewaters. In this manner, it is important to develop newer metal oxide-based photocatalytic materials to solve the majority of basic issues associated with environment. In this review, we have mainly focussed on the on recent developments in metal oxide based heterostructures for photocatalytic applications towards environmental remediation. The special attention has been made on different metal oxide materials under various categories such as ZnO, WO3, Fe2O3 and Bi2O3 based photocatalysts. Finally, the stability and challenges to fabricate novel heterostructures suitable for environmental remediation applications are also highlighted.

Metal Organic Frameworks or related carbon materials are the ideal materials for supercapacitors due to their high surface area and unique porous structure. Here, we propose a new green and recyclable synthesis method of porous carbon. Aluminum hydroxide (Al(OH)3) and trimesic acid (BTC) are employed as raw materials to obtain aluminium trimesic (denoted as Al-BTC) via their covalent reaction. Then, the porous carbon is obtained through carbonization and dissolving process to remove the aluminum oxide (Al2O3). Al(OH)3 is recovered by the Bayer method for the next batch. The SEM images show that the porous carbon has rugby-like morphology with the same of 400 nm wide and 1000 nm long which indicates the porous carbon with c/a ratio of 2.5 providing the largest specific volume surface area. The sample offers 306.4 F g−1 at 1 A g−1, and it can retain 72.2% even at the current density of 50 A g−1. In addition, the porous carbon provides excellent durability of 50,000 cycles at 50 A g−1 with only 5.05% decline of capacitance. Moreover, the porous carbon has an ultrafast charge acceptance, and only 4.4 s is required for one single process, which is promising for application in electric vehicles.

Nickel-based hydroxides with excellent electrochemical performance have been considered as cathode materials for Ni/MH batteries. In this paper, a Ni/Al layered double hydroxides (Ni/Al LDHs) material with three-dimensional (3D) spherical structure is synthesized by a facile stable dual complexation–precipitation method. SEM images show that the obtained Ni/Al LDHs possess 3D spherical structure composed of nanosheets. XRD and CV tests indicate that doping of Al increases the distance between Ni–Al layers, greatly improving the specific capacity of the obtained materials. The electrochemical tests show that the specific capacity of the obtained material with 18% Al is up to 383.4 mAh g−1 at a current density of 1 A g−1. In addition, when the current density is further increased to 10 and 20 A g−1, the specific capacity of this material still maintains 345.0 mAh g−1 and 307.9 mAh g−1, respectively, which implies that this cathode material can provide remarkable power densities. Moreover, the material composed of Ni/Al LDHs keeps 97.6% initial capacity after 5000 cycles at a current density of 10 A g−1, showing an excellent cycling stability and durability.

In recent times, silver (Ag) based semiconductors have been gained a lot of attention as photocatalysts for industrial waste-water treatment owing to their strong visible-light absorbing capability and small bandgap energy. Therefore, herein, we have designed and utilized a one-pot hydrothermal approach to the synthesis of nano-sized AgBr covered potato-like Ag

Herein, we propose a new highly porous natural carbon material from renewable and inexpensive jujube fruits as a carbon source applied in supercapacitors. The combination of pre-carbonization and chemical activation approaches is employed to product hierarchical porous carbon from natural jujube fruits. The specific surface area of the prepared porous carbon is increased from 85.4 to 1135 m2 g−1 after the completion of NaOH activation at an optimized condition, which is beneficial to enhancing electrochemical performance of supercapacitors. A 3-electrode configuration was utilized to explore the electrochemical ability of porous carbon in 6 M KOH electrolyte. The acquired results demonstrate that porous carbon displays the specific capacitance of 587, 460 and 324 F g−1 at 0.1, 1 and 100 A g−1, respectively, which is confirmed by its admirable capacitance and rate behaviors. The porous carbon also shows a wonderful durability with a capacitance retention of 92.2% after 130,000 cycles at 50 A g−1. Moreover, the assembled symmetrical coin-like supercapacitors with wide potential window of 2.5 V in 1 M Et4NBF4/AN organic electrolyte offer a high energy density of 23.7 Wh kg−1 at 0.629 kW kg−1 with remaining 94% capacitance over 10,000 cycles at 30 A g−1, indicating its practical application prospect. As a result, the present study proves the natural jujube fruits is a promising sustainable carbon source for making more economical and efficient electrode material of high performance supercapacitors.

Nanostructured carbon based materials with unique and tunable properties make them to be utilized for various applications in different forms especially for energy and environmental applications. Carbon is a distinctive chemical element which has superior properties such as porous structure, low cost, resistance to basic and acidic conditions, easy accessibility, low density, good recycling properties, more abundant and ability to combine with other chemical elements in different ways. In this review, we have critically assessed the recent developments in carbon based heterostructures for their applications in energy and environment. Special consideration has been paid on the applications in dye-sensitized solar cells, hydrogen evolution reaction, oxygen evolution reaction, Li-ion battery, supercapacitor, photocatalysis for the degradation of organic pollutants, electrochemical/bio sensors and biomedical applications. Finally, the challenges and future developments of carbon based heterostructures for applications in energy and environment are also outlined.

Highly activated porous carbon with attractive and promising electrochemical properties is employed as cathode material for high performance supercapacitors. The present paper proposes a novel activated porous carbon which is derived from zinc-based metal organic framworks as a source and template by carbonization at 825 °C and also further activation with KOH. The obtained activated porous carbon has uniform unique spherical morphology with an average size of 3–5 μm and has a specific surface area up to 2314.9 m2g-1. The activated porous carbon with superior mesoporous structure exhibits a high electrochemical performance and an excellent electrochemical stability in 6 M KOH solution. It provides a high specific capacitance and power density of 325 F g−1 and 71.2 W kg−1, respectively, at a current density of 1 A g−1. Additionally, the activated porous carbon retains its specific capacitance with very slight decay rate of 1.21% after 150,000 cycles at an ultrahigh current density of 50 A g−1. Hence, the present investigation demonstrates that the as-prepared activated porous carbon is a promising candidate as a low-cost and highly efficient electrode material for high-performance supercapacitors.

The influence of hematite iron oxide (α-Fe2O3) nanoparticles in tungsten oxide (WO3) nanorods photocatalyst on photodegradation of organic pollutant was investigated in the present work. The spherical-shaped α-Fe2O3 nanoparticles and WO3 nanorods were synthesized from citrate precursor and hydrothermal routes respectively. The different weight percentage (wt%) ratios (1, 2, and 3 wt%) of α-Fe2O3 added heterostructured α-Fe2O3/WO3 composite photocatalysts by a simple physical mixing process. The photocatalytic activities of as-synthesized photocatalysts were evaluated by photodegradation of methylene blue (MB) under visible-light irradiation. It showed that the 2% α-Fe2O3/WO3 composite exhibited excellent photocatalytic activity than the others. This enhancement could be attributed to its strong absorption in the visible region and the low recombination rate of electron-hole pairs. In addition, the photo-electrochemical measurements of the 2% α-Fe2O3/WO3 composite revealed the faster migration of the photo-excited charge-carriers. Hence, this study demonstrates the heterostructured α-Fe2O3/WO3 composite as a promising candidate for environmental remediation.

Due to controlling CO2 emissions and climate changes from the burning of fossil fuels, the growing renewable energy storage systems are the most crucial tasks for power application. Supercapacitors have gained extensive concentration as green energy storage systems from their rapid charge-discharge, superb power density, inexpensive, less weight, and good long-term stability. However, the large-scale application of supercapacitors is hindered from their low energy density and low stability in strong alkaline solutions. Therefore, it is essential to construct new electrode materials with excellent capacitive and long-term durability. In the past few decades, metal-organic frameworks (MOFs) have been acknowledged as potential porous crystalline materials for energy application ascribed to their large surface area, superb porosity and convenient surface structures. MOFs are also played as excellent carbon sources to achieve highly porous carbon materials. Therefore, in the present review, the modern developments of MOFs-derived porous carbons for supercapacitors are presented in detail. Especially, we focused on the discussion about the preparation of porous carbon from Zn and Al-based MOFs and their noteworthy impact in the supercapacitors applications. At last, we discussed the current challenges and further prospects for the developing MOF-derived carbon materials in order to develop high-performance energy storage devices.

Recycling of waste electrical and electronic equipment (WEEE) reduces the waste of resources, environmental pollution, and human health risks. WEEE recycling involves multiple stakeholders and a complex array of interacting factors that influence the behavior of those stakeholders. Identifying the key influencing factors for these stakeholders helps in the effective development of the WEEE recycling industry. Most previous research has only considered the perspective of consumers, however, this study considered the influencing factors for four key stakeholders: manufacturers, consumers, recyclers and disposers, and the government. The Decision Making Trial and Evaluation Laboratory (DEMATEL) model was used to determine the main factors affecting the typical social recycling behaviors in China. The results show that the most critical influential factor is the government policies that promote WEEE recycling (incentive), whereas the most important centrality factor is the producers that take responsibility for recycling. The disclosure of the environmental product information by manufacturers is the least important influencing factor in the system, which is contrary to conventional understanding. Although the government plays a powerful role, the production, recycling, and processing companies constitute central links in the entire WEEE recycling industry and are therefore important. These results are helpful in formulating relevant policies and affecting the behavior of relevant stakeholders.

The rapid development of photovoltaic (PV) industry has led to increasing emissions of silicon-based solid (SIBS) waste. The discharge of these solid wastes is not only detrimental to the recovery of valuable resources, but also poses a certain threat to the environment. Although some decentralized studies had been conducted on these wastes, either metallurgical silicon slag, waste crucibles, silicon cutting wastes, or EOL photovoltaic panels, few studies had systematically analyzed the comprehensive utilization of SIBS waste from the perspective of whole PV industry. This work firstly reviews the comprehensive utilization status of SIBS waste, and then analyzes the silicon metal value chain related to PV industry. Finally, it concludes the development advantages, risks and challenges in PV industry, and puts forward a few suggestions on closed and/or opened loop recycling of SIBS waste in PV industry chain. From the perspective of entire industrial chain, systematically sorting out the comprehensive utilization of SIBS waste will provide a theoretical reference for the green and sustainable development of PV industry.

In the present investigation, we have synthesized Ni3V2O8@GO composite by co-precipitation method and designed as a new anode material for supercapacitor applications. The phase formation and surface morphology of the Ni3V2O8 and Ni3V2O8@GO composite were confirmed by XRD and FE-SEM measurements, respectively. It was observed that the synthesized Ni3V2O8@GO composite was found to have a small stone-like particle morphology. The electrochemical behavior of Ni3V2O8@GO composite as an electrode material for supercapacitor application was examined by electrochemical techniques. The obtained results showed that the Ni3V2O8@GO composite electrode exhibits maximum specific capacitance value 547 Fg−1 at a scan rate of 5 mVs−1 which was much superior than that of pure Ni3V2O8 (118 Fg−1). The improved electrochemical behavior of the Ni3V2O8@GO composite may be due to its well crystalline nature and also offers more active sites for Faradic reactions, good conductivity, and rapid diffusion of the electrolyte ions. Furthermore, the fabricated Ni3V2O8@GO composite electrode possessed an outstanding cyclic stability and nearly 95% of original specific capacitance value was sustained after 1500 charge-discharge cycles at 5 Ag−1. This indicates that shaped the spherical Ni3V2O8@GO composite possessed excellent electrochemical property that favors it as an auspicious electrode candidates for supercapacitor applications.

Molybdenum disulfide (MoS2), a layered transition metal dichalcogenide with an analogous structure to graphene, has attracted enormous attention worldwide owing to its use in a variety of applications such as energy storage, energy conversion, environmental remediation and sensors. MoS2 and graphene have almost similar functional properties such as high charge carrier transport, high wear resistance and good mechanical strength and friction. However, MoS2 is advantageous over graphene due to its low-cost, abundancy, tailorable morphologies and tuneable band gap with good visible light absorption properties. In this review, we have focussed mainly on recent advances in MoS2 nanostructured materials for the applications in the broad area of energy and environment. Special attention has been paid to their applications in dye-sensitized solar cells, supercapacitor, Li-ion battery, hydrogen evolution reaction, photocatalysis for the degradation of organic pollutants, chemical/bio sensors and gas sensors. Finally, the challenges to design MoS2 nanostructures suitable for energy and environmental applications are also highlighted.

This article presents the effect of hematite phase iron oxide (α-Fe2O3) on the electrocatalytic activity of graphene oxide (GO) for electrochemical detection of hydroquinone in aqueous solution. The different weight percentage (wt%) (1, 2 and 3%) of α-Fe2O3 added GO nanocomposites were synthesized by wet-impregnation method. The cyclic voltammetry studies using 2% α-Fe2O3-GO modified glassy carbon electrodes was found to exhibit an excellent electrocatalytic activity than α-Fe2O3 and GO electrodes that may be due to the synergistic effect of α-Fe2O3nanoparicles and GO sheet. In addition, the modified electrode exhibited a good reproducibility as well as long-term stability. Hence, the 2% α-Fe2O3-GO can be a promising catalytic material for electrochemical sensor applications.

The influence of 5-amino-1,3,4-thiadiazole-2-thiol (ATDT) on the ionic conductivity of poly(vinylidinefluoride-co-hexafluoropropylene) (PVDF-HFP) polymer electrolytes with mixed iodide salts (potassium iodide (KI) and tetrabutylammonium iodide (TBAI)) and iodine (I 2 ) were studied for dye-sensitized solar cells (DSSCs). The pure and different weight percentage (wt%) ratios (2%, 3%, 4%, 5% and 6%) of ATDT modified PVDF-HFP/KI+TBAI/I 2 electrolyte films were prepared by solution casting technique using DMF as a solvent. The polymer electrolyte films were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD), electrochemical impedance spectroscopy and scanning electron microscopy (SEM). The pure PVDF-HFP/TBAI+KI/I 2 electrolyte exhibited the ionic conductivity value of 9.99×10 −6 S cm −1 at room temperature, which was found to be improved to a maximum value of 2.82×10 −4 S cm −1 at 4 wt% of ATDT modified polymer electrolyte. The photovoltaic characterization studies showed higher power conversion efficiency of 4.64% for DSSC assembled with the optimized wt% of ATDT modified polymer electrolyte than the pure PVDF-HFP/KI+TBAI/I 2 electrolyte (1.88%) at an illumination intensity of 60 mW/cm 2 . Hence, the studies concluded that the ATDT modified polymer electrolyte can be a suitable material for DSSC applications.

The influence of g-C3N4 in TiO2 photocatalyst on photodegradation of organic pollutant in aqueous solution has been investigated in the present study. The g-C3N4 was synthesized from low cost urea and used as precursor to synthesize g-C3N4/TiO2 composite by wet impregnation method. The synthesized g-C3N4 and g-C3N4/TiO2 composite photocatalysts were thoroughly characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy. The photocatalytic performance of pure g-C3N4, pure TiO2 and g-C3N4/TiO2 composite photocatalysts were evaluated for the photodegradation of acid orange 7 (AO7) under visible light irradiation. The photocatalytic experiments demonstrated that the g-C3N4/TiO2 composite photocatalyst showed much better photocatalytic degradability of AO7 than the pure TiO2 and g-C3N4. This may be due to the increased absorption of light in the visible region and also by a lower recombination of charge-carriers. Further, the photoelectrochemical measurements of g-C3N4/TiO2 revealed the faster migration of photo-induced charge-carriers. This study demonstrates that g-C3N4/TiO2 composite can be a good candidate for environmental remediation of polluted waters.

The various carbon-based materials incorporated nickel sulfide (NiS) composites have been electrochemically deposited on fluorine-doped tin oxide (FTO) glass substrate. The structure, surface morphology, and elemental composition of the electrodeposited NiS composite materials were characterized by XRD, HR-SEM, and EDS. The electrochemically deposited various NiS composites such as NiS/AB (acetylene black), NiS/VC (Vulcan carbon), and NiS/MWCNT (multi walled carbon nanotubes) have been served as an efficient, low-cost counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). Electrochemical impedance spectroscopy and cyclic voltammetry of NiS/AB CE composite materials exhibits a good conductivity and superior electrocatalytic performance over other various carbon incorporated materials. The positive synergistic effects, which increase the active catalytic sites and improved interfacial charge transfer, may be accountable for the superior electrocatalytic performance of NiS/AB composite materials The fabricated DSSC with NiS/AB CE reached a power conversion efficiency of 6.75%, which is equivalent with platinum electrode (7.20%). These results validate that the electrochemically deposited NiS/AB composite film is an auspicious alternative for low-cost and high efficient DSSCs.

Nanowire-shaped α-MoO3 was synthesized on a large scale by hydrothermal route. Nanocrystalline α-Mo2C phase was obtained by the carburization of α-MoO3 nanowires with urea as a carbon source precursor. The phase purity and crystalline size of the synthesized materials were ascertained by using powder X-ray diffraction. The shape and morphology of synthesized materials were characterized by field-emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). The electrocatalytic activity of α-Mo2C for I−/I3− redox couple was investigated by the cyclic voltammetry. The synthesized α-Mo2C was subsequently applied as counter electrode in dye-sensitized solar cells to replace the expensive platinum.

Zinc oxide (ZnO) is an adaptable material that has distinctive properties, such as high-sensitivity, large specific area, non-toxicity, good compatibility and a high isoelectric point, which favours it to be considered with a few exceptions. It is the most desirable group of nanostructure as far as both structure and properties. The unique and tuneable properties of nanostructured ZnO shows excellent stability in chemically as well as thermally stable n-type semiconducting material with wide applications such as in luminescent material, supercapacitors, battery, solar cells, photocatalysis, biosensors, biomedical and biological applications in the form of bulk crystal, thin film and pellets. The nanosized materials exhibit higher dissolution rates as well as higher solubility when compared to the bulk materials. This review significantly focused on the current improvement in ZnO-based nanomaterials/composites/doped materials for the application in the field of energy storage and conversion devices and biological applications. Special deliberation has been paid on supercapacitors, Li-ion batteries, dye-sensitized solar cells, photocatalysis, biosensors, biomedical and biological applications. Finally, the benefits of ZnO-based materials for the utilizations in the field of energy and biological sciences are moreover consistently analysed.

Presently, the porous carbon derived from natural biomass wastes hold a prominent position as electrode material in supercapacitors from its wonderful features of huge surface area, cost-effectiveness, freely available precursor, easy to preparation and eco-friendly nature. Thus, in the present study, we propose a new hollow tubular-like porous carbon (HT-PC) from the more sustainable and freely available feather finger grass flower (FFGF) with high electrochemical behavior as an active electrode for supercapacitors. The combination of carbonization and KOH activation treatments were carried out to prepare HT-PC from natural FFGF. The as-prepared biomass HT-PC containing the different sized micro-pore arrangement with a huge surface area (637.1 m2 g−1) after performed KOH activation treatment at the optimized condition. The three-electrode system measurements reveal that as-prepared HT-PC provides a remarkable specific capacitance of 315 F g−1 at 1 A g−1 and 262 F g−1 at 100 A g−1 with keeping 96% of capacitance over 50,000 cycles at 50 A g−1 using 6 M KOH aqueous electrolyte. In addition to that, the HT-PC electrode-based symmetrical supercapacitor releases high specific energy of 18.75 Wh kg−1 at 0.37 kW kg−1 with losing 30% of capacitance over 10,000 cycles at 10 A g−1 using 6 M KOH electrolyte. Meanwhile, the symmetrical supercapacitor shows a good specific energy of 13.18 Wh kg−1 at 0.61 kW kg−1 without losing any capacitance over 10,000 cycles at 10 A g−1 using 1 M Et4NBF4/AN electrolyte. This study is verified that the naturally available FFGF is a talented sustainable carbon source to make more economical and effective carbon electrodes for supercapacitors.

In recent times, silver (Ag) based semiconductors have been gained a lot of attention as photocatalysts for industrial waste-water treatment owing to their strong visible-light absorbing capability and small bandgap energy. Therefore, herein, we have designed and utilized a one-pot hydrothermal approach to the synthesis of nano-sized AgBr covered potato-like Ag2MoO4 composite photocatalysts for the elimination of organic wastes from the aquatic environment. To achieve a high-performance photocatalyst, a sequence of AgBr/Ag2MoO4 composites were acquired with varying CTAB from 1 to 4 mmol. Furthermore, the photocatalytic activity of these photocatalysts was confirmed from decomposing of Rhodamine B (RhB) dye via visible-light elucidation. It can be noticed that AgBr/Ag2MoO4 composites exhibited significantly increased photocatalytic behaviour as compared with pure AgBr and Ag2MoO4. Surprisingly, the AgBr/Ag2MoO4 composite obtained from 2 mmol CTAB was eliminated the entire RhB dye with 25 min. Also, the recycling experiment indicates the AgBr/Ag2MoO4 composite has an excellent photo-stability. Accordingly, the as-acquired AgBr/Ag2MoO4 composite would be a suitable photocatalytic material for industrial waste-water purification.

Recently, the naturally available biomass wastes are received considerable attention as an appropriate carbon precursor to making low-price, sustainable, and environmental friendly porous carbon for supercapacitors. In this study, we have derived a tubular-like porous carbon (TPC) from natural waste American poplar fruit as a carbon precursor via simple carbonization and KOH activation processes. The derived TPC exhibits an impressive tubular-like framework with extremely arranged porous structures and an enhanced surface area of 942 m2 g−1. Besides, the TPC exhibits superior specific capacitance (SC) (423 F g−1 at 1 A g−1) and rate ability (remained 217 F g−1 of SC still at 200 A g−1). It also has very-extensive cyclic life with only loss 3% of SC after 200,000 cycles still at 200 A g−1. The as-fabricated symmetrical cell under 6 M KOH offered a noteworthy SC of 58.71 F g−1 at 1 A g−1, superb specific energy of 7.99 Wh kg−1 at 372 W kg−1 as well as outstanding cyclic durability with preserved 80.2% of SC after 10,000 cycles at 10 A g−1. Meanwhile, the symmetrical cell under 1 M Et4NBF4/AN electrolyte expressed an increased SC of 31.68 F g−1 at 1 A g−1, high specific energy 13.75 Wh kg−1 at 624 W kg−1 as well as excellent cyclic durability with preserved 60.5% of SC after 10,000 cycles at 10 A g−1. Thus, the present work recommends that waste American poplar fruit is a sustainable carbon source for production of hierarchical porous carbon for energy storage device applications.

This work describes the effect of 2-aminopyrimidine (2-APY) on poly(vinylidinefluoride- co -hexafluoropropylene) (PVDF-HFP)/polyethylene oxide (PEO) blend polymer electrolyte along with binary iodide salts (tetrabutylammonium iodide (TBAI) and potassium iodide (KI)) and iodine (I 2 ) were studied for enhancing the efficiency of the dye-sensitized solar cells (DSSCs) consisting of g-C 3 N 4 /TiO 2 composite as photoanode. The g-C 3 N 4 was synthesized from low cost urea by thermal condensation method. It was used as a precursor to synthesize the various weight percentage ratios (5%, 10% and 15%) of g-C 3 N 4 /TiO 2 composites by wet-impregnation method. The pure and 2-APY incorporated PVDF-HFP/PEO polymer blend electrolytes were arranged by wet chemical process (casting method) using DMF as a solvent. The synthesized g-C 3 N 4 /TiO 2 composites and polymer blend electrolytes were studied and analyzed by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The ionic conductivity values of the pure and 2-APY incorporated PVDF-HFP/PEO blend electrolytes were estimated to be 4.53×10 −5 and 1.87×10 −4 Scm −1 respectively. The UV–vis absorption spectroscopy was carried out for the pure and different wt% of g-C 3 N 4 /TiO 2 composites coated FTO films after N3 dye-sensitization. The 10 wt% g-C 3 N 4 /TiO 2 composite film showed a maximum absorption compared to the others. The DSSC assembled with 10 wt% g-C 3 N 4 /TiO 2 as photoanode using the pure polymer blend electrolyte exhibited a power conversion efficiency (PCE) of 3.17% , which was superior than that of DSSC based pure TiO 2 (2.46%). However, the PCE was increased to 4.73% for the DSSC assembled using 10 wt% g-C 3 N 4 /TiO 2 as photoanode with 2-APY incorporated polymer blend electrolyte. Hence, the present study is a successful attempt to provide a new pathway to enhance the performance of DSSCs.

A flower-like molybdenum disulfide microspheres and various carbon materials (acetylene black, vulcan carbon, multi-walled carbon nanotubes, carbon nanofibers, and rice husk ash) incorporated MoS2 microsphere materials were synthesized via convenient single-step hydrothermal method. The obtained MoS2/C materials provide cost-effective and Pt free counter electrodes for DSSCs. Phthaloylchitosan-based polymer electrolyte was used as an electrolyte for DSSCs. The phase formation and purity of the synthesized materials were ascertained by powder X-ray diffractometer. The shape, morphology, and the distribution of the carbon materials in MoS2 microspheres were examined by electron microscope measurements. The electrochemical measurements were revealed that the carbon materials incorporated MoS2 electrode hold low charge transfer resistance at the counter electrode/electrolyte interface and demonstrate high electrocatalytic activity for the reduction of I3 − to I−ions. Among different carbon materials studied, MoS2 doped on CNF offered a positive synergistic effect for the electrocatalytic reduction of I3 −. The DSSC fabricated with MoS2/CNF CE and phthaloylchitosan-based polymer electrolyte shown a high power conversion efficiency of 3.17 %, whereas pure MoS2 CE showed only 1.04 %. The present study validates the application of carbon incorporated MoS2 as a potential CE in DSSCs.

In this work, we have investigated the influence of guanine as an organic dopant in dye-sensitized solar cell (DSSC) based on poly(vinylidinefluoride-co-hexafluoropropylene) (PVDF-HFP)/polyethylene oxide (PEO) polymer blend electrolyte along with binary iodide salts (potassium iodide (KI) and tetrabutylammonium iodide (TBAI)) and iodine (I2). The PVDF-HFP/KI + TBAI/I2, PVDF-HFP/PEO/KI + TBAI/I2 and guanine incorporated PVDF-HFP/PEO/KI + TBAI/I2 electrolytes were prepared by solution casting technique using DMF as solvent. The PVDF-HFP/KI + TBAI/I2 electrolyte showed an ionic conductivity value of 9.99 × 10−5 Scm−1, whereas, it was found to be increased to 4.53 × 10−5 Scm−1 when PEO was blended with PVDF-HFP/KI + TBAI/I2 electrolyte. However, a maximum ionic conductivity value of 3.67 × 10−4 Scm−1 was obtained for guanine incorporated PVDF-HFP/PEO/KI + TBAI/I2 blend electrolyte. The photovoltaic properties of all these polymer electrolytes in DSSCs were characterized. As a consequence, the power conversion efficiency of the guanine incorporated PVDF-HFP/PEO/KI + TBAI/I2 electrolyte based DSSC was significantly improved to 4.98% compared with PVDF-HFP/PEO/KI + TBAI/I2 electrolyte based DSSC (2.46%). These results revealed that the guanine can be an effective organic dopant to enhance the performance of DSSCs.

Ternary metal selenides of (Ni1−xCox)Se2 with 0≤x≤1 were synthesized by using one-step hydrothermal reduction route. The synthesized metal selenides were utilized as an efficient, low-cost platinum free counter electrode for dye-sensitized solar cells. The cyclic voltammetry and electrochemical impedance spectroscopy studies revealed that the Ni0.5Co0.5Se2 counter electrode exhibited higher electrocatalytic activity and lower charge transfer resistance at the counter electrode/electrolyte interface than the other compositions for reduction of triiodide to iodide. Ternary selenides of Ni0.5Co0.5Se2 offer a synergistic effect to the electrocatalytic activity for the reduction of triiodide that might be due to an increase in active catalytic sites and small charge transfer resistance. The DSSC with Ni0.5Co0.5Se2 counter electrode achieved a high power conversion efficiency of 6.02%, which is comparable with that of conventional platinum counter electrode (6.11%). This present investigation demonstrates the potential application of Ni0.5Co0.5Se2 as counter electrode in dye-sensitized solar cells.