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Mixed phase of iron telluride based thin films consisting of nanopebbles has been grown successfully over conducting stainless steel (SS) substrate through successive ionic layer adsorption reaction (SILAR) process. Crystal structural and elemental states through XPS revealed clear indication of FeTe: Fe2TeO5 mixed phase growth and well supported through FTIR studies. Agglomeration of embedded quantum dots forming nanopebbles like surface architecture resulting in enhanced hydrophilic nature evident through contact angle and higher surface roughness by atomic force micrographs found beneficial as more electroactive surface area for electrolyte ions to interact. This helped to achieve a significant specific capacitance of 591 F/g (166 mF/cm2) @3 mV/s potential scan rate and, 107 F/g (30 mF/cm2) @0.4 mA/cm2 in NaCl electrolyte. Performed electrochemical impedance spectroscopy (EIS) studies explored clear insight of the solution and charge transfer resistances, and relaxation time constant. Iron telluride based thin film clearly demonstrates very high value of pseudo capacitive contribution than the electric double layer due to the intrinsic pseudocapacitive behavior of mixed phase.

First-ever designed symmetric Ni3P2O8 flexible all-solid-state symmetric supercapacitor operating at 1.8 V with neutral gel electrolyte.

One-dimensional iron hydroxide@cadmium hydroxide nanostructures have been prepared by sequentially converting cadmium hydroxide into iron hydroxide via simple and cost-effective cation exchange reaction based on solubility product to design electrochemical supercapacitive electrode. Surface architecture of iron hydroxide@cadmium hydroxide nanostructures in the form of core–shell enables easy and effective electrochemical reactions which have been studied via electrochemical cyclic voltammetry and charge–discharge studies. Interestingly, iron hydroxide@cadmium hydroxide electrode exhibits specific capacitance of 368 F g−1 at current density of 0.5 A g−1 along with electrochemical impedance analysis. Capacitance retention performed at the scan rate of 50 mV s−1 for 5000 cycles results in 52% capacity of its initial.

Design of nanostructured surface architecture is currently playing a vital role to enhance the energy storage capability of electrode materials and opening up a new era for future technologies through electrochemical supercapacitors. Present effort portrays the growth of nanostructured bismuth vanadate (BiVO4) as an active electrode for supercapacitor application by using ease and industry scalable successive ionic layer adsorption and reaction (SILAR) method. Structural analysis reveals the development of orthorhombic structured BiVO4 with spongy nano-pebbles like surface architecture. Synthesized BiVO4 electrode yields remarkable capacitance of 707 F/g @3 mV/s scan rate. Faradaic and capacitive type contributions have been evaluated for in-depth understanding along with the estimation of electrochemical active surface area. Electrochemical impedance spectroscopy (EIS) analysis of BiVO4 electrode exhibits 5.723 and 0.89 Ω cm2 values of series and charge transfer resistances, respectively. Interestingly, BiVO4 electrode delivers outstanding capacitive retention of 102% even at 3500 cycles, indicating its potential candidature for the advancement in high capability supercapacitors with excellent stability for the future technologies.

Increasing demand for microelectronic devices necessitates the development of highly flexible energy storage technologies with a wide operating voltage. Thus, flexible electrodes and their devices with the requisite mechanical and electrochemical characteristics have prime importance. In this regard, the present article demonstrates the feasibility of designing a flexible all-solid-state supercapacitor using a chemically grown Ni

Simple, binder free, low-cost chemical route has been employed to design CdSe@PbS core-shell surface architecture in thin film form towards electrochemical supercapacitor application. Horizontal chemical bath deposition (H-CBD) was used to grow one-dimensional (1D) Cd(OH)2 nanowires (NWs) template followed by ion exchange to get 1D CdSe NWs. Further, PbS nanoparticles were encapsulated on the surface of CdSe nanowires by using successive ionic layer adsorption and reaction (SILAR) method. Structural, compositional, and morphological studies have been used to confirm and investigate obtain surface architecture. Interestingly, design CdSe@PbS core-shell surface architecture not only offer maximum active sites but also provide smooth and fast electron transfer path exhibiting significant electrochemical performance with a specific capacity of 82 mAh g-1 and improved long-term stability. Additionally, symmetric electrochemical supercapacitor device of CdSe@PbS exhibits noticeable energy density of 16.14 Wh kg-1 at the power density of 288 W/kg.

World-wide increased energy consumption and demand has made the need for high-energy storage systems with longer life critical. Hence, extensive research and development on supercapacitors based on efficient and robust electrode materials are being carried out. Many materials based on metal oxides, polymers, carbon-based materials, metal chalcogenides, and their composites have been explored to reach saturation to obtain the milestone capacitance value and hence, energy density. Recently, metal phosphides (MPs) have arisen as a unique class of potential candidates for high performance supercapacitors owing to their inherent semi-metallic nature and high electrical conductivity. Aid of fascinating properties, MPs has driven to reach demarcation outlined by champion metal oxides based electrodes for supercapacitor applications. We systematically reviewed the phosphides family including the phosphides of nickel, cobalt, iron, and copper to give a clear understanding in terms of their versatile applications in supercapacitors. Aside from mono-metal phosphides, an extensive analysis of the literature about multi-metal phosphides with combined benefits from two or more metal species has been explored. To further exploit their interesting properties, MPs have been integrated with other functionally active materials to form binary composites or even ternary composites. The present review article concentrates on modern research findings in the synthetic routes of nanostructured MPs in correlation with the structures, morphologies, and their electrochemical energy storage performances. Subsequently, the importance of strong synergistic effects existing in MP-based nanocomposites is highlighted along with some representative works on the fabrication of symmetric/asymmetric supercapacitor devices. Finally, the current challenges and future opportunities in real energy technology device applications of MPs are proposed.

In the class typical layered metal chalcogenide family, tin selenide (SnSe) has been explored resolutely as one of the significant binary IV-VI compounds for a wide range of energy storage applications. Two dimensional hexagonal tin selenide nanosheets have been synthesized using a one-pot colloidal method and tested as active electrode for supercapacitors without using any binder. The as-prepared SnSe electrode exhibits a capacitance of 617.9 F/g at a scan rate of 2 mV/s with a good electrochemical stability due to efficient ion transport between electrolyte to active electrode and charge transport between electrode and current collector. The high energy density of 28.5 Wh/kg along with high cyclic stability is due to the morphology assisted electrochemical activity of the electrode. The results indicate that the assembly of binder-free electrode by the proposed facile synthesis route has a promising application in producing high-performance energy storage devices.

We report the synthesis of two-dimensional porous ZnO nanosheets, CuSCN nanocoins, and ZnO/CuSCN nano-heterostructure thin films grown on fluorine-doped tin oxide substrates via two simple and low-cost solution chemical routes, i.e., chemical bath deposition and successive ionic layer adsorption and reaction methods. Detail characterizations regarding the structural, optoelectronic, and morphological properties have been carried out, which reveal high-quality and crystalline synthesized materials. Field emission (FE) investigations performed at room temperature with a base pressure of 1 × 10–8 mbar demonstrate superior FE performance of the ZnO/CuSCN nano-heterostructure compared to the isolated porous ZnO nanosheets and CuSCN nanocoins. For instance, the turn-on field required to draw a current density of 10 μA/cm2 is found to be 2.2, 1.1, and 0.7 V/μm for the ZnO, CuSCN, and ZnO/CuSCN nano-heterostructure, respectively. The observed significant improvement in the FE characteristics (ultralow turn-on field of 0.7 V/μm for an emission current density of 10 μA/cm2 and the achieved high current density of 2.2 mA/cm2 at a relatively low applied electric field of 1.8 V/μm) for the ZnO/CuSCN nano-heterostructure is superior to the isolated porous ZnO nanosheets, CuSCN nanocoins, and other reported semiconducting nano-heterostructures. Complementary first-principles density functional theory calculations predict a lower work function for the ZnO/CuSCN nano-heterostructure (4.58 eV), compared to the isolated ZnO (5.24 eV) and CuSCN (4.91 eV), validating the superior FE characteristics of the ZnO/CuSCN nano-heterostructure. The ZnO/CuSCN nanocomposite could provide a promising class of FE cathodes, flat panel displays, microwave tubes, and electron sources.

Enhancing energy storing capability with the aid of unique nanostructured morphologies is beneficial for the development of high performance supercapacitors. Developing earth abundant and low-cost transition metal selenides (TMSs) with enhanced charge transfer capabilities and good stability is still a challenge. Herein, state of the art for iron selenide with a nanoflake surface architecture, synthesized with the aid of a simple, industry-scalable and ionic layer controlled chemical approach, namely the successive ionic layer adsorption and reaction (SILAR) method, is presented. The iron selenide electrode yields a capacitance of 671.7 F g−1 at 2 mV s−1 scan rate and 434.6 F g−1 at 2 mA cm−2 current density through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) studies, respectively, with 91.9% cyclic retention at 4000 cycles. The developed bendable solid-state supercapacitor reveals a remarkable power density of 5.1 kW kg−1 with outstanding deformation tolerance, including its use in a practical demo to run a small fan, demonstrating its capability for advanced energy storage applications. A complementary first-principles density functional theory (DFT) approach is used in combination with the experimental supercapacitive performance to achieve an understanding of the electronic structure.

Cadmium sulphide and titanium dioxide-based junctionless transistor (JLT) has been demonstrated by using simple and low-cost chemical bath deposition method. The morphological and structural study has been performed to speculate the crystallinity and the topography of individual layers of the proposed device. The optimised sputtering conditions lead to the formation of source and drain electrical contacts of the device. The fabricated device successfully functionalised as a p-channel JLT. At the source-to-drain voltage of −50 V, the ON-state drive current and OFF-state leakage current of the fabricated JLT are found to be −6 µA and 1.3 nA, respectively.

Thin film consisting of hierarchical cadmium oxide nanonecklaces has been synthesized through room temperature chemically deposited cadmium hydroxide nanowires as template followed by air annealing. Formation of thin film has been confirmed with aid of structural, surface morphological, valence state and optical, studies performed by X-ray diffraction, Raman analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV–visible spectroscopy. Air annealing at 330 °C has enhanced the photo electrochemical power conversion efficiency of the CdO as photoanode to 0.21% configured through platinum as counter electrode and polyiodide as a liquid electrolyte. Complete device performance have been correlated through rate of recombination, and electron life time. The schematic energy band alignment also has been comprehended herein.

An investigation of field emission on solution processed MWCNTs, MoS2 and MoS2 anchored MWCNTs thin films on low cost stainless steel substrates have been performed. Decorative morphology of MoS2 nanoflakes over MWCNTs interconnected high surface area nanonetwork supports the active path for the application of field emission. Drastic diminishing in turn-on field value has been obtained for MWCNTs/MoS2 nanocomposite compared to bare MWCNTs and MoS2. Hence, present investigation opens path for the development of low-temperature solution processed MWCNTs/MoS2 thin film in the field of nanoelectronics and the used process can be integrated for large scale.

A complete solid state device with FTO/PANI/PTh/ZnO/Al assembly prepared by absolute wet chemical methods including chemical bath deposition (CBD), successive ionic layer adsorption and reaction (SILAR) and spin coating has been studied to investigate the effect of thickness of active PANI layer on device performance. Structural, morphological and chemical bond features have been investigated by using X-ray diffraction, Field Emission Scanning Electron Microscopy and Fourier Transform Infrared spectroscopy of the layers and are discussed herein. Effect of PANI thickness on current-voltage characteristic has been studied under dark and illumination (100 mW/cm2, AM 1.5G, 1 Sun) condition to know the solar cell performance.

Present work portrays the surface morphology dependent electrochemical behaviors tuned by annealing the chemical bath deposited (CBD) cerium oxide electrodes. The altered nanostructure properties are well-supported by in-depth structural and morphological analysis. Cerium oxide electrode annealed at 200 °C exhibits good surface properties enabling maximum electro-active porous cavities to penetrate electrolyte ions towards enhanced electron transfer. Consequently, the electrode exhibits maximum specific capacitance of 750 F/g with remarkably stable charge-discharge cycles. Fabricated symmetric solid-state supercapacitor device impressively expands potential window to 1.2 V with the aid of PVA-LiClO4 gel electrolyte with a peak specific capacitance of 321.3 F/g with top-up of 61.4 Wh/kg specific energy. The series combination of two devices confirms the strong energy storage ability by glowing ‘VNIT’ acronym designed through 21 red LEDs from the practical point of view.

The fiber wrapped tuberose structured Fe:Sr(OH)2 have been successfully deposited by using a simple and low cost chemical approach of successive ion layer adsorption and reaction (SILAR) method as binder-free electrodes for supercapacitors. The structural properties have been obtained by the XRD patterns, while FTIR shows the chemical bond analysis. The FE-SEM micrographs show fiber wrapped tuberose structured morphology and the Fe doping into Sr(OH)2 is confirmed by EDX. The deposited films show the battery type electrode behaviour in 1 M Na2SO4 aqueous solution. As an active electrode material, the specific capacity of 871 C g−1 (specific capacitance of 792 F g−1) at 1.2 mA cm−2 with cycle retention of ∼79% at 5 mA cm−2 has been obtained for 0.5 at.% Fe:Sr(OH)2. The electrochemical properties of the synthesised electrode reveal that it has the great potential for next-generation energy storage applications.

Portable and furnished electronics appliances demand power efficient energy storage devices where electrochemical supercapacitors gain much more attention. In this concern, a simple, low-cost and industry scalable successive ionic layer adsorption and reaction (SILAR) approach has been adopted to deposit nanostructured VS2 onto flexible and light-weight stainless steel (SS) substrate towards supercapacitor application. The nanocrystalline nature with hexagonal crystal structure has been confirmed for VS2 through structural analysis. The VS2 electrode exhibits a maximum specific capacitance of 349 F g−1 with a super stable behavior in three-electrode liquid-state configuration. Fabricated flexible symmetric solid-state supercapacitor (FSSC) device using gel electrolyte yields specific power of 1.5 kW kg−1 (specific energy of 25.9 Wh kg−1) with a widen voltage window of 1.6 V. A red LED has been glown for 30 s using the system consisted of two devices in series combination. Furthermore, the system glows a combination of 21 red LEDs network with acronym ‘VNIT’, demonstrating commercial exposure. The attribution of device demonstration even under mechanical stress holds great promise towards advanced flexible electronics application.

Through simple chemical route, nanoheterojunction has been developed between CdS-nanowires (NWs) as core with PbS nanoparticles as a shell for photoelectrochemical solar cell application. The use of simple, cost effective and industry scalable chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR) approaches for the deposition of CdS NWs and PbS nanoparticles, respectively has the added advantage. Well-tuned nano particle size of PbS through number of SILAR cycles over wide band gap CdS resulted into optical red shift which maximize the absorption region of solar spectrum responsible for yielding enhancement in light conversion efficiency than bare CdS. Device configured solar cell yields 15 fold enhancement in the power conversion efficiency in liquid configuration due to the well aligned nanoheterojunction between CdS and PbS analysed through photoelectron X-ray spectroscopy. This enhancement in efficiency has been correlated through flat band potential, electron life time, rate of recombination and external quantum efficiency.

Rectangular shaped α-Ce2S3 microrods have been grown with the aid of a facile, efficient, low cost and low temperature chemical bath deposition (CBD) approach in thin film form. Characterizations of α-Ce2S3 have been performed through structural, morphological and surface wettability studies. Intermixed rectangular microrods with lower contact angle provide a reduction in intrinsic resistance and effective ion diffusion path during electrochemical activities ensuring maximum utilization of the active electrode species. This leads to achieve a remarkable specific capacitance of 726 F/g at 2 mV/s scan rate with the excellent electrochemical stability of 93% at 2000 CV cycles. Efficient electrochemical findings exhibit excellent scope of α-Ce2S3 towards next-generation energy storage devices.

Sensors to detect the leakage of hazardous gases are indispensable to avoid accidental problems for human health. Sensors become part of industrial application and day-to-day life. Design and development of gas sensor need wide range of materials where the use of semiconducting metal oxide is on prime priority owing to its inherent exceptional chemical and physical properties and simple route of preparation through less expensive methods. Liquefied petroleum gas (LPG) is injurious to human health due to its explosive and inflammable properties. The extensive use of LPG generated a room for encroachment of sensitive and cost-effective gas sensors which can sense leakage before any severe calamities can occur. Research on sensing materials are currently aimed extensively on nanostructured materials of metal oxide semiconductor with numerous surface architectures in nano forms having their sizes in nano regime, namely, quantum dots, nanobelts, nanotubes, nanoparticles, nanowires, and nanorods due to abrupt change in conductivity under gas environment. High surface-to-volume ratios in addition to huge quantity of active sites associated with nanostructured architecture help to achieve maximum sensitivity when exposed to gas. Present chapter deals with chemically processed heterojunction-based metal oxide material towards room temperature LPG sensors with primary emphasis given on fundamental properties, basic mechanism with design and operation, recent progress, and future trends. Particularly, the chapter points out the state of the art towards the advancement in LPG sensors centered on semiconducting metal oxides with heterostructure properties. Furthermore, the comprehensive illustrations on heterojunction gas sensors based on metal oxides open up new directions for further exploration on room temperature LPG sensors.

Next-generation portable flexible electronic appliances require liquid-free energy storage supercapacitor devices to eliminate leakage and to support mechanical bending that is compatible with roll-to-roll technologies. Hence, a state-of-the-art process is presented to design a solid-state, wide-potential and flexible supercapacitor through the use of nano-pebbles of cerium selenide via a simple successive ionic layer adsorption and reaction (SILAR) method that could allow an industry scalable route. We strongly believe that this is the first approach amongst physical and chemical routes not only for synthesizing cerium selenide in thin-film form but also using it for device-grade supercapacitor applications. The designed solid-state symmetric supercapacitor assembled from cerium selenide electrodes sandwiched by PVA–LiClO4 gel electrolyte attains a wide potential window of 1.8 V with capacitance of 48.8 F g−1 at 2 mV s−1 and reveals excellent power density of 4.89 kW kg−1 at an energy density of 11.63 W h kg−1. The formed device is capable of 87% capacitive retention even at a mechanical bending angle of 175°. Lighting up a strip of 21 parallel connected red LEDs clearly demonstrates the practical use of the designed symmetric solid-state supercapacitor, aiming towards the commercialization of the product in the future. The authors gratefully acknowledge DST/TMD/MES/2k16/09 project, Government of India.

Design and development of cadmium sulphide core with silver sulphide shell assembly in nanowire (NWs) surface architecture has been explored through room temperature, simple chemical route towards photoelectrochemical solar cell application. Incorporation of low band gap Ag2S nanoparticles over the outer surface of the chemical bath deposited CdS NWs has been achieved by simple cation exchange route based on negative free energy of formation. Shell optimization has been performed by investigating structure, surface morphologies and optical analyses and correlated with the photovoltaic parameters. Interestingly, core-shell CdS NWs/ Ag2S exhibits 1.5 better performance in terms of linear voltammetry, photocurrent transient response and the photo stability than bare CdS. Furthermore, three-fold enhancement in photoelectrochemical conversion efficiency have been observed for optimized FTO/ CdS NWs/Ag2S compared to bare FTO/CdS NWs due to the augmented light harvesting and condensed charge recombination. External quantum efficiency exhibits 24% for the optimized CdS NWs/ Ag2S core shell structure. Mott-Schottky and electrochemical impedance spectroscopy measurements have been used for better understanding the impact of gradual growth of Ag2S over CdS NWs which directly influences the overall photocurrent density of the devices.

Anchoring of vanadium telluride (VxTey) nanoparticles onto the exterior layer of multi-walled carbon nanotubes (MWCNTs) has been successfully employed at room temperature (300 K) as first report by using successive ionic layer adsorption and reaction (SILAR) to yield VxTey/MWCNTs surface architecture. Mutualistic contribution from ion insertion/extraction introduced non-stoichiometric vanadium telluride with electric double-layer involved MWCNTs have been unified to enrich excellent electrochemical performance. Three-electrode system configured VxTey/MWCNTs electrode yields 16-fold enhancement in specific capacitance compared to the bare MWCNTs electrode. Achieved performance forced us to construct flexible solid-state supercapacitor device (FSS-SC). Symmetric electrode embedded with PVA-LiClO4 gel mediator harvests remarkable 2 V voltage window to gain 34.5 Wh/kg energy density and 0.7 kW/kg power density. Cycling over 10000 replications confirms the pronounced (82.5 %) stability of designed device and growing LED enables practical evidence; demonstrating its capacity as efficient energy storage device. Correlated density functional theory (DFT) has been manifested to confirm synergistic interactions between the VxTey and MWCNTs, and a corresponding enhancement in the electron density at the Fermi level of VxTey/MWCNTs describes the insight origin for enhanced supercapacitance.

Well controlled growth of pseudocapacitive nanostructured silver selenide (Ag2Se) thin film has been achieved through simple, less expensive, room temperature and industry scalable successive ionic layer adsorption and reaction (SILAR) onto stainless steel substrate to use as electrode material for supercapacitor application as the first report. X-ray photoelectron spectroscopy studies confirmed the formation of Ag2Se. Orthorhombic structure of grown Ag2Se thin film exhibits hydrophilic nature in aqueous Na2SO3 electrolyte yielding specific capacitance of 112.45 F/g @ 10 mV/s scan rate studied through cyclic voltammetry (CV) and 115.99 F/g @ 0.8 A/g by galvanostatic charge discharge through electrochemical studies. Interestingly Ag2Se electrode exhibits 85.10% capacitive retention after 2000 CV cycles. Origin of net-charge stored at the electrode-electrolyte interface has been well understood from surface induced capacitive and diffusion-controlled mechanisms. Low equivalent series resistance (ESR) value of 0.061 Ω was determined by the plot of iRdrop vs. current density exhibiting high-power burst electrode material.

Present innovation emphasizes the design and development of hybrid nanoarchitecture by using simple two-step chemical routes, namely, “dip and dry”, for multiwalled carbon nanotubes (MWCNTs) follow...

Supercapacitors as one of the most important energy storage devices have been receiving worldwide attention due to their high capacitance, power density, long cycle life, and rapid charge/discharge rates as compared to conventional electrolytic capacitors and rechargeable batteries. A nanocomposite has been prepared using mercury sulfide (HgS) and multiwalled carbon nanotubes (MWCNTs) via novel, simple, and low-cost ‘dip and dry’ process followed by successive ionic layer adsorption and reaction (SILAR) method. The association of HgS nanoparticles with high surface area reinforced MWCNTs nanonetwork boosts the electrochemical supercapacitive performance of nanocomposite compared to bare HgS and MWCNTs. This nanocomposite yields excellent specific capacitance of 946.43 F/g at scan rate of 2 mV/s and an outstanding rate capability of 93% retention over 4000 cycles with decent charge–discharge cycles. Moreover, the electrode exhibits maximum specific energy and power densities of 42.97 Wh/kg and 1.60 kW/kg, respectively. The promising capabilities of formed nanocomposite can explore the opportunities as alternative electrode material for energy storage applications.

Recently, thin-film supercapacitors have received much interest because they can achieve both high energy densities and high power densities, which make them suitable for practical applications. Here, thin films consisting of zinc ferrite (ZnFe2O4) anchored on multiwalled carbon nanotubes (CNT) were prepared through a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method. This method has the advantage of direct electrode formation without the use of any binder. The synergy of the composite electrode (ZnFe2O4-CNT) yields a high specific capacity of 217 mAhg(-1) at 5 mVs(-1), which is realized by contributions from the inner and outer active surfaces of the hybrid ZnFe2O4-CNT electrode. Furthermore, a solid-state symmetric device exhibits a highest specific energy of 12.80 Whkg(-1) and a specific power of 377.86 Wkg(-1), which clearly demonstrates that our hybrid ZnFe2O4-CNT electrode is promising and innovative for energy-storage applications.