Energy Materials and Devices

Over the last few decades, lithium-ion batteries (LIBs) have dominated the market of energy storage devices due to their wide range of applications ranging from grid–scale energy storage systems to electric vehicles (EVs). However, the increasing demand for sustainable energy sources and scarcity of lithium draws attention to other alternatives, such as Sodium-ion batteries (SIBs). SIBs are potential candidates for sustainable energy storage devices due to their high natural abundance and low cost of Na-based materials. However, the low specific capacity of standard cathodes and the poor cycle life of Na-rich cathodes still limit the practical application of SIBs for high-energy applications. This review summarizes the challenges and recent progress in the development of Na-rich layered cathode materials. We highlight some of the critical parameters that modulate the anionic redox in high-capacity Na-ion batteries. This review provides the present state of understanding and is expected to be helpful for the future design and development of improved Na-based cathode materials for high-energy applications.

In any electrochemical energy storage system capacity fading is a crucial concern and poses challenges to their long-term stability for any practical uses. There are various characterization techniques for understanding the electrode material, yet it is difficult to nail down the microscopic regions of failure. X-ray diffraction is one of the most important techniques, used for understanding the crystallographic characteristics of the material together with any residual stress, volume change, and other related information. The electrode materials used in rechargeable batteries undergo lithium/sodium ion insertion/extraction process during cycling, causing changes in the electrode materials. The changes may include even permanent structural changes in some cases together with changes like localized strain, volume expansion/contraction, and even complete structural collapse. These cause cyclic instability, and even causing fire accidents in some cases. The in-situ XRD can be integrated to monitor such changes during charging/discharging cycling and thus, may provide a wealth of information to design and develop a robust electrode material for enhanced stability during charging/discharging cycling. The presented review will discuss a few case studies (both Li and Na ion rechargeable batteries) to track such changes in respective cathode materials and thus provide the use of in-situ XRD measurements in electrochemical storage devices.

We review the development of a non-destructive technique based on Raman spectroscopy and microscopy for the in-situ characterization of electrode materials, mainly rechargeable Li-ion and sodium-ion batteries. It is possible to characterize the electrode materials using the extremely sensitive Raman shift and line width measurements to factors such as crystal structure, atomic positions, stress, chemical species, isotopes, oxidation states, bond strength, etc. The improved battery and cell performance can be attributed to minimizing the affecting factors. Overall, in-situ Raman spectroscopy has become an effective method for researching rechargeable batteries, offering insightful knowledge of the structural and chemical alterations brought about by battery operation. Using this approach, researchers may observe electrode materials under operando settings in real-time and analyze the complex processes involved in charge and discharge cycles. With an emphasis on the electrode materials for lithium-ion (Li-ion) and sodium-ion (Na-ion) batteries, this study provides an overview of in-situ Raman techniques for rechargeable batteries. We discuss how in-situ Raman spectroscopy can examine electrode materials’ structural alterations, phase transitions, and electrochemical processes. It is possible to learn a lot about the behavior of materials during electrochemical processes by following up on the development of vibrational modes and spotting distinctive peaks. We also present various experimental results from the literature on the in-situ characterization of electrode materials using Raman spectroscopy and microscopy, including all the design aspects.

Mo₂C emebded in carbon and reduced graphene oxide has been explored as an anode material for lithium as well as sodium ion batteries. This suitably designed anode demonstrates capacity around 650 mAh/g in case of lithium ion battery and ~450 mAh/g capacity at 50 mA/g current density in case of sodium ion battery. The added extra carbon and reduced graphene oxide provide desired electronic conductivity and cushionnig affect to minimize the volume variation due to intercalation and deintercalation. Mo₂C/C/rGO anode could retain 645 mAh/g capacity after 1500 cycles when used as anode material for lithium ion battery. On the other hand, its retention is around 96.4% of its intial capacity after 750 cycles as sodium ion battery anode material. The excellent retention of capacity in both cases arises due to this specially designed electrode. The results shed light on potential of this material as futuristic anode material for lithium as well as sodium ion battery.

Liquid electrolytes with high salt concentrations offer better chemical and thermal stability for rechargeable battery applications. In this work, we study the effect of salt concentration on the diffusion and ion-ion correlations in ethylene carbonate lithium bis(trifluoromethane sulfonyl)imide (EC-LiTFSI) electrolytes using molecular dynamics simulations. Our simulations show that the ionic diffusivities and Nernst-Einstein conductivity decrease with the concentration of the LiTFSI salt. We also investigated the influence of salt concentration on the structural properties by calculating the radial distribution functions and coordination numbers for different pairs, such as ion-ion and ion-EC. As the salt concentration increases, we observe a systematic decrease in the peak of radial distribution functions and an increase in the corresponding coordination numbers for the Li-TFSI pairs. Consistent with the structural features, the ion-pair time correlation functions are observed to decay slowly and monotonically with the addition of salt. We further investigated the interplay of different parameters that affect diffusivity and provide mechanistic insights into ion transport in EC-LiTFSI electrolytes.

To address the intermittency and energy deficit associated with solar energy, photo-rechargeable batteries (PRBs) can offer energy solutions for remote and off-grid locations. A PRB can simultaneously perform energy harvesting and energy storage in the form of electrochemical energy in a single device. Such devices minimize ohmic losses, the number of electrodes, materials, packaging requirements, and as a result, total device cost. In recent years 2D metal halide perovskites, MoS₂ and V₂O₅ have been used as active material for Li-PRBs, but these devices suffer either from low stability, complex synthesis of active material, and complex fabrication routes. Iron oxide (α-Fe₂O₃) anodes offer high theoretical capacity (1006 mAh g⁻¹) for conventional Li-ion battery (LIB) applications, as well as are highly stable in liquid electrolyte environments. Moreover, its suitable bandgap (~2.1 eV) in the visible region makes it a potential active material for high-performance PRB applications. Here, we provide initial results on the fabrication of nanoporous crystalline α phase Fe₂O₃ (hematite) electrodes based photocathodes for photo-enhanced LIBs using a conversion mechanism. The demonstrated Li-PRB showed a specific capacity of 689.3 mAh g⁻¹ under dark conditions at a current density of 1000 mA g⁻¹ after 100 cycles in a voltage range of 3.0–0.01 V. The Li-PRB showed an enhancement of up to 92.96% in the specific capacities when exposed to white light LED (broad spectra in the visible region, 12 mW cm⁻²) at a current density of 2000 mA g⁻¹. The photocharging effect is also confirmed by performing various in-situ measurements such as cyclic voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and Galvanostatic charging discharging (GCD) under dark and illuminated conditions.

The growing demand for renewable energy and energy storage solutions is driven by two significant challenges faced by fossil fuel-based energy generation methods: energy security and greenhouse gas emissions. Electrochemical energy storage technology, particularly lithium-ion batteries (LIBs), offers high energy density and numerous charge/discharge cycles. However, the safety of LIBS has been called into question due to the risk of thermal runaway and fire accidents caused by factors such as lithium dendrite/plating (dead lithium). This research paper investigates the formation of dead lithium in a commercially available 18650 NCM (Nickel Cobalt Manganese) lithium-ion battery under low temperature (−5 °C) with 1C charging rate and 2C discharging rate. The study employs electrochemical impedance spectroscopy to characterize the process and validated through kramers kronig transform (KKT) as well as evaluated with distribution of relaxation time (DRT). The results reveal that during lithium formation at the anode surface, the resistance of the solid electrolyte interface (SEI) layer remains almost constant, but the series resistance significantly increases, indicating the conversion of active lithium-ion into dead lithium on the electrode's surface, while the charge transfer resistance (R_ct) increases slightly. This finding could contribute to a better understanding of dead lithium formation and improve battery safety.

Aluminum-Air Battery (AAB) is getting attention because of its simple structure, suitable redox potential, and most abundant aluminum metal in the earth's crust, with the expectations to meet or mitigate the energy demand. We designed a cost-effective AAB under ambient conditions, consisting of pure Al as the anode, 4M KOH as an electrolyte, and carbon cloth (CC) as the current collector, and its electrochemical performance is evaluated. The electrochemical cell is modified by adding catalyst V₂O₅ on CC for improving the electrochemical performance. Further, the 4M KOH electrolyte is modified using 30 mM NH₄VO₃ additive. These two modifications are also integrated into one, i.e., pure Al-4M KOH + 30 mM NH₄VO₃-V₂O₅/CC cell. The corrosion and polarization studies are carried out to understand the impact of additive NH₄VO₃ mixed in the alkaline electrolyte, on the aluminum anode. The best obtained specific capacity among all the configurations is about 970.49 mAh g⁻¹ at 5 mA discharge current for ~4 h, corresponding to the pure Al-4MKOH + 30 mM NH₄VO₃-V₂O₅ AAB configuration. The discharge plateau is observed at 1.3 V for more than 8000 s.

Lithium-ion batteries (LIBs) are extensively explored due to their higher gravimetric/volumetric capacity and energy density. However, constraints such as higher lithium cost limited lithium resources, and associated toxic, explosive, and highly reactive characteristics with water compel to hunt for alternative rechargeable batteries as efficient electrical energy storage systems. Iron, the second most abundant material with non-toxic characteristics and relatively lower cost, makes it an attractive system for rechargeable iron-ion batteries (RIIBs) with the possibility of an alternative to the LIBs for next-generation energy storage devices without any adverse effects or environmental impacts. However, the large size and slow diffusion are the materials’ issues that must be addressed. Here, RIIBs are fabricated under ambient conditions using mild steel as an anode for an iron source and graphitic carbon nitride as a cathode material. g-C₃N₄ material is synthesized via the thermal polymerization of melamine precursor and an aqueous electrolyte, including ferrous sulfate heptahydrate-based salts. Cyclic voltammetry was investigated to check the redox reaction at various scan rates. The galvanostatic charge–discharge (GCD) characteristics are measured at different current densities, showing a capacity of ~135 mAh g⁻¹ at 1 A g⁻¹, and a lower density of 0.5 A/g shows a higher gravimetric capacity of ~180 mAh/g. Its exhibits 50% capacity retention in 50 cycles at 1 A/g. The performance degradation was investigated using impedance analysis between the cycling and the post-mortem of the anode and cathode using the SEM-EDAX analysis after 150 GCD cycles.

Lithium iron orthosilicate (Li₂FeSiO₄) with an olivine structure is one of the promising cathode materials for energy storage devices due to its properties like high theoretical capacity, eco-friendly, low price, and extreme affluence. Out of all available energy storage devices, supercapacitors have high power density, fast charging-discharging rate, and high stability. Supercapacitors are of two types symmetric and asymmetric on the basis of fabrication. Here we have tested the performance of different asymmetric supercapacitors consisting of Li₂FeSiO₄ as cathode and FeOOH, MoSe₂, Activated carbon, and graphite as different anode materials. The structural analysis of the prepared sample was done by XRD. Exploration of the electrochemical performances of all designed asymmetric supercapacitors was tested using CV, EIS, and GCD techniques. Li₂FeSiO₄ and MoSe₂-based asymmetric supercapacitor exhibited excellent electrochemical properties delivering specific capacitance of 512 F/g at a current density of 3 A/g, low charge transfer resistance of 0.41 Ω with high power density of 4260 W/Kg corresponding to the energy density of 71 Wh/Kg.

Supercapacitors (SCs) have drawn a considerable concentration because of their magnificent power density, extended cycle life, rapid charge/discharge rate, and with nearly negligible short–circuit problems compared to conventional batteries and capacitors. Carbon–based nanomaterials are widely used for supercapacitor electrodes because of their enormous surface area and electrical conductivity. Here we propose a symmetric supercapacitor made of exfoliated graphite (EXG) as a host with the composites of ZnO nanorods (NRs) in different ratios to show its capability to store the enhanced energy in a simple system. Highly porous exfoliated graphite was synthesized using the thermal exfoliation method of a chemically treated natural graphite flakes (NGFs) and compressed to paper with ZnO NRs synthesized by the hydrothermal route. SCs contain compressed electrodes of the EXG-10% ZnO NRs composite. The electrochemical behavior of SCs was investigated using Cyclic Voltammetry (CV) in 0 to 0.6 V potential window at different scan rates. The measured areal–specific capacitance is ~15 mF/cm² at 10 mV/s scan rate for 10% ZnO NRs and EXG composite electrode. The capacity retention is more than 95% after the 1000 cycles at a higher scan rate, suggesting highly stable electrodes. Electrochemical impedance analysis is also carried out before and after the complete cycling to analyze the electrode interface resistance. The pseudocapacitive materials have high specific capacitance and low cycle life while carbon materials have long cycle life and less specific capacitance. This work employs less weight percentage of ZnO as a potential booster to increase the capacitance of EXG-based symmetric SC. EXG-10% ZnO NRs composite is a highly stable electrode material for symmetric SC with optimal capacity.

Energy storage has evolved as a crucial domain demanding urgent attention. Tremendous efforts are on the way for the design and development of charge storage materials with high capacity and rate capability. Supercapacitors are widely regarded as potential energy storage devices due to their high power density, non-toxic nature, safe operation, and long life cycle. As a material with unique structural stability, electronic properties, compositional flexibility and oxygen vacancies, strontium titanate qualifies for supercapacitor applications. The present work reports the fabrication of a ternary composite of SrTiO₃ (STO) incorporating conducting polymer polyaniline (PANI) and multi-walled carbon nanotubes (MWCNTs). XRD, FTIR, and XPS analysis confirmed successful composite formation, while electrochemical impedance spectroscopy revealed heterojunction formation with efficient charge transfer. Cyclic voltammetry (CV) and charge–discharge tests showed the potential of STO/CNT/PANI composite as a promising material for supercapacitor applications. CV plots in a three electrode assembly revealed the pseudo-capacitive nature of the composite, and the specific capacitance was found to be 854 F/g with 1 A/g current density. The charge storage capacity of the composite can be attributed to the synergistic interaction between PANI and carbon materials. Furthermore, the system exhibited reasonable cyclic stability of 71% at 5 A/g current density after 1000 scans. The overall performance of the composite may be traced to the synergistic interaction between PANI and CNT.

Bare ZnO and 6wt% Manganese doped ZnO nanoparticles has been synthesized through the aqueous co-precipitation technique. The structural and phase purity have been verified through X-ray diffraction (XRD). The mean grain size determined by Scherrer’s formula is 26.29 nm and 20.52 nm for ZnO and Mn doped ZnO, respectively using FWHM corresponding to the highest peak intensity of (101). Scanning electron microscopy shows nano-flakes, and nano particles as the heterogeneous surface morphology. The nanoparticle’s elemental composition is matching with stoichiometric ratio. Thermal gravimetric analysis (TGA) has confirmed the thermal stability in the range of room temperature to 800 °C. Brunauer-Emmitt-Teller (BET) analysis has validated the ~60% increase in the specific surface area is 24.35 m²/g as compared to 15.25 m²/g for bare ZnO. At 5 mV/s scan rate, the calculated specific capacitance values for ZO and 6MZO is 80.06 and 483.20 (F/g) using 2M KOH electrolyte, respectively.

Due to their environmental friendliness, high power density, and quick charge–discharge properties, lead-free ceramic capacitors are having high demand in various electronic systems, pulse power supply systems, automobiles, distributed power systems etc. Nevertheless, the concurrent higher recoverable energy storage density (W_rec) and efficiency (η) are still difficult to obtain and must be researched. The energy storage properties can be increased by lowering the residual polarisation and raising the breakdown strength to produce a dielectric capacitor with a high W_rec and η. Due to its antiferroelectric and ferroelectric properties, lead-free ceramics based on NaNbO₃ have much potential for energy storage and piezoelectric devices. Pure NaNbO₃, however, typically exhibits lossy hysteresis loops due to the metastable antiferroelectric phase at ambient temperature. In this work, NaNbO₃(NN) was introduced in Ba_0.96Sr_0.04Zr_0.1Ti_0.9O₃(BSZT) to modulate the phase structure, dielectric and energy storage properties. Structural study confirms the formation of a monoclinic phase in NN, while for the (1-x) BSZT-xNN, the formation of a tetragonal phase has been observed. The microstructural study of the ceramic composite reveals the formation of dense microstructure with a decrease in grain size with increased NN content. The dielectric study reveals the diffuse phase transition (DPT) behaviour of the material around the curie point. With the increase in NN content dielectric constant was found to decrease with a dielectric loss (tan δ) value ≤ 0.20 for all compositions. From the ferroelectric study, an optimal recoverable energy density (W_rec) = 0.16 J/cm³, efficiency (η) = 84.2% has been achieved at 40 kV/cm for x = 0.06 composition.

Hydrogen, the lightest element with highest gravimetric energy density, has attracted global interest as clean chemical fuel with water as the only byproduct. Hydrogen is an excellent choice to replace conventional fossil fuels due to its high calorific value and low ignition energy. Along with these, the growing consumption of energy globally has encouraged researchers to work on hydrogen technology for a carbon–neutral sustainable economy. This can be realized by cost-efficient production of hydrogen. Once hydrogen is produced, the most challenging task is to figure out the safe and convenient storage of it because of its low volumetric energy density. And hydrogen storage is essential for its use in mobility and stationary applications. Various hydrogen storage methods have been developed e.g., liquid hydrogen at cryogenic temperature, compressed gaseous hydrogen in high pressure tanks, and in solid materials in gaseous form through adsorption or absorption process. So, to realize the hydrogen economy in true sense, it is important to explore the more convenient and efficient hydrogen storage methods, which is one of the major bottlenecks of hydrogen economy. Thus, considering the importance of the field, this review article is designed to highlight some of the recent progress and challenges associated with hydrogen storage methods and their use for mobility applications.

Hydrogen is expected to play a leading role in attaining carbon neutrality. Therefore, the production of hydrogen using renewable energy is foreseen. To address this aspect, concentrated solar thermal-based thermochemical hydrogen generation systems are discussed as potential candidates for industry-level green hydrogen production. The paper presents (a) a literature review highlighting the latest developments and some limitations of these technologies and (b) the development of a system for concentrated irradiance-based ammonia cracking.

All the sustainable development objectives proposed by the United Nations call for a more prudent and responsible use of the world’s natural resources, with the least possible disruption to the environment's delicate balance. One of these main objectives is to make sure that everyone has simple access to modern, sustainable, economical energy. Since they are sustainable, clean, and ecologically benign, researchers are largely focusing on renewable energy sources in this direction. However, there are many barriers that limit their widespread usage in commercial applications, including their low reliability, irregular nature, remote availability, etc. A possible answer to issues including increased energy consumption, dependable and constant electric power, and improved grid stability may be to combine these renewable energy sources with efficient and economical energy storage technology. Modern energy storage technologies like EDLC and lithium-ion batteries have enormous potential for a variety of energy storage applications. The most adaptable fundamental materials for the storage and conversion of contemporary energy may be those based on carbon. The commercially manufactured activated carbon is expensive and unsustainable since it requires the expensive processing of non-renewable and high-priced precursors, i.e., wood, petroleum, and coal. The transformation of waste plastics into value-added, affordable carbon nanomaterials has drawn a lot of scientific interest because of the exponentially rising volume of plastic trash and the need for effective solid waste management. Therefore, plastic waste remediation for the generation of electrode materials of modern electrochemical double-layer supercapacitors (EDLCs) and lithium-ion batteries (LIBs) can be treated as a two-way sustainable approach. It addresses the problems of solid plastic waste management and affordable energy storage for renewable energies at the same time. This book chapter examines the necessity and the efforts undertaken to develop supercapacitors and Li-ion batteries as sustainable modern energy storage devices using carbon materials synthesized from remediation of the waste plastic.

The effect of La-Ni-based alloys La₂₃Nd_8.5Ti_1.1Ni_33.9Co_32.9Al_0.65, NiMn_9.3Al_4.0Co_14.1Fe_3.6, and NiMnAl on MgH₂ and their Hydrogenation properties were investigated. All these additives considerably enhanced MgH₂’s dehydrogenation capabilities, but NiMnAl exhibits the best alloy effect followed by La₂₃Nd_8.5Ti_1.1Ni_33.9Co_32.9Al_0.65 and NiMn_9.3Al_4.0Co_14.1Fe_3.6 sequentially. Kissinger’s equation was used to compute the activation energy of dehydrogenation the activation energy is decreased to various degrees by the use of Ni-based additives. The best outcome was for the MgH₂-25 wt% NiMnAl. Due to the catalytic impacts on hydrogenation/dehydrogenation rates, thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies revealed the creation of many active species.

To address the energy scarcity and prevailing environmental issues, renewable energy resource-based technological advances are quite vital. Solar energy harnessing for photoelectrochemical (PEC) water splitting seems to be a viable strategy for the same. The development of an efficient photoelectrode is the key task in the photoelectrochemical process. In this study, we have fabricated Au nanoparticles (NPs) decorated onto a g-C₃N₄/Bi₂S₃ heterojunction by drop-casting method. The g-C₃N₄/Bi₂S₃ heterojunction was fabricated using annealing followed by a doctor blade method, while Bi₂S₃ was loaded using successive ionic layer adsorption and reaction (SILAR). Although g-C₃N₄ is a polymeric semiconductor with unique properties, it suffers from high electro-hole recombination and low conductivity. Bi₂S₃ and Au NPs have been introduced to overcome these issues as they offer advantages such as high optical absorption coefficient, favorable band alignment, narrow bandgap, and improved charge carrier density. The Au NPs play a vital role in preventing charge recombination due to the surface plasmon resonance effect, resulting in good photochemical energy conversion efficiency, photostability, and interfacial charge transfer kinetics. The g-C₃N₄/Bi₂S₃/Au heterojunction exhibited a photocurrent density of 1.4 mA/cm² at 1.23 V versus RHE and a solar-to-hydrogen efficiency (STH) of 0.72% at 0.68 V versus RHE in neutral medium. The photostability of the fabricated electrodes was ensured by scanning up to 1000 s in the neutral electrolyte (0.1 M Na₂SO₄). Electrode/electrolyte charge transfer kinetics was analyzed by impedance analysis, and it was found that in comparison to the individual counterparts, the g-C₃N₄/Bi₂S₃/Au photoelectrode displayed a smaller semicircle in the high-frequency region indicating better charge transfer at electrode/electrolyte surface.

In this work, we present a binder-free, direct growth of SnS₂ nanoflakes on carbon cloth (CC), adopting a cost-effective, one-step hydrothermal technique as an efficient electrocatalyst for hydrogen evolution reaction (HER). The XRD spectrum confirms the phase pure SnS₂ nanoflakes with crystallite size 38 \(\pm\) 2 nm. The presence of A_1g peak in the Raman spectrum at ~313 cm⁻¹, corresponding to out-of-plane vibration of S-Sn-S atoms, further confirms SnS₂ at CC. The detailed electrochemical analysis shows the HER overpotential value of SnS₂ as ~411 mV at a current density of 10 mA/cm². The Tafel slope for SnS₂@CC is 151 mV dec⁻¹; a lower Tafel slope value suggests the fast reaction kinetics of the electrocatalyst. The chronopotentiometry stability test performed for 6 h suggests that the HER response of the electrocatalyst is quite stable with time. The present findings indicate that the catalytically inactive binder-free growth and nanostructured morphology are the prime factors responsible for the enhanced electrocatalytic activity of SnS₂@CC.

In this work, we demonstrate a single step hydrothermally grown nanorod shaped pristine and Vanadium (V) doped NiS on highly porous nickel foam substrate, i.e., NiS@NF and V-NiS@NF. A detailed electrochemical analysis, in terms of hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and Tafel slope, suggests that V doping enhances the electrocatalytic activity of NiS@NF for water splitting. V-NiS@NF delivered 172 mV HER and 310 mV OER overpotentials at current densities of 10 mA/cm² and 50 mA/cm², respectively. The Tafel slope values for HER and OER of V-NiS@NF are 45 mV/dec and 25 mV/dec, respectively. The better electrocatalytic performance of V-NiS@NF as compared to the NiS@NF was attributed to the matching of the atomic radius and deformation of the electronic structure of the pristine NiS@NF resulting in higher active sites. Due to the bifunctional nature with moderate HER/OER overpotentials and ease of synthesis, the present electrocatalyst V-NiS@NF can be used to develop an efficient electrolyzer for green hydrogen generation through water splitting.

The Brown gas (HHO), i.e., hydrogen as well as oxygen, is considered as one of the assuring fuels for the future. It can be generated by renewable process such as (i) photoelectrochemical water splitting, (ii) thermochemical water splitting, (iii) electrochemical water splitting, etc., with zero carbon emission. We designed an HHO generator using different electrode materials and investigated the impact of electrolyte molarity, and plate counts, which determine the efficiency and gas generation capacity of the device. We observed that the combination of stainless steel with KOH results in the maximum yield in a hydrolytic reaction among other electrode materials. On the other hand, aluminium was failing to provide a minimum power to initiate the reaction at a feasible rate, aside of that stainless steel provided power of 90 W attributed to the higher electrolysis rate. They will endure for a long period so that we can escalate the production at the industrial scale. While working with 3 biased and 2 neutral electrodes combination, the device was able to continuously generate HHO at a flow rate of 175 ml/min for 30 min with power of 100.8 W. And with 3 biased electrodes and 4 neutral electrodes, highest production of HHO gas was 180 ml/min at 118 W power. Thus, the present device with stainless steel as electrode and KOH as electrolyte can be a better option for a cost-efficient large-scale production of the HHO gas.

Global energy challenges compel us to explore alternative green energy sources to meet the rapidly depleting conventional energy sources. Hydroelectric cell is a noble invention in generating green electricity by nanopores defect modulated water dissociation processes without external power. In this work, ZnO nanostructured samples are synthesized using the hydrothermal and chemical auto-combustion methods. Further, their morphology is controlled by precursor concentration. The phase purity of synthesized ZnO nanostructures is confirmed using X-ray diffractogram (XRD). The SEM image reveals the diameter ZnO increase from nanometer to micrometre with the increase in Zn precursor concentration and auto combustion synthesized ZnO has the morphology of nanoparticle due to extra thermal energy obtained during the synthesis. The band gap of the synthesized ZnO is \(3.195, 3.187, 3.186\) and \(3.22\,\text{eV}\) for ZnO NRs, ZnO MRs, ZnO Bulk and ZnO NPs respectively. The ZnO NRs and ZnO NPs have higher average specific surface areas of \(6.75\) and \(4.59\,\text{m}^{2}\text{/g}\) and are responsible for the higher off-load power. ZnO-based HEC is fabricated using nanorods, microrods, bulk, and nanoparticles ZnO powder materials. ZnO nanoparticle-based HEC device (\(Area=2.2\times 2.2\,\text{cm}^{2})\) showed the maximum \(5.82\,\text{mA}\) current with \(0.60\,\text{V}\) open circuit voltage and \(3.50\,\text{mW}\) maximum off-load power using only \(1\,\text{ml}\) of water.

Due to the unique and intriguing buckled topology, modeling and understanding thermal transport is challenging in germanene 2D materials. We examine the suitability of Tersoff and Stillinger–Weber interaction potentials to model the germanene monolayer and investigate the phonon thermal conductivity. We find that the widely used Tersoff interaction potential cannot accurately reproduce the experimental structure of the germanene monolayer at higher temperatures. However, we observed that Stillinger–Weber potential with optimized parameters satisfactorily reproduces the structure and buckling of germanene monolayer over a wide range of temperatures and is quite suitable for studying thermal conductivity of germanene. We used molecular dynamics simulations to generate 30 independent equilibrium trajectories at a given temperature to understand the thermal conductivity in the germanene monolayer. Our simulations predict that the thermal conductivity of the germanene monolayer is 3.6 \(\pm\) 0.4 W/(m.K) at room temperature, which further decreases rapidly with temperature. The thermal conductivity of germanene is found to be much lower than that of graphene and silicene at any temperature.

Pristine tin sulfide (SnS) nanoparticles were produced by using the conventional hydrothermal procedure. Tin chloride dihydrate (SnCl₂·2H₂O) and thioacetamide (C₂H₅NS) were utilized as the primary carriers of Sn²⁺ and S²⁻ ions respectively. Polyvinylpyrrolidone (PVP) was added as a regulating compound to maintain particles’ regular morphology. The X-ray diffraction pattern has confirmed the orthorhombic unit cell structure with lattice components (a = 11.23 Å, b = 3.98 Å, and c = 4.25 Å) which are in great agreement with JCPDS card no. 00-067-0519. Using Scherrer’s equation, the typical crystallite size ranges between 16 and 40 nm. The surface morphology of synthesized SnS nanoparticles is sheet type and marble chips type as obtained from Scanning Electron Microscopy (SEM). Tin (Sn) and sulfur (S) have an atomic proportion that is about 50%. The ultraviolet–visible near-infrared spectroscopy (UV–Vis) is performed between 200 and 800 nm and confirms the direct band gap value is 1.54 eV by the Kubelka–Munk function and tauc relation plot. Partial thermoelectric properties of synthesized nanoparticles were obtained using a ‘Hall effect setup’ at room temperature (306 K). It reveals that semiconducting nature, carrier concentration (n), hall coefficient (R_H), electrical conductivity, and hall mobility are P-type semiconductors, n = 2.64 * 10¹⁷ cm⁻³, R_H = 23.663 cm³/C, \(\sigma\) = 0.197 S/cm, \(\mu\)_H = 4.66 cm² V⁻¹ s⁻¹ respectively.

The family of ternary chalcogenides (CuSbS/Se₂ and CuBiS/Se₂) provides an ample option of potential candidates for the new generation photovoltaic devices. However, Copper antimony sulphide CuSbS₂ (CAS), is an efficient absorber material during present scenario for thin film solar cells due to its extraordinary optical and structural properties. In this paper, substrate heterojunction thin film solar cell (HJTFSC) simulated having defects of V_Cu in CAS with CdS buffer, ZnO window and Mo back contact using the SCAPS-1D software. The main focus of the reported work is to observe the impact of copper vacancies (V_Cu at 0.08 eV above VBM) on the performance of cell. The cell performance can also be observed by changing the absorber layer properties, i.e., thickness and carrier density. The cell structure ZnO:Al/i-ZnO/n-CdS/p-CuSbS₂/Mo was set in software and calculated the optoelectronic parameters, i.e., short circuit current density (J_sc), open circuit voltage (V_oc), fill factor (FF) and efficiency (η). The physical parameters of solar cell were set at room temperature 300 K under illumination intensity 100 mW/cm² with AM1.5 spectrum. The optimized thickness and carrier density of the absorber layer were 2.5 μm and 5 × 10¹⁶ cm⁻³, respectively that reveals the ~10% energy conversion efficiency.