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Supercapacitors (SCs) are gaining attention for Internet of Things (IoT) devices because of their impressive characteristics, including their high power and energy density, extended lifespan, significant cycling stability, and quick charge–discharge cycles. Hence, it is essential to make precise predictions about the capacitance and lifespan of supercapacitors to choose the appropriate materials and develop plans for replacement. Carbon-based supercapacitor electrodes are crucial for the advancement of contemporary technology, serving as a key component among numerous types of electrode materials. Moreover, accurately forecasting the lifespan of energy storage devices may greatly improve the efficient handling of system malfunctions. Researchers worldwide have increasingly shown interest in using machine learning (ML) approaches for predicting the performance of energy storage materials. The interest in machine learning is driven by its noteworthy benefits, such as improved accuracy in predictions, time efficiency, and cost-effectiveness. This paper reviews different charge storage processes, categorizes SCs, and investigates frequently employed carbon electrode components. The performance of supercapacitors, which is crucial for Internet of Things (IoT) applications, is affected by a number of their characteristics, including their power density, charge storage capacity, and cycle longevity. Additionally, we provide an in-depth review of several recently developed ML-driven models used for predicting energy substance properties and optimizing supercapacitor effectiveness. The purpose of these proposed ML algorithms is to validate their anticipated accuracies, aid in the selection of models, and highlight future research topics in the field of scientific computing. Overall, this research highlights the possibility of using ML techniques to make significant advancements in the field of energy-storing device development. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides exhibit various stacking polytypes and distinct electronic structures. In this study, first-principles calculations show that chalcogen enrichment induces the phase conversion from 2H to 1T′. Models for Se intercalation and substitution (MoSex and WSex with x > 2) were constructed for the 2H and three stacking polytypes of the 1T′ phase (1T′, 2M, and Td). Se intercalates and substitutes more favorably into the 1T′ polytypes than into the 2H phase. Intercalation in the 1T′ polytypes occurs by forming Se dimers, which is distinct from the Se monomer in the 2H phase. The relative stability predicts that as x increases, the 2H phase undergoes phase conversion preferentially into the 2M phase. On the experimental side, we synthesized Se-rich MoSe2 and WSe2 nanosheets using a colloidal reaction, and confirmed the stacking sequence of the 2M phase using atomic-resolution scanning transmission electron microscopy. The Se-rich 2M phase nanosheets exhibited enhanced electrocatalytic performance in the hydrogen evolution reaction (HER). Gibbs free energy calculations support that excess Se enhances the HER. [ABSTRACT FROM AUTHOR]

The development of a single junction photoelectrode material having specific properties is essential and challenging for the efficient application in solar water splitting for oxygen production and a high value-added product, hydrogen. Moreover, the present material solutions based on binary metal oxides offer limited catalytic activity and hydrogen production efficiency. Therefore, it is paramount to develop and exploit a unique range of materials derived from ternary metal oxides with specifically engineered properties to advance in photoelectrochemical (PEC) water splitting. Among the ternary oxides, copper vanadates offer promising characteristics, such as a narrow bandgap and catalytic surface properties along with favorable band edges for facile oxygen evolution reaction (OER), which is considered the bottleneck step in performing overall water dissociation. Furthermore, the copper vanadates allow the tuning of the stoichiometry through which a wide range of polymorphs and materials could be obtained. This review provides a complete outlook on the range of copper vanadates and the established synthesis approach, morphology, crystal structure, band edge properties, and PEC characterizations. Mainly, the underlying charge dynamic properties, carrier path length, effect of doping, and influence of surface catalysts are discussed. The review concludes that the advancement toward obtaining low-bandgap materials is a main challenge to overcome the limitations for efficient water dissociation to OER and copper vanadates, which offer a promising solution with their unique properties and advantages. Importantly, intense and strategically focused research is vital to overcome the scientific challenges involved in copper vanadates and to explore and exploit new polymorphs to set new efficiency benchmarks and PEC water splitting solutions. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting is one of the most sustainable approaches for converting solar energy into hydrogen fuel. Affordable and robust photoelectrodes are crucial for the commercialization of PEC technologies. Recently, transition metal-based co-catalysts, especially Ni- and Fe-based catalysts, have attracted much interest owing to their exceptional OER characteristics. Given this, we here proposed the decoration of a Fe-Ni-based cocatalyst on the surface of the TiO2 photoanode for PEC water splitting. The TiO2 photoanode was hydrothermally synthesized and then decorated by Fe-Ni hydroxide catalyst using photo-assisted electrodeposition. The optimized TiO2/FeNiOOH photoanode exhibited the maximum photocurrent density value of 1.36 mA cm−2, which is almost twice the value obtained for bare TiO2, at 1.23 V vs RHE under the AM 1.5 G illumination. Due to the enhanced light absorption in the UV region, the optimized photoanode exhibited remarkable IPCE and photoconversion efficiency of 87.8% and 0.93%, respectively. Furthermore, excellent faradaic efficiencies of ∼90% for H2 and ∼70% for O2 generations were obtained. Predominantly, the enhancement in the photocurrent potentials was explained in detail. Our study shows the roles and benefits of using bimetallic catalysts with TiO2 photoanodes for sustainable water-splitting applications. [ABSTRACT FROM AUTHOR]

Semiconductor ionic electrolytes, especially heterostructure composites, have a significant role in enhancing oxide ion conductivity and peak power density (PPD) because of their interfacial contact. In this work, the fluorite structure CeO2 and spinel-based CoAl2O4 samples, as a heterostructure composite electrolyte, are successfully fabricated. The p-type CoAl2O4 and n-type CeO2 heterostructure (CeO2-CoAl2O4) used as an electrolyte exhibits a cell performance of 758 mW/cm2 under fuel cell H2/air conditions at 550 °C, which is quite higher than the pure CoAl2O4 and CeO2 fuel cell devices. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) verified the heterostructure formation including the morphological analysis of the prepared heterostructure composite. The heterostructure-based CeO2-CoAl2O4 composite achieved a higher ionic conductivity of 0.13 S/cm at 550 °C temperature, which means that the constructed device successfully works as an electrolyte by suppressing electronic conductivity. Meanwhile, the obtained results demonstrate the semiconductor ionic heterostructure effect by adjusting the appropriate composition to build heterostructure of the n-type (CeO2) and p-type (CoAl2O4) components and built-in electric field. So, this work exhibits that the constructed device can be effective for energy conversion and storage devices. [ABSTRACT FROM AUTHOR]

High-performing electrolytes at low operating temperatures have become an inevitable trend in the development of low-temperature solid oxide fuel cells (LT-SOFCs). Such electrolytes have drawn significant attention due to their appeal for high performance. Herein, we propose a new material by doping Y3+ into Gd2O3 for LT-SOFC electrolyte use. The prepared material was characterized in terms of crystal structure, surface, and interface properties, followed by its application in LT-SOFCs. YDG delivered promising SOFC performance with a power density of 1046 mW cm−2 at 550 °C along with high ionic conductivity of 0.19 S cm−1. Moreover, impedance spectra revealed that YDG exhibited the least ohmic resistance of 0.06–0.09 Ω cm2 at 550–460 °C. Furthermore, stable operation for 60 h demonstrated the chemical stability of the material in reduced temperature environments. Density function theory was also applied to analyze the electronic band structure and density of states of the synthesized sample. Our findings thus certify that YDG as a high-performing electrolyte at low operating temperatures. [ABSTRACT FROM AUTHOR]

Hybrid flexible supercapacitors (HFS) offer high power density and stability making them an ideal choice for the energy storage system in wearable devices. In this work, the synthesis of lamellar flower-like alpha manganese vanadate (α-Mn 2 V 2 O 7) on nickel foam was proposed for efficient and highly stable HFS applications for the first time. The voltammetric characterization indicated that the capacitance contribution of α-Mn 2 V 2 O 7 is derived from the diffusion-controlled (battery-type, 89.93%) and capacitive controlled (10.07%) mechanisms in aqueous electrolyte (0.5 M KOH). The optimized α-Mn 2 V 2 O 7 electrode exhibited an impressive specific capacity of 125.6 mAhg−1 (760.3 Fg-1). In the HFS device configuration, the utilization of α-Mn 2 V 2 O 7 resulted in a remarkable specific capacitance of 35.7 F g−1 with energy, and a power density of 28.4 Whkg−1 and 8.5 kWkg−1, respectively. Furthermore, the α-Mn 2 V 2 O 7 fabricated device is found to operate in a wide potential window exhibiting remarkable and stable electrochemical performance in the gel electrolyte even under mechanical stress conditions. Importantly, the α-Mn 2 V 2 O 7 HFS showed an impressive and stable performance over 5000 cycles. The superior specific capacitance performances obtained in the present study are noted to be the best results reported for vanadium-based ternary oxides so far. [ABSTRACT FROM AUTHOR]

The attraction of electronic textiles for next‐generation wearable electronic devices has raised the demands of washable and stretchable energy storage. However, negative effects of washing on the textile‐based devices are majorly known. In this work, besides the innovation of a conventional stretchable composite based on carbon nanotubes (CNT) and polydimethylsiloxane (PDMS) for textile‐based supercapacitors, findings regarding negative and positive effects of washing are introduced. Since the CNT‐and‐PDMS‐based composite (CNT+PDMS) owns high stretchability but low electrochemical performance, two strategies using molybdenum trioxide (MoO3) nanoflakes are designed for upgrading the composite performance. Through stretching, washing, and electrochemical tests, the pros and cons of these strategies are revealed and discussed. Besides, a positive effect of chemical treatment of a liquid detergent (i.e., prewashing) is discovered, and it can improve the prewashed supercapacitor electrodes from 10 to 84 mF cm−2 at a scan rate of 10 mV s−1. Compared to supercapacitor cells assembled from unwashed electrodes, those of the sufficiently prewashed electrodes possess similar stretchability (≈60%) but threefold higher energy and power densities (3.9 μWh cm−2 and 0.89 mW cm−2, respectively). Overall, those findings are beneficial for the development of sustainable e‐textiles for wearable electronic applications. [ABSTRACT FROM AUTHOR]

The incorporation of the different functions of a biological nervous system into electronic devices is challenging in the realization of humanoid robotics, which can recognize and respond in a manner that is similar to humans. Emerging synaptic devices that can process electronic signals by neuromorphic functions that operate in a similar manner to that of biological nervous systems. In this study, an acid‐sensitive artificial nociceptor device, which simultaneously detects acid concentration and generates synaptic signals, is developed for electronic nose application. The transition metal oxide (WO3)‐based device electrochemically performs neuromorphic sulfuric acid (H2SO4) sensing. The current–voltage curves demonstrate loop opening, with the change in the molarity of the acid, indicating memory storage ability and tunability of the developed nociceptor device. [ABSTRACT FROM AUTHOR]

Combining WO 3 with suitable materials to form heterojunction is essential to overcome the limitations of WO 3 to enhance its photoelectrochemical (PEC) water splitting activity. Moreover, a clear understanding of photo-response and charge behavior of materials could lead to the rational design of efficient photoelectrodes. Given this, an efficient strategy is applied to fabricate WO 3 heterojunction with nitrogen-doped carbon dots (NCDs) and in-depth characterization to investigate the surface charge dynamics using nano imaging in a relation to the enhanced PEC water splitting activity. The optimized NCDs loading to the WO 3 NRs exhibited the enhanced photocurrent density of 1.54 mA cm−2 at 1.23V vs RHE under AM 1.5 G illumination, highest IPCE of ~82 % (at 308.32 nm). The Kelvin probe force microscopy and electrostatic force microscopy reveal that after loading NCDs to the WO 3 , a relatively smooth charge transport has been observed, which improves the PEC. Furthermore, this work demonstrates the effect of photogenerated charges caused by the NCDs that assist in enhancing the increased photocurrent, hydrogen production efficiency, and stability of the PEC water splitting system. Significantly, the nano imaging characterization utilized in this work could be extended to various photoanodes to study the surface charge dynamics. [Display omitted] • WO 3 NRs/NCDs heterojunction was proposed for water splitting applications. • NCD on WO 3 suppresses charge recombination and decreases charge transfer resistance. • Enhanced photocurrent, IPCE, and H 2 production was achieved upon NCD sensitization. • Nanoscale surface imaging was performed to understand insights of carrier dynamics. [ABSTRACT FROM AUTHOR]

Two-terminal memristive devices are considering as a potential candidate to mimic human brain functionality to enable artificial intelligence. Particularly, two-terminal nanoscale devices are regarded as a promising solution for implementing bio-synapses due to their small dimensions, extremely compact, and low power to operate neuromorphic functions. Here, we demonstrate that the nanoscale charge transport and resistive switching behavior of VOx thin film can be tuned by modulating the substrate morphology. Particularly, the device prepared with flat-Si shows totally distinguished behavior in comprising of reactive ion-etched-Si substrates. Interestingly, conductive atomic force microscopy current maps revealed the electric field inhomogeneity due to a change in substrate morphology. A reliable bipolar resistive switching behavior of the corresponding etched devices have been demonstrated. Due to an increase in the etching time of substrate, an increase in active area and decrease in work function was observed. Further, nanoscale synaptic functions were generated from the corresponding devices, showing a strong conduction path at preferential bright spots of the particular devices. Moreover, finite element simulations confirm the modulation in generation of localized current conduction in particular etched devices by applying tip voltages. These findings represent a new way to generate nanoscale artificial synaptic functions. [ABSTRACT FROM AUTHOR]

The phase control of transition metal dichalcogenides (TMDs) is an intriguing approach for tuning the electronic structure toward extensive applications. In this study, WSe 2 nanosheets synthesized via a colloidal reaction exhibit a phase conversion from semiconducting 2H to metallic 2M under Se-rich growth conditions (i.e., increasing the concentration of Se precursor or lowering the growth temperature). High-resolution scanning transmission electron microscopy images are used to identify the stacking sequence of the 2M phase, which is distinctive from that of the 1T' phase. First-principles calculations employing various Se-rich models (intercalation and substitution) indicated that Se enrichment induces conversion to the 2M phase. The 2M phase WSe 2 nanosheets with the Se excess exhibited enhanced electrocatalytic performance in the hydrogen evolution reaction (HER). In situ X-ray absorption fine structure studies suggested that the excess Se atoms in the 2M phase WSe 2 enhanced the HER catalytic activity, which is supported by the Gibbs free energy (ΔG H* ) of H adsorption and the Fermi abundance function. These results provide an appealing strategy for phase control of TMD catalysts., (© 2023 Wiley-VCH GmbH.)