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A layer-by-layer fabrication technique for a stacked on-chip supercapacitor operable in a wide range of temperatures (−20 °C to 70 °C) is demonstrated, and the prepared devices show competing performances at room and high temperatures.

Supercapacitors will serve as essential components of distributed energy storage networks and structural power devices in many emerging technologies. Current supercapacitors are engineered, however, using ‘sandwich’ architecture that undermines their physical integrity under stress and at high temperatures due to delamination. It also limits the successful integration of charge storage and load-bearing functions needed to increase the net stored charge. Bridging the requirement for high mechanical and thermal integrity of supercapacitors as structural energy storage elements is still challenging. Addressing these long-standing problems, we demonstrate here a process of developing structural monolithic supercapacitors (MSCs) where all the components are interdigitated by strong nanofibers synthesized from polyaramid fiber (Kevlar® 49). The monolithic design is realized using a one-step stratified assembly of a graphene–polyaramid nanofiber (PANF) and boron nitride–PANF nanocomposites acting as electrodes and separator, respectively. MSCs demonstrate an optimum combination of mechanical flexibility and robustness, distributing the stress at interfaces and preventing delamination. Also, combination of thermal stability with fast heat dissipation enables MSCs to operate at high temperature (∼100 °C). Hence, we envisage that MSCs could open prospects for their utilization as a structural energy and power system.

Green hydrogen production is a vital requirement of the upcoming hydrogen fuel-based locomotion and economy. Water electrolysis facilitated by electricity derived from renewable sources and direct solar-to-hydrogen conversion centred on photochemical and photoelectrochemical water splitting is a promising pathway for sustainable hydrogen production. All these methods require a highly active noble metal catalyst to make the water-splitting process more energy-efficient and in order to make it economical, metal-free hydrogen evolution catalysts such as graphene nanoplatelets (GNPs) are essential. Herein, we report the effect of a range of functionalizations on the catalytic properties of graphene nanoplatelets (GNPs) for the hydrogen evolution reaction (HER). We also account for the effect of functionalization on the strength of the electrical double layer formation on the surface of functionalized GNPs. It is observed that the catalytic activity and the electrical double layer strength are inversely related to each other. Our first-principles-based density functional theoretical (DFT) modelling unravels the origin of the observed electrocatalytic activity and its trend and the strength of the electrical double layers in terms of free energy changes during the ion absorption/desorption events on the electrode surface. Based on our observations, minimizing the electrical double layer strength is identified as an approach to improve the catalytic performance of the catalysts.

Hexagonal boron nitride (h-BN) has emerged as a strong candidate for two-dimensional (2D) material owing to its exciting optoelectrical properties combined with mechanical robustness, thermal stability, and chemical inertness. Super-thin h-BN layers have gained significant attention from the scientific community for many applications, including nanoelectronics, photonics, biomedical, anti-corrosion, and catalysis, among others. This review provides a systematic elaboration of the structural, electrical, mechanical, optical, and thermal properties of h-BN followed by a comprehensive account of state-of-the-art synthesis strategies for 2D h-BN, including chemical exfoliation, chemical, and physical vapor deposition, and other methods that have been successfully developed in recent years. It further elaborates a wide variety of processing routes developed for doping, substitution, functionalization, and combination with other materials to form heterostructures. Based on the extraordinary properties and thermal-mechanical-chemical stability of 2D h-BN, various potential applications of these structures are described.

Although Li-ion batteries have revitalized the energy storage platform, higher energy density for long-range applications is still a challenge. Beyond Li-ion, Li-S battery could be one of the most promising technologies, but challenges such as lithium polysulfide shuttling, sluggish reaction kinetics and low areal sulfur loading (

Alkali and alkaline earth metal-ion batteries are currently among the most efficient electrochemical energy storage devices. However, their stability and safety performance are greatly limited when used with volatile organic liquid electrolytes. A solid state polymer electrolyte is a prospective solution even though poor ionic conductivity at room temperature remains a bottleneck. Here we propose the mixing of two similar polymer matrices, poly(dimethyl siloxane) and poly(ethylene oxide), to address this challenge. The resulting electrolyte matrix is denser and significantly improves room-temperature ionic conductivity. Ab initio analyses of the reaction between the cations and the polymers show that oxygen sites act as entrapment sites for the cations and that ionic conduction likely occurs through hopping between adjacent oxygen sites. Molecular dynamics simulations of the dynamics of both polymers and the dynamics of the polymer mix show that the more frequent and more pronounced molecular vibrations of the polymer mix are likely responsible for reducing the time between two consecutive oxygen entrapments, thereby speeding up the conduction process. This hypothesis is experimentally validated by the practically useful ionic conductivity (σ ≈ 10−4 S cm−1 at 25 °C) and the improved safety parameters exhibited by a transparent flexible multi-cation (Li+, Na+ and Mg2+) conducting solid channel made up of the above mixed polymer system.

Positron Annihilation Lifetime Spectroscopy (PALS) is used to study the nanoporosity and fractional free volume in Ultra High Molecular Weight Polyethylene (UHMWPE) and composites with the addition of Martian Regolith (UHMWPE-MR) as-made and irradiated with 56Fe heavy ions at an energy of 600 MeV/u to three different doses (10, 32, 64 Gy). The positron lifetime spectra were obtained using 22Na positron source and the spectra were analyzed to two lifetime components using POSFIT program. First short lifetime component around 0.28 ns is related to positron annihilation in material including vacancy defects and the second long lived component around 1.7 ns is due to Positronium formation in free volume pores. UHMWPE-MR composites were shown to be less porous with much lower nanopores concentration compared to the UHMWPE polymer. The average size of the nanopores is around 0.5 nm (obtained from a simple model). Larger variations in positron lifetime parameters are observed with increasing irradiation dose for UHMWPE polymer compared to UHMWPE+MR composites. The 3-point bend test results also showed larger variations with increasing irradiation dose for the UHMWPE polymer. The variations in PALS parameters may indicate an increasing competition between two processes at higher irradiation doses: 1) vacancy defects aggregation and 2) escape of vacancy defects as the local temperature increases at higher doses resulting in increased vacancy defects mobility. Present results clearly indicate a qualitative inverse relationship between nanoscale porosity measured by positron life time and mechanical properties of UHMWPE and its composite with MR.