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Potassium-ion battery (KIB) is a promising technology for large-scale energy storage applications due to their low cost, theoretically high energy density and abundant resources. However, the development of KIBs is hindered by the sluggish K+ transport kinetics and the structural instability of the electrode materials during K+ intercalation/de-intercalation. In the present investigation, we have designed a potassium-ion capacitor (KIC) using layered potassium niobate (K4Nb6O17, KNO) nanosheet arrays as anode and orange-peel derived activated carbons (OPAC) as fast capacitive cathode materials. The systematic electrochemical analysis with the ex-situ characterizations demonstrates that KNO-anode exhibits highly stable layered structure with excellent reversibility during K+ insertion/de-insertion. After optimization, the fabricated KNO//OPAC delivers both a high energy density of 116 Wh/kg and high power density of 10,808 W/kg, which is significantly higher than other similar hybrid devices. The cell also displays long term cycling stability over 5000 cycles, with 87 % of capacity retention. This study highlights the utilization of layered nanosheet arrays of niobates to achieve superior K-storage for KICs, paving the way towards the development of high-performance anodes for post lithium-ion batteries. © 2020

Potassium-ion capacitor (KICs) is an emerging technology that can potentially combines the virtue of high power capability of supercapacitors and high energy density of batteries. Herein, we have scientifically transformed blue denim textile waste into two different forms of nanocarbons to assemble dual carbon potassium-ion hybrid capacitor (KIHC). The unique composition of indigo and sulphur dyes in blue jeans enables to produce multi-heteroatom (nitrogen, sulphur and oxygen) doped hard carbon (MHC) with large interlayer spacing (0.41 nm) in a single step. An in-situ transmission electron microscopy (TEM) analysis reveal that the charge stored in disordered and large interlayer spaced graphitic structure enable fast kinetics for efficient potassium-ion transportation. Coupling with an activated carbon foam (ACF)-based cathode, a full cell of potassium-ion capacitor successfully delivers a high energy density of 181 Wh kg−1 at 70.4 W kg−1 and 61.8 Wh kg−1 at 4000 W kg−1, as well as an long lifespan of 5000 cycles with over 89% of capacity retention. These performance statistics match or exceed state-of-the-art values for KIHCs, providing novel strategy to develop dual carbon ion capacitors with high energy and high power capabilities. © 2021

Developing nanogenerators (NGs) is achieved by exploiting the piezoelectric, triboelectric, and pyroelectric effects of both organic and inorganic materials. Many exhibit beneficial electrical properties (dielectric, conductive, or insulating) or have surfaces that are polarizable upon friction or physical contact. Recently, biomass-derived materials and recycled materials, whose electrical activity can be induced, are explored for application in the design of more sustainable, cost-effective, biodegradable, disposable NGs, and have demonstrated a wide range of output (microenergy) power densities. Among them, cellulose, the most abundant biopolymer, is found to offer excellent opportunities for designing and manufacturing NGs with multifunctional capacities. Cellulose can be derived into varied forms with multifunctionalities and physical morphologies. This account provides an overview of how cellulose is utilized in creating NGs based on piezoelectric, triboelectric, and pyroelectric effects. Because the mechanical properties of cellulose are tunable, current research trends on NGs originate with the triboelectric effect. The discussion here focuses on design, fabrication methods, achievable electrical power output, and combinations with other materials and devices. Challenges in efficient fabrication and consistent power densities, and opportunities for integrating different technologies and developing more sustainable (in terms of economic, environmental, and ecological) nature–human–machine interfacial devices are also discussed. © 2021 Wiley-VCH GmbH

Aluminium (Al)-doped ZnO thin films are synthesised by chemical spray pyrolysis technique and investigated their gas sensing properties. X-ray diffraction analysis of the films revealed the formation of hexagonal-phase (wurtzite) of ZnO with orientation along (002) plane. Interestingly, the lattice parameters of Al-doped ZnO films showed a decreasing trend with Al doping, suggesting incorporation of Al in the crystal lattice of ZnO. A significant change in both the volume of the unit cell and bond length with an increase in Al concentration is observed. The surface morphological analysis suggested the formation of hexagonal-like ZnO, which transform into spherical particles with Al doping. The energy dispersive spectra confirm the existence of Al, Zn and O. The optical absorption analysis showed that the bandgap of ZnO samples decreases from 3.28 eV to 3.21 eV with Al content in ZnO. The ammonia gas sensing properties of ZnO and Al-doped ZnO are studied at 25 ppm concentration of ammonia gas in air at 100 °C temperature, suggesting reasonable gas sensing characteristics.

Graphene and its analog, two-dimensional (2D) layered molybdenum disulphide (MoS2), have been used for ‘clean energy’ applications in the last several years because of their remarkable electrochemical, optical, and magnetic properties. Their huge success and application potential in various fields has led to the investigation of new 2D nanomaterials which cross the boundaries of existing graphene-based devices. The combination of chemically inert graphene and redox-active MoS2 in a single electrode is providing new opportunities to improve the performance of energy devices and circumvent existing limitations. This article updates our previous review on advances in graphene-MoS2 hybrids for energy-oriented applications. In particular, a summary of recent developments in the synthesis of the graphene-MoS2 hybrids, with an emphasis on energy storage and hydrogen production, is provided. Future challenges and opportunities associated with the development of 2D hybrid materials, and their applications in energy storage systems, are discussed.

The giant wheel-shaped Na15{[Mo154O462H14(H2O)70]0.5[Mo152O457H14(H2O)68]0.5}·ca. 400 H2O (Mo154) is one of the fascinating clusters with the open host framework, which is designed by simple metal-oxygen fragment–linked coordination modes. The generation of structural vacancies (here referred to as defects), the substitution of ligands, and incorporation of heterometallic centers in Mo154 could offer several attractive possibilities to achieve good electrochemical performance such as high specific capacity and stability in multivalent batteries. Herein, we have introduced electronically rich giant nanowheel Mo154 as a potential cathode material in magnesium-rechargeable batteries (MRBs). The experimental evidence indicates that the Mo154 wheels offer a reversible capacity of ∼150 mAh g−1 at 50 mA g−1 in MRBs, which was retained to about 55 mAh g−1 after a long cycling life (>500 cycles). Typically, the divalent alkali metals (Mg2+) suffer from diffusion and insertion reactions in host materials; however, the stable and high rate performance against cycling with good Coulombic efficiency was achieved for Mo154 electrodes. Thus, the work demonstrates that the complex inorganic clusters are promising cathode materials in multivalent ion batteries.