Flexible supercapacitors (SCs) are an emergent and promising technology for next-generation energy storage devices. However, low energy densities hindered their practical applications. Two-dimensional (2D) nanosheets can exhibit excellent electrochemical charge storage properties due to their short ion-diffusion distance and rich electroactive sites with multiple valence states. Herein, we report the direct growth of mesoporous 2D zinc cobaltite nanosheets on a flexible carbon cloth substrate (Zn–Co–O@CC) with an average thickness of ∼45 nm by a facile hydrothermal method at low temperature. The Zn–Co–O@CC electrode displays a high capacitance of 1750, 1573.65 and 1434.37 F g⁻¹ at a current density of 1.5 A g⁻¹ in LiCl, NaCl and KCl neutral aqueous electrolytes, respectively, with excellent rate capabilities at high current densities and demonstrates good cycling stability (>94%) for up to 5000 cycles. Moreover, highly flexible asymmetric supercapacitor (ASC) devices have been fabricated using Zn–Co–O@CC as a positive electrode and bimetallic organic framework (MOF)-derived nanoporous carbon polyhedra (NPC@CC) as a negative electrode (Zn–Co–O@CC//NPC@CC). The as-fabricated ASC can operate at a large potential window of 0.0–2.0 V and shows outstanding energy storage performance by delivering an ultra-high energy density of 117.92 W h kg⁻¹ at a power density of 1490.4 W kg⁻¹ with a cycling stability of 94% after 5000 charge/discharge cycles. To the best of our knowledge, the achieved energy storage performance of the ASC device is very competitive and the highest among all binary metal oxides, carbonaceous materials, and MXene-based SCs and ASCs to date. The applied strategy to fabricate SCs is capable of enhancing both electrochemical activity and cycling stability, and can be readily applied to other metal oxide-based SCs.

Today’s world needs highly efficient systems that can fulfill the growing demand for energy. One of the promising solutions is the fuel cell. Solid oxide fuel cell (SOFC) is considered by many developed countries as an alternative solution of energy in near future. A lot of efforts have been made during last decade to make it commercial by reducing its cost and increasing its durability. Different materials, designs and fabrication technologies have been developed and tested to make it more cost effective and stable. This article is focused on the advancements made in the field of high temperature SOFC. High temperature SOFC does not need any precious catalyst for its operation, unlike in other types of fuel cell. Different conventional and innovative materials have been discussed along with properties and effects on the performance of SOFC’s components (electrolyte anode, cathode, interconnect and sealing materials). Advancements made in the field of cell and stack design are also explored along with hurdles coming in their fabrication and performance. This article also gives an overview of methods required for the fabrication of different components of SOFC. The flexibility of SOFC in terms fuel has also been discussed. Performance of the SOFC with varying combination of electrolyte, anode, cathode and fuel is also described in this article.

Semiconductors and the associated methodologies applied to electrochemistry have recently grown as an emerging field in energy materials and technologies. For example, semiconductor membranes and heterostructure fuel cells are new technological trend, which differ from the traditional fuel cell electrochemistry principle employing three basic functional components: anode, electrolyte, and cathode. The electrolyte is key to the device performance by providing an ionic charge flow pathway between the anode and cathode while preventing electron passage. In contrast, semiconductors and derived heterostructures with electron (hole) conducting materials have demonstrated to be much better ionic conductors than the conventional ionic electrolytes. The energy band structure and alignment, band bending and built-in electric field are all important elements in this context to realize the necessary fuel cell functionalities. This review further extends to semiconductor-based electrochemical energy conversion and storage, describing their fundamentals and working principles, with the intention of advancing the understanding of the roles of semiconductors and energy bands in electrochemical devices for energy conversion and storage, as well as applications to meet emerging demands widely involved in energy applications, such as photocatalysis/water splitting devices, batteries and solar cells. This review provides new ideas and new solutions to problems beyond the conventional electrochemistry and presents new interdisciplinary approaches to develop clean energy conversion and storage technologies. Graphic Abstract

By integrating the design principles of broadband metamaterial absorbers with woven structures, this study introduces a woven composite metamaterial (WCM) made of resin and AlCuFe quasicrystals, enabling optical materials to operate efficiently across a wide spectral range while withstanding mechanical deformation. This lightweight metamaterial features a unique 3D four-way braided structure combined with Dirac semimetals. Static analysis reveals that AlCuFe quasicrystals significantly enhance mechanical properties, with a Young's modulus reaching 38 GPa in the z direction and 18 GPa in the x and y directions at 40% fiber content and a 30° weaving angle. Frequency domain simulations show a high average absorption rate of 83.4% in the 3–12 μm range, primarily due to internal electromagnetic coupling. The study further reveals that the electromagnetic properties of the WCM are closely related to fiber content and weaving angle. As a lightweight optical material, the WCM shows strong application potential in fields such as aerospace and electromagnetic countermeasures.

Electrochemical energy storage and conversion systems such as electrochemical capacitors, batteries and fuel cells are considered as the most important technologies proposing environmentally friendly and sustainable solutions to address rapidly growing global energy demands and environmental concerns. Their commercial applications individually or in combination of two or more devices are based on their distinguishing properties e.g., energy/power densities, cyclability and efficiencies. In this review article, we have discussed some of the major electrochemical energy storage and conversion systems and encapsulated their technological advancement in recent years. Fundamental working principles and material compositions of various components such as electrodes and electrolytes have also been discussed. Furthermore, future challenges and perspectives for the applications of these technologies are discussed.