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In the recent times research towards solid state supercapacitors (SSS) have increased drastically due to the promising performance in futuristic technologies particularly in portable and flexible electronics like smart watches, smart fabrics, foldable smartphones and tablets. Also, when compared to supercapacitors using liquid electrolyte, solid electrolyte has several advantages like high energy density, safety, high cycle life, flexible form factor, and less environmental impact. The crucial factor determining the sustainability of a technology is the eco‐friendliness since the natural resources are being exploited in a wide scale. Numerous studies have focused on biodegradable materials for supercapacitor electrodes, electrolytes, and other inactive components. Making use of these biodegradable materials to design a SSS enables the technology to sustain for a very long time since biodegradable materials are not only environment friendly but also, they show relatively high performance. This review focuses on recent progress of different biodegradable electrodes, and electrolytes along with their properties, electrochemical performance and biodegradable capabilities for SSS have been analyzed and provides a concise summary enabling readers to understand the importance of biodegradable materials and to narrow down the research in a more rational way. [ABSTRACT FROM AUTHOR]

Mixed multimetallic-based nanocomposites have been considered a promising functional material giving a new dimension to environmental remediation and energy storage applications. On this concept, a hybrid ternary CoO/Ni(OH)2/Cu(OH)2 (CNC) composite showing sea-urchin-like morphology was synthesized via one-pot hydrothermal approach, and its photocatalytic and electrochemical performances were investigated. The photocatalytic performance was explored using Congo red (CR) as a dye pollutant under visible light illumination. The presence of mixed phases of ternary metal ions could minimize the recombination efficacy of photogenerated charge carriers on the basis of the heterojunction mechanism, resulting in 90% degradation of CR dye (40 mg L−1). The effect of scavengers coupled with electrochemical experiments revealed O2−. radical as the predominating species responsible for the degradation of CR. From the electrochemical analysis of CNC, the well-distinguished redox peaks indicated the redox-type nature with a specific capacity of 405 C g−1. For practical applications, an supercapattery (CNC(+)|KOH|AC(−)) was assembled furnishing an energy density of 42 W h kg−1 at a power density of 5160 W kg−1 at 5 A g−1 along with a high capacity retention and coulombic efficiency of 98.83% over 5000 cycles. [ABSTRACT FROM AUTHOR]

Energy generation can be clean and sustainable if it is dependent on renewable resources and it can be prominently utilized if stored efficiently. Recently, biomass-derived carbon and polymers have been focused on developing less hazardous eco-friendly electrodes for energy storage devices. We have focused on boosting the supercapacitor's energy storage ability by engineering efficient electrodes in this context. The well-known conductive polymer, polyaniline (PANI), deposited on nickel foam (NF) is used as a positive electrode, while the activated carbon derived from jute sticks (JAC) deposited on NF is used as a negative electrode. The asymmetric supercapacitor (ASC) is fabricated for the electrochemical studies and found that the device has exhibited an energy density of 24 µWh/cm2 at a power density of 3571 µW/cm2. Furthermore, the ASC PANI/NF//KOH//JAC/NF has exhibited good stability with ~86% capacitance retention even after 1000 cycles. Thus, the enhanced electrochemical performances of ASC are congregated by depositing PANI on NF that boosts the electrode's conductivity. Such deposition patterns are assured by faster ions diffusion, higher surface area, and ample electroactive sites for better electrolyte interaction. Besides advancing technology, such work also encourages sustainability. [ABSTRACT FROM AUTHOR]

• Facile, solid-state, low temperature synthesized layered molybdenum boride found out to be of thin nanosheets. • MoB are found to be electrochemically active in acid and neutral electrolyte, where the nanosheets provide a higher surface area for the electrolyte ion interaction. • MoB was directly employed as a negative electrode, against the activated carbon as a positive electrode for the asymmetric supercapacitors. • The device was found to deliver a high energy density and power density with long-term stability in charge/discharge cyclings. • Interestingly, it was discovered that the outcomes of the electrochemical performance of asymmetric supercapacitors could be tuned by the electrolyte. [Display omitted] The survey of 2D materials has triggered the energy storage and conversion research. In molybdenum-based 2D layered materials are of great significance, due to their remarkable properties. In this work, simple solid-state synthesis and formation of molybdenum boride has been explored with various characteristic techniques. The advanced characterization techniques like XRD, TEM, XPS, BET, have been used to understand the crystallinity, morphology, and surface area of the layered MoB (LMB). The electrochemical performances of LMB electrode were verified with different aqueous electrolytes. The LMB electrode has been found to store higher charge in H 2 SO 4 than Na 2 SO 4 electrolyte. The LMB electrode delivered a specific capacitance of 445 F g−1 in H 2 SO 4 where 130 F g−1 in Na 2 SO 4 at a current density of 1 A g−1. Such behavior may be due to ionic size and mobility of ions in the electrolyte. The asymmetric supercapacitors have been fabricated with LMB and activated carbon (AC) electrode then the device performance was examined in both the electrolyte. On optimization, it was found the device works well in potential window 1.4 V in H 2 SO 4 while the potential window was extended to 1.8 V in Na 2 SO 4 electrolyte. The device was found to deliver an energy density of 14 W h kg−1 at a power density of 16.8 kW kg−1 for H 2 SO 4 with a better capacity retention of 98% for 2000 cycles. Thus, LMB electrode in supercapacitor application has been demonstrated for the first time, which can instigate more investigations for layered molybdenum-based electrodes for energy storage devices. [ABSTRACT FROM AUTHOR]