Self-assembled CuO nanosheet bundles are fabricated on stainless steelviachemical bath deposition and optimized for efficient electrocatalysis.

A supercapacitor is well recognized as one of emerging energy sources for powering electronic devices in our daily life. Although various kind of supercapacitors have been designed and demonstrated, their market aspect could become advanced if the utilisation of other physicochemical properties (e.g. optical) is incorporated in the electrode. Herein, we present an electrochromic supercapacitor (smart supercapacitor) based on a nanoflake NiMoO 4 thin film which is fabricated using a facile and well-controlled successive ionic layer adsorption and reaction (SILAR) technique. The polycrystalline nanoflake NiMoO 4 electrode exhibits a large electrochemically active surface area of ~ 96.3 cm 2. Its nanoporous architecture provides an easy pathway for the intercalation and de-intercalation of ions. The nanoflake NiMoO 4 electrode is dark-brown in the charged state and becomes transparent in the discharged state with a high optical modulation of 57 %. The electrode shows a high specific capacity of 1853 Fg-1 at a current rate of 1Ag-1 with a good coloration efficiency of 31.44 cm 2 /C. Dynamic visual information is obtained when the electrode is charged at different potentials, reflecting the level of energy storage in the device. The device retains 65% capacity after 2500 charge-discharge *Manuscript Click here to view linked References 2 cycles compared with its initial capacity. The excellent performance of the nanoflake NiMoO 4 based smart supercapacitor is associated with the synergetic effect of nanoporous morphology with a large electrochemically active surface area and desired chemical composition for redox reaction.

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Summary The outstanding multifunctional electrochemical properties of chalcogenide‐based FeO@CuCo2S4, such as electrochemical energy storage (EES) and electrocatalytic oxygen evolution reaction are demonstrated. The FeO@CuCo2S4 film is fabricated using a two‐step synthesis procedure. First, CuCo2S4 was grown on 3D porous nickel foam substrate using a mild hydrothermal growth technique, onto which FeO was then deposited via a magnetron sputtering. The FeO@CuCo2S4 film shows a cordillera‐like morphology with a uniformly distributed island‐like nanospheres on its surface. The optimized FeO@CuCo2S4 electrode delivers an ultrahigh specific capacitance of 3213 F g−1 at 1 A g−1. This FeO@CuCo2S4 electrode shows superior capacity retention and coulombic efficiency of ~116% and ~99%, respectively, after 10 000 charge/discharge stability cycles. Moreover, this superior electrode is also serves as an OER electrocatalyst in alkaline solution (1 M aqueous KOH), demonstrating better catalytic activity by attaining a low overpotential of ~240 mV at 10 mA cm−2 and a small Tafel slope of 51 mV dec−1. This FeO@CuCo2S4 catalyst has excellent current rate performance and endurance properties at a high current density rate of up to 100 mA cm−2 even after 25 hours. The post‐measurement HR‐TEM, EDS‐STEM mapping, and Raman analysis reveal the phase transformation of FeO@CuCo2S4 upon electro‐oxidation.

Ultrathin graphene nanosheets were derived from rice husks via KOH activation and they showed excellent electrochemical performances.

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Ultrathin nanoporous CuCo2O4 nanosheets can be synthesized on nickel foam (NF) via an electrodeposition method followed by air annealing treatment. The electrochemical energy storage and oxygen evolution reaction (OER) properties are studied in aqueous 1M KOH solution. The CuCo2O4 nanosheet electrode exhibits a high specific capacitance of 760 F/g at 1 A/g with a capacity retention of ~ 85% after 5000 cycles and 1473 F/g at 1 A/g in 3M KOH solution. The CuCo2O4 nanosheet electrode works as a highly efficient OER electrocatalyst, demonstrating an overpotential of 260 mV at 20 mA/cm 2 with a Tafel slope of ~ 64 mV/dec., which is the lowest among other copper-cobalt based transition metal oxide catalysts. The catalyst is very stable at > 20 mA/cm 2 for more than 25 h. The superior electrochemical performance of the CuCo2O4 nanosheets is due to the synergetic effect of the direct growth of 2D nanosheet structure and a large electrochemically active surface area associated with nanopores on the CuCo2O4 nanosheet surface.

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