Syam Kandula

By changing the mixed metal sulfide composition, morphology tuning of the active electrode material can be possible, which can show a huge impact on its electrochemical performance. Here, an effective morphology tuning of the NiCo LDH/MMoSx (M = Co, Ni, and Zn) heteronanostructures is demonstrated by varying the composition of the MMoSx. Taking advantage of the benefits associated with Kirkendall growth and Ostwald ripening, tunable morphologies were successfully achieved. Among the NiCo LDH/MMoSx (M = Co, Ni, and Zn) heteronanostructures, the NiCo LDH/NiMoSx core-shell structured electrode delivers high specific capacity of 404 mA h gat 3 mA cm, as well as extraordinary cycling stability (after 10,000 cycles) of 93.2 % at 50 mA cm. In addition, ASC device coupled with NiCo LDH/NiMoSx as a cathode and Fe2O3/rGO as an anode exhibits excellent cell capacity and extraordinary cycling stability. Moreover, ASC device provides very high specific energy of 72.6 Wh kg1 at a specific power of 522.7 W kg1 and maintained the specific energy of 23.5 Wh kg at 5357.6 W kg demonstrating high applicability to energy storage devices.

The scalable and cost‐effective H₂ fuel production via electrolysis demands an efficient earth‐abundant oxygen and hydrogen evolution reaction (OER, and HER, respectively) catalysts. In this work, for the first time, the synthesis of a sheet‐like Zn_1‐xFe_x–oxyselenide and Zn_1‐xFe_x–LDH on Ni‐foam is reported. The hydrothermally synthesized Zn_1‐xFe_x–LDH/Ni‐foam is successfully converted into Zn_1‐xFe_x–oxyselenide/Ni‐foam through an ethylene glycol‐assisted solvothermal method. The anionic regulation of electrocatalysts modulates the electronic properties, and thereby augments the electrocatalytic activities. The as‐prepared Zn_1‐xFe_x–LDH/Ni‐foam shows very low OER and HER overpotentials of 263 mV at a current density of 20 mA cm⁻² and 221 mV at 10 mA cm⁻², respectively. Interestingly, this OER overpotential is decreased to 256 mV after selenization and the HER overpotential of Zn_1‐xFe_x–oxyselenide/Ni‐foam is decreased from 238 to 202 mV at 10 mA cm⁻² after a stability test. Thus, the Zn_1‐xFe_x–oxyselenide/Ni–foam shows superior bifunctional catalytic activities and excellent durability at a very high current density of 50 mA cm⁻². More importantly, when the Zn_1‐xFe_x–oxyselenide/Ni‐foam is used as the anode and cathode in an electrolyzer for overall water splitting, Zn_1‐xFe_x–oxyselenide/Ni‐foam(+)ǁZn_1‐xFe_x–oxyselenide/Ni‐foam(‐) shows an appealing potential of 1.62 V at 10 mA cm⁻². The anionic doping/substitution methodology is new and serves as an effective strategy to develop highly efficient bifunctional electrocatalysts.

A thin layer of N–C sandwiched between an electroactive MnCo₂O₄ core and MnO₂ shell results in sophisticated, robust core@sandwich@shell as a highly efficient energy storage material.

Photocatalysts suffer from a lack of separation of photogenerated excitons due to the fast recombination of charge carriers, so a strong synergistic effect exhibited by photocatalysts is promising for effective photocatalysis. Herein, we have synthesized efficient visible light functionalized graphene oxide nanosheet (FGS)/ZnO nanocomposite photocatalysts via a simple and economical approach with large scale production for practical applications. A series of nanocomposites (FGS/ZnO NCs) with different amounts by weight of graphene oxide (GO) have been synthesized via a facile solution route followed by calcination under environmental conditions. The phase, purity and morphological studies of the synthesized FGS/ZnO NCs were carried out using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The optical properties were studied using UV-visible diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). XRD results confirm the formation of a pure phase of ZnO in the FGS/ZnO NCs and TEM results show strongly adhered ZnO NPs on the surface of the FGS. DRS results confirm the extension of light absorption in the visible region while PL results confirm the effective separation of charge carriers in 0.09 wt% FGS/ZnO NCs. The synthesized photocatalyst efficiently degrades carcinogenic safranin-T dye under visible light illumination which is reported for the first time using FGS/ZnO nanocomposites. Photocatalytic studies confirm the higher photocatalytic activity of 0.09 wt% FGS/ZnO NCs (about 94.5%) towards the photodegradation of safranin-T dye in aqueous solution under visible light. The improved photocatalytic activity of 0.09 wt% FGS/ZnO NCs can be ascribed to the integrative synergistic effects of the enhanced adsorption capacity of safranin-T dye, effective separation of photogenerated excitons and effective interfacial hybridization of FGS and ZnO NCs. The generation of reactive oxygen species was confirmed using terephthalic acid as a probe molecule and a scavenger test was conducted in presence of histidine.

Supercapacitors suffer from lack of energy density and impulse the energy density limit, so a new class of hybrid electrode materials with promising architectures is strongly desirable. Here, the rational design of a 3D hierarchical sandwich Co₉S₈/α‐MnS@N–C@MoS₂ nanowire architecture is achieved during the hydrothermal sulphurization reaction by the conversion of binary mesoporous metal oxide core to corresponding individual metal sulphides core along with the formation of outer metal sulphide shell at the same time. Benefiting from the 3D hierarchical sandwich architecture, Co₉S₈/α‐MnS@N–C@MoS₂ electrode exhibits enhanced electrochemical performance with high specific capacity/capacitance of 306 mA h g⁻¹/1938 F g⁻¹ at 1 A g⁻¹, and excellent cycling stability with a specific capacity retention of 86.9% after 10 000 cycles at 10 A g⁻¹. Moreover, the fabricated asymmetric supercapacitor device using Co₉S₈/α‐MnS@N–C@MoS₂ as the positive electrode and nitrogen doped graphene as the negative electrode demonstrates high energy density of 64.2 Wh kg⁻¹ at 729.2 W kg⁻¹, and a promising energy density of 23.5 Wh kg⁻¹ is still attained at a high power density of 11 300 W kg⁻¹. The hybrid electrode with 3D hierarchical sandwich architecture promotes enhanced energy density with excellent cyclic stability for energy storage.

Cu₂O@Ag polyhedral core–shell nanoparticles with different morphologies (rhombicuboctahedral, cuboctahedral, truncated octahedral, and octahedral) have been successfully synthesized by a thermal decomposition approach. The Cu₂O@Ag polyhedral core–shell nanoparticles were characterized by X‐ray diffraction, electron microscopy, surface‐area analysis, and diffuse reflectance spectroscopy. The XRD results confirm the presence of Cu₂O and silver in the Cu₂O@Ag samples. Electron microscopy studies prove the formation of a shell of silver nanoparticles on the polyhedral Cu₂O microcrystals. The diffuse reflectance spectra of the Cu₂O@Ag polyhedral core–shell nanoparticles show band‐gap absorption owing to Cu₂O as well as surface plasmon resonance owing to silver nanoparticles. The catalytic activities of the Cu₂O@Ag polyhedral core–shell nanoparticles were explored for the reductions of 4‐nitrophenol and methylene blue in aqueous solutions. The Cu₂O@Ag core–shell nanoparticles with octahedral morphology show higher catalytic activity than the other Cu₂O@Ag samples. The core–shell nanoparticles show a higher turnover frequency (TOF) and activity parameter (k_act) for 4‐nitrophenol reduction and a higher apparent rate constant (k_app) for methylene blue reduction compared to the previously reported values. The reusability of the Cu₂O@Ag polyhedral core–shell nanoparticles was also tested, and they show stability for up to five cycles without loss of efficiency.