CuO–ZnO nanocomposites (NCs) were synthesized using an aqueous extract of Verbascum sinaiticum Benth. (GH) plant. X-ray diffraction (XRD), spectroscopic, and microscopic methods were used to explore the crystallinity, optical properties, morphology, and other features of the CuO–ZnO samples. Furthermore, catalytic performances were investigated for methylene blue (MB) degradation and 4-nitrophenol (4-NP) reduction. According to the results, CuO–ZnO NCs with 20 wt % CuO showed enhanced photocatalytic activity against MB dye with a 0.017 min –1 rate constant compared to 0.0027 min –1 for ZnO nanoparticles (NPs). Similarly, a ratio constant of 5.925 min –1 g –1 4-NP reductions was achieved with CuO–ZnO NCs. The results signified enhanced performance of CuO–ZnO NCs relative to ZnO NPs. The enhancement could be due to the synergy between ZnO and CuO, resulting in improved absorption of visible light and reduced electron–hole (e – /h + ) recombination rate. In addition, variations in the CuO content affected the performance of the CuO–ZnO NCs. Thus, the CuO–ZnO NCs prepared using V. sinaiticum Benth. extract could make the material a desirable catalyst for the elimination of organic pollutants.
Water splitting driven by renewable energy sources is considered a sustainable way of hydrogen production, an ideal fuel to overcome the energy issue and its environmental challenges. The rational design of electrocatalysts serves as a critical point to achieve efficient water splitting. Layered double hydroxides (LDHs) with two-dimensionally (2D) layered structures hold great potential in electrocatalysis owing to their ease of preparation, structural flexibility, and tenability. However, their application in catalysis is limited due to their low activity attributed to structural stacking with irrational electronic structures, and their sluggish mass transfers. To overcome this challenge, attempts have been made toward adjusting the morphological and electronic structure using appropriate design strategies. This review highlights the current progress made on design strategies of transition metal-based LDHs (TM-LDHs) and their application as novel catalysts for oxygen evolution reactions (OERs) in alkaline conditions. We describe various strategies employed to regulate the electronic structure and composition of TM-LDHs and we discuss their influence on OER performance. Finally, significant challenges and potential research directions are put forward to promote the possible future development of these novel TM-LDHs catalysts.
Copper oxide is considered as an alternative electrode material for supercapacitors due to its low cost, chemical stability and high theoretical specific capacitance. In the present work, nanostructured copper oxide (CuO) films are prepared by radio-frequency (RF) magnetron sputtering, and the influence of the substrate temperature on the microstructure and supercapacitive properties was studied. The copper oxide films prepared at 350 °C exhibit a predominant (1¯11) orientation corresponding to the monoclinic Cu(II)O phase with a crystallite size of 24 nm. The surface of the film consists of uniformly distributed oval-like grains providing a high surface roughness of 45 nm. The films exhibit an optical bandgap of 1.68 ± 0.01 eV and an electrical conductivity of 0.4 S cm−1 at room temperature. The as-prepared CuO films deliver a discharge specific capacitance of 387 mF cm−2 (375 F g−1) at a current density of 1 mA cm−2 with excellent cyclic capacitance retention of 95% (367 mF cm−2) even after 1000 cycles. Hence, these films are potential electrodes for micro-supercapacitors.
A feasible nanoscale framework of heterogeneous plasmonic materials and proper surface engineering can enhance photoelectrochemical (PEC) water‐splitting performance owing to increased light absorbance, efficient bulk carrier transport, and interfacial charge transfer. This article introduces a new magnetoplasmonic (MagPlas) Ni‐doped Au@FexOy nanorods (NRs) based material as a novel photoanode for PEC water‐splitting. A two stage procedure produces core–shell Ni/Au@FexOy MagPlas NRs. The first‐step is a one‐pot solvothermal synthesis of Au@FexOy. The hollow FexOy nanotubes (NTs) are a hybrid of Fe2O3 and Fe3O4, and the second‐step is a sequential hydrothermal treatment for Ni doping. Then, a transverse magnetic field‐induced assembly is adopted to decorate Ni/Au@FexOy on FTO glass to be an artificially roughened morphologic surface called a rugged forest, allowing more light absorption and active electrochemical sites. Then, to characterize its optical and surface properties, COMSOL Multiphysics simulations are carried out. The core–shell Ni/Au@FexOy MagPlas NRs increase photoanode interface charge transfer to 2.73 mAcm−2 at 1.23 V RHE. This improvement is made possible by the rugged morphology of the NRs, which provide more active sites and oxygen vacancies as the hole transfer medium. The recent finding may provide light on plasmonic photocatalytic hybrids and surface morphology for effective PEC photoanodes.
Transition metal based layered double hydroxides (TMLDHs) are potential candidates for supercapacitors; however, their structural staking often limits their energy density, one of the major pending obstacles in the sector. Simple, fast, and safe modification strategies such as exfoliation of jammed layers into single sheets can be a viable option to overcome those challenges. This work reports fabrication of an ultrathin nanosheets from bulk TMLDHs using superficial non-thermal Arplasma exfoliation strategy. Electrochemical characterizations have confirmed that capacitive performance of pristine NiCoO x nanosheets has improved because of Ar-plasma induced exfoliation. A remarkable of 5.7 F cm À 2 areal capacitance was achieved at a current density of 5 mA cm À 2 for ultrathin Ar-NiCoO x nanosheets. The material also exhibited excellent cyclic stability with over 88 % capacitance retention after 5000 cycles. The electrode material assembled into symmetric supercapacitor device delivering an energy density of 85.9 μWh cm À 2 at a power density of 500 μW cm À 2 .The higher supercapacitive performance is attributed to increased electrochemical surface area and improved capability of electron and ion transport induced by Ar-plasma exfoliation, demonstrating an opportunity for further use of TMLDHs in the energy conversion and storage sector.
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