Fabrication of ionic liquid based D-Ti3C2/MoO3 hybrid electrode system for efficient energy storage applications

Heterostructures of MXenes and transition metal oxides for supercapacitors: an overview

MXenes are a large family of two dimensional (2D) materials with high conductivity, redox activity and compositional diversity that have become front-runners in the materials world for a diverse range of energy storage applications. High-performing supercapacitors require electrode materials with high charge storage capabilities, excellent electrical conductivity for fast electron transfer, and the ability of fast charging/discharging with good cyclability. While MXenes show many of these properties, their energy storage capability is limited by a narrow electrochemically stable potential window due to irreversible oxidation under anodic potentials. Although transition metal oxides (TMOs) are often high-capacity materials with high redox activity, their cyclability and poor rate performance are persistent challenges because of their dissolution in aqueous electrolytes and mediocre conductivity. Forming heterostructures of MXenes with TMOs and using hybrid electrodes is a feasible approach to simultaneously increase the charge storage capacity of MXenes and improve the cyclability and rate performance of oxides. MXenes could also act as conductive substrates for the growth of oxides, which could perform as spacers to stop the aggregation of MXene sheets during charging/discharging and help in improving the supercapacitor performance. Moreover, TMOs could increase the interfacial contact between MXene sheets and help in providing short-diffusion ion channels. Hence, MXene/TMO heterostructures are promising for energy storage. This review summarizes the most recent developments in MXene/oxide heterostructures for supercapacitors and highlights the roles of individual components.

Ternary Metal (Cu-Ni-Zn) Oxide Nanocomposite via an Environmentally Friendly Route

In this work, we report the engineering of sub-30 nm nanocomposites of CuO/ZnO/NiO by using Dodonaea viscosa leaf extract. Zinc sulfate, nickel chloride, and copper sulfate were used as salt precursors, and isopropyl alcohol and water were used as solvents. The growth of nanocomposites was investigated by varying the concentrations of precursors and surfactants at pH 12. The as-prepared composites were characterized by XRD analysis and found to have CuO (monoclinic), ZnO (hexagonal primitive), and NiO (cubic) phases with an average size of 29 nm. FTIR analysis was performed to investigate the mode of fundamental bonding vibrations of the as-prepared nanocomposites. The vibrations of the prepared CuO/ZnO/NiO nanocomposite were detected at 760 and 628 cm^-1, respectively. The optical bandgap energy of the CuO/NiO/ZnO nanocomposite was 3.08 eV. Ultraviolet-visible spectroscopy was performed to calculate the band gap by the Tauc approach. Antimicrobial and antioxidant activities of the synthesized CuO/NiO/ZnO nanocomposite were investigated. It was found that the antimicrobial activity of the synthesized nanocomposite increases with an increase in the concentration. The antioxidant activity of the synthesized nanocomposite was examined by using both ABTS and DPPH assays. The obtained results show an IC₅₀ value of 0.110 for the synthesized nanocomposite compared to DPPH and ABTS (0.512), which is smaller than that of ascorbic acid (IC₅₀ = 1.047). Such a low IC₅₀ value ensures that the antioxidant potential of the nanocomposite is higher than that of ascorbic acid, which in turn shows their excellent antioxidant activity against both DPPH and ABTS.

Conductivity and aging behavior of Sr(Ti0.6Fe0.4)1-x O3-δ mixed conductor materials

Perovskite materials play a significant role in oxygen sensors due to their fascinating electrical and ionic conductivities. The sol-gel technique was employed to prepare various compositions of B-site-deficient Fe-doped SrTiO3 (iron-doped strontium titanate) or Sr(Ti0.6Fe0.4)1-x O3-δ , where x = 0.01, 0.02, and 0.03. The XRD results revealed that the principle crystalline phase of the samples was the cubic perovskite structure. The B-site deficiency improved the ionic and total conductivities of Sr(Ti0.6Fe0.4)1-x O3-δ . A small polaron conduction behavior occurred in the total electrical conductivity. The XPS results showed that the oxygen vacancy value decreased with the rise in the amount of B-site deficiencies. A lower B-site deficiency amount could produce more oxygen vacancies in the lattice but resulted in the ordering of vacancies and then lower ionic conductivity. The aging behavior was caused by the ordering of oxygen vacancies and resulted in a degeneration of electrical features under a long service time. Conversely, augmentation of the B-site deficiency amount inhibited the tendency for the ordering of oxygen vacancies and then promoted the electrical performance under a long usage time. The conduction mechanism of oxygen ions through oxygen vacancies was thoroughly investigated and discussed. The current study presents a feasible approach to ameliorate the physical features of conductors through doping the B-site of the perovskite layer with Fe, which would be a fruitful approach for numerous applications, including oxygen sensors and fuel cells anodes.

Experimental and Theoretical Studies on Optical Properties of Tetra(Imidazole) of Palladium (II) Phthalocyanine

In this work, the optical properties of tetra(imidazole) of palladium phthalocyanine (PdPc(Im)₄) in solution form and thin films on glass and fluorine-doped tin oxide (FTO) substrates were investigated via the thermal evaporation technique. The optical band gap was evaluated by ultraviolet–visible spectroscopy (UV-Vis). The energy band gap values were determined based on the Tauc graph. In addition, time-dependent density functional theory (TD-DFT) was used to simulate the UV-Vis absorption spectrum of the (PdPc(Im)₄) molecule in the Dimethyl Sulfoxide (DMSO) solution phase. A good correlation was found between the DFT results and the experimental optical results. The band gap values between the experimental and DFT-simulated values are presented. The energy band gap of (PdPc(Im)₄) obtained from the DFT calculations showed that it can be efficiently regulated. Frontier molecular orbitals and molecular electrostatic potentials were also proposed in this work. The surface study of the layers deposited on FTO was considered by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and the results demonstrated good homogeneity covering the entire surface. The SEM image showed a homogeneous distribution of the grains with some spherical or rod-shaped structures and no agglomeration structures. This work rendered a strategy for regulating the energy band gap and compared the experimental observations obtained with theoretical studies, which provides a fundamental insight into the optical band for optoelectronic and thin-film solar cells.