Trends on the Development of Hybrid Supercapacitor Electrodes from the Combination of Graphene and Polyaniline

The high demand for efficient energy devices leads to the rapid development of energy storage systems with excellent electrochemical properties, such as long life cycles, high cycling stability, and high power density. SC is postulated as a potential candidate to fulfill this demand. The combination of graphene and polyaniline can create SC electrodes with excellent electrical conductivity, high specific surface area, and high capacitance. The graphene/polyaniline hybrid electrodes represent an attractive means to overcome the major drawbacks of graphene or polyaniline non-hybrid (single) electrode materials. In this review article, the trend in the development of various graphene/polyaniline hybrid electrodes is summarized, which includes the zero-dimension graphene-quantum-dots/polyaniline hybrid, one-dimension graphene/polyaniline hybrid, two-dimension graphene/polyaniline hybrid, and three-dimension hydrogel-shaped graphene/polyaniline hybrid. Several strategies and approaches to enhance the capacitance value and cycling stability of graphene/polyaniline hybrid electrodes are discussed in this review article, such as the addition of transition metal oxides and metal-organic frameworks, and modification of graphene into functionalized-graphene. The performance of the electrodes prepared from the combination of graphene with other conducting polymers (i.e., polypyrrole, polythiophene, and polythiophene-derivatives) is also discussed.

Signatures of enhanced out-of-plane polarization in asymmetric BaTiO3 superlattices integrated on silicon

In order to bring the diverse functionalities of transition metal oxides into modern electronics, it is imperative to integrate oxide films with controllable properties onto the silicon platform. Here, we present asymmetric LaMnO3/BaTiO3/SrTiO3 superlattices fabricated on silicon with layer thickness control at the unit-cell level. By harnessing the coherent strain between the constituent layers, we overcome the biaxial thermal tension from silicon and stabilize c-axis oriented BaTiO3 layers with substantially enhanced tetragonality, as revealed by atomically resolved scanning transmission electron microscopy. Optical second harmonic generation measurements signify a predominant out-of-plane polarized state with strongly enhanced net polarization in the tricolor superlattices, as compared to the BaTiO3 single film and conventional BaTiO3/SrTiO3 superlattice grown on silicon. Meanwhile, this coherent strain in turn suppresses the magnetism of LaMnO3 as the thickness of BaTiO3 increases. Our study raises the prospect of designing artificial oxide superlattices on silicon with tailored functionalities.

John Goodenough and the Many Lives of Transition-Metal Oxides

In honor of John Goodenough's centennial birthday, I discuss some of his insights into magnetism and the role of mixed valence in transition-metal oxides. His ideas form an important part of the continuing evolution of our understanding of these fascinating materials with a wide range of technologically-important functionalities. In particular, will mention connections to phenomena such as colossal magnetoresistance, enhanced thermopower, and high-temperature superconductivity.

Hybrid Sorbents for Removal of Arsenic

The paper analyzes data on the removal of arsenic by sorption methods using materials that have prospects for large-scale application in water treatment. These materials include transition metal oxides in the micro- and nano-dimensional form, including those in the composition of composite materials with inorganic matrices, or hybrid sorbents in the composition with polymer resins or natural biopolymers. Examples of the use of composite (hybrid) sorbents for the removal of arsenic from solutions with low concentrations (at the level of MPC) are given. The objective of this article was to sum the up-to-date information about the most important features of chitosan-containing and chitosan-carbon materials we developed in view their use in arsenic removal processes at low concentrations to concentrations that meet WHO requirements. The paper presents data on the sorption properties of Mo-containing activated carbon fibers and chitosan-carbon composite materials towards arsenic (V) when it is extracted from bidistilled and tap water under static and dynamic conditions. The factors of the different behavior of the sorbents depending on the form of a biopolymer deposited on the fiber and the stability of the sorbents during the sorption of arsenic are discussed.

Theoretical Design of Transition Metal-Doped TiO2 for the Selective Catalytic Reduction of NO with NH3 by DFT Calculations

Many transition metal oxides supported on TiO2 have been studied for selective catalytic reduction (SCR) of NO with NH3. However, the trade-off exists between the low-temperature activity and N2 selectivity....

Thickness Dependent OER Electrocatalysis of Epitaxial LaFeO3 Thin Films

Transition metal oxides have long been an area of interest for water electrocatalysis through the oxygen evolution and oxygen reduction reactions. Iron oxides, such as LaFeO3, are particularly promising due...