Titanium oxynitride coated graphite paper electrodes for light-weight supercapacitors

The rapid development of smart electronics devices has stimulated intensive research on flexible supercapacitors with high mechanical tolerance and energy density. Up to date, most of the asymmetric devices are fabricated using carbon-based materials as negative electrode materials. However, the lower capacitance of carbon-based materials limited its applicability widely. Also, the device unavoidably carries unnecessary mass and volume, leads to poor contact and performance to repeated bending of devices, and occupies more space in the electronics devices. Herein, we prepared flexible, light-weight, and thin graphite paper current collectors to fabricate flexible supercapacitors. Further, the titanium oxynitride (TiOxNy) coatings were deposited by DC magnetron sputtering over a flexible and light-weight graphite substrate as a potential negative electrode. The presence of nitrogen content in transition metal oxynitrides adds wettability to the material; hence more electrolyte ions get adsorps onto the surface of the electrode owing to their hydrophilic nature. The resultant TiOxNy/graphite electrode exhibited a high areal capacitance of 62 mF cm−2 and also showed 100% capacitance retention even after 1500 GCD cycles. The results of a series of tests indicated that the flexible electrode has better capacitive performance, suggesting that as-prepared film is a favorable candidate for light-weight and flexible supercapacitors.publishe

Rapid synthesis of vertically aligned α-MoO₃ nanostructures on substrates

We report a new procedure for large scale, reproducible and fast synthesis of polycrystalline, dense, vertically aligned α-MoO3 nanostructures on conducting (FTO) and non-conducting substrates (Si/SiO2) by using a simple, low-cost hydrothermal technique. The synthesis method consists of two steps, firstly formation of a thermally evaporated Cr/MoO3 seed layer, and secondly growth of the nanostructures in a highly acidic precursor solution. In this report, we document a growth process of vertically aligned α-MoO3 nanostructures with varying growth parameters, such as pH and precursor concentration influencing the resulting structure. Vertically aligned MoO3 nanostructures are valuable for different applications such as electrode material for organic and dye-sensitized solar cells, as a photocatalyst, and in Li-ion batteries, display devices and memory devices due to their high surface area.publishe

Oxygen vacancies in oxidized and reduced vertically aligned α-MoO₃ nanoblades

Functionalized materials are highly desired for technological advancements spanning physics, chemistry, materials science, and biology due to their unique electronic properties. One such example is molybdenum trioxide (MoO3), a metal oxide with multiple oxidation states. Manipulating these oxidation states can alter the electronic properties, for instance, defects and electrical conductivity, by several orders of magnitude. In this work, oxygen vacancy-mediated intrinsic defects in vertically aligned a-MoO3 crystals are systematically tuned via thermal treatment under different reducing and oxidizing atmospheres. The positions and the concentration of the oxygen vacancies and restitution of the oxygen ions have been experimentally demonstrated via a range of techniques including electron paramagnetic resonance, X-ray diffraction, and high-resolution electron microscopy. The calculated concentration of the oxygen vacancies in the a-MoO3-x via EPR measurements is in the range of x = 0.004–0.049. The mechanism of the formation of oxygen vacancies in the a-MoO3-x crystal is understood via color center formation and polaron migration models. These oxygen vacancies show no influence on the optical band gap. However, they significantly impact the electrical conductivity on the order of 102 Sm-1 by altering the MoO3 properties from semi-insulating to conducting.publishe