Supercapacitors and energy conversion structures based on WS2 and MoS2 disulfides

In this paper, disulfides WS2 and MoS2 were successfully prepared using thermal decomposition and utilised for fabrication of supercapacitor- and water splitting electrodes. Both, energy storage and conversion performances of these electrodes were compared with electrodes prepared with commercial MoS2, WS2, and activated carbon (AC). The electrochemical characterisation confirmed the pseudocapacitive character of disulfide-based supercapacitor electrodes. A strong influence of the scan rate on the specific capacitance was found, which is due to the diffusion of ions and the pseudocapacitive nature of charge storage. A specific capacitance of 405 mF/cm2 at 10 mV/s scan rate was achieved on MoS2 structures prepared by thermal decomposition. This value is 3.5-times greater than the capacitance achieved on commercial MoS2 and 6.8-times greater than capacitance achieved on structures with activated carbon. A specific capacitance of 396 mF/cm2 at 10 mV/s scan rate was achieved on WS2 structures prepared by thermal decomposition, which was 2.2 and 6.7-times greater than the capacitance achieved on commercial WS2 and AC based electrodes, respectively. Water-decomposition structures showed greater catalytic activity of thermally decomposed disulfides for HER compared to commercial materials and AC. The study showed a high perspective of MoS2 and WS2 prepared by thermal decomposition for energy storage applications by means of supercapacitors and energy conversion trough water electrolysis and hydrogen generation.

Corrosion Resistance of Additive Manufactured Titanium Alloy Parts: The Effect of Recycled Powders

The possibility to reduce costs of the additive manufacturing (AM) technologies by using recycled powders is still an open question. The present paper aims to investigate the effect of using virgin and recycled powders on the corrosion resistance of Ti6Al4V titanium alloy additive manufactured parts. Although the study of the electrochemical behaviour of titanium parts produced by using AM is present in the literature, the corrosion resistance of samples manufactured using recycled powders is less investigated. This work would like to contribute to the deepening of this aspect. The experimental investigations have been carried out on as-built samples as well as on samples after mechanical polishing. The metallographic observations of additive manufactured samples showed a martensitic microstructure inside the prior β grain grew up as columnar structure. X-ray diffraction analysis revealed the presence of titanium oxide in rutile crystallographic phase. The electrochemical characterisation unveiled the lower corrosion resistance of the as-built additive manufactured components compared to the traditional counterpart. It also highlighted the effect due to the use of recycled powders when the bulk of the samples has been investigated.

Synthesis and Electrochemical Characterisation of Magnetite Coatings on Ti6Al4V-ELI

Titanium alloys have been widely employed in implant materials owing to their biocompatibility. The primary limitation of these materials is their poor performance in applications involving surfaces in mutual contact and under load or relative motion because of their low wear resistance. The aim of this work is to synthesis magnetite coatings on the Ti6Al4V-ELI alloy surface to increase corrosion resistance and to evaluate its electrochemical behaviour. The coatings were obtained using potentiostatic pulse-assisted coprecipitation (PP-CP) on a Ti6Al4V-ELI substrate. The preliminary X-Ray Diffraction (XRD) results indicate the presence of the magnetite coating with 8–10 nm crystal sizes, determined for the (311) plane. Using X-ray photoelectron spectroscopy (XPS), the presence of the magnetite phase on the titanium alloy was observed. Magnetite coating was homogeneous over the full surface and increased the roughness with respect to the substrate. For the corrosion potential behaviour, the Ti6Al4V-ELI showed a modified Ecorr that was less active from the presence of the magnetite coating, and the impedance values were higher than the reference samples without coating. From the polarization curves, the current density of the sample with magnetite was smaller than of bare titanium.

Insights into the Mixed Oxide Thin Film Cathodes of LiCoO2, LiMn2O4 and TiO2 Deposited from Powder Target

The present work describes the preparation of mixed oxide powder target of LiCoO2, LiMn2O4 and preparation of thin films. Electrochemical investigations have been carried out in the potential range 2.0–4.3 V with respect to Li. There after TiO2 mesoporous (2–50 nm) powder was also added to the above composition and deposited thin films. XRD, XPS and electrochemical characterisation have been carried out for thin film cathodes. The potential window as well as discharge capacity enhanced after TiO2 doping to the mixed oxide target of LiCoO2 and LiMn2O4. Electrochemical characterization have been carried out in potential range 1.4–4.5 V, delivered a discharge capacity of 137 μAh μm−1 cm−2. The deposited cathode thin films will be a good choice as electrodes for high voltage solid state batteries.