Electroanalytical properties of metal–oxide electrodes formed by plasma electrolytic oxidation

Plasma Electrolytic Oxidation of Titanium in Ni and Cu Hydroxide Suspensions towards Preparation of Electrocatalysts for Urea Oxidation

The increasing climate crisis requires an improvement in renewable energy technologies. One of them are fuel cells, devices that are capable of generating electricity directly from the chemical reaction that is taking place inside of them. Despite the advantages of these solutions, a lack of the appropriate materials is holding them back from commercialization. This research shows preliminary results from a simple way to prepare black TiO₂ coatings, doped with Cu or Ni using the plasma electrolytic oxidation process, which can be used as anodes in urea-fueled fuel cells. They show activity toward urea oxidation, with a maximum current density of 130 μA cm^-2 (@1 V vs. Hg|HgO) observed for Cu-enhanced TiO₂ and low potential of only 0.742 V (Vs Hg|HgO) required for 50 μA cm^-2 for Ni-enhanced TiO₂. These results demonstrate how the PEO process can be used for the preparation of TiO₂-based doped materials with electrocatalytic properties toward urea electrooxidation.

Corrosion and Wear Behavior of TiO2/TiN Duplex Coatings on Titanium by Plasma Electrolytic Oxidation and Gas Nitriding

In this study, corrosion and wear behavior of three kinds of coatings by two processes, namely, plasma electrolytic oxidation (PEO) coatings (Ti/TiO₂), gas nitriding coating (Ti/TiN), and the duplex coating (Ti/TiO₂-N) by combination of PEO and gas nitriding methods were systematically investigated. X-ray diffraction tests, field-emission scanning electron microscopy, and adhesion tests are employed for the coating characterization, along with the wear and electrochemical test for evaluating the corrosion and tribological properties. The morphology and structure of the coating consist of micro-cavities known as the pancake structure on the surface. The electrolytic plasma oxidation process produces a typical annealing behavior with a low friction coefficient based on the wear test. The coating consists of nitride and nitrate/oxides titanium for nitrided samples. The surface morphology of nitrided oxide titanium coating shows a slight change in the size of the crystals and the diameter of the cavities due to the influence of nitrogen in the titanium oxide coating. The tribological behavior of the coatings showed that the wear resistance of the duplex coating (Ti/TiO₂-N) and Ti/TiO₂ coatings is significantly higher compared to Ti/TiN coatings and uncoated Ti samples. The polarization resistance of the Ti/TiO₂-N and Ti/TiO₂ coatings was 632.2 and 1451.9 kΩ cm², respectively. These values are considerably greater than that of the uncoated Ti (135.9 kΩ cm²). Likewise, impedance showed that the Ti/TiO₂-N and Ti/TiO₂ coatings demonstrate higher charge transfer resistance than that of other samples due to better insulating behavior and denser structure.