Ni-Doped Titanium Dioxide Films Obtained by Plasma Electrolytic Oxidation in Refrigerated Electrolytes

Enhancing Photocatalytic Properties of TiO2 Photocatalyst and Heterojunctions: A Comprehensive Review of the Impact of Biphasic Systems in Aerogels and Xerogels Synthesis, Methods, and Mechanisms for Environmental Applications

This review provides a detailed exploration of titanium dioxide (TiO2) photocatalysts, emphasizing structural phases, heterophase junctions, and their impact on efficiency. Key points include diverse synthesis methods, with a focus on the sol-gel route and variants like low-temperature hydrothermal synthesis (LTHT). The review delves into the influence of acid-base donors on gelation, dissects crucial drying techniques for TiO2 aerogel or xerogel catalysts, and meticulously examines mechanisms underlying photocatalytic activity. It highlights the role of physicochemical properties in charge diffusion, carrier recombination, and the impact of scavengers in photo-oxidation/reduction. Additionally, TiO2 doping techniques and heterostructures and their potential for enhancing efficiency are briefly discussed, all within the context of environmental applications.

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.

Efficiency and Energy Demand in Polishing Treatment of Wastewater Treatment Plants Effluents: Photoelectrocatalysis vs. Photocatalysis and Photolysis

Photoelectrocatalysis (PEC), photolysis (PL), and photocatalysis (PC) were applied to increase the biodegradability of wastewaters effluents sampled from a plant collecting both municipal wastewaters and aqueous waste. In PEC, the catalyst was a porous TiO2 photoanode obtained by plasma electrolytic oxidation and electrically polarized during operation. In PC a dispersion of TiO2 powders was used. The same irradiation shielding, and similar catalyst surface areas were set for PC and PEC, allowing a straightforward evaluation of the catalytic effect of the electrical polarization of TiO2 during operation. Results showed that the chemical oxygen demand (COD) and color removal rates follow the order: PEC > PL and PEC > PC. The specific biodegradability rate (SBR) increased following the same order, the PEC process allowing SBR values more than twice higher than PL and PC. The operating costs were calculated based on the electrical energy per order of COD, color, and SBR values, demonstrating that at the laboratory scale the energy demand of PEC is significantly lower than the other two tested processes.

Synthesis and Characterization of Enhanced Photocatalytic Activity with Li+-Doping Nanosized TiO2 Catalyst

The photocatalytic efficiency of TiO₂ is reduced by rapid electron-hole recombination. An effective approach to address this limitation is to have TiO₂ doped with various metal ions or heteroatoms. Herein, we prepared a series of Li⁺-doped TiO₂ nanoparticles showing high photocatalytic activities through the sol-gel method. The samples were characterized by X-ray diffraction (XRD) and surface area analyses. Effects of Li⁺ doping on the Brunauer-Emmett-Teller (BET) surface area, crystallite size, phase transformation temperature, and phase composition were studied. The results showed that Li⁺ doping can promote the generation of the rutile crystal phase in TiO₂, lower the anatase-to-rutile transformation temperature, and generate the mixed-crystal effect. The photocatalytic degradation of methyl orange (MO) was used as a probe reaction to evaluate the photoactivity of the nanoparticles. Parameters affecting the photocatalytic efficiency, including the Li⁺ doping amount, calcination temperature, and catalyst amount, as well as the kinetics of the photocatalytic process toward the degradation of MO, were investigated. The mixed-crystal TiO₂, which was doped with 1.0 mol % Li⁺ and calcined at 550 °C containing 27.1% rutile and 72.9% anatase phase, showed a 2.2-fold increase in the photoactivity on the basis of the rate constant of MO decomposition as compared with the undoped TiO₂. The existence of a definite quantity of rutile phase could effectively inhibit the recombination of the electron-hole pairs, thus promoting photocatalytic activity.