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One of the important environmental challenges of the 21st century is the effective removal of pollutants from the aquatic environment. In this study, electrodeposited manganese oxides (MnyOx) films were applied as visible-light-driven photocatalyst for the removal and mineralization of Tetracycline (TC) antibiotics. The photocatalytic activity of as-deposited and annealed MnyOx was tested at different pH values using LED visible illumination, resulting in 92.4 % of TC mineralization efficiency after 180 min for the best performing manganese oxide. Quenching experiments showed that hydroxyl radicals (radical dotOH) are the main active species responsible for the TC degradation. The photocorrosion of MnyOx has been studied by quantifying the concentration of the dissolved manganese cations during the photocatalytic experiments. By comparing the catalyst mass loss with the % of TC mineralization, we revealed that the degradation of the oxide surface structure is the factor that, more than the photocorrosion, is limiting the photocatalytic activity of MnyOx films. Finally, the photocatalytic mechanism of TC mineralization is proposed based on the detection of the intermediates species of the mineralization process by High-Performance Liquid Chromatography Mass-Spectroscopy. The facile synthesis process and the superior mineralization rate can open up a new approach for the possible large-scale utilization of electrodeposited MnyOx films as an effective visible light photocatalyst.

Synthesizing efficient heterogeneous catalysts with multiple active sites able to activate peroxymonosulfate (PMS) for the degradation of persistent organic pollutants continues to be a challenge for societies worldwide. In response, cost-effective, eco-friendly oxidized Ni-rich and Co-rich CoNi micro-nanostructured films were fabricated following a two-step process based on simple electrodeposition using green deep eutectic solvent as an electrochemical media and thermal annealing. The CoNi-based catalysts demonstrated exceptional efficiency in the heterogeneous catalyzed activation of PMS for tetracycline degradation and mineralization. The effects of the catalysts’ chemical nature and morphology, the pH, the concentration of PMS, irradiation with visible light, and the duration of contact with the catalysts on the degradation and mineralization of tetracycline were also studied. In dark conditions, oxidized Co-rich CoNi degraded more than 99% of tetracyclines in only 30 min and mineralized more than 99% of them in only 60 min. Moreover, the degradation kinetics doubled from 0.173 min−1 in dark conditions to 0.388 min−1 under visible light irradiation. In addition, the material demonstrated excellent reusability and can be easily recovered with simple heat treatment. Given those findings, our work provides new strategies for constructing high-efficiency and cost-effective PMS catalysts and elucidating the effects of operational parameters and primary reactive species formed by the catalyst–PMS system on water treatment technologies.

Complex tunable visible-light-driven Aurivillius-phase-based micro- and nanostructured photocatalysts were fabricated following a novel, scalable, easily implemented sequential process based on electrochemical deposition and thermal treatment. Regarding its novelty, electrochemistry was the primary tool for synthesis, one that constitutes a viable alternative to other complex chemical and physical processes. The parameters of electrodeposition and thermal conditions promoted different nanostructured Bi2MoO6 and Bi2MoO6@Bi2MoO6-x films. The nanostructured homojunction Bi2MoO6@Bi2MoO6-x films obtained after 3 h of calcination showing micro- and nanowire morphology emerged as the most effective photocatalyst for degrading and mineralizing the mono- and multiantibiotic solutions (i.e., tetracycline, ciprofloxacin, and/or levofloxacin), which achieved near-total degradation and exceptionally high mineralization values (>95%) after 180 min of radiation. The materials' proven reusability, low photocorrosion activity, and excellent photocatalytic performance in mineralizing antibiotics can support the implementation of Bi2MoO6@Bi2MoO6-x homojunctions as efficient visible-light photocatalysts under solar radiation.

Mn3O4 and Mn2O3 were synthesized by potentiostatic electrodeposition from a de-aerated manganese acetate and sodium sulfate electrolytic bath, followed by annealing. The electrodeposition parameters (including applied potential, precursor concentration, pH, temperature) and the thermal treatment conditions were investigated to obtain the best control over microstructure and stoichiometry of manganese oxides. We found that the applied voltage is the key parameter affecting the valence state of initial amorphous manganese while the thermal treatment leads to crystallization and tuning of optical properties without substantially changing the morphology. The as-electrodeposited manganese oxides are X-rays amorphous, while two different crystalline phases, Mn3O4 and Mn2O3, were obtained after the thermal treatment depending on the applied voltage. Through the analysis of TEM cross section images, a fiber-like growth was observed for Mn3O4, while Mn2O3 presented a less porous-more compact microstructure. The optical properties were investigated, resulting in an enhancement in the charge separation properties of the thermally treated manganese oxides, reflected by nearly a 40 % reduction in the photoluminescence peak intensity. We believe that these finding will be useful in the future development of environmental friendly manganese oxide-based photoelectrochemical systems.

Building a sustainable future requires new, accessible, economic, and ecological methods of preparing nanostructured materials used in biomedical and environmental applications. In this work, a detailed study on the electrodeposition process of CoNi in a biocompatible deep eutectic solvent (DES) is presented. Alloy plating performed in choline chloride within a urea-based DES allowed us to tailor elemental compositions, morphologies, and size of the deposits based on the plating conditions. Homogeneous, continuous, and needle-shaped deposits were characterized using electrochemical methods and ex-situ characterization techniques. Although the process's electrochemical behavior corresponded to that of normal deposition, applying the most negative potentials produced a co-reduction of the solvent, which favored the incorporation of oxygen species into the deposit. Given the materials' nature, morphology, and composition tailored to the high active surface, the materials were tested as platforms to activate the formation of sulfate radicals from the peroxomonosulfate salt. Results related to the proposed material and preparation method were promising, as, confirmed by the high effectiveness in degrading the antibiotic tetracycline. Altogether, the work showcases a versatile, environmentally friendly route for electrodepositing CoNi in DESs to yield a proactive tool for developing of platforms with catalytic potential.