Synthesis of high-area chemically modified electrodes using microwave heating

New MMO coatings for electro-refinery applications: Promoting the production of carboxylates

Within the new circular economy paradigm, this work evaluates the performance of tailored mixed metal oxides (MMO) anodes, based on ruthenium and antimony, for their application into an electrochemically-assisted organic refinery process. This process is designed to transform pollutants into value-added products with minimal mineralization. Oxidation of synthetic wastes consisting of phenol solutions was used to validate the electrochemical conversion of phenolic wastes into carboxylates, which are then considered as bricks to be used for electrosynthesis or to produce fuels. The MMO anodes were manufactured using two synthesis routes (Pechini method and ionic liquid method), each followed by one of three different heating treatments: furnace, microwave, and CO2 laser. The selection of the optimal electrode for the organic electrorefinery was based on a combination of physical and electrochemical properties, degradation performance of phenol to carboxylates, and long-term stability, looking for a truly sustainable solution. Results indicate that anodes synthesized by the ionic liquid (IL) method, regardless of the heating treatment, demonstrated superior performance, with larger active areas (with furnace 82 mC cm-2, microwave 97 mC cm-2, and laser 127 mC cm-2) and higher phenol degradation rates, resulting in a greater generation of carboxylates during electrolysis, yielding primarily oxalate and achieving up to 40% conversion with furnace heating. However, laser-treated anodes exhibited greater stability than furnace-made ones, attributed to the formation of an insulating TiO2 layer. Although the electrode with the longest service life did not show the best catalytic properties for minimizing mineralization, the observed variations in coatings with identical chemical compositions highlight the importance of this research. This study positions itself at the forefront of developing more efficient and sustainable electrochemical technologies for organic waste treatment.

Dipropyl ammonium ionic liquids to prepare Ti/RuO2-Sb2O4 anodes at different calcination temperatures

The development of technologies capable of producing efficient and economically viable anodes is essential for the electrochemical treatment of water contaminated with complex organic pollutants. In this context, the use of ionic liquids as solvents to prepare mixed metal oxide (MMO) anodes has proven to be an up-and-coming alternative. Here, we analyze the influence of the temperature of calcination (300, 350, and 400 ºC) on the production of Ti(RuO2)0.8-(Sb2O4)0.2 anodes made using the thermal decomposition method using three ionic liquids (IL) as solvents: dipropyl ammonium acetate (DPA-Ac), dipropyl ammonium propionate (DPA-Pr), and dipropyl ammonium butyrate (DPA-Bu). The decomposition temperature for all IL, accessed by thermogravimetry, is below 200 ºC. Physical and electrochemical analyses demonstrate that the calcination temperature of the anodes is decisive for their durability and electrochemical properties. Anodes prepared with DPA-Bu at 350 ºC show higher stability (around 35 h) than those made with other ILs at temperatures of 300 and 400 ºC and improved results in terms of 4-NP mineralization, where 97% of TOC removal was achieved in 120 min. It could be verified that the calcination temperature and IL employed had a decisive influence on the characteristics of the presented anodes. Therefore, the anode prepared with DPA-Bu at 350 ºC is promising for application in the degradation of organic compounds.