Carlos M. Sánchez-Sánchez

Electrochemical approaches to alleviation of the problem of carbon dioxide accumulation

The electrochemical reduction of CO2, which includes a number of different specific approaches, may show promise as a means to help slow down the accumulation of this greenhouse gas in the atmosphere. Two types of approaches are examined briefly here. First, CO2 can be used as a reagent in the electrocarboxylation reaction to produce organic carboxylic acids, for example, the pharmaceutical ibuprofen. Second, CO2 can be converted to a fuel, either directly or via synthesis gas. The latter can be produced with reasonably good energy efficiency in a gas-diffusion, electrode-based cell even at present with existing electrocatalysts. Oxygen gas is produced as a by-product. Further work is needed to improve the selectivity and efficiency in this and other approaches.

Mineral Iron Oxides as Iron Source in Electro-Fenton and Photoelectro-Fenton Mineralization Processes

Several low-soluble mineral iron oxides have been studied as an iron source for the production of hydroxyl radicals via H 2 O 2 decomposition in the presence of ferrous ions (Fentons reaction). In particular, this study focuses on electro-Fenton and photoelectro-Fenton processes, using aniline as a model pollutant. The aim of this work is to spread the use of iron minerals as catalyst in the different electrochemical wastewater treatments. Among all the iron oxides tested, magnetite (Fe 3 O 4 ) and wustite (FeO) show the more promising results. The main advantages of these minerals are that they produce lower concentrations of iron in solution, ease of recycling the iron catalyst, and their ability to self-regulate the concentration of iron ions in solution. Wustite and magnetite behave purely as a source of iron ions in the electro-Fenton process. But, magnetite exhibits a heterogeneous photocatalytic effect when used as an iron source in the photoelectro-Fenton process. This new magnetite-photoelectro-Fenton process significantly improves the pollutant removal yield (16.7% more after 5 h of mineralization) compared to the conventional photoelectro-Fenton process. This effect is observed for two different wavelengths in the UV range, 254 and 360 nm.

Electrochemical synthesis of 3-phenylcinnamonitrile by reduction of benzophenone in acetonitrile

Abstract The electrochemical cyanomethylation of benzophenone in acetonitrile was investigated as an interesting way of synthesizing high yield of 3-phenylcinnamonitrile (55% for 50% of theoretical circulated charge). This synthetic method uses the benzophenone radical-anion as a strong electrogenerated base to abstract a proton from the solvent and obtain the nucleophile − CH 2 CN. This anion is capable of yielding cyanomethylated products very easily. In our case the reaction of this anion with benzophenone yields 3-phenylcinnamonitrile in a father–son like mechanism.

Electrosynthesis of L-Cysteine on a Dispersed Pb/Carbon Black Electrode

The electrosynthesis of L-cysteine (RSH) in aqueous medium has been investigated using Pb particles dispersed on carbon as a cathode for L-cystine electroreduction. Pb particles were synthesized in a water-in-oil microemulsion and later dispersed on carbon Vulcan XC-72. The electrochemical characterization of the Pb/C catalyst was carried out by cyclic voltammetry and scanning electrochemical microscopy (SECM). In particular, an approach of the substrate generation/tip collection mode of the SECM has been used for imaging the RSH generation. Different 20 wt % Pb/C-supported cathodes have been fabricated and morphologically characterized. These cathodes were tested for RSH electrosynthesis and compared with a conventional bulk Pb cathode. After a 100% theoretical charge, our three-dimensional 20 wt % Pb/C cathode exhibits a 30% higher RSH yield and current efficiency than the other cathodes. This performance improvement is related to the increase in the available geometric area of this electrode. We demonstrate the feasibility of using Pb/C particles as a catalyst in a type of cathode for RSH electrosynthesis. Moreover, our Pb/C electrodes show a broad scope because they can be applied to other electrosyntheses of valuable organic compounds where bulk Pb is the conventional cathode at present.

Influence of Pb2+ ions in the H2 oxidation on Pt catalyzed hydrogen diffusion anodes in sulfuric acid: presence of oscillatory phenomena

The influence of Pb2+ ions in sulfuric acid medium on the behavior of a platinum catalyzed hydrogen diffusion electrode (HDE) in a filter press reactor has been studied. A voltammetric study of the H2 oxidation reaction on a polyoriented platinum electrode and a platinum rotating disk electrode (RDE) in presence of lead ions in solution has also been carried out. Potential oscillations were found in galvanostatic experiments of H2 oxidation using a HDE catalyzed with platinum when Pb2+ ions are present in solution. This oscillatory phenomenon was also observed when hydrogen oxidation was carried out in presence of Pb2+ ions using a platinum RDE. The oscillatory behavior observed has been attributed to an adsorption–oxidation–desorption process of lead on the platinum surface. Due to the low solubility of Pb2+ in sulfuric acid, at high values of coverage, lead is oxidised to insoluble lead sulfate that blocks the Pt surface. The coupling of the dissolution of lead sulfate and the Pb electrochemical adsorption–oxidation processes cause the oscillatory phenomenon.