Alejandro Alatorre-Ordaz

Efficient degradation of selected polluting dyes using the tetrahydroxoargentate ion, Ag(OH)4−, in alkaline media

The use of soluble and highly oxidizing Ag(III) in the form of the tetrahydroxoargentate ion Ag(OH)4- is reported for the oxidation of surrogate organic recalcitrant dyes (i.e., rhodamine 6G (Rh6G) and fluorescein (Fl)). The possible use of Ag(OH)4- for the treatment of these and other refractory compounds is assessed. Such dyes were selected due to their common occurrence, stability, refractory nature, the relatively high toxicity of Rh6G, and their structural similarity to Fl. Several reaction intermediates/products were identified. The results showed that the highly oxidizing tetrahydroxoargentate anion was capable of degrading these recalcitrant dyes. Furthermore, the final degradation products do not represent a higher environmental risk than the original surrogates themselves. In addition, the partial mineralization of the dyes was proven.

Photovoltaic study of quantum dot-sensitized TiO2/CdS/ZnS solar cell with P3HT or P3OT added

Within the body of research aimed at improving the photovoltaic performance of quantum dot-sensitized solar cells (QDSSC), poly-3-alkyl thiophenes have been commonly used in hybrid photovoltaic devices. The roles of poly(3-hexylthiophene) (P3HT) and of poly(3-octylthiophene) (P3OT) on hybrid QDSSC were investigated in the present work. To this end, CdS and ZnS QDs were deposited by successive ionic layer adsorption and reaction method on TiO2 mesoporous film. The polymers were added by drop-casting method giving the configurations TiO2/CdS/ZnS/P3HT and TiO2/CdS/ZnS/P3OT. Results showed that the polymer covers the TiO2/CdS/ZnS surface enough to protect it from contact with the polysulfide electrolyte, while electrochemical impedance spectroscopy measurements indicated that when P3HT and P3OT were employed, the recombination resistance increased and the transport resistance decreased, causing the improvement of the open circuit voltage and fill factor, respectively.Graphical Abstract

Oxidation of the borohydride Ion at silver nanoparticles on a glassy carbon electrode (GCE) using pulsed potential techniques

Direct oxidation borohydride fuel cells are very attractive energy conversion devices. Silver has been reported as one of the few materials which can catalyze an 8-electron oxidation. Potential step amperometric pulse techniques to synthesize nanostructured silver material on flat glassy carbon electrodes is reported and significant differences with bulk silver deposit have been observed. The oxidation of borohydride ion on the silver particles occurs at -0.025 V vs. SCE and the potential decreases towards negative values at longer cycle times. The oxidation current also decreases with the number of cycles, suggesting that the silver active sites become partially blocked by oxidation products of borohydride. The electroactive area per unit electrode area of silver was relatively low for particles deposited using potential step amperometric techniques on glassy carbon (0.002 cm2 per cm-2) compared with the area found at a polycrystalline silver electrode (0.103 cm2 per cm-2)

Experimental Analysis of PEM Fuel Cells With Biomimetical Mixed Flows as Gas Distributors

A proton exchange membrane fuel cell (PEMFC) is an electrochemical device that converts the chemical energy from the gases into electrical energy. The PEMFCs consist of many parts, and the current collector plate is one of the key components among them. Channels in the bipolar plate distribute air on the cathode side and hydrogen on the anode side. Theoretically a fuel cell produces more current as more fuel is supplied. However the way in which the gases are supplied affects dramatically the performance of the cell. The present paper shows how the mixed flows improve the current density produced by fuel cells. Polarization and power density curves are presented. The results suggest that a flow with two levels of bifurcations is preferred for the anode side. This behavior is expected due to the similitude with the performance of the natural world in which geometries with this type of bifurcations transport the nutrients inside the tree leaves and plants.Copyright

Degradation of pentachlorophenol as a model hazardous and recalcitrant organochlorinated pollutant using AgIII

Environmental context Electrochemistry offers potential applications for environmental remediation. Pentachlorophenol, a highly toxic and recalcitrant halogenated compound, is degraded by a novel oxidant produced electrochemically, and the intermediates and products of the degradation are investigated. Cyclic remediation systems merit further study. Abstract The use of electrochemically generated Ag(OH)4− as a strong oxidising agent was evaluated for the treatment of a model hazardous and recalcitrant organochlorinated pollutant, pentachlorophenol (PCP). High-performance liquid chromatography (HPLC), gas chromatography with flame ionisation detection (GC-FID) or with electron capture detection (GC-ECD), gas chromatography with mass spectrometry detection and UV-visible spectroscopy were utilised to investigate intermediates and products generated during such treatment. From these, it was deduced that dechlorination occurred first, followed by an oxidative ring opening at the C=C bond that destabilised the remaining structure and generated tetrachloro-p-benzoquinone, 2,3,5,6-tetrachlorophenol, 2,3,4,6-tetrachlorophenol, 2,4,6-trichlorophenol (or 2,3,5-trichlorophenol), 2,4,5-trichlorophenol (or 2,3,6-trichlorophenol) and 2,4-dichlorophenol (or 3,4-dichlorophenol). In contrast to other remediation methods (e.g. incineration) no highly toxic molecules such as dioxins were generated by this novel degradation system.

Numerical and Experimental Study of Lead-Acid Battery

Lead-Acid battery was the earliest secondary battery to be developed. It is the battery that is most widely used in applications ranging from automotive to industrial storage. Nowadays it is often used to store energy from renewable energy sources. There is a growing interest to continue using Lead-Acid batteries in the energy systems due to the recyclability and the manufacturing infrastructure which is already in place. Due to this rising interest, there is also a need to improve the efficiency and extend the life cycle of Lead-Acid batteries. To achieve these objectives, it is necessary to gain a better understanding of the physics taking place within individual batteries. A physics based computational model can be used to simulate the mechanisms of the battery accurately and describe all the processes that are happening inside; including the interactions between the battery elements, based upon the physical processes that the model takes into account.In the present paper, we present a discharge/charge experimental study that has been carried out with small Lead-Acid batteries (with a capacity of 7 Ah). The experiments were performed with a constant current rate of 0.1C [A]1 for two different battery arrangements.An in-house zero dimensional model was developed to perform simulations of Lead-Acid batteries under different operating conditions. A validation analysis of the model was executed to confirm the accuracy of the results obtained by the model compared to the aforementioned experiments. Additional simulations of the battery were carried out under different current rates and geometry modifications in order to study how the performance of the battery may change under these conditions.Copyright

Electrochemical Study of Co(II)/Co(III) on Different Electrode Materials for Energy Storage in Redox Flow Cells

The development of redox flow cells has been carried out through the use of several redox couples which oxidize and reduce to store electrical energy. Some problems encountered in redox cells include: low solubility of redox couples, slow kinetics, low stability of electrode materials and high toxicity of electroactive species. In this paper, Co(III)/Co(II) has been investigated as a possible electroactive material because of its high oxidizing power and the relatively low toxicity of Co(III). The electrochemical study of Co(III)/Co(II) was carried out on different electrode materials such as glassy carbon, Au, Pt, Pb and stainless steel. Results show that the high oxidizing power of Co(III) does not enable to observe its reduction reaction in the aforementioned electrode materials possibly due to electrode surface corrosion and/or water oxidation. However, the electrolysis of Co(III) with a Pb electrode shows that the system is reversible and forms PbO2 on the electrode surface