Thermogalvanic corrosion of Alloy 31 in different heavy brine LiBr solutions

Thermogalvanic corrosion generated between two electrodes of Alloy 31, a highly-alloyed austenitic stainless steel (UNS N08031), has been investigated imposing different temperature gradients in three deaerated LiBr solutions, under open circuit conditions by using a zero-resistance ammeter (ZRA). Besides EIS spectra were acquired in order to explain the obtained results. On the whole, cold Alloy 31 electrodes were anodic to hot Alloy 31 electrodes, since an increase in temperature favoured the cathodic behaviour of the hot electrode. Thermogalvanic corrosion of Alloy 31 in the LiBr solutions studied was not severe, although it negatively affects the corrosion resistance of the cold anode. The protective properties of the passive film formed on the anode surface were found to improve with thermogalvanic coupling time

Effect of Temperature on Thermogalvanic Coupling of Alloy 31 in Libr Solutions Studied by Means of Imposed Potential Measurements

Corrosion resistance of Alloy 31, a highly alloyed stainless steel (UNS N08031) were studied in heavy brine LiBr solutions (400, 700 and 992 g/l) at different temperatures using electrochemical techniques. The mixed potential theory was used to evaluate thermogalvanic corrosion of Alloy 31 in the studied LiBr solutions. Potentiodynamic curves indicate that high temperatures favoured both cathodic and anodic processes, increasing passive current densities and decreasing the pitting potential. Generally, the cold electrode of the pair was the anode of the thermogalvanic cell

Repassivation of the damage generated by cavitation on UNS N08031 in a LiBr solution by means of electrochemical techniques and Confocal Laser Scanning Microscopy

The objective of this work is to study the influence of cavitation on the corrosion behaviour of Alloy 31, a highly-alloyed austenitic stainless steel (UNS N08031), in a LiBr heavy brine solution (992 g/L) at 25 °C. The presence of cavitation shifted the OCP value towards the active direction by 708 mVAg/AgCl, increased anodic current densities and passivation current density, ip, and reduced the pitting potential, Ep. Repassivation behaviour of Alloy 31 has been investigated by using potentiostatic tests at different potentials. The current density transient obtained after interrupting cavitation was used to obtain the repassivation index, n, provided by the slope of the log i(t) vs. log t representation. The value of n decreased as the applied potential was increased, reaching values near zero for potentials close to the pitting potential. The damage generated during the potentiostatic tests has been quantified by means of Confocal Laser Scanning Microscopy

Facile preparation of electrodes based on WO3 nanostructures modified with C and S used as anode materials for Li-ion batteries

[EN] An appropriate morphological and structure matrix configuration where lithium ions could insert and de-insert is essential for lithium-ion batteries (LiB). Tungsten oxides (WO3) are especially attractive materials for this aim. In this research, the effects of the morphology and composition of WO3 nanostructures on the charge/discharge behavior for Li-ion batteries are methodically examined. On the one hand, nanostructured WO3 thin film was effectively synthesized by an electrochemical procedure. Then, an annealing treatment at 600°C in air environment for 4 h was carried out. In the second electrode synthesized, a carbon layer was uniformly deposited on WO3 nanostructures to obtain a WO3/C electrode. Finally, WO3/WS2 electrodes were prepared by means of in situ sulfurization of WO3 one-step solid-state synthesis using tungsten trioxide (WO3) and thiourea as precursor material. By using X-ray photoelectron spectroscopy, X-ray diffraction analysis, transmission electron microscopy, Raman spectra, and field-emission scanning electron microscopy, the three electrodes have been morphologically characterized. Electrochemical properties were analyzed by cyclic voltammogram, galvanostatic charge/discharge cycling, and electrochemical impedance spectroscopy. Among all the synthesized samples, WO3/C nanostructures reveal the best performance as they exhibit the greatest discharge capacity and cycle performance (820 mA h g¿1).UPV for the concession of a postdoctoral, Grant/Award Number: PAID-10-21; Ministerio de Universidades for the concession of the predoctoral, Grant/Award Number: FPU19/02466; Comunitat Valenciana, Grant/Award Number: IDIFEDER/18/044Roselló-Márquez, G.; García-García, D.; Cifre-Herrando, M.; Blasco-Tamarit, E.; Garcia-Anton, J. (2023). Facile preparation of electrodes based on WO3 nanostructures modified with C and S used as anode materials for Li-ion batteries. Journal of the American Ceramic Society. 106(4):2550-2566. https://doi.org/10.1111/jace.1891025502566106

Should TiO2 nanostructures doped with Li+ be used as photoanodes for photoelectrochemical water splitting applications?

Different TiO2 nanostructures, nanotubes and nanosponges, were obtained by anodization of Ti under stagnant and hydrodynamic conditions. Samples were doped with Li+ before and after annealing at 450 °C during 1 h. The nanostructures were characterized by different microscopy techniques: Field Emission Scanning Electron Microscopy (FE-SEM) and Raman Confocal Laser Microscopy. Additionally, Incident Photon-to-electron Conversion Efficiency (IPCE), photoelectrochemical water splitting and stability measurements were also performed. According to the results, TiO2 nanostructures doped before annealing present the worst photocurrent response, even if compared with undoped samples. On the other hand, this study reveals that Li+-doped TiO2 nanostructures doped after annealing can be used as durable and stable photoanodes for photoelectrochemical water splitting applications

Effects of the area of a duplex stainless steel exposed to corrosion on the cathodic and anodic reactions in a LiBr solution under static and dynamic conditions

[EN] The objective of the work was to study the influence of the exposed area of the working electrode on the corrosion behavior of a duplex stainless steel (EN 1.4462) in a 992 g/l LiBr solution under static conditions (without cavitation) and dynamic conditions (with cavitation) at 25 °C. The Potentiodynamic Cyclic curves obtained were compared and different tendencies were observed. Cavitation increased the cathodic current density when the area exposed to the solution is large (diameters 6 and 8 mm). This behavior was not observed in the tests with smaller electrode areas (diameters 1.6 and 4 mm). © 2011 by ESG.We wish to express our gratitude to Ministerio de Ciencia e Innovación (CTQ2009-07518/PPQ), to FEDER for their financial support and to Dr. M. Asunción Jaime for her translation assistance.García-García, D.; Blasco-Tamarit, E.; Garcia-Anton, J. (2011). Effects of the area of a duplex stainless steel exposed to corrosion on the cathodic and anodic reactions in a LiBr solution under static and dynamic conditions. International Journal of Electrochemical Science. 6(5):1237-1249. http://hdl.handle.net/10251/61155S123712496

TiO2 Nanostructures for Photoelectrocatalytic Degradation of Acetaminophen

Advanced oxidation processes driven by renewable energy sources are gaining attention in degrading organic pollutants in waste waters in an efficient and sustainable way. The present work is focused on a study of TiO2 nanotubes as photocatalysts for photoelectrocatalytic (PEC) degradation of acetaminophen (AMP) at different pH (3, 7, and 9). In particular, different TiO2 photocatalysts were synthetized by stirring the electrode at different Reynolds numbers (Res) during electrochemical anodization. The morphology of the photocatalysts and their crystalline structure were evaluated by field emission scanning electron microscopy (FESEM) and Raman confocal laser microscopy (RCLM). These analyses revealed that anatase TiO2 nanotubes were obtained after anodization. In addition, photocurrent densities versus potential curves were performed in order to characterize the electrochemical properties of the photocatalysts. These results showed that increasing the Re during anodization led to an enhancement in the obtained photocurrents, since under hydrodynamic conditions part of the initiation layer formed over the tubes was removed. PEC degradation of acetaminophen was followed by ultraviolet-visible absorbance measurements and chemical oxygen demand tests. As drug mineralization was the most important issue, total organic carbon measurements were also carried out. The statistical significance analysis established that acetaminophen PEC degradation improved as hydrodynamic conditions linearly increased in the studied range (Re from 0 to 600). Additionally, acetaminophen conversion had a quadratic behavior with respect to the reaction pH, where the maximum conversion value was reached at pH 3. However, in this case, the diversity of the byproducts increased due to a different PEC degradation mechanism

Characterization and Comparison of WO3/WO3-MoO3 and TiO2/TiO2-ZnO Nanostructures for Photoelectrocatalytic Degradation of the Pesticide Imazalil

[EN] Tungsten oxide (WO3) and zinc oxide (ZnO) are n-type semiconductors with numerous applications in photocatalysis. The objective of this study was to synthesize and characterize different types of nanostructures (WO3, WO3-Mo, TiO2, and TiO2-ZnO) for a comparison of hybrid and pure nanostructures to use them as a photoanodes for photoelectrocatalytic degradation of emerging contaminants. With the aim of comparing the properties of both samples, field emission scanning electron microscopy (FE-SEM) and confocal laser-Raman spectroscopy were used to study the morphology, composition, and crystallinity, respectively. Electrochemical impedances, Mott-Schottky, and water splitting measurements were performed to compare the photoelectrochemical properties of photoanodes. Finally, the photoelectrocatalytic degradation of the pesticide Imazalil was carried out with the best optimized nanostructure (TiO2-ZnO).This research was funded by AEI (PID2019-105844RB-I00/AEI/10.13039/501100011033) and the project co-funded by FEDER operational program 2014¿2020 of Comunitat Valenciana (IDIFEDER/18/044). M.C.-H. received financial support from Ministerio de Universidades of the predoctoral grant (FPU19/02466). G.R.-M. received financial support from the UPV of a post-doctoral grant (PAID-10-21). P.J.N.-G. received support thanks the grant PEJ2018-003596-A-AR funded by MCIN/AEI/10.13039/501100011033. Finally, project co-funded by FEDER operational programme 2014-2020 of Comunitat Valenciana (IDIFEDER/18/044) is acknowledged.Cifre-Herrando, M.; Roselló-Márquez, G.; Navarro Gázquez, PJ.; Muñoz-Portero, M.; Blasco-Tamarit, E.; Garcia-Anton, J. (2023). Characterization and Comparison of WO3/WO3-MoO3 and TiO2/TiO2-ZnO Nanostructures for Photoelectrocatalytic Degradation of the Pesticide Imazalil. Nanomaterials. 13(18). https://doi.org/10.3390/nano13182584131

Original Approach to Synthesize TiO2/ZnO Hybrid nanosponges used as photoanodes for photoelectrochemical applications

[EN] In the present work, TiO2/ZnO hybrid nanosponges have been synthesized for the first time. First, TiO2 nanosponges were obtained by anodization under hydrodynamic conditions in a glycerol/water/NH4F electrolyte. Next, in order to achieve the anatase phase of TiO2 and improve its photocatalytic behaviour, the samples were annealed at 450 degrees C for 1 h. Once the TiO2 nanosponges were synthesized, TiO2/ZnO hybrid nanosponges were obtained by electrodeposition of ZnO on TiO2 nanosponges using different temperatures, times, and concentrations of zinc nitrate (Zn(NO3)(2)). TiO2/ZnO hybrid nanosponges were used as photoanodes in photoelectrochemical water splitting tests. The results indicate that the photoelectrochemical response improves, in the studied range, by increasing the temperature and the Zn(NO3)(2) concentration during the electrodeposition process, obtaining an increase in the photoelectrochemical response of 141% for the TiO2/ZnO hybrid nanosponges electrodeposited at 75 degrees C with 10 mM Zn(NO3)(2) for 15 min. Furthermore, morphological, chemical, and structural characterization was performed by Field Emission Scanning Electron Microscopy (FE-SEM) with Energy Dispersive X-Ray spectroscopy (EDX), Raman Confocal Laser Spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), and Grazing Incidence X-Ray Diffraction (GIXRD).The authors would like to express their gratitude for the financial support of the ¿Agencia Estatal de Investigación (PID2019-105844RB-I00/MCIN/AEI/10.13039/501100011033)¿, for the co-finance by the European Social Fund, and for its help in the ¿Laser Raman Microscope acquisition (UPOV08-3E-012) ¿. Pedro José Navarro Gázquez also thanks the Grant PEJ2018-003596-A-AR funded by MCIN/AEI/10.13039/501100011033 and by ¿ESF Investing in your future¿.Navarro-Gázquez, PJ.; Muñoz-Portero, M.; Blasco-Tamarit, E.; Sánchez-Tovar, R.; Fernández-Domene, RM.; Garcia-Anton, J. (2021). Original Approach to Synthesize TiO2/ZnO Hybrid nanosponges used as photoanodes for photoelectrochemical applications. Materials. 14(21):1-21. https://doi.org/10.3390/ma14216441S121142

Study of the effect of temperature on the galvanic corrosion between Alloy 31 base metal and its weld in polluted phosphoric acid

This work studies the influence of the solution temperature on the corrosion resistance of a high alloyed austenitic stainless steel (UNS N08031) used as Base Metal (BM), the Heat Affected Zone (HAZ) and the Weld Metal (WM) obtained by the Gas Tungsten Arc Welding technique using a Nickel-base alloy (UNS N06059) as filler metal (GTAW). Electrochemical tests were carried out in a 5.5 M polluted phosphoric acid solution with 0.03 wt% (380 ppm) of chloride ions and 2 wt% of H2SO4 at 25, 40, 60 and 80 degrees C. The potentiodynamic curves of the materials were registered in each condition under study and electrochemical parameters such as E-corr, i(corr), E-b and i(p) were obtained. The galvanic corrosion generated between the BM-HAZ and HAZ-WM pairs was also analysed by means of the Mixed Potential Theory. The lower E-b and (E-b-E-corr) values and higher ip values obtained at higher temperatures indicate that the properties of the passive film formed degraded with temperature. The welding process modifies the characteristics of the passive film, deteriorating them and favouring the loss of passivity of the WM with respect to the BM, as shown by the lowest E-b values and highest i(p) values of the WM.Blasco-Tamarit, E.; García-García, D.; Garcia-Anton, J.; Guenbour, A. (2011). Study of the effect of temperature on the galvanic corrosion between Alloy 31 base metal and its weld in polluted phosphoric acid. International Journal of Electrochemical Science. 6(12):6244-6260. http://hdl.handle.net/10251/61160S6244626061