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Electrochemical cells based on acid salts (CsH2PO4) have attracted great interest for intermediate temperature, due to the outstanding proton conductivity of acid salts. In this work, electrodes and electrolyte were optimized following different strategies. An epoxy resin was added to the CsH2PO4 material to enhance the mechanical properties of the electrolyte, achieving good con-ductivity, enhanced stability, and cyclability. The electrodes configuration was modified, and Ni sponge was selected as active support. The infiltration of different oxide nanoparticles was carried out to tailor the electrodes resistance by promoting the electrocatalyst activity of electrodes. The selection of a cell supported on the electrode and the addition of an epoxy resin enables the reduction of the electrolyte thickness without damaging the mechanical stability of the thinner electrolyte. ; Funding fromSpanish Government (MINECO ENE2014-57651 grant) is kindly acknowledged

A robust LSM-GDC composite was used as a backbone electrode for the infiltration of different catalysts, dispersed as oxide nanoparticles after firing. Catalyst candidates were screened using symmetric cells supported on the GDC electrolyte. Among the tested catalysts, praseodymium infiltration exhibited an outstanding and highly stable promotion effect of the oxygen reduction reaction. Impedance spectroscopy modelling provided insight into the nature of the distinct mechanisms limiting the cathode performance. The Pr-promotion in cathodes resulted in a fivefold rise in the power density peak when tested on a fully assembled anode-supported fuel cell. ; This work was financially supported by Spanish Government; ENE2011-24761 and SEV-2012-0267. Electron Microscopy Service of the UPV is also acknowledged and anode supported cells were kindly supplied by Forschungszentrum Julich. ; Navarrete Algaba, L.; Solis Díaz, C.; Serra Alfaro, JM. (2015). Boosting the oxygen reduction reaction mechanisms in IT-SOFC cathodes by catalytic functionalization. Journal of Materials Chemistry A. 3(32):16440-16444. https://doi.org/10.1039/C5TA05187H ; S ; 16440 ; 16444 ; 3 ; 32

[EN] The mixed ionic-electronic conductor La2NiO4+delta was investigated as potential cathode material for protonic conducting solid oxide fuel cells (PC-SOFCs) based on La5.5WO11.25-delta electrolyte. Firstly the chemical compatibility between cathode and electrolyte phases (La2NiO4+delta and La5.5WO11.25-delta respectively) was studied. Then, the electrochemical properties of this cathode were improved by partially substituting La and/or Ni, specifically La1.5Pr0.5NiO4+delta and La(1.5)Pro(0.5)Nio(0.8)Co(0.2)O(4+delta) were considered. These two doped materials showed improved electrical conductivity and reduced polarization resistance, when tested as cathode in symmetrical cells. In a second step, the microstructure of La(1.5)Pro(0.5)Nio(0.8)Co(0.2)O(4+delta) was optimized by varying the firing temperature of the cathode. The performance of these mixed conductors is limited by medium frequencies associated processes while they show lower polarization resistances (Rp) than conventional composites based on La5.5WO11.25-delta and pure electronic conductors. La(1.5)Pro(0.5)Nio(0.8)Co(0.2)O(4+delta) cathode sintered at 1050 degrees C exhibits the best electrochemical performance on a La5.5WO11.25-delta-based PC-SOFC, achieving Rp = 0.62 Omega cm(2) at 750 degrees C in wet air. ; Funding from European Union (FP7 Project EFFIPRO - Grant agreement 227560), the Spanish Government (ENE2011-24761, SEV-2012-0267, BES-2012-053180 and CSIC Intramural 200880I093 grants) is kindly acknowledged. The authors thank M. Fabuel for sample preparation. ; Solis Díaz, C.; Navarrete Algaba, L.; Serra Alfaro, JM. (2013). Study of Pr and Pr and Co doped La2NiO4+δ as cathodes for La5.5WO11.25-δ based protonic conducting fuel cells. Journal of Power Sources. 240:691-697. https://doi.org/10.1016/j.jpowsour.2013.05.055 ; S ; 691 ; 697 ; 240

[EN] New composite cathodes for proton conducting solid oxide fuel cells (PC-SOFCs) based on the novel La5.5WO12-delta (LWO) electrolyte have been developed. First the applicability of LWO as a protonic electrolyte has been proved by recording the OCV in a Pt/LWO/Pt cell as a function of the temperature, matching the expected Nernst voltage. In order to improve the electrode performance on LWO PC-SOFCs, composite cathodes have been prepared by mixing the La0.8Sr0.2MnO3-delta (LSM) electronic phase with the LWO protonic phase. The ceramic-ceramic (cer-cer) composites have been electrochemically studied as cathodes on LWO dense electrolytes in symmetrical cells. Different ratios of both phases and two different electrode sintering temperatures (1050 and 1150 degrees C) have been studied. Electrochemical impedance spectroscopy (EIS) analysis has been carried out in the temperature range 700-900 degrees C under moist (2.5% H2O) atmospheres. Different oxygen partial pressures (pO(2)) have been employed in order to characterize the processes (surface reaction and charge transport) taking place at the composite cathode. A substantial improvement in the cathode performance has been attained by the addition of the LWO protonic phase into the LSM electronic material. From the electrochemical analysis it can be inferred that electrode enhancement is principally ascribed to the increase in the three-phase-boundary length, which enables electrochemical reactions to occur along the thickness of the electrode. ; Funding from European Union (FP7 Project EFFIPRO - Grant Agreement 227560), the Spanish Government (ENE2011-24761 and CSIC Intramural 200880I093 grants) is kindly acknowledged. The authors thank Dr M. Ivanova and Dr D. Sebold (Forschungszentrum Julich, IEK-1) for sample preparation for microscopy analysis, and Mrs M. Fabuel and Dr V. B. Vert for assistance in electrochemical tests. ; Solis Díaz, C.; Navarrete Algaba, L.; Roitsch, S.; Serra Alfaro, JM. (2012). Electrochemical properties of composite fuel cell cathodes ...

[EN] The present work focuses on the study of different Ruddlesden-Popper based cathode materials for Solid Oxide Fuel Cells at Intermediate Temperature (IT-SOFC). The partial substitution of La and Ni by Pr and Co, respectively, were studied in the La(2-x)A(x)Ni(1-y)ByO(4+delta) system, with the purpose of enhancing their mixed ionic-electronic conductivity and the electrocatalytic activity for the O-2-reduction while the crystal structure was preserved. All synthesized compounds were characterized by electrochemical impedance spectroscopy (EIS), DC conductivity measurements, X-Ray diffraction (XRD), iodometric titration and scanning electron microscopy (SEM). XRD analyses by Rietveld refinement revealed the influence of the ionic radius on the crystalline phase for the different dopants, i.e., variation of the cell parameters and M-O bond lengths. The substitution in both La and Ni sites improves La2NiO4+delta electrochemical properties as IT-SOFC cathode, since higher conductivity and lower polarization resistance were obtained. Finally, La1.5Pr0.5Ni0.8Co0.2O4+delta cathode exhibited the lowest electrode polarization resistance and activation energy values in the temperature range of 450-900 degrees C. La1.5Pr0.5Ni0.8Co0.2O4+delta was applied on an anode supported cell and a maximum power density of similar to 400 mW cm(-2) was obtained at 700 degrees C using pure hydrogen and air. ; This work was financially supported by Spanish Government (Grants SEV-2016-0683 and RTI2018-102161) and Generalitat Valenciana (PROMETEO/2018/006). Vicente B. Vert, Ji Haeng Yu and Dae Sik Yun are kindly acknowledged for their support during this work preparation and Forschungszentrum Julich for providing the anode supported cell. ; Navarrete Algaba, L.; Fabuel Robledo, M.; Yoo, C.; Serra Alfaro, JM. (2020). Tailoring La(2-x)A(x)Ni(1-y)ByO(4+delta) cathode performance by simultaneous A and B doping for IT-SOFC. International Journal of Hydrogen Energy. 45(31):15589-15599. https://doi.org/10.1016/j.ijhydene.2020.03.150 ; S ; 15589 ...

[EN] Fe2NiO4-Ce0.8Tb0.2O2-delta (NFO-CTO) composite membranes are of interest to separate oxygen from air. In this study, we investigate the influence of the catalytic activation of NFO-CTO membranes on the oxygen permeation rate. Specifically, the effect of activating porous NFO-CTO layers -coated on both sides of the dense NFO-CTO membrane - with Pr6O11 nanoparticles is studied. Measurements in the temperature range 850-700 degrees C revealed a 2-4 fold increase in the oxygen flux after coating a 30 mm-thick porous NFO-CTO layer on both membrane sides, and a 6-12 fold increase relative to the bare membrane after activating the porous layers coated on both sides of the membrane with Pr6O11 nanoparticles. No degradation of the oxygen fluxes was found in CO2-containing atmospheres. Pulse isotopic exchange measurements confirmed an increase in the oxygen surface exchange rate of more than one order of magnitude after dispersion of Pr6O11 nanoparticles on the surface of NFO-CTO composite powders. Electrochemical impedance spectroscopy measurements on symmetrical cells, using Gd-doped ceria (CGO) as the electrolyte and Pr6O11-activated NFO-CTO electrodes, showed a 10-fold decrease in the polarization resistance compared to non-infiltrated electrodes in air. Modification of porous layers by activation with Pr6O11 nanoparticles is considered a viable route to enhance the oxygen fluxes across composite membranes. ; Financial support by the EU through FP7 GREEN-CC Project (Grant Agreement Number: 608524) and the Spanish Government (ENE2014-57651 and SEV-2016-0683 grants) is gratefully acknowledged. The support of the Servicio de Microscopia Electronica of the Universitat Politecnica de Valencia is also acknowledged. ; García-Fayos, J.; Ruhl, R.; Navarrete Algaba, L.; Bouwmeester, H.; Serra Alfaro, JM. (2018). Enhancing oxygen permeation through Fe2NiO4-Ce0.8Tb0.2O2-delta composite membranes using porous layers activated with Pr6O11 nanoparticles. Journal of Materials Chemistry A. 6(3):1201-1209. ...

[EN] Composites made of different doped cerias and (La0.8Sr0.2)(0.95)MnO3+ were studied as potential solid oxide fuel cell cathodes. Tb, Pr, Gd and Er have been introduced as ceria dopants to enhance the electrocatalytic properties of (La0.8Sr0.2)(0.95)MnO3+ composites fabricated within. Different electrochemical behaviors were observed for the studied composites depending on lanthanide cation nature, i.e., whether they can exhibit different oxidation states or not. Specifically, (La0.8Sr0.2)(0.95)MnO3+/ceria composites with a mixed valence dopants (Tb and Pr) in the CeO2 structure are the best performing and present a limiting step at low frequencies; whereas those with ceria-doping elements withfixed oxidation state (Gd and Er) exhibit the limiting processes at higher frequencies. This fact is related to the higher magnitude of the TPB enlargement in the composite cathode achieved thanks to the promotion of mixed ionic-electronic conductivity in the Pr/Tb-doped ceria phase.The best cathode performance was obtained with (La0.8Sr0.2)(0.95)MnO3+_Ce0.8Pr0.2O2- cathodes with the lowest values for the polarization resistance in the 900-700 degrees C temperature range. ; Funding from Spanish Government (MINECO ENE2014-57651 grant) is kindly acknowledged. ; Navarrete Algaba, L.; Balaguer Ramírez, M.; Vert Belenguer, VB.; Serra Alfaro, JM. (2017). Tailoring Electrocatalytic Properties of Solid Oxide Fuel Cell Composite Cathodes Based on (La0.8Sr0.2)(0.95)MnO3+delta and Doped Cerias Ce(1 x)Ln(x)O(2 delta) (Ln=Gd, La, Er, Pr, Tb and x=0.1 0.2). Fuel Cells. 17(1):100-107. https://doi.org/10.1002/fuce.201600133 ; S ; 100 ; 107 ; 17 ; 1 ; Minh, N. Q. (1993). Ceramic Fuel Cells. Journal of the American Ceramic Society, 76(3), 563-588. doi:10.1111/j.1151-2916.1993.tb03645.x ; Mizusaki, J. (2000). Electronic conductivity, Seebeck coefficient, defect and electronic structure of nonstoichiometric La1â xSrxMnO3. Solid State Ionics, 132(3-4), 167-180. doi:10.1016/s0167-2738(00)00662-7 ; Jiang, S. P. (2003). Issues on development ...

100 107 17 1 ; S ; M. Balaguer 2013 ; [EN] Composites made of different doped cerias and (La0.8Sr0.2)(0.95)MnO3+ were studied as potential solid oxide fuel cell cathodes. Tb, Pr, Gd and Er have been introduced as ceria dopants to enhance the electrocatalytic properties of (La0.8Sr0.2)(0.95)MnO3+ composites fabricated within. Different electrochemical behaviors were observed for the studied composites depending on lanthanide cation nature, i.e., whether they can exhibit different oxidation states or not. Specifically, (La0.8Sr0.2)(0.95)MnO3+/ceria composites with a mixed valence dopants (Tb and Pr) in the CeO2 structure are the best performing and present a limiting step at low frequencies; whereas those with ceria-doping elements withfixed oxidation state (Gd and Er) exhibit the limiting processes at higher frequencies. This fact is related to the higher magnitude of the TPB enlargement in the composite cathode achieved thanks to the promotion of mixed ionic-electronic conductivity in the Pr/Tb-doped ceria phase.The best cathode performance was obtained with (La0.8Sr0.2)(0.95)MnO3+_Ce0.8Pr0.2O2- cathodes with the lowest values for the polarization resistance in the 900-700 degrees C temperature range. Funding from Spanish Government (MINECO ENE2014-57651 grant) is kindly acknowledged. Navarrete Algaba, L.; Balaguer Ramírez, M.; Vert Belenguer, VB.; Serra Alfaro, JM. (2017). Tailoring Electrocatalytic Properties of Solid Oxide Fuel Cell Composite Cathodes Based on (La0.8Sr0.2)(0.95)MnO3+delta and Doped Cerias Ce(1 x)Ln(x)O(2 delta) (Ln=Gd, La, Er, Pr, Tb and x=0.1 0.2). Fuel Cells. 17(1):100-107. https://doi.org/10.1002/fuce.201600133 Minh, N. Q. (1993). Ceramic Fuel Cells. Journal of the American Ceramic Society, 76(3), 563-588. doi:10.1111/j.1151-2916.1993.tb03645.x Mizusaki, J. (2000). Electronic conductivity, Seebeck coefficient, defect and electronic structure of nonstoichiometric La1â xSrxMnO3. Solid State Ionics, 132(3-4), 167-180. doi:10.1016/s0167-2738(00)00662-7 Jiang, S. P. (2003). Issues on ...

[EN] Composites made of La0.8Sr0.2MnO3-delta (LSM) and lanthanide doped ceria (Ce(0.8)Ln(0.2)O(2-delta), Ln = Gd, Er, Tb and Pr) have been proposed as robust and high-performing solid oxide fuel cell cathodes. The addition of small amounts of highly-dispersed CoOx into the electrode promoted the formation of bridges among LSM-ceria particles. These resulted in the reduction of the required sintering temperature due to the enhancement of the sintering and proper ionic and electronic percolation pathways. In addition, Pr as a multivalent cation dopant in ceria showed the best electrochemical results toward oxygen reduction when the electrode sintering temperature is kept at 1000 degrees C. (C) 2016 The Electrochemical Society. All rights reserved. ; This work was supported by funding from Spanish Government (MINECO) (SEV-2012-0267 and ENE2014-57651 grants). ; Navarrete Algaba, L.; Balaguer Ramírez, M.; Vert Belenguer, VB.; Serra Alfaro, JM. (2016). Optimization of SOFC Composite Cathodes Based on LSM and Doped Cerias Ce0.8Ln0.2O2 (Ln = Gd, Er, Tb and Pr). Journal of The Electrochemical Society. 163(13):1440-1443. https://doi.org/10.1149/2.1081613jes ; S ; 1440 ; 1443 ; 163 ; 13

In this work, the carbothermic reduction of iron-and zinc-bearing products is studied through in situ microwave heating, dielectric properties monitoring, and mass spectrometry up to high temperatures (1000 °C). The results are correlated to the information provided by conventional analysis techniques such as differential scanning calorimetry (DSC) and thermogravimetry (TG). This combination allows a detailed study of seven different process stages with an accurate determination of the reaction temperatures, providing new evidence about the particular conditions of this microwave-driven reduction process. The presented results suggest that molecular vibrations imposed by the microwave field are presumably the reason for reactions taking place at lower temperatures than those observed in the conventional process. This work also explores the influence of other parameters, such as the apparent density or the amount of carbonaceous material, on the resulting dielectric properties, providing useful information for the development of a potential microwave industrial application in the metallurgy field. ; This research was funded by the European Union's Horizon 2020 research and innovation programme under Grant Agreement number 820783. ; Peer reviewed

[EN] CsH2PO4 is a proton conductor pertaining to the acid salts group and shows a phase transition from monoclinic to cubic phase at 232 +/- 2 degrees C under high-steam atmospheres (>30%). This cubic phase gives rise to the so-called superprotonic conductivity. In this work, the influence of the partial substitution of Cs by Ba and Rb, as well as the partial substitution of P by W, Mo, and S in CsH2PO4 on the phase transition temperature and electrochemical properties is studied. Among the tested materials, the partial substitution by Rb led to the highest conductivity at high temperature. Furthermore, Ba and S-substituted salts exhibited the highest conductivity at low temperatures. CsH2PO4 was used as electrolyte in a fully-assembled fuel cell demonstrating the applicability of the material at high pressures and the possibility to use other materials (Cu and ZnO) instead of Pt as electrode electrocatalyst. Finally, an electrolyzer cell composed of CsH2PO4 as electrolyte, Cu and ZnO as cathode and Pt and Ag as anode was evaluated, obtaining a stable production of H-2 at 250 degrees C. ; Funding from Spanish Government (SEV-2016-0683, ENE2014-57651 and Juan de la Cierva-Incorporacion 2016 Grants) is kindly acknowledged. ; Navarrete Algaba, L.; Andrio, A.; Escolástico Rozalén, S.; Moya, S.; Compañ Moreno, V.; Serra Alfaro, JM. (2019). Protonic Conduction of Partially-Substituted CsH2PO4 and the Applicability in Electrochemical Devices. Membranes. 9(4):1-11. https://doi.org/10.3390/membranes9040049 ; S ; 1 ; 11 ; 9 ; 4 ; Kreuer, K. D. (2001). On the development of proton conducting polymer membranes for hydrogen and methanol fuel cells. Journal of Membrane Science, 185(1), 29-39. doi:10.1016/s0376-7388(00)00632-3 ; Minh, N. Q. (1993). Ceramic Fuel Cells. Journal of the American Ceramic Society, 76(3), 563-588. doi:10.1111/j.1151-2916.1993.tb03645.x ; Peighambardoust, S. J., Rowshanzamir, S., & Amjadi, M. (2010). Review of the proton exchange membranes for fuel cell applications. International Journal of ...

[EN] In this work, the carbothermic reduction of iron- and zinc-bearing products is studied through in situ microwave heating, dielectric properties monitoring, and mass spectrometry up to high temperatures (1000 degrees C). The results are correlated to the information provided by conventional analysis techniques such as differential scanning calorimetry (DSC) and thermogravimetry (TG). This combination allows a detailed study of seven different process stages with an accurate determination of the reaction temperatures, providing new evidence about the particular conditions of this microwave-driven reduction process. The presented results suggest that molecular vibrations imposed by the microwave field are presumably the reason for reactions taking place at lower temperatures than those observed in the conventional process. This work also explores the influence of other parameters, such as the apparent density or the amount of carbonaceous material, on the resulting dielectric properties, providing useful information for the development of a potential microwave industrial application in the metallurgy field. ; This research was funded by the European Union's Horizon 2020 research and innovation programme under Grant Agreement number 820783. ; García-Baños, B.; Catalá Civera, JM.; Sánchez-Marín, JR.; Navarrete Algaba, L.; López-Buendía, AM.; Schmidt, L. (2020). High Temperature Dielectric Properties of Iron- and Zinc-Bearing Products during Carbothermic Reduction by Microwave Heating. Metals. 10(5):1-15. https://doi.org/10.3390/met10050693 ; S ; 1 ; 15 ; 10 ; 5 ; Omran, M., Fabritius, T., & Mattila, R. (2015). Thermally assisted liberation of high phosphorus oolitic iron ore: A comparison between microwave and conventional furnaces. Powder Technology, 269, 7-14. doi:10.1016/j.powtec.2014.08.073 ; Omran, M., Fabritius, T., Heikkinen, E.-P., & Chen, G. (2017). Dielectric properties and carbothermic reduction of zinc oxide and zinc ferrite by microwave heating. Royal Society Open Science, 4(9), 170710. ...

This work was supported by the Spanish Government (RTI2018-102161, SEV-2016-0683 and Juan de la Cierva grant IJCI-2017-34110). We thank the support of the Electronic Microscopy Service of the Universitat Politècnica de València.

[EN] Hydrogen is a promising vector in the decarbonization of energy systems, but more efficient and scalable synthesis is required to enable its widespread deployment. Towards that aim, Serra et al. present a microwave-based approach that allows contactless water electrolysis that can be integrated with hydrocarbon production. Supplying global energy demand with CO2-free technologies is becoming feasible thanks to the rising affordability of renewable resources. Hydrogen is a promising vector in the decarbonization of energy systems, but more efficient and scalable synthesis is required to enable its widespread deployment. Here we report contactless H-2 production via water electrolysis mediated by the microwave-triggered redox activation of solid-state ionic materials at low temperatures ( 250 degrees C). Water was reduced via reaction with non-equilibrium gadolinium-doped CeO2 that was previously in situ electrochemically deoxygenated by the sole application of microwaves. The microwave-driven reduction was identified by an instantaneous electrical conductivity rise and O-2 release. This process was cyclable, whereas H-2 yield and energy efficiency were material- and power-dependent. Deoxygenation of low-energy molecules (H2O or CO2) led to the formation of energy carriers and enabled CH4 production when integrated with a Sabatier reactor. This method could be extended to other reactions such as intensified hydrocarbons synthesis or oxidation. ; This work was supported by the Spanish Government (RTI2018-102161, SEV-2016-0683 and Juan de la Cierva grant IJCI-2017-34110). We thank the support of the Electronic Microscopy Service of the Universitat Politecnica de Valencia. ; Serra Alfaro, JM.; Borras-Morell, JF.; García-Baños, B.; Balaguer Ramirez, M.; Plaza González, PJ.; Santos-Blasco, J.; Catalán-Martínez, D. (2020). Hydrogen production via microwave-induced water splitting at low temperature. Nature Energy. 5(11):910-919. https://doi.org/10.1038/s41560-020-00720-6 ; S ; 910 ; 919 ; 5 ; 11 ; Serra, J. M. ...