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The perovskite La0.15Sm0.35Sr0.08Ba0.42FeO3 − δ has been prepared by the glycine nitrate (GNC) route, varying the fuel/oxidizer ratio (glycine/nitrate, G/N = 1 and 2) and cooling rate (slow cooling and air-quenched), in order to study the influence of sample preparation on the materials' properties, in the context of their application as a cathode material for SOFCs. For this, the performance of the prepared mixed ion and electron conducting perovskite oxides is dictated by their structure, oxygen stoichiometry (3 − δ), chemical composition and thermal expansion properties. High-resolution Synchrotron X-ray powder diffraction patterns were collected at room temperature and at 700 and 800 °C. It was found that the materials had a cubic crystal structure at these temperatures. As expected, 3 − δ decreased as temperature increased, and was slightly smaller for the quenched sample. Higher electrical conductivity values were obtained for the sample with G/N = 1 (air-quenched) in the cooling rate. At 700 and 800 °C the cathode synthesized with G/N = 1 and air-quenched showed the smallest polarization resistance values in impedance spectroscopy studies. Therefore, the physicochemical and electrochemical characterization clearly demonstrated the influence of the synthetic conditions on the cathode performance. ; This research has been funded by the Ministerio de Economía, Industria y Competitividad (MAT2016-76739-R (AEI/FEDER, UE) and MAT2015-86078-R), and Departamento de Educación of the Basque Government (IT-630-13). The authors thank SGIker of UPV/EHU for technical and personnel support. This work was benefited from the BL04-MSPD beamline at ALBA. The authors thank Dr. Francois Fauth of the Experiments Division of ALBA for his assistance in situ synchrotron measurements. K. Vidal thanks UPV/EHU for funding. ; Peer reviewed

The first fluorination of the cuspidine-related phases of Ln4(Al2O7□)O2 (where Ln = Sm, Eu, Gd) is reported. A low-temperature reaction with poly(vinyl-idene difluoride) lead to the fluorine being substituted in place of oxygen and inserted into the vacant position between the dialuminate groups. X-ray photoelectron spectroscopy shows the presence of the F 1s photoelectron together with an increase in Al 2p and rare-earth 4d binding energies supporting F incorporation. Energy-dispersive X-ray spectroscopy analyses are consistent with the formula Ln4(Al2O6F2)O2, confirming that substitution of one oxygen by two fluoride atoms has been achieved. Rietveld refinements show an expansion in the cell upon fluorination and confirm that the incorporation of fluoride in the Ln4(Al2O7□)O2 structure results in changes in Al coordination from four to five. Thus, the isolated tetrahedral dialuminate Al2O7 groups are converted to chains of distorted square-based pyramids. These structural results are also discussed based on Raman spectra. ; This research was funded by the Ministerio de Economía, Industria y Competitividad (MAT2016-76739-R) (AEI/FEDER, UE), and Departamento de Educación of the Basque Government (IT-630–13). The authors thank SGIker of UPV/EHU for technical and personnel support. A. Mora´nRuiz thanks UPV/EHU for funding. ; Peer reviewed

A series of chromite perovskites with the general formula Ln1−xMxCr0.9Ni0.1O3 (Ln = La and/or Nd; M = Sr and/or Ca; x ≤ 0.25) has been prepared by three combustion synthesis routes using a different combustible substance each time: glycine, urea and sucrose. In order to isolate the effect of divalent dopant concentration from the A cation steric effects, the whole group has a fixed mean A cation radius, ≈ 1.22 Å, and cation size disorder, σ2(rA) ≈ 0.0001 Å2, but variable doping x. Their crystal structure, microstructure, electrical properties and expansion coefficients have been investigated on the basis of their possible use as anode materials for intermediate temperature solid oxide fuel cells (SOFC). Cell parameters, grain sizes, expansion coefficients and conductivities all are found to be dependent on x and the combustible substance used. The most interesting relationship is the negative dependence of the conductivity with x under H2 atmosphere: conductivity decreases with doping which is the opposite to the expected behavior for a p-type doped perovskites and has not been reported before. ; This research has been funded by the Ministerio de Economía y Competitividad (MAT2016-76739-R), the Feder program of the European Union and Dpto. Educación, Política Lingüística y Cultura of the Basque Government (IT-630-13). The authors thank for technical and human support provided by SGIker of UPV/EHU. L.Ortega-San-Martin acknowledges Departamento de Ciencias, PUCP (Peru), for funding two shorts stays at UPV/EHU. ; Peer reviewed

The presence of hexavalent chromium water pollution is a growing global concern. Among the currently applied technologies to remove Cr-VI, its adsorption and photocatalytic reduction to Cr-III less mobile and toxic forms are the most appealing because of their simplicity, reusability, and low energy consumption. However, little attention has been paid to bifunctional catalysts, that is, materials that can reduce Cr-VI to Cr-III and retain both hexavalent and trivalent chromium species at the same time. In this work, the dual Cr-VI adsorption-reduction capacity of two iconic photoactive water-stable zirconium and titanium-based metal-organic frameworks (MOFs) has been investigated: UiO-66-NH2 and MIL-125. The bifunctionality of photoactive MOFs depends on different parameters, such as the particle size in MIL-125 or organic linker functionalization/defective positions in UiO-66 type sorbents. For instance, the presence of organic linker defects in UiO-66 has shown to be detrimental for the chromium photoreduction but beneficial for the retention of the Cr-III phototransformed species. Both compounds are able to retain from 90 to 98% of the initial chromium present at acidic solutions as well as immobilize the reduced Cr-III species, demonstrating the suitability of the materials for Cr-VI environmental remediation. In addition, it has been demonstrated that adsorption can be carried out also in a continuous flux mode through a diluted photoactive MOF/sand chromatographic column. The obtained results open the perspective to assess the bifunctional sorption and photoreduction ability of a plethora of MOF materials that have been applied for chromium capture and photoreduction purposes. In parallel, this work opens the perspective to develop specific chemical encoding strategies within MOFs to transfer this bifunctionality to other related water remediation applications. ; Spanish Ministry of Economy and Competitiveness (MINECO) MAT2016-76739-R MAT2016-76039C4-3-R European Commission Basque Government Industry and Education Department under the ELKARTEK (LION, ACTIMAT) Basque Government Industry and Education Department under the HAZITEK (SIMAN) Basque Government Industry and Education Department under the PIBA PIBA-2018-06 European Commission Research & Innovation H2020-MSCA-RISE-2017 INDESMOF project 778412 ; Versión publicada - versión final del editor

Acute Cr(VI)water pollution due to anthropogenic activities is an increasing worldwide concern. The high toxicity and mobility of Cr(VI)makes it necessary to develop dual adsorbent/ion-reductive materials that are able to capture Cr(VI)and transform it efficiently into the less hazardous Cr-III. An accurate description of chromium speciation at the adsorbent/ion-reductive matrix is key to assessing whether Cr(VI)is completely reduced to Cr-III, or if its incomplete transformation has led to the stabilization of highly reactive, transient Cr(V)species within the material. With this goal in mind, a dual ultraviolet-visible and electron paramagnetic spectroscopy approach has been applied to determine the chromium speciation within zirconium-based metal-organic frameworks (MOFs). Our findings point out that the generation of defects at Zr-MOFs boosts Cr(VI)adsorption, whilst the presence of reductive groups on the organic linkers play a key role in stabilizing it as isolated and/or clustered Cr(III)ions. ; Spanish Ministry of Economy and Competitiveness (MINECO) (AEI/FEDER, UE) (FEDER) MAT2016-76739-R MAT2016-76039-C4-3-R Basque Government Industry and Education Departments PIBA-2018-06 European Commission Research & Innovation H2020-MSCA-RISE-2017 INDESMOF project 778412