Correction: The role of ion solvation in lithium mediated nitrogen reduction.

[This corrects the article DOI: 10.1039/D2TA07686A.].

The role of ion solvation in lithium mediated nitrogen reduction.

Since its verification in 2019, there have been numerous high-profile papers reporting improved efficiency of lithium-mediated electrochemical nitrogen reduction to make ammonia. However, the literature lacks any coherent investigation systematically linking bulk electrolyte properties to electrochemical performance and Solid Electrolyte Interphase (SEI) properties. In this study, we discover that the salt concentration has a remarkable effect on electrolyte stability: at concentrations of 0.6 M LiClO4 and above the electrode potential is stable for at least 12 hours at an applied current density of -2 mA cm-2 at ambient temperature and pressure. Conversely, at the lower concentrations explored in prior studies, the potential required to maintain a given N2 reduction current increased by 8 V within a period of 1 hour under the same conditions. The behaviour is linked more coordination of the salt anion and cation with increasing salt concentration in the electrolyte observed via Raman spectroscopy. Time of flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy reveal a more inorganic, and therefore more stable, SEI layer is formed with increasing salt concentration. A drop in faradaic efficiency for nitrogen reduction is seen at concentrations higher than 0.6 M LiClO4, which is attributed to a combination of a decrease in nitrogen solubility and diffusivity as well as increased SEI conductivity as measured by electrochemical impedance spectroscopy.

Evolution of cobalt spin states and magnetic coupling along the SrCo(1-x)Sb(x)O(3-δ) system: correlation with the crystal structure.

The oxides of the SrCo(1-x)Sb(x)O(3-δ) perovskite family have been recently designed, characterized and described as cathode materials for solid-oxide fuel cells with competitive power performance in the temperature range 750-850 °C. They feature a number of interesting properties including a good electronic conductivity, low electrode polarization resistance and adequate thermal expansion; the crystal structure adopts a 3C corner-linked perovskite network with a considerable number of oxygen vacancies. This paper reports on the effects of Sb-doping on the crystal structure features, the Co oxidation state and magnetic properties related to the presence of spin-state transitions in the Co cations. A phase transition was observed from the tetragonal P4/mmm space group for x≤ 0.15 to the cubic Pm ̅3m space group in the x = 0.2 composition from neutron powder diffraction data. For the tetragonal phases the oxygen vacancies were found to be ordered and localized in the axial O2 and equatorial O3 atoms surrounding the Co2 positions. A noticeable distortion of CoO(6) octahedra is observed for x = 0.05 and 0.1, exhibiting a charge-ordering with a mixed oxidation state of Co(3+/4+) at Co1 sites and Co(3+) at Co2 positions: the Jahn-Teller Co(3+) in an intermediate-spin configuration is responsible for the octahedral distortion. Increasing Sb contents promotes a higher average oxidation state of cobalt, from a valence of 3.2+ for x = 0.05 to 3.4+ for x = 0.2, inducing a decrease of the oxygen vacancies and favouring a random distribution over a Pm ̅3m cubic symmetry. All the samples present an antiferromagnetic behaviour with a G-type (k = 0) magnetic structure. The increase of the Sb content induces the weakening of the crystal field (Δ(cf)) in the octahedral environment promoting the Co spin-transition from the intermediate-spin to the high-spin configuration, as evidenced by the decrease of the octahedral distortion, increment of the unit-cell volume and enhancement of the ordered magnetic moment.

Phase transformations in Sr0.8Ba0.2CoO2.5 brownmillerite: correlation between structure and transport properties.

An oxygen-defective perovskite oxide with the title composition has been prepared by soft-chemistry procedures followed by quenching in liquid N(2) from 900 degrees C. This polycrystalline sample has been characterized by temperature-dependent X-ray (XRPD) and neutron powder diffraction (NPD), thermal analysis, electrical conductivity and thermal expansion measurements, in order to correlate the physico-chemical properties and the structural features. At room temperature (RT), the sample adopts an orthorhombic brownmillerite-like structure defined in the Ibm2 space group, containing layers of CoO(6) octahedra alternating with layers of CoO(4) tetrahedra along the b axis. This phase is stable between room temperature and 350 degrees C, where a topotactic intake of oxygen increases the coordination of the tetrahedra to octahedral, with change of the space group to Pnma, as unveiled by the in-situ NPD study. This intermediate phase has been identified for the first time. At 653 degrees C, this phase irreversibly transforms to a hexagonal "H" phase. At 920 degrees C, a cubic perovskite phase "C" is identified, which is transformed again, upon cooling, into the "H" phase at 774 degrees C. The features of the very distinct coordination polyhedra present in the different polymorphs have been correlated with the transport properties. There is a substantial increment of the conductivity at 350 degrees C, upon the oxygen insertion process, concomitant with a contraction of the axial Co-O bonds of the octahedral CoO(6) units and the transformation of the tetrahedra into octahedra, also characterized by dilatometry measurements. The dramatic reduction of the conductivity above 700 degrees C is connected with the transformation to the "H" polymorph, with a complete oxygen sublattice and a face-sharing octahedral framework with a poor 1D electronic conduction. In Sr(0.8)Ba(0.2)CoO(2.5), the plateau of stability of the 3C-like structure, with useful transport properties in the range of sigma = 50-60 S cm(-1), is extended up to 650 degrees C with respect to the pristine SrCoO(2.5). By heating above 900 degrees C, the conductivity abruptly rises when the sample is entering the cubic perovskite region, characterized by a three-dimensional vertex-sharing network of CoO(6) octahedra. The total conductivity displays a maximum value of 75 S cm(-1) at 900 degrees C, which increases during the cooling run, exhibiting a typical metallic behaviour. Moreover, in this cubic phase, the oxygen atoms show large thermal factors of 5.5 A(2), suggesting a considerable mobility and a mixed conductor behaviour.

Effect of Sr content on the crystal structure and electrical properties of the system La2-xSrxNiO4+delta (0

Materials formulated as La(2-x)Sr(x)NiO(4+delta) (0