Crystal structure of mono-β-alanine hydrochloride

Crystal structure of mono-β-alaninium chloride has been studied by single crystal X-ray diffraction. The compound crystallizes in the orthorhombic system. The space group is Pbca, with the following lattice constants: a = 9.7414(5) Å, b = 7.4671(6) Å, c = 16.5288(11) Å, V = 1202.31(14) Å3, Z = 8. The asymmetric unit contains one β-alaninium cation (+NH3CH2CH2COOH) and one chloride anion. The structure was shown to consist of layers stacked along the c-axis and connected with each other by weak van der Waals forces. Each layer consists of two halves linked by hydrogen bonds between carbonyl and NH3+ groups and, also, between NH3+ groups and Cl- anions. Fourier transform infrared spectrum of β-alaninium chloride was recorded and analyzed. The spectroscopic results were found to support the conclusions of the structural study

Experimental thermochemical verification of trends in thermodynamic stability of hybrid perovskite-type organic-inorganic halides

Hybrid perovskite-type methylammonium lead halides have received great attention in recent years due to high conversion efficiency obtained in solar cells based on such materials. Since the time of the first demonstration photovoltaic devices based on the hybrid perovskites CH3NH3PbX3 (X = Cl, Br, I) have showed huge progress in increase of conversion efficiency reaching currently 20.1%. However, despite very promising achievements fundamental chemistry and physics of hybrid organic-inorganic (HOIP) perovskites is far from being completely understood. In particular it is true for thermodynamic properties of HOIP perovskite-type halides ABX3 and A2BX4 (A=CH3NH3, formamidinium, Cs, Rb, etc; B=Sn, Pb, 3d-element; X = Cl, Br, I). Moreover, reported results of DFT calculations aiming at estimating the stability of these materials often give controversial results. In addition, some of the HOIP perovskites (for example, CH3NH3PbX3 (X = Cl, Br, I)) are known to be entropy-stabilized phases. Therefore experimental verification of the stability trends in HOIP perovskite-type halide systems is strongly required. This is especially important for assessment of the stability of these materials under particular working conditions. Therefore, the main aim of this work was to study the thermodynamics of formation of HOIP perovskite-type halides ABX3 and A2BX4 (A=CH3NH3, formamidinium, Cs, Rb, etc; B=Sn, Pb, 3d-element; X = Cl, Br, I). Their standard formation enthalpy at 298 K was measured by solution calorimetry. Heat capacity was measured in the temperature range 2-298 K using PPMS system. Standard entropy was obtained by integration of the Cp/T vs T curve. Standard Gibbs free energy of ABX3 and A2BX4 (A=CH3NH3, formamidinium, Cs, Rb, etc; B=Sn, Pb, 3d-element; X = Cl, Br, I) was evaluated using measured formation enthalpy and entropy. Trends in variation of the thermodynamic functions with chemical composition and crystal structure of HOIP perovskite-type halides were analyzed and compared with available results of DFT calculations. This work was supported by the Russian Science Foundation (grant No. 18-73-10059)

Thermochemical Study of CH3NH3Pb(Cl1−xBrx)3 Solid Solutions

Hybrid organic–inorganic perovskite halides, and, in particular, their mixed halide solid solutions, belong to a broad class of materials which appear promising for a wide range of potential applications in various optoelectronic devices. However, these materials are notorious for their stability issues, including their sensitivity to atmospheric oxygen and moisture as well as phase separation under illumination. The thermodynamic properties, such as enthalpy, entropy, and Gibbs free energy of mixing, of perovskite halide solid solutions are strongly required to shed some light on their stability. Herein, we report the results of an experimental thermochemical study of the CH3NH3Pb(Cl1−xBrx)3 mixed halides by solution calorimetry. Combining these results with molecular dynamics simulation revealed the complex and irregular shape of the compositional dependence of the mixing enthalpy to be the result of a complex interplay between the local lattice strain, hydrogen bonds, and energetics of these solid solutions

Nonstoichiometry, Defect Chemistry and Oxygen Transport in Fe-Doped Layered Double Perovskite Cobaltite PrBaCo2−xFexO6−δ (x = 0–0.6) Membrane Materials

Mixed conducting cobaltites PrBaCo2−xFexO6−δ (x = 0–0.6) with a double perovskite structure are promising materials for ceramic semi-permeable membranes for oxygen separation and purification due to their fast oxygen exchange and diffusion capability. Here, we report the results of the detailed study of an interplay between the defect chemistry, oxygen nonstoichiometry and oxygen transport in these materials as a function of iron doping. We show that doping leads to a systematic variation of both the thermodynamics of defect formation reactions and oxygen transport properties. Thus, iron doping can be used to optimize the performance of mixed conducting oxygen-permeable double perovskite membrane materials