IUPAC-NIST Solubility Data Series. 95. Alkaline earth carbonates in aqueous systems. Part 1. Introduction, Be and Mg

The alkaline earth carbonates are an important class of minerals. This volume compiles and critically evaluates solubility data of the alkaline earth carbonates in water and in simple aqueous electrolyte solutions. Part 1, the present paper, outlines the procedure adopted in this volume in detail, and presents the beryllium and magnesium carbonates. For the minerals magnesite (MgCO 3), nesquehonite (MgCO 3.3H 2O), and lansfordite (MgCO 3.5H 2O), a critical evaluation is presented based on curve fits to empirical and=or thermodynamic models. Useful side products of the compilation and evaluation of the data outlined in the introduction are new relationships for the Henry constant of CO 2 with Sechenov parameters, and for various equilibria in the aqueous phase including the dissociation constants of CO 2(aq) and the stability constant of the ion pair MCO 3 0(M=alkaline earth metal). Thermodynamic data of the alkaline earth carbonates consistent with two thermodynamic model variants are proposed. The model variant that describes the Mg 2+-HCO 3 - ion interaction with Pitzer parameters was more consistent with the solubility data an d with other thermodynamic data than the model variant that described the interaction with a stability constant

High-yield synthesis of PVP-stabilized small Pt clusters by microfluidic method

Monodisperse PVP-stabilized Pt nanoparticles (PtNPs) with an average diameter of 1.4 ± 0.3 nm were efficiently produced via the complete reduction of Pt4+ ions by BH4- in a micromixer. Because of microfluidic mixing, hydrolytic decomposition of BH4- by the PtNPs formed in the initial stage of the reaction was suppressed, and hence, the PtNP yield was higher than that in the conventional batch mixing. The results of various spectroscopic analyses including EXAFS, FTIR of CO and XPS revealed that the microfluidically synthesized PtNPs were negatively charged and had a high population of edges and vertices on their surface. The PtNPs dispersed in oxygen-saturated water catalyzed the selective oxidation of PhCH2OH to PhCHO

Dopant site in indium-doped SrTiO3 photocatalysts

Strontium titanate, SrTiO3, with the perovskite ABO3 structure is known as one of the most efficient photocatalyst materials for the overall water splitting reaction. Doping with appropriate metal cations at the A site or at the B site substantially increases the quantum yield to split water into H2 and O2. The site occupied by the guest dopant in the SrTiO3 host thus plays a key role in dictating the water splitting activity. However, little is known about the detailed structure of the dopant site in the host lattice. In this study, the local structure of In3+ cations, which were shown to improve the water splitting activity of SrTiO3, is investigated with X-ray absorption fine structure spectroscopy and density functional theory (DFT) calculations. The In3+ cations exclusively substitute for Ti4+ cations at the B site to form InO6 octahedra. Further optical experiments using UV-Vis diffuse reflectance spectroscopy and DFT calculations of the density of states indicate that the substitution of In3+ for Ti4+ does not alter the band structure and bandgap energy (remaining at 3.2 eV). The mechanism underlying the increased water splitting activity is discussed in relation to occupation of the B site by In3+ cations

Development of supported NiO nanocluster for aerobic oxidation of 1-phenylethanol and elucidation of reaction mechanism via X-ray analysis

Supported NiO nanocluster catalysts were synthesized by using Ni colloid as a precursor and applied to the aerobic oxidation of 1-phenylethanol. Obtained catalysts were characterized through X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS) and in situ X-ray diffraction (XRD). Activated carbon (AC) supported NiO nanocluster catalyst showed the catalytic activity to the aerobic oxidation of 1-phenylethanol without any additives. Only the AC support allowed the NiO catalyst to be active although the other supports did not. XAFS and in situ XRD revealed that NiO nanocluster was fixed on the supports successfully. XAFS and XPS gave the information about a difference in the local structure, chemical state and electronic state of Ni among the different supports. The obtained catalyst showed the activity more effectively compared to conventional nickel-based catalysts