Electron irradiation and thermal chemistry studies of interstellar and planetary ice analogues at the ICA astrochemistry facility

The modelling of molecular excitation and dissociation processes relevant to astrochemistry requires the validation of theories by comparison with data generated from laboratory experimentation. The newly commissioned Ice Chamber for Astrophysics-Astrochemistry (ICA) allows for the study of astrophysical ice analogues and their evolution when subjected to energetic processing, thus simulating the processes and alterations interstellar icy grain mantles and icy outer Solar System bodies undergo. ICA is an ultra-high vacuum compatible chamber containing a series of IR-transparent substrates upon which the ice analogues may be deposited at temperatures of down to 20 K. Processing of the ices may be performed in one of three ways: (i) ion impacts with projectiles delivered by a 2 MV Tandetron-type accelerator, (ii) electron irradiation from a gun fitted directly to the chamber, and (iii) thermal processing across a temperature range of 20–300 K. The physico-chemical evolution of the ices is studied in situ using FTIR absorbance spectroscopy and quadrupole mass spectrometry. In this paper, we present an overview of the ICA facility with a focus on characterising the electron beams used for electron impact studies, as well as reporting the preliminary results obtained during electron irradiation and thermal processing of selected ices. Graphic Abstract

Nickel Sulfate Aqueous Solutions Thermal Chemistry and Enthalpy of Ni2+ Cation Formation at the Temperature 298.15 K

Calorimeter with an isothermal shell was used at a temperature of 298.15 K to measure the following parameters: enthalpy of NiSO4(k) dissolution in water followed by generation of two molar concentration solutions; enthalpy of four NiSO4 aqueous solutions dilution having various molar concentrations followed by generation of solutions with approximately the same concentration values. Based on the data obtained, enthalpy and ion association constant in the NiSO4 aqueous solution, as well as standard enthalpy of the aqueous solution formation, were determined for the indicated compound. The latter value made it possible to establish a more accurate value of standard enthalpy in the Ni2+ cation formation in an aqueous solution, which turned out to be equal to --52.3 ± 0.5 kJ/mol.

Correction: Nickel clusters on TiO2(110): thermal chemistry and photocatalytic hydrogen evolution of methanol

Correction for ‘Nickel clusters on TiO2(110): thermal chemistry and photocatalytic hydrogen evolution of methanol’ by Moritz Eder et al., Catal. Sci. Technol., 2020, DOI: 10.1039/d0cy01465f.

Nickel clusters on TiO2(110): thermal chemistry and photocatalytic hydrogen evolution of methanol

While nickel clusters, similar as to platinum ones, facilitate the thermal recombination of hydrogen in the photocatalysis of alcohols, they also undergo photocorrosion over time by the formation of carbon deposits.

Electron-driven and thermal chemistry during water-assisted purification of platinum nanomaterials generated by electron beam induced deposition

Focused electron beam induced deposition (FEBID) is a versatile tool for the direct-write fabrication of nanostructures on surfaces. However, FEBID nanostructures are usually highly contaminated by carbon originating from the precursor used in the process. Recently, it was shown that platinum nanostructures produced by FEBID can be efficiently purified by electron irradiation in the presence of water. If such processes can be transferred to FEBID deposits produced from other carbon-containing precursors, a new general approach to the generation of pure metallic nanostructures could be implemented. Therefore this study aims to understand the chemical reactions that are fundamental to the water-assisted purification of platinum FEBID deposits generated from trimethyl(methylcyclopentadienyl)platinum(IV) (MeCpPtMe3). The experiments performed under ultrahigh vacuum conditions apply a combination of different desorption experiments coupled with mass spectrometry to analyse reaction products. Electron-stimulated desorption monitors species that leave the surface during electron exposure while post-irradiation thermal desorption spectrometry reveals products that evolve during subsequent thermal treatment. In addition, desorption of volatile products was also observed when a deposit produced by electron exposure was subsequently brought into contact with water. The results distinguish between contributions of thermal chemistry, direct chemistry between water and the deposit, and electron-induced reactions that all contribute to the purification process. We discuss reaction kinetics for the main volatile products CO and CH4 to obtain mechanistic information. The results provide novel insights into the chemistry that occurs during purification of FEBID nanostructures with implications also for the stability of the carbonaceous matrix of nanogranular FEBID materials under humid conditions.