Dataset of Exploring Tribochemical Transduction Pathways for Dehydrogenation of Molecular Hydrides

Cylindrical pellets 13 mm in diameter and ca. 2 mm thick were obtained by compacting, under uniaxial pressure of 65 MPa, of commercial powder of EDAB (Boron Specialties, 97% purity). The pellets were prepared and conserved under a static Ar atmosphere before and after the tests. X-ray diffraction (Cu Kα radiation, θ/2θ configuration, 10° - 60° 2θ range) was used to analyze the pellet structure. Thermal gravimetric analysis coupled with mass spectrometry (TGA-MS) under argon flow (heating rate: 10°C/min) was used to evaluate thermal stability and the composition of emitted gases. During the isothermal test the required temperature was attained at a heating rate 10 ºC/min and then maintained constant for 90-380 min depending on the temperature. The ion currents were measured in the range of mass-to-charge ratios from 1 to 90. Micro-Raman confocal spectrometry (incident laser: 532 nm, power: 5.6 mW) and FTIR microscopy was used to analyze the chemical structure of mechanically affected zones compared to pristine areas. It was conducted under normal atmosphere. In-plane thermal conductivity of EDAB pellets was determined using van der Pauw method. Nanoindentation with a Berkovich diamond tip (load: 5-20 mN, peak load hold time: 120 s, loading/unloading rates: 4-40 mN/min, 10 measurements for each load) was used to characterize mechanical properties. Tribochemical reactions under vacuum were studied in real time using Mechanically Stimulated Gas Emission Mass Spectrometry (MSGE-MS) which was described in detail elsewhere. This technique combines a mass-spectrometry, a nearly zero-emission ultrahigh vacuum friction cell and a dynamic gas expansion system. The latter allows for accurate quantification of emitted gas rates with the detection limit around 1 pmol/s. The tribostimulation of the pellets was done using an alumina ball, 3 mm in diameter, under normal load 0.44-1.1 N and the frequency of reciprocating motion 1 full cycle (forward and backward strokes) per second. The additional arrangements which were made to avoid undesirable gas emission sources other than triboemission from mechanically affected zones of the sample are described in ESI. The tribostimulated gas emission was determined from the mass-spectrometry signal and benchmarked against the steady background gas pressure with the indenter standing still. The Differential Mass-Spectra (DMS) were derived by subtracting the reference spectrum from the mass-spectra measured during tribostimulation. A separate experiment to investigate possible chemical changes in the EDAB under applied mechanical deformation was conducted using Nuclear Magnetic Resonance (NMR). For this experiment about 0.5 g of EDAB powder was grounded in a porcelain mortar just prior to the NMR analysis. A portion of the ground EDAB was analyzed using solid state Magic Angle Spinning (MAS) 1H and 11B NMR, while the other one was analyzed using 1H and 11B solution RMN using deuterated dimethyl sulfoxide (DMSO-d6) as a solvent.