Hydrogen is a promising green fuel carrier that can replace fossil fuels; however, its storage is still a challenge. Carbon-based materials with metal catalysts have recently been the focus of research for solid-state hydrogen storage due to their efficacy and low cost. Here, we report on the exfoliation of expanded graphite (EG) through high shear mixing and probe tip sonication methods to form graphene-based nanomaterial ShEG and sEG, respectively. The exfoliation processes were optimized based on electrochemical capacitance measurements. The exfoliated EG was further functionalized with palladium nanoparticles (Pd-NP) for solid-state hydrogen storage. The prepared graphene-based nanomaterials (ShEG and sEG) and the nanocomposites (Pd-ShEG and Pd-sEG) were characterized with various traditional techniques (e.g., SEM, TEM, EDX, XPS, Raman, XRD) and the advanced high-resolution pair distribution function (HRPDF) analysis. Electrochemical hydrogen uptake and release (Q_H) were measured, showing that the sEG decorated with Pd-NP (Pd-sEG, 31.05 mC cm⁻²) and ShEG with Pd-NP (Pd-ShEG, 24.54 mC cm⁻²) had a notable improvement over Pd-NP (9.87 mC cm⁻²) and the composite of Pd-EG (14.7 mC cm⁻²). Q_H showed a strong linear relationship with an effective surface area to volume ratio, indicating nanoparticle size as a determining factor for hydrogen uptake and release. This work is a promising step toward the design of the high-performance solid-state hydrogen storage devices through mechanical exfoliation of the substrate EG to control nanoparticle size and dispersion.

The design, performance, and capabilities of the High Energy beamline at the Brockhouse Sector of the Canadian Light Source are described. The beamline uses a single bent silicon wafer as a side-bounce Laue monochromator, using the (111), (422), or (533) hkl reflections to access energies ranging from 25 to 90 keV. The cryogenically cooled crystal serves as the only optical element in the beamline providing a simple, convenient, and reliable configuration. The bending provides a vertical focus as small as 20 µm. The flux ranges from 1 × 10¹⁰ to 1 × 10¹³ photons s⁻¹, depending on the energy, with typical pre-monochromator slit settings. A large translation table in the hutch moves to follow the beam as the energy is changed. Data are collected using large area detectors. Common uses include rapid collection of powder diffraction data, penetration of thick samples and devices, high pressure diffraction, and pair distribution function measurements.

X-ray total scattering measurements are implemented using a digital flat-panel area detector in an inclined geometry and compared with the traditional geometry. The traditional geometry is defined here by the incident X-ray beam impinging on and normal to the center-most pixel of a detector. The inclined geometry is defined here by a detector at a pitch angle α, set to 15° in this case, bisected by the vertical scattering plane. The detector is positioned such that the incident X-ray beam strikes the pixels along the bottom edge and 90° scattered X-rays impinge on the pixels along the top edge. The geometric attributes of the inclined geometry translate into multiple benefits, such as an extension of the measurable scattering range to 90°, a 47% increase in the accessible magnitudes of the reciprocal-space vector Q and a leveling of the dynamic range in the measured total scattering pattern. As a result, a sixfold improvement in signal-to-noise ratios is observed at higher scattering angles, enabling up to a 36-fold reduction in acquisition time. Additionally, the extent of applied modification functions is reduced, decreasing the magnitude of termination ripples and improving the real-space resolution of the pair distribution function G(r). Taken all together, these factors indicate that the inclined geometry produces higher quality data than the traditional geometry, usable for simultaneous Rietveld refinement and total scattering studies.