Expeditious re-hydrogenation kinetics of ball-milled magnesium hydride (B-MgH2) decorated acid-treated halloysite nanotube (A-HNT)/polyaniline (PANI) nanocomposite (B-MgH2/A -HNT/PANI) for fuel cell applications.

Our environment is getting effluent day by day due to modernization and industrialization which leads to more serious issues in recent years. Hydrogen energy is considered a green, clean, and sustainable alternative energy carrier. So, the present work is focused on the effective storing of hydrogen on metal hydride (MgH₂) and natural clay nanotube (A-HNT) decorated conductive polymer (PANI) nanocomposite. A facile two-step synthesis was adopted for the preparation of B-MgH₂/A-HNT/PANI nanocomposite. The structural, morphological, elemental, and specific surface area studies of the prepared B-MgH₂/A-HNT/PANI nanocomposite confirm the presence of B-MgH₂, A-HNT, and PANI. During ball milling, more defective sites were created at the surface of MgH₂, A-HNT, and PANI and thereby more specific surface area (441.2 m² g⁻¹) in the case of B-MgH₂/A-HNT/PANI nanocomposite. In contrast, the addition of PANI and A-HNT promotes quick disintegration of B-MgH₂ at 252 °C instead of 352 °C which is authenticated by all-thermal analysis (Thermo Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Temperature-Programmed Desorption (TPD)). The amount of stored hydrogen (Sievert's-like hydrogenation setup) was found to be 7.9 wt% at 110 °C, and the binding energy of stored hydrogen lies in the recommended range (0.33–0.6 eV) of US-Department of Energy (US-DOE) 2025 targets. The prepared B-MgH₂/A-HNT/PANI nanocomposite was utilized as a working electrode in the electrochemical hydrogen storage where 2498 mAh/g discharge capacity (corresponds to 7.5 wt% hydrogen storage capacity) was attained at 24^th cycle of the discharging process. In addition, coulombic efficiency of 95.3%, capacitance retention of 79.8%, and superior corrosion resistance of 25.5 mA/cm² were noticed for B-MgH₂/A-HNT/PANI. The improved electrochemical activity of B-MgH₂/A-HNT/PANI was attributed to the synergistic effect of A-HNT and PANI species in B-MgH₂ towards charge transfer during the charging and discharging processes. Moreover, the hydrogen storage capacity of B-MgH₂/A-HNT/PANI estimated using Sievert's-like hydrogen storage method is almost the same as in the electrochemical storage method. Hence, these characteristics authenticate that the prepared B-MgH₂/A-HNT/PANI nanocomposite may serve as an excellent hydrogen storage medium for weakly chemisorbed hydrogens and as a working electrode to store hydrogens electrochemically for renewable energy storage applications. [ABSTRACT FROM AUTHOR]