Atomic-scale selectivity of hydrogen for storage sites in Pd nanoparticles at atmospheric pressure

Accelerated Hydrogen "Spill-Over" Enhances Anode Performance of Tensile Strained Pd-Based Fuel Cell Electrocatalysts

Development of efficient electrocatalysts usually relies on half-cell electrochemical tests for rapid material screening, which however are not always consistent with the associated full cell evaluation. This study designs a tensile-strained Pd anode and reveals that with a lower apparent activity toward the hydrogen oxidation reaction as compared to the unstrained one, it exhibits a surprisingly high activity in proton exchange membrane fuel cells (PEMFCs). With an ultralow Pd loading of 4.5 µg cm^-2 , the tensile-strained Pd achieves a maximum power density of 1048 mW cm^-2 , indicating a 30-fold improvement in power efficiency than that of commercial Pd/C, nearly four times of that of the unstrained one. This discrepancy can be ascribed to the hydrogen-rich surface in the H₂ atmosphere of PEMFCs owing to the accelerated hydrogen "spill-over" in the tensile-strained Pd with a standout hydrogen storage property.

Li-fluorine codoped electrospun carbon nanofibers for enhanced hydrogen storage

Carbon materials have attracted increasing attention for hydrogen storage due to their great specific surface areas, low weights, and excellent mechanical properties. However, the performance of carbon materials for hydrogen absorption is hindered by weak physisorption. To improve the hydrogen absorption performance of carbon materials, nanoporous structures, doped heteroatoms, and decorated metal nanoparticles, among other strategies, are adopted to increase the specific surface area, number of hydrogen storage sites, and metal catalytic activity. Herein, Li–fluorine codoped porous carbon nanofibers (Li–F–PCNFs) were synthesized to enhance hydrogen storage performance. Especially, perfluorinated sulfonic acid (PFSA) polymers not only served as a fluorine precursor, but also inhibited the agglomeration of lithium nanoparticles during the carbonization process. Li–F–PCNFs showed an excellent hydrogen storage capacity, up to 2.4 wt% at 0 °C and 10 MPa, which is almost 24 times higher than that of the pure porous carbon nanofibers. It is noted that the high electronegativity gap between fluorine and lithium facilitates the electrons of the hydrogen molecules being attracted to the PCNFs, which enhanced the hydrogen adsorption capacity. In addition, Li–F–PCNFs may have huge potential for application in fuel cells.

We developed a facile, yet general, approach for preparing Li–fluorine codoped porous carbon nanofiber (Li–F–PCNF) composites, which showed excellent hydrogen storage performance.