Light-Enabled Reversible Hydrogen Storage of Borohydrides Activated by Photogenerated Vacancies

Abstract

Borohydrides, known for ultrahigh hydrogen density, are promising hydrogen storage materials but typically require high operating temperatures due to their strong thermodynamic stability. Here we introduce a novel light-induced destabilization mechanism for hydrogen storage reaction of borohydrides under ambient conditions via photogenerated vacancies in LiH. These vacancies thermodynamically destabilize B–H bonds through the spontaneous “strong adsorption” of BH₄ groups, which trigger an asymmetric redistribution of electrons, enabling hydrogen release at near room temperature, approximately 300 °C lower than the corresponding thermal process. By utilizing specially designed “nano-photothermal reactors”, which optimize thermodynamic destabilization effect with nanoscale dispersed LiH and create space-confined “hotspots” to enhance hydrogen storage kinetics, we achieve an ultrahigh hydrogen storage capacity of 11.02 wt % H₂ in LiBH₄ using only light irradiation. This light-induced destabilization mechanism can also be extended to other alkali metal borohydrides, offering insights for developing solid-state hydrogen storage materials under mild conditions.