Doping and Structure-Promoted Destabilization of NaBH₄ Nanocubes for Hydrogen Storage

Abstract

Sodium borohydride (NaBH 4 ) is a potential candidate for hydrogen storage; however, its high thermodynamic stability has hampered its practical use. Doping NaBH 4 with transition metals is an efficient way to improve its hydrogen properties; however, even with the most effective dopants, the temperatures required for hydrogen release are still too high (above 400 °C) for practical use. Herein, we report on vanadiumdoped NaBH 4 (V-NaBH 4 ) nanocubes and the related core−shell like (V-NaBH 4 @Ni) structure, which outperforms conventional transition metal (e.g., Co, Cu, Fe, Nb, Ti)-doped NaBH 4 systems and significantly lowers the hydrogen release temperature of V-NaBH 4 @Ni to 355 °C. Notably, V-NaBH 4 @Ni releases up to 5.3 mass% H 2 below 200 °C, which is a significant improvement compared to unmodified NaBH 4 . Detailed structural investigations revealed that the improved hydrogen release is due to the synergistic effects of the unique core−shell structure and the in situ formed V x B y and Ni x B y at the core−shell interface. The formation of these intermediate borides is believed to enhance the electron transfer from BH 4 − to the boride site and trigger hydrogen release at lower temperatures. This study provides, for the first time, convincing evidence of accelerated decomposition of NaBH 4 in the core−shell structure and paves the way toward tuning the hydrogen properties of transition-metal doped core−shell hydrides.

Reversible Hydrogen Storage in Solid‐State Reaction Derived Core‐Shell NaBH4@Ni Nanocubes

“…[28] However, no appreciable shift in the diffraction patterns of NaBH 4 was observed in agreement with our previous findings on V-NaBH 4 and V-NaBH 4 @Ni prepared via solvent-based method. [27] For V-NaBH 4 @Ni-30, the decrease in peak intensity corresponding to the NaBH 4 phase may indicate the formation of Ni shell over NaBH 4 cores in agreement with our previous studies. [12a,20,21,27] However, we did not find any trace of metallic Ni/V or Ni x B y /V x B y by XRD, which is likely due to their highly dispersed or amorphous nature.…”

“…We also demonstrated that the presence of boride species (V x B y and Ni x B y ) is essential to destabilize borohydride and improve its hydrogen release and uptake. [27] The present study once again provides convincing evidence for improved hydrogen release and uptake of V-doped core-shell borohydride structures. These results also emphasize that compared to the destabilization achieved by Cl À , Br À , or F À substitutions, V doping leads to the formation of V x B y species, accelerates the H 2 release/uptake in the core-shell structure and bypasses the formation of B 12 H 12 .…”

“…The improvement in hydrogen uptake could be due to the core-shell structure and/or presence of Ni x B y /V x B y species in good agreement with our investigations on core-shell V-NaBH 4 @Ni. [20,27]…”

Nanoscale engineering of solid-state materials for boosting hydrogen storage

“…Recently, Aguey-Zinsou's group confined vanadium-doped NaBH 4 (V-NaBH 4 ) nanocubes inside a Ni shell (V-NaBH 4 @Ni), which significantly lowers the onset desorption temperature to 323 K, which is a significant improvement compared to unmodified NaBH 4 (∼773 K). 208 As shown in Fig. 9d, the improved H 2 release performance could be attributed to the formation of V/V x B y and Ni/Ni x B y species at the interfaces between the NaBH 4 core and Ni shell, which facilitate the destabilization of NaBH 4 .…”

Trimetallic Zn–Co–Ni Selenide Nanoparticles as Electrocatalysts for the Hydrogen Evolution Reaction

“…Everlasting consumption of fossil fuels on a large scale leads to increasing CO 2 emissions, resulting in serious issues for our society and environment . Hence, the development of renewable and green energy sources is essential to replace conventional fossil fuels. − Hydrogen could be a best alternative to conventional energy sources owing to its highest energy density and environmental friendliness. − At present, the production of hydrogen on an industrial scale is carried out primarily using steam formation and coal gasification. However, these techniques either consume fossil fuels, generate comparatively less hydrogen, and/or emit other harmful gases .…”