Stabilization of NaZn(BH4)3via nanoconfinement in SBA-15 towards enhanced hydrogen release

Abstract

In the present work, the decomposition behaviour of NaZn(BH₄)₃ nanoconfined in mesoporous SBA-15 has been investigated in detail and compared to bulk NaZn(BH₄)₃ that was ball milled with SBA-15, but not nanoconfined. The successful incorporation of nanoconfined NaZn(BH₄)₃ into mesopores of SBA-15 was confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, ¹¹B nuclear magnetic resonance, nitrogen absorption/desorption isotherms, and Fourier transform infrared spectroscopy measurements. It is demonstrated that the dehydrogenation of the space-confined NaZn(BH₄)₃ is free of emission of boric by-products, and significantly improved hydrogen release kinetics is also achieved, with pure hydrogen release at temperatures ranging from 50 to 150 °C. By the Arrhenius method, the activation energy for the modified NaZn(BH₄)₃ was calculated to be only 38.9 kJ mol⁻¹, a reduction of 5.3 kJ mol⁻¹ compared to that of bulk NaZn(BH₄)₃. This work indicates that nanoconfinement within a mesoporous scaffold is a promising approach towards stabilizing unstable metal borohydrides to achieve hydrogen release with high purity.