Enhanced hydrogen generation by solid-state thermal decomposition of NaNH₂-NaBH₄ composite promoted with Mg-Co-B catalyst

The on-site hydrogen supply is a key issue for the commercialization of the fuel cells, which is one of the important ways for realizing a hydrogen-economy society. Composite NaNH₂-NaBH₄ is regarded as a promising high-capacity hydrogen storage material. In this paper, the composite NaNH₂-NaBH₄ (2/1) was synthesized via a solid-state ball milling method. To improve the hydrogen generation kinetics, a multiplex metal boride Mg-Co-B was selected as the catalyst. It was found that Na3BN2 and metal Na were byproducts in the thermal decomposed sample by X-ray diffraction analysis. Thermogravimetry and differential thermal analysis indicated that the main decomposition stages of the catalyst promoted NaNH₂-NaBH₄ material were split into three stages. The activation energy of the Mg-Co-B promoted NaNH₂-NaBH₄ (2/1) material below 300 °C was 76.4 KJ/mol, which is only 47.9% of that of the pristine NaNH₂-NaBH₄ (2/1), and implying much better hydrogen generation kinetics.