Thermal decomposition kinetics of light-weight composite NaNH2–NaBH4 hydrogen storage materials for fuel cells

Pristine and Co–B doped NaNH2–NaBH4 (2/1 molar rate) hydrogen storage materials were synthesized via a ball milling method. The kinetic parameters, especially the activation energies were calculated by the Achar differential and the Coats–Redfern integral methods, based on the thermogravimetry curves of the decomposition processes of the hydrogen storage materials. The as-obtained activation energy for the pristine NaNH2–NaBH4 (2/1) is 159.6 kJ/mol, while that for the Co–B doped NaNH2–NaBH4 (2/1) is 70 kJ/mol, only 43.9% of the former, which indicates the Co–B catalyst can dramatically promote the hydrogen generation reaction. The structural evolution and the hydrogen releasing performance of the Co–B doped NaNH2–NaBH4 (2/1) were investigated by X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA). Then, the catalytic mechanism of NaNH2–NaBH4 (2/1) decomposition promoted by Co–B was discussed and illustrated. It implies that the existence of Co–B catalyst can promote the loss of electron from H−, thus improve the kinetics and accelerate the formation of H2 upon heating.