Highly efficient hydrogen evolution from the hydrolysis of ammonia borane solution with the Co–Mo–B/NF nanocatalyst

Abstract

Catalytic hydrolysis of ammonia borane (NH3BH3) is considered as a secure and effective way to supply hydrogen (H2) source for the proton exchange membrane fuel cell. Hence, cheap and high activity catalysts need to be exploited. In this work, a series of cobalt–molybdenum–boron (Co–Mo–B) composites were successfully supported on the surface of Ni foam (NF in short) via electroless plating method by tuning the depositional pH values. The as-prepared nanocatalysts were marked as Co–Mo–B/NF and characterized using the inductively coupled plasma-mass spectroscopy, scanning electron microscopy, X–ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy technology. These catalysts showed highly efficient catalytic performance for H2 evolution toward the hydrolysis of NH3BH3 solution, and the optimized Co–Mo–B/NF nanocatalyst deposited at pH = 11.5 achieved a higher H2 evolution rate of 6027.1 mL·min−1·g−1 under ambient temperature. The kinetics tests displayed that hydrolysis reaction catalyzed by Co–Mo–B/NF was zero-order in terms of the NH3BH3 concentration, while it was first-order in view of the catalyst concentration. In addition, the activation energy of NH3BH3 hydrolysis was calculated to be 43.6 kJ·mol−1 with the Co–Mo–B/NF nanocatalyst (pH = 11.5), which was lower than that of most of the previous precious metal and non-precious metal catalysts. The corresponding Gibbs free energy of activation was 43.1 kJ·mol−1, meaning that NH3BH3 hydrolysis reaction was non-spontaneous.