A multifunctional catalytic system has been developed for the efficient hydrolysis of ammonia borane, a promising candidate for on-board hydrogen storage applications (1). The proposed catalytic system combines metal nanoparticles, acid sites, and amines; all targeting specific functionalities for the destabilization and cleavage of the N→B dative bond (2). The use of zeolites as supports for the different functionalities more than doubles the activity for the hydrolysis of ammonia borane when compared to less acidic supports, such as silica (see Figure 1). Acid sites weaken the interaction between the ammonia and the borane by transferring a H+ from the zeolite to the ammonia. The amount of acid sites present in the system, tuned through the use of zeolites with different SiO2/Al2O3 ratio, has a direct relationship with the activity of the catalyst. The incoporation of amines to the catalyst, specifically p-phenylenediamine (PPD), significantly decreases the stability of ammonia borane by forming a hydrogen bond with the hydrogens of the ammonia. Finally, bimetallic nanoparticles with low Pd content, i.e. Pd/Co = 0.1/0.9 molar ratio, present similar activity than those catalysts containing only noble metal (Pd NPs). Excellent activity for the final multifunctional catalyst has been observed, namely 108.2 min-1, which amounts to 18 times higher activity compared to a catalyst based on colloidal Pd NPs.

Improving hydrogen production from ammonia borane hydrolysis by using acid supports

255th National Meeting (2018)

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