Synergetic effect of Au nanoparticles and transition metal phosphides for enhanced hydrogen evolution from ammonia-borane.

Schematic diagram: Synergetic effect of Au NPs loading over Ni 2 P & CoP for H 2 evolution. [Display omitted] • The catalysts (Au/Ni 2 P, Au/CoP) are synthesized and optimized. • The XPS reveals that the synergetic effect of Au/Ni 2 P is stronger than Au/CoP. • The activation energy of Au/CoP is less than Au/Ni 2 P. • Active sites for ammonia-borane hydrolysis are Auδ+ and (Ni 2 P & CoP) δ-. The hydrogen evolution from ammonia borane is intriguing but challenging due to its sluggish kinetics. In this regard, the gold nanoparticles amalgamation with metal phosphides is speculated to be more efficient catalysts. Here, the catalysts Au/Ni 2 P and Au/CoP with the high synergetic effect of Au nanoparticles and metal phosphides were synthesized for ammonia borane hydrolysis. The activity of Au/Ni 2 P increases 4.8-fold (i.e., 0.08 to 0.40 L∙h−1) compared to pristine Ni 2 P, and the activity of Au/CoP increases 1.7-fold (i.e., 0.74 to 1.27 L∙h−1) compared to pristine CoP. This reveals that the synergetic effect of Auδ+ and (Ni 2 P) δ- is stronger than Auδ+ and (CoP) δ- which is manifested by XPS analysis. The kinetics exposes that the activation energy of Au/Ni 2 P (45.28 kJ∙mole-1) is greater than Au/CoP (31.45 kJ∙mole-1) and the TOF of Au/Ni 2 P is less than Au/CoP. This research work presents an effective approach for producing active sites of Auδ+ and (Ni 2 P & CoP) δ- for ammonia borane hydrolysis to enhance the H 2 evolution rate. [ABSTRACT FROM AUTHOR]