Stratified nanoporous PtTi alloys for hydrolysis of ammonia borane.

Stratified nanoporous PtTi (SNP-PtTi) alloys with bimodal size distributions and different components are successfully prepared by selectively dissolving Al atoms followed by removing part of Ti atoms from the PtTiAl precursor alloy. The as-made PtTi alloys have stratified nanoporous architecture with the first order ligaments around 50nm and the second order smaller ligaments around 6nm. The SNP-PtTi alloys with different bimetallic ratios exhibit much higher catalytic activity for the hydrolysis of ammonia borane than NP-Pt catalyst. The SNP-Pt65Ti35 alloy shows superior specific activity toward the hydrolytic dehydrogenation of ammonia borane compared with SNP-Pt50Ti50 and -Pt80Ti20, showing an initial turnover frequency of 51.4mol H2 (molPt)(-1)min(-1). The activation energy of SNP-Pt65Ti35 was estimated to be about 39.4kJmol(-1), which was small compared with most of the reported activation energy values in the literature. In addition, the recyclability tests indicate that the SNP-Pt65Ti35 retained 63% of the initial catalytic activity after the fifth run of hydrolysis. The lifetime of SNP-Pt65Ti35 was measured as 16,380 turnovers over 100h in the hydrolysis of ammonia borane before deactivation. The SNP-PtTi alloys show potential application prospect in the field of online hydrogen production due to the high catalytic performance and the facile preparation.