Hydrogen production via selective dehydrogenation of hydrazine borane and hydrous hydrazine over MoOx-promoted Rh catalyst

Abstract

Hydrazine borane (N2H4BH3, 15.4 wt%) and hydrous hydrazine (N2H4·H2O, 8 wt%) are promising chemical hydrogen storage materials that have attracted much attention in recent years due to their high gravimetric hydrogen capacities. The selective and rapid catalytic dehydrogenation of N2H4BH3 and N2H4·H2O is the key to the potential use of the abovementioned materials in hydrogen applications. In this study, a series of Rh-MoOx nanoparticles (NPs) with various metal compositions have been successfully prepared via a simple one-step chemical reduction approach in the absence of a surfactant/support at room temperature. The obtained surfactant/support-free Rh-MoOx NPs exhibit good dispersibility and small particle size. Among all of the as-prepared Rh-MoOx NPs, the optimized Rh-MoOx catalysts with a molar ratio of 1:1 show the highest catalytic properties with 100% H2 selectivity for hydrogen evolution from aqueous N2H4BH3 and N2H4·H2O solutions at 323 K under alkaline conditions. The turnover frequency (TOF) values of Rh0.5(MoOx)0.5 NPs are 2000 and 750 h−1 for hydrogen evolution from N2H4BH3 and N2H4·H2O, respectively, which are among the highest values ever reported for Rh-based catalysts. The superior catalytic performances could be attributed to the small particles size, low crystallinity, modified electronic structure, and strong basic sites of Rh NPs induced by the MoOx dopant. The highly rapid and selective Rh-MoOx catalyst may further encourage the deployment and application of N2H4BH3 and N2H4·H2O as safe and convenient sources of hydrogen for fuel cells.