Ru and Ru–Ni Nanoparticles on TiO₂ Support as Extremely Active Catalysts for Hydrogen Production from Ammonia–Borane

Abstract

Highly dispersed monometallic Ru nanoparticles can be successfully synthesized on TiO 2 supports for effective hydrogen production from ammonia–borane (NH 3 ·BH 3; AB). The choice of support material and reduction methods were confirmed to significantly influence the size of the Ru nanoparticles, and smaller sizes of Ru nanoparticles with a mean diameter of 1.7 nm could be formed on a TiO 2 support material by H 2 reduction at 200 °C. The catalytic activity of the Ru nanoparticles can be significantly enhanced by alloying with Ni atoms, whereby a significantly high total turnover number (TTO) of approximately 153000 over 8 h was achieved with an excellent turnover frequency (TOF) of 914 min –1 and an activation energy of 28.1 kJ mol –1 . Detailed characterization by means of TEM, EDX, H 2 -TPR, and in situ XAFS measurements revealed that a synergistic alloying effect originates from the random distribution of Ru–Ni nanoparticles with a mean diameter of 2.3 nm and plays a crucial role in the exceptional catalytic performance. This catalytic system has particular potential for industrial application in fuel cells due to advantages such as the facile preparation method, the use of relatively cheap metals, and the exceptionally high catalytic activity.