Enhanced Hydrogen Production from Ammonia Borane over Ni Nanoparticles Supported on TiN-TiO_2 Composites under Sunlight

摘要

Titanium dioxide-titanium nitride composite (TiO2-TiN) nanoparticles (NPs) were used as a support to load nickel nano particles for the dehydrogenation of ammonia borane (AB) which is a new method. The composite support was fabricated via a simple ultrasonic mixing route, followed by the in situ loading of Ni NPs using a liquid-phase reduction reaction method where sodium borohydride was adopted as a reducing agent. The synthesized samples were characterized by X-ray diffraction spectra (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Ultra Violet-Visible (UV-vis) analyses. The characterization results show that the Ni NPs uniformly dispersed on the support and existed in both zero and oxidized states. Compared with bare TiO2, Ni loading on TiO2-TiN exhibited a higher catalytic activity toward dehydrogenation of AB both under dark and under sunlight irradiation. Ni/10TiN-TiO2 showed a hydrogen evolution rate with a turnover frequency (TOF) of 8.01 mol(H2).min(-1).mol(cat)(-1) at 25 degrees C under sunlight. The loading of Ni NPs lowered the band gap energy of TiO2, resulting in the enhanced absorption of sunlight. The addition of TiN that acts as electron scavengers improved the separation efficiency of electron-hole pairs. Titanium dioxide-titanium nitride composites play an important role in improving the catalytic dehydrogenation of AB by nickel-based catalysts.