AUTHOR=Furukawa Shinya , Nishimura Genki , Takayama Tomoaki , Komatsu Takayuki 

TITLE=Highly Active Ni- and Co-Based Bimetallic Catalysts for Hydrogen Production From Ammonia-Borane

JOURNAL=Frontiers in Chemistry

VOLUME=7

YEAR=2019

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00138

DOI=10.3389/fchem.2019.00138

ISSN=2296-2646

ABSTRACT=<p>Ammonia-borane is one of the most promising candidates for hydrogen carriers. A series of Ni- and Co-based bimetallic catalysts supported on SiO<sub>2</sub> (Ni–M/SiO<sub>2</sub> and Co–M/SiO<sub>2</sub>; M = Ga, Ge, Sn, Zn) was prepared and tested as catalysts for hydrogen production from ammonia-borane (AB) in water or methanol. Ni–Zn/SiO<sub>2</sub> and Co–Ge/SiO<sub>2</sub> exhibited catalytic activities much higher than those of monometallic Ni/SiO<sub>2</sub> and Co/SiO<sub>2</sub>, respectively. Ni–Zn/SiO<sub>2</sub> showed a high catalytic activity when water was used as a solvent, where the reaction was completed within 6 min at room temperature with a specific reaction rate of 4.3 ml min<sup>−1</sup> mmol-cat<sup>−1</sup> mM-AB<sup>−1</sup>. To the best of our knowledge, this is the highest value among those reported using 3d metal-based catalysts. Co–Ge/SiO<sub>2</sub> afforded a five-fold higher reaction rate than that of the corresponding monometallic Co/SiO<sub>2</sub>. XRD, TEM, and HAADF-STEM-EDS analyses revealed that Ni<sub>0.75</sub>Zn<sub>0.25</sub> and Co<sub>0.8</sub>Ge<sub>0.2</sub> solid-solution alloys were formed with high phase purities. An XPS study showed that Co atoms in Co<sub>0.8</sub>Ge<sub>0.2</sub> were electron-enriched due to electron transfer from Ge to Co, which may be the origin of the improved catalytic activity.</p>