Synthesis of Longtime Water/Air-Stable Ni Nanoparticles and Their High Catalytic Activity for Hydrolysis of Ammonia-Borane for Hydrogen Generation

In this paper, two kinds of Ni nanoparticles have been successfully synthesized without and with starch as the "green" protective material and investigated as catalysts for generating hydrogen from ammonia borane (NH3BH3, AB). Experimental investigations have demonstrated that both of the Ni nanoparticles possess high catalytic activities for H-2 generation from aqueous solution of AB. However, the catalytic activities of Ni nanoparticles without starch decrease seriously in the course of the lifetime tests. In contrast, the catalytic activities of the Ni nanoparticles with starch almost keep unchanged even after 240 h. Moreover, the XPS results show that the surface of the Ni nanoparticles in starch solution is still metallic Ni even after 240 h, while that in pure water is nickel oxide. This means that starch can successfully keep the Ni nanoparticles in aqueous solution from the oxidation in air. The present efficient, low-cost, and longtime water/air stable Ni catalyst represents a promising step toward the development of AB as a viable on-board hydrogen storage and supply material.