The chemical storage and release of hydrogen under mild conditions are of importance to the hydrogen-economy paradigm. Ammonia-Borane (AB) has been regarded as a competitive candidate for chemical hydrogen storage because of its high hydrogen content, non-toxicity, and long-term stability under ambient temperature. Fast hydrogen evolution from AB has been achieved using noble metal nanoparticles (e.g. Rh and Pt) as the catalyst. However, all non-noble metal catalysts (e.g. Fe, Co, Ni nanoparticles) still display relatively poor catalytic activity; the TOF is usually less than 70 min–1 at room temperature for these systems. Therefore, the development of high-efficiency and noble-metal-free catalysts for hydrogen release is highly desirable. Metal phosphides with partial charge transfer from metal to P have been discovered to be promising catalysts for AB hydrolysis. However, the specific mechanism about how the electronic structure of metal phosphide influenced the catalytic performance and why the presence of extra OH– could dramatically improve the activity are unclear. In this work, ternary Ni-Co-P nanoparticles with various metal elemental ratios and electronic structures are firstly used as catalysts for AB hydrolysis. The incorporation of Co into Ni2P effectively optimizes the electronic structures of Ni2-xCoxP catalysts to enhance their interaction with AB and simultaneously facilitate the hydroxyl activation of AB, resulting in the reduction of reaction energy barrier and thus substantial improvement of the catalytic rate.
Ternary Ni-Co-P Nanoparticles and Their Hybrids with Graphene as Noble-metal-free Catalysts to Boost the Hydrolytic Dehydrogenation of Ammonia-Borane
Energy Environ. Sci. 2017, 10, 1770-1776, DOI: 10.1039/C7EE01553D.