Synergistic enhancement of Co doped Ni/NiOx nanofilms for catalytic hydrolysis towards ammonia borane

Abstract

Transition metal catalysts exhibit a potential application for the hydrolytic dehydrogenation of ammonia borane (AB). The regulation of active sites through heterogeneous metal doping have been acknowledged as an efficient technology. Herein, Co-doped Ni/NiO nanofilms (Ni/NiCoOx-Y, Y is Co/(Co + Ni) atom ratio) were synthesized on an ionic liquid (IL)/water interface, in which Co atoms are uniformly doped in the basal NiO crystal lattice in the form of Co ions. The Ni/NiCoOx-Y catalysts exhibit a “volcanic” relationship between the catalytic activities for AB hydrolysis and Co-doped content. The optimized Ni/NiCoOx-20 nanofilms exhibit observably enhanced catalytic activity for AB hydrolysis, completely producing H2 within 4 min with a turnover frequency of 12.93 molH2·molmetal−1·min−1 and a low activation energy of 39.57 kJ mol−1. Moreover, Co doping can effectively enhance the stability of Ni-based nanofilms. The incorporation of Co ions into Ni/NiO crystal lattice slightly increases Ni electron density or Ni lattice expansion. Thus “electronic effect” strengthens the adsorption of H2O/intermediates and further beneficially accelerate combination of AB and H2O molecules, contributing to the improved catalytic activity. Meantime, the strong interaction of Co–Ni atoms can utilize the synergistic enhancement effect.