Capability of defective graphene-supported Co4 nanoparticle toward ammonia dehydrogenation

Abstract

Performing density functional theory calculations, we have studied the adsorption of nanoparticle Con (n = 2, 4, 6) on graphene sheets and Co4 stands out for the most favorable stability. Furthermore, the catalytic activity of Co4-supported on a variety of graphene sheets was explored toward ammonia dehydrogenation. Present results demonstrate that the existence of C-vacancy in graphene considerably enhances the interaction of NHx (x = 3–0) with Co4 cluster, and effectively facilitates H abstraction from ammonia. Specifically, Co4 anchored on monovacancy graphene sheet outperforms the others for its superb catalytic activity in NH3 decomposition, giving rise to the intermediates NH and/or N bound with the nanocomposite. In contrast, doping of N or B atom in graphene hinders the NH bond cleaving of NH3. The higher catalytic activity of Co4 supported over the vacancy graphene is correlated well with the lower d-band center value relative to the Fermi level, consistent with the literature emphasizing on the importance of support to metal catalysts.