▎ 摘　　要

Oxidative addition of aryl halides is an elementary and the rate limiting step common to several cross-coupling reactions. Metal complex-based homogeneous catalysts are conventionally used for catalysing such reactions. In search for heterogeneous catalysts, graphene has been widely used as a support for immobilising catalytically active Pd nanoparticles or clusters. In this study, we investigated the activities of small Pd-n (n = 3, 4) clusters immobilised over pristine and defected graphenes for the oxidative addition of bromobenzene in the presence of water solvation. We compared the adsorption energetics and activation barriers of oxidative addition for a series of graphene supports and contrasted them with homogeneous free Pd-n catalysts. Our theoretical investigations reveal the defected graphene supports to act as charge donors thereby drastically reducing the activation barriers of oxidative addition of bromobenzene when compared to free Pd-n clusters. Double vacancy defected graphene and B-doped graphene were concluded as the best support materials providing stronger traps for small Pd-n (n = 3, 4) clusters and reducing the oxidative addition barriers, making them potential heterogeneous catalysts for cross-coupling reactions.