Tuning the catalytic property of non-noble metallic impurities in graphene

The stable configuration, electronic structure, magnetic property and catalytic activity of single-atom non-noble-metal (NNM) catalysts on graphene are investigated using the first-principles method. In contrast to the pristine graphene, a vacancy defect in graphene strongly stabilises the NNM adatom and makes it more positively charged. The charging leads to the CO adsorption unfavourable, while facilitate the O-2 adsorption, thus alleviating the CO poisoning and improving the reaction possibility for CO oxidation. Besides, there are more electrons transferred between NNM doped-graphene and O-2 molecule, which enhance their interaction and induce changes in the electronic structures and magnetic properties of the systems. Moreover, the sequential processes of CO oxidation on the Co-, Al- and Zn-graphene systems have lower enough energy barriers (<0.4 eV) by the Langmuir-Hinshelwood (LH) reaction (CO + O-2 -> OOCO -> CO2 + O-ads) than that on the Ni-graphene substrate. Among the reaction processes, the rate-controlling step is the breaking of the O-O bond of the OOCO complex to form the CO2 molecule and the atomic O-ads. The results validate the reactivity of NNM catalysts at the atomic scale and initiate a clue for fabricating graphene-based catalysts with low cost and high activity. (C) 2014 Elsevier Ltd. All rights reserved.