Graphene oxide(GO) is an important derivative of graphene, fascinating the entire world with its dazzling properties and versatile performance. However, the synthesis of GO via chemical routes often results in limited control of the density of functionalities and their distribution, presenting a barrier to the spread of GO applications. We modified Hummers' method and aimed at controlling the oxygen functionality of GO. The highest oxygen content of the modified synthetic GO(Md GO) occurs at edge regions, and the large proportion of carboxyl groups can be easily removed upon annealing. The excellent conductivity of intrinsic graphene can thus be recovered after the removal of the main functional groups. The resulting Md GO was reduced and doped with NH3, and the reduced Md GO(r Md GO) was determined to be an excellent support for oxygen reduction reaction(ORR) electrocatalysts. As a demonstration, a composite of Co O and N-r Md GO was fabricated, which exhibited highly comparable ORR performance in alkaline relative to 20 wt.% Pt/C.
Hydrogenation of benzaldehyde is a typical consecutive reaction, since the intermediate benzyl alcohol is apt to be further hydrogenated. Here we demonstrate that the selectivity of benzyl alcohol can be tuned via functionalization of carbon nanotubes （CNTs）, which are used as the support of Pd. With the original CNTs, the selectivity of benzyl alcohol is 88% at a 100% conversion of benzaldehyde. With introduction of oxygen-containing groups onto CNTs, it drops to 27%. In contrast, doping CNTs with N atoms, the selectivity reaches 96% under the same reaction conditions. The kinetic study shows that hydrogenation of benzyl alcohol is significantly suppressed, which can be attributed to weakened adsorption of benzyl alcohol. This is most likely related to the modified electronic structure of Pd species via interaction with functionalized CNTs, as shown by XPS characterization.
Yonghua ZhouJing LiuXingyun LiXiulian PanXinhe Bao
Oxide nanostructures grown on noble metal surfaces are often highly active in many reactions,in which the oxide/metal interfaces play an important role.In the present work,we studied the surface structures of Fe Ox-on-Pt and Ni Ox-on-Pt catalysts and their activity to CO oxidation reactions using both model catalysts and supported nanocatalysts.Although the active Fe O1x structure is stabilized on the Pt surface in a reductive reaction atmosphere,it is prone to change to an Fe O2x structure in oxidative reaction gases and becomes deactivated.In contrast,a Ni O1x surface structure supported on Pt is stable in both reductive and oxidative CO oxidation atmospheres.Consequently,CO oxidation over the Ni O1x-on-Pt catalyst is further enhanced in the CO oxidation atmosphere with an excess of O2.The present results demonstrate that the stability of the active oxide surface phases depends on the stabilization effect of the substrate surface and is also related to whether the oxide exhibits a variable oxidation state.
Rentao MuQiang FuXiaoguang GuoXuejun XuDali TanXinhe Bao
Commercial production of vinyl chloride from acetylene relies on the use of HgCla as the catalyst, which has caused severe environmental problem and threats to human health because of its toxicity. Therefore, it is vital to explore alternative catalysts without mercury. We report here that N-doped carbon can catalyze directly transformation of acetylene to vinyl chloride. Particularly, N-doped high surface area mesoporous carbon exhibits a rather high activity with the acetylene conversion reaching 77% and vinyl chloride selectivity above 98% at a space velocity of 1.0 mL.min-l.g-1 and 200 ~C. It delivers a stable performa℃nce within a test period of 100h and no obvious deactivation is observed, demonstrating potentials to substitute the notoriously toxic mercuric chloride catalyst.
