Vertically Aligned N-Doped Diamond/Graphite Hybrid Nanosheets Epitaxially Grown on B-Doped Diamond Films as Electrocatalysts for Oxygen Reduction Reaction in an Alkaline Medium.

Diamond/graphite hybrid nanosheets (DGNSs) have been epitaxially grown on boron-doped diamond (BDD) films from CH4/H2 mixture gas by microwave plasma chemical vapor deposition. The DGNSs are vertically aligned on the crystal facets of the BDD films uniformly, densely, and orderly. The DGNSs are composed of the core diamond sheets and the surface graphitic overlayers, which possess an open edge structure. By posttreatment in NH3 atmosphere in a microwave plasma or a tube furnace, the N-doped DGNSs (NDGNSs) were obtained. The electrocatalytic performance toward oxygen reduction reaction (ORR) for the DGNSs was greatly enhanced after doping with N, and the doped pyridinic N contributes more to the ORR. The electrocatalytic activity for ORR of the NDGNSs doped at 650 °C in NH3 in a tube furnace is the highest in all of the samples, which is comparable to the commercial Pt/C. The present work provides a novel electrocatalyst for the ORR with high performance.