▎ 摘　　要

Due to the pi-pi interaction of graphene (GR) layers, GR sheets tend to aggregate irreversibly to graphite during the application process. In addition, nanoparticles supported on GR layers are easily sandwiched or secluded inside the stacked layers and therefore not efficient exposure for catalysis. To address the irreversible aggregation of GR and increase the utilization efficiency of supported nanoparticles, in this work, porous GR (PGR) was prepared using SiO2 as a template and used as support for the NiCo2O4. The porous structure provided larger surface area and more opportunity for the exposure of supported NiCo2O4. Due to the porous structure of PGR, the NiCo2O4 supported on PGR were not hidden by aggregated GR layers and were highly exposed to target molecules. Compared with NiCo2O4/GR, the electrocatalytic activity of NiCo2O4 supported on PGR is effectively increased accompanied with the high utilization efficiency of NiCo2O4 supported on PGR. By combination of the catalytic properties of highly exposed NiCo2O4 and structural properties of PGR, the NiCo204/PGR is highly active, cheap and selective noble-metal free catalysts for oxygen reduction reaction (ORR) in alkaline solution. In addition, the ORR activity of NiCo2O4/PGR is increased accompanied with the decrease of pore size of PGR. N1CO204/PGR is potential efficient and inexpensive noble metal-free ORR catalysts with good long term stability in alkaline solution. (C) 2015 Elsevier B.V. All rights reserved.