Nitrogen-doped graphene-based catalyst with metal-reduced organic framework: Chemical analysis and structure control

Here we report an advanced nitrogen-doped graphene-based catalyst with metal-reduced organic framework structure (N-G/MOF) prepared by functionalizing ZIF-8 and nitrogen-functionalized graphene oxide using the nanoscale high energy wet ball milling method. The chemical structure control of N-G/MOF was studied by characterizing the variation of the chemical structure of synthesized samples throughout targeted grinding speeds. The results proved that the chemical interaction between ZIF-8 and N-G caused the reduction of nitrogen, oxygen and zinc atoms, and the variation of chemical bonding composition in N-G/MOF. The reduction rate of zinc was gradually increased with the increasing grinding speed and reached 82% of zinc loss at 650 RPM. The characterization of carbon and nitrogen bonding composition confirmed that the reduction of nitrogen, oxygen and zinc atoms was caused by the decomposition of C-N-Zn heteroatom contents in ZIF-8 and the O-containing functional groups in N-G which were influenced by the grinding speed. The decomposition of ZIF-8 not only affected the framework and the pore structure but also modified the chemical structure and the surface distribution of C-N-containing functional groups-constituted active sites. The variation of physical and chemical properties enhanced the electrochemical performance of N-G/MOF and made it comparable to the 10 wt% Pt/C catalyst.