TiN Supported Cobalt and Molybdenum Nitrides as an Efficient Oxygen Reduction Reaction Catalyst in Acid Medium

TiN supported Co-Mo nitride nano particles were synthesized via a modified sol-gel method, and then nitrided under NH 3 atmosphere at 700 °C. The samples obtained were characterized by XRD, XPS, HRTEM and SAED techniques and tested as catalysts for oxygen reduction reactions (ORR) in acid medium. The synergistic effect of the cobalt and molybdenum nitrides on nanosized TiN leads to a good ORR catalytic activity. The onset potential for the Co 1 Mo 1 Nx/TiN-6 catalyst was shifted to a more positive value 0.347 V versus SCE and the reduction peak located at 0.273 V versus SCE (0.401 V of Pt/C at the same condition). The number of electron transfer was tested by a rotating disk electrode which was in concordance with a two-electron mechanism at the potential 0.2 V versus SCE and it increased to four-electron in the negative values of the potential -0.2 V versus SCE. HRTEM showed that the nanoscale Co 2 N and MoN were still highly dispersed on the surface of TiN though heated at high temperature. This work clearly indicates that the oxygen reduction active center of Co-Mo-N/TiN catalyst was the mixture of Co 2 N and MoN.