Oxygen Reduction Reaction Performance Of TiN Supported Non-noble Metal Catalyst

As a clean, efficient energy conversion device, proton exchange membrane fuel cell(PEMFC) is easy to operate, fast to response and flexible, which can be widely used in automobiles and household appliances. However, the commercialization of PEMFC is hindered by the high cost and poor stability of the catalysts used, and the catalyst on the cathode for oxygen reduction reaction is of great importance.Nowadays, noble metal catalyst(such as commercial Pt/C) has the most widely used,since the limited storage and high cost, searching for new, low price and high stability ORR catalyst becomes one of the hot pots. In the paper, we would like to prepare catalyst with good ORR performance using non-noble metals.Here, nano titanium nitride, which has high conductivity and good corrosion resistance, serves as the carrier. A modified sol-gel method was used to loading cobal,iron and molybdenum oxides on TiN,following by a temperatured reduction under NH3 atmosphere, then obtain the sample Co-Mo-N/TiN and Fe-Mo-N/TiN and study their ORR performance.The best catalytic performance among the Co-Mo-N/TiN samples was obtained with a raw cobalt and molybdenum ratio of 1:1 and heat treatment temperature of650?. The oxygen reduction reaction on Co-Mo-N/TiN sample has an onset potential of 0.372 V( vs. SCE), and the limited current density of 2.215mA·cm-2. When comes to the sample Co-Mo-N/C and Co-Mo-N/TiN obtained under the same condition, the one with carrier TiN has the better ORR performance. To further study the stability,Co-Mo-N/TiN was treated in 0.5 mo L·L-1 H2SO4 solution for 24 h. The results show that all samples remains good ORR activity, indicating the good stability in acid medium. Here, it was seen by HRTEM that Co-Mo-N was distributed on TiN homogeneous. And combined with XRD and EDS results, the major component of Co-Mo-N/TiN catalyst were Co2 N, Mo N and TiN, since the synergism among them,the Co-Mo-N/TiN exhibited superior ORR performance to Co-Mo-N.As for the sample Fe-Mo-N/TiN synthesized in the same manner, EDS results showed that iron and molybdenum content was really low, XRD and HRTEM results were combined to give the major component of Fe-Mo-N/TiN were Fe8 N, Mo5N6,Fe2O3, Mo O3 and TiN. The best ORR performance was obtained under 700? heat treatment, and the molar ratio was 2:1 while having a loading ratio of 10%. The catalyst had an onset potential of 0.445 V( vs. SCE), and reached up a limited current density of 2.898mA·cm-2. The number of electrons transferred obtained for the oxygen reduction on Fe-Mo-N/TiN was 3.12, indicating that the ORR on it was followed a path of four electrons.