Modulating the structure of iron-doped titanium nitride deposited on a nitrogen-doped carbon catalyst for the oxygen reduction reaction in Zn–air batteries

Abstract

High-performance electrocatalysts with cost-effectiveness are the key to advances in the areas of energy conversion and storage. To achieve this, nitrogen doped carbon supported iron-doped titanium nitride nanoparticles (Ti_xFe_1−xN/NC/C catalyst) were prepared and optimized as a cathode catalyst for Zn–air batteries. The optimized Ti_0.95Fe_0.05N/NC/C catalyst display remarkable activity and durability for the ORR, which even surpassed those of Pt/C. The Zn–air battery assembled with the Ti_0.95Fe_0.05N/NC/C air-cathode presents a high maximum power density and possesses a specific capacity comparable to that of Pt/C. The remarkable performance was attributed to the introduction of the Fe dopant into the lattice of TiN, which can promote the graphitization degree of carbon matrices indirectly, optimize the particle size of TiN nanoparticles, and mediate the relative percentage of pyridinic-N and graphitic-N. More importantly, the electronic structure and active sites were modulated, the reaction barrier of the rate-determining step decreased in the ORR process by doping Fe ions, and therefore improves the ORR activity and Zn–air battery performance. This work demonstrates the great potential of the Ti_0.95Fe_0.05N/NC/C catalyst as a substitute for the commercial Pt/C catalyst in energy conversion devices.