In this work, the effects of the addition of transition metals (Mn, Fe, Co, Ni, Cu) on the structure and performance of the doped carbon catalysts M-PANI/C-Mela are investigated. The results show that the doping of various transition metals affected structures and performances of the catalysts significantly. Doping with Fe and Mn leads to a catalyst with a graphene-like structure, and doping with Co, Ni, and Cu leads to a disordered or nanosheet structure. The doping of transition metals can enhance the performance of the catalysts, and their ORR activity follows the order of Fe > Co > Cu > Mn > Ni, which is consistent with the order of their active N contents. We suggest that the various performance enhancements of the transition metals may be the result of the joint effect of the following three aspects: the N content/active N content, metal residue, and the surface area and pore structure, but not the effect of any single factor.

The main challenges to the commercial viability of polymer electrolyte membrane fuel cells are (i) the high cost associated with using large amounts of Pt in fuel cell cathodes to compensate for the sluggish kinetics of the oxygen reduction reaction, (ii) catalyst degradation, and (iii) carbon-support corrosion. To address these obstacles, our group has focused on robust, carbon-free transition metal nitride materials with low Pt content that exhibit tunable physical and catalytic properties. Here, we report on the high performance of a novel catalyst with low Pt content, prepared by placing several layers of Pt atoms on nanoparticles of titanium nickel binary nitride. For the ORR, the catalyst exhibited a more than 400% and 200% increase in mass activity and specific activity, respectively, compared with the commercial Pt/C catalyst. It also showed excellent stability/durability, experiencing only a slight performance loss after 10,000 potential cycles, while TEM results showed its structure had remained intact. The catalyst's outstanding performance may have resulted from the ultrahigh dispersion of Pt (several atomic layers coated on the nitride nanoparticles), and the excellent stability/durability may have been due to the good stability of nitride and synergetic effects between ultrathin Pt layer and the robust TiNiN support.

With a novel two-step approach, we prepared a low-cost, high-performance, binary transition metal nitride (BTMN) catalyst. An ammonia (NH 3 ) complex of Ti and transition metal was prepared in an organic solvent by the reaction of metal ions with ammonium; the complex then was dried in a vacuum oven, followed by nitridation in a tubular furnace in NH 3 flow. The catalyst exhibited excellent activity towards the oxygen reduction reaction (ORR) in an alkaline medium and good ORR activity in an acidic medium.The effects of the doping elements (Fe, Co, and Ni), the doping concentration, and various nitriding temperatures on catalytic performance were intensively investigated. The onset potential of Ti 0.95 Ni 0.5 N catalyst reached 0.83 V, with a limiting diffusion current density of 4 mA cm -2 (at a rotation speed of 1600 rpm) in 0.1 M HClO 4 solution, which is the highest to date among reported TiN-based electrocatalysts in an acidic medium. In 0.1 M KOH solution, the performance of this catalyst was almost comparable to that of commercial JM Pt/C; the diffusion current density reached 5.3 mA cm -2 , and the halfway potential was only 71 mV inferior to that of commercial JM Pt/C. Furthermore, the catalyst showed high stability and only a slight drop in its current density after durability testing. All of these findings make our BTMN catalyst attractive for PEMFCs.