Structural and surface characterization of catalystsA family of carbon-supported TMNs was prepared via a nitridation reaction with ammonia, as shown in Fig. 1A. The introduction of a carbon support promotes dispersion of TMNs and hence maximizes nitride utilization. The crystal structures of the as-synthesized MxN/C were first investigated with powder x-ray diffraction (XRD). The XRD patterns of TiN/C, VN/C, and CrN/C displayed the same characteristic spectral patterns, typical of the NaCl type face-centered cubic (fcc) structure (Fig. 1B and fig. S1, A to C), in which the metal atoms adopt an fcc arrangement, and the nitrogen atoms are located at the octahedral sites with a stoichiometric ratio of 1:1, as can be visualized from the crystal model (Fig. 1B). In contrast, manganese nitride is known to form multiple phases with different nitrogen contents (40–42). Among them, θ-MnN…
Nonprecious transition metal nitrides as efficient oxygen reduction electrocatalysts for alkaline fuel cells
