Exploring the Inner- and Outer-Sphere Mechanistic Pathways of ORR on M–N–Cs with Pyrrolic MN<sub>4</sub> Motifs
Jian Liang Low, Christina Roth, Beate Paulus
Abstract
High Resolution Image Download MS PowerPoint Slide Metal- and nitrogen-doped carbon materials (M–N–Cs) have emerged as promising alternatives to costly platinum-group metals (PGMs) for the oxygen reduction reaction (ORR) in renewable energy applications. Notably, there is increasing experimental and theoretical evidence supporting pyrrolic MN 4 coordination over pyridinic MN 4 in these materials, which aligns closer to the MN 4 geometries found in nature. This study utilizes density functional theory (DFT) to elucidate the ability of each metal to catalyze various ORR mechanisms at the pyrrolic MN 4 sites. Among the M–N–Cs of first–row transition metals, pyrrolic CrN 4 and FeN 4 exhibit exceptional 4e-ORR activity, promoting both inner- and outer-sphere mechanisms and H 2 O 2 dissociation. Pyrrolic CoN 4 is also promising for 2e-ORR catalysis due to its effective outer-sphere electron-transfer capabilities. These findings offer valuable insights for designing sustainable electrocatalysts to exploit the full potential of renewable energy sources, advancing the path toward carbon neutrality.