Interplay of hetero-MN4 catalytic sites on graphene for efficient oxygen reduction reaction - Abhishek Kumar; Gonçalves, Josué Martins; Lüder, Johann; Nakamura, Marcelo; Angnes, Lúcio; Bouvet, Marcel; Bertotti, Mauro; Araki, Koiti (Electrochimica Acta, 2022)