Enhanced ORR activity of cobalt porphyrin co-deposited with transition metal oxides on Au and C electrodes. The ORR threshold data

• The activity of cobalt porphyrin towards ORR was enhanced by metal oxides.
• The CoOx–CoP/Au catalyst showed better activity to ORR than NiOx–CoP/Au.
• The transition metal oxide near the N4–Co center improved the ORR.

We co-deposited cobalt porphyrins (CoP) and transition metal oxides on gold and carbon/graphene electrodes as catalysts for the oxygen reduction reaction (ORR). Porphyrins were adsorbed spontaneously, and the transition metal oxides (CoOx and NiOx) were deposited using spontaneous deposition tactics or an electrochemical deposition method. The electrodes were characterized in acidic media by cyclic voltammetry (CV), by broad-band sum frequency generation (BB-SFG) and – in vacuum – by the Auger electron spectroscopy (AES). The ORR activity data indicate that the activity of cobalt porphyrin towards ORR is enhanced by co-deposited transition metal oxides. The detailed reasons for this behavior are being interrogated.