ORR and OER on Ni‐modified Co3O4(111) Cathodes for Zn‐Air Batteries – A Combined Surface Science and Electrochemical Model Study

The performance of structurally and chemically well-defined Ni-free and Ni-modified single-crystalline Co 3 O 4 (111) thin film electrodes in the oxygen reduction and oxygen evolution reactions (ORR and OER) was investigated in a combined surface science and electrochemistry approach. Pure and Ni-modified Co 3 O 4 (111) film electrodes were prepared and characterized under ultrahigh vacuum (UHV) conditions by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Both Ni decoration, by post-deposition of Ni, and Ni doping, by simultaneous vapor deposition of Ni, Co and O 2 , induce distinct differences in the base CVs in 0.5 M KOH at potentials > 0.7 V compared to Co 3 O 4 (111) electrodes. Also, all oxide film electrodes show a higher overpotential for the ORR, but a lower one for the OER than polycrystalline Pt. Ni modification significantly improves the ORR current densities by increasing the electric conductivity, while the OER onset of ~1.47 V RHE at 0.1 mA cm -2 is almost unchanged.