Sheet-like units of ferrocene-based coordination compounds for oxygen evolution

Metal-organic frameworks represent an emerging class of effective pre-electrocatalysts with low cost and high activity for oxygen evolution, which is a critical process involved in water splitting and metal-air batteries. In this study, a new electrode with ferrocene-based coordination compounds supported by nickel foam was designed and prepared, in which the coordination compounds are assembled by cobalt chloride and 1, 1'-ferrocenedicarboxylic acid. The as-obtained pre-catalytic electrode shows remarkable electrocatalytic activity and stability towards oxygen evolution. In 1 M KOH, the electrode can provide a current density of 50 mA cm−2 at an overpotential of 268 mV with Tafel slope of 109 mV dec−1. During the catalytic process, the metal-organic framework surface shows an obvious phase evolution behavior. The synergetic effect between Co and Fe sites, and the unique microstructure of the in situ derived active species are believed to be responsible for the excellent electrocatalytic performance. The catalytic electrode was also investigated as a cathode in a Zn-air battery, which presents an energy density of 572 mW h gZn−1, a peak power density of 60 mW cm−2, and an excellent cyclability of over 50 h. This work presents a new type pre-catalytic electrode for oxygen evolution and would provide some hints for the development of advanced catalytic electrodes.