One-Step Electrodeposition of Nanocrystalline Zn x Co 3-x O 4 Films with High Activity and Stability for Electrocatalytic Oxygen Evolution.

The development of highly active, environmentally friendly, and long-term stable oxygen evolving catalysts at low costs is critical for efficient and scalable H2 production from water splitting. Here, we report a new and facile one-step electrodeposition of nanocrystalline spinel-type Znx Co3-x O4 films from an alkaline Zn2+ -Co2+ -tartrate solution. The electrodeposited Znx Co3-x O4 electrode could be directly used as the anode for the water electrolysis without any post treatment. The Znx Co3-x O4 film shows a low and stable overpotential of ∼0.33 V at 10 mA cm-2 (and ∼0.35 V at 20 mA cm-2 ) for over 10 h and a Tafel slope of ∼39 mV dec-1 toward the oxygen evolution reaction (OER) in 1 M NaOH, comparable to the best performance of the nonprecious OER catalysts reported for alkaline media. The enhanced OER activity of Znx Co3-x O4 compared to Co3 O4 could be attributed to the surface structural modification and higher density of the accessible active Co3+ sites induced by the incorporation of Zn2+ . The electrodeposition method in this paper could also be used to synthesize other binary and ternary metal oxide based catalytic electrodes for reactions such as the OER and oxygen reduction reaction (ORR).