One-Step Electrodeposition of Nanocrystalline Zn_xCo_3–xO₄ 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 H 2 production from water splitting. Here, we report a new and facile one-step electrodeposition of nanocrystalline spinel-type Zn x Co 3– x O 4 films from an alkaline Zn 2+ –Co 2+ –tartrate solution. The electrodeposited Zn x Co 3– x O 4 electrode could be directly used as the anode for the water electrolysis without any post treatment. The Zn x Co 3– x O 4 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 Zn x Co 3– x O 4 compared to Co 3 O 4 could be attributed to the surface structural modification and higher density of the accessible active Co 3+ sites induced by the incorporation of Zn 2+ . 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).