Heterostructure and Oxygen Vacancies Promote NiFe2 O4 /Ni3 S4 toward Oxygen Evolution Reaction and Zn-Air Batteries.

Developing high-performance catalysts for oxygen evolution reaction (OER) is critical for the widespread applications of clean and sustainable energy through electrochemical devices such as zinc-air batteries and (photo)electrochemical water splitting. Constructing heterostructure and oxygen vacancies have demonstrated great promises to boost the OER performance. Herein, we report a facile strategy to fabricate hetero-structured NiFe2 O4 /Ni3 S4 nanorods, where NiFe2 O4 can be derived from Fe-based metal-organic frameworks (MOFs). The NiFe2 O4 /Ni3 S4 catalyst exhibited excellent OER performance, evidenced by an overpotential value of 357 mV at the current density of 20 mA cm-2 , and a small Tafel slope of 87.46 mV dec-1 in 1 M KOH, superior to the benchmark IrO2 catalyst. Moreover, NiFe2 O4 /Ni3 S4 outperformed with regard to long-term durability for OER than IrO2 . Such outstanding OER performance is mainly accounted by the interface between NiFe2 O4 and Ni3 S4 , and the presence of rich oxygen vacancies. When employed as air-cathode in zinc-air batteries, the NiFe2 O4 /Ni3 S4 decorated battery had a high round-trip efficiency of 62.1% at 10 h, and possessed long-term stability of >50 h. This study may pave the way for fabricating non-noble-metal-based cost-effective, efficient and durable electrocatalysts for OER, zinc-air batteries, and beyond.