An Efficient Bifunctional Electrocatalyst for a Zinc-Air Battery Derived from Fe/N/C and Bimetallic Metal-Organic Framework Composites.

Efficient bifunctional electrocatalysts with desirable oxygen activities are closely related to practical applications of renewable energy systems including metal-air batteries, fuel cells, and water splitting. Here a composite material derived from a combination of bimetallic zeolitic imidazolate frameworks (denoted as BMZIFs) and Fe/N/C framework was reported as an efficient bifunctional catalyst. Although BMZIF or Fe/N/C alone exhibits undesirable oxygen reaction activity, a combination of these materials shows unprecedented ORR (half-wave potential of 0.85 V as well as comparatively superior OER activities (potential@10 mA cm-2 of 1.64 V), outperforming not only a commercial Pt/C electrocatalyst but also most reported bifunctional electrocatalysts. We then tested its practical application in Zn-air batteries. The primary batteries exhibit a high peak power density of 235 mW cm-2, and the batteries are able to be operated smoothly for 100 cycles at a curent density of 10 mA cm-2. The unprecedented catalytic activity can be attritued to chemical coupling effects between Fe/N/C and BMZIF and will aid the development of highly active electrocatalysts and applications for electrochemical energy devices.