Ultrafine iron-cobalt nanoparticles embedded in nitrogen-doped porous carbon matrix for oxygen reduction reaction and zinc-air batteries

Abstract

Oxygen reduction reaction (ORR) is a key process in renewable energy conversion and storage technologies, including fuel cells and metal-air batteries. Pt is a highly efficient ORR electrocatalyst, but its large-scale application is severely prohibited by the high cost. In the pursuit of cost-effective electrocatalysts, it is urgent to develop non-noble metal ORR catalysts. Herein, we report a facile strategy for synthesizing an ORR electrocatalyst based on ultrafine bimetallic FeCo nanoparticles (NPs) anchoring on N-doped porous carbon matrix (FeCo-NC). By optimizing the ratio of Fe and Co, the FeCo-NC-1 catalyst exhibits excellent performance for ORR with the half-wave potential of 0.84 V and limiting current density of −5.3 mA cm−2, which is comparable to the commercial Pt/C catalyst. When applied to Zn-air batteries, FeCo-NC-1 catalyst possesses a high open-circuit potential (1.50 V) and large specific capacity (726.2 mA h g−1) with a good long-term stability and methanol-tolerant capability, which are even superior to the commercial Pt/C catalyst. The first-principle calculations indicate the bimetallic FeCo-NC has stronger O2 adsorption than the single metal nitrogen-doped carbon catalysts (Fe-NC and Co-NC), which is the primary reason for the better ORR performance. We believe this work can be helpful for the development of inexpensive and high-efficient ORR electrocatalysts.