In-site grown carbon nanotubes connecting Fe/Cu-N-C polyhedrons as robust electrocatalysts for Zn-air batteries

Fe-N-C catalysts are considered to be the most promising non-precious metal based catalysts for oxygen reduction reactions (ORRs), but the low active site density and the insufficient electron transport capability have seriously impeded their applications in fuel cells and metal-air batteries. Herein, we demonstrate polyhedral Fe/Cu-N-C particles chained by in-site grown carbon nanotubes (CNTs) serving as robust electrocatalysts for Zn-air battery (ZAB) applications. Benefiting from highly exposed polyhedral active sites and FeCu induced in-site grown CNT channels as well as Fe, Cu bimetallic synergistic optimization of adsorption/desorption energy, the engineered Fe/Cu-N-C electrocatalyst exhibits outstanding oxygen reduction performance. The ultrahigh activity of the Fe/Cu-Nx catalytic centers is attributed to not only the high content of pyridinic and graphitic N, but also the enhanced electron density around Fe atom center. Both primary and rechargeable ZABs are assembled and tested. The results show that the Fe/Cu-N-C based ZABs are far superior to the commercial Pt/C based ZABs regarding peak power density, specific capacity, energy density and cycling stability.