Enhanced dual atomic Fe-Ni sites in N-doped carbon for bifunctional oxygen electrocatalysis

Atomically dispersed catalysts with high electrocatalytic performance are emerging as promising electrocatalysts for energy conversion and storage devices. Nevertheless, achieving superior bifunctional catalytic activity with single-atom catalysts toward reactions involving multi-intermediates is still facing great challenges. Herein, dual-atomic Fe-Ni pairs dispersed in hierarchical porous nitrogen-doped carbon (FeNi-HPNC) catalysts were successfully synthesized using a facile mechanochemical strategy. By virtue of the engineered electronic structure of Fe coordinated with Ni, the as-synthesized FeNi-HPNC with atomically dispersed dual-metal active sites and pore-rich structure exhibits remarkable bifunctional activities. A high half-wave potential of 0.868 V for oxygen reduction reaction and a low potential of 1.59 V at 10 mA/cm2 for oxygen evolution reaction have been obtained for FeNi-HPNC, which are superior to the single-atom catalysts of Fe-HPNC and Ni-HPNC, respectively, and are even greater than the precious metal catalysts. Combined experimental and theoretical results have revealed that the enhanced bifunctional catalytic activity of FeNi-HPNC is ascribed to the electronic interaction of Fe-Ni sites, which decreases the adsorption energy of oxygen intermediates during oxygen reduction reaction/oxygen evolution reaction. Furthermore, the practical application of FeNi-HPNC catalysts in Zn-air batteries has been demonstrated; a high peak power density and long-term durability are delivered.