Engineering dual metal single-atom sites with the nitrogen-coordinated nonprecious catalyst for oxygen reduction reaction (ORR) in acidic electrolyte

Abstract An electrocatalyst composed of dual metal single-atom sites attached to nitrogen-doped porous carbon was made in the current study developing a host–guest design. Co single atoms/nitrogen-doped carbon (Co SAs/NC), Fe SAs/NC, and Co-Fe SAs/NC electrocatalysts were successfully synthesized to evaluate their oxygen reduction reaction (ORR reaction activity) in an acidic medium. Co-Fe SAs/NC shown remarkable oxygen reduction reaction (ORR) performances compared to other samples due to the porous structures from their N-doped porous carbon and dual-site of Fe-Zn or Co-Fe. The respective onset potential and the limiting current density values for Co-Fe SAs/NC are 0.86 VRHE and 6.34 mA cm−2 in 0.1 M HClO4. In contrast with commercial 10 wt% Pt/C, the Co-Fe SAs/NC possess a small electrochemical impedance. It is worth noting that 90.31% and 73.24 % of the initial current density of Co-Fe SAs/NC are remained after 15,000 and 40,000 s in durability measurements. Besides, after 40k durability cycles, the Co-Fe SAs/NC was more stable than commercial Pt/C. Therefore, the Co-Fe SAs/NC can be considered an encouraging ORR catalyst to be utilized in fuel cells to address the problems associated with slow ORR kinetics and high durability.