Beads‐on‐string hierarchical structured electrocatalysts for efficient oxygen reduction reaction

Abstract Rational design of hierarchically structured electrocatalysts is particularly important for electrocatalytic oxygen reduction reaction (ORR). Here, ZIF‐67 crystals are stringed on core–shell Ag@C nanocables using a coordination‐modulated process. Upon pyrolysis, Ag@C strings of Co nanoparticles embedded with three‐dimensional porous carbon with beads‐on‐string hierarchical structures are developed. Due to the advantages of the rich electrochemical active sites of Co‐based “beads” and the efficient electron transfer pathways via Ag@C “strings,” the resultant NH₃–Ag@C@Co–N–C‐700 catalyst shows an improved electrocatalytic activity toward ORR. NH₃–Ag@C@Co–N–C‐700 shows a high onset potential of 0.99 V versus RHE, a high half‐wave potential of 0.88 V versus RHE, and a large limiting current of 5.8 mA cm⁻², which are better than those of commercial Pt/C electrocatalysts. Additionally, the NH₃–Ag@C@Co–N–C‐700 catalyst shows high stability and preeminent methanol tolerance, which makes NH₃–Ag@C@Co–N–C‐700 a promising catalyst for oxygen electrocatalysis in fuel cell applications.