Graphene‐Based Phthalocyanine‐Assembled Synergistic Fe‐Co‐Ni Trimetallic Single‐Atomic Bifunctional Electrocatalysts by Rational Design for Boosting Oxygen Reduction/Evolution Reactions

ABSTRACT Development of high‐efficiency bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is vital for the widespread application of zinc–air batteries (ZABs). However, it still remains a great challenge to avoid the inhomogeneous distribution and aggregation of metal single‐atomic active centers in the construction of bifunctional electrocatalysts with atomically dispersed multimetallic sites because of the common calcination method. Herein, we report a novel catalyst with phthalocyanine‐assembled Fe‐Co‐Ni single‐atomic triple sites dispersed on sulfur‐doped graphene using a simple ultrasonic procedure without calcination, and X‐ray absorption fine structure (XAFS), aberration‐corrected scanning transmission electron microscopy (AC‐STEM), and other detailed characterizations are performed to demonstrate the successful synthesis. The novel catalyst shows extraordinary bifunctional ORR/OER activities with a fairly low potential difference (ΔE = 0.621 V) between the OER overpotential (Ej10 = 315 mV at 10 mA cm−2) and the ORR half‐wave potential (Ehalf‐wave = 0.924 V). Moreover, the above catalyst shows excellent ZAB performance, with an outstanding specific capacity (786 mAh g−1), noteworthy maximum power density (139 mW cm−2), and extraordinary rechargeability (discharged and charged at 5 mA cm−2 for more than 1000 h). Theoretical calculations reveal the vital importance of the preferable synergetic coupling effect between adjacent active sites in the Fe‐Co‐Ni trimetallic single‐atomic sites during the ORR/OER processes. This study provides a new avenue for the investigation of bifunctional electrocatalysts with atomically dispersed trimetallic sites, which is intended for enhancing the ORR/OER performance in ZABs.