Coordination modulation of single-atom Zn sites to boost oxygen reduction performance

Abstract

Rational design of highly active and durable oxygen reduction reaction (ORR) electrocatalysts to replace expensive platinum-based catalysts and significantly improve the electrocatalytic performance of rechargeable zinc–air batteries (ZABs) has become a key goal in the field of energy storage technology. Here, we modulate the coordination structure of single-atom Zn sites on an N-doped graphene matrix using a rapid heating method to enhance the ORR performance. In 0.1 M KOH solution, the half-wave potential (E_1/2) of Zn-NG-800 is 0.84 V, and it exhibits good anti-Fenton reaction performance. The zinc-air battery assembled with Zn-NG-800 as the cathode material has an open-circuit voltage (OCV) of up to 1.50 V and exhibits a maximum power density of 158 mW cm⁻² and excellent output stability for over 200 h. Theoretical calculations show that the Zn-N₄G configuration exhibits a lower ORR barrier than Zn-N₂G and Zn-N₃G structures. The rate-determining step on Zn-N₂G and Zn-N₃G is *O → *OH, and both show a reaction barrier significantly greater than 1.00 eV. In contrast, the rate-determining step on Zn-N₄G is *OH → * + H₂O, and the energy barrier is only 0.68 eV, thus exhibiting better catalytic performance.