Molten‐Salt‐Assisted Synthesis of 3D Holey N‐Doped Graphene as Bifunctional Electrocatalysts for Rechargeable Zn–Air Batteries

Abstract

AbstractDevelopment of efficient bifunctional oxygen electrocatalysts is urgently needed for high‐performance rechargeable Zn–air batteries. However, sluggish oxygen reduction reaction/oxygen evolution reaction (ORR/OER) kinetics and poor mass transport are two key issues that hinder the performance of Zn–air batteries. Herein, a facile strategy is reported to prepare 3D holey N‐doped graphene (3D HNG) with the aid of molten salts for boosting the performance of ORR/OER‐driven Zn–air batteries. The as‐prepared HNG shows a hierarchical porous framework structure with a 1:1 ratio of pyridinic to graphitic N. Owing to the matched N catalytic active sites and the special pore structure, 3D HNG displays super bifunctional electrocatalytic activity toward both ORR and OER. Specifically, rechargeable Zn–air batteries fabricated with this electrocatalyst show excellent discharge capacity, rechargeability, and round‐trip efficiency. Density functional theory (DFT) computations further reveal that armchair–graphitic N and zigzag–pyridinic N are more favorable for ORR and OER, respectively. By combining these two components, the mixed structure displays the lowest overpotentials of 0.47 and 0.36 V for ORR and OER, respectively, comparable to the theoretical values of Pt and RuO2. This work provides a new strategy for optimizing N‐doped carbon materials for bifunctional oxygen electrocatalysts.