Cu single atoms regulating nitrogen active-sites of g-C3N4 for sodium ion storage

Abstract

Nitrogen-rich material of graphitic carbon nitride (g-C3N4) with cost-effectiveness and easy accessibility has been considered as one of the most promising anode materials for sodium ion batteries (SIBs). However, the excessive presence of non-stable nitrogen sites in low crystallinity carbon nitrides would result in significant irreversibility, inadequate ion conductivity and structural instability, thereby limiting its practical application. Herein, a novel low-temperature strategy is proposed to stabilize the g-C3N4 by modulating the nitrogen configuration with single-atoms copper. The formed copper single atoms serving as anchors effectively regulate the coordination environment of nitrogen atoms in carbon nitride, thereby constructing stable nitrogen active sites for Na+ storage and conductive networks for rapid Na+ transport. Therefore, the Cu1.0/NC exhibits superior capacity (350.4 mAh g−1 at 50 mA g−1), exceptional rate performance (252.3 mAh g−1 at 1000 mA g−1), and long-cycle stability (capacity retention rate of 80.3 % after 1000 cycles at 5A g−1). Furthermore, in-situ Raman, ex-situ XANES and XPS technologies jointly reveal that the Cu atoms significantly influence the charge transfer process of Na+ and change the storage mode of sodium through redox effects during the sodiation/desodiation process. This work proves that single-atom engineering is a novel and feasible strategy to optimize the high-performance electrode materials for rechargeable batteries.