Defect Engineering toward Atomic Co–N_x–C in Hierarchical Graphene for Rechargeable Flexible Solid Zn‐Air Batteries

Abstract

Rechargeable flexible solid Zn‐air battery, with a high theoretical energy density of 1086 Wh kg−1, is among the most attractive energy technologies for future flexible and wearable electronics; nevertheless, the practical application is greatly hindered by the sluggish oxygen reduction reaction/oxygen evolution reaction (ORR/OER) kinetics on the air electrode. Precious metal‐free functionalized carbon materials are widely demonstrated as the most promising candidates, while it still lacks effective synthetic methodology to controllably synthesize carbocatalysts with targeted active sites. This work demonstrates the direct utilization of the intrinsic structural defects in nanocarbon to generate atomically dispersed Co–Nx–C active sites via defect engineering. As‐fabricated Co/N/O tri‐doped graphene catalysts with highly active sites and hierarchical porous scaffolds exhibit superior ORR/OER bifunctional activities and impressive applications in rechargeable Zn‐air batteries. Specifically, when integrated into a rechargeable and flexible solid Zn‐air battery, a high open‐circuit voltage of 1.44 V, a stable discharge voltage of 1.19 V, and a high energy efficiency of 63% at 1.0 mA cm−2 are achieved even under bending. The defect engineering strategy provides a new concept and effective methodology for the full utilization of nanocarbon materials with various structural features and further development of advanced energy materials.

A Hydrangea‐Like Superstructure of Open Carbon Cages with Hierarchical Porosity and Highly Active Metal Sites

“…[48][49][50] The electron transfer number of ORR is also determined by measuring LSV curves upon various rotating speeds according to the Koutechy-Levich (K-L) equation. [55] As expected, Zn-air batteries with CoFe5@CC and CoFe20@CC all display a substantial elongated lifetime (>130 h) and a superior cycling stability (400 cycles). The CoFe20@CC exhibits the same slope as that of the Pt/C catalyst ( Figure S43, Supporting Information).…”

Defect electrocatalytic mechanism: concept, topological structure and perspective

“…58 Subsequently, Zhang and co-workers also demonstrated the direct utilization of defects in carbon-based materials to create atomic Co-N x -C coordination structures, which could serve as bifunctional active sites for both ORR and OER. 59 Meanwhile, Zhang et al directly identified the coordination structure of atomic Ni trapped in graphene defects by using probe-corrected TEM, and further revealed that different integrated coordination structures (atomic Ni at various carbon defects) may be the specific active sites for OER and HER, respectively. 60 For commercialization purpose, Liu et al developed a controllable and scalable synthetic strategy of such defective carbons from cheap and earth-abundant biowaste resources (e.g.…”

“…This feature may provide good opportunities to significantly enhance the catalytic activity and catalyst durability. 52,[57][58][59][60][61] The focus on defects on carbon for electrocatalysis is an emerging field, and the simultaneous and subsequent research from other groups is also discussed.…”

N, P-dual doped carbon with trace Co and rich edge sites as highly efficient electrocatalyst for oxygen reduction reaction

“…Their micro-electrochemical system can provide direct evidence to prove that the activity of edge sites was higher than that of the basal plane. Guided by this finding, many researchers try to induce more holes to expose more edge sites or different kinds of defects through various methods [27][28][29][30]. Though metal-free carbon based catalysts have been widely researched, their activities still cannot fully satisfy the demand for commercialization.…”