Insights into the Surface Oxygen Functional Group-Driven Fast and Stable Sodium Adsorption on Carbon

Engineering the oxygen functional groups (OFGs) is a dynamic strategy to tune the surface chemistry and electrochemical properties of carbon-based materials. In this paper, the species and contents of OFGs on the surface of ordered mesoporous carbon (OMC) and their effects on the sodium storage performance are systematically investigated without the interference of interlayer distance variation, extrinsic defects, other heteroatoms (e.g., N, S), etc. Theoretical calculations performed on various OFGs demonstrate that quinones and carboxylic anhydride groups possess two C═O bonds with stable configurations, good electronic conductivity, and strong sodium adsorption capability, contributing greatly to the Na⁺ storage capacity compared to the carboxylic acid groups. The ex situ techniques disclose the evolution of the OFGs and manifest the stable coordination of Na⁺ with C═O bonds even after long cycles. The optimized OFGs boost the Na⁺ redox reaction kinetics and enhance the surface capacitance contribution, achieving a capacity enhancement of 64.7% compared to the pristine OMC. This work would present implications in rational designing of oxygen-functionalized carbon materials for energy storage fields.