Pushing Theoretical Potassium Storage Limits of MXenes through Introducing New Carbon Active Sites.

Surface-driven capacitive storage enhances rate performance and cyclability, thereby improving the efficacy of high-power electrode materials and fast-charging batteries. Conventional defect engineering, widely-employed capacitive storage optimization strategy, primarily focuses on the influence of defects themselves on capacitive behaviors. However, the role of local environment surrounding defects, which significantly affects surface properties, remains largely unexplored for lack of suitable material platform and has long been neglected. As proof-of-concept, typical Ti3C2Tx MXenes are chosen as model materials owing to metallic conductivity and tunable surface properties, satisfying the requirements for capacitive-type electrodes. Using density functional theory (DFT) calculations, the potential of MXenes with modulated local atomic environment is anticipated and introducing new carbon sites found near pores can activate electrochemically inert surface, attaining record theoretical potassium storage capacities of MXenes (291 mAh g-1). This supposition is realized through atomic tailoring via chemical scissor within sublayers, exposing new sp3-hybridized carbon active sites. The resulting MXenes demonstrate unprecedented rate performance and cycling stability. Notably, MXenes with higher carbon exposure exhibit a record-breaking capacity over 200 mAh g-1 and sustain a capacity retention higher than 80% after 20 months. These findings underscore the effectiveness of regulating defects' neighboring environment and illuminate future high-performance electrode design.

Atomic Insights into the Relationship between Molecular Structure and Dispersion Performance of Phenyl Polymer on Graphene Oxide.

The adsorption of organic polymers onto the surface of graphene oxide is known to improve its dispersibility in cement-based materials. However, the mechanism of this improvement at the atomic level is not yet fully understood. In this study, we employ a combination of DFT static calculation and umbrella sampling to explore the reactivity of polymers and investigate the effects of varying amounts of phenyl groups on their adsorption capacity on the surface of graphene oxide. Quantitative analysis is utilized to study the structural reconstruction and charge transfer caused by polymers from multiple perspectives. The interfacial reaction between the polymer and graphene oxide surface is further clarified, indicating that the adsorption process is promoted by hydrogen bond interactions and π-π stacking effects. This study sheds light on the adsorption mechanism of polymer-graphene oxide systems and has important implications for the design of more effective graphene oxide dispersants at the atomic level.