Wei-Wei Wang

Recently, MXene-based microsupercapacitors (MSCs) prepared by inkjet printing have attracted great attention due to their potential applications in portable and wearable electronics. Although the aqueous MXene inks are more eco-friendly than their organic counterparts, their practical applications seriously suffer from the poor stability of MXene in water. In this work, a high-stability aqueous ink is developed by grafting sodium dodecyl sulfate (SDS) onto the surface of MXene. The SDS molecules firmly adsorb on MXene in a parallel configuration through electrostatic interactions and hydrogen bonding, thereby inhibiting the agglomeration of MXene nanoflakes and protecting the defective sites from water and oxygen. Thus, the dispersion and structural stabilities of the SDS-MXene ink are substantially promoted compared with those of the pristine MXene ink. The lifetime constant of the SDS-MXene ink is estimated to be 157.3 days, while that of the pristine MXene ink is only 22.1 days. Furthermore, the interdigital electrodes are prepared on the flexible polyethylene terephthalate substrates by inkjet printing using a home printer, with a high resolution (150 μm), high conductivity (1091 S/cm), and controllable thicknesses. The assembled MSCs using the SDS-MXene ink shows greatly enhanced electrochemical performance than that of the devices using the pristine MXene ink, with the volume capacitances increasing from 177 F/cm³ to 714.3 F/cm³, which is mainly attributed to expanded ion transport channels, increased active sites, and maintained high conductivity. Besides, the MSCs derived from the ink aged for 60 days still have a similar performance to that of the device from the fresh ink. Finally, the MSCs also show impressive flexibility and an adjustable voltage window. The present work provides a basic formula of a highly stable aqueous MXene ink, which can be further modified to match the manufacturing requirements of different electronic devices such as sensors, batteries, and electric circuits.

Achieving superior tribo-negative performance beyond traditional fluorinated polymers (TFPs) is crucial for advancing triboelectric devices. In this work, we identified an approach to enhance the tribo-negative properties of TFPs via synergistic effects of C-F and C-Cl bonds, based on the significant tribo-differences observed in polyvinylidene fluoride (PVDF) based copolymers. Our findings indicate that the -CTFE unit, particularly its C-Cl bond, significantly lowers the LUMO of the copolymer system, resulting in PVDF-CTFE (PC) exhibiting the strongest tribo-negative properties. By controlling the surface Cl/F ratio via chlorine plasma treatment, it was demonstrated that a higher C-Cl content enhances electron acquisition, whereas a higher C-F content improves charge retention. The synergistic effect optimally balances triboelectric charge capture and losses, enabling PC-Cl to achieve the highest triboelectric charge density (310 µC cm^-2) among PVDF copolymers. Our results will provide a versatile strategy for enhancing a wide range of tribo-negative materials.

Controllable regioselective functionalization of endohedral metallofullerenes (EMFs), exemplified by La@C₈₂, remains elusive owing to the high similarity among surface sites and pronounced metal-cage charge transfer. Here, we propose an external-electric-field-assisted strategy for the Diels-Alder cycloaddition on La@C₈₂, enabling highly active, regioselective, and tunable derivatization. Density functional theory calculations reveal that the applied field not only modulates intrinsic La-cage interactions and even drives La migration, but also, in synergy with the built-in field, tailors intermolecular charge transfer at transition states and reshapes reaction barriers. By establishing a quantitative field-strength-barrier relationship, this work introduces a target-oriented paradigm for EMF functionalization beyond the reach of conventional chemistry.

Chlorination is an effective method for stabilizing fullerenes with pentagon adjacencies, transforming reactive sp ² carbon sites into sp ³ hybridization to release local strain and reorganize orbital and spin distributions. Yet, the immense variety of fullerene isomers and their diverse chlorination sites pose significant challenges for accurate structural prediction. This study introduces a density functional theory (DFT)‐accurate machine learning potential (MLP) for the C‐Cl system, facilitating high‐throughput screening of chlorinated fullerenes. The MLP precisely replicates a range of experimentally identified chlorofullerenes and establishes correlations between parent fullerenes and their chlorinated derivatives in terms of structural features and stability, offering theoretical insights into the formation principles of chlorofullerenes.

Theoretical modeling of the solid‐state photocatalysis is one of the important issues as various useful photocatalysts have been developed to date. In this work, we investigated the mechanism of the alcohol photooxidation on niobium oxide (Nb₂O₅) which was experimentally developed, using the density functional theory (DFT)/time‐dependent (TD)DFT calculations based on the cluster model. The alcohol adsorption and the first hydrogen transfer from hydroxy group to surface occur in the ground state, while the second hydrogen transfer from CH proceeds in the excited states during the photoirradiation of UV or visible light. The spin crossing was identified and the low‐lying triplet states were solved for the reaction pathway. The photoabsorption in the visible light region was characterized as the charge transfer transition from O 2p of alcohol to Nb 4d of the Nb₂O₅ surface. The spin density and the natural population analysis indicated the generation of spin density in the moiety of carbonyl compound and its dissipation to the interface of the surface, which partly explains the electron paramagnetic resonance measurement. It was confirmed that the rate determining step is the desorption of carbonyl compound and water molecule in agreement with the experimental rate equation analysis. The present findings with the theoretical modeling will provide useful information for the further studies of the solid‐state photocatalysis.

We herein report that surface modification of metal halide perovskites using graphene would be beneficial to improving the energy conversion efficiencies of perovskite solar cells. The present first-principles calculations on MAPbI₃ with a single vacancy created by removing either I, Pb or MA show that the I and Pb vacancies near the surface result in the formation of Pb–Pb and I–I dimers, respectively. They are predicted to yield mid-gap levels, and would degrade the energy conversion efficiency of perovskite solar cells through carrier trapping. The present calculations suggest that when the surface of MAPbI₃ is covered with a graphene sheet, the formation of the carrier trapping dimers would be suppressed. The origin of the “healing effect” of graphene on the lattice defect is ascribed to electronic interactions on the surface, which prevent charge localization at the lattice defects beneath the surface.

We introduce a mechanistic study based on a controversial fullerene bottom-up growth model proposed by R. Saito, G. Dresselhaus, and M. S. Dresselhaus. The so-called SDD C₂ addition model has been dismissed as chemically inadmissible but here we prove that it is feasible via successive atomic-carbon-participated addition and migration reactions. Kinetic calculations on the formation of isolated pentagon rule (IPR)-obeying C₇₀ and Y₃N@C₈₀ are carried out by employing the SDD model for the first time. A stepwise mechanism is proposed with a considerably low barrier of ca. 2 eV which is about 3 eV lower than a conventional isomerization-containing fullerene growth pathway.

Although the existence of Stone–Wales (5‐7) defect at graphene edge has been clarified experimentally, theoretical study on the formation mechanism is still imperfect. In particular, the regioselectivity of multistep reactions at edge (self‐reconstruction and growth with foreign carbon feedstock) is essential to understand the kinetic behavior of reactive boundaries but investigations are still lacking. Herein, by using finite‐sized models, multistep reconstructions and carbon dimer additions of a bared zigzag edge are introduced using density functional theory calculations. The zigzag to 5‐7 transformation is proved as a site‐selective process to generate alternating 5‐7 pairs sequentially and the first step with largest barrier is suggested as the rate‐determining step. Conversely, successive C₂ insertions on the active edge are calculated to elucidate the formation of 5‐7 edge during graphene growth. A metastable intermediate with a triple sequentially fused pentagon fragment is proved as the key structure for 5‐7 edge formation.

Binding of Li⁺ to quadrannulene and its influence on buckybowl functionalization are introduced. The concave-trapped Li⁺ acts as a Lewis acid and the rate of Diels–Alder cycloaddition is enhanced 10⁸ times. A sandwiched bowl-Li⁺-bowl structure is stabilized via concave–cation–convex interactions, indicating the promoted role of Li⁺ in buckybowl assembly.