Manipulating 2D Membrane Interlayer Channels with Accelerated Mass-Transfer Behavior to Boost Solar Desalination.

The scarcity of fresh water necessitates sustainable and efficient water desalination strategies. Solar-driven steam generation (SSG), which employs solar energy for water evaporation, has emerged as a promising approach. Graphene oxide (GO)-based membranes possess advantages like capillary action and Marangoni effect, but their stacking defects and dead zones of flexible flakes hinders efficient water transportation, thus the evaporation rate lag behind unobstructed-porous 3D evaporators. Therefore, fundamental mass-transfer approach for optimizing SSG evaporators offers new horizons. Herein, a universal multi-force-fields-based method is presented to regularize membrane channels, which can mechanically eliminate inherent interlayer stackings and defects. Both characterization and simulation demonstrate the effectiveness of this approach across different scales and explain the intrinsic mechanism of mass-transfer enhancement. When combined with a structurally optimized substrate, the 4Laponite@GO-1 achieves evaporation rate of 2.782 kg m-2 h-1 with 94.48% evaporation efficiency, which is comparable with most 3D evaporators. Moreover, the optimized membrane exhibits excellent cycling stability (10 days) and tolerance to extreme conditions (pH 1-14, salinity 1%-15%), verifies the robust structural stability of regularized channels. This optimization strategy provides simple but efficient way to enhance the SSG performance of GO-based membranes, facilitating their extensive application in sustainable water purification technologies.

Rearrangement of GO nanosheets with inner and outer forces under high-speed spin for supercapacitor.

The self-standing graphene membranes are considered as ideal electrode materials for supercapacitors. However, maintaining highly regularized and uniform graphene membranes with satisfied electrochemical performance is still a challenge. Herein, with the chelation of metal cation and the radial shear force introduced by high-speed spinning, the uniform interlayer channels and shrunken cracks between adjacent nanosheets can be achieved in the metal-intercalated graphene oxide (GO) membranes, thus realizing regularization both in normal and radial direction. With the promotion in electron transfer and electrolyte penetration, the iron cross-linked GO membrane with spin coating for 40 cycles exhibits a high specific capacitance (427 F g-1 at 1 A g-1) and rate capability (42.6% capacitance retention from 1 to 40 A g-1), as well as excellent cyclic capability (90.5% capacitance retention after 20,000 cycles). Particularly, a 21% increasement in capacitance can be achieved after high-speed spinning treatment. Moreover, the spin regularization strategy can be extended to GO membranes cross-linked by various multi-valence metal cations, the electrochemical performance of metal-cation cross-linked GO membrane electrodes after high-speed spinning treatment can also be improved obviously. Therefore, this paper provides a novel method to fabricate highly ordered GO membranes with promising electrochemical performance, which presents an immense potential application in membrane materials applied in energy storage, separation and catalysis.

Oxygen vacancies refilling and potassium ions intercalation of δ-manganese dioxide with high structural stability toward 2.3 V high voltage asymmetric supercapacitors.

Oxygen vacancies occupation and coordination environment modulation of the transition-metal based electrodes are effective strategies to improve the structural stability and electrochemical performance. In this work, the 2-methylimidazole (2-MI) doped manganese dioxide (MnO2) anchored on carbon cloth (CC) is fabricated via a simple method (MI-MnO2-x/CC), where the oxygen defects on/inside the K+ doped δ-MnO2 nanosheets are in-situ created by reductive ethanol/Mn2+ and occupied by 2-MI ligands. With the pre-embedded K+ ions and abundant ligand-refilled defects, the electronic coordination structure, structural stability and electron/ion diffusion efficiency can be effectively enhanced. Therefore, the MI-MnO2-x/CC reveals a remarkable specific capacitance of 721.2 mF cm-2 with excellent cycle durability (capacitance retention of 93.4% after 10,000 cycles) under 1.3 V operation potential window. In addition, an asymmetric supercapacitor assembled by MI-MnO2-x/CC and activated mechanical exfoliated graphene oxide yields a maximum energy density of 57.0 Wh kg-1 and a highest power density of 23.0 kW kg-1 under 2.3 V. This effective oxygen defect stabilization strategy by ligands refilling can be extended to various metal oxide-based electrodes for energy storage and conversion.