Textured Asymmetric Membrane Electrode Assemblies of Piezoelectric Phosphorene and Ti3C2Tx MXene Heterostructures for Enhanced Electrochemical Stability and Kinetics in LIBs

Controllable preparation of carbon coating Ge nanospheres with a cubic hollow structure for high-performance lithium ion batteries

Germanium based nanomaterials are very promising as the anodes for the lithium ion batteries since their large specific capacity, excellent lithium diffusivity and high conductivity. However, their controllable preparation is still very difficult to achieve. Herein, we facilely prepare a unique carbon coating Ge nanospheres with a cubic hollow structure (Ge@C) via a hydrothermal synthesis and subsequent pyrolysis using low-cost GeO2 as precursors. The hollow Ge@C nanostructure not only provides abundant interior space to alleviate the huge volumetric expansion of Ge upon lithiation, but also facilitates the transmission of lithium ions and electrons. Moreover, experiment analyses and density functional theory (DFT) calculations unveil the excellent lithium adsorption ability, high exchange current density, low activation energy for lithium diffusion of the hollow Ge@C electrode, thus exhibiting significant lithium storage advantages with a large charge capacity (1483 mAh/g under 200 mA g-1), distinguished rate ability (710 mAh/g under 8000 mA g-1) as well as long-term cycling stability (1130 mAh/g after 900 cycles under 1000 mA g-1). Therefore, this work offers new paths for controllable synthesis and fabrication of high-performance Ge based lithium storage nanomaterials.

Boosting Zn-Ion Storage Behavior of Pre-Intercalated MXene with Black Phosphorus toward Self-Powered Systems

MXene-based Zn-ion capacitors (ZICs) with adsorption-type and battery-type electrodes demonstrate high energy storage and anti-self-discharge capabilities, potentially being paired with triboelectric nanogenerators (TENGs) to construct self-powered systems. Nevertheless, inadequate interlayer spacing, deficient active sites, and compact self-restacking of MXene flakes pose hurdles for MXene-based ZICs, limiting their applications. Herein, black phosphorus (BP)-Zn-MXene hybrid is formulated for MXene-based ZIC via a two-step molecular engineering strategy of Zn-ion pre-intercalation and BP nanosheet assembly. Zn ions as intercalators induce cross-linking of MXene flakes with expandable interlayer spacing to serve as scaffolds for BP nanosheets, thereby providing sufficient accessible active sites and efficient migration routes for enhanced Zn-ion storage. The density functional theory calculations affirm that zinc adsorption and diffusion kinetics are significantly improved in the hybrid. A wearable ZIC with the hybrid delivers a competitive areal energy of 426.3 µWh cm-2 and ultra-low self-discharge rate of 7.0 mV h-1, achieving remarkable electrochemical matching with TENGs in terms of low energy loss, matched capacity, and fast Zn-ion storage. The resultant self-powered system efficiently collects and stores energy from human motion to power microelectronics. This work advances the Zn-ion storage of MXene-based ZICs and their synergy with TENG in self-powered systems.

Construction of Monolayer Ti3C2Tx MXene on Nickel Foam under High Electrostatic Fields for High-Performance Supercapacitors

Ti3C2Tx MXene, as a common two-dimensional material, has a wide range of applications in electrochemical energy storage. However, the surface forces of few-layer or monolayer Ti3C2Tx MXene lead to easy agglomeration, which hinders the demonstration of its performance due to the characteristics of layered materials. Herein, we report a facile method for preparing monolayer Ti3C2Tx MXene on nickel foam to achieve a self-supporting structure for supercapacitor electrodes under high electrostatic fields. Moreover, the specific capacitance varies with the deposition of different-concentration monolayer Ti3C2Tx MXene on nickel foam. As a result, Ti3C2Tx/NF has a high specific capacitance of 319 mF cm-2 at 2 mA cm-2 and an excellent long-term cycling stability of 94.4% after 7000 cycles. It was observed that the areal specific capacitance increases, whereas the mass specific capacitance decreases with the increasing loading mass. Attributable to the effect of the high electrostatic field, the self-supporting structure of the Ti3C2Tx/NF becomes denser as the concentration of the monolayer Ti3C2Tx MXene ink increases, ultimately affecting its electrochemical performance. This work provides a simple way to overcome the agglomeration problem of few-layer or monolayer MXene, then form a self-supporting electrode exhibiting excellent electrochemical performance.

Recent advances in ambient-stable black phosphorus materials for artificial catalytic nitrogen cycle in environment and energy

Nitrogen cycle is crucial for the Earth's ecosystem and human-nature coexistence. However, excessive fertilizer use and industrial contamination disrupt this balance. Semiconductor-based artificial nitrogen cycle strategies are being actively researched to address this issue. Black phosphorus (BP) exhibits remarkable performance and significant potential in this area due to its unique physical and chemical properties. Nevertheless, its practical application is hindered by ambient instability. This review covers the synthesis methods of BP materials, analyzes their instability factors under environmental conditions, discusses stability improvement strategies, and provides an overview of the applications of ambient-stable BP materials in nitrogen cycle, including N2 fixation, NO3- reduction, NOx removal and nitrides sensing. The review concludes by summarizing the challenges and prospects of BP materials in the nitrogen cycle, offering valuable guidance to researchers.