Changlong Sun

Gallium Nitride Crystals: Novel Supercapacitor Electrode Materials.

A type of single-crystal gallium nitride mesoporous membrane is fabricated and its supercapacitor properties are demonstrated for the first time. The supercapacitors exhibit high-rate capability, stable cycling life at high rates, and ultrahigh power density. This study may expand the range of crystals as high-performance electrode materials in the field of energy storage.

Self‐Supporting GaN Nanowires/Graphite Paper: Novel High‐Performance Flexible Supercapacitor Electrodes

Flexible supercapacitors have attracted great interest as energy storage devices because of their promise in applications such as wearable and smart electronic devices. Herein, a novel flexible supercapacitor electrode based on gallium nitride nanowire (GaN NW)/graphite paper (GP) nanocomposites is reported. The outstanding electrical conductivities of the GaN NW (6.36 × 102 S m-1 ) and GP (7.5 × 104 S m-1 ) deliver a synergistically enhanced electrochemical performance that cannot be achieved by either of the components alone. The composite electrode exhibits excellent specific capacitance (237 mF cm-2 at 0.1 mA cm-2 ) and outstanding cycling performance (98% capacitance retention after 10 000 cycles). The flexible symmetric supercapacitor also manifests high energy and power densities (0.30 mW h cm-3 and 1000 mW cm-3 ). These findings demonstrate that the GaN/GP composite electrode has significant potential as a candidate for the flexible energy storage devices.

One-step exfoliation and fluorination of g-C3N4 nanosheets with enhanced photocatalytic activities

Exfoliation and functionalisation of two-dimensional (2D) nanosheets are highly desired for the improvement of their chemical and physical properties. Herein, we propose a novel and efficient method for the preparation of fluorinated graphite carbon nitride (F-C3N4) nanosheets with enhanced photocatalytic activities. A one-step route was used to exfoliate and fluorinate the graphite carbon nitride (g-C3N4) nanosheets by using g-C3N4 powder combined with ammonium fluoride (NH4F). Through related instrumental characterisation, we confirmed that few-layered F-C3N4 nanosheets were produced successfully. Meanwhile, the enhanced hydrogen evolution rate of F-C3N4 nanosheets (477.6 µmol h−1 g−1) also confirmed the feasibility of this exfoliation method. This report not only opens up new possibilities for the rational design of metal-free F-C3N4 nanosheets with stable photochemical applications but also provides a potential method for producing functionalised 2D materials.

One-step fabrication of porous GaN crystal membrane and its application in energy storage

Single-crystal gallium nitride (GaN) membranes have great potential for a variety of applications. However, fabrication of single-crystalline GaN membranes remains a challenge owing to its chemical inertness and mechanical hardness. This study prepares large-area, free-standing, and single-crystalline porous GaN membranes using a one-step high-temperature annealing technique for the first time. A promising separation model is proposed through a comprehensive study that combines thermodynamic theories analysis and experiments. Porous GaN crystal membrane is processed into supercapacitors, which exhibit stable cycling life, high-rate capability, and ultrahigh power density, to complete proof-of-concept demonstration of new energy storage application. Our results contribute to the study of GaN crystal membranes into a new stage related to the elelctrochemical energy storage application.

Metal-free Ternary BCN Nanosheets with Synergetic Effect of Band Gap Engineering and Magnetic Properties

Introducing the synergy effect of magnetic properties and band gap engineering is highly desired for two-dimensional (2D) nanosheets. Here, we prepare metal-free ternary 2D carbon (C) doped boron nitride (BN) nanosheets (BCN) with band gap engineering and magnetic properties by a synergetic way. The substitutional occupation of C atoms, as revealed by X-ray absorption spectrum, in BCN nanosheets induces tunable band gap reduction (5.5 eV to 2.6 eV) and intensive intrinsic ferromagnetism at room temperature. First-principle calculations also reveal that substituted C atoms in BCN nanosheets can broaden the light adsorption region and reduce the optical band gap, and ferromagnetic ordering is energetically more favorable than antiferromagnetic. This design opens up new possibility for synergetic manipulation of exchange interactions and band gap engineering in 2D nanostructures.

Graphene-Oxide-Assisted Synthesis of GaN Nanosheets as a New Anode Material for Lithium-Ion Battery

As the most-studied III-nitride, theoretical researches have predicted the presence of gallium nitride (GaN) nanosheets (NSs). Herein, a facile synthesis approach is reported to prepare GaN NSs using graphene oxide (GO) as sacrificial template. As a new anode material of Li-ion battery (LIBs), GaN NSs anodes deliver the reversible discharge capacity above 600 mA h g-1 at 1.0 A g-1 after 1000 cycles, and excellent rate performance at current rates from 0.1 to 10 A g-1. These results not only extend the family of 2D materials but also facilitate their use in energy storage and other applications.

Stable and Reversible Lithium Storage with High Pseudocapacitance in GaN Nanowires

In this work, gallium nitride (GaN) nanowires (NWs) were synthesized by chemical vapor deposition (CVD) process. The hybrid electrode showed the capacity up to 486 mAh g-1 after 400 cycles at 0.1 A g-1. Even at 10 A g-1, the reversible capacity can stabilize at 75 mAh g-1 (after 1000 cycles). Pseudocapacitive capacity was defined by kinetics analysis. The dynamics analysis and electrochemical reaction mechanism of GaN with Li+ was also analyzed by ex situ XRD, HRTEM, and XPS results. These results not only cast new light on pseudocapacitance enhanced high-rate energy storage devices by self-assembled nanoengineering but also extend the application range of traditional binary III/V semiconductors.