Yizhou Zhang

Template-Assisted Synthesis of Nickel Sulfide Nanowires: Tuning the Compositions for Supercapacitors with Improved Electrochemical Stability

Ni nanowires were first synthesized via a chemical method without surfactants or a magnetic field. A series of nickel sulfide nanowires (Ni3S2-Ni, Ni3S2-NiS-Ni, and Ni3S2-NiS) have been successfully prepared by a controlled sacrificial template route based on the conductive Ni nanowire template. Electrochemical characterizations indicate that Ni3S2-NiS nanowires present superior redox reactivity with a high specific capacitance of 1077.3 F g(-1) at 5 A g(-1). Besides, its specific capacitance can remain about 76.3% after 10u202f000 cycles at 20 A g(-1). On the contrary, the nickel-preserving sulfide nanowires (Ni3S2-Ni and Ni3S2-NiS-Ni) deliver enhanced cycling stability as 100% of the initial specific capacitance of Ni3S2-Ni is retained after 10u202f000 cycles. The outstanding electrochemical stability can be attributed to the interaction between nickel sulfides and the conductive nickel nanowires.

Facile one-pot synthesis of NiCo2O4 hollow spheres with controllable number of shells for high-performance supercapacitors

In this work, single- and double-shelled NiCo2O4 hollow spheres have been synthesized in situ by a one-pot solvothermal method assisted by xylose, followed by heat treatment. Employed as supercapacitor electrode materials, the double-shelled NiCo2O4 hollow spheres exhibit a remarkable specific capacitance (1,204.4 F·g−1 at a current density of 2.0 A·g−1) and excellent cycling stability (103.6% retention after 10,000 cycles at a current density of 10 A·g−1). Such outstanding electrochemical performance can be attributed to their unique internal morphology, which provides a higher surface area with a larger number of active sites available to interact with the electrolyte. The versatility of this method was demonstrated by applying it to other binary metal oxide materials, such as ZnCo2O4, ZnMn2O4, and CoMn2O4. The present study thus illustrates a simple and general strategy for the preparation of binary transition metal oxide hollow spheres with a controllable number of shells. This approach shows great promise for the development of next-generation high-performance electrochemical materials.

Stretchable Ti3C2Tx MXene/Carbon Nanotube Composite Based Strain Sensor with Ultrahigh Sensitivity and Tunable Sensing Range

It remains challenging to fabricate strain-sensing materials and exquisite geometric constructions for integrating extraordinary sensitivity, low strain detectability, high stretchability, tunable sensing range, and thin device dimensions into a single type of strain sensor. A percolation network based on Ti3C2Tx MXene/carbon nanotube (CNT) composites was rationally designed and fabricated into versatile strain sensors. This weaving architecture with excellent electric properties combined the sensitive two-dimensional (2D) Ti3C2Tx MXene nanostacks with conductive and stretchable one-dimensional (1D) CNT crossing. The resulting strain sensor can be used to detect both tiny and large deformations with an ultralow detection limit of 0.1% strain, high stretchability (up to 130%), high sensitivity (gauge factor up to 772.6), tunable sensing range (30% to 130% strain), thin device dimensions (<2 μm), and excellent reliability and stability (>5000 cycles). The versatile and scalable Ti3C2Tx MXene/CNT strain sensors provide a promising route to future wearable artificial intelligence with comprehensive tracking ability of real-time and in situ physiological signals for health and sporting applications.

Graphene as an intermediary for enhancing the electron transfer rate: A free-standing Ni 3 S 2 @graphene@Co 9 S 8 electrocatalytic electrode for oxygen evolution reaction

A highly active and stable oxygen evolution reaction (OER) electrocatalyst is critical for hydrogen production from water splitting. Herein, three-dimensional Ni3S2@graphene@Co92S8 (Ni3S2@G@Co9S8), a sandwich-structured OER electrocatalyst, was grown in situ on nickel foam; it afforded an enhanced catalytic performance when highly conductive graphene is introduced as an intermediary for enhancing the electron transfer rate and stability. Serving as a free-standing electrocatalytic electrode, Ni3S2@G@Co9S8 presents excellent electrocatalytic activities for OER: A low onset overpotential (2 mA·cm−2 at 174 mV), large anode current density (10 mA·cm−2 at an overpotential of 210 mV), low Tafel slope (66 mV·dec−1), and predominant durability of over 96 h (releasing a current density of ∼14 mA·cm−2 with a low and constant overpotential of 215 mV) in a 1 M KOH solution. This work provides a promising, cost-efficient electrocatalyst and sheds new light on improving the electrochemical performance of composites through enhancing the electron transfer rate and stability by introducing graphene as an intermediary.

Fiber-based all-solid-state asymmetric supercapacitors based on Co3O4@MnO2 core/shell nanowire arrays

With the rapid development of portable and wearable electronics, fiber-based supercapacitors as one type of flexible and lightweight energy storage devices have attracted intensive attention. However, most of the reported fiber-based supercapacitors are based on a symmetric device configuration, whose narrow operating voltage window and low energy densities as well as the poor electrochemical performance hinder the practical applications of fiber-based supercapacitors. In this report, we developed a fiber-based flexible all-solid-state asymmetric supercapacitor, using nickel wire/Co3O4@MnO2 nanowire arrays and carbon fibers/graphene as the two electrodes. The fiber-based all-solid-state asymmetric supercapacitor exhibited remarkable electrochemical performance with high capacitance (13.9 mF cm−2 at 0.1 mA cm−2) and high cycling stability (82% retention, even after 1000 cycles at 0.6 mA cm−2). The obtained fiber-based supercapacitor is a promising power source candidate for flexible, portable and wearable electronics.

S-Doped TiSe2 Nanoplates/Fe3O4 Nanoparticles Heterostructure

2D Sulfur-doped TiSe2 /Fe3 O4 (named as S-TiSe2 /Fe3 O4 ) heterostructures are synthesized successfully based on a facile oil phase process. The Fe3 O4 nanoparticles, with an average size of 8 nm, grow uniformly on the surface of S-doped TiSe2 (named as S-TiSe2 ) nanoplates (300 nm in diameter and 15 nm in thickness). These heterostructures combine the advantages of both S-TiSe2 with good electrical conductivity and Fe3 O4 with high theoretical Li storage capacity. As demonstrated potential applications for energy storage, the S-TiSe2 /Fe3 O4 heterostructures possess high reversible capacities (707.4 mAh g-1 at 0.1 A g-1 during the 100th cycle), excellent cycling stability (432.3 mAh g-1 after 200 cycles at 5 A g-1 ), and good rate capability (e.g., 301.7 mAh g-1 at 20 A g-1 ) in lithium-ion batteries. As for sodium-ion batteries, the S-TiSe2 /Fe3 O4 heterostructures also maintain reversible capacities of 402.3 mAh g-1 at 0.1 A g-1 after 100 cycles, and a high rate capacity of 203.3 mAh g-1 at 4 A g-1 .

Fe2O3/SnSSe Hexagonal Nanoplates as Lithium-Ion Batteries Anode

Novel two-dimensional (2D) Fe2O3/SnSSe hexagonal nanoplates were prepared from hot-inject process in oil phase. The resulted hybrid manifests a typical 2D hexagonal nanoplate morphology covered with thin carbon layer. Serving as anode material of lithium-ion battery (LIB), the Fe2O3/SnSSe hybrid delivers an outstanding capacity of 919 mAh g-1 at 100 mA g-1 and a discharge capacity of 293 mAh g-1 after 300 cycles at the current density of 5 A g-1. Compared with pristine SnSSe nanoplates, the Fe2O3/SnSSe hybrid exhibits both higher capacity and better stability. The enhanced performance is mainly attributed to the 2D substrate together with the synergistic effects offered by the integration of SnSSe with Fe2O3. The 2D Fe2O3/SnSSe hybrid can afford highly accessible sites and short ion diffusion length, which facilitate the ion accessibility and improves the charge transport. The novel structure and high performance demonstrated here afford a new way for structural design and the synthesis of chalcogenides as LIB anodes.