Xue-Feng Lu

Hierarchical NiCo2O4 nanosheets@hollow microrod arrays for high-performance asymmetric supercapacitors

Novel hierarchical NiCo2O4 nanosheets@hollow microrod arrays (NSs@HMRAs) are fabricated by a simple and environmental friendly template-assisted electrodeposition followed by thermal annealing. Due to their unique nanostructures, the NiCo2O4 NSs@HMRAs, as electrodes, exhibited a high specific capacitance (Csp) (678 F g−1 at 6 A g−1) and outstanding cycle stability (Csp retention of 96.06% after 1500 cycles). The desirable superior capacitive performance of the NiCo2O4 NSs@HMRAs can be attributed to the large specific surface area, fast ion diffusion, and perfect charge transmission in the hierarchical NSs@HMRAs. The asymmetric supercapacitor (ASC) based on the NiCo2O4 NSs@HMRAs as a positive electrode and active carbon (AC) as a negative electrode was assembled and it exhibited a Csp of 70.04 F g−1 at 5 mV s−1 and a high energy density of 15.42 W h kg−1. Moreover, the NiCo2O4 NSs@HMRAs//AC ASC has an outstanding cycle stability (almost no Csp loss after 2500 cycles), making it promising as one of the most attractive candidates for electrochemical energy storage.

α-Fe2O3@PANI Core–Shell Nanowire Arrays as Negative Electrodes for Asymmetric Supercapacitors

Highly ordered three-dimensional α-Fe2O3@PANI core-shell nanowire arrays with enhanced specific areal capacity and rate performance are fabricated by a simple and cost-effective electrodeposition method. The α-Fe2O3@PANI core-shell nanowire arrays provide a large reaction surface area, fast ion and electron transfer, and good structure stability, which all are beneficial for improving the electrochemical performance. Here, high-performance asymmetric supercapacitors (ASCs) are designed using α-Fe2O3@PANI core-shell nanowire arrays as anode and PANI nanorods grown on carbon cloth as cathode, and they display a high volumetric capacitance of 2.02 mF/cm3 based on the volume of device, a high energy density of 0.35 mWh/cm3 at a power density of 120.51 mW/cm3, and very good cycling stability with capacitance retention of 95.77% after 10,000 cycles. These findings will promote the application of α-Fe2O3@PANI core-shell nanowire arrays as advanced negative electrodes for ASCs.

Palladium–Cobalt Nanotube Arrays Supported on Carbon Fiber Cloth as High‐Performance Flexible Electrocatalysts for Ethanol Oxidation

PdCo nanotube arrays (NTAs) supported on carbon fiber cloth (CFC) (PdCo NTAs/CFC) are presented as high-performance flexible electrocatalysts for ethanol oxidation. The fabricated flexible PdCo NTAs/CFC exhibits significantly improved electrocatalytic activity and durability compared with Pd NTAs/CFC and commercial Pd/C catalysts. Most importantly, the PdCo NTAs/CFC shows excellent flexibility and the high electrocatalytic performance remains almost constant under the different distorted states, such as normal, bending, and twisting states. This work shows the first example of Pd-based alloy NTAs supported on CFC as high-performance flexible electrocatalysts for ethanol oxidation.

Amorphous Cobalt Hydroxide with Superior Pseudocapacitive Performance

Cobalt hydroxide (Co(OH)2) has received extensive attention for its exceptional splendid electrical properties as a promising supercapacitor electrode material. Co(OH)2 study so far prefers to crystal instead of amorphous, in spite of amorphous impressive electrochemical properties including the ability to improve the electrochemical efficiency based on the disorder structure. The amorphous Co(OH)2 nanostructures with excellent electrochemical behaviors were successfully synthesized by a simple and green electrochemistry. Our as-prepared Co(OH)2 electrode exhibited ultrahigh capacitance of 1094 F g(-1) and super long cycle life of 95% retention over 8000 cycle numbers at a nominal 100 mV s(-1) scan rate. The united pseudo-capacitive performances of the amorphous Co(OH)2 nanostructures in electrochemical capacitors are totally comparable to those of the crystalline Co(OH)2 nanomaterials. These findings actually open a door to applications of amorphous nanomaterials in the field of energy storage as superior electrochemical pseudocapacitors materials.

Asymmetric Paper Supercapacitor Based on Amorphous Porous Mn3O4 Negative Electrode and Ni(OH)2 Positive Electrode: A Novel and High-Performance Flexible Electrochemical Energy Storage Device

Here we synthesize novel asymmetric all-solid-state paper supercapacitors (APSCs) based on amorphous porous Mn3O4 grown on conducting paper (NGP) (Mn3O4/NGP) negative electrode and Ni(OH)2 grown on NGP (Ni(OH)2/NGP) as positive electrode, and they have attracted intensive research interest owing to their outstanding properties such as being flexible, ultrathin, and lightweight. The fabricated APSCs exhibit a high areal Csp of 3.05 F/cm3 and superior cycling stability. The novel asymmetric APSCs also exhibit high energy density of 0.35 mW h/cm3, high power density of 32.5 mW/cm3, and superior cycling performance (<17% capacitance loss after 12,000 cycles at a high scan rate of 100 mV/s). This work shows the first example of amorphous porous metal oxide/NGP electrodes for the asymmetric APSCs, and these systems hold great potential for future flexible electronic devices.

Carbon/MnO 2 Double-Walled Nanotube Arrays with Fast Ion and Electron Transmission for High-Performance Supercapacitors

The novel carbon (C)/MnO2 double-walled nanotube arrays (DNTAs) are designed and fabricated via template-assisted electrodeposition. The unique DNTA architectures of C/MnO2 composites with high weight fraction of MnO2 allow high electrode utilization ratio and facilitate electron and ion transmission. In the half-cell test, the hybrid C/MnO2 DNTAs as electrodes show a large specific capacitance (Csp) of 793 F/g at the scan rate of 5 mV/s, high energy/power densities, and much enhanced long-term cycle stability. After 5,000 cycles, the Csp retention of C/MnO2 DNTAs keeps ∼97%, which is much larger than 69% of the MnO2 nanotube arrays (NTAs). The symmetrical supercapacitors (SSCs) composed of C/MnO2 DNTAs also show the predominant performance, such as large Csp of 161 F/g and high energy density of ∼35 Wh/kg, indicating that the C/MnO2 DNTAs is a potential electrode for supercapacitors. The high order pore passages, double-walled structures, hollow structures, and high conductivity are responsible for the superior performance of C/MnO2 DNTAs. Such hybrid C/MnO2 DNTAs may bring new opportunities for the development of supercapacitors with superior performance.

Flexible symmetrical planar supercapacitors based on multi-layered MnO2/Ni/graphite/paper electrodes with high-efficient electrochemical energy storage

High-performance planar supercapacitors have attracted increasing attention because of their thin, light and flexible abilities. Here we developed novel flexible symmetrical planar supercapacitors (FSPSCs) by using the multi-layered MnO2/Ni/graphite/paper electrodes that were fabricated by sequentially coating a graphite layer, Ni layer, and MnO2 layer on ordinary cellulose paper. The MnO2/Ni/graphite/paper electrodes show a large specific capacitance (Csp) of 175 mF cm−2 at a scan rate of 5 mV s−1. The assembled FSPSCs based on the multi-layered MnO2/Ni/graphite/paper electrodes exhibit a large volumetric Csp (1020 mF cm−3 at 5 mV s−1) and a superior long-term cycle stability (less 4% loss of the maximum Csp after 6000 cycles). The FSPSCs based on the multi-layered MnO2/Ni/graphite/paper electrodes may open up new opportunities in developing novel supercapacitor devices because of the low-cost, high performance, and facile large-scale fabrication procedures.

Efficient Hydrogen Evolution Electrocatalysis Using Cobalt Nanotubes Decorated with Titanium Dioxide Nanodots

TiO2 Co nanotubes decorated with nanodots (TiO2 NDs/Co NSNTs-CFs) are reported as high-performance earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solution. TiO2 NDs/Co NSNTs can promote water adsorption and optimize the free energy of hydrogen adsorption. More importantly, the absorbed water can be easily activated in the presence of the TiO2 -Co hybrid structure. These advantages will significantly promote HER. TiO2 NDs/Co NSNTs-CFs as electrocatalysts show a high catalytic performance towards HER in alkaline solution. This study will open up a new avenue for designing and fabricating low-cost high-performance HER catalysts.

Ni@NiO core–shell nanoparticle tube arrays with enhanced supercapacitor performance

Nanotube arrays have shown great potential in a variety of important applications, such as energy storage. To enhance their inherent properties and endow nanotubes with multifunctionality, the rational design of nanotube arrays with higher complexity in terms of structure and composition is highly desired and still remains a great challenge. In this work, Ni@NiO core–shell nanoparticle tube arrays (CSNPTAs) were designed and fabricated via an efficient, low-cost and environmentally friendly ZnO nanorods template-assisted electrodeposition method, and they are effective in enhancing ion diffusion and surface area as well as preventing nanoparticle agglomeration because of the unique array structures, hollow structures, and core–shell nanoparticle structures. As electrodes, Ni@NiO CSNPTAs show high electrochemical performance such as high specific capacitance (Csp), superior rate capability, and excellent cycle stability and exhibit promising applications for high-performance supercapacitors (SCs).

Pt–MoO3–RGO ternary hybrid hollow nanorod arrays as high-performance catalysts for methanol electrooxidation

Here we design and synthesize novel Pt–MoO3–RGO (reduced graphene oxide) ternary hybrid hollow nanorod arrays (HNRAs) as anode catalysts for methanol electrooxidation. These fabricated Pt–MoO3–RGO HNRAs have highly dispersive MoO3, RGO, and Pt nanocrystals (∼3 nm), which leads to rich heterogeneous interfaces and strong synergistic effects among Pt, MoO3 and RGO. The Pt–MoO3–RGO HNRAs exhibit a high electrochemically active surface area (ECSA) of 71.20 m2 per (g, Pt), which is much higher than those of Pt–MoO3 HNRAs (34.23 m2 per (g, Pt)) and commercial Pt/C catalysts (52.89 m2 per (g, Pt)). Because of the strong synergistic effects and structural advantages, these Pt–MoO3–RGO HNRAs show much enhanced electrocatalytic activity, durability and CO anti-poisoning ability compared with Pt–MoO3 HNRAs and commercial Pt/C catalysts. Besides, the electrocatalytic activity of Pt–MoO3–RGO HNRAs also exceeds those of many Pt-based catalysts reported in the literature. Our finding demonstrates the importance of the interfacial and structural effects in harnessing the true electrocatalytic potential of Pt-based catalysts and will open up new strategies for the development of high-performance catalysts for methanol electrooxidation.