Zhenhai Wen

Porous Co3O4 hollow nanododecahedra for nonenzymatic glucose biosensor and biofuel cell

Cobalt oxide hollow nanododecahedra (Co3O4-HND) is synthesized by a facile thermal transformation of cobalt-based metal-organic framework (Co-MOF, ZIF-67) template. The morphology and properties of the Co3O4-HND are characterized by a set of techniques, including transmission electron microscope (TEM), powder X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunner-Emmet-Teller (BET). When tested as a non-enzymatic electrocatalyst for glucose oxidation reaction, the Co3O4-HND exhibits a high activity and shows an outstanding performance for determining glucose with a wide window of 2.0μM to 6.06mM, a high sensitivity of 708.4μAmM(-1)cm(-2), a low detection limit of 0.58μM (S/N=3), and fast response time(<2s). Based on the nonenzymatic oxidation of glucose, Co3O4-HND could be served as an attractive non-enzyme and noble-metal-free electrocatalyst in glucose fuel cell (GFC) due to its excellent electrochemical properties, low cost and facile preparation.

Oxygen‐Containing Amorphous Cobalt Sulfide Porous Nanocubes as High‐Activity Electrocatalysts for the Oxygen Evolution Reaction in an Alkaline/Neutral Medium

A novel OER electrocatalyst, namely oxygen-incorporated amorphous cobalt sulfide porous nanocubes (A-CoS4.6 O0.6 PNCs), show advantages over the benchmark RuO2 catalyst in alkaline/neutral medium. Experiments combining with calculation demonstrate that the desirable O* adsorption energy, associated with the distorted CoS4.6 O0.6 octahedron structure and the oxygen doping, contribute synergistically to the outstanding electrocatalytic activity.

3D graphene network encapsulating SnO2 hollow spheres as a high-performance anode material for lithium-ion batteries

Herein, we report a reliable method for the synthesis of nanohybrids with interconnected networks of reduced graphene oxide (rGO) enwrapping hollow SnO2 nanospheres (H-SnO2@rGO), which is implemented by an electrostatic assembly process between positively charged hollow SnO2 nanospheres and negatively charged rGO. Systematic characterizations demonstrate that the as-developed H-SnO2@rGO has a unique three-dimensional (3D) nanostructure with favorable features for lithium ions storage, which not only provides robust protection against the aggregation and volume changes of the SnO2 nanospheres, but also ensures high transport kinetics for both electrons and lithium ions. The as-developed H-SnO2@rGO exhibits an outstanding electrochemical performance as an anode material for lithium-ion batteries, showing a high reversible capacity of 1107 mA h g−1 after 100 cycles at a current density of 0.1 A g−1 and maintaining 552 mA h g−1 over 500 cycles at a current density up to 1 A g−1.

Multifunctional high-activity and robust electrocatalyst derived from metal–organic frameworks

High-activity electrocatalysts with robust structure are critical for development of renewable-energy technologies. Herein, a hybrid of cobalt nanoparticles embedded in N-doped carbon nanotubes (Co@NCNT) was fabricated via economically scalable pyrolysis of a mixture of a Co-based metal–organic framework (ZIF-67) and dicyandiamide. The as-synthesized Co@NCNT hybrid was characterized by techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photon spectroscopy (XPS) etc., confirming that it possessed desirable properties of high surface area, robust structure, and good conductivity. A series of electrochemical measurements demonstrated that the Co@NCNT exhibits high activity and excellent durability toward several important electrochemical reactions, including hydrogen evolution reaction (HER) in pH-universal electrolyte, oxygen reduction reaction (ORR) in both acidic and alkaline media, glucose oxidation reaction (GOR), and oxygen evolution reaction (OER) in alkaline medium, mainly as a result of the synergistic effects of unique structure and high surface area of the Co nanoparticles and nitrogen dopant in the nanocomposite. A zinc–air battery with outstanding performance was set up using the Co@NCNT as cathode material, demonstrating its potential applications in energy storage and as a conversion system device.

In situ integration of CoFe alloy nanoparticles with nitrogen-doped carbon nanotubes as advanced bifunctional cathode catalysts for Zn–air batteries

Electrochemical catalysis of O2-incorporated reactions is a promising strategy for metal-air batteries. The performance of metal-air batteries is determined by the catalytic activities of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Therefore, developing efficient catalysts with superior activities for the ORR and OER is of great significance to expand the application range of metal-air batteries. Herein, CoFe alloy nanoparticles adhered to the inside wall of nitrogen doped carbon nanotubes (CoFe@NCNTs) are synthesized and can function as a Janus particle to efficiently catalyze the ORR and OER with desirable activities in 0.1 M KOH solution. Specifically, the CoFe@NCNTs present an onset potential of 0.95 V and a half-wave potential of 0.84 V as an ORR catalyst. When used as an air-cathode catalyst for a Zn-air battery, the CoFe@NCNTs cathode performs better than a Pt/C cathode, showing a high open-circuit potential of 1.45 V, a maximum power density of 150 mW cm-2 and an average specific capacity of 808 mA h gzn-1 at current densities from 2 mA cm-2 to 10 mA cm-2.

Graphene-based electrode materials for microbial fuel cells

Microbial fuel cells (MFCs) are environmentally friendly technology capable of converting chemical energy stored in waste-waters directly into electrical energy by using microorganisms as biocatalysts. However, the overall low power density of the MFC and the high cost of its components are two major barriers for its commercialization. Among all the factors, the electrodes (cathode and anode) materials play the significant role in affecting the performance of MFCs. Recently, the performance of MFCs has been improved by using graphene-based electrodes that are more conductive and mechanically stable with larger surface area and higher electrocatalytic activity compared to the conventional carbon materials. This paper provides an overview of recent research progress in graphene-based materials as electrodes for MFCs, which will be the promising candidates for developing MFCs and other bioelectrochemical systems to achieve sustainable water/wastewater treatment and bioenergy production.中文摘要微生物燃料电池是一种采用微生物作为生物催化剂, 直接将储藏在废水中的化学能转化为电能的环境友好技术. 目前, 微生物燃料电池的商业发展仍受制于功率密度低、构成部件成本高这两个缺陷. 在制约微生物燃料电池商业化的因素中, 电极(包括阴极和阳极)材料具有举足轻重的地位. 相对于传统材料, 基于石墨烯的电极材料具有优异的导电性能、稳定的机械性能、较大的比表面积以及高的电催化活性, 它的使用大大提高了微生物燃料电池的性能. 本文主要综述了近期基于石墨烯基电极材料微生物燃料电池的研究进展, 基于石墨烯的电极材料有望用于可持续性的废水处理及生物能利用技术, 并在未来微生物燃料电池以及其他生物电化学系统中广泛应用.

Three-Dimensional Network Architecture with Hybrid Nanocarbon Composites Supporting Few-Layer MoS2 for Lithium and Sodium Storage

The exploration of anode materials for lithium ion batteries (LIBs) or sodium ion batteries (SIBs) represents a grand technological challenge to meet the continuously increased demand for the high-performance energy storage market. Here we report a facile and reliable synthetic strategy for in situ growth of few-layer MoS2 nanosheets on reduced graphene oxide (rGO) cross-linked hollow carbon spheres (HCS) with formation of three-dimensional (3D) network nanohybrids (MoS2-rGO/HCS). Systematic electrochemical studies demonstrate, as an anode of LIBs, the as-developed MoS2-rGO/HCS can deliver a reversible capacity of 1145 mAh g-1 after 100 cycles at 0.1 A g-1 and a revisible capacity of 753 mAh g-1 over 1000 cycles at 2 A g-1. For SIBs, the as-developed MoS2-rGO/HCS can also maintain a reversible capacity of 443 mAh g-1 at 1 A g-1 after 500 cycles. The excellent electrochemical performance can be attributed to the 3D porous structures, in which the few-layer MoS2 nanosheets with expanded interlayers can provide shortened ion diffusion paths and improved Li+/Na+ diffusion mobility, and the hollow porous carbon spheres and the outside graphene network are able to improve the conductivity and maintain the structural integrity.

Alkaline–Acid Zn–H2O Fuel Cell for the Simultaneous Generation of Hydrogen and Electricity

An alkaline-acid Zn-H2 O fuel cell is proposed for the simultaneous generation of electricity with an open circuit voltage of about 1.25 V and production of H2 with almost 100 % Faradic efficiency. We demonstrate that, as a result of harvesting energy from both electrochemical neutralization and electrochemical Zn oxidation, the as-developed hybrid cell can deliver a power density of up to 80 mW cm-2 and an energy density of 934 Wh kg-1 and maintain long-term stability for H2 production with an output voltage of 1.16 V at a current density of 10 mA cm-2 .

Three-dimensional nanoarchitectures of Co nanoparticles inlayed on N-doped macroporous carbon as bifunctional electrocatalysts for glucose fuel cells

Exploring high-performance electrocatalysts is of great importance for developing clean and renewable energy conversion systems such as fuel cells and metal–air batteries. Hybrid nanostructures with transition metal nanoparticles embedded in a carbon matrix exhibit outstanding electrocatalytic activity and have emerged as promising low-cost alternatives to precious metal catalysts for a variety of electrochemical reactions. Herein, we report a convenient synthesis route to prepare a three-dimensional porous nanoarchitecture with Co nanoparticles (Co NPs) inlayed in nitrogen-doped macroporous carbon (Co/N-MC). The hybrids show an outstanding electrocatalytic activity for the oxygen reduction (ORR) and glucose oxidation reaction (GOR) due to the synergistic contribution of the Co NPs and nitrogen doping in macroporous carbon. Benefitting from their outstanding electrocatalytic activity in the ORR and GOR, a home-made glucose fuel cell (GFC) was set up using Co/N-MC as the anode and cathode material, delivering a considerable power density with decent stability.

Bottom‐Up Construction of Porous Organic Frameworks with Built‐In TEMPO as a Cathode for Lithium–Sulfur Batteries

Two redox-active porous organic frameworks (POFs) with a built-in radical moiety (TEMPO) and hierarchical porous structures were synthesized through a facile bottom-up strategy and studied as cathode materials for lithium-sulfur (Li-S) batteries. The sulfur loading in these two POFs reached 61 %, benefitting from their large pore volumes. Owing to the highly dense docking sites of TEMPO, sulfur could be covalently immobilized within the porous networks and efficiently inhibit the shuttle effect, thereby significantly improving the cycling performance. The composites TPE-TEMPO-POF-S (TPE=tetraphenylethene) deliver a capacity in excess of 470 mAh g-1 after 200 cycles with a coulombic efficiency of around 100 % at a current rate of 0.1 C. Furthermore, TEMPO-POFs with sulfur embedded showed excellent rate capability with limited capacity loss at rates of 0.1-1 C.