Suqin Ci

Nitrogen‐Enriched Core‐Shell Structured Fe/Fe3C‐C Nanorods as Advanced Electrocatalysts for Oxygen Reduction Reaction

A cost-effective route for the preparation of Fe(3) C-based core-shell structured catalysts for oxygen reduction reactions was developed. The novel catalysts generated a much higher power density (i.e., three times higher at R(ex) of 1 Ω) than the Pt/C in microbial fuel cells. Furthermore, the N-Fe/Fe(3)C@C features an ultralow cost and excellent long-term stability suitable for mass production.

Perpendicularly Oriented MoSe2/Graphene Nanosheets as Advanced Electrocatalysts for Hydrogen Evolution

By increasing the density of exposed active edges, the perpendicularly oriented structure of MoSe2 nanosheets facilitates ion/electrolyte transport at the electrode interface and minimizes the restacking of nanosheets, while the graphene improves the electrical contact between the catalyst and the electrode. This makes the MoSe2 /graphene hybrid perfect as a catalyst in the hydrogen evolution reaction (HER). It shows a greatly improved catalytic activity compared with bare MoSe2 nanosheets.

Nickel oxide hollow microsphere for non-enzyme glucose detection.

A facile strategy has been developed to fabricate nickel oxide hollow microspheres (NiO-HMSs) through a solvothermal method by using a mixed solvent of ethanol and water with the assistance of sodium dodecyl sulfate (SDS). Various techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), and powder X-ray diffraction (XRD), were used to characterize the morphology and the structure of as-prepared samples. It was confirmed that the products possess a hollow microsphere structure that is constructed by interconnecting porous nanoplate framework. Electrochemical studies indicate that the NiO-HMS exhibits excellent stability and high catalytic activity for electrocatalytic oxidation of glucose in alkaline solutions, which enables the NiO-HMS to be used in enzyme-free amperometric sensors for glucose determination. It was demonstrated that the NiO-HMS-based glucose biosensor offers a variety of merits, such as a wide linear response window for glucose concentrations of 1.67 μM-6.87 mM, short response time (3 s), a lower detection limit of 0.53 μM (S/N=3), high sensitivity (~2.39 mA mM(-1) cm(-2)) as well as good stability and repeatability.

Synthesizing nitrogen-doped activated carbon and probing its active sites for oxygen reduction reaction in microbial fuel cells.

Cost-effective cathode catalysts are critical to the development of microbial fuel cell (MFC) technology. Herein, a synthesis route is presented to improve the nitrogen content and nitrogen functionality in the nitrogen-doped activated carbon (AC) as a low cost and efficient catalyst for oxygen reduction reaction (ORR). It was demonstrated that key factors for successful nitrogen doping were the proper pretreatment with acidic and alkaline solutions consecutively and the use of a solid-state nitrogen precursor. The AC pretreated with both acidic and alkaline solutions resulted in a nitrogen content of 8.65% (atom %) (in which 5.56% is pyridinic-N) on its surface, and exhibited an outstanding electrocatalytic activity for ORR in both electrochemical and MFC tests. A good agreement between pyridinic-N content and ORR activity was observed, indicating that pyridinic-N is the most active site for ORR in the nitrogen-doped AC. The pretreated nitrogen-doped AC catalysts resulted in a higher maximum power density than the untreated AC and the commercial Pt/C (10% Pt) catalysts. The exceptional performance associated with the advantages, such as simple and convenient preparation procedure, easily obtained raw materials, and low cost, makes the pretreated nitrogen-doped AC promising for the ongoing effort to scale up MFCs.

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.

Nitrogen-doped graphene–vanadium carbide hybrids as a high-performance oxygen reduction reaction electrocatalyst support in alkaline media

A high-efficiency and stable electrocatalyst for oxygen reduction reaction (ORR) is critical for fuel cells. Here we report a new type of ORR catalyst composed of platinum nanocrystals loaded on nitrogen-doped graphene–vanadium carbide (VC) hybrids. This is the first report on using graphene oxide as the carbon source in the synthesis of transition-metal carbides as ORR catalysts; the electrochemical tests and theoretical modeling prove that the N-doping in both VC and graphene could effectively improve the overall catalytic activity. The catalytic performance of the hybrids in alkaline solutions is superior to that of commercial Pt/C catalysts in terms of the oxygen-reduction half-wave potential and the mass activity. The stability study of the catalyst also shows less degradation in catalytic activity after 3000 cycles compared with Pt/C and the hybrid catalyst structure remains virtually unchanged. Therefore, using inexpensive hybrids of high-conductivity nitrogen-doped transition-metal carbides and nanocarbon as the catalyst support presents a new direction to optimize catalyst performance for next-generation fuel cells.

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.

Rational design of mesoporous NiFe-alloy-based hybrids for oxygen conversion electrocatalysis

A mesoporous NiFe-based alloy was synthesized through a hard-template technique and investigated as the electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Precious metal-free elements, i.e., nitrogen (N), nickel (Ni), and iron (Fe), were merged together through either doping or alloying to form a mesoporous structure supporting NiFe-alloy electrocatalyst (m-NiFe/CNx). The synergetic effects from multiple active sites, in combination with structural merits, endowed the m-NiFe/CNx electrocatalyst with an excellent electrocatalytic activity for both OER and ORR, including high activity, fast kinetics, modest overpotential, and excellent stability. The m-NiFe/CNx also featured a simple and scalable synthesis process with a low cost, which makes it an attractive alternative catalyst to precious metal-based electrocatalysts for OER and ORR.

Improved electrochemical properties of single crystalline NiO nanoflakes for lithium storage and oxygen electroreduction

A facile strategy has been developed to realize the controllable synthesis of single crystalline NiO nanoflakes. According to the SEM, TEM and BET analysis, it was found that the m-NiO nanoflakes have a hexagonal structure with an average pore diameter of 4.4 nm, and exhibit a high surface area of 113.4 m2 g−1 and a pore volume around 0.142 cm3 g−1. The m-NiO nanoflakes exhibit a significantly improved electrochemical performance as an anode of lithium-ion batteries (LIBs) compared with bulk NiO based on cyclic voltammograms and galvanostatic measurement. Additionally, the m-NiO nanoflakes showed remarkable advanced activity for catalyzing oxygen reduction reaction (ORR ) relative to the bulk NiO electrode and the bare electrode. Further, rotating disk electrodes demonstrated that the m-NiO nanoflakes, as the support of the Pt nanoparticles, shows significantly improved activity for ORRs.

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.