Rongmei Kong

Copper-Nitride Nanowires Array: An Efficient Dual-Functional Catalyst Electrode for Sensitive and Selective Non-Enzymatic Glucose and Hydrogen Peroxide Sensing

It is highly attractive to develop non-noble-metal nanoarray architecture as a 3D-catalyst electrode for molecular detection due to its large specific surface area and easy accessibility to target molecules. Here, we report the development of a copper-nitride nanowires array on copper foam (Cu3 N NA/CF) as a dual-functional catalyst electrode for efficient glucose oxidation in alkaline solutions and hydrogen peroxide (H2 O2 ) reduction in neutral solutions. Electrochemical tests indicate that such Cu3 N NA/CF possesses superior non-enzymatic sensing ability toward rapid glucose and H2 O2 detection with high selectivity. At 0.40u2005V, this sensor offers a high sensitivity of 14u2009180u2005μAu2009mmu2009cm-2 for glucose detection, with a wide linear range from 1u2005μm to 2u2005mm, a low detection limit of 13u2005nm (S/N=3), and satisfactory stability and reproducibility. Its application in determining glucose in human blood serum is also demonstrated. Amperometric H2 O2 sensing can also been realized with a sensitivity of 7600u2005μAu2009mmu2009cm-2 , a linear range from 0.1u2005μm to 10u2005mm, and a detection limit of 8.9u2005nm (S/N=3). This 3D-nanoarray architecture holds great promise as an attractive sensing platform toward electrochemical small molecules detection.

NiCoP Nanoarray: A Superior Pseudocapacitor Electrode with High Areal Capacitance

High-performance supercapacitors require the design and development of electrode materials with high conductivity and a large electrolyte-accessible surface area. Here, the use of a conductive NiCoP nanoarray on nickel foam (NiCoP/NF) as a superior pseudocapacitor electrode is demonstrated. This 3D electrode exhibits high areal capacitances of 9.2 and 5.97u2005Fu2009cm-2 at current densities of 2 and 50u2005mAu2009cm-2 , respectively, with good rate capability and cycling stability. The asymmetric supercapacitor (ASC) device assembled using NiCoP/NF as positive electrode and active carbon as negative electrode delivers a high energy density of 1.16u2005mWhu2009cm-2 at a power density of 1.6u2005mWu2009cm-2 with 72u2009% retention of its initial specific capacitance after 2000u2005cycles at 50u2005mAu2009cm-2 . The practical use is further demonstrated with two such ASC devices in series to light six LED indicators and also to drive an alkaline water electro- lyzer using NiCoP/NF as both cathode and anode for hydrogen production.

A cobalt-borate nanosheet array: an efficient and durable non-noble-metal electrocatalyst for water oxidation at near neutral pH

Exploitation of efficient water oxidation electrocatalysts under benign conditions is of great importance but remains a huge challenge. In this communication, we report the preparation of a cobalt-borate nanosheet array on a Ti mesh (Co-Bi/Ti) successfully converted from an electrodeposited α-Co(OH)2 nanosheet array in potassium borate (K-Bi) via in situ electrochemical tuning. The Co-Bi/Ti shows high electrocatalytic activity toward water oxidation with an overpotential of 469 mV to achieve a current density of 10 mA cm−2 in 0.1 M K-Bi, with long-term electrochemical stability with a turnover frequency of 0.15 s−1 at an overpotential of 600 mV.

Energy-efficient electrolytic hydrogen generation using a Cu3P nanoarray as a bifunctional catalyst for hydrazine oxidation and water reduction

Energy-efficient electrolytic hydrogen generation is highly desired but still remains challenging. In this work, we demonstrate that a Cu3P nanoarray on copper foam (Cu3P/CF) behaves as a high-performance electrocatalyst for hydrazine oxidation reaction (HzOR) in alkaline electrolytes. A full electrolytic system employing Cu3P/CF as both an anode for HzOR and a cathode for hydrogen evolution reaction drives 100 mA cm−2 at a voltage of 0.72 V in 1.0 M KOH aqueous solution with 0.5 M hydrazine. It also demonstrates high long-term stability.

Cobalt phosphide nanowire array as an effective electrocatalyst for non-enzymatic glucose sensing

It is of significant importance for the design of electrodes to construct enhanced electrochemical sensing platforms, and a nanoarray offers an ideal architecture for the detection of molecules. In this communication, we demonstrate that cobalt phosphide nanowire array grown in situ on titanium mesh (CoP NA/TM) exhibits high catalytic activity towards electrooxidation of glucose. As a non-enzymatic electrochemical glucose sensor, this CoP NA/TM catalytic electrode possesses superior analytical performance with a short response time of less than 5 s, a wide linear range of 0.0005-1.5 mM, a low detection limit of 0.1 μM (S/N = 3), a high sensitivity of 5168.6 μA mM-1 cm-2, and a remarkable selectivity and long-term stability for glucose detection. We further demonstrate the successful use of such glucose biosensors in human blood serum and fruit juice.

A nickel–borate–phosphate nanoarray for efficient and durable water oxidation under benign conditions

The development of earth-abundant electrocatalysts for efficient water oxidation under moderate conditions is highly desired but still a big challenge. In this communication, we demonstrate the topotactic conversion of a nickel phosphide nanoarray on carbon cloth into a nickel–borate–phosphate nanoarray (Ni–Bi–Pi/CC) by oxidative polarization in potassium borate water. When used as a 3D water oxidation catalyst, such Ni–Bi–Pi/CC shows high activity with a geometrical catalytic current density of 10 mA cm−2 at an overpotential of only 440 mV in 0.1 M K–Bi, rivaling the performances of the reported Ni-containing catalysts operated under benign conditions. Notably, this electrode also demonstrates strong long-term electrochemical durability with 100% Faradaic efficiency for oxygen evolution. All these features promise its use as an attractive low-cost catalyst electrode in water-splitting devices for mass production of hydrogen fuels under environmentally friendly conditions.

Hydrazine-assisted electrolytic hydrogen production: CoS2 nanoarray as a superior bifunctional electrocatalyst

The sluggish kinetics of the oxygen evolution reaction has severely hindered the energetic convenience of electrolytic water splitting. Herein, we demonstrate that a CoS2 nanoarray on Ti mesh (CoS2/TiM) behaves as an efficient and durable catalyst for the hydrazine oxidation reaction in 1.0 M KOH with 100 mM hydrazine, which requires the potential of 125 mV to achieve 100 mA cm−2. The high hydrogen-evolving activity of CoS2/TiM makes it a bifunctional catalyst for energy-saving electrolytic hydrogen generation by replacing water oxidation with hydrazine oxidation. To drive 100 mA cm−2, its two-electrode electrolyzer demands a low cell voltage of only 0.81 V and it exhibits remarkable long-term electrochemical durability and nearly 100% Faradic efficiency for hydrogen evolution.

Core–Shell NiFe-LDH@NiFe-Bi Nanoarray: In Situ Electrochemical Surface Derivation Preparation toward Efficient Water Oxidation Electrocatalysis in near-Neutral Media

The corrosion issue with acidic and alkaline water electrolyzers can be avoided by developing water oxidation catalysts performing efficiently under benign conditions. In this Letter, we report that a NiFe-borate layer can be generated on a NiFe-layered double hydroxide nanosheet array hydrothermally grown on carbon cloth via an in situ electrochemical surface derivation process in potassium borate (K-Bi) solution. The resulting 3D NiFe-LDH@NiFe-Bi nanoarray (NiFe-LDH@NiFe-Bi/CC) demonstrates high activity for water oxidation, demanding overpotentials of 444 and 363 mV to achieve 10 mA cm-2 in 0.1 and 0.5 M K-Bi (pH: 9.2), respectively, rivaling the performances of most reported non-noble-metal catalysts in near-neutral media. Notably, this electrode also shows strong electrochemical durability with a high turnover frequency of 0.54 mol O2 s-1 at overpotential of 600 mV. All these features promise its use as an efficient earth-abundant catalyst material for water oxidation under eco-friendly conditions.