Pei Kang Shen

Palladium-Based Electrocatalysts for Alcohol Oxidation in Half Cells and in Direct Alcohol Fuel Cells

Direct alcohol fuel cells (DAFCs) are attracting increasing interest as power sources for portable applications due to some unquestionable advantages over analogous devices fed with hydrogen.1 Alcohols, such as methanol, ethanol, ethylene glycol, and glycerol, exhibit high volumetric energy density, and their storage and transport are much easier as compared to hydrogen. On the other hand, the oxidation kinetics of any alcohol are much slower and still H2-fueled polymer electrolyte fuel cells (PEMFCs) exhibit superior electrical performance as compared to DAFCs with comparable electroactive surface areas.2,3 Increasing research efforts are therefore being carried out to design and develop more efficient anode electrocatalysts for DAFCs.

Simultaneous Formation of Ultrahigh Surface Area and Three‐Dimensional Hierarchical Porous Graphene‐Like Networks for Fast and Highly Stable Supercapacitors

A new one-step ion-exchange/activation combination method using a metal-ion exchanged resin as a carbon precursor is used to prepare a ultrahigh surface area and three-dimensional hierarchical porous graphene-like networks for fast and highly stable supercapacitors.

Porous MoO2 Nanosheets as Non‐noble Bifunctional Electrocatalysts for Overall Water Splitting

A porous MoO2 nanosheet as an active and stable bifunctional electrocatalyst for overall water splitting, is presented. It needs a cell voltage of only about 1.53 V to achieve a current density of 10 mA cm(-2) and maintains its activity for at least 24 h in a two-electrode configuration.

Hierarchical Hollow Co9S8 Microspheres: Solvothermal Synthesis, Magnetic, Electrochemical, and Electrocatalytic Properties

A simple solvothermal route in a binary solution of triethylenetetramine (TETA) and deionized water (DIW) has been used to synthesize hierarchical hollow Co(9)S(8) microspheres with high surface area (80.38 m(2) g(-1)). An appropriate volume ratio of TETA:DIW has been found to be essential for the formation of hollow Co(9)S(8) microspheres. The magnetic study indicated that the Co(9)S(8) hollow microspheres are paramagnetic at high temperature and antiferromagnetic at low temperature. The oxygen reduction reaction experiments demonstrated that the onset potential of the Co(9)S(8) sample is 0.88 V, which is comparable to the value predicted for Co(9)S(8) (0.74 V) from the theoretical simulation. The discharge capability of Co(9)S(8) hollow microspheres as cathode materials for lithium ion batteries and their electrocatalytic activity for the oxygen reduction reaction (ORR) have been studied.

Bimetallic Carbide Nanocomposite Enhanced Pt Catalyst with High Activity and Stability for the Oxygen Reduction Reaction

Nanocomposites consisting of the bimetallic carbide Co(6)Mo(6)C(2) supported on graphitic carbon ((g)C) were synthesized in situ by an anion-exchange method for the first time. The Co(6)Mo(6)C(2)/(g)C nanocomposites were not only chemically stable but also electrochemically stable. The catalyst prepared by loading Pt nanoparticles onto Co(6)Mo(6)C(2)/(g)C was evaluated for the oxygen reduction reaction in acidic solution and showed superior activity and stability in comparison with commercial Pt/C. The higher mass activity of the Pt-Co(6)Mo(6)C(2)/(g)C catalyst indicated that less Pt would be required for the same performance, which in turn would reduce the cost of the fuel cell electrocatalyst. The method reported here will promote broader interest in the further development of other nanostructured materials for real-world applications.

Direct electrochemistry of hemoglobin on carbonized titania nanotubes and its application in a sensitive reagentless hydrogen peroxide biosensor.

Carbonized TiO(2) nanotubes (TNT/C) prepared by carbonization with organic polymers possess advantages combined from high conductivity of carbon and nanostructure of TiO(2) nanotubes. The material was used as a supporting matrix to immobilize a redox protein, hemoglobin (Hb), to explore its direct electron transfer ability. The apparent heterogeneous electron transfer rate constant (k(ET)) of Hb on TNT/C is 108s(-1), which is much higher than that in the reported works, demonstrating excellent direct electrochemistry behavior. The TNT/C-Hb modified glassy carbon electrode (GCE) demonstrates significant electrocatalytic activity for reduction of hydrogen peroxide with a small apparent Michaelis-Menten constant (87.5 microM). The TNT/C-Hb based H(2)O(2) sensor has a low detection limit (0.92 microM), fast response time (3s) and high dynamic response range (10(-6) to 10(-4)M), a much better performance than the reported works. These results demonstrate that a direct electrochemistry behavior can be significantly enhanced through simple carbon coating on a nanostructured material for higher reaction surface area and better conductivity. This work suggests that Hb-immobilized TNT/C has potential applications in a sensitive H(2)O(2) sensor.

Tungsten carbide promoted Pd–Fe as alcohol-tolerant electrocatalysts for oxygen reduction reactions

An intermittent microwave heating (IMH) assisted method has been used to synthesize palladium and iron on nanocrystalline tungsten carbide (denoted as PdFe-WC/C) as a cathodic electrocatalyst for oxygen reduction reactions (ORRs). The materials are characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and electrochemical techniques. The ORR activity of the PdFe-WC/C electrocatalyst in acidic solution is found to be comparable to that of Pt/C electrocatalysts. It is believed that the high catalytic activity as a Pt-free electrocatalyst originats from the synergistic effect between Pd and Fe and WC. The alcohol-tolerance and selectivity of the PdFe-WC/C electrocatalyst are favorable for the ORR in the presence of alcohol which makes it a promising cathodic electrocatalyst in direct alcohol fuel cells (DAFCs). The ORR is hardly affected in the alcohol-containing solutions up to 1.0 mol L−1alcohol. The results also revealed that the ORR on the PdFe-WC/C electrocatalyst is a four-electron process. This novel PdFe-WC/C electrocatalyst could be a Pt-free alternative for a cathodic electrocatalyst for ORRs.

One-step synthesis of Ni3S2 nanoparticles wrapped with in situ generated nitrogen-self-doped graphene sheets with highly improved electrochemical properties in Li-ion batteries

A facile strategy has been developed to fabricate Ni3S2 nanoparticles wrapped with in situ generated N-doped graphene sheets (Ni3S2@N-G). In this strategy, the nitrogen and sulfur-containing resin is introduced as a sulfur source to form the Ni3S2 nanoparticles and to provide a source of nitrogen and carbon to grow a coating of N-doped graphene sheets on their surface. As an anode material in lithium-ion batteries (LIBs), Ni3S2@N-G exhibits a highly improved reversible capacity, as well as an excellent cycling performance and rate performance. It delivers a discharge capacity of up to 809 mA h g−1 in the 150th cycle. With the successful synthesis of Ni3S2@N-G as a starting point, this facile strategy can be used to synthesize other metal sulfides/graphene sheets nanocomposites and will immensely extend its applications.

Morphologic study of electrochemically formed lead dioxide

Various electrochemical methods with different conditions were used to prepare lead dioxide (PbO2). The observation revealed that the morphology of deposited PbO2 could be controlled by simply changing deposition parameters. Under the condition of oxygen evolution, which dominates the electrode process, uniformly distributed high porous structured PbO2 was formed. The results indicated that large current density or high potential polarization should be one of the most important and necessary factors for forming high surface area PbO2 deposit. Only β-PbO2 was identified by X-ray diffraction measurement for the deposit prepared by present methods and solution. One potential application of this method is to prepare nanoscaled PbO2 parallel lines.

Nanosized tungsten carbide synthesized by a novel route at low temperature for high performance electrocatalysis.

Tungsten carbide (WC) is a widely used engineering material which is usually prepared at high temperature. A new mechanism for synthesizing nanoscaled WC at ultralow temperature has been discovered. This discovery opens a novel route to synthesize valuable WC and other carbides at a cost-efficient way. The novel formation mechanism is based on an ion-exchange resin as carbon source to locally anchor the W and Fe species. As an intermediate, FeWO4 can be formed at lower temperature, which can be directly converted into WC along with the carbonization of resin. The size of WC can be less than 2 nm. The catalyst made with Pt nanoparticles supported on nanosized WC-GC (WC-graphitized carbon) shows enhanced electrocatalytic activity for oxygen reduction reaction. The result also indicates that the Pt nanoparticles deposited on WC-GC are dominated by Pt (111) plane and shows a mass activity of 257.7 mA mg−1Pt@0.9 V.