The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core–shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

http://repository.ust.hk/ir/bitstream/1783.1-77094/1/acs.chemrev.5b00462_withlink.pdf

Recent Advances in Electrocatalysts for Oxygen Reduction Reaction

Using a simple hydrothermal procedure, cobalt oxide (Co3O4) nanowires were in situ synthesized on three-dimensional (3D) graphene foam grown by chemical vapor deposition. The structure and morphology of the resulting 3D graphene/Co3O4 composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The 3D graphene/Co3O4 composite was used as the monolithic free-standing electrode for supercapacitor application and for enzymeless electrochemical detection of glucose. We demonstrate that it is capable of delivering high specific capacitance of ∼1100 F g–1 at a current density of 10 A g–1 with excellent cycling stability, and it can detect glucose with a ultrahigh sensitivity of 3.39 mA mM–1 cm–2 and a remarkable lower detection limit of <25 nM (S/N = 8.5).

3D Graphene–Cobalt Oxide Electrode for High-Performance Supercapacitor and Enzymeless Glucose Detection

In the present review we try to give a comprehensive and most up to date view to the field, with an emphasis on the currently most investigated anodic TiO2 nanotube arrays. We will first give an overview of different synthesis approaches to produce TiO2 nanotubes and TiO2 nanotube arrays, and then deal with physical and chemical properties of TiO2 nanotubes and techniques to modify them. Finally, we will provide an overview of the most explored and prospective applications of nanotubular TiO2.

One-dimensional titanium dioxide nanomaterials: nanotubes.

This paper gives a comprehensive review about the most recent progress in synthesis, characterization, fundamental understanding, and the performance of graphene and graphene oxide sponges. Practical applications are considered including use in composite materials, as the electrode materials for electrochemical sensors, as absorbers for both gases and liquids, and as electrode materials for devices involved in electrochemical energy storage and conversion. Several advantages of both graphene and graphene oxide sponges such as three dimensional graphene networks, high surface area, high electro/thermo conductivities, high chemical/electrochemical stability, high flexibility and elasticity, and extremely high surface hydrophobicity are emphasized. To facilitate further research and development, the technical challenges are discussed, and several future research directions are also suggested in this paper.

A review of graphene and graphene oxide sponge: material synthesis and applications to energy and the environment

Flower-shaped inorganic nanocrystals(1-3) have been used for applications in catalysis(4,5) and analytical science(6,7), but so far there have been no reports of 'nanoflowers' made of organic components(8). Here, we report a method for creating hybrid organic-inorganic nanoflowers using copper (II) ions as the inorganic component and various proteins as the organic component. The protein molecules form complexes with the copper ions, and these complexes become nucleation sites for primary crystals of copper phosphate. Interaction between the protein and copper ions then leads to the growth of micrometre-sized particles that have nanoscale features and that are shaped like flower petals. When an enzyme is used as the protein component of the hybrid nanoflower, it exhibits enhanced enzymatic activity and stability compared with the free enzyme. This is attributed to the high surface area and confinement of the enzymes in the nanoflowers.

/pdf/protein-inorganic-hybrid-nanoflowers-4v9xuuz5ir.pdf

Protein-inorganic hybrid nanoflowers

Electrospun Co3O4 nanofibers for sensitive and selective glucose detection

Microbial biosensors: A review

Ultrasensitive and selective non-enzymatic glucose detection using copper nanowires.

Copper oxide nanowires (CuO NWs) were prepared by a facile two-step procedure consisting of wet-chemistry synthesis and subsequent direct calcination. The morphology, surface property, and crystal structure of the as-prepared CuO NWs were characterized by SEM, TEM, and XRD. The CuO NWs were further employed to construct a non-enzymatic glucose sensor with excellent performance toward glucose detection in 50 mM NaOH solution. The as-developed non-enzymatic glucose sensor showed a fast response time (less than 5 s) and a wide dynamic range with excellent sensitivity of 648.2 μA cm −2  mM −1 and 119.9 μA cm −2  mM −1 toward glucose detection at an applied potential of +0.55 V and +0.3 V (vs. Ag/AgCl), respectively. The Langmuir isothermal theory was employed to fit the obtained calibration curves with high correlation coefficient and the mechanisms for the glucose oxidation promoted by CuO NWs were also discussed. The good selectivity of the CuO NWs based non-enzymatic glucose sensor against electroactive compounds such as ascorbic acid, uric acid, and acetaminophen, and other sugars such as fructose and sucrose at their physiological concentrations were also demonstrated. Furthermore, good accuracy and high precision for the quantification of glucose concentration in human serum samples was attested. These good features indicate that CuO NWs have a great potential in the development of sensitive and selective non-enzymatic glucose sensor.

CuO nanowires based sensitive and selective non-enzymatic glucose detection

Following a facile two-step synthesis route, NiO–Ag hybrid nanofibers, NiO nanofibers, and porous Ag were prepared. Scanning electron microscopy and transmission electron microscopy were employed to characterize the morphology of the as-prepared samples. Fourier transform infrared spectroscopy was used to confirm the complete degradation of the polymer matrix and the conversion of metal salts to metal oxides. X-Ray diffraction and X-ray photoelectron spectroscopy were performed to investigate the crystal structures and compositions of the final products. The as-prepared samples were then applied to construct non-enzymatic sensors for glucose detection. The NiO–Ag hybrid nanofiber-based sensor shows much higher sensitivity, lower detection limit and wider linear range in glucose detection compared to the NiO nanofibers or the porous Ag based sensor. A synergistic effect was achieved between NiO and Ag. High selectivity against uric acid and ascorbic acid was also achieved from the NiO–Ag nanofibers and NiO nanofiber-based sensors at an applied potential of 0.6 V. A mechanism of the excellent selectivity was proposed for the first time. The application of NiO–Ag nanofibers for selective glucose detection was also demonstrated using human serum sample, and the result is in good agreement with that of commercial glucose meter. The excellent performance of the developed inorganic nanofiber-based glucose sensor, combined with good reproducibility, low cost and inherent stability of inorganic materials, indicates great commercial value in clinical diagnosis of diabetes.

Preparation and characterization of NiO–Ag nanofibers, NiO nanofibers, and porous Ag: towards the development of a highly sensitive and selective non-enzymatic glucose sensor

Liang Su

Papers

Electrospun Co3O4 nanofibers for sensitive and selective glucose detection

Microbial biosensors: A review

Ultrasensitive and selective non-enzymatic glucose detection using copper nanowires.

CuO nanowires based sensitive and selective non-enzymatic glucose detection

Preparation and characterization of NiO–Ag nanofibers, NiO nanofibers, and porous Ag: towards the development of a highly sensitive and selective non-enzymatic glucose sensor