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

Graphene and related two-dimensional crystals and hybrid systems showcase several key properties that can address emerging energy needs, in particular for the ever growing market of portable and wearable energy conversion and storage devices. Graphene's flexibility, large surface area, and chemical stability, combined with its excellent electrical and thermal conductivity, make it promising as a catalyst in fuel and dye-sensitized solar cells. Chemically functionalized graphene can also improve storage and diffusion of ionic species and electric charge in batteries and supercapacitors. Two-dimensional crystals provide optoelectronic and photocatalytic properties complementing those of graphene, enabling the realization of ultrathin-film photovoltaic devices or systems for hydrogen production. Here, we review the use of graphene and related materials for energy conversion and storage, outlining the roadmap for future applications.

Graphene, related two-dimensional crystals, and hybrid systems for energy conversion and storage

日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

Annual review of condensed matter physics

Review: Carbon nanotube based electrochemical sensors for biomolecules.

Influence of barrier on partial discharge activity by a conducting particle in liquid nitrogen under AC voltages adopting UHF technique

Nanostructured carbon thin films have been actively investigated recently for their electroresistance (ER) properties. Furthermore, carbon films with nonlinear current?voltage (I?V) characteristics have potential application in field-emission devices. This has motivated us to study the effect of various growth parameters on the physical and morphological properties of carbon films grown by pulsed laser deposition (PLD). Carbon films have been deposited using a graphite target at different partial pressures of argon. The morphology of film surfaces deposited at various growth conditions was monitored using an atomic force microscope (AFM). AFM studies showed nanostructured grain growth with average grain size of about 80?90?nm. As the deposition time was decreased down to 1?min, the grain size was also found to decrease correspondingly. From Raman spectroscopic measurements an increase in the I(D)/I(G) ratio and a decrease in FWHM (G) clearly revealed the promotion of sp2 hybridization as the substrate temperature increased. All the films show semiconducting behaviour with the dominant conduction process being the three-dimensional (3D) variable range hopping (VRH) mechanism. Nonlinear I?V curves were obtained for carbon films deposited on p-type Si indicating diode-like behaviour. The most significant result of this study was the observation of a large electroresistance value.

Electrical transport and morphological study of PLD-grown nanostructured amorphous carbon thin films

Polycrystalline, Dy0.5Gd4.5Si2Ge2 compound (monoclinic, space group P21/a) has been synthesized and characterized. This compound orders ferromagnetically at ∼210 K (TC) followed by an antiferromagnetic-like transition at ∼21 K (TN). The electrical resistivity, ρ, follows T2 law in the ferromagnetically ordered state indicating the presence of dominant single magnon scattering. There is a pronounced increase of resistivity in the vicinity of antiferromagnetic transition. Thermoelectric power, S, indicates a slope change near TC and has T3 dependence at low temperatures.

Electrical transport properties of Dy0.5Gd4.5Si2Ge2

/pdf/the-effect-of-particle-size-on-the-magnetic-properties-of-zr4cuj6w1f.pdf

The effect of particle size on the magnetic properties of Y2FeCoO6

Double perovskite based magnets wherein frustration and competition between emergent degrees of freedom are at play can lead to novel electronic and magnetic phenomena. Herein, we report the electronic structure and magnetic properties of an ordered double perovskite material Ho 2 CoMnO 6 . In the double perovskite with general class A 2 BB (cid:48) O 6 , the octahedral B and B (cid:48) -site has a distinct crystallographic site. The Rietveld reﬁnement of XRD data reveal that Ho 2 CoMnO 6 crystallizes in the monoclinic P 2 1 /n space group. The X-ray photoelectron spectroscopy conﬁrms the charge state of cations present in this material. The temperature dependence of magnetization and speciﬁc heat exhibit a long-range ferromagnetic ordering at T C ∼ 76 K owing to the presence of super exchange interaction between Co 2+ and Mn 4+ moments. Furthermore, the magnetization isotherm at 5 K shows a hysteresis curve that conﬁrms ferromagnetic behavior of this double perovskite. We observed a re-entrant glassy state in the intermediate temperature regime, which is attributed to the presence of inherent anti-site disorder and competing interactions. A large magnetocaloric eﬀect has been observed much below the ferromagnetic transition temperature. The temperature dependent Raman spectroscopy studies support the presence of spin-phonon coupling and short range order above T C in this double perovskite. The stabilization of magnetic ordering and charge states is further analyzed through electronic structure calculations. The latter also infers the compound to be a narrow band gap insulator with the gap arising between the lower and upper Hubbard Co- d subbands. Our results demonstrate that anti-site disorder and complex 3 d -4 f exchange interactions in the spin-lattice account for the observed electronic and magnetic properties in this promising double perovskite material.

K. Sethupathi

Papers

Influence of barrier on partial discharge activity by a conducting particle in liquid nitrogen under AC voltages adopting UHF technique

Electrical transport and morphological study of PLD-grown nanostructured amorphous carbon thin films

Electrical transport properties of Dy0.5Gd4.5Si2Ge2

The effect of particle size on the magnetic properties of Y2FeCoO6

Electronic structure and magnetic properties of 3d-4f double perovskite material