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.

Magnetism in DyGd4Si2Ge2

Samarium iron garnet (Sm3Fe5O12) is a potential but less explored ferromagnetic rare earth iron garnet. Cobalt substitution induced structural modifications that results enhancement in room temperature as well as low temperature magnetic behavior of Sm3Fe5O12 prepared by co-precipitation has been probed using superconducting quantum interface device. At room temperature, replacement of 0.3 atomic% Fe by Co improves the saturation value from 12.63 to 25.26 emu/g and the coercivity is found to be increased from 0.023 to 0.09 kOe. Similarly, at low temperature (∼5K) the enhancement in saturation magnetization and coercivity is found to be 17.62 to 31.23 emu/g and 1.55 to 2.32 kOe respectively. Rooted from the morphological modifications, the enhanced magnetism observed here might also be from the modifications in the super-exchange interaction and formation of oxygen vacancies due to the larger ionic radius of replaced Co2+ ions in the Fe3+ sites of Sm3Fe5O12. 

Coexistence of ferri and ferromagnetism in cobalt substituted samarium iron garnet

The rare earth based transition metal perovskites are well known for their tunable physical properties. Here we present the dielectric response of the magnetic perovskite Eu2FeCoO6 from impedance spectroscopy measurements. The compound having a weak ferromagnetic ground state, is subjected to impedance spectroscopy measurements through the frequency range 100 Hz to 10 MHz for the temperature range 123 K-473 K. The dielectric permittivity shows huge values at high temperatures with low frequency. The two step relaxation process is inferred from Arrhenius fit.The rare earth based transition metal perovskites are well known for their tunable physical properties. Here we present the dielectric response of the magnetic perovskite Eu2FeCoO6 from impedance spectroscopy measurements. The compound having a weak ferromagnetic ground state, is subjected to impedance spectroscopy measurements through the frequency range 100 Hz to 10 MHz for the temperature range 123 K-473 K. The dielectric permittivity shows huge values at high temperatures with low frequency. The two step relaxation process is inferred from Arrhenius fit.

Dielectric response of the magnetic perovskite oxide Eu2FeCoO6

Diamond is an excellent band insulator However, boron (B) doping is known to induce superconductivity We present two interesting effects in superconducting B doped diamond (BDD) thin films: i) Wohlleben effect (paramagnetic Meissner effect, PME) and ii) a low field spin glass like susceptibility anomaly We have performed electrical and magnetic measurements (under pressure in one sample) at dopings (14 , 26 and 36) X 1021 cm-3, in a temperature range 2 - 10 K PME, a low field anomaly in inhomogeneous superconductors could arise from flux trapping, flux compression, or for non-trivial reason such as emergent Josephson Pi junctions Joint occurrence of PME and spin glass type anomalies points to possible emergence of Pi junctions BDD is a disordered s-wave superconductor; and Pi junctions could be produced by spin flip scattering of spin half moments when present at weak superconducting regions (Bulaevski et al 1978) A frustrated network of 0 and Pi junctions will result (Kusmartsev et al 1992) in a distribution of spontaneous equilibrium supercurrents, a phase glass state Anderson localized spin half spinons embedded in a metallic fluid (two fluid model of Bhatt et al) could create Pi junction by spin flip scattering Our findings are consistent with presence of Pi junctions, invoked to explain their (Bhattacharyya et al) observation of certain resistance anomaly in BDD

Wohlleben Effect and Emergent Pi junctions in superconducting Boron doped Diamond thin films

Pb(1-3x/2)LaxZr0.65Ti0.35O3 (x = 6, 7, 8 and 9%) show diffusivity values as 1.55, 1.72, 1.94 and 2.18, respectively. The differential permittivity strongly depends on temperature and electric field...

K. Sethupathi

Papers

Magnetism in DyGd4Si2Ge2

Coexistence of ferri and ferromagnetism in cobalt substituted samarium iron garnet

Dielectric response of the magnetic perovskite oxide Eu2FeCoO6

Wohlleben Effect and Emergent Pi junctions in superconducting Boron doped Diamond thin films

Temperature Dependence of Energy Storage Density and Differential Permittivity and Bandgap Study of Relaxor (Pb,La)Zr0.65Ti0.35O3