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[en] In a unicellular cyanobacterium, the mobile fraction of phycobilisome (PBS) was found to be maximum at a particular redox value of QA (i.e., 0.52). An upward or downward shift in the redox value leads to a decrease in this mobile fraction of PBS. Furthermore, the regulatory effect of the redox state of QA on PBS mobility was found to be independent of the effect exerted by the plastoquinone pool. These findings indicate for the first time that PBS mobility is regulated by the QA redox state in cyanobacteria. A possible working mechanism underlying this control is discussed.
[en] Present work is devoted to kinetics of reduction of molecular oxidant by metal containing redox. Constructed generalized kinetic model of redox process in the system solid redox - reagent solution allows to perform the general theoretical approach to research and to obtain new results on kinetics and mechanism of interaction of redox with oxidants.
[en] The reduction mechanism of Th"4"+|Th couple in LiCl-KCl eutectic at inert and cadmium electrodes was studied in the temperature range 698-798 K using electrochemical techniques such as cyclic voltammetry, open circuit chronopotentiometry (OCP) and electrochemical impedance spectroscopy (EIS). While there was only cathodic peak associated with a single-step four electron transfer for the reduction of Th"4"+ at inert electrode, two cathodic peaks were observed at cadmium electrode, associated with under-potential deposition of thorium due to formation of ThCd_1_1 and ThCd_5. Impedance data were measured at different potentials at inert and cadmium electrodes were fitted to equivalent circuits comprising of solution and charge transfer resistance, diffusional component and double layer capacitance elements. The heterogeneous rate constant for the charge transfer process of thorium reduction was also estimated from the impedance data. (author)
[en] Core@shell nanocrystals (NCs) have been widely explored for oxygen reduction reaction (ORR). In this work, monodisperse PdCu@PtCu NCs with various shell thicknesses and compositions have been synthesized through a two-step protocol. As-synthesized PdCu@PtCu core@shell catalysts show enhanced specific activities (SAs) and mass activities (MAs) towards ORR. When PdCu/PtxCuy (core/shell) atomic ratio and Pt/Cu (x/y) ratio both reach 1/1, the core@shell catalyst exhibits the highest SA and MA (normalized with total mass of Pt and Pd). It is also found that the core@shell catalysts show drastically enhanced stability compared with pure PtCu alloy catalyst. It is proposed that both the activity and stability enhancements can be ascribed to the electronic interaction or charge transfer between Pd atoms (in core) and the shell elements. This work demonstrates a new family of core@shell catalysts that can be potentially used as cathode electro-catalysts in fuel cells.
[en] PEDOT:PSS-modified GC (PEDOT:PSS/GC) electrode shows enhanced electrocatalytic activity for Pu(IV)/Pu(III) redox couple in sulphuric acid solution compared to GC, Au and Pt electrodes. (author)
[en] Atomic-scale structures of oxygen reduction reaction (ORR) active sites in non-platinum group metal (non-PGM) catalysts, made from pyrolysis of carbon, nitrogen, and transition-metal (TM) precursors have been the subject of continuing discussion in the fuel cell electrocatalysis research community. Quantum chemical modeling is one path forward for understanding of these materials and how they catalyze the ORR. We here demonstrate through literature examples of how such modeling can be used to better understand non-PGM ORR active site relative stability and activity and how such efforts can also aid in the interpretation of experimental signatures produced by these materials.
[en] A simple and effective method is presented for producing light-emitting porous silicon (PSi). A thin (d<10 nm) layer of Au, Pt, or Au/Pd is deposited on the (100) Si surface prior to immersion in a solution of HF and H2O2. Depending on the type of metal deposited and Si doping type and doping level, PSi with different morphologies and light-emitting properties is produced. PSi production occurs on the time scale of seconds, without electrical current, in the dark, on both p- and n-type Si. Thin metal coatings facilitate the etching in HF and H2O2, and of the metals investigated, Pt yields the fastest etch rates and produces PSi with the most intense luminescence. A reaction scheme involving local coupling of redox reactions with the metal is proposed to explain the metal-assisted etching process. The observation that some metal remains on the PSi surface after etching raises the possibility of fabricating in situ PSi contacts
[en] A unique approach has been developed to probe the non-PGM catalyst active site for the Oxygen Reduction Reaction (ORR) for PEMFCs. Iron based functionalities have been engineered into a variety of catalysts to evaluate their impact on activity for the ORR. A series of high surface area catalysts were synthesized and the impact of the chemical structure on the electrochemical and electrocatalytic properties was investigated. Elemental and surface analyses of the prepared catalysts reveal the incorporation of iron in a targeted and controlled manner. A high surface area framework catalyst was prepared that shows exceptional activity, comparable to state-of-the-art materials. The results of this research project provided critical seed data for the newly awarded ElectroCat project, which focuses on rationally designed framework catalysts for the oxygen reduction reaction.