scholarly journals Restructuring of an Ir(210) electrode surface by potential cycling

2014 ◽  
Vol 5 ◽  
pp. 1349-1356 ◽  
Author(s):  
Khaled A Soliman ◽  
Dieter M Kolb ◽  
Ludwig A Kibler ◽  
Timo Jacob
Keyword(s):  
Structural Changes ◽  
Electrochemical Behaviour ◽  
Surface Oxidation ◽  
Potential Cycling ◽  
Thermally Induced ◽  
Preferred Direction ◽  
Scanning Tunnelling ◽  
Tunnelling Microscopy ◽  
Voltammetric Peak

This study addresses the electrochemical surface faceting and restructuring of Ir(210) single crystal electrodes. Cyclic voltammetry measurements and in situ scanning tunnelling microscopy are used to probe structural changes and variations in the electrochemical behaviour after potential cycling of Ir(210) in 0.1 M H2SO4. Faceted structures are obtained electrochemically as a function of time by cycling at a scanrate of 1 V·s−1 between −0.28 and 0.70 V vs SCE, i.e., between the onset of hydrogen evolution and the surface oxidation regime. The electrochemical behaviour in sulfuric acid solution is compared with that of thermally faceted Ir(210), which shows a sharp characteristic voltammetric peak for (311) facets. Structures similar to thermally-induced faceted Ir(210) are obtained electrochemically, which typically correspond to polyoriented facets at nano-pyramids. These structures grow anisotropically in a preferred direction and reach a height of about 5 nm after 4 h of cycling. The structural changes are reflected in variations of the electrocatalytic activity towards carbon monoxide adlayer oxidation.

Growth of thin Mn films on W(110) studied by means of in-situ scanning tunnelling microscopy

1999 ◽  
Vol 432 (1-2) ◽  
pp. 8-20 ◽  
Author(s):  
M. Bode ◽  
M. Hennefarth ◽  
D. Haude ◽  
M. Getzlaff ◽  
R. Wiesendanger
Keyword(s):  
Scanning Tunnelling Microscopy ◽  
Scanning Tunnelling ◽  
Tunnelling Microscopy

Electron transfer at the cell–uranium interface in Geobacter spp.

2012 ◽  
Vol 40 (6) ◽  
pp. 1227-1232 ◽  
Author(s):  
Gemma Reguera
Keyword(s):  
Outer Membrane ◽  
Cell Envelope ◽  
Uranium Deposits ◽  
Oxide Reduction ◽  
Cellular Protection ◽  
Primary Mechanism ◽  
Redox Active ◽  
Scanning Tunnelling ◽  
Tunnelling Microscopy

The in situ stimulation of Fe(III) oxide reduction in the subsurface stimulates the growth of Geobacter spp. and the precipitation of U(VI) from groundwater. As with Fe(III) oxide reduction, the reduction of uranium by Geobacter spp. requires the expression of their conductive pili. The pili bind the soluble uranium and catalyse its extracellular reductive precipitation along the pili filaments as a mononuclear U(IV) complexed by carbon-containing ligands. Although most of the uranium is immobilized by the pili, some uranium deposits are also observed in discreet regions of the outer membrane, consistent with the participation of redox-active foci, presumably c-type cytochromes, in the extracellular reduction of uranium. It is unlikely that cytochromes released from the outer membrane could associate with the pili and contribute to the catalysis, because scanning tunnelling microscopy spectroscopy did not reveal any haem-specific electronic features in the pili, but, rather, showed topographic and electronic features intrinsic to the pilus shaft. Pili not only enhance the rate and extent of uranium reduction per cell, but also prevent the uranium from traversing the outer membrane and mineralizing the cell envelope. As a result, pili expression preserves the essential respiratory activities of the cell envelope and the cell's viability. Hence the results support a model in which the conductive pili function as the primary mechanism for the reduction of uranium and cellular protection in Geobacter spp.

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