Theoretical insights into the effect of the overpotential on CO electroreduction mechanisms on Cu(111): regulation and application of electrode potentials from a CO coverage-dependent electrochemical model

2020 ◽  
Vol 22 (1) ◽  
pp. 62-73
Author(s):  
Lihui Ou ◽  
Junxiang Chen
Keyword(s):  
Electron Transfer ◽  
Antibonding Orbital ◽  
Electrode Potentials ◽  
Electrochemical Model

The electron transfer into the π antibonding orbital of CO leads to increasing overpotential and weaker CO bonding with the Cu surface.

Effect of Metal Modification to Carbon Paper Anodes on the Performance of Yeast-Based Microbial Fuel Cells Part Ι: In the Case without Exogenous Mediator

2013 ◽  
Vol 534 ◽  
pp. 76-81 ◽  
Author(s):  
Enas Taha Kasem ◽  
Takuya Tsujiguchi ◽  
Nobuyoshi Nakagawa
Keyword(s):  
Electron Transfer ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Thin Layer ◽  
Electrode Surface ◽  
Microbial Fuel Cells ◽  
Yeast Cells ◽  
Carbon Paper ◽  
Electrode Potentials ◽  
Different Thickness

Effect of modification of carbon paper with a thin layer of cobalt or gold on the performance of yeast-based microbial fuel cells was investigated. The modification was conducted by depositing Co or Au thin layer with different thickness, 5 nm and 30 nm, using a sputtering technique. The electrode performance was evaluated by measuring the electrode potentials and the fuel cell power output. The Co modification significantly increased the performance of the fuel cell, while the Au modification inhibited the performance. SEM observation indicated that the adhesion density of the yeast cells on the electrode surface was affected by the metals. It was confirmed that the electron transfer took place through the surface confined species at the mediatorless anode.

scholarly journals Molecular ordering at electrified interfaces: Template and potential effects

2014 ◽  
Vol 10 ◽  
pp. 2243-2254 ◽  
Author(s):  
Thanh Hai Phan ◽  
Klaus Wandelt
Keyword(s):  
Phase Transition ◽  
Electron Transfer ◽  
Self Assembly ◽  
Electrode Surface ◽  
Bone Structure ◽  
Scanning Tunneling ◽  
Cyclic Voltammogram ◽  
Tunneling Microscopy ◽  
Stripe Pattern ◽  
Electrode Potentials

A combination of cyclic voltammetry and in situ scanning tunneling microscopy was employed to examine the adsorption and phase transition of 1,1’-dibenzyl-4,4’-bipyridinium molecules (abbreviated as DBV2+) on a chloride-modified Cu(111) electrode surface. The cyclic voltammogram (CV) of the Cu(111) electrode exposed to a mixture of 10 mM HCl and 0.1 mM DBVCl2 shows three distinguishable pairs of current waves P1/P’1, P2/P’2, and P3/P’3 which are assigned to two reversible electron transfer steps, representing the reduction of the dicationic DBV2+ to the corresponding radical monocationic DBV+• (P1/P’1) and then to the uncharged DBV0 (P3/P’3) species, respectively, as well as the chloride desorption/readsorption processes (P2/P’2). At positive potentials (i.e., above P1) the DBV2+ molecules spontaneously adsorb and form a highly ordered phase on the c(p × √3)-precovered Cl/Cu(111) electrode surface. A key element of this DBV2+ adlayer is an assembly of two individual DBV2+ species which, lined up, forms a so-called “herring-bone” structure. Upon lowering the electrode potential the first electron transfer step (at P1) causes a phase transition from the DBV2+-related herring-bone phase to the so-called "alternating stripe" pattern built up by the DBV+• species following a nucleation and growth mechanism. Comparison of both observed structures with those found earlier at different electrode potentials on a c(2 × 2)Cl-precovered Cu(100) electrode surface enables a clear assessment of the relative importance of adsorbate–substrate and adsorbate–adsorbate interactions, i.e., template vs self-assembly effects, in the structure formation process of DBV cations on these modified Cu electrode surfaces.

Electronic propensity of Cu(II) versus Cu(I) sites in zeolites to activate NO — Spin- and orbital-resolved Cu–NO electron transfer

2013 ◽  
Vol 91 (7) ◽  
pp. 538-543 ◽  
Author(s):  
Mariusz Radoń ◽  
Paweł Kozyra ◽  
Adam Stępniewski ◽  
Jerzy Datka ◽  
Ewa Broclawik
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Lone Pair ◽  
Blue Shift ◽  
Open Shell ◽  
Minor Importance ◽  
Antibonding Orbital ◽  
Spin Manifolds ◽  
Copper Center ◽  
Nitrogen Lone Pair

Electronic factors responsible for the notable decline of NO activation by Cu(II) with respect to Cu(I) sites in zeolites are investigated within spin-resolved analysis of electron transfer channels between the copper center and the substrate. The results of natural orbitals for chemical valence (NOCV) charge transfer analysis for a minimal model of Cu(II) sites in zeolite ZSM-5 ({T1Cu}+ NO) are compared with those for Cu(I)–NO and referenced to an interaction of NO with bare Cu+ cations. The bonding of NO, which is an open-shell and non-innocent ligand, gives rise to a noticeable nondynamical correlation in the adduct with Cu(II) (reflected in a broken-symmetry solution obtained at the density functional theory (DFT) level). Four distinct components of electron transfer between the copper and NO are identified: (i) donation of an unpaired electron from the NO π∥* antibonding orbital to the Cu species, (ii) backdonation from copper d⊥ to the NO antibonding orbital, (iii) “covalent” donation from NO π∥ and Cu d∥ orbitals to the bonding region, and (iv) donation from the nitrogen lone pair to Cus,d. Large variations in channel identity and significance may be noted among studied systems and between spin manifolds: channel i is effective only in the bonding of NO with either a naked Cu+ cation or Cu(II) site. Channel ii comes into prominence only for the model of the Cu(I) site: it strongly activates the NO bond by populating antibonding π*, which weakens the N–O bond, in contrast to channel i depopulating the antibonding orbital and strengthening the N–O bond. Channels iii and iv, however, may contribute to the strength of the bonding between NO and copper, and are of minor importance for the activation of the NO bond. This picture perfectly matches the IR experiment: interaction with either Cu(II) sites or a naked Cu+ cation imposes a comparable blue-shift of NO stretching frequency, while the frequency becomes strongly red-shifted for a Cu(I) site in ZSM-5 due to enhanced π* backdonation.

Electrochemical aspects of leaching copper from chalcopyrite in ferric and cupric salt solutions

1981 ◽  
Vol 34 (1) ◽  
pp. 13 ◽  
Author(s):  
AJ Parker ◽  
RL Paul ◽  
GP Power
Keyword(s):  
Electron Transfer ◽  
Surface Film ◽  
Salt Solutions ◽  
Type Semiconductor ◽  
Transport Of Ions ◽  
Time Periods ◽  
Electrochemical Model ◽  
Kinetics Of ◽  
Natural Chalcopyrite ◽  
Comparable Time

Electrochemical aspects of semiconductors are used to interpret well established observations on the kinetics of leaching of chalcopyrite. The oxidation of this n-type semiconductor is dominated by a surface film which is thermally unstable and breaks down in CS2, acetone or acidified water, or under dry nitrogen, over comparable time periods. The film is thought to be a semiconductor metal-deficient polysulfide which slows transport of Cu+ and Fe2+ products, slows electron transfer to oxidants such as Fe3+ and Cu2+, and dramatically slows supply of holes and thus electron transfer from reduced species such as Fe2+ on corroding chalcopyrite. Thus the Fe3+/Fe2+ couple (especially as sulfate) is much less reversible on corroding chalcopyrite than on pyrite or platinum. The couples Cu2+/Cu+,I3-/I- and Fe(CN)63-/Fe(CN)64- are more reversible than Fe3+ /Fe2+ but all couples are much less reversible on chalcopyrite than on pyrite. A layer of sulfur forms on corroding chalcopyrite, but this is not the species which slows transport of ions and transfer of electrons. A mixture of Fe3+/Cu2+ chlorides is one of the more effective oxidants for CuFeS2 because of relatively fast electron transfer from corroding chalcopyrite to Cu2+ and oxidation of Cu+ by Fe3+. Catalysis by iodine and by inclusion of Ag2S or FeS2 in natural chalcopyrite is explained by the electrochemical model.

scholarly journals Resilience, Dynamics, and Interactions within a Model Multispecies Exoelectrogenic-Biofilm Community

2017 ◽  
Vol 83 (6) ◽  
Author(s):  
Anna Prokhorova ◽  
Katrin Sturm-Richter ◽  
Andreas Doetsch ◽  
Johannes Gescher
Keyword(s):  
Electron Transfer ◽  
Geobacter Sulfurreducens ◽  
Positive Interactions ◽  
Organic Substrates ◽  
Bioelectrochemical Systems ◽  
Mixed Species ◽  
Positive Interaction ◽  
Content Type ◽  
Electrode Potentials ◽  
The Individual

ABSTRACT Anode-associated multispecies exoelectrogenic biofilms are essential for the function of bioelectrochemical systems (BESs). The individual activities of anode-associated organisms and physiological responses resulting from coculturing are often hard to assess due to the high microbial diversity in these systems. Therefore, we developed a model multispecies biofilm comprising three exoelectrogenic proteobacteria, Shewanella oneidensis, Geobacter sulfurreducens, and Geobacter metallireducens, with the aim to study in detail the biofilm formation dynamics, the interactions between the organisms, and the overall activity of an exoelectrogenic biofilm as a consequence of the applied anode potential. The experiments revealed that the organisms build a stable biofilm on an electrode surface that is rather resilient to changes in the redox potential of the anode. The community operated at maximum electron transfer rates at electrode potentials that were higher than 0.04 V versus a normal hydrogen electrode. Current densities decreased gradually with lower potentials and reached half-maximal values at −0.08 V. Transcriptomic results point toward a positive interaction among the individual strains. S. oneidensis and G. sulfurreducens upregulated their central metabolisms as a response to cultivation under mixed-species conditions. G. sulfurreducens was detected in the planktonic phase of the bioelectrochemical reactors in mixed-culture experiments but not when it was grown in the absence of the other two organisms. IMPORTANCE In many cases, multispecies communities can convert organic substrates into electric power more efficiently than axenic cultures, a phenomenon that remains unresolved. In this study, we aimed to elucidate the potential mutual effects of multispecies communities in bioelectrochemical systems to understand how microbes interact in the coculture anodic network and to improve the community's conversion efficiency for organic substrates into electrical energy. The results reveal positive interactions that might lead to accelerated electron transfer in mixed-species anode communities. The observations made within this model biofilm might be applicable to a variety of nonaxenic systems in the field.

A light optical diffractometer for electron microscopical images operating in line

1978 ◽  
Vol 36 (1) ◽  
pp. 86-87
Author(s):  
P. Bonhomme ◽  
A. Beorchia
Keyword(s):  
Electron Microscopy ◽  
Electron Transfer ◽  
Electron Microscope ◽  
Image Converter ◽  
Coherent Light ◽  
Spatial Filters ◽  
Electron Image ◽  
Electron Microscopical ◽  
Working Parameters ◽  
Amorphous Part

We have already described (1.2.3) a device using a pockel's effect light valve as a microscopical electron image converter. This converter can be read out with incoherent or coherent light. In the last case we can set in line with the converter an optical diffractometer. Now, electron microscopy developments have pointed out different advantages of diffractometry. Indeed diffractogram of an image of a thin amorphous part of a specimen gives information about electron transfer function and a single look at a diffractogram informs on focus, drift, residual astigmatism, and after standardizing, on periods resolved (4.5.6). These informations are obvious from diffractogram but are usualy obtained from a micrograph, so that a correction of electron microscope parameters cannot be realized before recording the micrograph. Diffractometer allows also processing of images by setting spatial filters in diffractogram plane (7) or by reconstruction of Fraunhofer image (8). Using Electrotitus read out with coherent light and fitted to a diffractometer; all these possibilities may be realized in pseudoreal time, so that working parameters may be optimally adjusted before recording a micrograph or before processing an image.

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

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