Magnetic Field Enhanced Cobalt Iridium Alloy Catalyst for Acidic Oxygen Evolution Reaction.

Magnetic field mediated magnetic catalysts provide a powerful pathway for accelerating their sluggish kinetics toward the oxygen evolution reaction (OER) but remain great challenges in acidic media. The key obstacle comes from the production of an ordered magnetic domain catalyst in the harsh acidic OER. In this work, we form an induced local magnetic moment in the metallic Ir catalyst via the significant 3d-5d hybridization by introducing cobalt dopants.

Understanding molecular and electrochemical charge transfer: theory and computations.

Electron, proton, and proton-coupled electron transfer (PCET) are crucial elementary processes in chemistry, electrochemistry, and biology. We provide here a gentle overview of retrospective and currently developing theoretical formalisms of chemical, electrochemical and biological molecular charge transfer processes, with examples of how to bridge electron, proton, and PCET theory with experimental data. We offer first a theoretical minimum of molecular electron, proton, and PCET processes in homogeneous solution and at electrochemical interfaces.

Effect of a Au underlayer on outer-sphere electron transfer across a Au/graphene/electrolyte interface.

The effect of a gold underlayer on the outer-sphere non-adiabatic electron transfer on a graphene surface is investigated theoretically using both periodic and cluster DFT calculations. We propose a model that describes the alignment of energy levels and charge redistribution at the metal/graphene/redox electrolyte interface. Model calculations were performed for the [Fe(CN)] and [Ru(NH)] redox couples.

Electronic Spillover from a Metallic Nanoparticle: Can Simple Electrochemical Electron Transfer Processes Be Catalyzed by Electronic Coupling of a Molecular Scale Gold Nanoparticle Simultaneously to the Redox Molecule and the Electrode?

Electrochemical electron transfer (ET) of transition metal complexes or redox metalloproteins can be catalyzed by more than an order of magnitude by molecular scale metallic nanoparticles (NPs), often rationalized by concentration enhancement of the redox molecules in the interfacial region, but collective electronic AuNP array effects have also been forwarded. Using DFT combined with molecular electrochemical ET theory we explore here whether a single molecular scale Au nanocluster (AuC) between a Au (111) surface and the molecular redox probe ferrocene/ferricinium (Fc/Fc) can trigger an ET rate increase. Computational challenges limit us to AuCs ( up to 147), which are smaller than most electrocatalytic AuCs studied experimentally.

Chemistry of cysteine assembly on Au(100): electrochemistry, in situ STM and molecular modeling.

Cysteine (Cys) is an essential amino acid with a carboxylic acid, an amine and a thiol group. We have studied the surface structure and adsorption dynamics of l-cysteine adlayers on Au(100) from aqueous solution using electrochemistry, high-resolution electrochemical scanning tunnelling microscopy (in situ STM), and molecular modelling. Cys adsorption on this low-index Au-surface has been much less studied than Cys adsorption on Au(111)- and Au(110)-electrode surfaces.

Chiral Selectivity in Inter-reactant Recognition and Electron Transfer of the Oxidation of Horse Heart Cytochrome c by Trioxalatocobaltate(III).

Outer-sphere electron transfer (ET) between optically active transition-metal complexes and either other transition-metal complexes or metalloproteins is a prototype reaction for kinetic chirality. Chirality as the ratio between bimolecular rate constants of two enantiomers mostly amounts to 1.05-1.

When do defectless alkanethiol SAMs in ionic liquids become penetrable? A molecular dynamics study.

Molecular dynamics simulations were performed to address the permeability of defectless alkanethiol self-assembled monolayers (SAMs) on charged and uncharged Au(111) surfaces in 1-butyl-3-methylimidazolium ([bmim][BF4]) room-temperature ionic liquid (IL). We demonstrate that ionic permeation into the monolayer does not start until a critical surface charge density value is attained (both for positive and negative surface charges). The free energy barrier for the permeation of IL components is shown to include nearly equal contributions from ion desolvation and the channel formation in the dense monolayer.

DNA bases assembled on the Au(110)/electrolyte interface: a combined experimental and theoretical study.

Among the low-index single-crystal gold surfaces, the Au(110) surface is the most active toward molecular adsorption and the one with fewest electrochemical adsorption data reported. Cyclic voltammetry (CV), electrochemically controlled scanning tunneling microscopy (EC-STM), and density functional theory (DFT) calculations have been employed in the present study to address the adsorption of the four nucleobases adenine (A), cytosine (C), guanine (G), and thymine (T), on the Au(110)-electrode surface. Au(110) undergoes reconstruction to the (1 × 3) surface in electrochemical environment, accompanied by a pair of strong voltammetry peaks in the double-layer region in acid solutions.

Interfacial bond-breaking electron transfer in mixed water-ethylene glycol solutions: reorganization energy and interplay between different solvent modes.

We explore solvent dynamics effects in interfacial bond breaking electron transfer in terms of a multimode approach and make an attempt to interpret challenging recent experimental results (the nonmonotonous behavior of the rate constant of electroreduction of S2O8(2-) from mixed water-EG solutions when increasing the EG fraction; see Zagrebin, P.A. et al.

A spectroscopic and computational study of Al(III) complexes in cryolite melts: Effect of cation nature.

Lithium, sodium and potassium cryolite melts are probed by Raman spectroscopy in a wide range of the melt composition. The experimental data demonstrate a slight red shift of main peaks and a decrease of their half-widths in the row Li(+), Na(+), K(+). Quantum chemical modelling of the systems is performed at the density functional theory level.

Modeling and computations of the intramolecular electron transfer process in the two-heme protein cytochrome c(4).

The di-heme protein Pseudomonas stutzeri cytochrome c(4) (cyt c(4)) has emerged as a useful model for studying long-range protein electron transfer (ET). Recent experimental observations have shown a dramatically different pattern of intramolecular ET between the two heme groups in different local environments. Intramolecular ET in homogeneous solution is too slow (>10 s) to be detected but fast (ms-μs) intramolecular ET in an electrochemical environment has recently been achieved by controlling the molecular orientation of the protein assembled on a gold electrode surface.

Quinones electrochemistry in room-temperature ionic liquids.

The two-step electrochemical reduction of tetrachloro-1,2-benzoquinone (chloranil), 2-methyl-1,2-benzoquinone (toluquinone), and 9,10-anthraquinone in two room-temperature ionic liquids is addressed by means of voltammetry on a platinum electrode. For the subsequent quinone/radical anion (Q/Q(•-)) and radical anion/dianion (Q(•-)/Q(2-)) redox reactions, the experimental data on formal potentials in 1-butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BF(4)]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([C(4)mim][PF(6)]) and literature data for the same reactants in various aprotic molecular solvents are considered in the framework of a common potential sequence (Fc(+)/Fc scale) and compared with solvation energies computed at various levels. For the Q/Q(•-) couple, the agreement appeared to be satisfactory when solvation is described at the polarized continuum model (PCM) level.

A spectroscopic and computational study of Al(III) complexes in sodium cryolite melts: ionic composition in a wide range of cryolite ratios.

The structure of sodium cryolite melts was studied using Raman spectroscopy and quantum chemical calculations performed at the density functional theory level. The existence of bridged forms in the melts was argued first from the analysis of experimental Raman spectra. In the quantum chemical modelling emphasis was put on the construction of potential energy surfaces describing the formation/dissociation of certain complex species.

Dynamic solvent effects in electrochemical kinetics: indications for a switch of the relevant solvent mode.

The influence of solvent dielectric relaxation on the rate of electron transfer (ET) at an electrochemical interface is addressed using both experiment and model calculations. Water-ethylene glycol (EG) mixtures were chosen as the solvent because their optical permittivity remains practically constant over the entire composition range. This allows observation of the dynamic solvent effect with a very minor interference from the static solvent properties (being typically of opposite sign).

Interplay between solvent effects of different nature in interfacial bond breaking electron transfer.

Solvent dynamics effects on electroreduction of peroxodisulphate anion on mercury electrode (a typical bond breaking electron transfer reaction) are explored in the framework of the Sumi-Marcus model. The reaction three-dimensional free energy surface is constructed using the Anderson model Hamiltonian. A new interpretation of short- and long-time survival times is presented as well.

Submolecular electronic mapping of single cysteine molecules by in situ scanning tunneling imaging.

We have used L-cysteine (Cys) as a model system to study the surface electronic structures of single molecules at the submolecular level in aqueous buffer solution by a combination of electrochemical scanning tunneling microscopy (in situ STM), electrochemistry including voltammetry and chronocoulometry, and density functional theory (DFT) computations. Cys molecules were assembled on single-crystal Au(110) surfaces to form a highly ordered monolayer with a periodic lattice structure of c(2x2) in which each unit contains two molecules; this conclusion is confirmed by the results of calculations based on a slab model for the metal surface. The ordered monolayer offers a platform for submolecular scale electronic mapping that is an issue of fundamental interest but remains a challenge in STM imaging science and surface chemistry.

Medium and interfacial effects in the multistep reduction of binuclear complexes with robson-type ligand.

We present a combined experimental and computational approach to the modeling and prediction of reactivity in multistep processes of heterogeneous electron transfer. The approach is illustrated by the study of a Robson-type binuclear complex (-Cu(II)-Cu(II)-) undergoing four-electron reduction in aqueous media and water-acetonitrile mixtures. The observed effects of solvent, pH, buffer capacity, and supporting electrolyte are discussed in the framework of a general reaction scheme involving two main routes; one of them includes protonation of intermediate species.

Binuclear Robson type Ni(ii) complex as a reactant supplementing our knowledge of the orientation effects in electrochemical kinetics.

The multistep reduction of a binuclear Ni(ii) Robson-type complex with a multidentate template-like organic ligand (formed from 4-tert-butyl-2,6-diformylphenol and 1,3-diaminopropane), Ni(2)L, is studied using the electron photoemission technique. The number of transferred electrons corresponding to a single reduction wave is found to be 8 per complex species. This value is attributed to both complete Ni(ii) reduction (with Ni metal formation) and ligand reduction.

Adsorption and in situ scanning tunneling microscopy of cysteine on Au(111): Structure, energy, and tunneling contrasts.

The amino acid L-cysteine (Cys) adsorbs in highly ordered (3 square root of 3 x 6) R30 degrees lattices on Au(111) electrodes from 50 mM ammonium acetate, pH 4.6. We provide new high-resolution in situ scanning tunneling microscopy (STM) data for the L-Cys adlayer.

Role of charge distribution in the reactant and product in double layer effects: construction of corrected Tafel plots.

The effect of charge distribution within Cr(III) and Eu(III) aquacomplexes on the kinetics of simple electron-transfer reactions at electrodes is considered. The construction of corrected Tafel plots using noninteger effective charges for the reactant and product estimated on the basis of quantum-chemical data was shown to be more reasonable than the traditional approach in which integer charges are assumed. The potential distribution near the electrode has been estimated both by the Gouy-Chapman model and from Monte Carlo simulations for 1-1 supporting electrolytes.