Strain Influences the Hydrogen Evolution Activity and Absorption Capacity of Palladium.

Strain engineering can increase the activity and selectivity of an electrocatalyst. Tensile strain is known to improve the electrocatalytic activity of palladium electrodes for reduction of carbon dioxide or dioxygen, but determining how strain affects the hydrogen evolution reaction (HER) is complicated by the fact that palladium absorbs hydrogen concurrently with HER. We report here a custom electrochemical cell, which applies tensile strain to a flexible working electrode, that enabled us to resolve how tensile strain affects hydrogen absorption and HER activity for a thin film palladium electrocatalyst.

Correlating cobalt redox couples to photovoltage in the dye-sensitized solar cell.

We report a series of structurally analogous cobalt mediators related to [Co-bpy]Z (bpy = 2,2'-bipyrimidine, Z = 2+ or 3+) to demonstrate a linear relationship between the redox potential of the Co(iii/ii)-based redox couple (Emed) and open-circuit voltage (VOC) of the DSSC. The Emed values vary from 0.42 to 1.

Kinetics teach that electronic coupling lowers the free-energy change that accompanies electron transfer.

Electron-transfer theories predict that an increase in the quantum-mechanical mixing (H) of electron donor and acceptor wavefunctions at the instant of electron transfer drives equilibrium constants toward unity. Kinetic and equilibrium studies of four acceptor-bridge-donor (A-B-D) compounds reported herein provide experimental validation of this prediction. The compounds have two redox-active groups that differ only by the orientation of the aromatic bridge: a phenyl-thiophene bridge (p) that supports strong electronic coupling of H > 1,000 cm; and a xylyl-thiophene bridge (x) that prevents planarization and decreases H < 100 cm without a significant change in distance.

Kinetic pathway for interfacial electron transfer from a semiconductor to a molecule.

Molecular approaches to solar-energy conversion require a kinetic optimization of light-induced electron-transfer reactions. At molecular-semiconductor interfaces, this optimization has previously been accomplished through control of the distance between the semiconductor donor and the molecular acceptor and/or the free energy that accompanies electron transfer. Here we show that a kinetic pathway for electron transfer from a semiconductor to a molecular acceptor also exists and provides an alternative method for the control of interfacial kinetics.

A combined computational and spectroelectrochemical study of platinum-bridged bis-triarylamine systems.

The character of the electronic transitions in the ultraviolet-visible-near infrared (UV-vis-NIR) spectra of platinum-bis(alkynyl) bridged, bis-triarylamine mixed-valence systems trans-[Pt(C≡CC6H4NAr2)2 (PR3)2](n+) (R = ethyl, Ar = C6H4CH3-4 (1) or C6H4OCH3-4 (2); R = Ph, Ar = C6H4CH3-4 (3) or C6H4OCH3-4 (4), n = 0, 1, 2) has been determined from a combination of spectroscopic measurement and density functional theory calculations. The hybrid functional BLYP35 in combination with a suitable solvent model (i.e.

Refining the interpretation of near-infrared band shapes in a polyynediyl molecular wire.

Spinning to improve (band) shape: A blend of theoretical and experimental work demonstrates that the rotational conformation of mixed-valence complexes influences the low-energy (NIR) transitions in such molecules. Interpretations of the NIR band shapes are presented.

Ruthenium(II) complexes bearing a naphthalimide fragment: a modular dye platform for the dye-sensitized solar cell.

Cycloruthenated complexes of the type [Ru(II)(N^N)2(C^N)](+) (N^N = substituted 2,2'-bipyridine; C^N = substituted 3-(2'-pyridyl)-1,8-naphthalimide ligand) are shown to generate high power conversion efficiencies (PCEs) in the dye-sensitized solar cell (DSSC). It is shown that substitution of the pyridine ring of the C^N ligand with conjugated groups can enhance molar absorption extinction coefficients, while the electron density imparted on the metal center is alleviated by the 1,8-naphthalimide fragment. This latter feature maintains a Ru(III)/Ru(II) redox couple more positive than 0.

Stabilization of ruthenium sensitizers to TiO2 surfaces through cooperative anchoring groups.

Cooperative binding of a bis(tridentate) ruthenium(II) complex to a TiO(2) surface through carboxylate and phosphonate groups is demonstrated to be an effective method for achieving a robust anchoring motif in aqueous media while maintaining charge transfer from the dye into the semiconductor. The realization of these complementary goals has broad implications for solar cells and (photo)electrocatalytic schemes.

Modification of electrode surfaces by self-assembled monolayers of thiol-terminated oligo(phenyleneethynylene)s.

The wire-like properties of four S-(4-{2-[4-(2-phenylethynyl)phenyl]ethynyl}phenyl) thioacetate derivatives, PhC≡CC(6)H(4)C≡CC(6)H(4)SAc (1), H(2)NC(6)H(4)C≡CC(6)H(4)C≡CC(6)H(4)SAc (2), PhC≡CC(6)H(2)(OMe)(2)C≡CC(6)H(4)SAc (3) and AcSC(6)H(4)C≡CC(6)H(4)C≡CC(6)H(4)SAc (4) (Figure 1), all of which possess a high degree of conjugation along the oligo(phenyleneethynylene) (OPE) backbone, were investigated as self-assembled monolayers (SAMs) on gold and platinum electrodes by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The redox probe [Fe(CN)(6)](4)(-) was used in both the CV and impedance experiments. The results indicate that the thiolates derived from thioacetate-protected precursor molecules 1 and 2 form well-ordered monolayers on a gold electrode, whereas SAMs derived from 3 and 4 exhibit randomly distributed pinholes.

Directionally oriented LB films of an OPE derivative: assembly, characterization, and electrical properties.

Langmuir films have been fabricated from 4-[4'-(4''-thioacetyl-phenyleneethynylene)-phenyleneethynylene]-aniline (NOPES) after cleavage of the thioacetyl protecting group. Characterization by surface pressure vs area per molecule isotherms and Brewster angle microscopy reveal the formation of a high quality monolayer at the air-water interface. One layer Langmuir-Blodgett (LB) films were readily fabricated by the transfer of the NOPES Langmuir film onto solid substrates.

The electronic structures of diruthenium complexes containing an oligo(phenylene ethynylene) bridging ligand, and some related molecular structures.

The complexes [{Cp'(L(2))Ru}C≡CC(6)H(4)C≡CC(6)H(2)(OMe)(2)C≡CC(6)H(4)C≡C{Ru(L(2))Cp'}](L(2) = (PPh(3))(2), Cp' = Cp; L(2) = dppe, Cp' = Cp*) in which the metal centres are bridged by an oligomeric phenylene ethynylene (OPE) ligand have been prepared and the electronic structure of these representative ruthenium-capped OPEs investigated using a combination of electrochemical, UV-vis-NIR and IR spectroelectrochemical methods, and DFT-based calculations. The diruthenium complexes are oxidised to the thermodynamically stable dications [Cp'Ru(L(2))C≡CC(6)H(4)C≡CC(6)H(2)(OMe)(2)C≡CC(6)H(4)C≡CRu(L(2))Cp'](2+), which on the basis of the spectroelectrochemical and computational results can be described in terms of two non-interacting Ru(C≡CAr)(L(2))Cp' moieties. X-ray structures of the oligophenyleneethynylene HC≡CC(6)H(4)C≡CC(6)H(2)(OMe)(2)C≡CC(6)H(4)C≡CH, the bis(gold) complex Ph(3)PAuC≡CC(6)H(4)C≡CC(6)H(2)(OMe)(2)C≡CC(6)H(4)C≡CAuPPh(3) and the precursor 1-ethynyl-4-(trimethylsilylethynyl)benzene are also reported.