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New Paper – Kinetic Evidence that the Solvent Barrier for Electron Transfer is Absent in the Electric Double Layer

Classical capacitance studies have revealed that the first layer of water present at an aqueous metal-electrolyte interface has a die-lectric constant less than 1/10th that of bulk water. Modern theory indicates that under such solvent conditions the barrier for elec-tron … Continued

New Paper – Abrupt degenerately-doped silicon nanowire tunnel junctions

The presence of narrow, degenerately-doped axial silicon nanowire (SiNW) p–n junctions via off-axis electron holography (EH) has been confirmed. SiNWs were grown via the vapor-solid-liquid (VLS) mechanism using gold (Au) as the catalyst, silane (SiH4 ), diborane (B2H6 ) and phosphine (PH3 ) as the … Continued

New Paper – Kinetics of the Trans Effect in Ruthenium Complexes Provide Insight into the Factors that Control Activity and Stability in CO2 Electroreduction

Comparative kinetic studies of a series of new ruthenium complexes provide a platform for understanding how strong trans effect ligands and redox-active ligands work together to enable rapid electrochemical CO2 reduction at moderate overpotential. After synthesizing isomeric pairs of ruthenium … Continued

New Paper ‒ Cation Effects in p-Type Dye Sensitized Solar Cells

The performance of dye sensitized solar cells (DSSCs) depends on the properties and interactions of three fundamental components: the semiconductor, chromophore, and electrolyte. For the electrolyte, the dependence of DSSC performance on the identity and valence state of the spectator … Continued

New Paper ‒ BODIPY Dyes as Visible Light Absorber/Sensitizers on Semiconductor Oxide Surfaces

The synthesis, characterization, electrochemical and photophysical properties of the phosphonate-derivatized Carbazole (CBZ) and boron dipyrromethene (BODIPY) chromophores in the dyes, BODIPY(CBZ)2PO3H2 [8] and BODIPY(Tol)2PO3H2 [7], are described. The oxide-bound dyes have been explored as light absorbers in dye-sensitized photoelectrosynthesis cell … Continued

New Paper ‒ Electron Transfer Reorganization Energies in the Electrode–Electrolyte Double Layer

The total reorganization energy, λ, for interfacial electron transfer, ET, from a conductive electrode to redox-active molecules at fixed positions within the electric double layer, EDL, has been determined experimentally. Conductive indium–tin-oxide (ITO, In2O3:Sn) mesoporous films were functionalized with 4-[N,N-di(p-tolyl)-amino]benzylphosphonic … Continued

New Paper ‒ Self-Assembled Chromophore/Catalyst Bilayer for Water Oxidation in a Dye-Sensitized Photoelectrosynthesis Cell

A new approach is described for the preparation of water oxidation photoanodes in a Dye-Sensitized Photoelectrosynthesis Cell (DSPEC) for water splitting. It is based on a chromophore (C) – catalyst (Cat) assembly prepared by a self-assembled bilayer (SAB) on a … Continued

New Paper ‒ Factors that Control the Direction of Excited State Electron Transfer at Dye-Sensitized Oxide Interfaces

Molecular excited states at conductive and semiconductive interfaces were found to transfer an electron to the oxide (injection) or accept an electron from the oxide (hole transfer). The direction of this electron transfer was determined by the metal oxide electronic … Continued

New Paper ‒ A stable dye-sensitized photoelectrosynthesis cell mediated by a NiO overlayer for water oxidation

In the development of photoelectrochemical cells for water splitting or CO2 reduction, a major challenge is O2 evolution at photoelectrodes that, in behavior, mimic photosystem II. At an appropriate semiconductor electrode, a water oxidation catalyst must be integrated with a visible … Continued

New Paper ‒ Electron Localization & Transport in SnO2/TiO2 Mesoporous Thin Films

A study of SnO2/TiO2 core/shell films was undertaken to investigate the influence of shell thickness and post deposition sintering on electron localization and transport properties. Electrochemical reduction of the materials resulted in the appearance of a broad visible –near IR … Continued

New Paper ‒ Atomic Layer Deposition of SnOx onto Mesoporous, Nanocrsytalline TiO2 and SnO2 Thin Films

The atomic layer deposition of tetrakisdimethylamidotin(IV) and water on mesoporous thin films of nanocrystalline anatase TiO2, rutile SnO2, and rutile TiO2 was investigated. For all deposition conditions tested, highly oxygen deficient coatings were created, and purge time and temperature were … Continued

New Paper ‒ Proton-Coupled Electron Transfer in Water Oxidation Catalysis

The reorganization energy, λ, for interfacial electron transfer (ET) and for proton-coupled electron transfer (PCET) between a water oxidation catalyst and a conductive In2O3:Sn (ITO) oxide were extracted from kinetic data by application of Marcus–Gerischer theory. Specifically, light excitation of … Continued

New Paper ‒ Modeling Electron Injection at Semiconductor-Molecule Interfaces

Excited electron transfer across semiconductor-molecule heterogeneous interfaces is central to various future electronic and optoelectronic devices. At the same time, first-principles modeling of such dynamical processes remains as a great challenge in theoretical chemistry and condensed matter physics for developing … Continued

New Paper ‒ Molecular Photoelectrode for Water Oxidation Inspired by Photosystem II

In artificial photosynthesis, the sun drives water splitting into H2 and O2 or converts CO2 into a useful form of carbon. In most schemes, water oxidation is typically the limiting half-reaction. Here, we introduce a molecular approach to the design … Continued

New Paper ‒ Trans Effect in Electrocatalytic CO2 Reduction

A comprehensive mechanistic study of electrocatalytic CO2 reduction by ruthenium 2,2′:6′,2″-terpyridine (tpy) pyridyl-carbene catalysts reveals the importance of stereochemical control to locate the strongly donating N-heterocyclic carbene ligand trans to the site of CO2 activation.  Computational studies were undertaken to … Continued

New Paper ‒ A Donor-Chromophore-Catalyst Assembly for Solar CO2 Reduction

This paper describes the preparation and characterization of a photocathode assembly for CO2 reduction to CO in 0.1M LiClO4 acetonitrile. The assembly was formed on 1.0 µm thick mesoporous films of NiO using a layer-by-layer procedure based on Zr(IV)-phosphonate bridging … Continued

New Review ‒ Halide Photoredox Chemistry

Halide photoredox chemistry is of both practical and fundamental interest. Practical applications have largely focused on solar energy conversion with hydrogen gas, through HX splitting, and electrical power generation, in regenerative photoelectrochemical and photovoltaic cells. On a more fundamental level, … Continued

New Paper ‒ Light-driven Water Oxidation on a Mesoporous Double-Shell Electrode

A mesoporous atomic layer deposition (ALD) double-shell electrode, Al2O3 (insulating core)//ALD ZnO|ALD TiO2, on a fluorine-doped tin oxide (FTO) conducting substrate was explored for a photoanode assembly, FTO//Al2O3 (insulating core)//ALD ZnO|ALD TiO2|–chromophore–catalyst, for light-driven water oxidation. Photocurrent densities at photoanodes based on … Continued

New Paper ‒ Decoherence in Hot Electron Relaxation within Fluorinated Silicon Quantum Dots

Surface passivation with fluorine atoms results in a significant slow down of hot electron relaxation because there exist particular electronic states that retain the hot electron for an extended time, and the relaxation time scale is largely influenced by shuttling … Continued

New Paper ‒ Simultaneous Electrosynthesis of Syngas and an Aldehyde

A tandem cell for artificial photosynthesis with CO2 and water as the oxidants and an organic alcohol as the reductant is described. The use of molecular catalysts with high activity and selectivity, in an appropriate cell configuration, leads to electrochemical reduction … Continued

New Paper ‒ A Silane-Derivatized Ru(II) Catalyst for Water Oxidation

The silane-derivatized catalyst, Ru(bda)(L)2 (bda = 2,2′-bipyridine-6,6′-dicarboxylate, L = 4-(6-(triethoxysilyl)hexyl)pyridine), is stabilized on metal oxide electrode surfaces over an extended pH range. It maintains its reactivity on the electrode surface toward electrochemical oxidation over a wide range of conditions. On … Continued

New Paper ‒ A Charge‐Separated State that Lives for Almost a Second

Transparent conductive oxides (TCOs) are widely-used commercially available materials for opto‐electronic applications, yet have received very little attention for dye‐sensitization applications. This paper reports that mesoporous thin films of conductive indium‐doped tin oxide (ITO) nanocrystallites support long‐lived charge separation with … Continued

New Review ‒ Carbon Dioxide Electroreduction

The development of molecular organometallic electrocatalysts for the reduction of carbon dioxide (CO2) is reviewed. Organometallic complexes are a promising subset of the many catalysts capable of electrochemical reduction of carbon dioxide to organic small molecules such as carbon monoxide (CO), formate (HCO2−), and oxalate (C2O42−). The carbon-based supporting ligands of organometallic complexes … Continued

New Paper ‒ Optimization of Photocatalyst Reduction Potentials for Dye-Sensitized HBr Splitting

Dye-sensitized bromide oxidation was investigated using a series of  ruthenium polypyridyl photocatalysts anchored to SnO2/TiO2 core/shell mesoporous thin films through 2,2’-bipyridine-4,4’-diphosphonic acid anchoring groups. The ground- and excited-state reduction potentials were tuned over 500 mV by the introduction of electron-withdrawing … Continued

New Paper ‒ Stabilized Photoanodes for Water Oxidation

Stabilized photoanodes for light-driven water oxidation were prepared on nanoparticle core/shell electrodes with surface-stabilized donor–acceptor chromophores, a water oxidation catalyst, and an electron-transfer mediator. For the electrode, fluorine-doped tin oxide FTO|SnO2/TiO2|-Org1-|1.1 nm Al2O3|-RuP2+-WOC (water oxidation catalyst) with Org1 (1-cyano-2-(4-(diphenylamino)phenyl)vinyl)phosphonic acid), … Continued

New Paper ‒ Photocatalytic Water Oxidation by a π-Conjugated Chromophore-Catalyst Assembly

The organic chromophore, 2,2′-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis(thiophene-3-carboxylic acid), was prepared and investigated along with metal complex [Ru(bda)(pyP)2] (bda = 2,2’-bipyridine-6,6’-dicarboxylate; pyP = 3-(pyridine-4-yloxy)propyl)phosphonic acid), for light-driven water splitting in dye-sensitized photoelectrochemical cells. The resulting co-loaded organic chromophore plus catalyst surface assembly was evaluated … Continued

New Paper ‒ Completing a Charge Transport Chain for Artificial Photosynthesis

A ruthenium polypyridyl chromophore with electronically isolated triarylamine substituents models the role of tyrosine in the electron transport chain in photosystem II. When bound to the surface of a TiO2 electrode, electron injection from a Ru(II) Metal-to-Ligand Charge Transfer (MLCT) excited … Continued

New Paper ‒ Catalytic Interconversion

Surface catalytic interconversion of hydroquinone and 1,4-benzoquinone occur at a fluorine-doped tin oxide electrode (FTO) modified by the addition of the surface-bound couple, [Os(bpy)2((4,4’-PO3H2)2bpy)]3+/2+. Significant rate enhancements are observed with added solution buffers – phosphate, acetate, and citrate – and … Continued

New Paper ‒ Stability of Phosphonate-Derivatized Sensitizers on Metal Oxide Surfaces

A series of Ru(II) polypyridyl complexes were evaluated under electrochemically oxidative conditions, which generates the Ru(III) oxidation state and mimics the harsh conditions in dye-sensitized solar cells, to develop fundamental insights into the factors governing molecular sensitizer surface stability. Results … Continued

New Paper ‒ Interfacial Dynamics

Interfacial dynamics following photoexcitation of a water oxidation assembly on nanocrystalline TiO2 electrodes have been investigated. Transient absorption measurements reveal that electron injection occurs with high efficiency but that hole transfer to the catalyst, which occurs on the electrochemical time … Continued