Effect of CdS loading on the properties and photocatalytic activity of MoS nanosheets.

Molybdenum sulfide (MoS) and modified MoS with different percentages of CdS (10%, 30%, and 50% CdS@MoS) were successfully synthesized and characterized. The photocatalytic performance of the MoS and CdS@MoS was evaluated by degrading brilliant green (BG), methylene blue (MB), and rhodamine B (RhB) dyes under visible light irradiation. Amongst the synthesized photocatalysts, 50% CdS@MoS exhibited the highest photocatalytic activity, degrading 97.

Microwave-assisted synthesis of ZnS@CuInS for photocatalytic degradation of coloured and non-coloured pollutants.

Copper indium sulfide (CuInS) exhibits strong visible light absorption and thus has the potential for good photocatalytic activity; however, rapid charge recombination limits its practical usage. An intriguing strategy to overcome this issue is to couple CuInS with another semiconductor to form a heterojunction, which can improve the charge carrier separation and, hence, enhance the photocatalytic activity. In this study, photocatalysts comprising CuInS with a secondary CuS phase (termed CuInS) and CuInS loaded with ZnS (termed ZnS@CuInS) were synthesized via a microwave-assisted method.

Doped Ceria Nanomaterials: Preparation, Properties, and Uses.

Doping is a powerful strategy for enhancing the performance of ceria (CeO) nanomaterials in a range of catalytic, photocatalytic, biomedical, and energy applications. The present review summarizes recent developments in the doping of ceria nanomaterials with metal and non-metal dopants for selected applications. The most important metal dopants are grouped into s, p, d, and f block elements, and the relevant synthetic methods, novel properties, and key applications of metal doped ceria are collated and critically discussed.

Influence of metal salts (Al, Ca, and Mg) on the work function and hole extraction at carbon counter electrodes in perovskite solar cells.

Hole transport material-free carbon-based perovskite solar cells (HTM-free -PSCs) are recognized as a cost-effective and stable alternative to conventional perovskite solar cells. However, the significant energy level misalignment between the perovskite layer and the carbon counter electrode (CE) results in ineffective hole extraction and unfavorable charge recombination, which decreases the power conversion efficiency (PCE). Here, we report the introduction of metal salts (Al, Ca, and Mg) into graphite/carbon black (Gr/CB) CEs to modify the work function and enhance the hole selectivity of the CE.

Graphite/Carbon Black Counter Electrode Deposition Methods to Improve the Efficiency and Stability of Hole-Transport-Layer-Free Perovskite Solar Cells.

The interfacial compatibility between the graphite/carbon black composite counter electrode (Gr/CB CE) and the perovskite layer is a crucial determinant of the performance of the hole-transport-layer-free carbon-based perovskite solar cells, and judicious selection of the Gr/CB CE application method is essential for achieving an optimum contact. In this work, three different types of Gr/CB CEs application methods are investigated: (1) deposition of Gr/CB on the fluorine-doped tin oxide (FTO) substrate, followed by clamping to the perovskite layer, (2) direct deposition of Gr/CB onto the perovskite layer, and (3) deposition of Gr/CB onto the PbI precursor layer, followed by immersion in methylammonium iodide solution for the conversion of PbI to perovskite. The results revealed that Method 3 produced superior Gr/CB-perovskite contacts, resulting in up to 8.

Molybdenum Disulfide-Based Nanomaterials for Visible-Light-Induced Photocatalysis.

Visible-light-responsive photocatalytic materials have a multitude of important applications, ranging from energy conversion and storage to industrial waste treatment. Molybdenum disulfide (MoS) and its variants exhibit high photocatalytic activity under irradiation by visible light as well as good stability and recyclability, which are desirable for all photocatalytic applications. MoS-based materials have been widely applied in various fields such as wastewater treatment, environmental remediation, and organic transformation reactions because of their excellent physicochemical properties.

Synthesis of nanostructured β-Ni(OH)2 by electrochemical dissolution-precipitation and its application as a water oxidation catalyst.

A straightforward electrochemical dissolution-precipitation approach has been developed to synthesize nanostructured β-Ni(OH)2 powders (particle size 10-100 nm, specific surface area ∼100 m(2) g(-1)) from Ni metal anodes. The approach differs from existing electrochemical synthesis methods in that it predominantly results in bulk precipitation of nanoparticles, without significant film growth on either of the electrodes. Heat treatment of the as-synthesized β-Ni(OH)2 afforded NiO with mostly preserved nanostructure and very high specific surface area (≤100 m(2) g(-1), depending on calcination temperature).

A redox-flow electrochromic window.

A low-cost electrochromic (EC) window based on a redox-flow system that does not require expensive transparent conductive oxide (TCO) substrates is introduced and demonstrated for the first time. An aqueous I3–/I– redox electrolyte is used in place of a TCO to oxidize/reduce a molecular layer of an EC triphenylamine derivative that is anchored to a mesoporous TiO2 scaffold on the inner faces of a double-paned window. The redox electrolyte is electrochemically oxidized/reduced in an external two-compartment cell and circulated through the window cavity using an inexpensive peristaltic pump, resulting in coloration or decoloration of the window due to reaction of the redox solution with the triphenylamine derivative.

Determination of sensitizer regeneration efficiency in dye-sensitized solar cells.

Regeneration of the sensitizing dye in dye-sensitized solar cells (DSCs) is frequently studied using the transient absorption (TA) technique. However, TA measurements are generally not performed using complete DSCs at the maximum power point (MPP) on the current-voltage (j-V) characteristic, and the electron concentration in the nanocrystalline TiO2 films used in these devices is often not well characterized, which may lead to results that are not relevant to actual solar cell operation. Here, dye regeneration kinetics were studied at the MPP and at open circuit (where interpretation of results is simpler) in DSCs employing a "robust" nonvolatile 3-methoxypropionitrile-based electrolyte solution.

Efficient dye-sensitized solar cells using a tetramethylthiourea redox mediator.

An organic redox couple tetramethylthiourea/tetramethylformaminium disulfide (TMTU/TMFDS(2+) ) is evaluated in dye-sensitized solar cells in conjunction with a series of indoline and ruthenium-based dyes. Of these, devices with indoline dye D205 show the best performance, with an optimized power conversion efficiency of 7.6 % under AM 1.

Significant performance improvement in dye-sensitized solar cells employing cobalt(III/II) tris-bipyridyl redox mediators by co-grafting alkyl phosphonic acids with a ruthenium sensitizer.

Efficiencies of up to 8.5% for dye-sensitized solar cells employing a ruthenium dye with a cobalt complex redox mediator have been achieved, by using octadecylphosphonic acid (OPA) as a coadsorbent. This success is due to improved electron injection and reduced recombination.

Conformal growth of nanocrystalline CdX (X = S, Se) on mesoscopic NiO and their photoelectrochemical properties.

Semiconductor-sensitized NiO photocathodes have been fabricated by successive ionic-layer adsorption and reaction (SILAR) deposition of CdS, CdSe and cascaded CdS/CdSe onto mesoscopic NiO films. Detailed morphological and structural characterization reveals that the growth of CdS and CdSe on mesoscopic NiO electrodes results in the formation of crystalline and conformal layers under ambient conditions. With a polysulfide redox electrolyte and a Pt counter electrode, CdX (X = S and Se)-sensitized p-NiO solar cells operating in a photocathodic mode are unambiguously demonstrated when NiO blocking layers are used, which are critical to prevent anodic photocurrent due to electron injection from CdX into the SnO2:F substrate.

Heterogeneous electron transfer from dye-sensitized nanocrystalline TiO2 to [Co(bpy)3]3+: insights gained from impedance spectroscopy.

Dye-sensitized solar cells (DSCs) employing the [Co(bpy)3](3+/2+) redox mediator have recently attained efficiencies in excess of 12%, increasing the attractiveness of DSCs as an alternative to conventional photovoltaics. Heterogeneous electron transfer from dye-sensitized nanocrystalline TiO2 to [Co(bpy)3](3+) ions in solution, a process known as recombination in the context of DSC operation, is an important loss mechanism in these solar cells. Here, we employ impedance spectroscopy over a range of temperatures to characterize electron storage, transport, and recombination in efficient DSCs based on the [Co(bpy)3](3+/2+) redox mediator, with either the amphiphillic ruthenium sensitizer Z907 or the state-of-the-art organic sensitizer Y123.

Band engineered ternary solid solution CdSxSe1-x-sensitized mesoscopic TiO2 solar cells.

The optical band gap of the light absorber and the alignment of its bands with the underlying wide band gap metal oxide are critical for efficient light harvesting and charge separation in semiconductor-sensitized solar cells (SSCs). In practice, these two requirements are however not always fulfilled concomitantly in SSCs. Favourable band alignment in CdSe-sensitized TiO2 requires utilization of quantum sized CdSe, which causes great losses in the harvesting of long wavelength photons due to quantum confinement effects.

Patterned 3-dimensional metal grid electrodes as alternative electron collectors in dye-sensitized solar cells.

We describe the application of 3-dimensional metal grid electrodes (3D-MGEs) as electron collectors in dye-sensitized solar cells (DSCs) as a replacement for fluorinated tin oxide (FTO) electrodes. Requirements, structure, advantages, and limitations of the metal grid electrodes are discussed. Solar conversion efficiencies of 6.

Carrier generation and collection in CdS/CdSe-sensitized SnO2 solar cells exhibiting unprecedented photocurrent densities.

CdS/CdSe-sensitized nanostructured SnO(2) solar cells exhibiting record short-circuit photocurrent densities have been fabricated. Under simulated AM 1.5, 100 mW cm(-2) illumination, photocurrents of up to 17.

The influence of dye structure on charge recombination in dye-sensitized solar cells.

Replacing the nonyl groups on the solar cell dye Ru(4,4'-carboxylic acid-2,2'-bipyridine)(4,4'-dinonyl-2,2'-bipyridine)(NCS)(2) (Z-907) with amino groups results in a marked decrease in solar cell performance. This is despite the fact that the amino derivative (Z-960) has more favourable light absorption characteristics than Z-907 when used with thick nanocrystalline TiO(2) layers. Electron transfer to the electrolyte from the exposed fluorine-doped tin oxide (FTO) substrate is particularly fast in cells employing the Z-960 dye if a compact TiO(2) blocking layer is not used.

Synthesis and properties of [Pt(4-CO(2)CH(3)-py)(2)(mnt)]: comparison of pyridyl and bipyridyl-based dyes for solar cells.

The dye complexes [Pt(4-CO(2)R-py)(2)(mnt)] (R = H (3a), CH(3) (3b)) and the precursor complexes [Pt(4-CO(2)R-py)(2)Cl(2)] (2a, 2b) (py = pyridyl) were synthesised, characterised by electrochemical, spectroscopic, spectroelectrochemical (UV-vis-nIR and in situ EPR) and hybrid DFT computational methods and attached to a TiO(2) substrate to determine charge recombination kinetics. The results were compared to the bipyridyl analogues [Pt{X,X'-(CO(2)R)-2,2'-bipyridyl}(mnt)], (X = 3 or 4). The electronic characteristics of the bis-pyridyl complex were found to be different to the bipyridyl complexes making the former harder to reduce, shifting the lowest-energy absorption band to higher energy and showing separate degenerate LUMO orbitals on the two pyridine rings.

Dye-sensitized solar cells based on oriented TiO2 nanotube arrays: transport, trapping, and transfer of electrons.

Dye-sensitized solar cells fabricated using ordered arrays of titania nanotubes (tube lengths 5, 10, and 20 microm) grown on titanium have been characterized by a range of experimental methods. The collection efficiency for photoinjected electrons in the cells is close to 100% under short circuit conditions, even for a 20 microm thick nanotube array. Transport, trapping, and back transfer of electrons in the nanotube cells have been studied in detail by a range of complementary experimental techniques.