SFI Strategic Research Cluster in Solar Energy Conversion

Belfield, Ireland

SFI Strategic Research Cluster in Solar Energy Conversion

Belfield, Ireland

Time filter

Source Type

Mattle M.J.,Ecole Polytechnique Federale de Lausanne | Loughrey D.,SFI Strategic Research Cluster in Solar Energy Conversion | Rajesh B.,Ecole Polytechnique Federale de Lausanne | Rahman M.,SFI Strategic Research Cluster in Solar Energy Conversion | And 4 more authors.
Journal of Physical Chemistry C | Year: 2012

A series of C-doped, W-doped, and C,W-codoped TiO 2 samples have been prepared using modified sol-gel techniques. Reproducible inexpensive C-doping arises from the presence of melamine borate in a sol-gel mixture, whereas W-doping is from the addition of tungstic acid to the sol. The materials have been characterized using elemental analysis, N 2 physisorption (BET), thermogravimetric analysis, X-ray diffraction, Raman, X-ray photoelectron, UV-vis spectroscopies, and photocatalytic activity measurements. Doping C and W independently results in an increased absorbance in the visible region of the spectrum with a synergistic effect in increased absorbance when both elements are codoped. The increased visible-light absorbance of the W-doped or codoped materials is not reflected in photocatalytic activity. Visible-light-induced photocatalytic activity of C-doped material was superior to that of an undoped catalyst, paving the way for its application under only visible-light irradiation conditions. A significant fraction of the spectral red shift commonly observed with doped catalysts might be due to the formation of color centers as a result of defects associated with oxygen vacancies, and bandgap-related narrowing or intragap localization of dopant levels are not the only factors responsible for enhanced visible-light absorption in doped photocatalysts. Furthermore, bandgap narrowing through increases in the energy of the valence band may actually decrease photo-oxidation activity through a curtailment of one route of oxidation. © 2012 American Chemical Society.


Morgan G.G.,SFI Strategic Research Cluster in Solar Energy Conversion | Fennell K.,SFI Strategic Research Cluster in Solar Energy Conversion | Kishore M.J.L.,SFI Strategic Research Cluster in Solar Energy Conversion | Sullivan J.A.,SFI Strategic Research Cluster in Solar Energy Conversion | Sullivan J.A.,Kyungpook National University
ChemCatChem | Year: 2013

Two bimetallic cryptates (containing Cu and Co), which have previously been shown to react with and activate atmospheric CO2, were tethered to modified mesoporous SiO2 and their activities in promoting the CO2+H2 reaction has been analysed. The cryptates were tethered to -C3H6Cl-modified SBA-15 through a condensation reaction between surface alkyl chlorides and 2° amines of the ligands, which released HCl and formed 3° amine linkages. The materials were characterised using BET, thermogravimetric analysis, FTIR and elemental analysis and their activities in promoting the CO2+H2 reaction was tested under batch reactor conditions. Co ions appear to selectively populate the medal sites of the tethered ligands whereas Cu ions appear to deposit on the surface as Cu(BF4)2 salts. The composite materials generate CO and CH4 from the CO2+H2 mixtures. Co-containing catalysts are more effective than their Cu analogues in promoting the reaction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Gorman P.D.,SFI Strategic Research Cluster in Solar Energy Conversion | English N.J.,SFI Strategic Research Cluster in Solar Energy Conversion | English N.J.,University College Dublin | MacElroy J.M.D.,SFI Strategic Research Cluster in Solar Energy Conversion
Physical Chemistry Chemical Physics | Year: 2011

Classical equilibrium molecular dynamics (MD) simulations have been performed to investigate the dynamical and energetic properties in hydrogen and mixed hydrogen-tetrahydrofuran sII hydrates at 30 and 200 K and 0.05 kbar, and also at intermediate temperatures, using SPC/E and TIP4P-2005 water models. The potential model is found to have a large impact on overall density, with the TIP4P-2005 systems being on average 1% more dense than their SPC/E counterparts, due to the greater guest-host interaction energy. For the lightly-filled mixed H2-THF system, in which there is single H2 occupation of the small cage (1s1l), we find that the largest contribution to the interaction energy of both types of guest is the van der Waals component with the surrounding water molecules in the constituent cavities. For the more densely-filled mixed H2-THF system, in which there is double H 2 occupation in the small cage (2s1l), we find that there is no dominant component (i.e., van der Waals or Coulombic) in the H2 interaction energy with the rest of the system, but for the THF molecules, the dominant contribution is again the van der Waals interaction with the surrounding cage-water molecules; again, the Coulombic component increases in importance with increasing temperature. The lightly-filled pure H2 hydrate (1s4l) system exhibits a similar pattern vis-à-vis the H 2 interaction energy as for the lightly-filled mixed H 2-THF system, and for the more densely-filled pure H2 system (2s4l), there is no dominant component of interaction energy, due to the multiple occupancy of the cavities. By consideration of Kubic harmonics, there is some evidence of preferential alignment of the THF molecules, particularly at 200 K; this was found to arise at higher temperatures due to transient hydrogen bonding of the oxygen atom in THF molecules with the surrounding cage-water molecules. © the Owner Societies 2011.


Healy J.J.,Communications and Optoelectronic Research Center | Healy J.J.,SFI Strategic Research Cluster in Solar Energy Conversion | Healy J.J.,University College Dublin | Sheridan J.T.,Communications and Optoelectronic Research Center | Sheridan J.T.,University College Dublin
Optics Letters | Year: 2010

The linear canonical transform may be used to simulate the effect of paraxial optical systems on wave fields. Using a recent definition of the discrete linear canonical transform, phase space diagram analyses of the sampling requirements of the direct method of calculating the Fresnel and other linear canonical transforms are more favorable than previously thought. Thus the direct method of calculating these transforms may be used with fewer samples than previously reported simply by making use of an appropriate reconstruction filter on the samples output by the algorithm. © 2010 Optical Society of America.


English N.J.,SFI Strategic Research Cluster in Solar Energy Conversion | English N.J.,University College Dublin
Chemical Physics Letters | Year: 2013

The dynamical properties of physically adsorbed water molecules on partially hydroxylated rutile-(1 10) surfaces have been studied via equilibrium Born-Oppenheimer molecular dynamics. It was found that water molecules were almost parallel to the surface. There is a coupling frequency of around 110 and 220 cm 1 between the translational modes of the water molecules and the upper layer of Ti and bridging oxygen atoms in the titania, respectively. Hydrogen bonds with the surface were observed to be stable, with stretch frequencies around 835-920 cm 1. Oxygen-vacancies were found to weaken hydrogen bonding between the water molecules' protons and the bridging oxygen atoms. © 2013 Elsevier B.V. All rights reserved.


Healy J.J.,University College Dublin | Healy J.J.,SFI Strategic Research Cluster in Solar Energy Conversion | Sheridan J.T.,University College Dublin | Sheridan J.T.,SFI Strategic Research Cluster in Solar Energy Conversion
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2010

The linear canonical transform provides a mathematical model of paraxial propagation though quadratic phase systems. We review the literature on numerical approximation of this transform, including discretization, sampling, and fast algorithms, and identify key results. We then propose a frequency-division fast linear canonical transform algorithm comparable to the Sande-Tukey fast Fourier transform. Results calculated with an implementation of this algorithm are presented and compared with the corresponding analytic functions. © 2010 Optical Society of America.


Wadnerkar N.,SFI Strategic Research Cluster in Solar Energy Conversion | English N.J.,SFI Strategic Research Cluster in Solar Energy Conversion | English N.J.,University College Dublin
Computational Materials Science | Year: 2013

Hybrid density functional theory (DFT) calculations were performed on the monoclinic clinobisvanite polymorph of bismuth vanadate (BiVO4), which has piqued experimental and theoretical interest in recent years due to its photo-active nature. In particular, the effect of using PBEsol and HSE06-PBEsol functional, as corrected for the solid state, is gauged upon the predictive performance for electronic structure, band gap and optical properties. It was found that HSEsol-type functionals offer better predictive performance than PBEsol with respect to experimental data, although PBEsol performs comparatively well for this system, despite its general well-known limitations. Nonetheless, appropriately-tuned HSE06-PBEsol hybrid functionals may provide an improved description of solids compared to PBE, PBEsol and HSE06. Although the 'standard' proportion of exact exchange for HSEsol (25%) seems to provide a relatively accurate band gap vis-à-vis experiment, a smaller proportion (circa 10%) achieves quantitative agreement in this respect; in addition, the prediction of the lattice constants and band gaps is improved substantially. For HSE06-PBEsol, analysis of the density of states analysis showed that the conduction-band minimum (CBM) and valence-band maximum (VBM) position shift upwards and downwards, respectively, thus widening the band gap, in better agreement with experimental results. It was found that clinobisvanite is an indirect (albeit closer to a direct) band-gap semiconductor, and the optical properties were investigated, including the effect of varying the proportion of exact exchange thereon. © 2013 Elsevier B.V. All rights reserved.


El-Hendawy M.M.,SFI Strategic Research Cluster in Solar Energy Conversion | English N.J.,SFI Strategic Research Cluster in Solar Energy Conversion | English N.J.,University College Dublin | Mooney D.A.,SFI Strategic Research Cluster in Solar Energy Conversion | Mooney D.A.,University College Dublin
Inorganic Chemistry | Year: 2012

Using density functional theory (DFT) methods, we have investigated two possible mechanisms for atmospheric CO 2 fixation in the cavity of the dinuclear zinc(II) octa-azacryptate, and the subsequent reaction with methanol whereby this latter reaction transforms the (essentially) chemically inert CO 2 into useful products. The first mechanism (I) was proposed by Chen et al. [Chem.-Asian J.2007, 2, 710], and involves the attachment of one CO 2 molecule onto the hydroxyl-cryptate form, resulting in the formation of a bicarbonate-cryptate species and subsequent reaction with one methanol molecule. In addition, we suggest another mechanism that is initiated via the attachment of a methanol molecule onto one of the Zn-centers, yielding a methoxy-cryptate species. The product is used to activate a CO 2 molecule and generate a methoxycarbonate-cryptate. The energy profiles of both mechanisms were determined, and we conclude that, while both mechanisms are energetically feasible, free energy profiles suggest that the scheme proposed by Chen et al. is most likely. © 2012 American Chemical Society.


O'Callaghan N.,SFI Strategic Research Cluster in Solar Energy Conversion | Sullivan J.A.,SFI Strategic Research Cluster in Solar Energy Conversion
Applied Catalysis B: Environmental | Year: 2014

A series of Ti-modified mesoporous SiO2 materials (SBA-15 and MCF) are prepared, characterised and used as catalysts in the selective epoxidation of a probe alkene (cyclohexene) using H2O2 as an oxidising agent. Similarly, a series of mesoporous SiO2-supported monometallic and bimetallic DMAP-stabilised Au and Pd nanoparticles were prepared, characterised and used as catalysts in the production of H2O2 from dilute H2(g)+O2(g) mixtures.The metallic nanoparticles were then supported on the Ti-modified mesoporous SiO2 and these hybrid materials were characterised and their activities in the selective epoxidation of alkenes in the presence of H2(g)+O2(g) mixtures (where H2O2 would be formed in situ) were studied. The bimetallic Au/Pd nanoparticles (which were most active in the production of H2O2 from H2 and O2) were not the most active or selective in the combined reaction. This was ascribed to the Pd component of the nanoparticles promoting hydrogenation of the probe alkene more rapidly than the formation of H2O2. The selectivity of Au nanoparticles in the presence of H2(g)+O2(g) was higher than that of the same catalysts in the presence of H2O2(aq). © 2013 Elsevier B.V.


Rahman M.,SFI Strategic Research Cluster in Solar Energy Conversion | Rahman M.,Electric Ireland | MacElroy J.M.D.,SFI Strategic Research Cluster in Solar Energy Conversion | Dowling D.P.,Electric Ireland
Journal of Nanoscience and Nanotechnology | Year: 2011

The production of hydrogen from water (called "water splitting"), utilises sunlight as an energy source (solar-hydrogen) in a photoelectrochemical (PEC) solar cell, is a promising source of green energy. In this work, a PEC was used, for evaluating the photoactivity of a thin film TiO 2 based photoanode by measuring photocurrent (which is comparable to hydrogen production rate by water splitting process in PEC). The main focus of this work is to study the effect of the TiO 2 nanosurface and bulk properties on the photoresponse properties of the photoanode. The TiO 2 coatings (360-400 nm) were deposited using a closed field reactive magnetron sputtering system. The structure and morphology of the TiO 2 coatings were systematically altered by varying the deposition pressure between 5×10 -4 to 1×10 -2 mbar. The properties of the deposited nano-coatings were determined using Ellipsometry, SEM, AFM, profilometry, XPS, Raman and X-ray diffraction (XRD). Coating properties were correlated with the light absorption and photocurrent performance which were evaluated using UV-Vis spectroscopy and tri-electrode potentiostat measurements respectively. It was concluded from this study that the coating deposition pressure has a pronounced effect on the TiO 2 photoanode properties leading to a significant enhancement in the photoactivity in PEC cell. Over a six fold increase in photocurrent at applied potential 0 V was observed for TiO 2 photoanode prepared at 4×10 -3 mbar as compared to 5×10 -4 mbar. A correlation has been established between the deposition pressure, nano surface morphology and bulk properties, UV-Vis light absorbance and bandgap value, and the consequently higher (i) photocurrent density, (ii) negative flat band, and (iii) open circuit potential measured in Photoelectrochemical (PEC) cell. Copyright © 2011 American Scientific Publishers. All rights reserved.

Loading SFI Strategic Research Cluster in Solar Energy Conversion collaborators
Loading SFI Strategic Research Cluster in Solar Energy Conversion collaborators