Veronica Celorrio | University College London (original) (raw)

Papers by Veronica Celorrio

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ACS Applied Materials & Interfaces, 2015

Aerosol processing enables the preparation of hierarchical graphene nanocomposites with special c... more Aerosol processing enables the preparation of hierarchical graphene nanocomposites with special crumpled morphology in high yield and in a short time. Using modular insertion of suitable precursors in the starting solution, it is possible to synthesize different types of graphene-based materials ranging from heteroatom-doped graphene nanoballs to hierarchical nanohybrids made up by nitrogen-doped crumpled graphene nanosacks that wrap finely dispersed MoS2 nanoparticles. These materials are carefully investigated by microscopic (SEM, standard and HR TEM), diffraction (grazing incidence X-ray diffraction (GIXRD)) and spectroscopic (high resolution photoemission, Raman and UV-visible spectroscopy) techniques, evidencing that nitrogen dopants provide anchoring sites for MoS2 nanoparticles, whereas crumpling of graphene sheets drastically limits aggregation. The activity of these materials is tested toward the photoelectrochemical production of hydrogen, obtaining that N-doped graphene/MoS2 nanohybrids are seven times more efficient with respect to single MoS2 because of the formation of local p-n MoS2/N-doped graphene nanojunctions, which allow an efficient charge carrier separation.

Chemistry (Weinheim an der Bergstrasse, Germany), Jan 17, 2015

Oleylamine (OA) based "hot injection" colloidal synthesis offers a versatile approach t... more Oleylamine (OA) based "hot injection" colloidal synthesis offers a versatile approach to the synthesis of highly monodisperse metallic and multi-metallic alloyed nanostructures in the absence of potentially toxic and unstable phosphine compounds. For application in heterogeneous catalysis and electrocatalysis, the adsorbed OA species at the metal surfaces should be effectively removed without compromising the structure and composition of the nanostructures. Herein, we investigate the removal of OA from colloidal Pt nanoparticles through 1) "chemical methods" such as washing in acetic acid or ethanol, and ligand exchange with pyridine; and 2) thermal pre-treatment between 185 and 400 °C in air, H2 or Ar atmospheres. The electrochemical reactivity of Pt nanoparticles is acutely affected by the presence of surface organic impurities, making this material ideal for monitoring the effectiveness of OA removal. The results showed that thermal treatment in Ar at temperat...

J Solid State Electrochem, 2014

A b s t r a c t A o n e -s t e p m e t h o d o f p r e p a r i n g photoelectrochemically active ... more A b s t r a c t A o n e -s t e p m e t h o d o f p r e p a r i n g photoelectrochemically active nanostructured BiVO 4 films is reported based on thermolysis (500°C in air) of a polyethylene glycol (PEG300) "paint-on" precursor solution containing Bi 3+ (as nitrate) and VO 4 3− (as the metavanadate ammonium salt). Films are formed directly on tin-doped indium oxide (ITO) substrates and characterised by electron microscopy (scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS)), X-ray diffraction, Raman spectroscopy, and photoelectrochemistry. The nanocrystalline film exhibited typically up to 52 % incident photon to current efficiency (IPCE) at 1.0 V vs. saturated calomel electrode (SCE) in aqueous 0.5 M Na 2 SO 4 with oxalate, strongly enhancing photocurrents.

J. Phys. Chem. C, 2014

Correlations between the population of deep trap states in an array of TiO 2 nanotubes (NT) and t... more Correlations between the population of deep trap states in an array of TiO 2 nanotubes (NT) and the dynamic photocurrent responses under supra-band-gap illumination are investigated. Ordered arrays of TiO 2 NT of 10 μm length, 125 nm inner diameter, and 12 nm wall thickness featuring strong anatase character were obtained by anodization of Ti in ethylene glycol solution containing NH 4 F. Cyclic voltammograms at pH 10 show the characteristic responses for nanostructured TiO 2 electrodes, in particular a sharp cathodic peak as the electron density in the film increases. These responses are associated with the population of deep trap states with an average value of 5 × 10 4 electrons per NT. Dynamic photocurrent measurements clearly show that the characteristic rise time of the photocurrent increases as the potential is increased above the onset region for charging deep trap states. At potentials in which deep trap states are fully depopulated in the dark, photocurrent rise time approaches values just below 1 s, which is more than 3 orders of magnitude slower than the estimated RC time constant. The occupancy of the deep trap states under photostationary conditions is a fraction of the density of states estimated from voltammetric responses. These findings are discussed in the context of current views about trap states in high surface area TiO 2 electrodes.

International Journal of Hydrogen Energy, 2014

Polymer electrolyte membrane fuel cell Carbon nanocoils Electrocatalyst a b s t r a c t Carbon na... more Polymer electrolyte membrane fuel cell Carbon nanocoils Electrocatalyst a b s t r a c t Carbon nanocoils (CNCs) synthesized via the catalytic graphitization of resorcinolformaldehyde gel were investigated as an electrocatalyst support in PEMFC anodes. Their textural and physical properties make them a highly efficient catalyst support for anodic hydrogen oxidation in low temperature PEMFC.

Journal of Power Sources, 2013

Carbon nanocoils (CNCs) were proposed as electrocatalysts support. Electrocatalyst' performance s... more Carbon nanocoils (CNCs) were proposed as electrocatalysts support. Electrocatalyst' performance strongly depended on the synthesis method. CNCs-supported showed better electrochemical behaviour than E-TEK electrocatalysts. By using CNCs as support the reaction route of intermediates is favoured. Intermediates oxidation is facilitated by the use of CNCs as support.

Electrochimica Acta, 2013

Different carbon materials with high electrical conductivity have been studied as electrocatalyst... more Different carbon materials with high electrical conductivity have been studied as electrocatalyst support for direct alcohol fuel cells (DAFCs). The aim of the work was to establish the influence of the support on the catalyst properties and to improve their efficiency in the fuel cell. Carbon nanofibers (CNFs), carbon nanocoils (CNCs) and ordered mesoporous carbons (gCMK-3) have been used for synthesizing platinum catalysts by the polyol method. Results have been compared with those obtained for a platinum catalyst supported on Vulcan XC-72R, prepared by the same method, and for the commercial Pt/C catalyst from E-TEK. It has been demonstrated that novel carbon supports could help to oxidize CO adsorbed on platinum particles more easily than the commercial carbon support and improve the alcohol oxidation reaction, both in terms of onset potential and current density. The catalyst supported on gCMK-3 carbon resulted to be the most effective in both the methanol and ethanol oxidation, which can be attributed to its ordered structure and high electrical conductivity.

ACS Applied Materials & Interfaces, 2015

Chemistry (Weinheim an der Bergstrasse, Germany), Jan 17, 2015

J Solid State Electrochem, 2014

J. Phys. Chem. C, 2014

International Journal of Hydrogen Energy, 2014

Journal of Power Sources, 2013

Electrochimica Acta, 2013