Bifunctional doping effect on the TiO2 nanowires for photoelectrochemical water splitting (original) (raw)
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Branched TiO2/Si nanostructures for enhanced photoelectrochemical water splitting
Nano Energy, 2013
We report a successful fabrication of hierarchical three-dimensionally branched TiO 2 /Si nanowire arrays and their application as the photoelectrochemical electrode for solar water splitting. The branched TiO 2 /Si nanowire arrays improved the photoelectrochemical (PEC) performance compared to TiO 2 thin film-coated Si nanowire arrays because of the substantially increased surface area for electrochemical reactions and enhanced charge transfer kinetics. Wavelength-dependent photocurrent response of the branched nanowire array indicates a strong response in the ultraviolet region (o400 nm), while a negligible photocurrent is observed under visible illumination, primarily caused by the high overpotential loss of n-Si photoanode and energy band configuration of the TiO 2 /Si heterojunction. The working mechanism based on recombination at this heterogeneous n-n junction is proposed. This study provides insights on the fundamental understanding and potential optimizations of nanoscale hierarchical 3D structured devices for renewable energy applications. Published by Elsevier Ltd.
Nanoscale Research Letters, 2013
One-dimensional anodic titanium oxide (ATO) nanotube arrays hold great potential as photoanode for photoelectrochemical (PEC) water splitting. In this work, we report a facile and eco-friendly electrochemical hydrogenation method to modify the electronic and PEC properties of ATO nanotube films. The hydrogenated ATO (ATO-H) electrodes present a significantly improved photocurrent of 0.65 mA/cm 2 in comparison with that of pristine ATO nanotubes (0.29 mA/cm 2 ) recorded under air mass 1.5 global illumination. The incident photon-tocurrent efficiency measurement suggests that the enhanced photocurrent of ATO-H nanotubes is mainly ascribed to the improved photoactivity in the UV region. We propose that the electrochemical hydrogenation induced surface oxygen vacancies contribute to the substantially enhanced electrical conductivity and photoactivity.
Journal of The Electrochemical Society, 2021
Iron oxyhydroxide (FeOOH) was implemented as a low-cost, stable, and earth-abundant catalyst on hydrogenated titania nanorods array (H-TiO2/FeOOH), for photoelectrochemical water splitting applications. The hydrogenation treatment enhanced the maximum photocurrent density delivered by the titania-based photoanode (from 0.65 mA cm−2 to 1 mA cm−2 at +1.23 V vs RHE) while the exploitation of FeOOH resulted in a significant improvement in the photoelectrochemical activity at low bias. The optimized photoelectrode showed ∼0.6 mA cm−2 at +0.4 V vs RHE, with a saturation current density of 1.05 mA cm−2. Insights on the role of FeOOH were revealed by electrochemical impedance and photoluminescence measurements, suggesting a reduction of the charge transfer resistance at the electrolyte interface and a lower frequency of recombination events. The H-TiO2/FeOOH photoelectrode showed a maximum applied bias photon-to-current efficiency (ABPE) of 0.68% with a 0.3 V bias, while for the bare TiO2 n...
Nature communications, 2016
Production of chemical fuels by direct solar energy conversion in a photoelectrochemical cell is of great practical interest for developing a sustainable energy system. Various nanoscale designs such as nanowires, nanotubes, heterostructures and nanocomposites have been explored to increase the energy conversion efficiency of photoelectrochemical water splitting. Here we demonstrate a self-organized nanocomposite material concept for enhancing the efficiency of photocarrier separation and electrochemical energy conversion. Mechanically robust photoelectrodes are formed by embedding self-assembled metal nanopillars in a semiconductor thin film, forming tubular Schottky junctions around each pillar. The photocarrier transport efficiency is strongly enhanced in the Schottky space charge regions while the pillars provide an efficient charge extraction path. Ir-doped SrTiO3 with embedded iridium metal nanopillars shows good operational stability in a water oxidation reaction and achieves...
Scientific Reports, 2016
It is highly desired to effectively trap photogenerated holes for efficient photoelectrochemical (PEC) water oxidation to evolve O2 on oxide semiconductors. Herein, it is found for the first time mainly based on the time-resolved- and atmosphere-controlled- surface photovoltage responses that the modified chloride would effectively trap photogenerated holes so as to prolong the charge lifetime and hence promote charge separation of single-crystal rutile TiO2 nanorods. Its strong capacity to trap holes, comparable to the widely-used methanol and Co(II) phosphate, is well responsible for the exceptional photoactivities for PEC water oxidation to evolve O2 on rutile nanorods with a proper amount of chloride modified, about 2.5-time high as that on the resulting anatase nanoparticles, even 10-time if the surface area is considered. Moreover, it is suggested that the hole trapping role of chemically-adsorbed chloride is related to its lonely-pair electrons, and to the subsequently-produc...
ACS Nano, 2012
We report that the length and surface properties of TiO 2 nanowires can have a dramatic effect on their photoelectrochemical properties. To study the length dependence, rutile TiO 2 nanowires (0.28À1.8 μm) were grown on FTO substrates with different reaction times (50À180 min) using a hydrothermal method. Nanowires show an increase in photocurrent with length, and a maximum photocurrent of 0.73 mA/cm 2 was measured (1.5 V vs RHE) for 1.8 μm long nanowires under AM 1.5G simulated sunlight illumination. While the incident photon to current
International Journal of Hydrogen Energy, 2012
Sonication assisted anodization of titanium in a fluorinated ethylene glycol and water electrolyte using Ti itself as a cathode is investigated. The prepared anodic film has a highly ordered nanotube-array surface architecture. The resulting TiO 2 nanotubes at potential 20e40 V have various diameters (30e100 nm), tube length (3e12 mm) and wall thicknesses (6e15 nm). The tube diameter and wall thickness are increased with the anodization time while the overall length of the nanotube arrays is controlled by the duration of the anodization time. In addition, apart from the anodization time, formation of nanotubes is governed by the distance and supplied voltages between the two electrodes, for a given electrolyte. The crystal structure and surface morphology of the annealed anodic films are investigated by XRD and SEM, respectively. The corresponding photoelectrochemical water splitting efficiency (PCE) was calculated under UV light. Our results show a very high PCE under UV (315e400 nm, 100 mW/cm 2) irradiation. The maximum value of PCE for hydrogen generation obtained was 29% which is one of the best results reported in literature [1].
Phys. Chem. Chem. Phys., 2015
The interaction strength of Au nanoparticles with pristine and nitrogen doped TiO 2 nanowire surfaces was analysed using density functional theory and their significance in enhancing the solar driven photoelectrocatalytic properties was elucidated. In this article, we prepared 4-dimethylaminopyridine capped Au nanoparticle decorated TiO 2 nanowire systems. The density functional theory calculations show {101} facets of TiO 2 as the preferred phase for dimethylaminopyridine-Au nanoparticles anchoring with a binding energy of À8.282 kcal mol À1 . Besides, the interaction strength of Au nanoparticles was enhanced nearly four-fold (À35.559 kcal mol À1 ) at {101} facets via nitrogen doping, which indeed amplified the Au nanoparticle density on nitrided TiO 2 . The Au coated nitrogen doped TiO 2 (N-TiO 2 -Au) hybrid electrodes show higher absorbance owing to the light scattering effect of Au nanoparticles. In addition, N-TiO 2 -Au hybrid electrodes block the charge leakage from the electrode to the electrolyte and thus reduce the charge recombination at the electrode/electrolyte interface. Despite the beneficial band narrowing effect of nitrogen in TiO 2 on the electrochemical and visible light activity in N-TiO 2 -Au hybrid electrodes, it results in low photocurrent generation at higher Au NP loading (3.4 Â 10 À7 M) due to light blocking the N-TiO 2 surface. Strikingly, even with a ten-fold lower Au NP loading (0.34 Â 10 À7 M), the synergistic effects of nitrogen doping and Au NPs on the N-TiO 2 -Au hybrid system yield high photocurrent compared to TiO 2 and TiO 2 -Au electrodes. As a result, the N-TiO 2 -Au electrode produces nearly 270 mmol h À1 cm À2 hydrogen, which is nearly two-fold higher than the pristine TiO 2 counterpart. The implications of these findings for the design of efficient hybrid photoelectrocatalytic electrodes are discussed.
In the present work our attention was focused on the obtaining photoelectrodes for photoelectrochemical cell that incorporate two electrodes, one of which has been titania (TiO 2 ) coated on a transparent conducting oxide (TCO), referred to as the primary electrode and the other, the counter electrode, a non-corrosive metal such as a thin layer of platinum. A thin layer of a nanoporous TiO 2 semiconductor was deposited onto a sheet of ITO conducting glass (sheet resistance ~ 30 Ωcm -2 ). Several complementary investigation techniques like BET, SEM and XRD were used to follow the influence of the reactants molar ratio and thermal treatment on the TiO 2 photoanode. The nanocrystalline TiO 2 /ITO conducting glass electrode seems to be a promising photoanode in a photoelectrochemical cell for hydrogen generation by water splitting.