TiO2 Arrays Research Articles

Enhanced photoelectric properties of TiO2 nanorod arrays through modulation of precursor concentration

This study synthesized titanium dioxide (TiO2) nanorod arrays and investigated their morphology and defect to the photoelectric response by varying the titanium isopropoxide (TTIP) precursor concentration from 0 to 66 mM. The vertically aligned rutile TiO2 nanorods exhibited film thicknesses ranging from 1 to 4.5 μm when the TTIP concentration equaled or exceeded 33 mM. Their rod length and diameter displayed a linear increase with the TTIP concentration. TiO2 arrays synthesized with a TTIP concentration of 33 mM exhibited the highest photoelectric response, measuring 52 μA/cm2 under xenon-lamp irradiation at a bias voltage of 0.8 V (vs. the Ag/AgCl reference). Notably, photoactivity was observed in the visible-light region as well. Photoluminescence spectra indicated a substantial reduction in electron-hole recombination compared to TiO2 arrays prepared from higher TTIP concentrations. X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses confirmed the presence of oxygen vacancies. Time-resolved photoluminescence spectra corroborated an extended electron lifetime, suggesting that surface oxygen vacancies facilitated the separation of photoexcited charge carriers. The presence of oxygen vacancies, combined with the unique array morphology, resulted in enhanced photocurrent density.

C3N5/TiO2 S-scheme heterojunction film for efficient photocatalytic removal of gatifloxacin

Constructing efficient and recyclable photocatalysts is a promising method to solve antibiotic pollution. Herein, we designed and fabricated C3N5/TiO2 S-scheme heterojunction film on flexible Ti foils through the self-absorbed. The C3N5 nanosheet was tightly anchored on the TiO2 arrays with an intimate TiO2-C3N5 interface. The heterojunction exhibited an excellent photocatalytic performance and the reaction rate constant of photocatalytic degradation gatifloxacin (GAT) over C3N5/TiO2 up to 0.0252 min−1, which was 1.85 folds that of pure TiO2 arrays. The outstanding photocatalytic performance was ascribed to high-efficiency transfer and separation of photoinduced carriers and highly hydrophilic surfaces. The removal rate of GAT under different parameters suggested that the as-prepared C3N5/TiO2 has high adaptability. Moreover, the three possible GAT degradation pathways over C3N5/TiO2 were proposed based on the results of the liquid chromatograph-mass spectrometer (LC-MS) and density functional theory (DFT). Finally, a reasonable S-scheme heterojunction was proposed based on the results of experiments and DFT calculation. This work may help in designing an S-scheme heterojunction for the degradation of antibiotic pollutants.

Realization of Self‐Powered High‐Performance Photodetection via Electrostatic Field Enhancement and Dark Current Suppression

Self‐powered photodetectors (PDs) are particularly attractive in the construction of environmentally friendly and sustainable Internet of Things. Utilizing dual functions of PTFE of electrostatic field enhancement and dark current suppression, a high‐performance self‐powered ITO/PTFE/TiO2/GaN UV PD is developed herein. The introduction of PTFE not only significantly reduces the dark current, but also facilitates the separation of photogenerated carriers by coupling the internal electrostatic field at the PTFE/TiO2 interface with the built‐in electric field of the TiO2/GaN heterojunction. With 0 V bias, the light‐to‐dark current (Ilight/Idark) ratio of the PD with PTFE is improved by 2297 times and the response time is faster by 1.69/2.96 times compared to the ITO/TiO2/GaN PD. In addition, a microstructured M‐ITO/PTFE/TiO2/GaN PD with micrometer‐sized cylindrical TiO2 arrays exhibits a high Ilight/Idark ratio of 3.65 × 105, a responsivity of 280.1 mA W−1, a high detectivity of 1.97 × 1013 Jones, and a response time of 4.3/3.0 ms under 360 nm illumination. Our strategy provides a promising way to develop high‐performance self‐powered PD.

Experimental and theoretical unraveling of the electrocatalytic hydrodechlorination of chlorinated phenol using Pd promoted by oxygen vacancies in TiO2 array

The electrocatalytic dichlorination (EHDC) shows a promising potential to degrade chlorinated phenols (CPs). It is also a green technology in reducing the corresponding hazardous impact on the environment. In this study, we constructed a catalytic structure which was Pd on a TiO2 array with oxygen vacancies on carbon fibre paper substrate (Pd/TiO2/CFP) by a relatively mild route. Due to the presence of the oxygen vacancies, the resulting strong metal-support interaction (SMSI) effect has been identified which featured a redistribution of spatial charge in Pd/TiO2. The electron flow from the oxygen vacancies in the TiO2 to Pd facilitated the adsorption of Pd with 4-chlorophenol (4-CP) and endowed the Pd metal with an improved chemical reaction kinetics even at a low Pd loading. Experimentally, we studied the dependence of pH, concentration of 4-CP, and working potential on the reaction conditions of EHDC. The results showed that the conversion of 4-CP reached 100 % within 180 min with an apparent rate constant of 2.9 × 10-2 min−1 and the dominant product was phenol (P). The multi-cycle test illustrated that the Pd/TiO2/CFP electrode showed superior stability. The results also revealed that the comprehensive catalytic behavior was much better than those of the Pd/CFP and the TiO2/CFP electrodes. The density function theory (DFT) calculations indicated that 4-CP was more preferably absorbed on Pd/TiO2/CFP than Pd/CFP due to the SMSI assistance. This study provides a valuable guide in the preparation of precious metal-based electrodes for EHDC with a reduced loading and cost but without performance compromise.

Nitrogen-rich carbon nitride (C3N5) coupled with oxygen vacancy TiO2 arrays for efficient photocatalytic H2O2 production

Developing efficient and facilitated recycling photocatalysts for H2O2 formation is an ideal strategy for solar-to-chemical energy conversion. In this work, we synthesized ultrathin C3N5 nanosheets through the process of thermal polymerization and polyvinylpyrrolidone (PVP)-assisted solvent exfoliation. Subsequently, the obtained ultrathin C3N5 nanosheets were tightly attached to the surface of TiO2-x arrays, resulting in an enhanced photocatalytic H2O2 production rate. The density functional theory (DFT) calculations demonstrate that an internal electric field (IEF) is generated between the TiO2-x array and the ultrathin C3N5 due to the different work functions. The presence of IEF provides an additional driving force for carrier separation and transfer in the heterointerface. Benefitting from this unique strategy, the optimal heterojunction obtains the highest H2O2 formation rate (2.93 μmol/L/min), which is about 4.1 times than that of TiO2-x arrays. The rotating disk electrode (RDE) analysis manifests H2O2 formation through 2e--dominated oxygen reduction reaction (ORR). This research provides an innovative strategy for assembling a type-II heterojunction with a useful IEF for efficient photocatalytic H2O2 production.

Pt-modified TiO2 nanorod array films on FTO with enhanced CO sensitivity: A combined experimental and first-principle study

In this work, highly regular TiO2 array films consisting of nanorods with a diameter of ∼119 nm were grown on FTO via a facile hydrothermal method. Then Pt nanoparticles with a size of ∼5 nm were modified on the surface of TiO2 nanorods via an in-situ reduction process. The gas-sensing performances of pristine TiO2 and Pt-modified TiO2 samples were systematically tested. The introduction of Pt nanoparticles could enhance the response and stability toward CO gas and decrease the optimal operating temperature from 400 °C to 360 °C. And the Pt/TiO2-based sensor with a Pt content of 1.5 wt% exhibits the maximum CO sensitivity. Furthermore, the adsorption energies of Pt-modified or Pt-doped TiO2 for CO molecules were calculated using first-principles calculations. The chemical sensitivity of Pt to CO molecules may be responsible for the improved CO sensitivity. Additionally, the unique nanorod array structure of Pt/TiO2 and the nano-Schottky junction generated between them are helpful in enhancing the gas-sensing property.

Optimisation of a Ce–Mn co-doped SnO2–Sb anode based on a nanotubular TiO2 array for electrochemical decolourisation of wastewater

ABSTRACT In this study, Ce and Mn co-doped SnO2–Sb electrode was prepared onto a Ti/TiO2 nanotubes surface. The nanostructure of the novel electrode was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS), and specific techniques were used to study the electrochemical characteristics of the electrode. SEM analysis results showed that TiO2 nanotubes could reduce the crack morphology and provide a larger surface area for loading the electrochemically active material. EDS analysis showed that Ce and Mn were doped into the electrode successfully. Under optimised conditions, the electrode prepared with Sn:Sb:Ce:Mn mole ratio of 100:10:3:3 has the best electrocatalytic performance. Ethylene glycol was used as the solvent in cerium-manganese co-doped Ti/TiO2–NTs/TiO2–SnO2–Sb electrode. Ce–Mn co-doped TiO2NTs/SnO2–Sb electrode has a high oxygen evolution potential of 1.79 V (vs. SCE) and a lower charge transfer resistance. The decolourisation extent of 30 mg L−1 methylene blue wastewater reaches 98.5% within 30 min. Finally, the main intermediates were identified by gas chromatography-mass spectrometer (GC-MS), and possible pathways for dye degradation were proposed. This study opens a door to the rapid electrochemical decoloursation treatment of wastewater by using an easily obtainable multi-metal co-doped electrode.

Experimental Investigation of Long-term Ageing Effect on the Structural and Electrochemical Behaviour of Self-organized TiO2 Array Nanotubes on Ti-6Al-4V Alloy

Background: The correlation between anodization conditions and the ageing effect on TiO2 nanotubes (TNT) surface has been widely studied in different media and conditions (physiological solutions, mechanical stresses in water, etc.) for the prediction of their behaviour over a long period of time. In the present study, the synthesized TiO2 nanotubes (TNT) from Ti-6Al-4V alloy, which were left unattended and exposed to environmental conditions (i.e., humidity and ambient temperature) for more than 4 years, were investigated to underline any important alteration/changes and ageing effects, on the surface morphology, the surface composition, and the electrochemical behaviour. The nanotubes were made in 2018 by anodization in different potentials (20V, 40V, 50V, and 60V) for different times (30 min, 60 min, 90 min, 150 min and 180 min) in an Ethylene Glycol solution for other purposes. Methods: For the surface morphology characterisation, electronic microscopy (SEM) was performed to depict any tendency with anodization conditions: potential and time. The comparison study between the obtained results and the SEM pictures taken on similar samples made and characterized under the same conditions in 2018, reveals a noticeable alteration in the morphology and a change in the TNT’s external diameter. Surface composition was checked using energy dispersive spectrometry (EDXS). The EDXS spectra analysis was realised to investigate the storage time impact on structure surface stability. A drastic decrease in the amount of oxygen was noticed on all of the surfaces where wettability measurements by contact angle were performed to confirm the latter. The verification of the hydrophobicity of TNT surfaces attested that all aged samples are hydrophobic in concordance with EDXS analysis and X-ray photoelectron spectroscopy (XPS). To affirm the surface modification during the storage duration and its impact on the electrical behaviour: cyclic voltammetry (CV), open circuit potential (OCP) measurements, and Tafel plots are undergone on the aged samples and compared with the freshly synthesised samples [1],[2]. The plotted CV curved as a function of the scan rate and the composition of the electrolyte showed a correlation between the different samples electrochemical behaviour and their surface morphologies as well as the existence of surface states for all samples. Results: From the previous characterisation, it was obvious that the sample prepared at 40V over 3 hours showed a remarkable electrochemical behaviour. The ageing effect is closely related to the anodization conditions. It was also noticed that the amount of water in the electrolyte solution EG played a contributing factor in the onset of ageing. High water content causes the formation of nanograss which have a non-negligible influence on the morphology. Conclusion: These results can open a new way for the optimization of the storage conditions according to anodization conditions (electrolyte, voltage, time, and temperature annealing) of this material as well as for the study of the life cycle of products made from TiO2 nanotubes. : Exposing nanotube surfaces to ambient conditions without taking any precautionary measures and without knowing their historical anodization conditions can cause drastic changes in the electrochemical behaviour of TNT. These changes affect considerably their function for different applications.

Introducing oxygen-doped g-C3N4 onto g-C3N4/TiO2 heterojunction for efficient catalytic gatifloxacin degradation and H2O2 production

Developing multi-functional high-efficiency photocatalysts to solve environmental pollution and the global energy crisis remains challenging. In this work, a novel oxygen-doped g-C3N4 modified g-C3N4/TiO2 (OCN@CNT-2) with double Z-scheme heterojunction was fabricated through electrostatic self-assembly. This strategy facilitates the uniform and tight adhesion of g-C3N4 and oxygen doping on g-C3N4 (OCN) to the surface TiO2 arrays. The ternary heterojunction could significantly enhance photocatalytic activity and removal of 91.7% gatifloxacin (GAT) within 2 h. Furthermore, the OCN@CNT-2 demonstrated the highest photosynthetic rate, and the concentration of H2O2 was recorded to be approximately 133.04 μmol/L after 60 min of irradiation. The enhanced photocatalytic activity is due to the formation of a double Z-type heterojunction, which amplifies the absorption edge and effectively separates electron-hole pairs through the influence of an internal electric field (IEF). Suggestions for GAT decomposition were put forward, and the toxicity of GAT and its decomposed components was evaluated. Moreover, the mechanism of charge transfer in a double Z-scheme heterojunction has been elucidated.

Pool boiling enhancement via biphilic surface comprising superhydrophilic TiO2 and superhydrophobic Teflon arrays

The ever-increasing power density overloads the heat removal capability of miniaturized power electronic devices and thus an efficient liquid cooling method needs to be strategized. Herein, we introduce a biphilic surface consisting of both superhydrophilic TiO2 and superhydrophobic Teflon. The purpose of this unique combination is to decrease the superheat (Tsat) by efficiently releasing vapor bubbles via the superhydrophobic surface and to increase the critical heat flux (CHF) using efficient wetting supplied by the superhydrophilic surface. The superhydrophilic TiO2 layer was deposited by the room temperature aerosol deposition method, whereas the superhydrophobic Teflon dots were deposited by the atmospheric supersonic cold spraying method. Each Teflon dot was 1 mm in diameter and the dots were patterned in the form of n×n arrays, where n varied from 1 to 5. The optimal CHF (187 kW·m−2), superheat, and effective heat transfer coefficient (4.6 kW·m−2·k−1) were observed for the 4 × 4 sample, beyond which the cooling effect deteriorated because of the excessive area covered by the Teflon dots. While the Teflon dots facilitated efficient bubble release, securing sufficient flow passage with the aid of a hydrophilic wetting area was also critical; thus the combination of the superhydrophobic and superhydrophilic surfaces was optimally balanced.

Enhancement of visible-light photo-activity of TiO2 arrays for environmental water purification

PurposeOver the past decades, intense efforts have been devoted to design and synthesize efficient photocatalysts which are active under sunlight for environmental and energy applications. Titanium dioxide (TiO2) has attracted much attention over many years for organic contaminant degradation in air or water due to its strong optical absorptivity, chemical stability and low cost. However, TiO2 has a very low photo quantum yield which prompts the easy recombination of photogeneration electron/hole pairs. In addition, bandgap of 3.2 eV restrains application of this photocatalyst mainly to the UV range.Design/methodology/approachVertically oriented one-dimensional TiO2 nanostructures remarkably improve electron transport by creating a direct conduction pathway, decreasing intercrystalline contacts and stretching grown structure with the specified directionality. In this research, to enhance the visible light absorbance of TiO2, prearranged hydrogenated titanium dioxide nanorods (H-TNRs) in the presence of H2/N2 gas flow are hydrothermally synthesized.FindingsThe X-ray diffraction patterns illustrated the characteristic peaks of tetragonal rutile TiO2 and confirmed that there is no phase change after hydrogenation. Trivalent titanium ions surface defects and oxygen vacancies were considered as major reasons for redshift of absorption edge toward visible region and subsequently narrowing the bandgap to 2.27 eV. The optimized photocatalysts exhibited high visible-light-driven photocatalytic activity for degradation of methylene blue in water within 210. The synthesized H-TNRs established themselves as promising photocatalysts for organic compounds degradation in the aqueous solution.Originality/valueTo the best of the authors’ knowledge, this work is original and has not been published elsewhere nor is it currently under consideration for publication elsewhere.

(Invited) Ceramic Nano-Heterostructures By Materials Design: Platforms for Sensing Applications – Opportunities and Challengess

This talk summarizes R&D efforts in the author’s laboratory on the fabrication of oxide nano-heterostructures, exploiting intrinsic material properties, that are highly scalable and do not require use of lithography. One such process creates crystallographically oriented nanofiber arrays of single crystal TiO2 in H2/N2 environment. H2/N2 heat treatment was also used to grow nanofibers on polycrystalline SnO2, showing directional growth on grains with crystal facets. We have also developed a process to create nanofibers of TiO2 on Ti metal/alloys via oxidation under a limited supply of oxygen. In another process, SnO2 nanowires grown from commercial FTO slides using the vapor-liquid-solid (VLS) method were placed in a microwave-assisted hydrothermal chamber where TiO2 nanorods nucleated radially from the SnO2 nanowire cores. We developed yet another interesting nano-structure (nanoislands and/or nanobars) during thermal annealing of an oxide (GDC) on top of another oxide (YSZ) substrate that self-assembles along the softest elastic direction of the substrate. What is common about these structures is that they are fabricated without the use of lithographic techniques and involves simple processes such as gas-phase reactions and stress-driven processes. These nano-heterostructures can be used as platforms for chemical sensing, catalysis, photocatalysis, photovoltaics and biomedical applications. Sensing application presents opportunities and challenges that are presented including an Open access Database Of Resistive type gas Sensors (ODORS) that has been developed and can be used to select suitable sensing materials.

Fabrication of TiO2: Nb array films and their enhanced electrochromic performance

In this work, Nb-doped TiO2 (NTO) array films were prepared on indium tin oxide (ITO) glasses via laser interferometry combined with the photosensitive sol–gel technique. The electrochromic properties of the NTO film with smooth surface and the one with array structure were compared. The results reveal that the both kinds of films have the property of selectively and independently spectral control over optical transmittance in the Visible (Vis) and near-infrared (NIR) regimes. Moreover, the NTO array film exhibits more superior electrochromic performance. The optical contrast of the NTO array film is 19.68% (in the NIR region) and 9.58% (in the Vis region) higher than that of the NTO film. The coloring time (tc) and bleaching time (tb) are tested to be 17 s and 3 s, which shortened 9 s and 4 s compared to NTO film. The enhanced electrochromism originates from the enhancement of the local surface plasmon resonance (LSPR) of the array.

Construction of TiO2@C@Prussian Blue core-shell nanorod arrays for enhanced electrochromic switching speed and cycle stability

In this study, a novel TiO2@[email protected] Blue core-shell nanorod arrays film was constructed through two-step hydrothermal and electrodeposition methods. Such a designed structure could increase the specific surface area, reactive site, and conductivity of Prussian Blue (PB) and reduce the diffusion distance of ions due to the nano-architecture arrays of TiO2 and the high conductivity of the carbon layer, thus leading to the remarkably improved storage capacity and reaction speed of ions during the electrochromic (EC) process of PB. Moreover, porous morphology and strong adhesion on the FTO substrate of the TiO2 nanorod arrays could alleviate the lattice stress and volume expansion and enhance the binding force, thus improving the cycle stability of EC. Given these benefits, the TiO2@[email protected] films display a large optical modulation range (67%), fast switching speed (tc/tb = 1.25 s/2.71 s), and high coloration efficiency (129.4 cm2/C). In particular, the EC cycle stability is remarkably improved (96.3% after 5000 cycles), implying a promising application in high-performance EC devices (ECDs).

Hot carrier extraction from plasmonic-photonic superimposed heterostructures.

Plasmonic nanostructures have been exploited in photochemical and photocatalytic processes owing to their surface plasmon resonance characteristics. This unique property generates photoinduced potentials and currents capable of driving chemical reactions. However, these processes are hampered by low photon conversion and utilization efficiencies, which are issues that need to be addressed. In this study, we integrate plasmonic photochemistry and simple tunable heterostructure characteristics of a dielectric photonic crystal for the effective control of electromagnetic energy below the diffraction limit of light. The nanostructure comprises high-density Ag nanoparticles on nanocavity arrays of SrTiO3 and TiO2, where two oxides constitute a chemical heterojunction. Such a nanostructure is designed to form intense electric fields and a vectorial electron flow channel of Ag → SrTiO3 → TiO2. When the plasmonic absorption of Ag nanoparticles matched the photonic stopband, we observed an apparent quantum yield of 3.1 × 10-4 e- per absorbed photon. The contributions of light confinement and charge separation to the enhanced photocurrent were evaluated.

Three dimensional BaTiO3 piezoelectric ceramics coated with TiO2 nanoarray for high performance of piezo-photoelectric catalysis

Persistent organic pollution (POPS) with the feature of difficult to be degraded, highly toxic and global spread has become a challenge for the whole human beings. Recently, piezo-photoelectric catalysis is emerging as a promising way to degrade organic pollutions. In order to avoid the secondary pollution caused by the difficult recycling of powder catalyst, a three-dimensional barium titanate (BaTiO3, BT) scaffold is prepared by direct writing technique in this study, of which the surface is decorated by titanium oxide (TiO2, TO) nanowire arrays. Piezoelectric potential can be generated in the BT scaffold, especially in the direction parallel to the direct writing printing, and the piezoelectric electric field can effectively promote the separation of photo-generated carriers. This design of the structure can effectively produce a larger deformation compared with the bulk structure in the catalytic process, and it can also increase the contact area between the catalyzer and solution with enhanced reactive site. Due to the piezo-phototronic coupling effect, BT piezoelectric ceramic scaffold with TiO2 array exhibits an excellent dye degradation efficiency, of which the rate constant reaches approximately 0.109 min−1 for 100 mL of 10 mg/L of indigo carmine (IC) degradation. This work demonstrated that 3D piezoelectric ceramics by direct ink writing method shows a great potential in promoting the practical application of catalysis.

TiO2 nanotube electrode for organic degradation coupled with flow-electrode capacitive deionization for brackish water desalination

A photoelectrochemical (PEC) oxidation and flow-electrode capacitive deionization (FCDI) dual system was explored for the effective treatment of brackish water. Two anodic electrodes with electrochemically self-doped TiO2 arrays (blue-mesh/ blue-plate TiO2 nanotube arrays (BM-TNA & BP-TNA)) were fabricated by annealing at 600 °C, and applied for the treatment of a water system. Specifically, the BM-TNA confirmed lower electrical resistance and superior performance under multiple light source (UV-A, -B, and -C). Furthermore, the system generated powerful oxidizing reactive oxygen species (ROS), which were assessed via degradation of eight organic pollutants: bisphenol-A, 4-chlorophenol, cimetidine, sulfamethoxazole, benzoic acid, phenol, nitrobenzene, and acetaminophen. Decomposition efficiency was stable throughout a wide range of pH, and durability of the BM-TNA electrode was demonstrated through long-term operation. Concurrently, optimization of the FCDI process via key operational parameters (electrode mass loading, and applied voltage) achieved superior desalination performance, and specific energy consumption (SEC). In particular, increased mass loading enhanced charge transportation through the formation of stable charge-percolation pathways, leading to improved solution conductance. Finally, the feasibility of the dual system (PEC-FCDI) was verified through complete degradation of the organic substrates and successful desalination of the brackish water.

Strengthening PPy/TiO2 arrayed SiOC honeycombs for self-protective gas sensing

As the operation reliability for gas sensors under complex environments is in increasing demand, the stability and safety performance are significant besides qualified gas sensing properties. In this work, structural-strengthened and self-protective ammonia sensing micro-tunnels were constructed by 3D printing. Modified methyl-silsesquioxane (MK) resin was employed as the feedstock to build the SiOC honeycomb structures. Polypyrrole (PPy) nanoparticle decorated TiO2 arrays sensitized the structures to form inner gas-sensitive tunnels. The sensing structure exhibited high selectivity toward ammonia at room temperature. Response to 50 ppm NH3 was 18.67%, while the response and recovery times were 119 and 86 s, respectively. The excellent long-term stability also ensured reliable operation in complex environments. More importantly, the enhanced honeycomb had an outstanding mechanical performance with the compressive strength, Young's modulus, and energy absorption of 33.72 MPa, 2.40 GPa, and 28.22 kJ/m3, respectively. It can serve as a load-bearing part of the fundamental component to avoid catastrophic collapse while maintaining a regular sensing capability under pressure loading as the excellent deformation resistance ensured the integrity and connection of the sensing layer. Moreover, the inner through-holes facilitated the exposure of the sensing tunnels to the atmosphere, which can detect target gas simultaneously without the embedding of extra sensors. Thus, the construction of self-protective gas sensing structures was promising to be an efficient strategy for reliable gas detection in extreme environments.

Influence of the Electronic Properties of the Ligand on the Photoelectrochemical Behavior of Au25 Nanocluster-Sensitized TiO2 Photoanode

Atomically precise metal nanoclusters (NCs) have recently emerged as a new class of bifunctional (photoactive and catalytically active) photosensitizers in light energy conversion applications. Despite the size and alloy effects of NCs, no effort has been made to elucidate how the protecting ligand affects the photoelectrochemistry of the NC-sensitized photoelectrodes. With a nanoporous TiO2 array as model support, Au25 NCs protected by various thiol-bearing ligands have been used to prepare four different photoanodes. It is revealed that a subtle change of the ligand from an alkanethiol to an aromatic thiol facilitates the charge transfer between the NC and TiO2, which in turn improves the photoelectrochemical performance of the corresponding photoanode by at least 6 times. This new insight highlights the importance of the electronic properties of the ligand on the design of more efficient NC-sensitized photoelectrodes.

Modulation of titania nanoflower arrays transformed from titanate nanowire arrays to boost photocatalytic Cr(vi) detoxification

The integration of the N/S co-doping, anatase/rutile junction construction, and morphology regulation of TiO2 arrays is achieved by a simple method to improve photocatalytic activity.