Boosting the visible-light photoelectrochemical performance of C3N4 by coupling with TiO2 and carbon nanotubes: An organic/inorganic hybrid photocatalyst nanocomposite for photoelectrochemical water spitting

Developing photoanode with proficient sunlight harvesting, stability as well as enhancing the electron injection across the interface remains a major challenge in the photoelectrochemical water splitting strategy to generate hydrogen. Herein, we design and fabricate an organic/inorganic TiO₂/C₃N₄/CNT photoanode by a hydrothermal technique which exhibits much enhanced photoelectrochemical properties. The TiO₂/C₃N₄/CNT photoanode exhibits a photocurrent density of 2.94 mA/cm², which is ~6.4 time higher than pristine graphitic carbon nitride (C₃N₄) at an applied bias potential of 0.6 V vs. Ag/AgCl. The excellent photoelectrochemical performance benefits from the impactful migration of photo-induced electrons at the TiO₂/C₃N₄ interface from C₃N₄ to TiO₂ and their intimate interface contact with CNT. Kelvin probe force microscopy result shows a smaller interface barrier height (~10 meV) between TiO₂ and C₃N₄, suggesting that electrons transport is favored through TiO₂/C₃N₄ interfaces in a ternary photoanode. The TiO₂/C₃N₄/CNT photoanode exhibited an onset potential of 0.25 V vs. Ag/AgCl which is much lower compared to pristine C₃N_4. The electrochemical impedance spectroscopy results also confirmed the enhanced electron injection across the interface in a ternary photoanode. These results demonstrate a promising approach to develop a highly proficient and visible light active photoanode with excellent stability for renewable energy applications.     

Photoelectrochemical water splitting with black Ni/Si-doped TiO2 nanostructures

Black Ni/Si-doped TiO₂ nanostructures were successfully fabricated through electrochemical anodization of Ti–1Ni–5Si alloy and Sn-reduction treatment. After Sn-reduction treatment, the band gap of Ni/Si-doped TiO₂ became much smaller compared to other samples, which can be attributed to the synergetic effect of Ni/Si doping and the large quantity of Ti³⁺/oxygen vacancy species induced by Sn-reduction treatment. The black Ni/Si-doped TiO₂ nanostructures exhibited a remarkable enhancement in the photoelectrochemical (PEC) water splitting in comparison with the pure TiO₂ and Ni/Si-doped TiO₂. The highest photocurrent reached 2.15 mA/cm² (at 0 V versus Ag/AgCl), corresponding to a conversion efficiency (~1.10%) which was 5.8 times that of the pure TiO₂ nanotubes. The first-principles calculations using density-functional theory (DFT) showed that ion doping and self-doped Ti³⁺ defect levels in the forbidden gap induced through Sn-reduction treatment could improve the mobility of photogenerated carriers and suppress charge recombination, which was in well agreement with the experimental results.     

Construction of three-dimensional hierarchical Pt/TiO2@C nanowires with enhanced methanol oxidation properties

Three-dimensional (3D) hierarchical Pt/TiO₂@C core-shell nanowire networks with high surface area have been constructed via wet chemical approaches. The 3D TiO₂ nanowire framework was in situ synthesized within a porous titanium foam by hydrothermal method followed by carbon coating and self-assembled growth of ultrathin Pt nanowires. Structural characterization indicates that single crystalline ultrathin Pt nanowires of 3–5 nm in diameter were vertically distributed on the anatase TiO₂ nanowires covered with a 2–4 nm thin carbon layer. The 3D hierarchical Pt/TiO₂@C nanostructure demonstrates evidently higher catalytic activities towards methanol oxidation than the commercial Pt/C catalyst. The catalytic current density of the hierarchical catalyst is 1.6 times as high as that of the commercial Pt/C, and the oxidation onset potential (0.35 V vs. Ag/AgCl) is more negative than the commercial one (0.46 V vs. Ag/AgCl). Synergistic effect between the ultrathin Pt nanowires and the TiO₂@C core-shell nanostructure accounts for the enhanced catalytic properties, which can be determined by X-ray photoelectron spectroscopy (XPS) investigation. The obtained hierarchical Pt/TiO₂@C nanowire networks promise great potential in producing anode catalysts for direct methanol fuel cells applications.     

Room‐temperature synthesis of TiO2 nanospheres and their solar driven photoelectrochemical hydrogen production

Highly monodisperse and crystalline anatase phase TiO₂ nanospheres have been synthesized at room temperature from organometallic precursor, titanocene dichloride and sodium azide. The photoelectrochemical (PEC) water splitting performance on the TiO₂ nanospheres was studied under illumination of AM 1.5G. The optimized photocurrent density and photoconversion efficiency of TiO₂ NSPs were observed ~0.95 mA cm^?2 at 1.23 V and 0.69%, respectively. The transient photocurrent response measurements on the TiO₂ NSPs during repeated ON/OFF visible light illumination cycles at 1.23 V vs RHE show that both samples exhibited fast and reproducible photocurrent responses. The TiO₂ NSPs show excellent catalytic stability, and significant dark current was not observed even at high potentials (2.0 V vs RHE). Copyright © 2015 John Wiley & Sons, Ltd.     

Electrochemical reduction induced self-doping of oxygen vacancies into Ti–Si–O nanotubes as efficient photoanode for boosted photoelectrochemical water splitting

Self-doping of oxygen vacancies (V_O) states into TiO₂-based nanotubes was an efficient way for improving photoelectrochemical (PEC) water splitting properties. Here we induced oxygen vacancies into Si-doped TiO₂ (Ti–Si–O) nanotubes on Ti–Si alloy via a facile electrochemical surface reduction, and applied it for PEC water splitting. Systematic studies revealed that the self-doped oxygen vacancies not only promoted optical absorption of the doped nanotubes but also enhanced separation-transport processes of the photo-generated charge carriers, and thus resulted in improved PEC water splitting properties. The V_O/Ti–Si–O co-doping system exhibited a higher photocurrent density of 1.63 mA/cm² at 0 V vs. Ag/AgCl. Corresponding solar-to-hydrogen efficiency could reach 0.81%, which was about 5.4 times that of undoped TiO₂. It's believed that elements doping and oxygen vacancies self-doping synergistic strategy employed in this work, may provide theoretical and practical significance for designing and fabricating efficient TiO₂-based nanostructures photoanodes in PEC water splitting for boosted solar-to-hydrogen conversion.     

In situ synthesis of MoO3/Ag/TiO2 nanotube arrays for enhancement of visible-light photoelectrochemical performance

A ternary composites of MoO₃/Ag/TiO₂ nanotube arrays were synthesized by in-situ annealing of TiO₂ nanotube arrays impregnated with AgNO₃ over MoO₃ powders. During the annealing process, the crystallization of the TiO₂ nanotubes, the thermo-decomposition of AgNO₃ to Ag nanoparticles, and the sublimation of MoO₃ occur jointly. The photoelectrochemical measurements of the resultants indicate that MoO₃/Ag/TiO₂ nanotube arrays present better photoelectrochemical properties compared with Ag/TiO₂ nanotube arrays and pristine TiO₂ nanotube arrays. Especially, the highest photocurrent and open circuit voltage are up to 21.29 μA/cm² and 0.058 V under visible light irradiation, whereas 1.77 and 3.87 times larger than those of TiO₂ nanotube arrays, respectively. Superior photoelectrochemical stability and larger photo-conversion efficiency of the ternary composites are also demonstrated. The improved photoelectrochemical properties are related to the close interfacial contact among MoO₃, Ag, and TiO₂ as well as the surface plasma resonance of Ag in the ternary composites, which broaden the range of light response and enhance the efficiency of charge separation. This study provides a skillful solution to construct TiO₂-based composite materials and demonstrates it is an unique architecture to promote the visible light driven photocatalytic application of TiO₂.     

Core-shell hetero-phase reduced Ti–Ni–O nanotubes photoanode with enhanced optical absorption and charge transport for boosted photoelectrochemical water splitting

Bulk-phase doping and surface oxygen-defective engineering of TiO₂-based nanostructures are identified as effective routes for enhanced photoelectrochemical (PEC) water splitting. Here, we reported a reduced Ti–Ni–O nanotubes photoanode with anatase-rutile crystalline-core and oxygen vavancies amorphous-shell for boosted PEC water splitting. The core-shell hetero-phase reduced Ti–Ni–O nanotubes were fabricated through phase-structure modulation by a thermal treatment of anodized Ti–Ni–O nanotubes on Ti–Ni alloy and with one-step electrochemical reduction. Microstructure, optical and PEC measurement results confirmed effective bulk-phase Ni-doping and surface oxygen vacancies self-doping into the reduced mixed-phase Ti–Ni–O nanotubes, which enabled high capability of optical-absorption and simultaneously favored charge separation-transfer for remarkably improved the PEC water splitting. A higher photocurrent density of 1.66 mA/cm² at 0 V vs. Ag/AgCl and solar-to-hydrogen efficiency of 0.79% were achieved for the reduced Ti–Ni–O system, which was 5.35 and 5.27 times that of undoped TiO₂, respectively. This work may shed an insight view on fabricating high-performance Ti-based nano-photoanodes with enhanced light harvesting and carrier kinetics for efficient PEC water splitting, through synergistic strategy of bulk-phase elements doping and surface oxygen vacancies self-doping.     

Physicochemical and morphological properties of spin-coated poly(3-alkylthiophene) thin films

Poly(3-hexylthiophene) (P3HT) and poly(3-octylthiophene) (P3OT) were synthesized by direct oxidation of the respective monomers with FeCl₃ as oxidant/catalyst. It was observed that the type of monomer affected the molecular weight and polydispersity as well as degree of regioregularity of the polymer, measured by size exclusion chromatography and by ¹H nuclear magnetic resonance, respectively. Homogeneous P3HT and P3OT films were prepared by spin-coating technique with different polymer concentration in solutions. Morphology study with atomic force microscopy indicates the cluster size difference between P3HT and P3OT films. Optical absorption properties of the polymeric films were analyzed in pristine and doped state. The electrochemical characterization of the poly(3-alquilthiophenes) (P3Ats) films showed two oxidation peaks, one at 0.35 V vs. Ag/AgCl, and the second one at 0.8 V vs. Ag/AgCl. The colors of the film at these two potentials were black and blue, respectively.     

Formation of single-crystalline rutile TiO2 splitting microspheres for dye-sensitized solar cells

The morphological evolution of specimen taken out after the different duration in TiCl₃ solution was investigated by field emission scanning electron microscopy (FE-SEM). The rutile TiO₂ splitting microspheres may be formed by the splitting crystal growth mechanism through the multistep process. The microsphere composed of the 20 nm width nanorods was in the range of 1.5–2.5 μm in the diameter. The dye-sensitized solar cell (DSC) based on the microspheres received 3.57% conversion efficiency under simulated AM 1.5 (100 mW/cm²) solar illumination, which exhibited remarkably higher charge collection efficiency and light scattering compared to that of P25. Electrochemical impedance spectroscopy (EIS) measurement revealed that impedance resistance at the surface of single-crystalline rutile TiO₂ splitting microspheres was 6 times larger than that of P25 nanoparticles, indicating electron recombination was significantly retarded.     

Fabrication of IrO2 decorated vertical aligned self-doped TiO2 nanotube arrays for oxygen evolution in water electrolysis

To fabricate effective and stable OER electrode in water electrolysis, self-doped TiO₂ nanotube arrays which has a higher electrical conductivity than pristine TiO₂ nanotube arrays was used as the support for loading IrO₂. The self-doped TNTA was fabricated by a simple electrochemical reduction of TNTA in neutral electrolyte solution, and then IrO₂ nano particles were deposited by pulse electro-deposition method. The cyclic voltammetric behavior, electrical conductivity and micro structure of self-doped TNTA prepared at different reduction potential were characterized to obtain an optimal performance, and self-doped TNTA prepared under ?1.9 V (vs. Ag/AgCl) shows the best electrochemical performance. After depositing IrO₂, the OER activity and stability of new electrodes were also determined. Due to the enhanced electrical conductivity of support, the mass activity of IrO₂/self-doped TNTA are 50 times higher than IrO₂/TNTA. The OER stability of new electrode was evaluated under constant current of 5 mA/cm², IrO₂/TNTA and IrO₂/Ti were also tested for comparison. A higher stability of IrO₂/self-doped TNTA electrode is observed than the other two electrodes, and XPS studies indicate a lower oxidation state of Ir in IrO₂/self-doped TNTA, this shows a possible interactions between IrO₂ and the new support.     

Laser induced formation of copper species over TiO2 nanotubes towards enhanced water splitting performance

We proposed fast and scalable route where the ordered TiO₂ nanotubes coated with thin copper layers were annealed by the laser beam of 355 nm wavelength at different fluencies in the range of 15–120 mJ/cm². As a result, copper species are integrated with the titania substrate and the formed material exhibits unique optical absorption bands in the visible range. Moreover, X-ray photoelectron spectroscopy analysis reveals the formation of Cu₂O while the 4⁺ oxidation state of titanium is preserved. According to the electrochemical results, the material treated by laser exhibits outstanding photoelectrochemical activity comparing to the pristine titania or the one only covered by the thin copper film. In particular, when the fluence of 60 mJ/cm² was used for the modification of the titania decorated with Cu film, the current density recorded in KOH electrolyte reaches nearly 4.5 mA/cm² at +2.0 V vs. Ag/AgCl/0.1 M KCl upon visible light.     

Controlled synthesis of MnO2@TiO2 hybrid nanotube arrays with enhanced oxygen evolution reaction performance

A novel tube-in-tube nanostructure of MnO₂@ TiO₂ hybrid arrays has been obtained by a facile and controllable chemical bath deposition method. Scrutiny on the hybrid arrays indicates that the chemical bath deposition method favors the growth of the MnO₂ nanotubes with different diameter which can modulate the oxygen evolution reaction (OER) activity as well as bandgap width of the hybrid. In terms of OER activity, onset potential (E_s) shifts negatively from 0.698 V (vs.Ag/AgCl) of pristine titania nanotube arrays (TNAs) to 0.501 V of the hybrid loaded with 26.6%wt MnO₂, and the current density on the hybrid electrode can be significantly enhanced up to 20.87 mA/cm², almost 97 times higher than that on TNAs electrode (0.214 mA/cm²). Optical absorption measurement suggests that the bandgap width (E_g) can be tuned by loading MnO₂ onto the TNAs implying interaction between the MnO₂ and TNAs. The MnO₂@TiO₂ hybrid nanotube arrays may find promising potential in electrochemical water splitting, photocatalysis, thermocatalysis and other sustainable energy applications.     

Construction of CdSe@TiO2 core‐shell nanorod arrays by electrochemical deposition for efficient visible light photoelectrochemical performance

The CdSe@TiO₂ core‐shell nanorod arrays for photoelectrochemical (PEC) application were designed and constructed by a facile electrochemical deposition strategy. The CdSe@TiO₂ photoanodes exhibit highly efficient PEC performance under visible light irradiation, among which the CdSe shell layer thickness can be precisely adjusted by different electrodeposition time. In comparison with nude TiO₂ nanorods, the optimized CdSe@TiO₂ photoanode (TC‐500) shows a significant saturated photocurrent density of 2.1 mA/cm² at 0 V (vs Ag/AgCl), which is attributed to the good distribution of CdSe nanoparticles on TiO₂ nanorod arrays, the favorable band alignment, and the intimate interfacial interaction between CdSe nanoparticles and TiO₂ nanorods. The introduction of CdSe shell layer does not only improve light absorption ability but also enhances photogenerated charge carrier's transfer and separation. This current work systematically studies the accurate adjustment of CdSe shell layer thickness on TiO₂ nanorod arrays by electrochemical deposition strategy and provides a paradigm to design and fabricate heterostructure composite for PEC application.     

Insight into effects of graphene and zinc oxide in Li4Ti5O12 as anode materials for Li-ion full-cell battery

Programmable design of nanocomposites of Li₄Ti₅O₁₂ (LTO) conducted through hydrothermal route in the presence of ethylenediamine as basic and capping agent. In this work, effect of ZnO and Graphene on the Li₄Ti₅O₁₂ based nanocomposites as anode materials investigated for Li-Ion battery performances. The full cells battery assembled with LTO based nanocomposites on Cu foil as the anode electrode and commercial LMO (LiMn₂O₄) on aluminum foil as cathode electrode. X-Ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), along with Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission electron microscopy (TEM) images was applied for study the composition and structure of as-prepared samples. The electrochemical lithium storage capacity of prepared nanocomposites was compared with pristine LTO via chronopotentiometry charge-discharge techniques at 1.5–4.0 V and current rate of 100 mA/g. As a result, the electrode which is provided by LTO/TiO₂/ZnO and LTO/TiO₂/graphene nanocomposites provided 765 and 670 mAh/g discharge capacity compared with pristine LTO/TiO₂ (550 mAh/g) after 15 cycles. Based on the obtained results, fabricated nanocomposites can be promising compounds to improve the electrochemical performance of lithium storage.     

Enhanced photoelectrochemical response of reduced-graphene oxide/Zn1−xAgxO nanocomposite in visible-light region

Graphene based nanocomposites have the potential to work as efficiently, multifunctional materials for energy conversion & storage. These composites may exhibit better photocatalytic properties by the improvement of their electronic and structural properties than pure photocatalysts. In the present work, reduced graphene oxide (rGO) & ZnO nanocomposite with 0–5 atom% Ag doping was prepared by electrodeposition method and characterized by XRD, Raman spectroscopy, FE-SEM, EDX, UV–Vis spectroscopy and final photoelectrochemical activity was assessed under 1.5 AM solar simulator in 1 M NaOH as electrolyte. Significant changes in the Raman spectrum for the nanocomposite suggest the possible electronic interaction between rGO and ZnO nanocomposite and its successful fabrication, which improves the charge separation and enhanced photoelectrochemical activity in the nanocomposite. We find a red-shift of 0.35 eV in the UV–vis spectrum and therefore an enhanced photoelectrochemical activity in the visible range on Ag doping in rGO/ZnO nanocomposite. Nanocomposite with 1 atom% Ag doping showed the highest photocurrent density of 2.48 mA/cm² at 0.8 V vs Ag/AgCl over other samples, which was almost five times higher than that for undoped rGO/ZnO composite. Calculated Flat-band potential and donor densities using Mott–Schottky data also supported the better photoelectrochemical response for Ag doping in nanocomposite.     

Test of conductor and semiconductor electrocatalysts in high voltage alkaline electrolyzer as production media for green hydrogen

Despite the restricted success of conductor and semiconductor electrodes in solving hydrogen production problems, they provide a promising alternative to expensive conventional electrodes in water electrolysis investigations. Titanium dioxide (TiO₂) and silver (Ag) are widely used as photocatalysts in water splitting systems for hydrogen generation. Though TiO₂ is an inactive chemical semiconductor with poor conductivity, it has not been entirely investigated as an electrocatalyst yet. Two criteria were used to achieve this target: supplying high voltage to overcome the TiO₂ large band gap and immersing it in an alkaline solution to activate its inert surface. For comparison study, Ag noble metal nanoparticles coating was employed as a competitive electrocatalyst. In this regard, the application of Ag and TiO₂ coated on Ti electrodes in a hydrogen production system operated under high voltage was reported. The nanoparticles were synthesized using cost-effective and simple methods based on UV-deposition for Ag nanoparticles and the chemical precipitation method for TiO₂ nanoparticles. Then the synthesized nanoparticles were deposited on the Ti electrodes by simple immersion. The synthesized nanoparticles and coated electrodes were tested by XRD, SEM, and EDS to study their morphology, structure, particle size, and surface composition. Based on these results, TiO₂ nano-powder and coated electrodes exhibited homogenous spheres with a mixture of rutile and anatase phases, the majority being the anatase phase. The Ag-coated Ti substrate possessed a smaller crystallite size compared to TiO₂ coated substrate. To evaluate the performance of Ag/Ti and TiO₂/Ti electrodes toward hydrogen production, H₂ flow rates were measured in a 3.6 M KOH electrolytic solution at 6 V. Hydrogen flow rates obtained for pure Ti, Ag, and TiO₂ electrodes at a steady state were 21, 35, and 37 SCCM (standard cm³/min), respectively. Also, it was found that energy consumption was reduced when the electrodes were coated with nanoparticles. Furthermore, the electrolyzer's performance was assessed by calculating the hydrogen production efficiency and the voltage efficiency. The results showed that using TiO₂ electrodes gave the best hydrogen production and voltage efficiencies of 27% and 23%, respectively. This study brings new insights about Ag and TiO₂ coated electrodes in alkaline water electrolysis at high voltage regarding nanoparticle performance, hydrogen production, system performance, and energy consumption. In addition, minimizing the fabrication and operation costs of hydrogen production is the major enabler for the broad commercialization of water electrolysis devices.     

TiO2 nanoparticles with superior hydrogen evolution and pollutant degradation performance

The human life faces serious energy shortage and environmental pollution problems, therefore developing a facile and environmental friendly strategy for synthesizing nanoparticles (NPs) with improved photocatalytic activity could pave the way for different applications. In the present study, one-pot/in-situ fluorine-free synthesis process has been examined toward the solvothermal production of anatase TiO₂ nanoparticles with exposed facet orientation. This is an aim to achieve the excellent photocatalytic/photoelectrocatalytic performance. Most importantly addressing the global energy shortage, the synthesized TiO₂ NPs represent superior performance in photoelectrocatalytic water splitting toward hydrogen production. The overpotential required to drive the hydrogen evolution reaction was −391, −346 and −283 mV vs. Ag/AgCl for P25, cubic and truncated octahedral NPs, respectively. Additionally, TiO₂ NPs with exposed facets represent excellent photocatalytic performance toward environmental purification. As synthesized nanoparticles was examined via photocatalytic degradation of Acid Blue 5 and photocatalytic removal of NO gas. The enhanced photocatalytic and photoelectrocatalytic performance are associated to the effect of exposed facet orientation of final nanoparticles.     

Construction of ZnO@NiO heterostructure photoelectrodes for improved photoelectrochemical performance

In this report, a p-n junction has been constructed using ZnO/NiO heterostructured photoelectrode by spin coating NiO layers over vertically aligned ZnO nanorod arrays to demonstrate its potential in water splitting applications. Before investigating their PEC performance, we thoroughly studied the introduction of NiO layers on the structure, morphology and light absorption property of ZnO nanorods. 9 layered NiO coated ZnO nanorods exhibited optimum photocurrent density of 0.251 mA/cm² at 0.8 V vs. Ag/AgCl which is attributed to its high absorbance and better charge transfer as recorded from UV–Vis and EIS data. Furthermore, we also studied the effect of (cation (Mg) and anion (Cl)) doping in PEC performance of ZnO nanorods on this optimized sample. Cl_ZnO/NiO showed high J_ph of 1.282 mA/cm² at 1.2 V vs. Ag/AgCl under visible light illumination. The reason behind better photoresponse is its enhanced absorption and well-defined p-n heterojunction between Cl_ZnO and NiO which favoured the separation and transfer of the photocarriers. The results displayed in this work provides a suitable approach of building p-n junction for high performance PEC water oxidation.     

Photocatalytic water oxidation at bismuth vanadate thin film electrodes grown by direct liquid injection chemical vapor deposition method

Photoelectrochemical cells (PECs) are devices that can harvest and convert solar energy to produce consumable fuel, e.g. by splitting water into oxygen and hydrogen. Photocatalytic semiconductor materials play a major role in PECs, and their overall efficiency is usually limited by short carrier diffusion length because of structural defects, poor light absorptivity, and sluggish kinetics of photoelectrochemical reactions at the semiconductor electrode. Synthesis of high quality defect-free semiconductor materials using high temperature deposition techniques generally yield films with good adhesion to substrates while improving charge carrier transport and hence the overall efficiency of a PEC. A direct liquid injection chemical vapor deposition (DLI-CVD) technique has been utilized to synthesize monoclinic clinobisvanite phase bismuth vanadate (BiVO₄) films for photocatalytic water oxidation. The technique yields dense high quality epitaxial and polycrystalline BiVO₄ films on Yttria stabilized zirconia (YSZ) and Fluorine doped tin oxide (FTO) substrates, respectively, at growth temperature in the range of 500–550 °C. The photoelectrochemical characteristics of the films grown on FTO have been studied and a photocurrent value of 2.1 mA/cm² at 1.23 V vs Normal hydrogen electrode (NHE) (0.5 V vs. Ag/AgCl), with onset potential values as low as 0.23 V vs. NHE (?0.5 V vs. Ag/AgCl), are obtained despite the low porosity of the films. The PEC performance is further improved by synthesizing BiVO₄ directly on top of a tungsten oxide interlayer and modifying its surface with FeOOH co-catalyst.     

Preparation and enhanced photoelectrocatalytic properties of a three-dimensional TiO2-Au porous structure fabricated using superaligned carbon nanotube films

Three dimensional TiO₂–Au cross-nanoporous structure (3D TiO₂–Au CNS) as an efficient photoelectrocatalytic system was fabricated using superaligned carbon nanotube films as etching masks and electron-beam evaporation. The 3D TiO₂–Au CNS exhibited a broad absorption band in the visible region, and the incident photon-to-current conversion efficiency of 3D TiO₂–Au CNS/Ti electrode was 3–4 times higher than that of pure TiO₂ electrode. The photocurrent density of the 3D TiO₂–Au CNS device was 0.079 mA cm⁻² at 0 V vs. Ag/AgCl with a solar irradiance of 100 mW cm⁻². This developed preparation method was simple, of high flexibility and can be adopted for mass production due to its low cost and good compatibility with other processing technologies. The 3D TiO₂–Au CNS and its preparation method have important value in design of photoelectrocatalytic system for research and practical applications, which may have a potential utility in photocatalytic and other photoelectrocatalytic reactions.