Structure Of Nanotube Arrays Research Articles

Optimization of Nanostructure and Characterization: Anodization of TiO2 in the Polyethylene Glycol-Based Electrolyte.

The homogeneity and stability of the structure of anodic TiO2 nanotube (ATNT) arrays have been a hot topic in materials synthesis research. In this work, the current density distribution during the anodization of ATNT arrays was optimized by adding polyethylene glycol-600 (PEG-600) to the conventional ethylene glycol-based electrolyte, which enhanced the dependence of the electronic current on the applied voltage, thus providing a stabilizing effect on anodization and improving the homogeneity of the pores on the surface of ATNT arrays. A new image processing approach, called the region-growing method, is reported in this work, which can quantitatively analyze the pore size of ATNT arrays through SEM images, and the surface morphology of ATNT arrays was evaluated based on this. The most stable anodization was obtained with a 50 wt % PEG-600 addition, and the equivalent diameters of the pores prepared at applied voltages of 40, 50, and 60 V were 34.5340, 42.4010, and 50.4791 nm, respectively, with a linear correlation of 0.9999.

Synthesis of P-(NiCo)CO3/TiO2/Ti Self-Supported Electrode with High Catalytic Activity and Stability for Hydrogen Evolution.

Hydrogen is considered an ideal clean energy due to its high mass-energy density, and only water is generated after combustion. Water electrolysis is a sustainable method of obtaining a usable amount of pure hydrogen among the various hydrogen production methods. However, its development is still limited by applying expensive noble metal catalysts. Here, the dissolution-recrystallization process of TiO2 nanotube arrays in water with the hydrothermal reaction of a typical nickel-cobalt hydroxide synthesis process followed by phosphating to prepare a self-supported electrode with (NiCo)CO3/TiO2 heterostructure named P-(NiCo)CO3/TiO2/Ti electrode is combined. The electrode exhibits an ultra-low overpotential of 31mV at 10mA cm-2 with a Tafel slope of 46.2mVdec-1 in 1m KOH and maintained its stability after running for 500h in 1m KOH. The excellent catalytic activity can be attributed to the structure of nanotube arrays with high specific surface area, superhydrophilicity, and super aerophobicity on the electrode surface. In addition, the uniform (NiCo)CO3/TiO2 heterostructure also accelerates the electron transfer on the electrode surface. Finally, DFT calculations demonstrate that phosphating also improves the ΔGH* and ΔGH2O of the electrode. The synthesis strategy also promotes the exploration of catalysts for other necessary electrocatalytic fields.

Controlled assembly of novel Fe2O3/MgFe2O4 nanotubular array structures for rapid detection of dibutylamine

The development of an efficient, fast, and real-time sensor for detecting dibutylamine (C8H19N) gas remains challenging. In this study, a simple controllable and environmentally friendly solvothermal method was used to construct novel Fe2O3/MgFe2O4 nanotube array structures with heterointerfaces. The array structure exhibits a relatively large specific surface area and high-activity heterointerfaces. These features greatly promote the diffusion and adsorption of gas molecules onto the sensitive layer, effectively increasing the surface-adsorbed oxygen species and active sites of the sensing material. The sensing performance of the Fe2O3/MgFe2O4 array structure for C8H19N gas is greatly improved due to the synergistic effect of these multiple factors. The sensor showed a high response of 92.6 to 100 ppm C8H19N at 170 °C, with a short response time of 3.6 s and an ultra-low detection limit of 10 ppb. The sensitization mechanism of Fe2O3/MgFe2O4 to C8H19N was investigated by combining theoretical calculations and experimental techniques. This study broadens the application of gas sensors for the detection of volatile organic compounds (VOCs).

TiO2 Nanotubes Decorated with Mo2C for Enhanced Photoelectrochemical Water-Splitting Properties.

The presence of Ti3+ in the structure of TiO2 nanotube arrays (NTs) has been shown to enhance the photoelectrochemical (PEC) water-splitting performance of these NTs, leading to improved results compared to pristine anatase TiO2 NTs. To further improve the properties related to PEC performance, we successfully produced TiO2 NTs using a two-step electrochemical anodization technique, followed by annealing at a temperature of 450 °C. Subsequently, Mo2C was decorated onto the NTs by dip coating them with precursors at varying concentrations and times. The presence of anatase TiO2 and Ti3O5 phases within the TiO2 NTs was confirmed through X-ray diffraction (XRD) analysis. The TiO2 NTs that were decorated with Mo2C demonstrated a photocurrent density of approximately 1.4 mA cm-2, a value that is approximately five times greater than the photocurrent density exhibited by the bare TiO2 NTs, which was approximately 0.21 mA cm-2. The observed increase in photocurrent density can be ascribed to the incorporation of Mo2C as a cocatalyst, which significantly enhances the photocatalytic characteristics of the TiO2 NTs. The successful deposition of Mo2C onto the TiO2 NTs was further corroborated by the characterization techniques utilized. The utilization of field emission scanning electron microscopy (FESEM) allowed for the observation of Mo2C particles on the surface of TiO2 NTs. To validate the composition and optical characteristics of the decorated NTs, X-ray photoelectron spectroscopy (XPS) and UV absorbance analysis were performed. This study introduces a potentially effective method for developing efficient photoelectrodes based on TiO2 for environmentally sustainable hydrogen production through the use of photoelectrochemical water-splitting devices. The utilization of Mo2C as a cocatalyst on TiO2 NTs presents opportunities for the advancement of effective and environmentally friendly photoelectrochemical (PEC) systems.

In-situ controllable assembly of 3D ZnO-ZnS heterojunction nanotube arrays for enhancing NO2-sensing performance at low energy consumption and sensing mechanism

The ZnO-ZnS composite nanotube arrays were grown in-situ on the ceramic tube substrate via hydrothermal route without any surfactant. ZnS nanoparticles are evenly coated on the surface of ZnO nanotubes to form a large number of nano-heterojunction structures. The response of the sensor is 14.25–10 ppm NO2 at the optimal operating temperature 170 °C. The lowest detection concentration reaches 0.5 ppm at 170 °C. The sensor also shows perfect selectivity, moisture resistance and long-term stability. The composite of ZnO and ZnS significantly increases the response of sensing material, and even achieves the room temperature response to NO2. The excellent NO2 sensing properties of the sensor are attributed to the unique nanotube arrays structure. It provides more active sites, which facilitates gas molecules to adsorb on the surface of the materials. At the same time, the hollow structure of nanotubes is also conducive to gas molecules diffusion. The detailed sensing mechanism analysis is further proved by techniques such as XPS, GC-MS, UV–Vis and Kelvin probe techniques.

Morphological modulation of NiCo2Se4 nanostructured arrays on carbon cloth and application to asymmetric supercapacitors

Electrode materials determine the electrochemical performance of supercapacitors and are strongly affected by their morphologies. In this paper, NiCo2Se4 with three different morphologies, such as solid nanoneedle array, hollow nanoneedle array, and nanotube array structure have been in situ grown on carbon cloth by a facile two-step hydrothermal method. The microstructures and electrochemical performance of synthesized integrated electrode material (CC@NiCo2Se4) with different morphologies were studied. It was revealed that the volume of solvent during the selenization process had a significant effect on the morphologies and loading capacity of NiCo2Se4, and the hollow nanoneedle array structure electrode (CC@hn-NiCo2Se4) exhibited the highest specific capacitance of 1687.08 F·g−1 at 2 A·g−1, and 70.64% retention even though the current density was increased to 20 A·g−1. Furthermore, the CC@hn-NiCo2Se4//CC@AC asymmetric supercapacitor exhibited an energy density of 30.71 Wh·kg−1 at 800 W·kg−1. All results highlight that NiCo2Se4 with a hollow nanoneedle array structure will be a promising electrode material for practical supercapacitor applications.

Oxygen-Deficient α-MnO2 Nanotube/Graphene/N, P Codoped Porous Carbon Composite Cathode To Achieve High-Performing Zinc-Ion Batteries.

A major drawback of α-MnO2-based zinc-ion batteries (ZIBs) is the poor rate performance and short cycle life. Herein, an oxygen-deficient α-MnO2 nanotube (VO-α-MnO2)-integrated graphene (G) and N, P codoped cross-linked porous carbon nanosheet (CNPK) composite (VO-α-MnO2/CNPK/G) has been prepared for advanced ZIBs. The introduction of VO in MnO2 can decrease the value of the Gibbs free energy of Zn2+ adsorption near VO (ca. -0.73 eV) to the thermal neutral value. The thermal neutral value demonstrates that the Zn2+ adsorption/desorption process on VO-α-MnO2 is more reversible than that on α-MnO2. The as-made Zn/VO-α-MnO2 battery is able to deliver a large capacity of 305.0 mAh g-1 and high energy density up to 408.5 Wh kg-1. The good energy storage properties can be attributed to VO. Additionally, the VO-α-MnO2/CNPK/G composite possesses the structure of nanotube arrays, which results from the vertical growth of α-MnO2 nanotubes on CNPK. This unique array structure helps to realize fast ion/electron transfer and stable microstructure. The electrochemical performance of VO-α-MnO2 has been comprehensively improved by compositing with G and CNPK. The VO-α-MnO2/CNPK/G can achieve capacity up to 405.2 mAh g-1, energy density of 542.2 Wh kg-1, and long cycle life (80% capacity retention after 2000 cycles).

Synergistic enhancement on flexible solid-state supercapacitor based on redox-active Fe3+ions/natural spidroin modified vertically aligned carbon nanotube arrays

The conductive skeleton and aligned carbon nanotube array (CNTA) structure can greatly shorten the ion transfer path and promote the charge transfer speed, which makes the CNTA an ideal electrode material for energy storage application. However, poor mechanical stability and low specific capacitance greatly impede its practical utilization. Here, we introduce a promising flexible electrode material based on the natural spider silk protein (SSP) modified CNTA(SSP/CNTA) with improved hydrophilicity and mechanical flexibility. The redox-active Fe3+ doped SSP/CNTA flexible solid-state supercapacitor (FSSC) device with superior energy storage performance was assembled in a symmetric ‘sandwich-type’ structure. The synergetic interaction between Fe3+ ions and the SSP are proved to greatly enhance the electrochemical performance especially the long-term cyclic stability. The Fe3+ doped SSP/CNTA FSSCs device achieves an ultra-high volumetric capacitance of 4.92 F cm−3 at a sweep speed of 1 mV s−1. Meanwhile it exhibited an excellent cycling stability with an increased capacitance by 10% after 10 000 charge–discharge cycles. As a control, a Fe3+ doped CNTA composite device without SSP will lose over 74% of the capacitance after 10 000 cycles. The energy storage mechanism analysis confirms the dominated capacitive behavior of the device, which explained a considerable power density and rate performance. Our method thus provides a promising strategy to build up highly-efficient redox-enhanced FSSCs for next generation of wearable and implantable electronics.

Encapsulating sulphur inside Magnéli phase Ti4O7 nanotube array for high performance lithium sulphur battery cathode

AbstractThe lithium–sulphur battery is a promising system for next‐generation energy storage because of its high energy density and the abundant supply of sulphur. In this study, Magnéli phase Ti4O7 nanotube arrays (NTA) were grown on titanium nitride mesh substrates via anodization of titanium mesh followed by high‐temperature reduction under a hydrogen atmosphere. When prepared into a composite material with sulphur via electrodeposition, Ti4O7 NTA provides sulphur with high electronic conductivity and strong polysulphide chemisorption during battery operation. The structure of NTA allows sufficient access of incorporated sulphur to the liquid electrolyte and supports high sulphur loadings per unit area of the electrode. The application of an additional layer of conductive carbon coating to confine electrodeposited sulphur inside the NTA further improved the cell cycling performance. Under sulphur loadings of around 2.0 mg/cm2, high values of specific capacity (1604 mAh/g at a 1/20 C rate), ultra‐low capacity decay rate (0.03% per cycle for 1800 cycles), and versatile rate capability (660 mAh/g at 2 C and 500 mAh/g at 4 C) were achieved. Under high sulphur loadings of around 5.0 mg/cm2, stable cycling (decay rate below 0.10% per cycle) and high areal capacity (4.97 mAh/cm2) were attained.

One-step synthesis of N-doped porous wall TiO2 nanotube arrays for efficient removal of dibutyl phthalate under visible light

The N-doped porous wall TiO2 nanotube arrays (N@p-TNTAs) was synthesized by one-step anodization method for the first time. The excellent adsorption performance and visible light response of N@p-TNTAs result in significantly superior photocatalytic activity, due to the porous wall nanotube array structure and the successful doping of N element. The photocatalytic activity of catalyst was evaluated by using the refractory organic pollutants dibutyl phthalate (DBP) as target pollutant. >97 % of DBP was degraded after 3 h of irradiation with visible light, and the degradation kinetic constant was nearly 88 and 9 times higher than that of TiO2 nanotube arrays (TNTAs) and TiN, respectively. During the calcination process, due to the N doping, the orbital of N 2p and O 2p were mixed to produce new valence bands, which effectively shortened the bandgap width of N@p-TNTAs to have visible light response. Meanwhile, a part of N escaped in the form of gas, forming the structure of porous wall. In addition, N@p-TNTAs still showed outstanding photocatalytic activity after 6 cycles, which indicated that the structure of material was stable and can be widely used in environmental photocatalysis.

Controllable preparation of CuCo2S4 nanotube arrays for high-performance hybrid supercapacitors

The CuCo2S4 sulfides were fabricated on Ni foam (NF) through a single-step hydrothermal deposition followed by sulfurization at different times. The results from various spectroscopic and microscopic analyses showed that the 3D hollow nanotube CuCo2S4 arrays were formed by the sulfurization, resulting in a larger contact area with the electrolyte and more active sites with high Faraday efficiency. Benefited from the unique nanotube arrays structure and high crystallinity, the optimized CuCo2S4/NF8 electrode material sulfurized for 8 h displayed superior electrochemical performances with the high specific charge of 458.8 C g − 1 at 1.0 A g − 1 as well as good cycling stability with 96.0% retention at 5.0 A g − 1 after 1 000 cycles. Furthermore, a hybrid supercapacitor device based on the CuCo2S4/NF8 as positive electrode and activated carbon as negative electrode was able to deliver an ultrahigh energy density 51.8 Wh kg−1 at a power density 700.0 W kg−1 with 80.0% capacitance retention at 5.0 A g − 1 after 10 000 cycles. This work provided new insights into the sulfurization process and an effective way to optimize the structure of the transition metal sulfides for supercapacitors.

Self-doped TiO2 nanotube array photoanode for microfluidic all-vanadium photoelectrochemical flow battery

• Self-doped TiO 2 nanotube array photoanode is developed for μVPFB. • Visible-light response of TiO 2 is enabled by self-doping. • Nanotube array structure enhances separation of electron-hole pairs. • The developed photoanode shows enhanced solar energy storage performance. In this work, a self-doped TiO 2 nanotube array (SD-TNA) photoanode was developed through a facile method for a microfluidic all-vanadium photoelectrochemical flow battery (μVPFB) to achieve better solar energy storage performance. The TEM, XPS and XRD results confirmed successful self-doping, for which the light absorption range of the developed photoanode was extended to visible light. Meanwhile, one-dimensional nanotube structure promoted electron transport to enhance the separation of electrons and holes. The miniaturization of the flow battery reduced mass transfer resistance. Because of these merits, the μVPFB with the SD-TNA photoanode yielded a relatively stable photocurrent density as high as 0.10 mA cm −2 , which was much better than the conventional TNA photoanode, presenting about 100% improvement. The improvements in the photocurrent density and vanadium ion conversion rate could be achieved by upgrading both the intensity of light and concentration of vanadium ion.

Structural Characterization and Visible Light-Induced Photoelectrochemical Performance of Fe-Sensitized TiO2 Nanotube Arrays Prepared via Electrodeposition

Surface modification of TiO2 nanotube arrays via metal doping is one of the approaches to narrow the wide bandgap of TiO2 in order to increase its adsorption to the visible region. The present work focuses on the fabrication of a Fe-sensitized TiO2 nanotube arrays (Fe-TNT) photoanode. Ordered Fe-TNTs were successfully synthesized using a facile two-step electrochemical method by varying the deposition voltage (2-4 V). The morphology, structure, composition, and visible light response were characterized by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), UV-Vis diffusion reflection spectroscopy (DRS), and photoelectrochemical (PEC) test. The XRD investigation demonstrated that the sensitization of Fe did not destroy the nanotube array structure, and the Fe-TNTs had an anatase phase composed of cubic-like particles at higher deposition voltages. The UV–Vis absorption spectra of the Fe-TNTs showed a redshift of photoresponse towards visible light. Such a redshift was characterized by a decrease in bandgap energy and the photo efficiency was enhanced. The optimal photoelectrochemical performance was observed at 2.5 V deposition voltage for 10 minutes and surpassed that of pristine titania nanotube arrays. The present work demonstrates feasible modification of TiO2 with Fe as a potential photoanode in solar conversion devices. &nbsp

Comparison of Ti/Ti4O7, Ti/Ti4O7-PbO2-Ce, and Ti/Ti4O7 nanotube array anodes for electro-oxidation of p-nitrophenol and real wastewater

Three types of Magnéli phase anodes (Ti/Ti4O7, Ti/Ti4O7-PbO2-Ce, and Ti/Ti4O7 nanotube arrays (NTA)) were fabricated, characterized, and compared with other typical active and non-active anodes (i.e., BDD, Ti/Pt, Ti/RuO2-IrO2, and Ti/IrO2-Ta2O5) for electro-oxidation treatment of p-nitrophenol (PNP) solution and a real coal chemical concentrated brine in this study. Characterization results indicate a nanotube array structure of Ti/Ti4O7 NTA, and a compact coating of Ti4O7 microparticles and PbO2-Ce nanocrystals on the Ti substrate for Ti/Ti4O7 and Ti/Ti4O7-PbO2-Ce, respectively. The three anodes present relatively high oxygen evolution potentials (2.16–2.44 V vs SCE), showing good capacity of electro-generating reactive oxidative species for pollutant degradation. After 30 min of EO treatment, Ti/Ti4O7 NTA and Ti/Ti4O7 removed 89–92% of PNP, which were 10–60% higher than Ti/Pt, Ti/RuO2-IrO2, and Ti/IrO2-Ta2O5, and were almost comparable with BDD (95%). Furthermore, Ti/Ti4O7 NTA and Ti/Ti4O7 kept very efficient for mineralization of PNP solution and real coal chemical concentrated brine. For Ti/Ti4O7-PbO2-Ce, its degradation efficiency was lower than other two Magnéli phase anodes, but still competitive compared with other active anodes. Thanks to their high removal efficiencies, the three Magnéli phase anodes required relatively low energy demand for pollutant mineralization. Besides, operational parameters such as electrolyte and current density were also very significant for efficient pollutant removal. The results of this study suggest Magnéli phase electrodes as promising and cost-effective anode materials for industrial wastewater treatment, with Ti/Ti4O7 NTA and Ti/Ti4O7 being more efficient options.

ZnO-NWs/metallic glass nanotube hybrid arrays: Fabrication and material characterization

In this work, we fabricated first-ever nanohybrids ZnO nanowires (ZnO-NWs)/Metallic Nanotube Arrays (MeNTA) structure for the large-scale fabrication of highly dense laterally and vertical aligned ZnO-NWs. To prepare heterogeneous surface MeNTA by using sputter-deposition of different metallic glasses (Zr55Cu30Al10Ni5, Cu47Zr42Al7Ti4, Pd72Cu12Si16, W50Ni25B25 and Ni54B0.3Si36Cr2.7Fe7) over on contact-hole arrays created by a photoresist template with 650 nm height and various diameter (2, 10 and 20 μm). A ZnO seed layer is deposited by sputtering method on MeNTA to provide the nucleation sites to grow the nanowires inside the MeNTA. To perform the material analysis like surface morphology, crystal structural, and optical properties were characterized by using scanning electron microscopy, X-ray diffraction, Raman, XPS and photoluminescence, respectively. Our results confirm that, the nanowires having the hexagonal wurtzite structure and presenting strong UV emissions can be used in optoelectronics, sensors, piezoelectric-nanogenerator, solar cells and battery applications.

Synthesis of Anodized TiO2 Nanotube Arrays as Ion Sieve for Lithium Extraction

AbstractTitanium type lithium ion‐sieve nanotubes synthesized by the hydrothermal method were extensively explored over recent years due to its promising properties. However, on account of nanotubes′ tangled structure impeding the lithium adsorption in the interior nanotube walls, unalterable dimensions of the synthesized nanotubes, and a long period of annealing, the anodizing technique was proposed. It is shown that lithium uptake and adsorption capacity is improved because of easier mass transfer during the ion exchange process. This work focuses on a novel anodizing method for nanotube ion‐sieve synthesis. The optimum anodizing condition was discovered by altering anodizing voltage, time, and fluoride concentration to have a proper nanotube morphology and corresponding high surface area for achieving the most suitable adsorption properties. Nanotubes were grown on Ti foil in Ethylene Glycol (EG) electrolyte with different amounts of NH4F in a range of anodizing voltage (40–70 V) and time (1–4 hours). TiO2 Nanotube array morphology, dimension, and phase characterization were derived from FESEM and XRD analysis. As a result, the optimum condition discovered in this research to obtain acceptable morphology and high aspect ratio nanotubes was at 0.5 wt % NH4F, 40 V, 3 hours. Lithium titanate spinel with nanotube morphology was synthesized by chemical lithiation in the LiOH solution and then acid‐treated to obtain H4Ti5O12 adsorbent. ICP‐OES analysis revealed that the H4Ti5O12 lithium‐ion sieve with nanotube array structure obtain adsorption capacity up to 37.5 mg/g in LiOH and LiCl solutions (112 mg/L Li, pH 12), designating that the Hydrogen titanate (HTO) ion sieve could effectively extract Li+from the enriched solutions.

Construction of core-shell heterojunction regulating α-Fe2O3 layer on CeO2 nanotube arrays enables highly efficient Z-scheme photoelectrocatalysis

Designing direct Z-scheme photocatalytic systems with core-shell architecture is crucial for effective charge separation towards sustainable photocatalysis. Herein, the core-shell heterojunction photocatalyst consisting of α-Fe2O3 nanoparticle layers encapsulating CeO2 nanotube arrays (Ce@Fe) was successfully synthesized through a simple and feasible strategy. The Ce@Fe heterojunctions exhibit the enhanced solar light scattering and absorption performance from 380 nm to 490 nm. The formed direct Z-scheme band structure between CeO2 and α-Fe2O3 further promotes the efficiency of carrier separation and transfer, and the core-shell nanotube array structure provides high specific surface area for antibiotic adsorption and enhanced light scattering, significantly improving the photoelectrocatalytic activity. Impressively, the unique photoelectrode achieves the highest pollutant removal efficiency of 88.6% for photoelectrocatalytic tetracycline degradation at 1 h under full light irradiation, and affords superior stability and strong alkaline resistance, which is expected to photoelectrocatalytic degrade antibiotics with high efficiency and environmental protection in harsh environment. Furthermore, the novel photoelectrocatalytic mechanism involving transfer behaviors of charge carriers, generation of reactive species, degradation intermediate products of tetracycline can be adopted after growing α-Fe2O3 layers onto CeO2 nanotube arrays, in accordance with direct Z-scheme mechanism.

Highly Efficient Catalysts of Bimetallic Pt-Ru Nanocrystals Supported on Ordered ZrO2 Nanotube for Toluene Oxidation.

ZrO2 nanotube arrays and their supported bimetallic platinum and ruthenium (PtxRuy/ZrO2; x + y = 1 mmol %, x/y = 1:0, 0.9:0.1, 0.8:0.2, 0.7:0.3, 0.5:0.5, 0:1) nanocomposites were fabricated by employing SBA-15-OH as a hard template and an impregnation method, respectively. A controlled ordered nanotube array structure formed from the fabricated catalysts, and it showed a good performance for toluene oxidation. The specific physicochemical properties of the catalysts were examined through various analytical means. The PtxRuy/ZrO2 possessed a high surface area, and the Pt-Ru nanoparticles were dispersed uniformly on the ZrO2 nanotube surface. The Pt0.7Ru0.3/ZrO2 catalyst performed best among all of the samples, with T90% and T100% (temperatures for 90 and 100% conversion of toluene) of 140 and 160 °C, respectively, at a weight hourly space velocity of 36 000 mL/(h·g). These bimetallic catalysts exhibit excellent characteristics for toluene oxidation, such as higher turnover frequencies and lower apparent activation energy (Ea) values, which probably result from the synergistic effect of the Pt-Ru noble metals that leads to a high reducibility and oxygen adsorption capacity. The excellent activity, stability, and economics of the Pt0.7Ru0.3/ZrO2 catalyst allow for its application in toluene removal.

Effective combination of CuFeO2 with high temperature resistant Nb-doped TiO2 nanotube arrays for CO2 photoelectric reduction

Herein, we report a simple approach to synthesize CuFeO2/TNNTs photocathodes composed of high-temperature resistance n-type Nb-doped TiO2 nanotube arrays (TNNTs) and p-type CuFeO2 for CO2 reduction. TNNTs were prepared by anodic oxidation on TiNb alloy sheets and CuFeO2/TNNTs were then prepared by coating precursor liquid onto TNNTs followed by heat treatment in argon atmosphere. The microstructures of CuFeO2/TNNTs and TNNTs before and after heat treatment were investigated by SEM and TEM. The phase compositions of CuFeO2/TNNTs were studied by XRD and XPS, and the light absorption performance were tested by UV–vis diffuse reflectance spectrum. Results show that TNNTs exhibit a regular nanotube arrays structure and this structure is well remained after the calcination at 650 °C. In addition, TNNTs show similar semiconductor properties to n-type TiO2, which enables them to be integrated with p-type CuFeO2 to obtain composite photocathodes with a p-n junction. The synthesized CuFeO2/TNNTs photocathode is well crystallized because no other crystalline iron or copper compounds are included in the prepared photocathode. Furthermore, the photocathode shows high light absorption and fast carrier transport due to the appropriate band gap and p-n junction. As a result, high photoelectrocatalytic CO2 reduction performance with high selectivity to ethanol is obtained on this photocathode.

Effect of the Structure of Anodic TiO2 Nanotube Arrays on Its Photoelectrocatalytic Activity

Effect of the Structure of Anodic TiO2 Nanotube Arrays on Its Photoelectrocatalytic Activity