Hydrogenated TiO2 Research Articles

Enhancing solar-driven photoelectrocatalytic efficiency of Au nanoparticles with defect-rich hydrogenated TiO2 toward ethanol oxidation

It is significant to promote the efficiency of solar fuel cells via improving the utilization of solar in photoelectrocatalysis. In this work, hydrogenated TiO2 (H-TiO2) nanoparticles with Ti3+ and/or oxygen vacancy (VO) defects were obtained and have extended light absorption to visible light region. As a photochemical component, H-TiO2 was further coupled with Au nanoparticles to assemble photoelectrocatalyst to apply in photo-assisted electrooxidation of ethanol. Due to the existence of defects in H-TiO2, the peak current density on Au/H-TiO2 is improved by 5.4% with the assistance of light irradiation, and even up to 18.3% under simulated sunlight illumination, which is much higher than that on Au/W-TiO2 (W-TiO2 loaded Au) under the light irradiation. Meanwhile, it is demonstrated that the charge transfer is improved on Au/H-TiO2 with Vo due to the existence of Vo, improving the separation of excited electrons and holes. Density function theory (DFT) based theoretical calculations illustrate that the energy barrier of reaction intermediates on Au-TiO2 with Vo defects is lower than that without Vo, indicating that Au-TiO2 with Vo is more energetically favorable. This work highlights the possibility of using defective semiconductor nanomaterials to combine photocatalysis and electrocatalysis in solar fuel cells and to further improve the efficiency of fuel cells under solar full spectrum.

Two-dimensional ultrathin MoS2 modified hydrogenated TiO2 nanoparticles for superior photocatalytic degradation under simulated sunlight

Photocatalysis is an effective technology for degradation of organic contaminants. Herein, we firstly synthesized hydrogenated TiO2 (HT) nanoparticles by calcining P25, and on the basis of HT, two-dimensional ultrathin MoS2/HT binary composites with different component ratios (MHT-20%, MHT-30% and MHT-35%) were controlled prepared. UV–vis diffuse reflectance spectra (DRS) showed that the HT nanoparticles exhibited stronger absorption towards visible light in the range of 550–800 nm compared to P25, and the introduction of two-dimensional ultrathin MoS2 nanosheets further enhanced the visible light absorption ability of MHT composites. Under simulated sunlight irradiation, the removal test of methylene blue (MB) in the present of various photocatalysts indicated that the catalytic performance of HT sample was better than that of P25, and MHT binary composites displayed more excellent photocatalytic performance. A maximum removal efficiency of MB reached 95% within 4 h over MHT-30% photocatalyst. Moreover, the kinetic constant of MHT-30% catalyst is 5.6, 3.6 and 2.5 times as much as that of P25, MoS2 and HT, respectively. In addition, the repeated degradation study and composition analysis of MHT-30% before and after photocatalytic reaction showed that MHT-30% photocatalyst exhibited good stability, and the removal rate of MB still reached 88% in four cycles. The improved and stable photocatalytic performance of MHT-30% can be attributed to band matching and tight interface bonding between MoS2 and HT, which accelerated the electron transfer and broaden the visible-light response range.

Hydrogenated TiO2 supported Ru for selective methanation of CO in practical conditions

Selective methanation of CO (SMET) is promising for deep removal of low-concentration CO in excess H2. However, the development of suitable catalysts applied in practical conditions remains a great challenge. Here we report a general strategy to develop highly efficient SMET catalysts by using hydrogenated TiO2 (H-TiO2) as support. The H-TiO2 supported Ru catalysts can remove CO to below 10 ppm with greater than 50 % selectivity in a wide temperature range of 200−265 °C, with a good long-term stability. Detailed characterizations including operando spectroscopy and in-situ XPS combined with DFT calculation revealed that the lowered Ru valance on H-TiO2 strengthens CO adsorption on both metal surface and metal-support interface which improved CO activation and inhibited CO2 hydrogenation, respectively, leading to enhancement of both activity and selectivity.

A hybrid composite of rhenium complexes covalently grafted on reduced graphene oxide/hydrogenated TiO2 as an efficient catalyst for CO2 reduction under visible light

The photocatalytic conversion of CO2 to fuels by light is of research interest owing to its relevance to environment and energy concerns. In this work, a hybrid H-TiO2–rGO–Re(bpy)(CO)3Cl composite consisting of a rhenium 2,2′-bipyridine compound, Re(bpy)(CO)3Cl, which was covalently grafted on reduced graphene oxide (rGO) and hydrogenated TiO2 (H-TiO2) was prepared. H-TiO2–rGO–Re(bpy)(CO)3Cl demonstrated high efficiency for visible light photo-conversion of CO2 into CO in triethanolamine/N,N-dimethylformamide (V:V = 1:9) solution with total turnover numbers larger than 580. In addition, the composite showed high stability with no leveling-off tendency after four catalytic experimental runs. The experimental results indicate that the suitable assembly of the Re(bpy)(CO)3Cl, rGO, and H-TiO2 components in the H-TiO2–rGO–Re(bpy)(CO)3Cl composite is necessary for the observed high performance of the catalyst for CO2 reduction under visible light irradiation.

Facile, rapid, one-pot synthesis of hydrogenated TiO2 by using an atmospheric-pressure plasma jet submerged in solution

We report a simple method for the synthesis of hydrogenated TiO2 (H-TiO2) by submerging an atmospheric-pressure plasma jet in a titanium precursor solution. The synthesized H-TiO2 demonstrates improved visible light absorption and electrical conductivity due to a decreased work function and narrowed band gap. Our plasma system has significant benefits compared to previously reported hydrogenation methods. It offers a facile, one-pot synthesis process, rapid synthesis time, and ease of mass production. We expect the plasma system to be a promising technology for the synthesis of H-TiO2, and believe this method has potential for use in new environmental and optoelectronic applications.

Tuning the Electromagnetic Synergistic Effects for Enhanced Microwave Absorption via Magnetic Nickel Core Encapsulated in Hydrogenated Anatase TiO2 Shell

Owing to tremendous potential applications, hydrogenated TiO2 (H-TiO2) nanomaterial has been considered an important member in the field of microwave absorption. In this paper, a kind of core–shell structured microspheres (MPs) consisting of outer-shell hydrogenated anatase TiO2 (H-A-TiO2) and inner-core magnetic Ni MPs were prepared successfully using a simple method. Experimental results revealed the as-prepared hydrogenated anatase TiO2@Ni (H-A-TiO2@Ni) composite exhibited enhanced microwave absorption property, when compared to pristine anatase TiO2@Ni (A-TiO2@Ni). (1) The minimum reflection loss (RL) of the H-A-TiO2@Ni/wax composite reached −64.2 dB at a thickness of 2 mm, indicating a large absorption efficiency over 99.99%. (2) The H-A-TiO2@Ni showed an effective microwave absorption bandwidth (RL < −20 dB) in a range from 2.2 to 11 GHz. Due to the introduction of core–shell media, coating Ni microspheres with H-A-TiO2 shells not only will be beneficial for impedance matching behavior but also impr...

Rational Design of Multifunctional Fe@γ-Fe2 O3 @H-TiO2 Nanocomposites with Enhanced Magnetic and Photoconversion Effects for Wide Applications: From Photocatalysis to Imaging-Guided Photothermal Cancer Therapy.

Titanium dioxide (TiO2 ) has been widely investigated and used in many areas due to its high refractive index and ultraviolet light absorption, but the lack of absorption in the visible-near infrared (Vis-NIR) region limits its application. Herein, multifunctional Fe@γ-Fe2 O3 @H-TiO2 nanocomposites (NCs) with multilayer-structure are synthesized by one-step hydrogen reduction, which show remarkably improved magnetic and photoconversion effects as a promising generalists for photocatalysis, bioimaging, and photothermal therapy (PTT). Hydrogenation is used to turn white TiO2 in to hydrogenated TiO2 (H-TiO2 ), thus improving the absorption in the Vis-NIR region. Based on the excellent solar-driven photocatalytic activities of the H-TiO2 shell, the Fe@γ-Fe2 O3 magnetic core is introduced to make it convenient for separating and recovering the catalytic agents. More importantly, Fe@γ-Fe2 O3 @H-TiO2 NCs show enhanced photothermal conversion efficiency due to more circuit loops for electron transitions between H-TiO2 and γ-Fe2 O3 , and the electronic structures of Fe@γ-Fe2 O3 @H-TiO2 NCs are calculated using the Vienna ab initio simulation package based on the density functional theory to account for the results. The reported core-shell NCs can serve as an NIR-responsive photothermal agent for magnetic-targeted photothermal therapy and as a multimodal imaging probe for cancer including infrared photothermal imaging, magnetic resonance imaging, and photoacoustic imaging.

Enhanced charge transfer and separation of hierarchical hydrogenated TiO2 nanothorns/carbon nanofibers composites decorated by NiS quantum dots for remarkable photocatalytic H2 production activity.

Hierarchical core/shell hydrogenated TiO2 (H-TiO2) nanothorns/carbon nanofibers (CNFs) composites were produced through a solvothermal method, followed by ordinal calcination and hydrogenation treatments using the prepared carbon nanofiber as electron-transporting substrate material. The hierarchical H-TiO2/CNFs composites possess more exposed surface active sites and offer efficient charge transport paths. NiS quantum dots as excellent electron acceptors and cocatalysts were anchored on the hierarchical H-TiO2/CNFs composites by a wet chemical deposition method. The synergistic effects of the surface defects (oxygen vacancies), NiS cocatalyst, and carbon nanofibers greatly improve charge transfer and separation, increase the accessible surface area and surface donor density of the composites and also extend the photoresponse from the ultraviolet to the visible light region. By taking advantage of these features and because of its unique architecture, the optimal NiS quantum dots-decorated H-TiO2/CNFs composite exhibited a remarkable solar-driven hydrogen generation rate (75.92 μmol h-1, 30 mg-1) in the absence of a Pt cocatalyst under AM 1.5 irradiation, which is about 12.3 times that of TiO2/CNFs nanostructures.

Coupling copper and hydrogenated TiO2 to bare TiO2 structures for improved photocatalytic performance

AbstractCoupling of metals and hydrogenated TiO2 (HT) to bare TiO2 may improve synergistically the photocatalytic activity of TiO2 for pollutant decomposition. Herein, we address this issue by investigating the photocatalytic performances of Cu‐loaded HT (CuHT)/bare TiO2 (CuHTT) heterojunction nanocomposites for the degradation of harmful n‐butanol under simulated solar light illumination. CuHTT with a CuHT‐to‐TiO2 composition ratio of 0.1 showed a photocatalytic efficiency exceeding those of four reference photocatalysts, exhibiting the advantages of improved visible light absorption efficiency, charge carrier separation, and adsorption capacity. Increasing the CuHT‐to‐TiO2 ratio from 0.01 to 0.1 improved the photocatalytic efficiency of CuHTT, whereas a further increase to 0.9 resulted in a decreased photocatalytic efficiency. Moreover, the photocatalytic efficiency improved as relative humidity increased from 20% to 70%, decreasing upon its further increase to 95%. The efficiencies of n‐butanol to CO2 conversion over CuHTT were lower than the corresponding decomposition efficiencies. Incompletely oxidized CO and three organic vapors (butanal, propanal, and 1‐propanol) were determined as major intermediates. A possible mechanism for CuHTT‐catalyzed photodegradation under simulated solar illumination was proposed.

Fabrication of H‐TiO2/CdS/Cu2‐xS Ternary Heterostructures for Enhanced Photocatalytic Hydrogen Production

AbstractSolar‐driven photocatalytic water splitting is a promising technology to produce H2 energy. Herein, we demonstrate the fabrication of a ternary catalyst, H‐TiO2/CdS/Cu2‐xS, by chemical bath deposition and ion exchange for efficient photocatalytic water splitting, based on hydrogenated TiO2 (H‐TiO2) with roughened surface and hollow structures. The as‐prepared H‐TiO2/CdS/Cu2‐xS ternary structure can make use of the full solar spectrum and have a better response to the near infrared region. The tuned bandgap alignments in this ternary heterostructure enable efficient separation of photogenerated electrons and holes, leading to a hydrogen production rate as high as 261.54 μmol⋅g−1⋅h−1 without noble metal as co‐catalyst. Meanwhile, a photocatalytic hydrogen production rate of 210.63 μmol⋅g−1⋅h−1 can be maintained after five cycles. We believe this fabricated noble metal‐free ternary heterostructure catalyst has a great potential in solar energy conversion with improved solar energy absorption and efficient electron‐hole separation.

Nature of Conduction Band Tailing in Hydrogenated Titanium Dioxide for Photocatalytic Hydrogen Evolution

AbstractThe involvement of oxygen vacancies in the electronic and structural properties and photocatalytic activity of hydrogenated TiO2 (H‐TiO2) for water splitting are currently under debate. Herein, the process for the formation of oxygen vacancies in H‐TiO2 is illustrated for the first time to verify the role of these vacancies on the surface and in the bulk of H‐TiO2 by using surface‐sensitive soft X‐ray techniques and bulk‐information‐included hard X‐ray techniques for the O K‐edges and Ti K‐edges, respectively. We find that oxygen vacancies on the surface and in the bulk contribute differently to tailing of the conduction band of H‐TiO2. By controlling the degree of hydrogenation to restrict tailing of the conduction band to just above the H+/H2 redox potential, the most favorable disordered structure for photocatalytic H2 evolution is developed. This work promotes a better understanding of the possible negative consequence of hydrogenated semiconductors in H2 evolution apart from the positive effect on visible‐light response.

Instability of hydrogenated TiO2.

Hydrogenated TiO2 (H-TiO2) is touted as a viable visible light photocatalyst. We report a systematic study on the thermal stability of H-implanted TiO2 using nuclear reaction analysis (NRA), Rutherford backscattering spectrometry, ultraviolet photoelectron spectroscopy, and X-ray photoelectron spectroscopy. Protons (40 keV) implanted at a ∼2 atom % level within a ∼120 nm wide profile of rutile TiO2(110) were situated ∼300 nm below the surface. NRA revealed that this H-profile broadened toward the surface after annealing at 373 K, dissipated out of the crystal into vacuum at 473 K, and was absent within the beam sampling depth (∼800 nm) at 523 K. Photoemission showed that the surface was reduced in concert with these changes. Similar anneals had no effect on pristine TiO2(110). The facile bulk diffusivity of H in rutile at low temperatures, as well as its interfacial activity toward reduction, significantly limits the utilization of H-TiO2 as a photocatalyst.

Covalently Coupled Ultrafine H-TiO2 Nanocrystals/Nitrogen-Doped Graphene Hybrid Materials for High-Performance Supercapacitor.

Hydrogenated TiO2 (H-TiO2) are considered one of the most promising materials for supercapacitors given its low-cost, high conductivity, and enhanced electrochemical activity. However, the electrochemical performances of H-TiO2 due to lacking suitable structures is unsatisfactory, and thus how to design energetic H-TiO2-based electrode architectures still remains a great challenge. Herein, covalently coupled ultrafine H-TiO2 nanocrystals/nitrogen-doped graphene (H-TiO2/NG) hybrid materials were developed through a simple hydrothermal route followed by hydrogenation. Within this architecture, the strong interaction between H-TiO2 nanocrystals and NG sheets via covalent chemical bonding affords high structural stability inhibiting the aggregation of H-TiO2 nanocrystals. Meanwhile, the NG matrices function as an electrical highway and a mechanical backbone so that most of well-dispersed ultrafine H-TiO2 nanocrystals are electrochemically active but stable. As a result, the optimized H-TiO2/NG (H-TiO2/NG-B) exhibited high reversible specific capacity of 385.2 F g(-1) at 1 A g(-1), enhanced rate performance of 320.1 F g(-1) at a high current density of 10 A g(-1), and excellent cycling stability with 98.8% capacity retention.

Hydrogenated TiO2 nanobelts as highly efficient photocatalytic organic dye degradation and hydrogen evolution photocatalyst

TiO2 nanobelts have gained increasing interest because of its outstanding properties and promising applications in a wide range of fields. Here we report the facile synthesis of hydrogenated TiO2 (H-TiO2) nanobelts, which exhibit excellent UV and visible photocatalytic decomposing of methyl orange (MO) and water splitting for hydrogen production. The improved photocatalytic property can be attributed to the Ti3+ ions and oxygen vacancies in TiO2 nanobelts created by hydrogenation. Ti3+ ions and oxygen vacancies can enhance visible light absorption, promote charge carrier trapping, and hinder the photogenerated electron–hole recombination. This work offers a simple strategy for the fabrication of a wide solar spectrum of active photocatalysts, which possesses significant potential for more efficient photodegradation, photocatalytic water splitting, and enhanced solar cells using sunlight as light source.

Formation of Highly Conductive Boron-Doped Diamond on TiO2 Nanotubes Composite for Supercapacitor or Energy Storage Devices

In the present paper, we report the phenomena of the formation of the novel composite nanostructures based on TiO2 nanotubes (NTs) over-grown by thin boron-doped diamond (BDD) film produced in Microwave Plasma Enhanced Chemical Vapor Deposition (PE MWCVD). The TiO2 nanotube array overgrown by boron-doped diamond immersed in 0.1 M NaNO3 can deliver high specific capacitance of 7.46 mF cm−2. The composite electrodes were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The depth-resolved investigations reveal that the primary anatase structure of TiO2 NTs was partially transformed into Ti2O3 and non-stoichiometric TiC fractions. The explanation for this effect is the decomposing of TiO2 NTs in the presence of activated hydrogen and carbon in the plasma leading to enhanced dehydration of NTs and carbon bonding originating from dissociated methane. This phenomena description fits also to processes demonstrated at hydrogenated TiO2 (H-TiO2) nanotube arrays used as electrode material for supercapacitors. Nevertheless, the increase of electrochemical performance can be attributed to several reasons: (1) the unique morphology of titania nanotubes and columnar BDD with intergrain defects and valley increasing specific area of electrode and (2) presence of TiC and Ti2O3 fractions introducing additional capacitance.

Highly Enhanced Photoactivity of Anatase TiO2Nanocrystals by Controlled Hydrogenation-Induced Surface Defects

Anatase TiO2 nanocrystals (aTiO2) of a uniform size have been synthesized and were subject to a successive hydrogenation under a H2 gas flow at elevated temperatures (500–700 °C). We found that the concentration of Ti3+ defects, such as Ti3+ interstitials and oxygen vacancies, and their distribution between surface and bulk varied significantly, depending on the hydrogenation temperature and time. Such changes in defects were found to be critical in enhancing the photoactivity of the hydrogenated TiO2 (H-aTiO2) by an order of magnitude. In our case, H-aTiO2 nanocrystals hydrogenated at 600 °C for longer than 10 h showed 10 times higher photoactivity than aTiO2, which was explained from a high surface-to-bulk defect ratio and a nonuniform distribution of defects between bulk and surface due to a preferential diffusion of bulk defects to the surface. Our study showed that a kinetically controlled hydrogenation condition could be used not only to control the surface/bulk defects but also to enhance the photoactivity of oxide nanocrystals.

Catalytic oxidation of formaldehyde on surface of H[sbnd]TiO2/H[sbnd]C[sbnd]TiO2 without light illumination at room temperature

A modified TiO2 was prepared by short-time annealing in low concentration of hydrogen gas at low temperature and ordinary pressure. As a result, the hydrogenated TiO2 (HTiO2) and hydrogenated carbon-doped TiO2 (HCTiO2) could decompose gaseous formaldehyde without light irradiation at room temperature. Compared with pure TiO2, the HTiO2 and HCTiO2 were allowed to introduce more oxygen vacancies and surface hydroxyl groups, which had crucial contribution to catalytic oxidation of gaseous formaldehyde in the dark. Moreover, the existence of oxygen vacancies and surface hydroxyl groups were confirmed by XPS and EPR. Oxygen vacancies could efficiently govern O2 adsorption by trapping O2 molecules on defect sites and producing active oxygen species. The surface hydroxyl groups could facilitate the adsorption of O2 molecules and remove carbonate species which could block the catalytic active sites. Based on these results, a novel mechanism of gaseous formaldehyde decomposed by hydrogenated TiO2 in the dark was proposed.