Role of hydroxylation modification on the structure and property of reduced graphene oxide/TiO2 hybrids
Graphical abstract
The structure model and enhancement mechanism of hydroxylation treatment on adsorbability and photocatalytic activity
Introduction
TiO2 has attracted considerable interests to employ in field of sensors, coating, cosmetics, supercapacitor, solar cell, and photocatalyst owing to the excellent chemical resistance and stability, high redox potential about 3.2 eV, and other unique properties [1], [2]. However, the light utilization and the carriers separation are two most concerned issues of TiO2 photocatalyst at present [3], [4]. Generally, low recombination ratio of photoexcited electron-hole pairs in vivo and vitro can contribute to a great photocatalytic activity. Series of material designs have developed to separate photoelectrons far from holes with high activity and broad light absorption, such as (1) Homogeneous heterojunctions between different crystalline facets and phases, e.g. {001}/{101} of TiO2 [5], anatase/rutile TiO2 [6], [7], [8], and H2Ti3O7/(101)TiO2 [9]. (2) Heterogeneous heterojunctions in composites, e.g. MoS2(WS2)/TiO2 [10], Bi2WO6/TiO2 [11], SiC/TiO2 [12], and C3N4/TiO2 [13]. (3) Conductive materials as electron trappers and transfer wires, including noble metals (Ag, Au, Cu and Pt) [14] and carbon materials (CNTs [15], C60 and graphene[16]). (4) Other surface modifications, such as doping and sensitization [17], [18]. (5) Mixed types [19], [20].
Among of these material designs, doping or coupling with nonmetallic elements is valid to synthesize colored TiO2 powders that have narrow band-gap and broad spectra response. For example, Fan et al. [21] reported a OH/N-doped anatase TiO2 with serial colors from white to yellow by controlling the disorder degree of TiO2. Liu et al. [22] obtained a red anatase TiO2 microspheres with a band gap of 1.94 eV for solar energy conversion via a N/B gradient-doped technique. Black TiO2 with a strong solar light utilization could be obtained by hydrogen plasma method [23], [24], [25]. In addition, carbonaceous TiO2 catalysts are gray to black color with wide light response and high conductivity [26]. Using graphene as 2D supporter can rapidly trap and transfer the photogenerated electrons of TiO2 through the high carrier mobility and large electronic storage capacity [16], [27]. Besides, the surface bond of COTi or CTi is deemed to yield a new defect energy level for wider light absorption [28].
These modifications and synthetic technologies are possible to improve the photocatalytic activity of graphene/TiO2 hybrids, but they are not adaptive in the practical application owing to its high energy consumption and high cost. Notably, surface hydroxylation should be a promising way to solve these problems because hydroxyl groups exist spontaneously in amorphous oxides before crystalline transition, such as titanium peroxide (PTC) [29], FeOOH, and H:SiOx [30]. Moreover, some theoretical simulations of nanoparticle hydroxylation in rutile [31], N-doped anatase [21], and TiO2-B [32] models have found that it is supposed to produce the dissociative adsorption with the specific surface area increased, and induce many oxygen vacancies or metallic ionic defects that benefits photoelectrons to rapidly trap and transfer [33]. Therefore, hydroxylation can become a potential way to further improve the applicability of graphene/TiO2 hybrids, which has not been reported. It is worth noting that using traditional high-temperature calcinations and hydrothermal synthesis is difficult to maintain and control the hydroxyls under high energy density.
To preserve the hydroxylation for a greater practicability, we developed a rapid energy-excitation method by using a UV/H2O2 pretreatment and microwave-assisted technique (UV-MW). Previous studies proved that UV excitation and UV-MW method can obtain efficient reduced graphene oxide (rGO)-based photocatalysts [34], [35]. In this way, high hydroxylation and the reduction of graphene oxide were realized in situ. Importantly, the effects of hydroxylation have been studied from their color, structure, morphology, performance, and working mechanism.
Section snippets
Preparation of OH-rGO/TiO2 hybrids
Graphene oxide (GO) solution was produced to a concentration of 2.0 g/L according to the modified Hummer method. The typical procedure of TiO2@OH-TiO2/rGO heterojunction hybrids (OH-rGO/TiO2) was described as follows. Briefly, 2.0 mg CTAB, 2.0 mL 0.18 g/mL PAA, and 1.0 mL concentrated HNO3 were firstly dissolved in 20 mL distilled water, while 1.0 m acetic acid and 5.8 mmol tetra-n-butyl titanate were dispersed into 15.0 mL ethanol in order. Then previous aqueous mixture and 6.0 mL sonicated GO were
XRD analysis
Fig. 1a displays that as-prepared TiO2, OH-TiO2, rGO/TiO2 and OH-rGO/TiO2 have different colors in white, yellow, black, and gray with a little yellow, respectively. The black is assigned to the reduced graphene oxide, while the yellow is attributed to the surface hydroxylation. XRD patterns in Fig. 1b describe several typical diffraction peaks in all samples at 2θ = 25.1°, 37.7°, 48.0°, 54.3° and 68.3° that refers to (101), (004), (200), (211), (204) and (116) of anatase TiO2. No special
Conclusions
Surface hydroxylation on reduced graphene oxide/TiO2 catalysts by UV pre-catalytic microwave method is promising to obtain the higher photocatalytic activity and broad spectra response. The results show that hydroxylation is available to change the powders’ color in yellow, reduce the size and degree of TiO2 crystals, and build the bond of COTi and TiOH. More importantly, this method remains many surface defects such as Ti3+, O vacancy, COTi and TiOH in hybrids, which can expand the light
Acknowledgements
This work is supported by Hunan Provincial Innovation Foundation for Postgraduate (No. CX2014B389) and Hunan Provincial Natural Science Foundation of China (No. 14JJ2077), and Open Research Fund Program of Key Laboratory of Water & Sediment Science and Water Hazard Prevention (No. 2015SS05) (Changsha University of Science & Technology). Thanks the help of Professor Jiafu Chen (University of Science and Technology of China) for the test of ESR spectra.
References (70)
- et al.
Direct Z-scheme anatase/rutile bi-phase nanocomposite TiO2 nanofiber photocatalyst with enhanced photocatalytic H2-production activity
Int. J. Hydrogen Energy
(2014) - et al.
Hierarchical (001) facet anatase/rutile TiO2 heterojunction photoanode with enhanced photoelectrocatalytic performance
Electrochim. Acta
(2013) - et al.
Synergistic photocatalytic effect of TiO2 coatings and p-type semiconductive SiC foam supports for degradation of organic contaminant
Appl. Catal. B-Environ.
(2014) - et al.
Graphitic-C3N4-hybridized TiO2 nanosheets with reactive {001} facets to enhance the UV- and visible-light photocatalytic activity
J. Hazard. Mater.
(2014) - et al.
Enhanced visible light responsive MWCNT/TiO2 core–shell nanocomposites as the potential photocatalyst for reduction of CO2 into methane
Sol. Energy Mater. Sol. C
(2014) - et al.
Surface modification of TiO2 photocatalyst for environmental applications
J. Photochem. Photobiol. C
(2013) - et al.
Promotional effect of vanadium on the selective catalytic oxidation of NH3 to N2 over Ce/V/TiO2 catalyst
Appl. Catal. B-Environ.
(2015) - et al.
Improved H2 production of Pt-TiO2/g-C3N4-MnOx composites by an efficient handling of photogenerated charge pairs
Appl. Catal. B-Environ.
(2014) - et al.
Carbonaceous nanomaterials for the enhancement of TiO2 photocatalysis
Carbon
(2011) - et al.
Synthesis of high visible light active carbon doped TiO2 photocatalyst by a facile calcination assisted solvothermal method
Appl. Catal. B-Environ.
(2013)
Monomeric peroxo titanate coordinated with cyclohexanediaminetetraacetate: towards the active oxygen species of the Ti(IV) site hosted in the titanium silicalite catalyst TS-1
Polyhedron
Fabrication of double- and triple-junction solar cells with hydrogenated amorphous silicon oxide (a-SiOx:H) top cell
Sol. Energy Mater. Sol. C
Synthesis of micro-sized hierarchical TiO2 particles of nano-scale effectiveness and their photocatalytic activities at various surface hydroxyl concentrations
Mater. Chem. Phys.
Synthesis of reduced graphene oxide/α-Bi2Mo3O12@β-Bi2O3 heterojunctions by organic electrolytes assisted UV-excited method
Chem. Eng. J.
MnOx quantum dots decorated reduced graphene oxide/TiO2 nanohybrids for enhanced activity by a UV pre-catalytic microwave method
Appl. Catal. B-Environ.
Catalytic activity of porous TiO2 obtained by sol–gel process in the degradation of phenol
J. Non Cryst. Solids
Effect of heat treatment temperature on the performance of nano-TiO2 coating in protecting 316 L stainless steel against corrosion under UV illumination and dark conditions
Surf. Coat. Tech.
Surfactant-free synthesis of water-soluble anatase nanoparticles and their application in preparation of high optic performance monoliths
J. Colloid Interface Sci.
Carbon quantum dots anchored TiO2 nanofibers: effective photocatalyst for waste water treatment
Ceram. Int.
Raman study of titania nanotube by soft chemical process
J. Mol. Struct.
Amorphous Ti species in titanium silicalite-1: structural features, chemical properties, and inactivation with sulfosalt
J. Catal.
MnO2/reduced graphene oxide composite as high-performance electrode for flexible supercapacitors
Inorg. Chem. Commun.
Sonochemical synthesis of TiO2 nanoparticles on graphene for use as photocatalyst
Ultrason. Sonochem.
Enhanced photocatalytic performance of TiO2 based on synergistic effect of Ti3+ self-doping and slow light effect
Appl. Catal. B-Environ.
ESR investigation into the effects of heat treatment and crystal structure on radicals produced over irradiated TiO2 powder
J. Photochem. Photobiol. A-Chem.
A new approach to prepare Ti3+ self-doped TiO2 via NaBH4 reduction and hydrochloric acid treatment
Appl. Catal. B-Environ.
Role of oxygen vacancy in the plasma-treated TiO2 photocatalyst with visible light activity for NO removal
J. Mol. Catal. A-Chem.
Bi2O3 quantum dots decorated anatase TiO2 nanocrystals with exposed {001} facets on graphene sheets for enhanced visible-light photocatalytic performance
Appl. Catal. B-Environ.
A comparative study of reduced graphene oxide modified TiO2, ZnO and Ta2O5 in visible light photocatalytic/photochemical oxidation of methylene blue
Appl. Catal. B-Environ.
Hypothermia-controlled Co-precipitation route to deposit well-dispersed β-Bi2O3 nanospheres on polymorphic graphene flakes
Vacuum
Superfine and closely-packed TiO2/Bi2O3 lamination on graphene nanoplates with high photocatalytic activity
Catal. Commun.
Polymer-assisted UV excitation method to synthesize reduced graphene oxide/α-Bi2Mo3O12 nanoplates with high activity
J. Environ. Chem. Eng.
Effect of inorganic ions, H2O2 and pH on the photocatalytic inactivation of Escherichia coli with silver impregnated combustion synthesized TiO2 catalyst
Appl. Catal. B-Environ.
Improved photocatalytic and antibacterial activities of three-dimensional polycrystalline anatase TiO2 photocatalysts
Appl. Catal. A-Gen.
Ultraviolet B retards growth, induces oxidative stress, and modulates DNA repair-related gene and heat shock protein gene expression in the monogonont rotifer Brachionus sp
Aquat. Toxicol.
Cited by (96)
Effects of surface groups on Fe/ZnO catalysts for CO<inf>2</inf> hydrogenation to olefin
2024, Applied Surface ScienceSelf-standing CdS/TiO<inf>2</inf> Janus nanofiberous membrane: COD removal, antibacterial activity and photocatalytic degradation of organic pollutants
2024, Journal of Environmental Chemical EngineeringStudy of the hydroxylation of the TiO<inf>2</inf> thin layer prepared by spin-coating method using FTIR analysis and DFT theory
2024, Inorganic Chemistry CommunicationsGraphene/LDHs hybrid composites synthesis and application in environmental protection
2024, Separation and Purification Technology