Bocheng Qiu

Mesoporous TiO2 Nanocrystals Grown in Situ on Graphene Aerogels for High Photocatalysis and Lithium-Ion Batteries

TiO2/graphene composites have been well studied as a solar light photocatalysts and electrode materials for lithium-ion batteries (LIBs). Recent reports have shown that ultralight 3D-graphene aerogels (GAs) can better adsorb organic pollutants and can provide multidimensional electron transport pathways, implying a significant potential application for photocatalysis and LIBs. Here, we report a simple one-step hydrothermal method toward in situ growth of ultradispersed mesoporous TiO2 nanocrystals with (001) facets on GAs. This method uses glucose as the dispersant and linker owing to its hierarchically porous structure and a high surface area. The TiO2/GAs reported here exhibit a highly recyclable photocatalytic activity for methyl orange pollutant and a high specific capacity in LIBs. The strong interaction between TiO2 and GAs, the facet characteristics, the high electrical conductivity, and the three-dimensional hierarchically porous structure of these composites results in highly active photocatalysis, a high rate capability, and stable cycling.

Facile synthesis of the Ti3+ self-doped TiO2-graphene nanosheet composites with enhanced photocatalysis

This study developed a facile approach for preparing Ti3+ self-doped TiO2-graphene photocatalyst by a one-step vacuum activation technology involved a relative lower temperature, which could be activated by the visible light owing to the synergistic effect among Ti3+ doping, some new intersurface bonds generation and graphene oxide reduction. Compared with the traditional methods, the vacuum activation involves a low temperature and low-costing, which can achieve the reduction of GO, the self doping of Ti3+ in TiO2 and the loading of TiO2 nanoparticles on GR surface at the same time. These resulting TiO2-graphene composites show the high photodegradation rate of MO, high hydrogen evolution activity and excellent IPCE in the visible light irradiation. The facile vacuum activation method can provide an effective and practical approach to improve the performance of TiO2-graphene and other metal oxides-graphene towards their practical photocatalytic applications.

Highly-dispersed Boron-doped Graphene Nanosheets Loaded with TiO2 Nanoparticles for Enhancing CO2 Photoreduction

Boron doped graphene nanosheets (B-GR) as a p-type semiconductor, provides much more edges to facilitate the loading of TiO2 nanoparticles (P25). Highly-dispersed P25/B-GR nanosheets with the size of 20-50 nm, are successfully synthesized by the vacuum activation and ultraphonic method. The nanosized morphology can decrease the local density of defects which are induced by the boron substitutional doping, and make the B-GR keeping excellent conductivity and p-type transport property. Ti-O-C bonds are formed during the mixing process, which could efficiently transfer the electrons from TiO2 to B-GR and the holes from B-GR to TiO2. The tunable bandgap of B-GR determines the large potential application of P25/B-GR in the photoreduction of CO2 and other gaseous organic pollutants.

A Brown Mesoporous TiO2‐x/MCF Composite with an Extremely High Quantum Yield of Solar Energy Photocatalysis for H2 Evolution

A brown mesoporous TiO2-x /MCF composite with a high fluorine dopant concentration (8.01 at%) is synthesized by a vacuum activation method. It exhibits an excellent solar absorption and a record-breaking quantum yield (Φ = 46%) and a high photon-hydrogen energy conversion efficiency (η = 34%,) for solar photocatalytic H2 production, which are all higher than that of the black hydrogen-doped TiO2 (Φ = 35%, η = 24%). The MCFs serve to improve the adsorption of F atoms onto the TiO2 /MCF composite surface, which after the formation of oxygen vacancies by vacuum activation, facilitate the abundant substitution of these vacancies with F atoms. The decrease of recombination sites induced by high-concentration F doping and the synergistic effect between lattice Ti(3+)-F and surface Ti(3+)-F are responsible for the enhanced lifetime of electrons, the observed excellent absorption of solar light, and the photocatalytic production of H2 for these catalysts. The as-prepared F-doped composite is an ideal solar light-driven photocatalyst with great potential for applications ranging from the remediation of environmental pollution to the harnessing of solar energy for H2 production.

Stöber-like method to synthesize ultralight, porous, stretchable Fe2O3/graphene aerogels for excellent performance in photo-Fenton reaction and electrochemical capacitors

We report three-dimensional (3D) graphene-based hybrids of Fe2O3 nanocrystals grown in situ on graphene aerogels (Fe2O3/GAs) by a Stober-like method. Compared with other reported Fe2O3/3D-graphene, Fe2O3/GAs have outstanding mechanical strength, high elasticity, ultralow mass, excellent electrical conductivity, good oil absorption capacity and a dispersion of nanoparticles. They have a 3D network structure with a high surface area of 316 m2 g−1 and physicochemical stability. 3D-GAs can inhibit the loss of Fe2+ and stabilize the conversion of Fe3+/Fe2+ in the photo-Fenton reaction. Compared with Fe2O3 and Fe2O3/2D-graphene (Fe2O3/GR), Fe2O3/GAs exhibit an ultrastable, solar-driven Fenton activity over a wide pH range of 3.5–9.0 for the first time. In addition, the highly-dispersed, nanosized Fe2O3 on the surface of the GAs makes the composite highly suitable for use in electrochemical capacitors. Although the Fe2O3/GAs only contain 18.3 wt% Fe2O3, they still yield a high and stable capacitance (151.2 F g−1) at a high discharge current density of 10 A g−1, which is better than that of Fe2O3/GR (93.6 F g−1).

Ultradispersed Cobalt Ferrite Nanoparticles Assembled in Graphene Aerogel for Continuous Photo-Fenton Reaction and Enhanced Lithium Storage Performance

The Photo-Fenton reaction is an advanced technology to eliminate organic pollutants in environmental chemistry. Moreover, the conversion rate of Fe3+/Fe2+ and utilization rate of H2O2 are significant factors in Photo-Fenton reaction. In this work, we reported three dimensional (3D) hierarchical cobalt ferrite/graphene aerogels (CoFe2O4/GAs) composites by the in situ growing CoFe2O4 crystal seeds on the graphene oxide (GO) followed by the hydrothermal process. The resulting CoFe2O4/GAs composites demonstrated 3D hierarchical pore structure with mesopores (14~18 nm), macropores (50~125 nm), and a remarkable surface area (177.8 m2 g−1). These properties endowed this hybrid with the high and recyclable Photo-Fenton activity for methyl orange pollutant degradation. More importantly, the CoFe2O4/GAs composites can keep high Photo-Fenton activity in a wide pH. Besides, the CoFe2O4/GAs composites also exhibited excellent cyclic performance and good rate capability. The 3D framework can not only effectively prevent the volume expansion and aggregation of CoFe2O4 nanoparticles during the charge/discharge processes for Lithium-ion batteries (LIBs), but also shorten lithium ions and electron diffusion length in 3D pathways. These results indicated a broaden application prospect of 3D-graphene based hybrids in wastewater treatment and energy storage.

Chiral Carbonaceous Nanotubes Modified with Titania Nanocrystals: Plasmon‐Free and Recyclable SERS Sensitivity

Chiral carbonaceous nanotubes (CNT) were successfully used in plasmon-free surface-enhanced Raman scattering (SERS) for the first time. Further modification of TiO2 nanocrystals on the chiral CNTs successfully realized the recycling of SERS substrate as chiral CNT/TiO2 hybrids. The high SERS sensitivity of methylene blue (MB) over the chiral CNT/TiO2 hybrids is ascribed to the laser-driven birefringence induced by the helical structure, which provides much more opportunities for the occurrence of Raman scattering. The TiO2 nanocrystals highly dispersed on the surface and inside the hollow cavity of chiral CNTs can completely degrade the MB under the solar light irradiation, leading to the self-cleaning of SERS substrate. The present research opens a new way for the application of chiral inorganic materials in plasmon-free SERS detection.

Facile preparation of C-modified TiO2 supported on MCF for high visible-light-driven photocatalysis

A green and facile approach is employed to prepare an efficient visible-light-driven photocatalyst by using mesocellular foams (MCF) as a matrix, glucose as a carbon-modified source and TiO2 as the catalytic active site, which is denoted as C-modified TiO2/MCF. Characterization results reveal that nano-sized TiO2 nanoparticles are loaded in the pore channels of MCF rather than being aggregated on the surface of the MCF. Furthermore, glucose selectively covers the surface of the TiO2/MCF composites during the stirring process due to the excellent adsorption capacity of MCF, and glucose then can be transformed into coke carbon through a hydrothermal process. In addition, a facile thermal treatment is adopted to enhance the visible light photocatalytic activity of the TiO2/MCF composites. It is believed that the post-thermal treatment plays a significant role in controlling the carbon diffusion from the surface to the bulk of TiO2. Compared to traditional C-TiO2 photocatalysts, the prepared C-doped catalyst exhibits stable carbon doping of TiO2, superior adsorption capacity and higher visible light photocatalytic activity owing to the special structure of the supported mesoporous catalyst. This study implies that the novel photocatalyst has good application prospects in photocatalytic water splitting, dye-sensitized solar cells and other fields.

Nitrogen‐Doped Mesoporous Carbon Encapsulated MoO2 Nanobelts as a High Capacity and Stable Host for Lithium‐ion Storage

N-doped mesoporous carbon-capped MoO2 nanobelts (designated as MoO2 @NC) were synthesized and applied to lithium-ion storage. Owing to the stable core-shell structural framework and conductive mesoporous carbon matrix, the as-prepared MoO2 @NC shows a high specific capacity of around 700 mA h g-1 at a current of 0.5 A g-1 , excellent cycling stability up to 100 cycles, and superior rate performance. The N-doped mesoporous carbon can greatly improve the conductivity and provide uninhibited conducting pathways for fast charge transfer and transport. Moreover, the core-shell structure improved the structural integrity, leading to a high stability during the cycling process. All of these merits make the MoO2 @NC to be a suitable and promising material for lithium ion battery.

TiO2/Graphene Composites with Excellent Performance in Photocatalysis

Since 1972, TiO2-based photocatalysis has attracted much attention owing to its excellent and stable UV light-driven photocatalytic activity. However, in the past few decades, most reported modifications such as impurity doping, noble metal loading, and dye sensitization on TiO2 only have a limited role in promoting its solar light activity, owing to the introduction of electron and hole recombination centers in TiO2. Until the emergence of graphene, which is as a cardiotonic to bring a new breakthrough on photocatalysis. In this chapter, we introduce the recent progress of TiO2/graphene composites application in photocatalysis. The preparation, characterization, and application of two/three-dimensional TiO2/graphene composites in photocatalysis including photodegradation of organic pollutants, water splitting, and CO2 photoreduction are the focus of this chapter. At last, we give a prospective of graphene based materials in photocatalysis especially for their industrial applications in dealing with environmental issues. Anyway, it is beyond all doubt that graphene is considered as a “catalyst” in the field of photocatalysis, which will bring new vigor to photocatalysis.