Search

Chiral metal halide perovskites with intrinsic asymmetric structures have drawn increased research interest for the application of second-order nonlinear optics (NLO). However, designing chiral perovskites with the features of a large NLO coefficient, high laser-induced damage thresholds (LDT), and environmental friendliness remains a major challenge. Herein, we have synthesized two chiral hybrid bismuth halides: (R/S-MBA)

The electrochemical oxygen reduction reaction (ORR) provides a green route for decentralized H2 O2 synthesis, where a structure-selectivity relationship is pivotal for the control of a highly selective and active two-electron pathway. Here, we report the fabrication of a boron and nitrogen co-doped turbostratic carbon catalyst with tunable B-N-C configurations (CNB-ZIL) by the assistance of a zwitterionic liquid (ZIL) for electrochemical hydrogen peroxide production. Combined spectroscopic analysis reveals a fine tailored B-N moiety in CNB-ZIL, where interfacial B-N species in a homogeneous distribution tend to segregate into hexagonal boron nitride domains at higher pyrolysis temperatures. Based on the experimental observations, a correlation between the interfacial B-N moieties and HO2 - selectivity is established. The CNB-ZIL electrocatalysts with optimal interfacial B-N moieties exhibit a high HO2 - selectivity with small overpotentials in alkaline media, giving a HO2 - yield of ≈1787 mmol gcatalyst -1 h-1 at -1.4 V in a flow-cell reactor. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:61 issue:37 ispartof: location:Germany status: published

Bismuth vanadate (BiVO₄) is an efficient photocatalyst or photoanode in water oxidation. However, the product selectivity in water oxidation over the most exposed clean and defective (001) and (101) facets is not clear. In this work, we investigated the water oxidation reaction on clean and oxygen deficient (001) and (101) facets and on Mo/W-doped facets using density functional theory. The pure (001) facet, we found, promotes OH radical formation. In the presence of oxygen vacancies, the O₂ evolution is preferred on the (101) facet with an overpotential of 0.52 V. On doping with Mo/W, the H₂O₂ evolution is preferred on the (101) facet with the overpotential of about 0.40 V; while on the (001) facet, the O₂ evolution is preferred with the overpotential of about 0.5 V. We also found that, on the (101) facet, there is a strong charge transfer from Bi atoms to the intermediates of water oxidation; but on the (001) facet, there is not. Our calculations could guide the design of the photocatalyst toward specific products of the water oxidation reaction, such as an OH radical, H₂O₂, or O₂. Moreover, the results show that the preferred sorption on the (101) facet may be a reason for the photoinduced charge separation between (101) and (001) facets of BiVO₄.

Three dimensional microporous zeolites have attracted much attention in catalysis because of their large BET surface area and abundant pores. Herein, Ti-MCM-41 zeolites with different molar ratio of Si/Ti were synthesized, and the surface acidity and active sites were adjusted by the modification of basic-earth metal oxides, and noble metal nanoparticles. The photocatalytic activity and selectivity were evaluated by the reduction of CO2 to CH4 and CO. The results indicated that the efficiency and selectivity of CO2 photoreduction to CH4 of Ti-MCM-41 zeolites were 93 ppm g−1 h−1 and 29% in the ratio Si/Ti = 10 under keeping the zeolite structure, and which is much higher than that of P25 with the value of 24 ppm g−1 h−1 and 23%. When the surface of Ti-MCM-41 zeolites was modified by different basic-earth metal oxides, the photo-reduction activity of CO2 to CH4 increased about 1.5 times with MgO modification, and the selectivity of CO2 to CH4 improved to 42%. Moreover, the photoactivity and selectivity enhanced to 8835 ppm g−1 h−1 and 93% when the surface was further decorated by Pt nanoparticles, while the selectivity of CO2 to CO reached 94% when Pd was loaded. Our work reveal reasonably that adjusting the acidity and active site of the microporous zeolites is a highly efficient way to improve the photocatalytic efficiency of CO2 reduction.

SrTiO3 (STO) is a widely used photocatalyst for water splitting, which has no photoactivity without a cocatalyst. The reason for this unclear. Here, we performed an oxygen evolution reaction (OER) ...

Developing photocatalysts with a high-efficiency charge separation remains a challenge in the solar hydrogen production. Herein, we devised and prepared a unique 2D/2D heterojunction of CuInS2/ZnIn2S4 nanosheets for solar hydrogen evolution. Structural characterizations reveal that the CuInS2/ZnIn2S4 2D/2D heterojunction with lattice match consists of the thin thickness of nanosheets and has a large interface contact area, boosting charges transfer and separation. Benefiting from the favorable 2D/2D heterojunction structure, the CuInS2/ZnIn2S4 2D/2D heterojunction photocatalyst with 5 wt % CuInS2 yields the highest H2 evolution rate of 3430.2 μmol·g–1·h–1. In addition, the apparent quantum efficiency of 5%CuInS2/ZnIn2S4 2D/2D heterojunction reaches 12.4% at 420 nm, which is high among the ZnIn2S4-based 2D/2D heterojunctions. The enhanced photocatalytic H2 evolution comes from the boosting charge separation. This work demonstrates that a 2D/2D heterojunction provides a potential way for significantly impro...

The reasons for the difference of visible light activity between the direct contact g-C3N4/TiO2 Z-scheme composites obtained by one-step or two-step calcination process were investigated in detail by XRD, TEM, XPS, Raman and ESR technologies. TEM results showed that only g-C3N4 obtained by two-step calcination (denoted as CN-TSC) presented the porous structure which was in favor of the light absorption. XPS analysis indicated that interstitial doped N species formed in one-step calcination composite (denoted as CT-OSC) while substitutional N would appear in two-step calcination composite (denoted as CT-TSC). Nevertheless, interstitial N located at the higher position in the band gap of TiO2 and usually acted as the strong capture center of holes which was unfavorable to charge transfer. ESR and Raman results indicated that CT-TSC with some concentration of surface Vo and lower concentration of bulk Vo had excellent charge separation efficiency, according to the surface-enhanced Raman scattering (SERS) results of photo-induced charge-transfer (PICT) enhancement mechanism. And as a result, the visible-light activity for propylene oxidation of CT-TSC was twice higher than that of CT-OSC.

Amyotrophic lateral sclerosis and several other neurodegenerative diseases are associated with brain deposits of amyloid-like aggregates formed by the C-terminal fragments of TDP-43 that contain the low complexity domain of the protein. Here, we report the cryo-EM structure of amyloid formed from the entire TDP-43 low complexity domain in vitro at pH 4. This structure reveals single protofilament fibrils containing a large (139-residue), tightly packed core. While the C-terminal part of this core region is largely planar and characterized by a small proportion of hydrophobic amino acids, the N-terminal region contains numerous hydrophobic residues and has a non-planar backbone conformation, resulting in rugged surfaces of fibril ends. The structural features found in these fibrils differ from those previously found for fibrils generated from short protein fragments. The present atomic model for TDP-43 LCD fibrils provides insight into potential structural perturbations caused by phosphorylation and disease-related mutations., Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) patients have brain deposits with amyloid-like aggregates from large C-terminal fragments of the transactive response DNA-binding protein of 43 kDa (TDP-43). Here, the authors present the cryo-EM structure of amyloid fibrils generated from the complete C-terminal TDP-43 low complexity domain and they discuss the effects of disease-causing mutations and phosphorylation of specific Ser residues.

Efficient adsorption and utilization of carbon dioxide play an important role in mitigating the greenhouse effect and developing clean energy. Surface functionalization of photocatalyst is an efficient method to promote the adsorption of CO2 and convert it into hydrocarbon fuels. In this work, tetraethylenepentamine (TEPA) is used to functionalize Ti-MCM-41 molecular sieve photocatalyst to enhance the adsorption and activation of CO2. Ti-MCM-41 molecular sieve was modified without any precious metal additives. When the content of TEPA was 1%, the yield of CH4 was 232 ppm g−1 h−1. Furthermore, the results indicate that high impregnation amount of TEPA causes strong and higher adsorption of CO2 but inefficient for its conversion. This is probably due to the blockage of the channel when the impregnation amount of TEPA exceeds the threshold value, which hinders the further conversion of CO2 molecules. Functionalization Ti-MCM-41 zeolite photocatalyst with amino group is the prime reason for its excellent CO2 adsorption followed by activation capacity. In the future, this proposed composite might come up as a perspective photocatalyst in the field of photocatalysis for the purpose of environment remediation.

A new amphiphilic polymer was synthesized by allowing polyethylenimine to react with benzyl bromide, and it was used as an emulsifier for the viscosity reduction of Shengli extra heavy crude oil. T...

On the basis of density functional theory calculations and experimental results, we propose a spin-flip effect in a novel single-electron-trapped oxygen vacancy (SETOV; Vo ) and Fe co-doped TiO2 photocatalyst which improves significantly the propylene photo-oxidation under visible light illumination through the two spin channels photo-absorption and one spin channel recombination congestion. The presence of SETOV can make strongly localized Fe 3d states within the band gap get more delocalized, which not only increases the carrier mobility but also has an effect on restraining carrier recombination, thus resulting in the remarkably improved photocatalytic activity. Here the proposed photocatalytic process referring to spin-flip effect might afford a way for us about how to design a material owning the expected photoactivity in terms of spin selection rules about interband transition, opening the way to ground breaking applications in energy conversion.

Neutral oxygen vacancies (Ovʼs) in semiconductor oxides give rise to excess electrons that have the potential to affect the binding of adsorbates to the surface through surface-to-adsorbate charge transfer, and, as a result, to alter the overpotential (OP) of reactions on oxygen-deficient materials compared to stoichiometric materials. We report a systematic computational investigation of the effects of Ovʼs on the oxygen evolution reaction (OER) overpotential for β-Ga2O3, a d10 semiconductor that has been shown to exhibit high activity for water splitting. We investigated 18 β-Ga2O3 surfaces/slabs, with and without Ovʼs and observed a clear dependence of OER activity on Ovʼs. A general finding emerged that the excess electrons associated with Ovʼs are found to participate in charge transfer to OER intermediates, making their bonds to the surface more ionic and stronger, depending on the amount of charge transfer. The OER reaction step free energies are significantly affected and the ensuing overpotential...

An oxygen-vacancy-rich Z-scheme g-C3N4/Pd/TiO2 ternary nanocomposite was fabricated using nanotubular titanic acid as precursors via a simple photo-deposition of Pd nanoparticles and calcination process. The prepared nanocomposites were investigated by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-visible diffuse reflectance spectroscopy, respectively. For g-C3N4/TiO2 binary nanocomposites, at the optimal content of g-C3N4 (2%), the apparent photocatalytic activity of 2%g-C3N4/TiO2 was 9 times higher than that of pure TiO2 under visible-light illumination. After deposition of Pd (1 wt%) at the contact interface between g-C3N4 and TiO2, the 2%g-C3N4/Pd/TiO2 ternary nanocomposites demonstrated the highest visible-light-driven photocatalytic activity for the degradation of gaseous propylene, which was 16- and 2-fold higher activities than pure TiO2 and 2%g-C3N4/TiO2, respectively. The mechanism for the enhanced photocatalytic performance of the g-C3N4/Pd/TiO2 photo-catalyst is proposed to be based on the efficient separation of photo-generated electron-hole pairs through Z-scheme system, in which uniform dispersity of Pd nanoparticles at contact interface between g-C3N4 and TiO2 and oxygen vacancies promote charge separation.

We report first principles and mesoscale kinetic simulations of intrinsic electron and hole transport in stoichiometric monoclinic BiVO4 (BVO). A main finding is that hole transport is bimodal: there are fast hole hops within VO4 tetrahedra that are not ‘transport-efficient’ and slower hole hops across VO4 tetrahedra that are ‘transport-efficient’. This bimodality in hole transport may explain the slow transport/high recombination characteristics of BVO. In this work, polaron hops were described via the two-state Marcus/Holstein model of VV–VIV and OI–OII interchanges for electron and hole polarons respectively. The relevant parameters in the theory were obtained using the density functional theory DFT+U method. Hopping activation energies were combined with Einstein diffusion theory to yield mobility as well as with kinetic Monte Carlo (KMC) modeling. All unique nearest neighbor electron and hole hopping processes were characterized. For V-to-V hops of electron polarons, we obtained activation energies of ∼0.37 eV that compare well with the experimental activation energy of ∼0.30 eV for drift mobility. Electron polarons remain localized on single sites along the hopping pathways before hopping via tunneling, suggestive of small non-adiabatic coupling and a diabatic character consistent with V-to-V electron transfer through space (no bridge linkers). These simulations yield a small electron transport anisotropy, with transport in the (a,b) plane being faster than along the c direction by a factor of ∼2. For hole polarons our calculations support the character of small polarons localized on O atoms as well. Some nearest neighbor hole hops have a diabatic character, while other nearest neighbor hops are adiabatic and phonon-assisted with an Arrhenius thermal dependence. Hops through O–V–O bridges and through space have low activation barriers (∼0.17 eV and ∼0.25 eV) while hops through O–Bi–O bridges have higher activation barriers (∼0.37 eV and higher). The mobility is gated by the slower transport across VO4 tetrahedra through O–Bi–O bridges owing to the underlying BVO lattice network. Hole mobility is determined to be about one order of magnitude larger than electron mobility consistent with THz spectroscopy measurements. This work sets the foundation to address facet selectivity of charge carriers in shape and size-tailored crystals.

The surface and bulk oxygen vacancy have a prominent effect on the photocatalytic performance of TiO 2 . In this study, TiO 2 possessing different types and concentration of oxygen vacancies were prepared by annealing nanotube titanic acid (NTA) at various temperatures in air or vacuum atmosphere. TiO 2 with the unitary bulk single-electron-trapped oxygen vacancies (SETOVs) formed when NTA were calcined in air. Whereas, TiO 2 with both bulk and surface oxygen vacancies were obtained when NTA were annealed in vacuum. The series of TiO 2 with different oxygen vacancies were systematically characterized by TEM, XRD, PL, XPS, ESR, and TGA. The PL and ESR analysis verified that surface oxygen vacancies and more bulk oxygen vacancies could form in vacuum atmosphere. Surface oxygen vacancies can trap electron and hinder the recombination of photo-generated charges, while bulk SETOVs act as the recombination center. The surface or bulk oxygen vacancies attributed different roles on the photo-absorbance and activity, leading that the sample of NTA-A400 displayed higher hydrogen evolution rate under UV light, whereas NTA-V400 displayed higher hydrogen evolution rate under visible light because bulk SETOVs can improve visible light absorption because sub-band formed by bulk SETOVs prompted the secondary transition of electron excited.

Molybdenum-doped akaganeite nano-rods were prepared by one step facile synthesis. The formation of akaganeite depends on the molar ratio of hexaammonium molybdate to ferric chloride hexahydrate. The nano-rods have an average particle size of ca. 30 nm and disperse uniformly. As a catalyst, the nano-rods can effectively increase the viscosity reduction rate of Shengli Oilfield extra heavy crude oil (175000 mPa s at 50 °C), especially combined with tetralin (a hydrogen donor). The results of SARA analysis, elemental analysis, and 1H NMR spectra indicate that the increase of light component caused by the denitrification and desulfuration of the catalyst plus tetralin as well as the loosening of heavy component molecules can be responsible for the viscosity reduction of the heavy oil.

Z-scheme heterostructure of nitrogen-vacancy rich g-C3N4 nanoparticles (VN-CN) confined in oxygen-vacancy rich TiO2 nanotube arrays (VO-TiO2) were fabricated to enhance CO2 photoreduction under visible light irradiation. Dual vacancies mediated VN-CN/VO-TiO2 heterostructure exhibits excellent photocatalytic CO2 reduction performance, and the CO and CH4 evolution rate are about 1.5 times and 3 times higher than that of pristine CN/TiO2, respectively. Possible reasons for the improvement of photocatalytic activity are as follows: (1) the adsorption and activation capacity of CO2 on the surface of CN/TiO2 are obviously improved due to the construction of nitrogen and oxygen dual vacancies; (2) the construction of dual vacancies are beneficial for enhancing the visible light absorption, promoting separation and transfer of photogenerated carriers due to intimate contact interface between VN-CN and VO-TiO2; (3) Z-scheme heterostructure could boost oxidation ability of VN-CN/VO-TiO2 and promote the production of more hydroxyl radical, which can react with CO2− to form HCO3−, leading to a new pathway to CO2 photoreduction compared to pristine CN/TiO2.

Exploiting an efficient and noble-metal-free cocatalyst is highly desired for photocatalytic H2 evolution from water. Here, we synthesized the MoS2-RGO/ZnO composite photocatalysts via a facile two-step solvothermal process. Through optimizing of the MoS2 and reduced graphene oxide (RGO) cocatalyst component proportion, the 0.75 wt%5G95 M/ZnO composite photocatalyst shows the highest H2 production rate of 288.4 μmol g−1 h−1 when the amount of MoS2-RGO is 0.75 wt% and the weight ratio of RGO to MoS2 is 5:95, which is about 14.1 times higher than the pure ZnO. More importantly, the ternary MoS2-RGO/ZnO composite photocatalyst exhibits much higher H2 evolution activity than the Pt loaded ZnO under the same condition. The significant improvement in the H2 evolution activity is ascribed to the positive synergetic effect between MoS2 and RGO, which acts as a hydrogen evolution cocatalyst and a robust electron transport pathway, respectively. This study suggests that MoS2-RGO can serves as an efficient and noble-metal-free cocatalyst to improve the H2 production performance of ZnO by suppressing the electron-hole pairs recombination.

Ni0@graphene nanocomposites were prepared via a solvothermal method and used as the catalysts for the viscosity reduction of extra heavy crude oil. Higher graphene content in Ni0@graphene nanocomposite has an adverse effect on its catalytic activity. The addition of tetralin and higher reaction temperature can obviously promote the catalytic activity. The catalyst accompanied by hydrogen donor can attain a viscosity reduction rate of 84.3% after the catalytic reaction under 280°C for 24 h and reduce the viscosity of crude oil from 174,219 to 27,352 mPa s (measured at 50°C).

Anatase TiO2 nanocrystals exposed with {001} facets were fabricated by solvothermal strategy in HF-C4H9OH mixed solution, using titanic acid nanobelts (TAN) as a precursor. The shape of TAN is a long flat plane with a high aspect ratio, and F− is easily adsorbed on the surface of the nanobelts, inducing a higher exposure of {001} facet of TiO2 nanoparticles during the structure reorganization. The exposed percentage of {001} facets could vary from 40 to 77% by adjusting the amount of HF. The as-prepared samples were characterized by transmission electron microscopy, N2 adsorption-desorption isotherms, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscope. The photocatalytic measurement showed that TiO2 nanocrystals with 77% {001} facets exhibited much superior photocatalytic activity for photodegradation of methyl orange, methylene blue, and rhodamine B. And what’s more, the mineralization rate of methyl orange was as high as 96% within 60 min. The photocatalytic enhancement is due to a large amount of the high energetic {001} facets exposing, the special truncated octahedral morphology and a stronger ability for dyes adsorption.

Direct contact Z-scheme g-C 3 N 4 -TiO 2 nanocomposites without an electron mediator are prepared via simple annealing the mixture of bulk g-C 3 N 4 and nanotube titanic acid (NTA) in air at 600 °C for 2 h. In the process of annealing, the bulk g-C 3 N 4 transformed to ultra-thin g-C 3 N 4 nanosheets, and NTA converted to a novel anatase TiO 2 , then the two components formed a close interaction. The XPS result reveals that some amount of nitrogen is doped into this novel-TiO 2 , and g-C 3 N 4 nanosheets exist in the composites. The results of XRD, TEM and TG indicate that the thickness of g-C 3 N 4 nanosheets is very thin. The ESR spectrum shows the existence of Ti 3+ and single-electron-trapped oxygen vacancy in the 30%g-C 3 N 4 -TiO 2 composites. In photocatalytic activity test, the 30%g-C 3 N 4 -TiO 2 nanocomposites showed an excellent photo-oxidation activity of propylene under visible light irradiation (λ≥ 420 nm), and the removal efficiency of propylene reached as high as 56.6%, and the activity kept nearly 82% after four consecutive recycles. Photoluminescence (PL) result using terephthalic acid (TA) as a probe molecule indicated that the g-C 3 N 4 -TiO 2 nanocomposites displayed a Z-sheme photocatalytic reaction system and this should be the main reason for the high photocatalytic activity. A possible photocatalytic mechanism was proposed on the basis of PL result and transient photocurrent-time curves.

Noble metal Pt nanoparticles have been considered as the most effective co-catalyst to improve the photocatalytic hydrogen production activity of TiO2. In this study, the effect of the dispersion of Pt nanoparticles on the photoactivity of TiO2 nanotubes was investigated. Compared with the samples that the co-catalyst of Pt nanoparticles agglomerated or freely dispersed, the sample with the uniformly dispersion of Pt nanoparticles showed a higher performance for photocatalytic hydrogen production. The photocatalysts were characterized systematically by TEM, BET, UV-Vis, XPS, and PL techniques, and the relationship between the structure and the photoactivity was investigated in detail. The results demonstrated that the dispersion status of Pt nanoparticles had a crucial effect on the photocatalytic activity.

Fe0/graphene nanocomposites were prepared via a thermal polymerization method and used as a catalyst to reduce the viscosity of heavy crude oil. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms and thermal analysis. Their performance on the aquathermolysis of heavy crude oil was assessed in an autoclave. Under the reaction conditions of 200°C and 24 h, the viscosity of the oil was remarkably reduced when the catalysts were added.

Catalyst is crucially important to reduce the viscosity of heavy oil during the catalytic aquathermolysis. SO4 2−-modified ZrO2-based nanoparticle catalyst is a commonly used catalyst. But less acid sites and poor hydrothermal stability limited further improving its catalytic performance and practical application. In this study, the Zr-doped silicalite zeolite catalysts with large surface area were prepared as a support matrix, and SO4 2−-modified Zr-doped silicalite zeolite (denoted as SO4 2−/Zr-silicalite-1 zeolite) was used as a solid superacid catalyst to crack the heavy oil. A reference catalyst of SO4 2−/Zr-SiO2 nanoparticles (NPs) was also prepared, which has the same composition with the SO4 2−/Zr-silicalite-1 zeolite catalyst. Compared with the SO4 2−/Zr-SiO2 NP catalyst, the amount of acid sites for the SO4 2−/Zr-silicalite-1 zeolite catalyst is significantly increased and the viscosity reduction efficiency is also enhanced by 40%. More importantly, the SO4 2−/Zr-silicalite-1 zeolite catalyst exhibits a high hydrothermal stability. After catalytic aquathermolysis, the quality of the heavy oil was also ameliorated. The heavy resins and asphaltenes reduced, while the light saturated and aromatic hydrocarbon increased. The results suggest metal element-doped silicalite zeolite catalyst is a potential useful way to solving the less acid sites and poor hydrothermal stability for the SO4 2−-modified nanoparticle catalyst.

A facile development of highly efficient MgO/TiO 2 nanotubes network (MgO/TNTs) films is described. These MgO/TNTs films have a unique one-dimensional (1D) network nanotubular structure, and the different contents of MgO existed as amorphous thin layers located on the surfaces of TiO 2 nanotubes. They exhibited excellent photoreduction efficiency of CO 2 to methane compared with the bare TiO 2 film. MgO plays a critical role in CO 2 methanation, because it has the strong adsorption ability of CO 2 and initiates the reaction by binding a CO 2 molecule, forming a magnesium carbonate species on the surface. For further improve the photocatalytic activity, Pt nanoparticles were loaded on MgO/TNTs films by the photo-reduction method. It was found that the loading of Pt notably improved the transformation efficiency of CO 2 to methane, and the highest evolution rate of methane reached 100.22 ppm/h cm 2 . The fast electron-transfer rate in MgO/TNTs film and the efficient electron–hole separation by the Pt nanoparticals were the main reasons for the enhancement of the photoreduction activity. The synergy effect of Pt nanoparticles and MgO in the nanocomposites played an important role in CO 2 photoreduction.

A facile development of highly efficient MgO/TiO 2 nanotubes network (MgO/TNTs) films is described. These MgO/TNTs films have a unique one-dimensional (1D) network nanotubular structure, and the different contents of MgO existed as amorphous thin layers located on the surfaces of TiO 2 nanotubes. They exhibited excellent photoreduction efficiency of CO 2 to methane compared with the bare TiO 2 film. MgO plays a critical role in CO 2 methanation, because it has the strong adsorption ability of CO 2 and initiates the reaction by binding a CO 2 molecule, forming a magnesium carbonate species on the surface. For further improve the photocatalytic activity, Pt nanoparticles were loaded on MgO/TNTs films by the photo-reduction method. It was found that the loading of Pt notably improved the transformation efficiency of CO 2 to methane, and the highest evolution rate of methane reached 100.22 ppm/h cm 2 . The fast electron-transfer rate in MgO/TNTs film and the efficient electron–hole separation by the Pt nanoparticals were the main reasons for the enhancement of the photoreduction activity. The synergy effect of Pt nanoparticles and MgO in the nanocomposites played an important role in CO 2 photoreduction.

Chitosan-poly(vinyl alcohol)/bentonite (CTS-PVA/BT) nanocomposites with high adsorption selectivity for Hg(II) ions were synthesized by introducing BT into the CTS-PVA polymer matrix. The structure and morphology of the nanocomposites were characterized by XRD, FTIR and SEM, etc. The BT content has great influence on microstructure of the nanocomposites. BT is in the exfoliated state in the polymer matrix when the BT content is less than 7%. Whereas some of BT tends to be intercalated by CTS and an intercalate-exfoliated nanostructure is formed as the BT content is beyond 7%. Some of BT particles disperse as tactoids in the polymeric matrix and a flocculated-intercalated nanostructure is formed with further increasing the BT content. The nanocomposites possess a mesoporous structure with a narrow size distribution and BT can effectively enhance the thermal stability. The nanocomposites have high adsorption capacity and selectivity for Hg(II) ions. The adsorption capacities for Hg(II) ions with a BT content of 0%, 10%, 30% and 50% are 460.18, 455.12, 392.19 and 360.73. mg/g, respectively, which are much higher than that for Cu(II), Cd(II) and Pb(II) ions. Interestingly, BT can improve the adsorption selectivity of the nanocomposites for Hg(II) ions. In addition, the nanocomposites can effectively remove Hg(II) of different mercuric salts with various initial concentrations and pH.

A conjugation-grafted-TiO2 nanohybrid was synthesized by chemically grafting conjugated structures on the surface of nanotube titanic acid (NTA) precursor-based TiO2 through the controlled thermal degradation of a coacervated polymer layer of polyvinyl alcohol (PVA). The interfacial interactions between the NTA precursor-based TiO2 and conjugated structures were characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Moreover, the effects of the NTA’s pretreatment temperature and the weight ratio of NTA to PVA on the photocatalytic degradation of methyl orange were also investigated. A higher NTA pretreatment temperature and a lower NTA to PVA weight ratio were found to enhance photogenerated electron–hole separation efficiency and photocatalytic activity. Moreover, the conjugation-grafted-TiO2 nanohybrid synthesized from the NTA precursor displayed a much higher visible-light photocatalytic activity than that of the sample obtained from the P25 precursor. The origin of the enhanced photocatalytic activity under visible-light irradiation is also discussed in detail.

This study reports the significant pressure effect on the photocatalytic activity of hydrogen generation over two kinds of representative semiconductor catalysts (TiSi2 and Pt/TiO2). The photothermal-catalytic hydrogen generation from water steam splitting under visible light was achieved. And the physicochemical properties of the photocatalysts were characterized by XRD and XPS techniques. Compared to the conventional liquid-solid-phase photocatalytic method, this gas-solid-phase photothermal-catalytic method for hydrogen releasing from water steam exhibited a higher apparent quantum yield (22.01%) under the high pressure.

Vulcan XC-72 carbon black for use as a catalyst support was treated in three different plasma atmospheres, H2, Ar and O2. The results showed that the microstructure and surface functional groups were significantly changed after plasma treatment. Pt/C catalysts were prepared by chemical reduction of H2PtCl6 with HCHO and those with untreated and plasma treated carbon black supports were characterized and tested for methanol electrooxidation. TEM showed that the platinum nanoparticles on H2 and Ar plasma treated carbon were uniform and well distributed. Those on untreated carbon were uniform in most regions but coalesced in others. On O2 plasma treated carbon agglomeration of the platinum nanoparticles was significant. XRD showed that the catalysts were composed of face-centered cubic Pt nanoparticles and XPS showed that they were metallic with no oxides present. Cyclic voltammetry and chronoamperometry were used to study methanol electrooxidation on the Pt/C catalysts in a solution of 0.5 M H2SO4 + 0.5 M CH3OH, and showed that the catalytic activity those using H2 and Ar plasma treated carbon was higher than for the untreated one. Catalysts supported by O2 plasma treated carbon showed no catalytic activity. The treatment atmosphere of carbon therefore had a large effect on the catalyst performance, with the H2 plasma being the best.

Lanthanum- and nitrogen-codoped TiO2 photocatalysts was synthesized using orthorhombic nanotubes titanic acid as the precursor by a simple impregnation and subsequent calcination method. The morphology, phase structure, and properties of La- and N-codoped TiO2 were well characterized by transmission electron microscopy, X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, and UV–Vis diffuse reflectance spectra. The La-/N-codoped TiO2 showed excellent photoactivity of propylene oxidation compared with the single-doped TiO2 and La-/N-codoped P25 TiO2 nanoparticles under visible light irradiation. The origin of the enhancement of the visible light-responsive photocatalytic activity was discussed in detail.

A novel kind of nano-sized TiO2 (anatase) was obtained by high-temperature (400–700°C) dehydration of nanotube titanic acid (H2Ti2O4(OH)2, NTA). The high-temperature (400–700°C) dehydrated nanotube titanic acids (HD-NTAs) with a unique defect structure exhibited a p-type semiconductor behavior under visible-light irradiation ( $$\uplambda\ge420$$ nm, E photon=2.95 eV), whereas exhibited an n-type semiconductor behavior irradiated with UV light ( $$\uplambda=365$$ nm, E photon=3.40 eV).

Edges naturally exist in a single-layer graphene sample. Similarly, individual graphene layers in a multilayer graphene sample contribute their own edges. We study the Raman spectrum at the edge of a graphene layer laid on n layer graphene (nLG). We found that the D band observed from the edge of the top graphene layer exhibits an identical line shape to that of disordered (n+1)LG induced by ion-implantation. Based on the spectral features of the D and 2D bands, we identified two types of alignment configurations at the edges of mechanically-exfoliated bilayer and trilayer graphenes, whose edges are well-aligned from their optical images., 9 pages, 2 figures

Mesoporous CeOx/TiO2nanoparticles have been successfully synthesized using titanate nanotubes as precursor through the hydrothermal-calcination method. The as-prepared materials were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), UV-vis diffuse reflectance spectra and nitrogen adsorption-desorption isotherm analysis. All the obtained CeOx/TiO2materials exhibit anatase phase. Ce element existed in two valance states of Ce3+and Ce4+. Introduction of Ce species can effectively extend the spectral response from UV to visible light region. N2adsorption-desorption analysis revealed that all the samples belong to mesoporous structure and have large BET surface area compared with P25. The CeOx/TiO2nanoparticles showed excellent photocatalytic activity in the degradation of MB under visible light irradiation.

Using the citric acid complexing method, perovskite-like mixed oxides La 2 NiO 4 were prepared. Before and after reduction, its structure was characterized by means of X-ray diffraction and XPS. Due to the formation of La 2 NiO 4 , Ni 2+ and La 3+ ions were evenly distributed. Nickel exists chiefly as Ni 0 after reduction and the size of Ni particles was estimated to be ca. 28 nm. After reduction of La 2 NiO 4 oxide, the rare earth oxide, La 2 O 3 , prevents Ni particles from agglomerating and promotes the dispersion of nano-scale Ni particles, which is one of the key factors for carbon nanotube growth. The carbon nanotubes from the catalytic decomposition of CH 4 were obtained using La 2 NiO 4 oxides as the catalyst precursor. The morphology of the carbon nanotubes obtained has been examined by transmission electron microscopy and scanning electron microscopy. High resolution transmission electron microscopy images and Raman spectra of carbon nanotubes show they are multi-walled nanotubes of good quality.

Orthorhombic titanic acid nanotubes (TAN) have large BET surface area and small-diameter one-dimensional nanotubular morphology, so they can work as a good supporter and a precursor of TiO2. However, in our former research, we found that calcination of TAN to anatase TiO2 would destroy the nanotubular structure and decrease the BET surface area sharply. In this work, we utilized the pillar effect of the foreign nanoparticles (La2O3) to keep the nanotubular morphology of TiO2, and obtained the anatase TiO2 nanotubes with large BET surface area. For improving the photocatalytic activity, Pd nanoparticles were loaded as the electron traps on the surface of La-doped TiO2 by photo-deposition method. The photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, diffuse reflectance spectra, and N2 adsorption–desorption isotherms measurement. Their photocatalytic activities were evaluated by the removal of propylene under visible light irradiation (λ ≥ 420 nm). The results showed that the photocatalytic activity of Pd-loaded La-doped TiO2 nanotubes improved effectively compared with that of La-doped TiO2 and pure TiO2.

Nanotube titanic acid/graphene (NTA/Gr) composites were prepared by an easy hydrothermal treatment of graphene oxide (GO) and NTA in a mixed solvent of ethanol–water. As-prepared NTA/Gr composites and GO were characterized by means of Fourier transform infrared spectrometry, X-ray diffraction, diffuse-reflection spectrometry, thermal analysis, and transmission electron microscopy. Besides, the photocatalytic activities of as-prepared NTA/Gr composites were evaluated by monitoring the degradation of methyl orange (MO) under visible light irradiation. It has been found that extending hydrothermal reaction time (24 h instead of 3 h) leads to great changes in the morphology and crystal structure of as-prepared composites. Namely, the orthorhombic NTA (ca. 10 nm in diameter) in the composite transformed to anatase TiO2 particle (ca. 20–30 nm in diameter) while the Gr sheets (with micrometers-long wrinkles) in it transformed to a few Gr fragments (ca. 50 nm in diameter). Correspondingly, the NTA/Gr composite transformed to titanium dioxide/graphene (TiO2/Gr) composite. In the meantime, pure GO only has adsorption effect but it has no photocatalytic activity in the visible light region. Nevertheless, increasing Gr ratio results in enhanced visible light absorption capability and photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites. This demonstrates that the true visible light photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites for the degradation of MO is not as excellent as expected, and their high apparent activity is attributed to the strong adsorption of MO on the composites.

Two kinds of hollow shell structured nickel titanates (nanosphere, nanorod) were prepared by the microwave-assisted hydrothermal method using carbon material as the template. Their phase structure, morphology, and optical properties were well characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectroscopy (DRS). Comparing with the template-free NiTiO3 (NiTiO3-TF), the two kinds of hollow shell structured NiTiO3 have larger Brunauer-Emmet-Teller (BET) surface areas. Both NiTiO3 nanosphere (NiTiO3-NS) and nanorod (NiTiO3-NR) showed remarkably photocatalytic H2 evolution from the methanol aqueous solution under full-arc lamp and visible light. Additional, their photocatalytic activities were also determined by photo-degradation of methyl blue (MB), and the degradation yield reached nearly 100% within 100 min on NiTiO3-NR under visible light. Whatever in photocatalytic H2 evolution or MB degradation, their photocatalytic activities all followed the order: NiTiO3-NR > NiTiO3-NS > NiTiO3-TF. The higher photocatalytic activities of the hollow shelled NiTiO3 should be due to their larger BET surface areas and more utilization of the incident light.

Silver bromide/titanium dioxide composites were first prepared using titanic acid nanobelts (TAN) as the TiO2 source. First, TAN reacted with AgNO3 to prepare Ag-incorporated TAN by the ion-exchange method, and then AgBr/TAN was obtained after adding NaBr. Finally, AgBr/TAN was transformed to AgBr/TiO2 composites by calcination. The post-treated calcination would not only convert TAN to TiO2 (H2Ti2O4(OH)2 → 2H2O + 2TiO2), but also increase the effective contact between AgBr and TiO2, further to improve the separation of photo-generated electron-holes. The advantage of this preparation method is the small particle size (ca. 10–20 nm) and well dispersion of AgBr on the surface of TiO2, and close contact between AgBr and TiO2. The effect of the different calcination temperature on the morphology, structure, and properties of AgBr/TiO2 composites was investigated in detail. The AgBr/TiO2 composites were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), and ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS). Comparing with pure TAN, AgBr, and AgBr/P25 mixture, the AgBr/TiO2 composites exhibited enhanced photocatalytic activity in decomposition of methyl orange (MO) under visible light irradiation.

Anatase TiO2 nanotube film was prepared by calcination of the orthorhombic titanic acid nanotube at 400 °C. To expand the light absorption, AgBr nanoparticles were sensitized on TiO2 film. The AgBr–TiO2 nanotube film showed a high activity for MO photo-degradation under visible light irradiation. Moreover, the photocatalytic activity was further improved a lot after annealing of the AgBr–TiO2 nanotube film.

Titanate network films were grown in situ on a Ti foil by a fast microwave-assisted hydrothermal method. The titanate network (STN) films were formed by twisting of long one dimensional (1D) multi-walled titanate nanotubes. Compared with the traditional hydrothermal method, the applied microwaves can accelerate the reaction rate and this method can save time. To expand the light absorption capability, PbS and CdS nanocrystals were uniformly sensitized on the STN film. After sensitization, the light absorption was remarkably shifted to the long wavelength direction, while the network structures of the film were kept. The PbS-STN and CdS-STN films showed enhanced photocatalytic activities for MO degradation compared to the bare STN film and N-TiO2 film. These enhanced photocatalytic activities were possibly due to the large BET surface areas of the titanate nanotubes, more light harvesting in the channels of the surface network structure, and the high separation probability of the photo-generated electron–hole pairs. Furthermore, it is interesting that all of the STN, PbS-STN, and CdS-STN films showed the super-amphiphilicity without any light irradiation, which may be due to the roughness of the surface network structures. And this super-amphiphilicity was kept even after exposure to air for more than 6 months.

WO(3) modified titanate network film was prepared by an improved low-temperature two-step hydrothermal method. It showed a high mineralization yield (over 90%) for 2-propanol (IPA) photo-decomposition by only 2 h of visible light (lambdaor = 420 nm) irradiation. Furthermore, it exhibited quite good stability in this photocatalytic mineralization.