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Previous work showed that the copper oxide nanoparticles confined in titania nanotubes (Cu-in-TiO2NT) can effectively enhance the water–gas shift (WGS) activity. The WGS activity is directly related to the concentration of active copper species and oxygen vacancies (Ov). The addition of potassium is found to enhance WGS activity of copper catalysts to some extent. Herein, the K-promoted copper oxide (2 wt% Cu) nanoparticles confined in TiO2 nanotubes catalysts (Cu-in-K/TiO2NT) with different potassium contents were synthesized and investigated for the WGS reaction. The K-promoted catalysts exhibit the enhanced WGS activity. Especially, the Cu-in-K20/TiO2NT with the molar ratio of K/Cu = 20 displays twofold higher WGS activity compared with the Cu-in-TiO2NT. XRD, Raman, XPS, H2-TPR and in situ DRIFTS have verified that the addition of appropriate potassium can make active copper species bound with oxygen of the TiO2, leading to a partial reduction of TiO2 to TiO2-x, which is beneficial to form Cu–Ov–Ti site for the WGS reaction.

Construction of high-efficient and low-cost heterostructure photocatalyst is crucial for hydrogen production in solar driven water splitting. Herein, g-C3N4-modified TiO2 nanotubes (TNTs) with confined Pt nanoparticles were prepared via a facile two-step process. The results of structure characterizations by XRD, TEM, and XPS reveal that Pt nanoparticles with the average size of 2–3 nm are embedded in the inner cavity of the TiO2 nanotube, and amorphous g-C3N4 is attached to the outer wall of anatase TNTs. The as-prepared g-C3N4/TNTs@Pt ternary composite displays an enhanced visible light-induced absorbance capacity and improved charge carrier recombination rate than that of pure TNTs. The photocatalytic performance is evaluated by hydrogen evolution from water splitting by using methanol as sacrifice agent under solar light illumination. Compared with TNTs@Pt and g-C3N4/Pt photocatalysts, the as-prepared ternary nanocomposite exhibits the highest photocatalytic performance with a H2 evolution rate of 15.36 mmol h−1 g−1. A possible mechanism of photocatalytic H2 production over the ternary g-C3N4/TNTs@Pt composite is also proposed. This work not only provides a promising low-cost heterostructure candidate for water splitting, but also paves the way to rational design high-performance photocatalysts in solar-to-fuel conversion.

A modified confined catalyst with Pt nanoparticles on the interior and Fe2O3 on the exterior surface of TiO2 nanotubes (Pt-in/Fe2O3-TNTs) was prepared and investigated for catalyzing the oxidation of ethylene. Compared with the Pt-in/TNTs without Fe2O3 modification, the Pt-in/Fe2O3-TNTs exhibited a significantly enhanced activity, and the complete conversion temperature of ethylene decreased from 170 to 95 °C. X-ray photoelectron spectroscopy analysis indicated that the Pt nanoparticles were stabilized at higher oxidation states in the Pt-in/Fe2O3-TNT catalyst. It was proposed that the modification of Fe2O3 on the outer surface can tune the electronic state of the encapsulated Pt particles and accelerate the electrons transferred from Pt to Fe species via TiO2 nanotubes, thus improving the catalytic oxidation performance of the confined catalyst.

It is of great significance to develop water-gas shift (WGS) catalyst with high catalytic activity in low-temperature operational regime. In this paper, we have prepared Cu confined in TiO2 nanotub...

Over the past four decades, China’s extensive economic growth mode has led to substantial greenhouse gas emissions, and China has become the world’s largest emitter since 2009. In order to alleviate the dual pressures from international climate negotiations and domestic environmental degradation, the Chinese government has pronounced it will reach its emission peak before 2030. However, through analyzing 12 scenarios, we found that it will be very difficult to meet this ambitious goal under the current widely used policies. With the trial implementation of China’s carbon emission trading system (ETS), concerns arise over whether national ETS can accelerate the carbon peak process. In this paper, we propose a new proactive data envelopment analysis approach to investigate the impacts of national carbon ETS on carbon peak. Several important results are obtained. For example, we find that carbon ETS has a significant accelerating effect on carbon peak, which effect will advance the carbon peak by one to 2 years, and the corresponding peak values are reduced by 2.71–3 Gt. In addition, the setting of carbon price in the current Chinese pilot carbon market is found to be overly conservative. Last, our estimation on the carbon trading volume indicates that the ETS lacks vitality as the annual average carbon trading volume only represents approximately 4.3% of the total average carbon emissions. Based on these findings, several policy implications are suggested regarding the means by which China can more smoothly peak its carbon emissions before 2030 and implement national carbon ETS.

The core-shell nanoparticles of Au@TiO2 were synthesised via a simple and flexible hydrothermal route. The structure and properties were characterised by X-ray diffraction, transmission electron mi...

Nanocubic lithium titanate (Li4Ti5O12, N-LTO) has been synthesized by a modified solid-state reaction using H-titanate nanotubes as titanium source and lithium carbonate as lithium source. The as-prepared N-LTO was highly crystalline with size ranging from 50 nm to 200 nm. The electrochemical performance of the N-LTO was investigated and compared with commercial nanoscale lithium titanate (C-LTO). The N-LTO electrode showed an initial discharge capacity of 181.0 mAh g−1 at 0.5 C with capacity retention of 86.7% after 200 cycles. At a high rate of 10 C, the N-LTO electrode retained a high reversible capacity of 149.2 mAh g−1, considerably higher compared with the value of 117.1 mAh g−1 for C-LTO. The N-LTO electrode exhibited excellent long-term cycling stability with capacity retention of 82.6% at 5 C after 1000 cycles. A full cell of LiFePO4/N-LTO was tested, showing capacity retention of 78.7% at 1 C after 100 cycles.

A TiO2 nanotube-based nanoreactor was designed and fabricated by facile two steps synthesis: firstly, hydrothermal synthesized SrTiO3 was deposited on TiO2 nanotubes (TiO2NTs). Secondly, the Au nanoparticles (NPs) were encapsulated inside the TiO2NTs followed by vacuum-assisted impregnation. The as-synthesized composites were characterized using Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Photoluminescence spectra (PL) and Ultraviolet–visible absorption spectroscopy (UV–vis). The photocatalytic performance was evaluated by the hydrogen evolution reaction. The results revealed that the SrTiO3 modified TiO2NTs confined Au NPs (STO-TiO2NTs@Au) achieved an enhanced hydrogen evolution rate at 7200 μmol h−1 g−1, which was 2.2 times higher than that of bald TiO2NTs@Au at 3300 μmol h−1 g−1. The improved photocatalytic activity could be attributed to the synergistic effect of the electron-donating of SrTiO3 and TiO2NTs confinement. The as-designed nanoreactor structure provides an example of efficient carriers' separation photocatalyst.

The Fenton reaction is regarded as an advanced oxidation process that can efficiently remediate environmental pollutants. However, the one-time irreversible consumption of its catalysts raises the cost in practical application. Herein, we report the generation of active Fe2+ sites via photo-reduction by photogenerated electrons on a TiO2 nanotube-based catalyst (TNT(Pd)/Fe2O3) with Fe2O3 decorated on the outside wall, while the inside cavity entrapped Pd nanoparticles. Fenton catalytic investigations under visible light show that TNT(Pd)/Fe2O3 displays superior methyl orange degradation activity with 90% removal in 10 minutes. The kinetic constant is 4.3 times as the sum of the pure photocatalysis and Fenton catalytic kinetic constants. The synergistic effect between the Fenton and photocatalytic reactions is further evidenced by the photocurrent and photodegradation tests. The TNT(Pd)/Fe2O3 catalyst showed no decay in the Fenton-photocatalytic performance over three successive cycles. XPS measurements after long-term stability tests revealed no loss, but a slight increase in the number of Fe2+ species. All of these results suggest that the most active Fe2+ species in the Fenton reaction can be regenerated via the reduction by photogenerated electrons. This work addressed the challenge in catalyst regeneration in the traditional Fenton reaction via photoreduction by rational combination with a photocatalyst and the realized synergistic effect between photocatalysis and the Fenton reaction.

The dual credit policy is currently the main starting point for China to achieve the green and sustainable development of the auto market. However, the policy’s impact on future market development remains unclear. It is necessary to consider the market capacity constraints and the market competition environment. By researching the impact of the dual credit policy on the micro-decision-making of automakers and the long-term evolution of the macro-auto market, the effect of the dual credit policy on the Chinese auto industry is obtained. This paper considers the market capacity constraint, combines the competitive relationship and game payment matrix between NEV makers and CFV makers, constructs a game model of the competition density between NEVs and CFVs, simulates the development and evolution of China’s auto market size, and analyzes the effect of the quantitative parameters of the dual credit policy on the auto market. The results show that: (1) the increase in NEV makers’ sale of credits will stimulate their production incentives, and the increase in conventional fuel vehicle (CFV) makers’ cost of purchasing credits will reduce their production incentives; (2) tightened fuel consumption standards for CFVs has an enhanced stimulating effect on the increase in the market share of NEVs, which can effectively reduce the market share of CFVs; (3) the price of credits facilitates the growth of the NEV market share, but credit prices that are too high do not stimulate the growth of the NEV market share to a significant degree; (4) the increase in the proportion of credits required for NEVs and the increase in the price of credits together help to reduce the market share of CFVs and increase the market share of NEVs.

The core-shell structured Ag2CO3@TiO2 composite was fabricated through a simple precipitation method by coating amorphous TiO2 on the Ag2CO3 surface. The morphologies, structure and optical property were characterized by field emission-scanning electron microscopy 3(SEM), high resolution-transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Ultraviolet–visible spectroscopy and photoluminescence spectra. The photocatalytic activity was investigated by the degradation of rhodamine B under visible light irradiation. Results show that the activity of Ag2CO3@TiO2 photocatalyst is much higher than that of pure Ag2CO3. It was revealed that the amorphous TiO2 shell layer effectively promotes the separation rate of photogenerated electron-hole pairs to inhibit the photocorrosion of Ag2CO3. Moreover, the core-shell structural Ag2CO3@TiO2 photocatalyst showed high photostability for the degradation of rhodamine B.

In this paper, the finite element analysis software ABAQUS is used to analyze the ultimate bearing capacity of three-dimensional rectangular footing of marine structures. The deformation law and the failure mode of homogeneous seabed soil beneath the rectangular footing are analyzed in detail. According to the equivalent plastic strain of soil under rectangular footing, an allowable velocity field of homogeneous seabed soil is reasonably constructed. Based on the plastic limit analysis theory of soil mass and by using the Mohr-Coulomb yield criterion, an upper bound solution of the ultimate bearing capacity of three- dimensional rectangular footing on general homogeneous seabed soil is derived, and a correction factor of ultimate bearing capacity of three-dimensional rectangular footing is given. To verify the rationality and applicability of this theoretical solution, some numerical solutions are achieved using the general-purpose FEM analysis package ABAQUS, and comparisons are made among the derived upper bound solution, the solution of Vesic, and the solution of Salgado et al. The results indicate that the upper bound solution of the three-dimensional shallowly embedded rectangular footing proposed in this paper is accurate in calculating the bearing capacity of homogeneous seabed soil. For undrained saturated clay foundation and sandy foundation with smaller internal friction angle, this upper bound solution can evaluate the ultimate bearing capacity of rectangular footing; with the gradual increase of the internal friction angle of the soil, the ultimate bearing capacity of the proposed upper bound solution is slightly higher than that of the rectangular footing.

Fe–Mn oxide catalysts with different morphologies were synthesized by a one-pot hydrothermal method and applied to the Fischer–Tropsch synthesis reaction. Unpromoted Fe2O3 presents a spindle-like shape. The increase of the Mn/Fe atomic ratio in the catalysts from 5/100 to 10/100 and then to 20/100 causes the morphology transformation of the Fe–Mn oxides from spindles (FeMn5) to cubes (FeMn10) and then to nanoparticles (FeMn20). Although the Mn has a negative influence on the catalytic stability, the introduction of a Mn promoter in the Fe-based catalysts can effectively suppress the CH4 formation and facilitate the carbon chain growth. The FeMn5 spindle catalyst with a low Mn content exhibits a higher selectivity for C2–C4 short-chain hydrocarbons, while the FeMn10 cube catalyst with a relatively high Mn content displays a much better selectivity for C5+ long-chain hydrocarbons. This demonstrates that the amount of Mn promoter in the synthesized Fe–Mn oxide catalysts has a great influence on the distribution of hydrocarbon products.

The characteristics of China's carbon emissions marginal abatement costs are investigated in this paper according to the following three objectives: (1) A modified directional distance function-data envelopment analysis is proposed to avoid non-positive carbon emissions marginal abatement costs. (2) A decomposition method is introduced to determine what factors will effect a change in the marginal abatement cost. (3) Marginal abatement cost curves are estimated to allocate the burden of emissions reduction for each province. The empirical results show the following: (1) Marginal abatement costs vary from province to province, and the average marginal abatement cost of China is approximately 1866.61 Yuan/ton. The energy intensity, dependence on foreign trade and industrial structure can significantly influence the carbon marginal abatement cost. (2) The decomposition results reveal that the overall technology advance has a negative effect on marginal abatement costs in most provinces. (3) The total reduction costs and inequality increased with time; hence, carbon emissions reduction targets should be reached as soon as possible. Additionally, areas with medium marginal abatement costs are the primary force for energy conservation and emissions reduction. Finally, based on the conclusions, policy implications are suggested to facilitate more effective implementation of carbon emissions reduction actions in China.

The essence of carbon trading is to optimize the allocation of factor resources by using price leverage. However, the effect of the carbon trading market might be seriously affected by carbon trading price distortion (CTPD), which means the deviation of the actual trading price from the carbon marginal abatement cost (MAC). This paper proposes a novel analytical framework to evaluate the impacts of CTPD and explore corresponding correction strategies. Specifically, the impacts of CTPD are analyzed theoretically, and then CTPD in China’s carbon trading pilot markets during 2013–2017 is evaluated by the Stochastic Frontier Analysis. Last, the panel data vector autoregression model and panel data vector error correction model are used to explore correction strategies. Our analysis reveals several interesting insights. First, our results show that CTPD negatively impacts the economic benefits, environmental benefits, and policy acceptance of the carbon trading market. Second, China’s carbon trading market suffers from not only CTPD but also persistent negative price distortions in energy, labor, and capital factors, although CTPD is the most serious issue. Third, the energy price and macroeconomic environment have positive impacts on the carbon trading price. Last, a greater of any factor price distortion would lead to an increase in the carbon MAC. Based on these results, several correction strategies are recommended.

A modified confined catalyst with Pt nanoparticles on the interior and Fe2O3 on the exterior surface of TiO2 nanotubes (Pt-in/Fe2O3-TNTs) was prepared and investigated for catalyzing the oxidation of ethylene. Compared with the Pt-in/TNTs without Fe2O3 modification, the Pt-in/Fe2O3-TNTs exhibited a significantly enhanced activity, and the complete conversion temperature of ethylene decreased from 170 to 95 °C. X-ray photoelectron spectroscopy analysis indicated that the Pt nanoparticles were stabilized at higher oxidation states in the Pt-in/Fe2O3-TNT catalyst. It was proposed that the modification of Fe2O3 on the outer surface can tune the electronic state of the encapsulated Pt particles and accelerate the electrons transferred from Pt to Fe species via TiO2 nanotubes, thus improving the catalytic oxidation performance of the confined catalyst.

The Fenton reaction is regarded as an advanced oxidation process that can efficiently remediate environmental pollutants. However, the one-time irreversible consumption of its catalysts raises the cost in practical application. Herein, we report the generation of active Fe2+ sites via photo-reduction by photogenerated electrons on a TiO2 nanotube-based catalyst (TNT(Pd)/Fe2O3) with Fe2O3 decorated on the outside wall, while the inside cavity entrapped Pd nanoparticles. Fenton catalytic investigations under visible light show that TNT(Pd)/Fe2O3 displays superior methyl orange degradation activity with 90% removal in 10 minutes. The kinetic constant is 4.3 times as the sum of the pure photocatalysis and Fenton catalytic kinetic constants. The synergistic effect between the Fenton and photocatalytic reactions is further evidenced by the photocurrent and photodegradation tests. The TNT(Pd)/Fe2O3 catalyst showed no decay in the Fenton-photocatalytic performance over three successive cycles. XPS measurements after long-term stability tests revealed no loss, but a slight increase in the number of Fe2+ species. All of these results suggest that the most active Fe2+ species in the Fenton reaction can be regenerated via the reduction by photogenerated electrons. This work addressed the challenge in catalyst regeneration in the traditional Fenton reaction via photoreduction by rational combination with a photocatalyst and the realized synergistic effect between photocatalysis and the Fenton reaction.

The weakness that China's traditional credit fails to effectively limit enterprise emissions has become increasingly evident. Although the industry-oriented green credit policy has achieved certain effects on environmental performance through the differentiated resource allocation of the industries, banking financial institutions have the ambiguity in the definition of the credit object and the characteristics of profit maximization, which cannot achieve the essential purpose of green credit sustainably. Hence, we propose a new eco-innovation-oriented green credit policy. We prove theoretically that the new green credit is feasible and can be used as an exogenous driver for improving enterprises' eco-innovation. Contrasting with traditional credit, the newly proposed credit policy is an expansionary monetary policy, which has the characteristics of expanding credit lines and differential interest rates. Utilizing evolutionary game theory, we calculate the evolution stability conditions of green credit and eco-innovation. The results show that the key to green credit to maintaining sustainable development is the return on investment due to eco-innovation. Our theoretical analysis also reveals that environmental benefit-cost ratios and adjustment cost parameters of different assets are the important factors for green credit.

When a severe accident occurs in a nuclear reactor, fuel–coolant interaction (FCI) may occur and cause steam explosion. Energetic FCI or steam explosion will threaten the integrity of the containment and even cause radioactive leakage. Therefore, the research and evaluation of the morphology and development of the melt in the FCI process is very important. In recent decades, many scholars have conducted theoretical and experimental research on this phenomenon, and formed a large number of mathematical and physical models for the degradation, evolution and relocation of the melt. This study retrospects and summarizes the experimental and theoretical research on the FCI phenomenon, and describes the behavior of the melt in the entire evolution process from the melt jet to debris bed. In addition, on the basis of literature review, the models of each stage are classified according to the formation mechanisms and applicable conditions. Finally, in the present study, the future development direction is prospected on the ground of the previous research results.

Herein, titanium nitride (TN) nano cluster was synthesized through NH3 nitrification of titania nanotubes. The effect of nitrification temperature on the formation of TN was investigated by characterizations of X-ray diffractometer, Transmission electron microscopy, Diffuse reflectance UV–vis spectra, X-ray photoelectron spectroscopy, etc. The TN-900, nitrificated at 900 °C, demonstrated high hydrogen (H2) yield in visible light-induced water splitting owing to a narrow energy band gap, unique nano-cluster structure, reasonable surface area and excellent electrical conductivity, which promoted light harvesting, reactant adsorption, and photo-electron–hole separation.

A novel Pt entrapped in Bi2O3 decorated TiO2 nanotube (Pt-in/Bi2O3@TNT) composite was obtained by the assistance of vacuum impregnation and subsequent calcination. Attributed to the confinement effect, TiO2 nanotube (TNT) confined Pt nanoparticles catalyst (Pt-in/TNT) processed better ethylene (C2H4) combustion activity than Pt nanoparticles loaded on TNT catalyst (Pt-out/TNT). More distinctly, the Pt-in/Bi2O3@TNT displayed enhanced activity towards C2H4 combustion, a nearly complete depletion at 150 °C was achieved, which is 30 °C lower than that of the Pt-in/TNT. The characterizations of X-ray photoelectron spectroscopy (XPS) not only verified that the electron density destitution of Pt in Pt-in/Bi2O3@TNT is significantly enhanced due to the modulation of layered Bi2O3 on the confinement effect of TNT, but also indicated that the catalyst facilitates the forming and migrating of active oxygen species. This work presents an efficient confinement effect combined with electron modifier strategy to construct high-performance catalysts for environmental applications.

Technology advances are considered to be effective in reducing carbon emissions. However, studies show that the effect of such advances on reducing carbon emissions is not as effective as expected, owing to the existence of the rebound effect (RE). This paper proposes a new method integrating the Data Envelopment Analysis (DEA) production model and the sequential Malmquist-Luenberger (SML) index to calculate China's macro-carbon RE. An extended DEA production model is used to eliminate the impact of input scale, and the SML index is employed to avoid the phenomenon of technology regress. Results show that the carbon RE can be calculated more precisely. The new method is then applied to calculate carbon RE values from 30 Chinese provinces from 1996 to 2015, and results indicate that the carbon RE does indeed exist in China and that national average carbon RE values vary from 7.4% to 43.8%. Furthermore, both the backfire effect and the super conservation effect are evident in some provinces. Based upon the obtained results, certain policy implications are suggested to facilitate China in effectively implementing carbon emission reduction actions.

In this study, we prepared nanoparticles of the visible light-responsive photocatalyst, Bi2O3 entrapped in anatase TiO2 nanotubes (Bi2O3-in-TNTs) via a vacuum-assisted precursor-filling process followed by annealing. Owing to the unique tubular electronic structure of TiO2 nanotubes, the interior of the nanotube is in an electron-deficient state, which was confirmed by XPS spectra and H2-TPR. Electrochemical impedance studies showed that the Bi2O3-in-TNTs demonstrated a more efficient separation of photogenerated carriers than when Bi2O3 nanoparticles were deposited on the outer wall of TiO2 nanotubes (Bi2O3-out-TNTs). Due to the confinement effect of TiO2 nanotubes, which inhibits photogenerated carriers’ recombination, the Bi2O3-in-TNTs exhibited a better photocatalytic performance for the photo-degradation of methyl orange under visible light compared to Bi2O3-out-TNTs.

Exploring and developing novel semiconductor photo-catalysts for visible-light-driven water splitting are of great scientific significance to solve energy and environmental problems. Herein, Bismuth Selenide (Bi2Se3) nanosheets decorated with a thin layer of Bi2SeO2 to form Bi2Se3/Bi2SeO2 nanocomposites were successfully prepared using a conventional reflux and heating method. Fabricated Bi2Se3/Bi2SeO2 heterojunctions were characterized via X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. It has revealed that, the thickness of outer Bi2SeO2 layer can be tuned upon the annealing temperatures, which strongly influenced the performance of catalyst towards water splitting performances. Annealed at 200 °C, the Bi2Se3/Bi2SeO2 heterojunction with ∼5 nm of Bi2SeO2 layer yielded the highest hydrogen production rate of 136 μmol g−1 h−1. This enhanced photo-catalytic activity was ascribed to the synergy effect between the Bi2Se3/Bi2SeO2 layer, increased the visible light absorbance capacity, adjustment of the band gap and accelerate the electron-hole separation efficiency. The results represent a simply solution-based method towards a material with high photo-catalytic performance through the appropriate regulation of the oxidation degree of Bi2Se3 nanosheets, promising their industrial applications.

A modified confined catalyst with CeO2 on the interior and CuO on the exterior surface of TiO2 nanotubes (Ce-in-TNT-Cu-out) was prepared and investigated for the combustion of butane catalytically. Compared with the Ce-in-TNT and TNT-Cu-out, the Ce-in-TNT-Cu-out presents a higher activity for butane oxidation, with a conversion of 10% at 200°C and a conversion of 90%) at 300°C. XPS analysis indicates that more Ce(IV) and Cu(I) components exist in the Ce-in-TNT-Cu-out catalyst. It is proposed that electron transfer ability between encapsulated CeO2 and loaded CuO is significantly enhanced by the confinement effect of the TiO2 nanotubes, facilitating the formation and migration of active oxygen species in the catalyst. This result shows that modulating the electronic property of the active component can further improve the catalytic combustion performance of the confined catalysts.

The hydrothermally synthesized titanate nanotubes were first modified by silane coupling agent as a pillar support, and then calcined at 450 °C. Finally, the surface coated silica was etched by concentrated NaOH to obtain pure titanium dioxide nanotube. The nanotubes were characterized by X-ray diffraction, high-resolution scanning and transmission electron microscopy, N 2 adsorption-desorption isotherm measurements and photoluminescence spectra. The results revealed that titanium dioxide nanotubes have good tubular morphology, high anatase crystallinity and large surface area. Due to the better 1D nano-tubular morphology and higher separation efficiency of the photogenerated electron-hole pairs, titanium dioxide nanotube exhibits improved photocatalytic activity for the degradation of methyl orange.

TiO2 hierarchical microspheres assembled by nanotubes (TiO2NTMS) were synthesized via hydrothermal method, acid-washing procedure and subsequent calcination. The morphology, crystal structure and surface area of TiO2NTMS were characterized. The photocatalytic activity was evaluated by degradation of methyl orange as a model molecule under UV irradiation. Experimental results revealed that the crystallinity was improved with increasing the calcination temperature, but specific surface areas and pore volumes steadily decreased. TiO2NTMS calcined at 450°C exhibited the distinctive photocatalytic activity among the calcined catalysts, which was attributed to its good crystallization and remaining tubular structure hierarchical microspheres.

With the energy crisis and resource depletion nowadays, novel, highly performing, and cost-effective semiconductors are in urgent demand for efficiently harvesting solar energy for photoelectrochemical applications. Herein, this study presents low-cost anatase TiO2 hollow nanoparticles as prepared by a critical liquid-phase deposition (LPD) processing combined with a hydrothermal reaction and calcination processing, without involving any templates. The additional LPD processing not only makes the resulting samples more visible light responsive, but also results in hollowing the TiO2 nanoparticles (nanosheets vs. hollow nanoparticles). Importantly, commercial TiO2 powder is employed as the starting material to achieve the final synthesis of TiO2 hollow nanoparticles, making it scalable and cost-effective for production and applications. As a by-product, the fluoride, formed during the preparation process, is assumed to play a significant role in hollowing through chemically induced self-transformation and Ostwald ripening, in addition to enhancing the crystallinity. The beneficial structural evolution to the hollow nanoparticles enables the improvement of the photoelectrochemical performance through impressive inhibition of the recombination of the photoelectrons and holes, which is well evidenced by I ph and EIS (Nyquist plot), as well as by I–V curve and electron lifetime evaluations as for the assembled DSSCs with the prepared TiO2 hollow nanoparticles under simulated sunlight illumination (50 mW/cm2).

A novel carbon/silica co-decorated TiO 2 nanotubes (TNT) photocatalyst (CS@TNT) was prepared for visible light driven water splitting by a facile two-steps process of amino-propyl-triethoxy silane modification and calcination. Structure characterizations (XRD, STEM, XPS, UV–vis spectra and PL spectra) revealed that the silica and carbon dots were homogeneously dispersed on the surfaces of TNT. The introduced silica resists crystallization of TNT, and keeps the tubular morphology intact and high surface area; the co-existence of carbon dots increases the visible light absorbance capacity and promotes the electron-hole separation efficiency. The CS@TNT preserves intact tubular morphology during calcination (500 °C), and a high activity of 0.096 mmol/h is achieved, which was 1.7 times higher than that of actual catalyst made of gold nanoparticles loading on TNT.

Uniform doping is usually recognized as an efficient method for enhancing photocatalysis of TiO 2 , while non-uniform doping is generally supposed to be inefficient because of the inhomogeneous dispersion of dopants. However, in this study, we present the first example of non-uniform doping (with Au)-better enhanced photocatalysis of TiO 2 nanotubes, as compared to uniform doping, in terms of the photocatalytic organic dye degradation. The extent to which the non-uniform doping (achieved by liquid phase deposition (LPD)) can enhance photocatalysis is evaluated, along with a comparison with uniform doping. There exists an additional positive effect in the non-uniform doping system, that is, as generated interfaces between pure phase TiO 2 and Au-doped TiO 2 , in contrast to the uniform doping system leading to a positive “platinum island” effect. Such double beneficial effects contribute to the highest performance in the photocatalytic organic dye degradation for the Au-non-uniformly doped TiO 2 nanotubes as compared to other samples involved in this study. Both the “platinum island” and interfacial separation effects are helpful to isolate the photo-generated electrons and holes, resulting in enhanced photocatalytic activities.

MnO2 and carbon nanotube co-modified C3N4 (CNTs/MnO2-C3N4) ternary composite was synthesized. The prepared catalyst was investigated by X-ray diffraction, transmission electron microscopy, UV–Vis absorption spectroscopy, nitrogen sorption, X-ray spectroscopy, photoluminescence spectroscopy and transient photocurrent responses. The photocatalytic activity of the ternary catalyst was evaluated by hydrogen and oxygen evolution for visible-light-driven water splitting without the addition of sacrificial agents. Compared with MnO2/C3N4 and CNTs/C3N4 catalysts, the CNTs/MnO2-C3N4 ternary catalyst showed an enhanced visible light-induced water splitting activity with a H2 evolution rate of 122 μmol h−1. In the CNTs/MnO2-C3N4 ternary catalyst, CNT can capture the electron from C3N4 and facilitate hydrogen evolution, and MnO2 catalyzes the decomposition of hydrogen peroxide for O2 evolution, leading to the efficient separation of photogenerated electron–hole pairs, thus an enhanced water splitting performance is achieved.

Fe2O3 is supposed to be one of the most promising photoanode materials. In terms of charge collection and transfer efficiencies, one-dimensional nanostructure arrays exhibit superior performance with great application potential in different fields. In the articles, Fe2O3 nanorod arrays (Fe2O3NRA) have been fabricated on the conductive fluorine-doped tin dioxide glasses by the hydrothermal method, In2O3 with different times cycles anchored Fe2O3NRA photoelectrode was also prepared by a simple dip-coating process. The structure, morphology, crystalline and optical property of the as-prepared photoelectrode were characterized by X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, etc. The photoelectrochemical performance of the samples was investigated under visible light irradiation. A highest photocurrent density of 23 μA/cm2 at 1.23 V (versus the reversible hydrogen electrode) is obtained for the In2O3 with 4 times cycle anchored Fe2O3NRA photoelectrode in a 1 M Na2SO4 aqueous solution. The maximum applied bias photon-to-current efficiency is observed for the In2O3 with 4 times cycle anchored Fe2O3NRA photoelectrode with values 0.0033%. The results indicated that the appropriate decoration amount of In2O3 nanoparticles significantly hinders the recombination process of electron-hole pairs and improves the separation efficiency of photogenerated charge carriers of Fe2O3NRA.

With the implementation of China’s national carbon trading market, concerns arose over how many gross domestic product (GDP) losses caused by carbon reduction could be recovered by trading carbon emissions. Accordingly, we proposed a new linear programming-based three-step estimation approach to systematically investigate four critical issues in carbon emissions trading. These are how to initially allocate carbon trading permits, set the carbon trading price, determine the amount of GDP loss recoveries that could be obtained from carbon trading, and how setting emission reduction targets. Our empirical results showed the following: (I) The allocation modes based on the sovereignty criterion and the ability-to-pay criterion resulted in the lowest (2.84%) and highest (24.56%) concussion impacts on GDP, respectively. (II) The optimal range of the carbon trading price was linked closely to the carbon emission reduction target. Specifically, when the reduction target was set at 10%, the estimated optimal carbon trading price was 256.2–394.8 Yuan/ton, which is higher than the price used in the carbon trading pilot market. (III) If the emission reduction target were set at more than 10%, China could recover at least 598.62 G Yuan of economic losses through the carbon trading market. (IV) From an economic perspective, the single allocation mode, the sovereignty-criterion-based allocation mode, was superior to the mixed allocation modes. We provide several suggestions for policymakers to implementing a carbon emissions trading market in China.

Ru nanoparticles (NPs) have been successfully deposited in the inner pores of TiO2 nanotubes (TNTs), denoted as Ru-in/TNT, by vacuum assisted impregnation method for Fischer-Tropsch synthesis (FTS). The composition, morphology and electronic properties have been characterized by the XRD, TEM, N2-sorption, H2-TPR/TPD and XPS, investigating the confinement effect of TNT on the entrapped Ru NPs’ FTS performance. The Ru-in/TNT exhibits high CO conversion activity and superior deactivation-resist ability over the Ru-out/TNT (with most of Ru NPs deposited on the outer surface of TNT) and Ru/P25 (using commercial P25 powder as support) catalysts. Besides above superiority, the Ru-in/TNT facilitates the formation of long chain (C19+) products as well. The enhanced activity and selectivity can be ascribed to the confinement effect of TNT: (i) strengthen charge transfer and modulate the electronic properties of Ru species resulting in more active center site; (ii) constrain the metal sintering and metal leaching to resist deactivation during FTS; (iii) facilitate the re-adsorption of α-olefin leading to long-chain product.

The TiO2/MnTiO3, TiO2/MgTiO3 and TiO2/MnTiO3/MgTiO3 composite photoanodes were prepared by immersing the TiO2 nanosheets film into the mixed solution of titanium tetrachloride and manganese chloride (or magnesium chloride), and followed by calcination treatment. The effects of MnTiO3 and MgTiO3 treatment on the photovoltaic performances of the dye-sensitized solar cells (DSSCs) were investigated. The MnTiO3 and MgTiO3 as coating layer on the surface of TiO2 can effectively promote the dye adsorption adhered to the photoanode film. The photoelectric conversion efficiency of the DSSC based on TiO2/MnTiO3 and TiO2/MgTiO3 photoanodes increased by 25.7% and 15.5% compared with that of pure TiO2-based DSSC, respectively. Furthermore, the DSSC based on the TiO2/MnTiO3/MgTiO3 photoanode exhibited the highest conversion efficiency of 6.39%, exceeding that of pure TiO2-based DSSC by a factor of 1.4. The highest efficiency observed for the DSSC based on this hybrid structure is attributed to the enhanced dye-absorption, fast electron transfer and the energy barrier formed by MnTiO3/MgTiO3 layer, which suppresses the charge recombination and increases the photocurrent. This investigation provides a new way for further improving the photoelectric conversion efficiency of the DSSCs.

The properties and catalytic performance of Co/TiO2 nanotubes prepared by impregnation (Imp) and homogeneous precipitation (HP) for Fischer–Tropsch synthesis were investigated. HP makes cobalt particles enrich the exterior surface of the support, while for the Imp catalyst, cobalt particles are distributed on both external and internal surfaces of the support. The HP catalyst displays a twofold higher activity as well as superior C5+ selectivity. The low activity of the Imp catalyst can be attributed to the strong Co–TiO2 interaction and less available active cobalt sites.

A dual Z-scheme fe2O3@MnO2 core/shell nanocube supported C3N4 ternary composite is rationally designed and successfully fabricated as a photocatalyst for water splitting. The as-prepared Fe2O3@MnO2/C3N4 ternary composite exhibits an enhanced visible light-induced absorbance capacity and superior photocatalytic activity for direct water splitting than that of pure g-C3N4. The photocatalytic efficiency is investigated by varying amounts of Fe2O3@MnO2 core/shell nanocubes in the ternary composite (10%wt, 20%wt and 30%wt). When the mass fraction of Fe2O3@MnO2 is determined to be 20%, the hydrogen evolution rate would achieve the maximum with a value of 124 μmol*h−1. The improved photocatalytic performance of Fe2O3@MnO2/C3N4 ternary composite can be mainly attributed to improved visible light absorption range and construction of an effective dual Z-scheme interfacial heterojunction with a rapid separation and transfer of electron-hole pairs.

Nanosheet-assembled hierarchical flower-like titanium phosphate (TiP) is synthesized via hydrothermal treatment of H-titanate nanotubes (Ti-NT) at the optimized conditions of 0.1 M of H3PO4 and hydrothermal temperature of 130 °C. A possible formation mechanism for the TiP flowers, involving the disintegration of Ti-NT and the growth and assembling of TiP nanosheets, is proposed. The main compositions of the uncalcined TiP flowers are titanium hydrogen phosphate hydrates (Ti(HPO4)2·xH2O), which can be transformed to titanium phosphate (TiP2O7) after high temperature calcination. The photocatalytic activity of the prepared TiP flowers is increased with the increased calcination temperature, which may be attributed to the better photocatalytic activity of TiP2O7 than Ti(HPO4)2·xH2O and the increased crystallization of TiP2O7.