Oxygen defect modulating the charge behavior in titanium dioxide for boosting photocatalytic nitrogen fixation performance

Extremely high-temperature and high-pressure requirement of Haber-Bosch process motivates the search for a sustainable ammonia synthesis approach under mild conditions.Photocatalytic technology is a potential solution to convert N2 to ammonia.However,the poor light absorption and low charge carrier separation efficiency in conventional semiconductors are bottlenecks for the application of this technology.Herein,a facile synthesis of anatase TiO_(2)nanosheets with an abundance of surface oxygen vacancies(TiO_(2)-OV)via the calcination treatment was reported.Photocatalytic experiments of the prepared anatase TiO_(2)samples showed that TiO_(2)-OV nanosheets exhibited remarkably increased ammonia yield for solar-driven N2 fixation in pure water,without adding any sacrificial agents.EPR,XPS,XRD,UV-Vis DRS,TEM,Raman,and PL techniques were employed to systematically explore the possible enhanced mechanism.Studies revealed that the introduced surface oxygen vacancies significantly extended the light absorption capability in the visible region,decreased the adsorption and activation barriers of inert N2,and improved the separation and transfer efficiency of the photogenerated electronhole pairs.Thus,a high rate of ammonia evolution in TiO_(2)-OV was realized.This work offers a promising and sustainable approach for the efficient artificial photosynthesis of ammonia.

Strain‑Induced Surface Interface Dual Polarization Constructs PML‑Cu/Bi_(12)O_(17)Br_(2) High‑Density Active Sites for CO_(2) Photoreduction

The insufficient active sites and slow interfacial charge trans-fer of photocatalysts restrict the efficiency of CO_(2) photoreduction.The synchronized modulation of the above key issues is demanding and chal-lenging.Herein,strain-induced strategy is developed to construct the Bi–O-bonded interface in Cu porphyrin-based monoatomic layer(PML-Cu)and Bi_(12)O_(17)Br_(2)(BOB),which triggers the surface interface dual polarization of PML-Cu/BOB(PBOB).In this multi-step polarization,the built-in electric field formed between the interfaces induces the electron transfer from con-duction band(CB)of BOB to CB of PML-Cu and suppresses its reverse migration.Moreover,the surface polarization of PML-Cu further promotes the electron converge in Cu atoms.The introduction of PML-Cu endows a high density of dispersed Cu active sites on the surface of PBOB,significantly promoting the adsorption and activation of CO_(2) and CO desorption.The conversion rate of CO_(2) photoreduction to CO for PBOB can reach 584.3μmol g-1,which is 7.83 times higher than BOB and 20.01 times than PML-Cu.This work offers valuable insights into multi-step polarization regulation and active site design for catalysts.

Coupling of BiOCl Ultrathin Nanosheets with Carbon Quantum Dots for Enhanced Photocatalytic Performance

Over the past few decades,photocatalysis technology has received extensive attention because of its potential to mitigate or solve energy and environmental pollution problems.Designing novel materials with outstanding photocatalytic activities has become a research hotspot in this field.In this study,we prepared a series of photocatalysts in which BiOCl nanosheets were modified with carbon quantum dots(CQDs)to form CQDs/BiOCl composites by using a simple solvothermal method.The photocatalytic performance of the resulting CQDs/BiOCl composite photocatalysts was assessed by rhodamine B and tetracycline degradation under visible-light irradiation.Compared with bare BiOCl,the photocatalytic activity of the CQDs/BiOCl composites was significantly enhanced,and the 5 wt%CQDs/BiOCl composite exhibited the highest photocatalytic activity with a degradation efficiency of 94.5%after 30 min of irradiation.Moreover,photocatalytic N_(2)reduction performance was significantly improved after introducing CQDs.The 5 wt%CQDs/BiOCl composite displayed the highest photocatalytic N_(2)reduction performance to yield NH_3(346.25μmol/(g h)),which is significantly higher than those of 3 wt%CQDs/BiOCl(256.04μmol/(g h)),7 wt%CQDs/BiOCl(254.07μmol/(g h)),and bare BiOCl(240.19μmol/(g h)).Our systematic characterizations revealed that the key role of CQDs in improving photocatalytic performance is due to their increased light harvesting capacity,remarkable electron transfer ability,and higher photocatalytic activity sites.

Construction of NH2-MIL-125(Ti)/Bi2WO6 composites with accelerated charge separation for degradation of organic contaminants under visible light irradiation

Photocatalysis is considered as an ideal strategy for water pollution treatment.However,it remains challenging to design a highly efficient photo-catalytic system through regulating the charge flow via a precise approach.In this work,a novel NH2-MIL-125(Ti)/Bi2WO6 composite was constructed via self-assembly growing Bi2WO6 nanosheets on NH2-MIL-125(Ti)material.The characterization results demonstrated that NH2-MIL-125(Ti)was successfully incorporated into Bi2WO6 and the photoexcited carriers could be efficiently separated and transferred between the two components.NH2-MIL-125(Ti)/Bi2WO6 composites displayed enhanced photocatalytic activity for the removal of rhodamine B(RhB)and tetracycline(TC)under visible light irradiation,and the optimal weight ratio of NH2-MIL-125(Ti)was determined to be 7 wt%.The introduction of NH2-MIL-125(Ti)into Bi2WO6 could raise the absorption of visible light,accelerate the separation and transfer of charge carriers,and boost photocatalytic activity.This research presents a wide range of possibilities for the further development of novel composites in the field of environment purification.

Enhancing the cycling stability of Na-ion batteries by bonding MoS2 on assembled carbon-based materials

Room temperature Na-ion batteries(SIBs) show great potential for use as renewable energy storage systems.However, the large-scale application of SIBs has been hindered by the lack of an ideal SIBs anode material. We synthesized MoS2 on carbonized graphene-chitosan(G-C) using the hydrothermal method. The strong interaction between the MoS2 and the G-C greatly improved the electron transport rate and maintained the structural stability of the electrode, which lead to both an excellent rate capability and long cycle stability. The G-C monolith was proven to enhance the electrical conductivity of the composites and served as a matrix for uniformly dispersing active MoS2 nanosheets(NSs), as well as being a buffer material to adapt to changes in volume during the cycle.Serving as an anode material for SIBs, the MoS2-G-C electrode showed good cycling stability(527.3mAh g-1 at100 m A g-1 after 200 cycles), excellent rate capability, and a long cycle life(439.1 m Ah g-1 at 1 A g-1 after 200 cycles).

Layer-Contacted Graphene-Like BN/Ultrathin Bi_(3)O_(4)Br Stacking for Boosting Photocatalytic Molecular Oxygen Activation

Novel graphene-like boron nitride(BN)/Bi_(3)O_(4)Br photocatalysts have been controllably synthesized through a facile solvothermal method for the first time. Layer contact stacking between graphene-like BN and ultrathin Bi_(3)O_(4)Br was achieved with strong interaction. Dehalogenation is designed to harvest more visible light, and the ultrathin structure of Bi_(3)O_(4)Br is designed to accelerate charge transfer from inside to the surface. After graphene-like BN was engineered, photocatalytic performance greatly improved under visible light irradiation. Graphene-like BN can act as a surface electron-withdrawing center and adsorption center, facilitating molecular oxygen activation. O_(2)^(·-)was determined to be the main active species during the degradation process through analyses of electron spin resonance and XPS valence band spectra.

In situ N-doped Bi_(3)O_(4)Br/(BiO)_(2)CO_(3) ultrathin nanojunctions with matched energy band structure for nonselective photocatalysis pollutant removal

Novel N-doped Bi_(3)O_(4)Br/(BiO)_(2)CO_(3) ultrathin nanojunctions have been prepared.Alkalization dehalogenation was performed to form Bi_(3)O_(4)Br,surfactant was employed to control the ultrathin thickness,and few-layers of C_(3)N_(4) as a sacrificial agent were used to build the N-doped(BiO)_(2)CO_(3).The photocatalytic behavior of the achieved N-doped Bi_(3)O_(4)Br/(BiO)_(2)CO_(3) ultrathin nanojunctions was evaluated through the degradation of antibiotic agent ciprofloxacin,tetracycline hydro-chloride,and endocrine disrupting chemical bisphenol A as well as typical dye rhodamine B under visible light irradiation.The matched energy band structure between Bi_(3)O_(4)Br and(BiO)_(2)CO_(3) could endow the highly efficient interfacial charge separation,thus leading to excellent nonselective photocatalytic behavior.The structure design in this system will open new windows for the reasonable design of other photocatalysts.

Cu^2+改性g-C3N4光催化剂的光催化性能

本文通过将Cu^2+掺入g-C3N4结构中成功制备了Cu/g-C3N4光催化剂,并进一步优化其光催化性能。同时,采用多种表征方法对Cu/g-C3N4光催化剂的结构、形貌、光学和光电性能进行了分析。X射线衍射(XRD)和X射线光电子能谱(XPS)结果表明制备的光催化剂为Cu/g-C3N4,且Cu的价态为+2。在可见光照射下,研究了不同铜含量的Cu/g-C3N4和gC3N4光催化剂的光催化活性。实验结果表明,Cu/g-C3N4光催化剂的降解能力显著高于纯相的g-C3N4。N2吸附-解吸等温线表明,Cu^2+的引入对g-C3N4的微观结构影响不大,说明光催化活性的提高可能与光生载流子的有效分离有关。因此,Cu/g-C3N4光催化降解RhB和CIP性能的提升可能是由于Cu^2+可以作为电子捕获陷阱从而降低了载流子的复合速率。通过光电测试表明,在g-C3N4中掺入Cu^2+可以降低g-C3N4的电子空穴复合速率,加速电子空穴对的分离,从而提高了其光催化活性。自由基捕获实验和电子自旋共振(ESR)结果表明,超氧自由基(O2·-)、羟基自由基(·OH)和空穴的协同作用提高了Cu/g-C3N4光催化剂的光催化活性。

Hexagonal boron nitride adsorbent: Synthesis, performance tailoring and applications

Hexagonal boron nitride(h-BN),with unique structural and properties,has shown enormous potentitoward variety of possible applications.By virtue of partially-ionic character of BN chemical bonds anusually large specific surface area,h-BN-related nanostructures exhibit appealing adsorption propertiewhich can be widely applied for separation and purification towards energy and environment treatmenIn this review,recent progress in designing h-BN micro,nano-structure,controlled synthesis,performancoptimizing as well as energy and environment-related adsorption applications are summarized.Strategieto tailor the h-BN can be classified as morphology control,element doping,defect control and surfacmodification,focusing on how to optimize the adsorption performance.In order to insight the intrinsimechanism of tuning strategies for property optimization,the significant adsorption applications of h-Btowards hydrogen storage,CO2 capture,pollutants removal from water and adsorption desulfurization arpresented.

Boosting photocatalytic degradation of RhB via interfacial electronic effects between Fe-based ionic liquid and g-C_3N_4

The Fe-based ionic liquid doped g-C_3N_4(Fee CN) photocatalyst was firstly prepared base on ultrathin g-C_3N_4 obtained by multiple calcination method with a metal-based reactive ionic liquid [Omim]FeCl_4 for the degradation of Rhodamine B(RhB). Experimental results revealed that Fe3+species were doped into the framework of g-C_3N_4. The effect of the amount of Fe-doping on the catalytic activity was performed. The result showed that the Fee CN could effectively degrade RhB under the condition of visible light irradiation. The photocurrent analysis showed that the incorporation of Fe^(3+)into g-C_3N_4 material could accelerate the separation of the photogenerated carriers significantly.At the same time, the reactive species generated during the photodegradation process were tested by radicals trapping experiments and electron spin resonance(ESR). It was proposed that the synergistic effect of■ and ·OH contributed to degrade RhB efficiently.

Facile microwave-assisted ionic liquid synthesis of sphere-like BiOBr hollow and porous nanostructures with enhanced photocatalytic performance

In this work, two kinds of self-assembled hierarchical BiOBr microcrystals were rapidly synthesized through a simple microwave-assisted route in the presence of reactable ionic liquid 1-hexadecyl-3-methylimidazolium bromide([C_(16)mim]Br). These porous and hollow BiOBr microspheres were obtained via a facile solvothermal method with or without polyvinyl pyrrolidone(PVP), respectively. During the synthetic process, ionic liquid [C_(16)mim]Br played as solvent, reactant and template at the same time. Moreover, the BiOBr hollow and porous microspheres exhibited outstanding photocatalytic activities for the degradation of rhodamine B(RhB) under visible light irradiation. A possible photocatalytic mechanism was also discussed in detail. It can be assumed that the higher photocatalytic activities of BiOBr porous microspheres materials could be ascribed to the novel structure, larger specific surface area, narrower band gap structure and smaller particle size.

Biomass-derived hard carbon microtubes with tunable apertures for high-performance sodium-ion batteries

Sodium-ion batteries(SIBs)are considered the most up-and-coming complements for large-scale energy storage devices due to the abundance and cheap sodium.However,due to the bigger radius,it is still a great challenge to develop anode materials with suitable space for the intercalation of sodium ions.Herein,we present hard carbon microtubes(HCTs)with tunable apertures derived from low-cost natural kapok fibers via a carbonization process for SIBs.The resulted HCTs feature with smaller surface area and shorter Na+diffusion path benefitting from their unique micro-nano structure.Most importantly,the wall thickness of HCTs could be regulated and controlled by the carbonization temperature.At a high temperature of 1,600℃,the carbonized HCTs possess the smallest wall thickness,which reduces the diffusion barrier of Na+and enhances the reversibility Na+storage.As a result,the 1600HCTs deliver a high initial Coulombic efficiency of 90%,good cycling stability(89.4%of capacity retention over 100 cycles at 100 mA·g^(−1)),and excellent rate capacity.This work not only charts a new path for preparing hard carbon materials with adequate ion channels and novel tubular micro-nano structures but also unravels the mechanism of hard carbon materials for sodium storage.

Construction of high-efficiency CoS@Nb_(2)O_(5) heterojunctions accelerating charge transfer for boosting photocatalytic hydrogen evolution

The random movement and easy recombination of photoinduced charges lead to a low conversion efficiency for photocatalytic hydrogen evolution.The cocatalyst design is a promising route to address such problem through introducing an appropriate cocatalyst on the semiconductor photocatalysts to construct the high-efficiency heterojunctions.Herein,novel CoS/Nb_(2)O_(5) heterojunctions were constructed via in-situ loading CoS cocatalyst on the surface of Nb_(2)O_(5) nanosheets.Through the femtosecond-resolved transient absorption spectroscopy,the average lifetime of charge carriers for 10 wt% CoS/Nb_(2)O_(5)(159.6 ps)is drastically shortened by contrast with that of Nb_(2)O_(5)(5531.9 ps),strongly suggesting the rapid charge transfer from Nb_(2)O_(5) to CoS.The significantly improved charge-transfer capacity contributes to a high photocatalytic hydrogen evolution rate of 355µmol/h,up to 17.5 times compared with pristine Nb_(2)O_(5).This work would provide a new design platform in the construction of photocatalytic heterojunctions with high charge-transfer efficiency.

Lower oxygen vacancy concentration in BiPO_(4)with unexpected higher photocatalytic activity

Defect engineering has been demonstrated to be an appealing strategy to boost the photocatalytic activity of materials.However,can higher defect concentration bring about higher photocatalytic activity?This is an open question.In this work,BiPO_(4)photocatalysts with controllable oxygen vacancy concentrations were successfully synthesized.The photocatalytic activity of the obtained BiPO_(4)photocatalysts was determined by the removal of ciprofloxacin and 4-chlorophenol,as well as CO_(2)photoreduction.The BiPO4materials with lower oxygen vacancy concentration could display unexpected higher photocatalytic efficiency.Through the investigation of different factors which may affect the photocatalytic performance,such as crystal structure,morphology,specific surface area,defect,and energy band structure,it can be found that the energy band structure difference was responsible for the enhanced photocatalytic activity.

Enhanced photocatalytic performance of carbon quantum dots/Bi OBr composite and mechanism investigation

Novel carbon quantum dots（CQDs）/Bi OBr composite photocatalysts have been constructed through a facile hydrothermal synthesis in the presence of ionic liquid 1-hexadecyl-3-methylimidazolium bromide（[C16 mim]Br）. Series of characterizations have been performed to confirm the uniform distribution of CQDs in Bi OBr nanosheets and the synergistic effect for photocatalytic degradation organic pollutants between CQDs and Bi OBr. The results show that 3.1 wt% CQDs/Bi OBr photocatalyst possesses the best photocatalytic activity for the degradation of colorless antibiotic tetracycline（TC）, endocrine disrupter bisphenol A（BPA） and dye rhodamine B（Rh B）, under visible light irradiation, which exhibited the highest photocatalytic performance. The enhanced photocatalytic performance for CQDs/Bi OBr composites could be attributed to the wider optical absorption range and fast separation of photogenerated charge carriers after the introduction of CQDs. The key roles of CQDs for the enhanced photocatalytic activity of Bi OBr have been discussed. A possible mechanism of CQDs/Bi OBr on the enhancement of visible light performance was proposed.

Space-confined microwave synthesis of ternary-layered BiOCl crystals with high-performance ultraviolet photodetection

In recent years,two-dimensional(2D)ternary materials have attracted wide attention due to their novel properties which can be achieved by regulating their chemical composition with a very great degree of freedom and adjustable space.However,as for the precise synthesis of 2D ternary materials,great challenges still lie ahead that hinder their further development.In this work,we demonstrated a simple and reliable approach to synthesize 2D ternary-layered BiOCl crystals through a microwave-assisted space-confined process in a short time(<3 minutes).Their ultraviolet(UV)detection performance was analyzed systematically.The photodetectors based on the as-obtained BiOCl platelets demonstrate high sensitivity to 266-nm laser illumination.The responsivity is calculated to be8 A/W and the response time is up to be18 ps.On the other hand,the device is quite stable after being exposed in the ambient air within 3 weeks and the response is almost unchanged during the measurement.The facile and fast synthesis of single crystalline BiOCl platelets and its high sensitivity to UV light irradiation indicate the potential optoelectronic applications of 2D BiOCl photodetectors.

2D/2D atomic double-layer WS_(2)/Nb_(2)O_(5)shell/core nanosheets with ultrafast interfacial charge transfer for boosting photocatalytic H_(2)evolution

Low-efficiency charge transfer is a critical factor to limit the photocatalytic H_(2)evolution activity of semiconductor photocatalysts.The interface design is a promising approach to achieve high chargetransfer efficiency for photocatalysts.Herein,a new 2 D/2 D atomic double-layer WS_(2)/Nb_(2)O_(5)shell/core photocatalyst(DLWS/Nb_(2)O_(5))is designed.The atom-resolved HAADF-STEM results unravel the presence of an unusual 2 D/2 D shell/core interface in DLWS/Nb_(2)O_(5).Taking advantage of the advanced femtosecond-resolved ultrafast TAS spectra,the average lifetime of charge carriers for DLWS/Nb_(2)O_(5)(180.97 ps)is considerably shortened as compared to that of Nb_(2)O_(5)(230.50 ps),strongly indicating that the 2 D/2 D shell/core interface enables DLWS/Nb_(2)O_(5)to achieve ultrafast charge transfer from Nb_(2)O_(5)to atomic double-layer WS_(2),thus yielding a high photocatalytic H_(2)evolution rate of 237.6 mmol/h,up to10.8 times higher than that of pure Nb_(2)O_(5)nanosheet.This study will open a new window for the development of high-efficient photocatalytic systems through the interface design.

Surfactant-assisted hydrothermal synthesis of MoS_(2) micro-pompon structure with enhanced photocatalytic performance under visible light

MoS_(2) nanomaterial with the micro-pompon structure was synthesized by a surfactant-assisted hydrothermal method.The morphologies and structures of as-prepared MoS_(2) micro-pompon were investigated by adding different types of surfactants such as cetyltrimethyl ammonium bromide(CTAB),sodium dodecylbenzene sulphonate(SDBS),and polyvinyl pyrrolidone(PVP).The results indicated that the morphology of MoS_(2) could be controlled and changed effectively by the cationic sur-factant of CTAB.A reasonable growth mechanism for hollow structured MoS_(2) micro-pompon by hydrothermal processes was proposed.Further,photocatalytic degradation properties of MoS_(2) micro-pompon under visible light were evaluated by degradation of common organic dyes,which include rhodamine B(RhB),congo red,methyl orange,and methylene blue.The results indicated that MoS_(2) micro-pompon owned the highly selective catalytic ability to RhB with degradation efficiency of 95%in 60 min and 68%in 30 min.With the additive of the surfactant,the MoS_(2)-CTAB sample exhibited an enhanced ability of photocatalytic activity where degradation efficiency was improved to 92%in 30 min.The method employed in this work could be expanded to fabricate other sulfides with the controllable morphology and structure to further regulate the photocatalytic performance.