In this work, a novel heterojunction composite Ag_(2)S/KTa_(x)Nb_(1-x)O_(3)was designed and synthesized through a combination of hydrothermal and precipitation procedures. The Ta/Nb ratio of the KTa_(x)Nb_(1-x)O_(3)an...In this work, a novel heterojunction composite Ag_(2)S/KTa_(x)Nb_(1-x)O_(3)was designed and synthesized through a combination of hydrothermal and precipitation procedures. The Ta/Nb ratio of the KTa_(x)Nb_(1-x)O_(3)and the Ag_(2)S content were optimized. The best 0.5% Ag_(2)S/KTa_(0.5)Nb_(0.5)O_(3)(KTN) sample presents an enhanced photocatalytic performance in ammonia synthesis than KTN and Ag_(2)S. Under simulated sunlight, the NH_(3)generation rate of 0.5% Ag_(2)S/KTN reaches 2.0 times that of pure KTN. Under visible light, the reaction rate ratio of the two catalysts is 6.0.XRD, XPS, and TEM analysis revealed that Ag2S was intimately decorated on the KTN nanocubes surface, which promoted the electron transfer between the two semiconductors. The band structure investigation indicated that the Ag_(2)S/KTN heterojunction established a type-Ⅱ band alignment with intimate contact, thus realizing the effective transfer and separation of photogenerated carriers. The change in charge separation was considered as the main reason for the enhanced photocatalytic performance. Interestingly, the Ag_(2)S/KTN composite exhibited higher NH3generation performance under the combined action of ultrasonic vibration and simulated sunlight. The enhanced piezo-photocatalytic performance can be ascribed that the piezoelectric effect of KTN improved the bulk separation of charge carriers in KTN. This study not only provides a potential catalyst for photocatalytic nitrogen fixation but also shows new ideas for the design of highly efficient catalysts via semiconductor modification and external field coupling.展开更多
Two-dimensional carbon nitride(2 D-C_(3) N_(4))nanosheets are promising materials in photocatalytic water splitting,but still suffer from easy agglomeration and fast photogene rated electron-hole pairs recombination.T...Two-dimensional carbon nitride(2 D-C_(3) N_(4))nanosheets are promising materials in photocatalytic water splitting,but still suffer from easy agglomeration and fast photogene rated electron-hole pairs recombination.To tackle this issue,herein,a hierarchical Nb_(2) O_(5)/2 D-C_(3) N_(4) heterostructure is precisely constructed and the built-in electric field between Nb_(2)O_(5) and 2 D-C_(3) N_(4) can provide the driving force to separate/transfer the charge carriers efficiently.Moreover,the strongly Lewis acidic Nb_(2)O_(5) can adsorb TEOA molecules on its surface at locally high concentrations to facilitate the oxidation reaction kinetics under irradiation,resulting in efficient photogene rated electrons-holes separation and exceptional photocatalytic hydrogen evolution.As expected,the champion Nb_(2)O_(5)/2 D-C_(3)N_(4) heterostructure achieves an exceptional H2 evolution rate of 31.6 mmol g^(-1) h^(-1),which is 213.6 times and 4.3 times higher than that of pristine Nb_(2)O_(5) and2 D-C_(3)N_(4),respectively.Moreover,the champion heterostructure possesses a high apparent quantum efficiency(AQE)of 45.08%atλ=405 nm and superior cycling stability.Furthermore,a possible photocatalytic mechanism of the energy band alignment at the hetero-interface is proposed based on the systematical characterizations accompanied by density functional theory(DFT)calculations.This work paves the way for the precise construction of a high-quality heterostructured photocatalyst with efficient charge separation to boost hydrogen production.展开更多
Constructing a suitable heterojunction photocatalytic system from two photocatalytic materials is an efficient approach for designing extremely efficient photocatalysts for a broader range of environmental,medical,and...Constructing a suitable heterojunction photocatalytic system from two photocatalytic materials is an efficient approach for designing extremely efficient photocatalysts for a broader range of environmental,medical,and energy applications.Recently,the construction of a step-scheme heterostructure system(hereafter called the S-scheme)has received widespread attention in the photocatalytic field due to its ability to achieve efficient photogenerated carrier separation and obtain strong photo-redox ability.Herein,a novel S-scheme heterojunction system consisting of 2D O-doped g-C_(3)N_(4)(OCN)nanosheets and 3D N-doped Nb_(2)O_(5)/C(N-NBO/C)nanoflowers is constructed via ultrasonication and vigorous agitation technique followed by heat treatment for the photocatalytic degradation of Rhodamine B(RhB).Detailed characterization and decomposition behaviour of RhB showed that the fabricated material shows excellent photocatalytic efficiency and stability towards RhB photodegradation under visible-light illumination.The enhanced performance could be attributed to the following factors:fast charge transfer,highly-efficient charge separation,extended lifetime of photoinduced charge carriers,and the high redox capability of the photoinduced charges in the S-scheme system.Various trapping experiment conditions and electron paramagnetic resonance provide clear evidence of the S-scheme photogenerated charge transfer path,meanwhile,the RhB mineralization degradation pathway was also investigated using LC-MS.This study presents an approach to constructing Nb_(2)O_(5)-based S-scheme heterojunctions for photocatalytic applications.展开更多
At present,the high re-combination rate of photogenerated carriers and the low redox capability of the photocatalyst are two factors that severely limit the improvement of photocatalytic performance.Herein,a dual Z-sc...At present,the high re-combination rate of photogenerated carriers and the low redox capability of the photocatalyst are two factors that severely limit the improvement of photocatalytic performance.Herein,a dual Z-scheme photocatalyst bismuthzirconate/graphitic carbon nitride/silver phosphate (Bi_(2)Zr_(2)O_(7)/g-C_(3)N4/Ag_(3)PO_(4)(BCA)) was synthesized using a co-precipitation method,and a dual Z-scheme heterojunction photocatalytic system was established to decrease the high re-combination rate of photogenerated carriers and consequently improve the photocatalytic performance.The re-combination of electron-hole pairs(e-and h+) in the valence band (VB) of g-C_(3)N4increases the redox potential of e-and h+,leading to significant improvements in the redox capability of the photocatalyst and the efficiency of e--h+separation.As a photosensitizer,Ag_(3)PO_(4)can enhance the visible light absorption capacity of the photocatalyst.The prepared photocatalyst showed strong stability,which was attributed to the efficient suppression of photo-corrosion of Ag_(3)PO_(4)by transferring the e-to the VB of g-C_(3)N4.Tetracycline was degraded efficiently by BCA-10%(the BCA with 10 wt.%of AgPO_(4)) under visible light,and the degradation efficiency was up to 86.2%.This study experimentally suggested that the BCA photocatalyst has broad application prospects in removing antibiotic pollution.展开更多
Photothermal carbon dioxide hydrogenation represents a promising route to reduce the emission of greenhouse gas CO_(2)and produce value-added chemicals,but the selectivity and stability of photothermal catalysts need ...Photothermal carbon dioxide hydrogenation represents a promising route to reduce the emission of greenhouse gas CO_(2)and produce value-added chemicals,but the selectivity and stability of photothermal catalysts need to be improved.Herein,we report the rational fabrication of well-defined Ag_(24)Au cluster decorated highly ordered nanorod-like mesoporous Co_(3)O_(4)(Ag_(24)Au/mesoCo_(3)O_(4))for highly efficient and selective CO_(2)hydrogenation.The orderly assembled meso-Co_(3)O_(4)nanorods were prepared via a nanocasting method,offering large surface area and abundant active sites for CO_(2)adsorption and conversion.Moreover,the catalytic activity and selectivity were further improved by molecule-like Ag_(24)Au cluster decoration and reaction temperature optimization.The Ag_(24)Au/meso-Co_(3)O_(4)composite catalyst exhibited an ultrahigh CH_(4)yield rate of 204 mmol·g^(−1)·h^(−1)and a greatly improved CH_(4)selectivity of 82%for CO_(2)hydrogenation,significantly higher than those of pristine meso-Co_(3)O_(4)catalyst.The mechanism of the photothermal catalytic performance improvement was verified by CO_(2)temperature-programmed desorption and time-resolved transient photoluminescence,revealing that CO_(2)molecules underwent a vigorous adsorption and rapid activation process over Ag_(24)Au/meso-Co_(3)O_(4).The hot electrons created by the localized surface plasmon resonance effect of Ag_(24)Au clusters facilitated the charge transfer for subsequent multi-electron CO_(2)hydrogeneration processes,resulting in a significant increase in the productivity and selectivity for CO_(2)-to-CH_(4)conversion.This work suggests that the rational coupling of well-defined metal atom clusters and ordered transition metal compound nanostructures could open a new avenue towards photoinduced green chemistry processes for efficient CO_(2)recycling and reutilization.展开更多
Semiconductor heterojunction plays a pivotal role in photocatalysis.However,the construction of a heterojunction with a fine microstructure usually requires complex synthetic procedures.Herein,a pH-adjusted one-step m...Semiconductor heterojunction plays a pivotal role in photocatalysis.However,the construction of a heterojunction with a fine microstructure usually requires complex synthetic procedures.Herein,a pH-adjusted one-step method was employed to controllably synthesize Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) heterojunction with a well-tuned 0D/1D hierarchical structure for the first time.It is noteworthy that the ordered stacking of vanadium oxide tetrahedron(VO_(3)-)guided by the pH value wisely realizes the in-situ growth of Ag_(4)V_(2)O_(7) nanoparticles on the surface of Ag_(3)VO_(4) nanorods.Furthermore,comprehensive characterization and calculation decipher the electronic structures of Ag_(4)V_(2)O_(7) and Ag_(3)VO_(4) and the formation of Z-scheme heterojunction,benefiting the visible light harvesting and carrier utilization.Such a new Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) heterojunction exhibits remarkable photocatalytic activity and excellent stability.Complete degradation of Rhodamine B(RhB)can be achieved in 10 min by the Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) heterojunction under visible light irradiation,demonstrating an outstanding reaction rate of 0.35 min^(−1) that is up to 84-fold higher than those of other silver vanadates.More importantly,this integration of synthesis technology and heterojunction design,based on the intrinsic crystal and electronic structures,could be inspiring for developing novel heterostructured materials with advanced performance.展开更多
Bismuth titanate (Bi_(4)Ti_(3)O_(12),BIT)piezoelectric materials have attracted increasing attention due to their high-temperature applications.However,it is quite challenging to simultaneously achieve outstanding pie...Bismuth titanate (Bi_(4)Ti_(3)O_(12),BIT)piezoelectric materials have attracted increasing attention due to their high-temperature applications.However,it is quite challenging to simultaneously achieve outstanding piezoelectric properties and high Curie temperature in BIT-based systems.In this study,oxygen vacancy defects tailoring strategy was utilized to solve this problem,excellent piezoelectric coefficient(32.1 pC/N),and ultrahigh Curie temperature(659℃)are gotten in Bi_(4)Ti_(3)-x(Mn_(1/3)Nb_(2/3))xO_(12)(BTMN)ceramics,which are among the top values in the BIT-based ceramics.More importantly,the(Mn_(1/3)Nb_(2/3))(4+d)+complex-ion modified Bi_(4)Ti_(3)O_(12)-based ceramics are characterized with excellent piezoelectric stability up to 500℃(d33>30.0 pC/N at 500℃))and significantly reduced conductivity(only~10^(-7)U-1 cm^(-1)at 500℃).Moreover,enhanced ferroelectricity and good dielectric stability were also obtained.The better comprehensive properties can be ascribed to two aspects.First,the concentration of oxygen vacancy defects is obviously reduced,and their distribution is effectively controlled in BITMN ceramics.Second,the introduction of(Mn_(1/3)Nb_(2/3))^((4+δ)+)complex-ion gives rise to the antiphase boundaries and massive ferroelectric domain walls.This works not only reveal the high potential of BITMN ceramics for high-temperature piezoelectric applications but also deepen the understanding of the structure-properties relationship in BIT-based materials.展开更多
The low separation/migration efficiency is a major obstacle that limits the practical application of semiconductor-photocatalysts. Constructing S-scheme heterojunction is an ideal strategy for providing high photocata...The low separation/migration efficiency is a major obstacle that limits the practical application of semiconductor-photocatalysts. Constructing S-scheme heterojunction is an ideal strategy for providing high photocatalytic activity via accelerating charge separation. Herein, an AgPO/CNcomposite was synthesized by coupling AgPOparticle with CNhollow spheres in-situ via a precipitation method. The S-scheme hete-rojunction between AgPOand CNcould accelerate the charge separation and retain high photoredox ability, which synchronously realized high photocatalytic oxygen production and hexavalent chromium reduction. The optimized Ag3PO4/CNcomposite shows a high oxygen production rate up to 803.31 μmol·g·hand a high conversion(87.9%) of Cr(Ⅵ) to Cr(Ⅲ). In addition, CNhollow spheres affords higher reaction efficiency than that of CNtube, CNbulk and CNsheet, which indicates that the hollow sphere structure can provide more active sites and adsorption sites in the photocatalytic process. This work offers an effective way in developing a dual-function S-scheme heterojunction for clean energy production and environmental protection.展开更多
The high melting point and strong chemical bonding of NbB_(2)pose a great challenge to the preparation of high-density nanostructured NbB_(2)composite coating.Herein,we report a novel,simple,and efficient method to fa...The high melting point and strong chemical bonding of NbB_(2)pose a great challenge to the preparation of high-density nanostructured NbB_(2)composite coating.Herein,we report a novel,simple,and efficient method to fabricate in-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating by plasma spraying Nb_(2)O_(5)–B_(4)C–Al composite powder,aiming at realizing the higher densification and ultra-fine microstructure of NbB_(2)composite coating.The microstructure and properties of in-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating were studied comparatively with ex-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating(plasma spraying NbB_(2)–NbC–Al_(2)O_(3)composite powder).The reaction mechanism of Nb_(2)O_(5)–B_(4)C–Al composite powder in plasma jet was analyzed in detail.The results showed that the in-situ nanostructured NbB_(2)–NbC–Al_(2)O_(3)composite coating presented a lower porosity and superior performance including higher microhardness,toughness and wear resistance compared to the plasma sprayed ex-situ NbB_(2)–NbC–Al_(2)O_(3)coating and other boride composite coatings.Densification of the in-situ NbB_(2)–NbC–Al_(2)O_(3)coating was attributed to the low melting point of Nb_(2)O_(5)–B_(4)C–Al composite powder and the exothermic effect of in-situ reaction.The superior performance was ascribed to the density improvement and the strengthening and toughening effect of the nanosized phases.The in-situ reaction path could be expressed as:Nb_(2)O_(5)+Al®Nb+Al_(2)O_(3),and Nb+B_(4)C®NbB_(2)+NbC.展开更多
基金financially supported by National Natural Science Foundation of China (Grant No. 22172144)Nature Science Foundation of Zhejiang Province (Grant No. LY20B030004)。
文摘In this work, a novel heterojunction composite Ag_(2)S/KTa_(x)Nb_(1-x)O_(3)was designed and synthesized through a combination of hydrothermal and precipitation procedures. The Ta/Nb ratio of the KTa_(x)Nb_(1-x)O_(3)and the Ag_(2)S content were optimized. The best 0.5% Ag_(2)S/KTa_(0.5)Nb_(0.5)O_(3)(KTN) sample presents an enhanced photocatalytic performance in ammonia synthesis than KTN and Ag_(2)S. Under simulated sunlight, the NH_(3)generation rate of 0.5% Ag_(2)S/KTN reaches 2.0 times that of pure KTN. Under visible light, the reaction rate ratio of the two catalysts is 6.0.XRD, XPS, and TEM analysis revealed that Ag2S was intimately decorated on the KTN nanocubes surface, which promoted the electron transfer between the two semiconductors. The band structure investigation indicated that the Ag_(2)S/KTN heterojunction established a type-Ⅱ band alignment with intimate contact, thus realizing the effective transfer and separation of photogenerated carriers. The change in charge separation was considered as the main reason for the enhanced photocatalytic performance. Interestingly, the Ag_(2)S/KTN composite exhibited higher NH3generation performance under the combined action of ultrasonic vibration and simulated sunlight. The enhanced piezo-photocatalytic performance can be ascribed that the piezoelectric effect of KTN improved the bulk separation of charge carriers in KTN. This study not only provides a potential catalyst for photocatalytic nitrogen fixation but also shows new ideas for the design of highly efficient catalysts via semiconductor modification and external field coupling.
基金Finacial support from the Natural Science Foundation of Jiangsu Province(BK20170549,BK20180887)the National Natural Science Foundation of China(21706103,62004084)+3 种基金Guangdong Innovation Research Team for Higher Education(2017KCXTD030)the High-level Talents Project of Dongguan University of Technology(KCYKYQD2017017)the Young Talent Cultivation Plan of Jiangsu UniversityJiangsu Provincial Program for High-Level Innovative and Entrepreneurial Talents Introduction。
文摘Two-dimensional carbon nitride(2 D-C_(3) N_(4))nanosheets are promising materials in photocatalytic water splitting,but still suffer from easy agglomeration and fast photogene rated electron-hole pairs recombination.To tackle this issue,herein,a hierarchical Nb_(2) O_(5)/2 D-C_(3) N_(4) heterostructure is precisely constructed and the built-in electric field between Nb_(2)O_(5) and 2 D-C_(3) N_(4) can provide the driving force to separate/transfer the charge carriers efficiently.Moreover,the strongly Lewis acidic Nb_(2)O_(5) can adsorb TEOA molecules on its surface at locally high concentrations to facilitate the oxidation reaction kinetics under irradiation,resulting in efficient photogene rated electrons-holes separation and exceptional photocatalytic hydrogen evolution.As expected,the champion Nb_(2)O_(5)/2 D-C_(3)N_(4) heterostructure achieves an exceptional H2 evolution rate of 31.6 mmol g^(-1) h^(-1),which is 213.6 times and 4.3 times higher than that of pristine Nb_(2)O_(5) and2 D-C_(3)N_(4),respectively.Moreover,the champion heterostructure possesses a high apparent quantum efficiency(AQE)of 45.08%atλ=405 nm and superior cycling stability.Furthermore,a possible photocatalytic mechanism of the energy band alignment at the hetero-interface is proposed based on the systematical characterizations accompanied by density functional theory(DFT)calculations.This work paves the way for the precise construction of a high-quality heterostructured photocatalyst with efficient charge separation to boost hydrogen production.
文摘Constructing a suitable heterojunction photocatalytic system from two photocatalytic materials is an efficient approach for designing extremely efficient photocatalysts for a broader range of environmental,medical,and energy applications.Recently,the construction of a step-scheme heterostructure system(hereafter called the S-scheme)has received widespread attention in the photocatalytic field due to its ability to achieve efficient photogenerated carrier separation and obtain strong photo-redox ability.Herein,a novel S-scheme heterojunction system consisting of 2D O-doped g-C_(3)N_(4)(OCN)nanosheets and 3D N-doped Nb_(2)O_(5)/C(N-NBO/C)nanoflowers is constructed via ultrasonication and vigorous agitation technique followed by heat treatment for the photocatalytic degradation of Rhodamine B(RhB).Detailed characterization and decomposition behaviour of RhB showed that the fabricated material shows excellent photocatalytic efficiency and stability towards RhB photodegradation under visible-light illumination.The enhanced performance could be attributed to the following factors:fast charge transfer,highly-efficient charge separation,extended lifetime of photoinduced charge carriers,and the high redox capability of the photoinduced charges in the S-scheme system.Various trapping experiment conditions and electron paramagnetic resonance provide clear evidence of the S-scheme photogenerated charge transfer path,meanwhile,the RhB mineralization degradation pathway was also investigated using LC-MS.This study presents an approach to constructing Nb_(2)O_(5)-based S-scheme heterojunctions for photocatalytic applications.
基金the financial support provided by the Shandong University Cross Project fund (No.2016JC003)。
文摘At present,the high re-combination rate of photogenerated carriers and the low redox capability of the photocatalyst are two factors that severely limit the improvement of photocatalytic performance.Herein,a dual Z-scheme photocatalyst bismuthzirconate/graphitic carbon nitride/silver phosphate (Bi_(2)Zr_(2)O_(7)/g-C_(3)N4/Ag_(3)PO_(4)(BCA)) was synthesized using a co-precipitation method,and a dual Z-scheme heterojunction photocatalytic system was established to decrease the high re-combination rate of photogenerated carriers and consequently improve the photocatalytic performance.The re-combination of electron-hole pairs(e-and h+) in the valence band (VB) of g-C_(3)N4increases the redox potential of e-and h+,leading to significant improvements in the redox capability of the photocatalyst and the efficiency of e--h+separation.As a photosensitizer,Ag_(3)PO_(4)can enhance the visible light absorption capacity of the photocatalyst.The prepared photocatalyst showed strong stability,which was attributed to the efficient suppression of photo-corrosion of Ag_(3)PO_(4)by transferring the e-to the VB of g-C_(3)N4.Tetracycline was degraded efficiently by BCA-10%(the BCA with 10 wt.%of AgPO_(4)) under visible light,and the degradation efficiency was up to 86.2%.This study experimentally suggested that the BCA photocatalyst has broad application prospects in removing antibiotic pollution.
基金supports from the National Key Research&Development Program of China(No.2017YFA0208200)the National Natural Science Foundation of China(Nos.22022505 and 21872069)+1 种基金the Fundamental Research Funds for the Central Universities(No.0205-14380266)the 2021 Suzhou Gusu Leading Talents of Science and Technology Innovation and Entrepreneurship in Wujiang District.
文摘Photothermal carbon dioxide hydrogenation represents a promising route to reduce the emission of greenhouse gas CO_(2)and produce value-added chemicals,but the selectivity and stability of photothermal catalysts need to be improved.Herein,we report the rational fabrication of well-defined Ag_(24)Au cluster decorated highly ordered nanorod-like mesoporous Co_(3)O_(4)(Ag_(24)Au/mesoCo_(3)O_(4))for highly efficient and selective CO_(2)hydrogenation.The orderly assembled meso-Co_(3)O_(4)nanorods were prepared via a nanocasting method,offering large surface area and abundant active sites for CO_(2)adsorption and conversion.Moreover,the catalytic activity and selectivity were further improved by molecule-like Ag_(24)Au cluster decoration and reaction temperature optimization.The Ag_(24)Au/meso-Co_(3)O_(4)composite catalyst exhibited an ultrahigh CH_(4)yield rate of 204 mmol·g^(−1)·h^(−1)and a greatly improved CH_(4)selectivity of 82%for CO_(2)hydrogenation,significantly higher than those of pristine meso-Co_(3)O_(4)catalyst.The mechanism of the photothermal catalytic performance improvement was verified by CO_(2)temperature-programmed desorption and time-resolved transient photoluminescence,revealing that CO_(2)molecules underwent a vigorous adsorption and rapid activation process over Ag_(24)Au/meso-Co_(3)O_(4).The hot electrons created by the localized surface plasmon resonance effect of Ag_(24)Au clusters facilitated the charge transfer for subsequent multi-electron CO_(2)hydrogeneration processes,resulting in a significant increase in the productivity and selectivity for CO_(2)-to-CH_(4)conversion.This work suggests that the rational coupling of well-defined metal atom clusters and ordered transition metal compound nanostructures could open a new avenue towards photoinduced green chemistry processes for efficient CO_(2)recycling and reutilization.
基金gratefully acknowledge the financial support of the National Natural Science Foundation of China(Nos.52102068,52202058,and 52073156)Science and Technology on Advanced Functional Composite Laboratory(No.6142906200509)+1 种基金State Key Laboratory of New Ceramics&Fine Processing Tsinghua University(No.KF202112)the Natural Science Foundation of Jiangsu Province(No.20KJB430017)and NUPTSF(No.NY219162).
文摘Semiconductor heterojunction plays a pivotal role in photocatalysis.However,the construction of a heterojunction with a fine microstructure usually requires complex synthetic procedures.Herein,a pH-adjusted one-step method was employed to controllably synthesize Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) heterojunction with a well-tuned 0D/1D hierarchical structure for the first time.It is noteworthy that the ordered stacking of vanadium oxide tetrahedron(VO_(3)-)guided by the pH value wisely realizes the in-situ growth of Ag_(4)V_(2)O_(7) nanoparticles on the surface of Ag_(3)VO_(4) nanorods.Furthermore,comprehensive characterization and calculation decipher the electronic structures of Ag_(4)V_(2)O_(7) and Ag_(3)VO_(4) and the formation of Z-scheme heterojunction,benefiting the visible light harvesting and carrier utilization.Such a new Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) heterojunction exhibits remarkable photocatalytic activity and excellent stability.Complete degradation of Rhodamine B(RhB)can be achieved in 10 min by the Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) heterojunction under visible light irradiation,demonstrating an outstanding reaction rate of 0.35 min^(−1) that is up to 84-fold higher than those of other silver vanadates.More importantly,this integration of synthesis technology and heterojunction design,based on the intrinsic crystal and electronic structures,could be inspiring for developing novel heterostructured materials with advanced performance.
基金supported by the National Natural Science Foundation of China,China(Grant No.51932010)by the National Natural Science Foundation of Shanghai,China(Grant No.19ZR1464600).
文摘Bismuth titanate (Bi_(4)Ti_(3)O_(12),BIT)piezoelectric materials have attracted increasing attention due to their high-temperature applications.However,it is quite challenging to simultaneously achieve outstanding piezoelectric properties and high Curie temperature in BIT-based systems.In this study,oxygen vacancy defects tailoring strategy was utilized to solve this problem,excellent piezoelectric coefficient(32.1 pC/N),and ultrahigh Curie temperature(659℃)are gotten in Bi_(4)Ti_(3)-x(Mn_(1/3)Nb_(2/3))xO_(12)(BTMN)ceramics,which are among the top values in the BIT-based ceramics.More importantly,the(Mn_(1/3)Nb_(2/3))(4+d)+complex-ion modified Bi_(4)Ti_(3)O_(12)-based ceramics are characterized with excellent piezoelectric stability up to 500℃(d33>30.0 pC/N at 500℃))and significantly reduced conductivity(only~10^(-7)U-1 cm^(-1)at 500℃).Moreover,enhanced ferroelectricity and good dielectric stability were also obtained.The better comprehensive properties can be ascribed to two aspects.First,the concentration of oxygen vacancy defects is obviously reduced,and their distribution is effectively controlled in BITMN ceramics.Second,the introduction of(Mn_(1/3)Nb_(2/3))^((4+δ)+)complex-ion gives rise to the antiphase boundaries and massive ferroelectric domain walls.This works not only reveal the high potential of BITMN ceramics for high-temperature piezoelectric applications but also deepen the understanding of the structure-properties relationship in BIT-based materials.
基金supported by the National Natural Science Foundation of China(21975110,21972058 and 22102064)the financial support from Taishan Youth Scholar Program of Shandong Province。
文摘The low separation/migration efficiency is a major obstacle that limits the practical application of semiconductor-photocatalysts. Constructing S-scheme heterojunction is an ideal strategy for providing high photocatalytic activity via accelerating charge separation. Herein, an AgPO/CNcomposite was synthesized by coupling AgPOparticle with CNhollow spheres in-situ via a precipitation method. The S-scheme hete-rojunction between AgPOand CNcould accelerate the charge separation and retain high photoredox ability, which synchronously realized high photocatalytic oxygen production and hexavalent chromium reduction. The optimized Ag3PO4/CNcomposite shows a high oxygen production rate up to 803.31 μmol·g·hand a high conversion(87.9%) of Cr(Ⅵ) to Cr(Ⅲ). In addition, CNhollow spheres affords higher reaction efficiency than that of CNtube, CNbulk and CNsheet, which indicates that the hollow sphere structure can provide more active sites and adsorption sites in the photocatalytic process. This work offers an effective way in developing a dual-function S-scheme heterojunction for clean energy production and environmental protection.
基金The authors gratefully acknowledge the financial supports of the National Natural Science Foundation of China(No.52072110)the Natural Science Foundation of Hebei Province(No.E2018202034).
文摘The high melting point and strong chemical bonding of NbB_(2)pose a great challenge to the preparation of high-density nanostructured NbB_(2)composite coating.Herein,we report a novel,simple,and efficient method to fabricate in-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating by plasma spraying Nb_(2)O_(5)–B_(4)C–Al composite powder,aiming at realizing the higher densification and ultra-fine microstructure of NbB_(2)composite coating.The microstructure and properties of in-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating were studied comparatively with ex-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating(plasma spraying NbB_(2)–NbC–Al_(2)O_(3)composite powder).The reaction mechanism of Nb_(2)O_(5)–B_(4)C–Al composite powder in plasma jet was analyzed in detail.The results showed that the in-situ nanostructured NbB_(2)–NbC–Al_(2)O_(3)composite coating presented a lower porosity and superior performance including higher microhardness,toughness and wear resistance compared to the plasma sprayed ex-situ NbB_(2)–NbC–Al_(2)O_(3)coating and other boride composite coatings.Densification of the in-situ NbB_(2)–NbC–Al_(2)O_(3)coating was attributed to the low melting point of Nb_(2)O_(5)–B_(4)C–Al composite powder and the exothermic effect of in-situ reaction.The superior performance was ascribed to the density improvement and the strengthening and toughening effect of the nanosized phases.The in-situ reaction path could be expressed as:Nb_(2)O_(5)+Al®Nb+Al_(2)O_(3),and Nb+B_(4)C®NbB_(2)+NbC.
