Designing a step-scheme(S-scheme)heterojunction photocatalyst with vacancy engineering is a reliable approach to achieve highly efficient photocatalytic H_(2)production activity.Herein,a hollow ZnO/ZnS S-scheme hetero...Designing a step-scheme(S-scheme)heterojunction photocatalyst with vacancy engineering is a reliable approach to achieve highly efficient photocatalytic H_(2)production activity.Herein,a hollow ZnO/ZnS S-scheme heterojunction with O and Zn vacancies(VO,Zn-ZnO/ZnS)is rationally constructed via ion-exchange and calcination treatments.In such a photocatalytic system,the hollow structure combined with the introduction of dual vacancies endows the adequate light absorption.Moreover,the O and Zn vacancies serve as the trapping sites for photo-induced electrons and holes,respectively,which are beneficial for promoting the photo-induced carrier separation.Meanwhile,the S-scheme charge transfer mechanism can not only improve the separation and transfer efficiencies of photo-induced carrier but also retain the strong redox capacity.As expected,the optimized VO,Zn-ZnO/ZnS heterojunction exhibits a superior photocatalytic H_(2) production rate of 160.91 mmol g^(-1)h^(-1),approximately 643.6 times and 214.5 times with respect to that obtained on pure ZnO and ZnS,respectively.Simultaneously,the experimental results and density functional theory calculations disclose that the photo-induced carrier transfer pathway follows the S-scheme heterojunction mechanism and the introduction of O and Zn vacancies reduces the surface reaction barrier.This work provides an innovative strategy of vacancy engineering in S-scheme heterojunction for solar-to-fuel energy conversion.展开更多
In this study,ZnO formation during the dissolution-passivation process of Zn anodes is observed via in situ Raman and optical characterization.The Zn passivation during galvanostatic anodization merely follows the dis...In this study,ZnO formation during the dissolution-passivation process of Zn anodes is observed via in situ Raman and optical characterization.The Zn passivation during galvanostatic anodization merely follows the dissolution-precipitation model,whereas that of potentiodynamic polarization exhibits different behaviors in different potential ranges.Initially,the Zn electrode is gradually covered by a ZnO precipitation film and then undergoes solid-state oxidation at~255 mV.The starting point of solid-state oxidation is well indicated by the abrupt current drop and yellow coloration of the electrode surface.During the pseudo passivation,an intense current oscillation is observed.Further,blink-like color changes between yellow and dark blue are revealed for the first time,implying that the oscillation is caused by the dynamic adsorption and desorption of OH groups.The as-formed ZnOs then experience a dissolution-reformation evolution,during which the crystallinity of the primary ZnO film is improved but the solid-state-formed ZnO layer becomes rich in oxygen vacancies.Eventually,oxide densification is realized,contributing to the Zn passivation.This study provides new insights into the Zn dissolution-passivation behavior,which is critical for the future optimization of Zn batteries.展开更多
2D MXenes are highly attractive for fabricating high-precision gas sensors operated at room temperature(RT)due to their high surface-to-volume ratio.However,the limited selectivity and low sensitivity are still long-s...2D MXenes are highly attractive for fabricating high-precision gas sensors operated at room temperature(RT)due to their high surface-to-volume ratio.However,the limited selectivity and low sensitivity are still long-standing challenges for their further applications.Herein,the self-assembly of 0D-2D heterostructure for highly sensitive NO_(2) detection was achieved by integrating ZnO nanoparticles on Ti_(3)C_(2)Tx MXene-derived TiO_(2) nanosheets(designated as ZnO@MTiO_(2)).ZnO nanoparticles can not only act as spacers to prevent the restacking of MTiO_(2) nanosheets and ensure effective transfer for gas molecules,but also enhance the sensitivity of the sensor the through trapping effect on electrons.Meanwhile,MTiO_(2) nanosheets facilitate gas diffusion for rapid sensor response.Benefiting from the synergistic effect of individual components,the ZnO@MTiO_(2)0D-2D heterostructure-based sensors revealed remarkable sensitivity and excellent selectivity to low concentration NO_(2) at RT.This work may facilitate the sensing application of MXene derivative and provide a new avenue for the development of high-performance gas sensors in safety assurance and environmental monitoring.展开更多
Light confinement induced by spontaneous near-surface resonance is inherently determined by the location and geometry of metallic nanostructures(NSs),offering a facile and effective approach to break through the limit...Light confinement induced by spontaneous near-surface resonance is inherently determined by the location and geometry of metallic nanostructures(NSs),offering a facile and effective approach to break through the limitation of the light-mater interaction within the photoactive layers.Here,we demonstrate high-performance Al NS/ZnO quantum dots(Al/ZnO) heterostructure UV photodetectors with controllable morphologies of the self-assembled Al NSs.The Al/ZnO heterostructures exhibit a superior light utilization than the ZnO/Al heterostructures,and a strong morphological dependence of the Al NSs on the optical properties of the heterostructures.The inter-diffusion of Al atoms into ZnO matrixes is of a great benefit for the carrier transportation.Consequently,the optimal photocurrent of the Al/ZnO heterostructure photodetectors is significantly increased by 275 times to ~1.065 mA compared to that of the pristine ZnO device,and an outstanding photoresponsivity of 11.98 A W-1 is correspondingly achieved under 6.9 MW cm-2 UV light illumination at 10 V bias.In addition,a relatively fast response is similarly witnessed with the Al/ZnO devices,paving a path to fabricate the high-performance UV photodetectors for applications.展开更多
ZnO-MxOy heterostructures (M=Co, Mn, Ni, or In) are fabricated via hydrothermal synthesis method. X-ray diffraction and Fourier-transform infrared spectroscopy analyses endorse the successive formation of the various ...ZnO-MxOy heterostructures (M=Co, Mn, Ni, or In) are fabricated via hydrothermal synthesis method. X-ray diffraction and Fourier-transform infrared spectroscopy analyses endorse the successive formation of the various heterostructures. Field Emission Scanning electron microscope and Brunauer-Emmett-Teller (BET) surface area studies confirm the porous nature of the heterostructures obtained. The band gaps of various heterostructures are calculated that, 3.1, 2.71, 2.64, and 2.19 eV for ZnO-NiO, ZnO-In2O3, ZnO-Co3O4, and ZnO-MnO2, respectively. The photocatalytic activities of the fabricated heterostructures are investigated through the degradation of phenol under direct sunlight irradiation. The results show that the photocatalytic activity is affected by the conduction band (CB) and valence band (VB) positions rather than surface area of ZnO-MxOy heterostructure nanocomposites.展开更多
First-principles calculations have been performed to clarify the differences of the electronic structures of Ga-doped ZnO and ZnS. Results show the local density approximation and local density approximation＋U calcul...First-principles calculations have been performed to clarify the differences of the electronic structures of Ga-doped ZnO and ZnS. Results show the local density approximation and local density approximation＋U calculations are in good qualitative agreement with each other. After doping, impurity states appear near the Fermi level in both ZnO and ZnS cases. When ZnO is doped, the impurity states are delocalized in the whole conduction band. On the contrary, when ZnS is doped, though the p state of Ga is also delocalized, the s state is localized near the Fermi level. Partial charge density distributions of the frontier orbital show the same information. After an exchange of the crystal structures of ZnO and ZnS, results remain unchanged. The localized Ga s state accounts for the bad electrical properties of Ga-doped ZnS.展开更多
文摘Designing a step-scheme(S-scheme)heterojunction photocatalyst with vacancy engineering is a reliable approach to achieve highly efficient photocatalytic H_(2)production activity.Herein,a hollow ZnO/ZnS S-scheme heterojunction with O and Zn vacancies(VO,Zn-ZnO/ZnS)is rationally constructed via ion-exchange and calcination treatments.In such a photocatalytic system,the hollow structure combined with the introduction of dual vacancies endows the adequate light absorption.Moreover,the O and Zn vacancies serve as the trapping sites for photo-induced electrons and holes,respectively,which are beneficial for promoting the photo-induced carrier separation.Meanwhile,the S-scheme charge transfer mechanism can not only improve the separation and transfer efficiencies of photo-induced carrier but also retain the strong redox capacity.As expected,the optimized VO,Zn-ZnO/ZnS heterojunction exhibits a superior photocatalytic H_(2) production rate of 160.91 mmol g^(-1)h^(-1),approximately 643.6 times and 214.5 times with respect to that obtained on pure ZnO and ZnS,respectively.Simultaneously,the experimental results and density functional theory calculations disclose that the photo-induced carrier transfer pathway follows the S-scheme heterojunction mechanism and the introduction of O and Zn vacancies reduces the surface reaction barrier.This work provides an innovative strategy of vacancy engineering in S-scheme heterojunction for solar-to-fuel energy conversion.
基金supported by the Research and Development Initiative for Scientific Innovation of New Generation Batteries(RISING)Projects,RISING2[JPNP16001]and RISING3[JPNP21006],commissioned by of the New Energy and Industrial Technology Development Organization(NEDO),Japanthe State Scholarship Fund of the China Scholarship Council[No.201906230294]for their support
文摘In this study,ZnO formation during the dissolution-passivation process of Zn anodes is observed via in situ Raman and optical characterization.The Zn passivation during galvanostatic anodization merely follows the dissolution-precipitation model,whereas that of potentiodynamic polarization exhibits different behaviors in different potential ranges.Initially,the Zn electrode is gradually covered by a ZnO precipitation film and then undergoes solid-state oxidation at~255 mV.The starting point of solid-state oxidation is well indicated by the abrupt current drop and yellow coloration of the electrode surface.During the pseudo passivation,an intense current oscillation is observed.Further,blink-like color changes between yellow and dark blue are revealed for the first time,implying that the oscillation is caused by the dynamic adsorption and desorption of OH groups.The as-formed ZnOs then experience a dissolution-reformation evolution,during which the crystallinity of the primary ZnO film is improved but the solid-state-formed ZnO layer becomes rich in oxygen vacancies.Eventually,oxide densification is realized,contributing to the Zn passivation.This study provides new insights into the Zn dissolution-passivation behavior,which is critical for the future optimization of Zn batteries.
基金supported by the National Natural Science Foundation of China(No.52103308)the Natural Science Foundation of Jiangsu Province of China(No.BK20210826)+4 种基金Outstanding Youth Foundation of Jiangsu Province of China(No.BK20211548)National Key Research and Development Program of China(No.2017YFE0115900)Innovative Science and Technology Platform Project of Cooperation between Yangzhou City and Yangzhou University(No.YZ2020266)Lvyang Jinfeng Plan for Excellent Doctor of Yangzhou City,Special Funds for Self-Made Experimental Equipment of Yangzhou Universitythe Doctor of Suzhou University Scientific Research Foundation Project(No.2022BSK003).
文摘2D MXenes are highly attractive for fabricating high-precision gas sensors operated at room temperature(RT)due to their high surface-to-volume ratio.However,the limited selectivity and low sensitivity are still long-standing challenges for their further applications.Herein,the self-assembly of 0D-2D heterostructure for highly sensitive NO_(2) detection was achieved by integrating ZnO nanoparticles on Ti_(3)C_(2)Tx MXene-derived TiO_(2) nanosheets(designated as ZnO@MTiO_(2)).ZnO nanoparticles can not only act as spacers to prevent the restacking of MTiO_(2) nanosheets and ensure effective transfer for gas molecules,but also enhance the sensitivity of the sensor the through trapping effect on electrons.Meanwhile,MTiO_(2) nanosheets facilitate gas diffusion for rapid sensor response.Benefiting from the synergistic effect of individual components,the ZnO@MTiO_(2)0D-2D heterostructure-based sensors revealed remarkable sensitivity and excellent selectivity to low concentration NO_(2) at RT.This work may facilitate the sensing application of MXene derivative and provide a new avenue for the development of high-performance gas sensors in safety assurance and environmental monitoring.
基金the National Natural Science Foundation of China(Grant Nos.61705070 and 61974052)China Postdoctoral Science Foundation(Grant Nos.2019M662594)National Research Foundation of Korea(NRF)Grant funded by the Korean Government(MSIP)(Nos.NRF2019R1A2C4069438 and NRF2018R1A6A1A03025242)。
文摘Light confinement induced by spontaneous near-surface resonance is inherently determined by the location and geometry of metallic nanostructures(NSs),offering a facile and effective approach to break through the limitation of the light-mater interaction within the photoactive layers.Here,we demonstrate high-performance Al NS/ZnO quantum dots(Al/ZnO) heterostructure UV photodetectors with controllable morphologies of the self-assembled Al NSs.The Al/ZnO heterostructures exhibit a superior light utilization than the ZnO/Al heterostructures,and a strong morphological dependence of the Al NSs on the optical properties of the heterostructures.The inter-diffusion of Al atoms into ZnO matrixes is of a great benefit for the carrier transportation.Consequently,the optimal photocurrent of the Al/ZnO heterostructure photodetectors is significantly increased by 275 times to ~1.065 mA compared to that of the pristine ZnO device,and an outstanding photoresponsivity of 11.98 A W-1 is correspondingly achieved under 6.9 MW cm-2 UV light illumination at 10 V bias.In addition,a relatively fast response is similarly witnessed with the Al/ZnO devices,paving a path to fabricate the high-performance UV photodetectors for applications.
文摘ZnO-MxOy heterostructures (M=Co, Mn, Ni, or In) are fabricated via hydrothermal synthesis method. X-ray diffraction and Fourier-transform infrared spectroscopy analyses endorse the successive formation of the various heterostructures. Field Emission Scanning electron microscope and Brunauer-Emmett-Teller (BET) surface area studies confirm the porous nature of the heterostructures obtained. The band gaps of various heterostructures are calculated that, 3.1, 2.71, 2.64, and 2.19 eV for ZnO-NiO, ZnO-In2O3, ZnO-Co3O4, and ZnO-MnO2, respectively. The photocatalytic activities of the fabricated heterostructures are investigated through the degradation of phenol under direct sunlight irradiation. The results show that the photocatalytic activity is affected by the conduction band (CB) and valence band (VB) positions rather than surface area of ZnO-MxOy heterostructure nanocomposites.
文摘First-principles calculations have been performed to clarify the differences of the electronic structures of Ga-doped ZnO and ZnS. Results show the local density approximation and local density approximation＋U calculations are in good qualitative agreement with each other. After doping, impurity states appear near the Fermi level in both ZnO and ZnS cases. When ZnO is doped, the impurity states are delocalized in the whole conduction band. On the contrary, when ZnS is doped, though the p state of Ga is also delocalized, the s state is localized near the Fermi level. Partial charge density distributions of the frontier orbital show the same information. After an exchange of the crystal structures of ZnO and ZnS, results remain unchanged. The localized Ga s state accounts for the bad electrical properties of Ga-doped ZnS.
