Energy band structure and interfacial compatibility of heterojunctions are crucial for photocatalysts in promoting photogene rated charge separation and transfer.Here,a combined strategy of vacancy engineering and qua...Energy band structure and interfacial compatibility of heterojunctions are crucial for photocatalysts in promoting photogene rated charge separation and transfer.Here,a combined strategy of vacancy engineering and quantum effect via a facile phosphating process is reported,for the first time,to modulate the energy band structure and the interface of Zn_(x)Cd_(1-x)S/CoP quantum dots(ZCS_(v)/CoP QDs)heterojunction.The combined experimental and theoretical investigation revealed that phosphating process transformed CoO_(x) QDs to CoP QDs,and more importantly,generated considerable amount of sulfur vacancies in ZCS_(v).As a result,a TypeⅡZCS_(v)/CoP QDs heterojunction with compatible interfaces was constructed via in-situ generated P-Zn,P-Cd and S-Co bonds,which facilitated the separation and transfer of the photogenerated charge and thus resulted in a high ability towards hydrogen evolution under visible light(17.53 mmol g^(-1) h^(-1)).This work provides an effective and adaptable strategy to modulate band structure and interfacial compatibility of heterojunctions via vacancy engineering and quantum effect.展开更多
Several samples of manganese oxides La(1-x)2/3Ca1/3MnO3 (V-LCMO) and (La0.7-xY0.3)2/3Ca1/3MnO3 (x<0.15) (V-LYCMO) with vacancies at La-site (La-vacancy) were prepared by solid-state reaction method. The X-ray diffr...Several samples of manganese oxides La(1-x)2/3Ca1/3MnO3 (V-LCMO) and (La0.7-xY0.3)2/3Ca1/3MnO3 (x<0.15) (V-LYCMO) with vacancies at La-site (La-vacancy) were prepared by solid-state reaction method. The X-ray diffraction(XRD) patterns refined by Rietveld confirm that these compounds exhibit single phase structure with orthorhombic symmetry (Pnma). The lattice parameters, Mn—O bond length and Mn—O—Mn bond angle vary with La-vacancy concentration, as an indication of the occurrence of the local Jahn-Teller effect. The measurement result of V-LCMO compounds shows that the maximum magnetoresistance(MR) is about 220% at TIM=268 K and La-vacancy content x=0.04. For V-LYCMO compounds, there exists metal-insulator transition at about 50 K, and a very large MR (over 106%) is observed at the temperature ranging from 40 K to 50 K.展开更多
Cu-based catalysts are widely employed for CO_(2) hydrogenation to methanol,which is expected as a promising process to achieving carbon neutrality.However,most Cu-based catalysts still suffer from low methanol yield ...Cu-based catalysts are widely employed for CO_(2) hydrogenation to methanol,which is expected as a promising process to achieving carbon neutrality.However,most Cu-based catalysts still suffer from low methanol yield with a passable CO_(2) conversion and lack insight into its reaction mechanism for guiding the design of catalysts.In this work,Cu^(+)/CeZrO_(x) interfaces are engineered by employing a series of ceria-zirconia solid solution catalysts with various Ce/Zr ratios,forming a Cu^(+)-O_(v)-Ce^(3+)structure where Cu^(+)atoms are bonded to the oxygen vacancies(O_(v))of ceria.Compared to Cu/CeO_(2) and Cu/ZrO_(2),the optimized catalyst(i.e.,Cu_(0.3)Ce_(0.3)Zr_(0.7))exhibits a much higher mass-specific methanol formation rate(192g_(MeOH)/kg_(cat)/h)at 240℃and 3 MPa.Through a series of in-situ and ex-situ characterization,it is revealed that oxygen vacancies in solid solutions can effectively assist the activation of CO_(2) and tune the electronic state of copper to promote the formation of Cu^(+)/CeZrO_(x) interfaces,which stabilizes the key*CO intermediate,inhibits its desorption and facilitates its further hydrogenation to methanol via the reverse watergas-shift(RWGS)+CO-Hydro pathway.Therefore,the concentration of*CO or the apparent Cu^(+)/(Cu^(+)+Cu^(0))ratio could be employed as a quantitative descriptor of the methanol formation rate.This work is expected to give a deep insight into the mechanism of metal/support interfaces in CO_(2) hydrogenation to methanol,offering an effective strategy to develop new catalysts with high performance.展开更多
Samples of manganese oxides La（1-x）2/3Ca1/3MnO3（x 〈 0.10） with Lavacancy were prepared by standard solid-state reaction method. All the samples are single phase, with orthorhombic symmetry （Pnma ）, analyzed by ...Samples of manganese oxides La（1-x）2/3Ca1/3MnO3（x 〈 0.10） with Lavacancy were prepared by standard solid-state reaction method. All the samples are single phase, with orthorhombic symmetry （Pnma ）, analyzed by XRD and with Rietveld Refinement. The effect of different La-site vacancies concentration on electronic transport of La（1-x）2/3Ca1/3MnO3 was investigated. The insulator-metal transition temperature （about 267 K） nearly remains unchanged with the increase of vacancy concentration, which indicates that small La-vacancy does not destroy the double exchange interaction. But the electronic resistance increases and MR value decreases with La-vacancy content x 〉 0.04. The maximum of the MR value （8 T） is about 220% at transition temperature （TMI）.展开更多
Z-scheme semiconductors are a promising class of photocatalysts for hydrogen generation.In this work,Z-scheme semiconductors composed of WO3-x quantum dots supported on TiO2（WO3-xQDS/TiO2） were fabricated by solvoth...Z-scheme semiconductors are a promising class of photocatalysts for hydrogen generation.In this work,Z-scheme semiconductors composed of WO3-x quantum dots supported on TiO2（WO3-xQDS/TiO2） were fabricated by solvothermal and hydrogen-reduction methods.Characterization by transmission electron microscopy and X-ray diffraction indicated that the amount and size of the WO3-x QDs could be tuned by modulating the addition of the W precursor.Evidence from X-ray photoelectron spectroscopy and photoluminescence spectroscopy suggested that the hydrogen reduction of the composite induced the formation of oxygen vacancy（W^5＋/Vo） defects in WO3.These defects led to ohmic contact between WO3-x and TiO2,which altered the charge-transfer pathway from type Ⅱ heterojunction to Z-scheme,and maintained the highly reductive and oxidative ability of TiO2 and WO3-x,respectively.Therefore,the Z-scheme sample showed 1.3-fold higher photoactivity than pure TiO2 in hydrogen generation.These results suggest that the formation of W^5＋/Vo defects at the interface is highly beneficial for the fabrication of Z-scheme photocatalysts.展开更多
Spinel LiNi_(0.5-x)Mn_(1.5+x)O_(4)(LNMO)has attracted intensive interest for lithium-ion battery due to its high voltage and high energy density.However,severe capacity fade attributed to unstable surface structure ha...Spinel LiNi_(0.5-x)Mn_(1.5+x)O_(4)(LNMO)has attracted intensive interest for lithium-ion battery due to its high voltage and high energy density.However,severe capacity fade attributed to unstable surface structure has hampered its commercialization.Oxygen vacancies(OVs)tend to occur in the surface of the material and lead to surface structure reconstruction,which deteriorates the battery performance during electrochemical cycling.Here,we utilize high-temperature-shock(HTS)method to synthesize LNMO materials with fewer surface OVs.Rapid calcination drives lower surface OVs concentration,reducing the content of Mn^(3+)and surface reconstruction layers,which is beneficial to obtain a stable crystal structure.The LNMO material synthesized by HTS method delivers an initial capacity of 127 mAh·g^(-1) at 0.1 C and capacity retention of 81.6%after 300 cycles at 1 C,and exhibits excellent performance at low temperature.展开更多
基金financially supported by the Taishan Scholar Program of Shandong Province(ts201712046)the Key Research and Development Programme of Shandong Province(2019JZZY010905)+2 种基金the Natural Science Foundation of Shandong Province(ZR2020QB132)the Liaoning BaiQianWan Talents Programthe Royal Society and the Newton Fund(NAF\R1\191294)。
文摘Energy band structure and interfacial compatibility of heterojunctions are crucial for photocatalysts in promoting photogene rated charge separation and transfer.Here,a combined strategy of vacancy engineering and quantum effect via a facile phosphating process is reported,for the first time,to modulate the energy band structure and the interface of Zn_(x)Cd_(1-x)S/CoP quantum dots(ZCS_(v)/CoP QDs)heterojunction.The combined experimental and theoretical investigation revealed that phosphating process transformed CoO_(x) QDs to CoP QDs,and more importantly,generated considerable amount of sulfur vacancies in ZCS_(v).As a result,a TypeⅡZCS_(v)/CoP QDs heterojunction with compatible interfaces was constructed via in-situ generated P-Zn,P-Cd and S-Co bonds,which facilitated the separation and transfer of the photogenerated charge and thus resulted in a high ability towards hydrogen evolution under visible light(17.53 mmol g^(-1) h^(-1)).This work provides an effective and adaptable strategy to modulate band structure and interfacial compatibility of heterojunctions via vacancy engineering and quantum effect.
基金Project(0150014) supported by the Natural Science Foundation of Jiangxi Province, China
文摘Several samples of manganese oxides La(1-x)2/3Ca1/3MnO3 (V-LCMO) and (La0.7-xY0.3)2/3Ca1/3MnO3 (x<0.15) (V-LYCMO) with vacancies at La-site (La-vacancy) were prepared by solid-state reaction method. The X-ray diffraction(XRD) patterns refined by Rietveld confirm that these compounds exhibit single phase structure with orthorhombic symmetry (Pnma). The lattice parameters, Mn—O bond length and Mn—O—Mn bond angle vary with La-vacancy concentration, as an indication of the occurrence of the local Jahn-Teller effect. The measurement result of V-LCMO compounds shows that the maximum magnetoresistance(MR) is about 220% at TIM=268 K and La-vacancy content x=0.04. For V-LYCMO compounds, there exists metal-insulator transition at about 50 K, and a very large MR (over 106%) is observed at the temperature ranging from 40 K to 50 K.
基金sponsored by the National Natural Science Foundation of China(21808120,21978148)。
文摘Cu-based catalysts are widely employed for CO_(2) hydrogenation to methanol,which is expected as a promising process to achieving carbon neutrality.However,most Cu-based catalysts still suffer from low methanol yield with a passable CO_(2) conversion and lack insight into its reaction mechanism for guiding the design of catalysts.In this work,Cu^(+)/CeZrO_(x) interfaces are engineered by employing a series of ceria-zirconia solid solution catalysts with various Ce/Zr ratios,forming a Cu^(+)-O_(v)-Ce^(3+)structure where Cu^(+)atoms are bonded to the oxygen vacancies(O_(v))of ceria.Compared to Cu/CeO_(2) and Cu/ZrO_(2),the optimized catalyst(i.e.,Cu_(0.3)Ce_(0.3)Zr_(0.7))exhibits a much higher mass-specific methanol formation rate(192g_(MeOH)/kg_(cat)/h)at 240℃and 3 MPa.Through a series of in-situ and ex-situ characterization,it is revealed that oxygen vacancies in solid solutions can effectively assist the activation of CO_(2) and tune the electronic state of copper to promote the formation of Cu^(+)/CeZrO_(x) interfaces,which stabilizes the key*CO intermediate,inhibits its desorption and facilitates its further hydrogenation to methanol via the reverse watergas-shift(RWGS)+CO-Hydro pathway.Therefore,the concentration of*CO or the apparent Cu^(+)/(Cu^(+)+Cu^(0))ratio could be employed as a quantitative descriptor of the methanol formation rate.This work is expected to give a deep insight into the mechanism of metal/support interfaces in CO_(2) hydrogenation to methanol,offering an effective strategy to develop new catalysts with high performance.
文摘Samples of manganese oxides La（1-x）2/3Ca1/3MnO3（x 〈 0.10） with Lavacancy were prepared by standard solid-state reaction method. All the samples are single phase, with orthorhombic symmetry （Pnma ）, analyzed by XRD and with Rietveld Refinement. The effect of different La-site vacancies concentration on electronic transport of La（1-x）2/3Ca1/3MnO3 was investigated. The insulator-metal transition temperature （about 267 K） nearly remains unchanged with the increase of vacancy concentration, which indicates that small La-vacancy does not destroy the double exchange interaction. But the electronic resistance increases and MR value decreases with La-vacancy content x 〉 0.04. The maximum of the MR value （8 T） is about 220% at transition temperature （TMI）.
基金supported by the National Natural Science Foundation of China (21506156, 21676193)the Tianjin Municipal Natural Science Foundation (15JCZDJC37300, 16JCQNJC05200)~~
文摘Z-scheme semiconductors are a promising class of photocatalysts for hydrogen generation.In this work,Z-scheme semiconductors composed of WO3-x quantum dots supported on TiO2（WO3-xQDS/TiO2） were fabricated by solvothermal and hydrogen-reduction methods.Characterization by transmission electron microscopy and X-ray diffraction indicated that the amount and size of the WO3-x QDs could be tuned by modulating the addition of the W precursor.Evidence from X-ray photoelectron spectroscopy and photoluminescence spectroscopy suggested that the hydrogen reduction of the composite induced the formation of oxygen vacancy（W^5＋/Vo） defects in WO3.These defects led to ohmic contact between WO3-x and TiO2,which altered the charge-transfer pathway from type Ⅱ heterojunction to Z-scheme,and maintained the highly reductive and oxidative ability of TiO2 and WO3-x,respectively.Therefore,the Z-scheme sample showed 1.3-fold higher photoactivity than pure TiO2 in hydrogen generation.These results suggest that the formation of W^5＋/Vo defects at the interface is highly beneficial for the fabrication of Z-scheme photocatalysts.
基金support from the National Natural Science Foundation of China(No.52171219).
文摘Spinel LiNi_(0.5-x)Mn_(1.5+x)O_(4)(LNMO)has attracted intensive interest for lithium-ion battery due to its high voltage and high energy density.However,severe capacity fade attributed to unstable surface structure has hampered its commercialization.Oxygen vacancies(OVs)tend to occur in the surface of the material and lead to surface structure reconstruction,which deteriorates the battery performance during electrochemical cycling.Here,we utilize high-temperature-shock(HTS)method to synthesize LNMO materials with fewer surface OVs.Rapid calcination drives lower surface OVs concentration,reducing the content of Mn^(3+)and surface reconstruction layers,which is beneficial to obtain a stable crystal structure.The LNMO material synthesized by HTS method delivers an initial capacity of 127 mAh·g^(-1) at 0.1 C and capacity retention of 81.6%after 300 cycles at 1 C,and exhibits excellent performance at low temperature.
