Photocatalytic overall pure water splitting is a promising method for generating green hydrogen energy under mild conditions.However,this process is often hindered by sluggish electron-hole separation and transport.To...Photocatalytic overall pure water splitting is a promising method for generating green hydrogen energy under mild conditions.However,this process is often hindered by sluggish electron-hole separation and transport.To address this,a step-scheme(S-scheme)B-doped N-deficient C_(3)N_(4)/O-doped C_(3)N_(5)(BN-C_(3)N_(4)/O-C_(3)N_(5))heterojunction with interfacial B-O bonds has been constructed.Utilizing Pt and Co(OH)_(2) as co-catalysts,BN-C_(3)N_(4)/O-C_(3)N_(5) S-scheme heterojunction demonstrates significantly enhanced photocatalytic activity for overall pure water splitting under visible light,achieving H_(2) and O_(2) evolution rates of 40.12 and 19.62μmol/h,respectively.Systematic characterizations and experiments revealed the performance-enhancing effects of the enhanced built-in electric field and the interfacial B-O bonding.Firstly,the strengthened built-in electric field provides sufficient force for rapid interfacial electron transport.Secondly,by reducing the transport energy barrier and transfer distance,the interfacial B-O bonds facilitate rapid recombination of electrons and holes with relatively low redox potential via the S-scheme charge-transfer route,leaving the high-potential electrons and holes available for H^(+)reduction and OH^(-)oxidation reactions.Overall,the photocatalytic efficiency of BN-C_(3)N_(4)/O-C_(3)N_(5) S-scheme heterojunction was significantly improved,making it a promising approach for green hydrogen production through overall pure water splitting.展开更多
Si-B-O-N powder without B-O bonds synthesized by polymeric precursor were hot-pressed into ceramics at different tempera-tures. The variations of microstructure and mechanical properties of Si-B-O-N ceramics have been...Si-B-O-N powder without B-O bonds synthesized by polymeric precursor were hot-pressed into ceramics at different tempera-tures. The variations of microstructure and mechanical properties of Si-B-O-N ceramics have been investigated. Crystallization of Si-B-O-N ceramics occurred at about 1400癈. Density, elastic modulus, and flexural strength of the ceramics increased with the increasing sintering temperatures, and reached to their maximum values at 1600癈. By contrast, hardness and frac-ture toughness of the ceramics monotonically changed with increasing sintering temperatures. Hardness decreased, while the fracture toughness increased. The principal toughening mechanisms including crack deflection, crack bridging and plate grain pulling-out effects are discussed展开更多
Thermal softening is an inevitable process in the physical network.Polyurethane(PU),a typical commercial material,is constructed by physical networks,which undergoes the serious thermal decay on mechanical properties ...Thermal softening is an inevitable process in the physical network.Polyurethane(PU),a typical commercial material,is constructed by physical networks,which undergoes the serious thermal decay on mechanical properties at high temperature.Herein,a physically cross-linked PU with a unique thermal stiffening behavior has been developed by incorporating B–N coordination with reversible B–O bonds.The B–N coordination can significantly improve the mechanical properties of the PU.The reversible B–O bonds(temperature dependent reversible transformation between B–OH and B–O–B)are conducive to constructing more multicoordination macromolecular crosslinking points and more stable B–N coordination bonds at high temperature,endowing the PU with the special thermal stiffening behavior for the first time.Such thermal stiffening behavior compensates for the bond breakage and the network destruction caused by heat,significantly expands the rubbery plateau and delays the entire chain motion of the thermoplastic PU.As a result,the terminal flow occurs at a higher temperature up to 200°C.The modulus retention ratio of the materials is up to 87%even at 145oC,which is much higher than that of the existing PU elastomer with the physical network and even some covalent cross-link PU.Simultaneously,the physical network ensures the recyclability of the PU,and the thermal stiffening behavior is still obtained in recycled PU.This work provides a simple strategy to impart thermal stiffening behavior to the physically crosslinked PU,thereby significantly extending the operating temperature range of thermoplastic PU,which can potentially expand the scopes of PU in applications under harsh conditions.展开更多
实验建立了高效液相色谱法检测丹田降脂丸中23-乙酰泽泻醇B等3种成分含量的测定方法。Capcell Pak UG C_(18)色谱柱分离;检测波长:葡糖苷、23-乙酰泽泻醇B和淫羊藿苷检测波长分别设定为319nm、208nm和271nm;柱温:28℃;进样体积:10μL;...实验建立了高效液相色谱法检测丹田降脂丸中23-乙酰泽泻醇B等3种成分含量的测定方法。Capcell Pak UG C_(18)色谱柱分离;检测波长:葡糖苷、23-乙酰泽泻醇B和淫羊藿苷检测波长分别设定为319nm、208nm和271nm;柱温:28℃;进样体积:10μL;以乙腈为流动相A,1.0%磷酸溶液为流动相B,梯度洗脱,洗脱方法:0~5min 13%A,5~15min 13%~45%A,15~24min 45%~86%A,24~30min 86%A,30~31min 13%A,30~35min 13%A;外标法定量检测。结果表明,葡糖苷、23-乙酰泽泻醇B和淫羊藿苷在0.1896~18.96、0.0983~9.83和0.0981~9.81μg/mL范围内线性良好;平均回收率分别为99.83%、99.46%和99.14%;精密度和重复性RSD(n=6)均在5.0%以内;供试品溶液在24h内稳定。该方法检测时间短、操作简单,可以用于丹田降脂丸的质量控制。展开更多
基金supported by the National Natural Science Foundation of China(No.62004143)the Key R&D Program of Hubei Province(No.2022BAA084)the Major Project of Natural Science Foundation of Jiangsu Universities,China(No.23KJA150010)。
文摘Photocatalytic overall pure water splitting is a promising method for generating green hydrogen energy under mild conditions.However,this process is often hindered by sluggish electron-hole separation and transport.To address this,a step-scheme(S-scheme)B-doped N-deficient C_(3)N_(4)/O-doped C_(3)N_(5)(BN-C_(3)N_(4)/O-C_(3)N_(5))heterojunction with interfacial B-O bonds has been constructed.Utilizing Pt and Co(OH)_(2) as co-catalysts,BN-C_(3)N_(4)/O-C_(3)N_(5) S-scheme heterojunction demonstrates significantly enhanced photocatalytic activity for overall pure water splitting under visible light,achieving H_(2) and O_(2) evolution rates of 40.12 and 19.62μmol/h,respectively.Systematic characterizations and experiments revealed the performance-enhancing effects of the enhanced built-in electric field and the interfacial B-O bonding.Firstly,the strengthened built-in electric field provides sufficient force for rapid interfacial electron transport.Secondly,by reducing the transport energy barrier and transfer distance,the interfacial B-O bonds facilitate rapid recombination of electrons and holes with relatively low redox potential via the S-scheme charge-transfer route,leaving the high-potential electrons and holes available for H^(+)reduction and OH^(-)oxidation reactions.Overall,the photocatalytic efficiency of BN-C_(3)N_(4)/O-C_(3)N_(5) S-scheme heterojunction was significantly improved,making it a promising approach for green hydrogen production through overall pure water splitting.
基金This research is supported by the National Natural Science Foundation of China, under grant No. 50072002.
文摘Si-B-O-N powder without B-O bonds synthesized by polymeric precursor were hot-pressed into ceramics at different tempera-tures. The variations of microstructure and mechanical properties of Si-B-O-N ceramics have been investigated. Crystallization of Si-B-O-N ceramics occurred at about 1400癈. Density, elastic modulus, and flexural strength of the ceramics increased with the increasing sintering temperatures, and reached to their maximum values at 1600癈. By contrast, hardness and frac-ture toughness of the ceramics monotonically changed with increasing sintering temperatures. Hardness decreased, while the fracture toughness increased. The principal toughening mechanisms including crack deflection, crack bridging and plate grain pulling-out effects are discussed
基金supported by the National Natural Science Foundation of China(52203064 and 52373061)the China Postdoctoral Science Foundation(2023M732415)+1 种基金the Fundamental Research Funds for the Central Universities(2022SCU12011)the State Key Laboratory of Polymer Materials Engineering,Sichuan University。
文摘Thermal softening is an inevitable process in the physical network.Polyurethane(PU),a typical commercial material,is constructed by physical networks,which undergoes the serious thermal decay on mechanical properties at high temperature.Herein,a physically cross-linked PU with a unique thermal stiffening behavior has been developed by incorporating B–N coordination with reversible B–O bonds.The B–N coordination can significantly improve the mechanical properties of the PU.The reversible B–O bonds(temperature dependent reversible transformation between B–OH and B–O–B)are conducive to constructing more multicoordination macromolecular crosslinking points and more stable B–N coordination bonds at high temperature,endowing the PU with the special thermal stiffening behavior for the first time.Such thermal stiffening behavior compensates for the bond breakage and the network destruction caused by heat,significantly expands the rubbery plateau and delays the entire chain motion of the thermoplastic PU.As a result,the terminal flow occurs at a higher temperature up to 200°C.The modulus retention ratio of the materials is up to 87%even at 145oC,which is much higher than that of the existing PU elastomer with the physical network and even some covalent cross-link PU.Simultaneously,the physical network ensures the recyclability of the PU,and the thermal stiffening behavior is still obtained in recycled PU.This work provides a simple strategy to impart thermal stiffening behavior to the physically crosslinked PU,thereby significantly extending the operating temperature range of thermoplastic PU,which can potentially expand the scopes of PU in applications under harsh conditions.
文摘实验建立了高效液相色谱法检测丹田降脂丸中23-乙酰泽泻醇B等3种成分含量的测定方法。Capcell Pak UG C_(18)色谱柱分离;检测波长:葡糖苷、23-乙酰泽泻醇B和淫羊藿苷检测波长分别设定为319nm、208nm和271nm;柱温:28℃;进样体积:10μL;以乙腈为流动相A,1.0%磷酸溶液为流动相B,梯度洗脱,洗脱方法:0~5min 13%A,5~15min 13%~45%A,15~24min 45%~86%A,24~30min 86%A,30~31min 13%A,30~35min 13%A;外标法定量检测。结果表明,葡糖苷、23-乙酰泽泻醇B和淫羊藿苷在0.1896~18.96、0.0983~9.83和0.0981~9.81μg/mL范围内线性良好;平均回收率分别为99.83%、99.46%和99.14%;精密度和重复性RSD(n=6)均在5.0%以内;供试品溶液在24h内稳定。该方法检测时间短、操作简单,可以用于丹田降脂丸的质量控制。
