This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decompos...This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters ; their pseudo-active energy Ea; and that the top-temperature of decom-position Tp decreases gently in the scope of micron-sized diameter, but decreases sharply when the average di-ameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reac-tions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both Ea and Tp to decline sharply with the decrease of the average diameter of nano-particles.展开更多
Although photocatalytic water splitting has excellent potential for converting solar energy into chemical energy,the challenging charge separation process and sluggish surface catalytic reactions significantly limit p...Although photocatalytic water splitting has excellent potential for converting solar energy into chemical energy,the challenging charge separation process and sluggish surface catalytic reactions significantly limit progress in solar energy conversion using semiconductor photocatalysts.Herein,we demonstrate a feasible strategy involving the surface assembly of cobalt oxide species(CoO_(x))on a visible-light-responsive Cd_(0.9)Zn_(0.1)S(CZS)photocatalyst to fabricate a hierarchical CZS@CoO_(x) heterostructure.The unique hierarchical structure effectively accelerates the directional transfer of photogenerated charges,reducing charge recombination through the smooth interfacial heterojunction between CZS and CoO_(x),as evidenced by photoluminescence(PL)spectroscopy and various electrochemical characterizations.The surface cobalt species on the CZS material also act as efficient cocatalysts for photocatalytic hydrogen production,with activity even higher than that of noble metals.The well-defined CZS@CoO_(x) heterostructure not only enhances the interfacial separation of photoinduced charges,but also improves surface catalytic reactions.This leads to superior photocatalytic performances,with an apparent quantum efficiency of 20%at 420 nm for visible-light-driven hydrogen generation,which is one of the highest quantum efficiencies measured among noble-metal-free photocatalysts.Our work presents a potential pathway for controlling complex charge separation and catalytic reaction processes in photocatalysis,guiding the practical development of artificial photocatalysts for successful transformation of solar to chemical energy.展开更多
Cesium lead halide perovskite nanocrystals(NCs)have attracted unprecedented attention owing to their compelling properties for optoelectronic applications.Compared with the classical hot-injection method,the roomtempe...Cesium lead halide perovskite nanocrystals(NCs)have attracted unprecedented attention owing to their compelling properties for optoelectronic applications.Compared with the classical hot-injection method,the roomtemperature(RT)synthetic strategy is more facile and tender,but it is hard to obtain stable CsPbI3 NCs and it usually uses polar solvents that sometimes reduce the stability and properties of NCs.Here,we reported a simple approach to synthesize highly efficient and stable CsPbI3 as well as other colortunable CsPbX3 NCs with high quantum efficiency at room temperature via an anion exchange at the water-oil interface,in which the as-synthesized pristine CsPbBr3 NCs in toluene were treated in aqueous solutions of HX(X=Cl,Br,and I)and protonated oleylamine(OAm)acted as a carrier.The synthesized CsPbI3 NCs had an emission at 680 nm and even showed excellent colloidal stability after being stored for 32 d.The high efficiency and stability of the obtained CsPbX3 NCs were ascribed to the facts that:(ⅰ)the polar reagents were almost removed from the surface of NCs;(ⅱ)the defect-related nonradiative recombination was suppressed efficiently by surface passivation.展开更多
文摘This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters ; their pseudo-active energy Ea; and that the top-temperature of decom-position Tp decreases gently in the scope of micron-sized diameter, but decreases sharply when the average di-ameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reac-tions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both Ea and Tp to decline sharply with the decrease of the average diameter of nano-particles.
文摘Although photocatalytic water splitting has excellent potential for converting solar energy into chemical energy,the challenging charge separation process and sluggish surface catalytic reactions significantly limit progress in solar energy conversion using semiconductor photocatalysts.Herein,we demonstrate a feasible strategy involving the surface assembly of cobalt oxide species(CoO_(x))on a visible-light-responsive Cd_(0.9)Zn_(0.1)S(CZS)photocatalyst to fabricate a hierarchical CZS@CoO_(x) heterostructure.The unique hierarchical structure effectively accelerates the directional transfer of photogenerated charges,reducing charge recombination through the smooth interfacial heterojunction between CZS and CoO_(x),as evidenced by photoluminescence(PL)spectroscopy and various electrochemical characterizations.The surface cobalt species on the CZS material also act as efficient cocatalysts for photocatalytic hydrogen production,with activity even higher than that of noble metals.The well-defined CZS@CoO_(x) heterostructure not only enhances the interfacial separation of photoinduced charges,but also improves surface catalytic reactions.This leads to superior photocatalytic performances,with an apparent quantum efficiency of 20%at 420 nm for visible-light-driven hydrogen generation,which is one of the highest quantum efficiencies measured among noble-metal-free photocatalysts.Our work presents a potential pathway for controlling complex charge separation and catalytic reaction processes in photocatalysis,guiding the practical development of artificial photocatalysts for successful transformation of solar to chemical energy.
基金supported by the Natural Science Foundation of Fujian Province(2019J05041)the Education Foundation of Fujian Province(JAT170021)the“Double-First Class”Foundation of Materials and Intelligent Manufacturing Discipline of Xiamen University。
文摘Cesium lead halide perovskite nanocrystals(NCs)have attracted unprecedented attention owing to their compelling properties for optoelectronic applications.Compared with the classical hot-injection method,the roomtemperature(RT)synthetic strategy is more facile and tender,but it is hard to obtain stable CsPbI3 NCs and it usually uses polar solvents that sometimes reduce the stability and properties of NCs.Here,we reported a simple approach to synthesize highly efficient and stable CsPbI3 as well as other colortunable CsPbX3 NCs with high quantum efficiency at room temperature via an anion exchange at the water-oil interface,in which the as-synthesized pristine CsPbBr3 NCs in toluene were treated in aqueous solutions of HX(X=Cl,Br,and I)and protonated oleylamine(OAm)acted as a carrier.The synthesized CsPbI3 NCs had an emission at 680 nm and even showed excellent colloidal stability after being stored for 32 d.The high efficiency and stability of the obtained CsPbX3 NCs were ascribed to the facts that:(ⅰ)the polar reagents were almost removed from the surface of NCs;(ⅱ)the defect-related nonradiative recombination was suppressed efficiently by surface passivation.
