（N, F）-codoped anatase TiO2 nanocrystals with active visible light response were prepared by using a simple sol-gel approach. X-ray photoelectron spectroscopy measurements suggested that the substitutional N and F s...（N, F）-codoped anatase TiO2 nanocrystals with active visible light response were prepared by using a simple sol-gel approach. X-ray photoelectron spectroscopy measurements suggested that the substitutional N and F species replaced the lattice oxygen atoms in TiO2 nanocrystals. Such nanocrystals showed strong absorption from 400 to 550 nm, which was mainly induced by nitrogen doping. The phase transformation from anatase to rutile was hindered by fluorine doping at high calcination temperatures, which was verified by XRD patterns. The N2 adsorption-desorption isotherms revealed the absence of mesopores in these nanocrystals. The （N, F）- codoped TiO2 nanocrystals showed satisfying photocatalytic activity on the photo-degradation of methylene blue under visible light.展开更多
N-doped TiO2 nanocrystals were prepared using titanium alkoxide as precipitant with different proportional materials. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission el...N-doped TiO2 nanocrystals were prepared using titanium alkoxide as precipitant with different proportional materials. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectra. It is confirmed experimentally that the photocatalytic activity of N-doped TiO2 is much higher than that of Degussa P25, when used for the degradation of crystal violet. The degradation kinetics follows an apparent first-order reaction, which is consistent with a generally observed Langmuir-Hinshelwood mechanism. The doping of TiO2 with nitrogen significantly increases the absorption in the region of visible light. The energy of the band gap of N-doped TiO2 is 2.92 eV. The better performance of N-doped TiO2 can be explained by the fact that it is also excited with longer-wavelength light.展开更多
The fabrication of high-quality electron-selective layers at low temperature is a prerequisite to realizing efficient flexible and tandem perovskite solar cells （PSCs）. A colloidal-quantum-dot ink that contains TiO2...The fabrication of high-quality electron-selective layers at low temperature is a prerequisite to realizing efficient flexible and tandem perovskite solar cells （PSCs）. A colloidal-quantum-dot ink that contains TiO2 nanocrystals enables the deposition of a flat film with matched energy level for PSCs; however, the selection of ligands on the TiO2 surface is still unexplored. Here, we systematically studied the effect of the titanium diisopropoxide bis（acetylacetonate） （TiAc2） ligand on the performance of PSCs with a planar n-i-p architecture. We prepared TiO2 nanocrystals from TiCI4 and ethyl alcohol with C1- ligands attached on its surface and we found that a tiny amount of TiAc2 treatment of as-prepared TiO2 nanocrystals in a mixed solution of chloroform and methyl alcohol can enhance PSC power conversion efficiency （PCE） from 14.7% to 18.3%. To investigate the effect of TiAc2 ligand on PSCs, TiO2 samples with different TiAc2 content were prepared by adding TiAc2 into the as-obtained TiO2 nanocrystal solution. We use x-ray photoelectron spectroscopy to identify the content of C1 so as to reveal that C1 ligands can be substituted by TiAc2. We speculate that the improvement in PCE originates from amorphous TiO2 formation on the TiO2 nanocrystal surface, whereby a single-molecule layer of amorphous TiO2 facilitates charge transfer between the perovskite film and the TiO2 electronic transport layer, but excessive TiAc2 lowers the PSC performance dramatically. We further prove our hypothesis by x-ray diffraction measurements. We believe the PCE of PSCs can be further improved by carefully choosing the type and changing the content of surface ligands on TiO2 nanocrystal.展开更多
In this work,the nature of physisorbed water and its impacts on the structure,surface chemistry,and proton conduction properties of TiO2 nanocrystals were investigated by a combinational spectral technique.All TiO2 na...In this work,the nature of physisorbed water and its impacts on the structure,surface chemistry,and proton conduction properties of TiO2 nanocrystals were investigated by a combinational spectral technique.All TiO2 nanocrystals were directly prepared by a hydrothermal method,which showed highly hydrated and sulfated surfaces.The surface water molecules were indicated to exist in a wide set of energetically nonequivalent surface hydration groups,leading to the removal of physisorbed and chemisorbed water in sequence with increasing temperature.After heating treatment at 100 ℃ in air,physisorbed water layers were recovered with no significant impacts on the TiO2 nanostructure.On the other hand,when treated at the same temperature in vacuum,the recovery of physisorbed water layers was partially reversible,while a new hydration state appeared due to the filling of the high-energy adsorption sites by water molecules,which led to a significant increase in the amount of water molecules for surface hydration and an accelerated dehydration process toward lower temperature.As a result,an abnormal increase was observed in proton conductivity.These observations were explained in terms of thermally induced changes of surface chemistry and the amount of hydrated water.The results reported in this work are important,which may help understand the roles that the physisorbed water plays in stabilizing the nanostructures and therefore could have a broad class of implications.展开更多
Transformation of greenhouse gas(CO_(2))into valuable chemicals and fuels is a promising route to address the global issues of climate change and the energy crisis.Metal halide perovskite catalysts have shown their po...Transformation of greenhouse gas(CO_(2))into valuable chemicals and fuels is a promising route to address the global issues of climate change and the energy crisis.Metal halide perovskite catalysts have shown their potential in promoting CO_(2)reduction reaction(CO_(2)RR),however,their low phase stability has limited their application perspective.Herein,we present a reduced graphene oxide(rGO)wrapped CsPbI_3 perovskite nanocrystal(NC)CO_(2)RR catalyst(CsPbI_3/rGO),demonstrating enhanced stability in the aqueous electrolyte.The CsPbI_3/rGO catalyst exhibited>92%Faradaic efficiency toward formate production at a CO_(2)RR current density of~12.7 mA cm^(-2).Comprehensive characterizations revealed the superior performance of the CsPbI_3/rGO catalyst originated from the synergistic effects between the CsPbI_3 NCs and rGO,i.e.,rGO stabilized theα-CsPbI_3 phase and tuned the charge distribution,thus lowered the energy barrier for the protonation process and the formation of~*HCOO intermediate,which resulted in high CO_(2)RR selectivity toward formate.This work shows a promising strategy to rationally design robust metal halide perovskites for achieving efficient CO_(2)RR toward valuable fuels.展开更多
In recent years,photocatalytic CO_(2)reduction reaction(CRR) has attracted much scientific attention to overcome energy and environmental issues by converting CO_(2)into high-value-added chemicals utilizing solar ener...In recent years,photocatalytic CO_(2)reduction reaction(CRR) has attracted much scientific attention to overcome energy and environmental issues by converting CO_(2)into high-value-added chemicals utilizing solar energy.Metal halide perovskite(MHP) nanocrystals(NCs) are recognized as an ideal choice for CRR owing to their outstanding optoelectronic properties.Although great efforts have been devoted to designing more effective photocatalysts to optimize CRR performance,severe charge recombination,instability,and unsatisfactory activity have become major bottlenecks in developing perovskite-based photocatalysts.In this review,we mainly focus on the recent research progress in the areas of relevance.First,a brief insight into reaction mechanisms for CRR and structural features of MHPs are introduced.Second,efficient modification approaches for the improvement of the photocatalytic activity and stability of the perovskite-based catalysts are comprehensively reviewed.Third,the state-of-the-art achievements of perovskite-based photocatalysts for CRR are systematically summarized and discussed,which are focused on the modification approaches,structure design,and the mechanism of the CO_(2)reduction process.Lastly,the current challenges and future research perspectives in the design and application of perovskite materials are highlighted from our point of view to provide helpful insights for seeking breakthroughs in the field of CRR.This review may provide a guide for scientists interested in applying perovskite-based catalysts for solar-to-chemical energy conversion.展开更多
The main bottleneck against industrial utilization of sodium ion batteries(SIBs)is the lack of high-capacity electrodes to rival those of the benchmark lithium ion batteries(LIBs).Here in this work,we have developed a...The main bottleneck against industrial utilization of sodium ion batteries(SIBs)is the lack of high-capacity electrodes to rival those of the benchmark lithium ion batteries(LIBs).Here in this work,we have developed an economical method for in situ fabrication of nanocomposites made of crystalline few-layer graphene sheets loaded with ultrafine SnO_(2)nanocrystals,using short exposure of microwave to xerogel of graphene oxide(GO)and tin tetrachloride containing minute catalyzing dispersoids of chemically reduced GO(RGO).The resultant nanocomposites(SnO_(2)@MWG)enabled significantly quickened redox processes as SIB anode,which led to remarkable full anode-specific capacity reaching 538 mAh g^(−1)at 0.05 A g^(−1)(about 1.45 times of the theoretical capacity of graphite for the LIB),in addition to outstanding rate performance over prolonged charge–discharge cycling.Anodes based on the optimized SnO_(2)@MWG delivered stable performance over 2000 cycles even at a high current density of 5 A g^(−1),and capacity retention of over 70.4%was maintained at a high areal loading of 3.4 mg cm^(−2),highly desirable for high energy density SIBs to rival the current benchmark LIBs.展开更多
Sodium-ion hybrid capacitor(SIHC)is one of the most promising alternatives for large-scale energy storage due to its high energy and power densities,natural abundance,and low cost.However,overcoming the imbalance betw...Sodium-ion hybrid capacitor(SIHC)is one of the most promising alternatives for large-scale energy storage due to its high energy and power densities,natural abundance,and low cost.However,overcoming the imbalance between slow Na^(+)reaction kinetics of battery-type anodes and rapid ion adsorption/desorption of capacitive cathodes is a significant challenge.Here,we propose the high-rate-performance NiS_(2)@OMGC anode material composed of monodispersed NiS_(2) nanocrystals(8.8±1.7 nm in size)and N,S-co-doped graphenic carbon(GC).The NiS_(2)@OMGC material has a three-dimensionally ordered macroporous(3DOM)morphology,and numerous NiS_(2) nanocrystals are uniformly embedded in GC,forming a core-shell structure in the local area.Ultrafine NiS_(2) nanocrystals and their nano-microstructure demonstrate high pseudocapacitive Na-storage capability and thus excellent rate performance(355.7 mAh/g at 20.0 A/g).A SIHC device fabricated using NiS_(2)@OMGC and commercial activated carbon(AC)cathode exhibits ultrahigh energy densities(197.4 Wh/kg at 398.8 W/kg)and power densities(43.9 kW/kg at 41.3 Wh/kg),together with a long life span.This outcome exemplifies the rational architecture and composition design of this type of anode material.This strategy can be extended to the design and synthesis of a wide range of high-performance electrode materials for energy storage applications.展开更多
化工、纺织印染与农药化肥等产业的蓬勃发展推动着人类社会的进步,但同时也给环境治理带来了巨大难题。目前,光催化降解局限于在特定波长下针对单一有机污染物进行降解,然而现实中的情况往往更复杂。因此,开发一种多功能光催化材料用于...化工、纺织印染与农药化肥等产业的蓬勃发展推动着人类社会的进步,但同时也给环境治理带来了巨大难题。目前,光催化降解局限于在特定波长下针对单一有机污染物进行降解,然而现实中的情况往往更复杂。因此,开发一种多功能光催化材料用于光催化降解不同有机污染物显得尤为重要。采用一步无模板溶剂热法合成了核壳结构的C-TiO_(2)复合材料前驱体,并在氩气气氛下煅烧得到高结晶度的C-TiO_(2)复合光催化材料。运用SEM、TEM、XRD和TG等表征手段对材料进行表征,结论如下:550℃煅烧时的样品为包含少量碳的高结晶度的锐钛矿相TiO 2,且550℃煅烧时的样品依然保持了完整的核壳结构。此外,C-TiO_(2)复合材料的比表面积高达85.69 m 2·g^(-1),平均孔径为16.4 nm以及孔体积为0.423 m 3·g^(-1)。在UV-Vis光照射下,C-TiO_(2)复合材料分别对罗丹明B(RhB)、亚甲基蓝(MB)和刚果红(CR)3种染料显示出增强的光催化降解活性。展开更多
基金supported by the Excellent Young Teachers Program of MOEKey Project of Shanghai Science and Technology Committee (No. 06DZ05025),China
文摘（N, F）-codoped anatase TiO2 nanocrystals with active visible light response were prepared by using a simple sol-gel approach. X-ray photoelectron spectroscopy measurements suggested that the substitutional N and F species replaced the lattice oxygen atoms in TiO2 nanocrystals. Such nanocrystals showed strong absorption from 400 to 550 nm, which was mainly induced by nitrogen doping. The phase transformation from anatase to rutile was hindered by fluorine doping at high calcination temperatures, which was verified by XRD patterns. The N2 adsorption-desorption isotherms revealed the absence of mesopores in these nanocrystals. The （N, F）- codoped TiO2 nanocrystals showed satisfying photocatalytic activity on the photo-degradation of methylene blue under visible light.
基金supported by the Outstanding Adult-Young Scientific Research Encouraging Foundation of Shandong Province (No.2008BS09016)the Nature Science Foundation of Shandong Province (No.Y2007B15)the Scientific Research Program of Shandong Province Education Department, China (No.J06D55)
文摘N-doped TiO2 nanocrystals were prepared using titanium alkoxide as precipitant with different proportional materials. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectra. It is confirmed experimentally that the photocatalytic activity of N-doped TiO2 is much higher than that of Degussa P25, when used for the degradation of crystal violet. The degradation kinetics follows an apparent first-order reaction, which is consistent with a generally observed Langmuir-Hinshelwood mechanism. The doping of TiO2 with nitrogen significantly increases the absorption in the region of visible light. The energy of the band gap of N-doped TiO2 is 2.92 eV. The better performance of N-doped TiO2 can be explained by the fact that it is also excited with longer-wavelength light.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51622201,61571015,and 91433102)
文摘The fabrication of high-quality electron-selective layers at low temperature is a prerequisite to realizing efficient flexible and tandem perovskite solar cells （PSCs）. A colloidal-quantum-dot ink that contains TiO2 nanocrystals enables the deposition of a flat film with matched energy level for PSCs; however, the selection of ligands on the TiO2 surface is still unexplored. Here, we systematically studied the effect of the titanium diisopropoxide bis（acetylacetonate） （TiAc2） ligand on the performance of PSCs with a planar n-i-p architecture. We prepared TiO2 nanocrystals from TiCI4 and ethyl alcohol with C1- ligands attached on its surface and we found that a tiny amount of TiAc2 treatment of as-prepared TiO2 nanocrystals in a mixed solution of chloroform and methyl alcohol can enhance PSC power conversion efficiency （PCE） from 14.7% to 18.3%. To investigate the effect of TiAc2 ligand on PSCs, TiO2 samples with different TiAc2 content were prepared by adding TiAc2 into the as-obtained TiO2 nanocrystal solution. We use x-ray photoelectron spectroscopy to identify the content of C1 so as to reveal that C1 ligands can be substituted by TiAc2. We speculate that the improvement in PCE originates from amorphous TiO2 formation on the TiO2 nanocrystal surface, whereby a single-molecule layer of amorphous TiO2 facilitates charge transfer between the perovskite film and the TiO2 electronic transport layer, but excessive TiAc2 lowers the PSC performance dramatically. We further prove our hypothesis by x-ray diffraction measurements. We believe the PCE of PSCs can be further improved by carefully choosing the type and changing the content of surface ligands on TiO2 nanocrystal.
基金supported by NNSFC (No.200903097,20771101)National Basic Research Program of China (No.2007CB613301,206L205)+1 种基金FIPYT (No. 2008F3116)FJIRSM (No. 2010KL002,SZD08002-3)
文摘In this work,the nature of physisorbed water and its impacts on the structure,surface chemistry,and proton conduction properties of TiO2 nanocrystals were investigated by a combinational spectral technique.All TiO2 nanocrystals were directly prepared by a hydrothermal method,which showed highly hydrated and sulfated surfaces.The surface water molecules were indicated to exist in a wide set of energetically nonequivalent surface hydration groups,leading to the removal of physisorbed and chemisorbed water in sequence with increasing temperature.After heating treatment at 100 ℃ in air,physisorbed water layers were recovered with no significant impacts on the TiO2 nanostructure.On the other hand,when treated at the same temperature in vacuum,the recovery of physisorbed water layers was partially reversible,while a new hydration state appeared due to the filling of the high-energy adsorption sites by water molecules,which led to a significant increase in the amount of water molecules for surface hydration and an accelerated dehydration process toward lower temperature.As a result,an abnormal increase was observed in proton conductivity.These observations were explained in terms of thermally induced changes of surface chemistry and the amount of hydrated water.The results reported in this work are important,which may help understand the roles that the physisorbed water plays in stabilizing the nanostructures and therefore could have a broad class of implications.
基金financial support by Australian Research Council(ARC)supported by the generous funding from Science and Engineering faculty,QUT。
文摘Transformation of greenhouse gas(CO_(2))into valuable chemicals and fuels is a promising route to address the global issues of climate change and the energy crisis.Metal halide perovskite catalysts have shown their potential in promoting CO_(2)reduction reaction(CO_(2)RR),however,their low phase stability has limited their application perspective.Herein,we present a reduced graphene oxide(rGO)wrapped CsPbI_3 perovskite nanocrystal(NC)CO_(2)RR catalyst(CsPbI_3/rGO),demonstrating enhanced stability in the aqueous electrolyte.The CsPbI_3/rGO catalyst exhibited>92%Faradaic efficiency toward formate production at a CO_(2)RR current density of~12.7 mA cm^(-2).Comprehensive characterizations revealed the superior performance of the CsPbI_3/rGO catalyst originated from the synergistic effects between the CsPbI_3 NCs and rGO,i.e.,rGO stabilized theα-CsPbI_3 phase and tuned the charge distribution,thus lowered the energy barrier for the protonation process and the formation of~*HCOO intermediate,which resulted in high CO_(2)RR selectivity toward formate.This work shows a promising strategy to rationally design robust metal halide perovskites for achieving efficient CO_(2)RR toward valuable fuels.
基金supported by the National Natural Science Foundation of China (52102166)the China Postdoctoral Science Foundation under Grant Nos. 2019M663058, 2021M701065,2019M652749, 2021M701071, and 2022T150187+3 种基金the Program for Innovative Research Team in University of Henan Province(21IRTSTHN009)Science and Technology Development Plan of Henan Province (212300410029, 202300410087, 202102210251)the Key Research&Development and Promotion Project of Henan Province (Science and Technology Tackling Key Problems) under Grant Nos. 222102320182, 222102240070Henan Center for Outstanding Overseas Scientists (GZS2022014)。
文摘In recent years,photocatalytic CO_(2)reduction reaction(CRR) has attracted much scientific attention to overcome energy and environmental issues by converting CO_(2)into high-value-added chemicals utilizing solar energy.Metal halide perovskite(MHP) nanocrystals(NCs) are recognized as an ideal choice for CRR owing to their outstanding optoelectronic properties.Although great efforts have been devoted to designing more effective photocatalysts to optimize CRR performance,severe charge recombination,instability,and unsatisfactory activity have become major bottlenecks in developing perovskite-based photocatalysts.In this review,we mainly focus on the recent research progress in the areas of relevance.First,a brief insight into reaction mechanisms for CRR and structural features of MHPs are introduced.Second,efficient modification approaches for the improvement of the photocatalytic activity and stability of the perovskite-based catalysts are comprehensively reviewed.Third,the state-of-the-art achievements of perovskite-based photocatalysts for CRR are systematically summarized and discussed,which are focused on the modification approaches,structure design,and the mechanism of the CO_(2)reduction process.Lastly,the current challenges and future research perspectives in the design and application of perovskite materials are highlighted from our point of view to provide helpful insights for seeking breakthroughs in the field of CRR.This review may provide a guide for scientists interested in applying perovskite-based catalysts for solar-to-chemical energy conversion.
基金funded by the Zhengzhou Materials Genome Institute,the National Talents Program of China,and Key Innovation Projects of the Zhengzhou Municipal City of China.
文摘The main bottleneck against industrial utilization of sodium ion batteries(SIBs)is the lack of high-capacity electrodes to rival those of the benchmark lithium ion batteries(LIBs).Here in this work,we have developed an economical method for in situ fabrication of nanocomposites made of crystalline few-layer graphene sheets loaded with ultrafine SnO_(2)nanocrystals,using short exposure of microwave to xerogel of graphene oxide(GO)and tin tetrachloride containing minute catalyzing dispersoids of chemically reduced GO(RGO).The resultant nanocomposites(SnO_(2)@MWG)enabled significantly quickened redox processes as SIB anode,which led to remarkable full anode-specific capacity reaching 538 mAh g^(−1)at 0.05 A g^(−1)(about 1.45 times of the theoretical capacity of graphite for the LIB),in addition to outstanding rate performance over prolonged charge–discharge cycling.Anodes based on the optimized SnO_(2)@MWG delivered stable performance over 2000 cycles even at a high current density of 5 A g^(−1),and capacity retention of over 70.4%was maintained at a high areal loading of 3.4 mg cm^(−2),highly desirable for high energy density SIBs to rival the current benchmark LIBs.
基金supported by the National Natural Science Foundation of Tianjin(No.20JCQNJC01280)the National Natural Science Foundation of China(No.21905201)+1 种基金the support of the scientifi c research project from China Three Gorges Corporation(No.202103406)supported by Tohoku University and JSPS KAKENHI(No.JP16J06828).
文摘Sodium-ion hybrid capacitor(SIHC)is one of the most promising alternatives for large-scale energy storage due to its high energy and power densities,natural abundance,and low cost.However,overcoming the imbalance between slow Na^(+)reaction kinetics of battery-type anodes and rapid ion adsorption/desorption of capacitive cathodes is a significant challenge.Here,we propose the high-rate-performance NiS_(2)@OMGC anode material composed of monodispersed NiS_(2) nanocrystals(8.8±1.7 nm in size)and N,S-co-doped graphenic carbon(GC).The NiS_(2)@OMGC material has a three-dimensionally ordered macroporous(3DOM)morphology,and numerous NiS_(2) nanocrystals are uniformly embedded in GC,forming a core-shell structure in the local area.Ultrafine NiS_(2) nanocrystals and their nano-microstructure demonstrate high pseudocapacitive Na-storage capability and thus excellent rate performance(355.7 mAh/g at 20.0 A/g).A SIHC device fabricated using NiS_(2)@OMGC and commercial activated carbon(AC)cathode exhibits ultrahigh energy densities(197.4 Wh/kg at 398.8 W/kg)and power densities(43.9 kW/kg at 41.3 Wh/kg),together with a long life span.This outcome exemplifies the rational architecture and composition design of this type of anode material.This strategy can be extended to the design and synthesis of a wide range of high-performance electrode materials for energy storage applications.
文摘化工、纺织印染与农药化肥等产业的蓬勃发展推动着人类社会的进步,但同时也给环境治理带来了巨大难题。目前,光催化降解局限于在特定波长下针对单一有机污染物进行降解,然而现实中的情况往往更复杂。因此,开发一种多功能光催化材料用于光催化降解不同有机污染物显得尤为重要。采用一步无模板溶剂热法合成了核壳结构的C-TiO_(2)复合材料前驱体,并在氩气气氛下煅烧得到高结晶度的C-TiO_(2)复合光催化材料。运用SEM、TEM、XRD和TG等表征手段对材料进行表征,结论如下:550℃煅烧时的样品为包含少量碳的高结晶度的锐钛矿相TiO 2,且550℃煅烧时的样品依然保持了完整的核壳结构。此外,C-TiO_(2)复合材料的比表面积高达85.69 m 2·g^(-1),平均孔径为16.4 nm以及孔体积为0.423 m 3·g^(-1)。在UV-Vis光照射下,C-TiO_(2)复合材料分别对罗丹明B(RhB)、亚甲基蓝(MB)和刚果红(CR)3种染料显示出增强的光催化降解活性。
