It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(...It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.展开更多
Unraveling atomic-level active sites of layered photocatalyst towards lowconcentration CO_(2) conversion is still challenging.Herein,the yield and selectivity of photocatalytic CO_(2) reduction of the Aurivillius-rela...Unraveling atomic-level active sites of layered photocatalyst towards lowconcentration CO_(2) conversion is still challenging.Herein,the yield and selectivity of photocatalytic CO_(2) reduction of the Aurivillius-related oxide semiconductor Bi_(2)O_(2)SiO_(3) nanosheet(BOSO)were largely improved using a surface sulfidation strategy.The experiment and theoretical calculation confirmed that surface sulfidation of the Bi_(2)O_(2)SiO_(3) nanosheet(S-BOSO,6.28 nm)redistributed the charge-enriched Bi sites,extended the solar spectrum absorption to the whole visible range,and considerably enhanced the charge separation,in addition to creating new reaction active sites,as compared to pristine BOSO.Subsequently,surface sulfidation played a switchable role,wherein S-BOSO showed a very high CH_(3)OH generation rate(12.78μmol g^(-1) for 4 h,78.6%selectivity)from low-concentration CO_(2)(1000 ppm)under visible light irradiation,which outperforms most of the state-of-the-art photocatalysts under similar conditions.This study presents an atomic-level modification protocol for engineering reactive sites and charge behaviors to promote solar-to-energy conversion.展开更多
基金supported by the National Key Research and Development Program of China(Nos.2022YFB3504100,2022YFB3506200)the National Natural Science Foundation of China(Nos.22208373,22376217)+1 种基金the Beijing Nova Program(No.20220484215)the Science Foundation of China University of Petroleum,Beijing(No.2462023YJRC030)。
文摘It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.
基金Natural Science Foundation of Hubei Province,Grant/Award Number:2021CFB242Research Project of Hubei Provincial Department of Education,Grant/Award Number:Q20202501+3 种基金China Postdoctoral Science Foundation,Grant/Award Number:2020M682878National Natural Science Foundation of China,Grant/Award Numbers:51971124,52104254,52171217State Key Laboratory of Electrical Insulation and Power Equipment,Xi'an Jiaotong University,Grant/Award Number:EIPE22208National Postdoctoral Program for Innovative Talents,Grant/Award Number:BX20200222。
文摘Unraveling atomic-level active sites of layered photocatalyst towards lowconcentration CO_(2) conversion is still challenging.Herein,the yield and selectivity of photocatalytic CO_(2) reduction of the Aurivillius-related oxide semiconductor Bi_(2)O_(2)SiO_(3) nanosheet(BOSO)were largely improved using a surface sulfidation strategy.The experiment and theoretical calculation confirmed that surface sulfidation of the Bi_(2)O_(2)SiO_(3) nanosheet(S-BOSO,6.28 nm)redistributed the charge-enriched Bi sites,extended the solar spectrum absorption to the whole visible range,and considerably enhanced the charge separation,in addition to creating new reaction active sites,as compared to pristine BOSO.Subsequently,surface sulfidation played a switchable role,wherein S-BOSO showed a very high CH_(3)OH generation rate(12.78μmol g^(-1) for 4 h,78.6%selectivity)from low-concentration CO_(2)(1000 ppm)under visible light irradiation,which outperforms most of the state-of-the-art photocatalysts under similar conditions.This study presents an atomic-level modification protocol for engineering reactive sites and charge behaviors to promote solar-to-energy conversion.
文摘目的探讨^(99m)Tc-3PRGD2 SPECT/CT显像半定量参数对可疑乳腺病变的诊断价值,并根据乳腺癌分子分型进行分类比较,分析其与临床病理的相关性。方法收集2020年12月~2022年8月于我院接受检查的70例可疑乳腺病变患者病例资料。根据病理结果,分析乳腺癌Luminal阳性型、Her-2阳性型和三阴性型3种分子亚型与T/N值的相关性;分析雌激素受体、孕激素受体、Her-2及Ki67表达情况与影像学检查指标的关系。结果70例患者病理检查结果证实乳腺癌51例(72.86%),病理分型为Luminal阳性型22例,Her-2阳性型20例,三阴性型9例。乳腺良性病变24例(27.14%)。乳腺癌患者病变侧T/N值高于良性病变患者(3.96±0.82 vs 1.16±0.32),差异有统计学意义(t=14.426,P<0.05)。诊断特异性为84.21%(16/19),敏感度为82.35%(42/51),准确率为82.86%(58/70),ROC曲线下面积为0.834(0.755~0.913),诊断临界值为1.56,即T/N值≥1.56时判定为恶性病变。Her-2阳性型的T/N值高于三阴性型(P<0.05)。Her-2表达阳性患者的T/N值高于Her-2表达阴性的患者(P<0.05)。雌激素受体、孕激素受体和Ki67表达阳性和表达阴性患者的T/N值相比,差异均无统计学意义(P>0.05)。结论^(99m)Tc-3PRGD2 SPECT/CT显像半定量指标在诊断乳腺病变良恶性方面有较高的敏感度,并且Her-2阳性型患者T/N值明显升高,有助于早期发现和诊断乳腺病变,为预测乳腺癌分子分型和治疗有相应的指导作用。
