A mechanochemical redox reaction between KMnO4 and CoCl2 was developed to obtain a CoxMn1-xOy catalyst with a specific surface area of 479 m^2 g^-1,which was higher than that obtained using a co-precipitation(CP)metho...A mechanochemical redox reaction between KMnO4 and CoCl2 was developed to obtain a CoxMn1-xOy catalyst with a specific surface area of 479 m^2 g^-1,which was higher than that obtained using a co-precipitation(CP)method(34 m2 g^-1),sol-gel(SG)method(72 m^2 g^-1),or solution redox process(131 m^2 g^-1).During catalytic combustion,this CoxMn1-xOy catalyst exhibited better activity(T100 for propylene=~200℃)than the control catalysts obtained using the SG(325℃)or CP(450℃)methods.The mechanical action,mainly in the form of kinetic energy and frictional heating,may generate a high degree of interstitial porosity,while the redox reaction could contribute to good dispersion of cobalt and manganese species.Moreover,the as-prepared CoxMn1-xOy catalyst worked well in the presence of water vapor(H2O 4.2%,>60 h)or SO2(100 ppm)and at high temperature(400℃,>60 h).The structure MnO2·(CoOOH)2.93 was suggested for the current CoxMn1-xOy catalyst.This catalyst could be extended to the total oxidation of other typical hydrocarbons(T90=150°C for ethanol,T90=225°C for acetone,T90=250℃for toluene,T90=120℃for CO,and T90=540℃for CH4).Scale-up of the synthesis of CoxMn1-xOy catalyst(1 kg)can be achieved via ball milling,which may provide a potential strategy for real world catalysis.展开更多
Gold（I） thiolate compounds （i.e. AuLSR） are important precursors for the synthesis of atom- ically precise Aun（SR）m nanoclusters. However, the nature of the AuI-SR precursor remains elusive. Here, we report that...Gold（I） thiolate compounds （i.e. AuLSR） are important precursors for the synthesis of atom- ically precise Aun（SR）m nanoclusters. However, the nature of the AuI-SR precursor remains elusive. Here, we report that the Aul0（TBBT）10 complex is a universal precursor for the synthesis of Aun（TBBT）m nanoclusters （where TBBT 4-tertbutylbenzenethiol/thiolate）. Interestingly, the Aul0（TBBT）10 complex is also found to be re-generated through extended etching of the Aun（SR）m nanoclusters with excess of TBBT thiol and O2. The formation of well-defined Aul0（TBBT）10 complex, instead of polymeric AuKSR, is attributed to the bulkiness of the TBBT thiol. Through 1D and 2D NMR charcteriztions, the structure of Aul0（TBBT）10 is correlated with the previously reported X-ray structure, which contains two inter-penetrated Aus（TBBT）5 rings. The photophysical property of Au10（TBBT）10 complex is further probed by femtosecond transient absorption spectroscopy. The acces- sibility of the precise Au10（TBBT）10 precursor improves the efficiency of the synthesis of the Aun（TBBT）m nanoclusters and is expected to further facilitate excellent control and understanding of the reaction mechanisms of nanocluster synthesis.展开更多
文摘A mechanochemical redox reaction between KMnO4 and CoCl2 was developed to obtain a CoxMn1-xOy catalyst with a specific surface area of 479 m^2 g^-1,which was higher than that obtained using a co-precipitation(CP)method(34 m2 g^-1),sol-gel(SG)method(72 m^2 g^-1),or solution redox process(131 m^2 g^-1).During catalytic combustion,this CoxMn1-xOy catalyst exhibited better activity(T100 for propylene=~200℃)than the control catalysts obtained using the SG(325℃)or CP(450℃)methods.The mechanical action,mainly in the form of kinetic energy and frictional heating,may generate a high degree of interstitial porosity,while the redox reaction could contribute to good dispersion of cobalt and manganese species.Moreover,the as-prepared CoxMn1-xOy catalyst worked well in the presence of water vapor(H2O 4.2%,>60 h)or SO2(100 ppm)and at high temperature(400℃,>60 h).The structure MnO2·(CoOOH)2.93 was suggested for the current CoxMn1-xOy catalyst.This catalyst could be extended to the total oxidation of other typical hydrocarbons(T90=150°C for ethanol,T90=225°C for acetone,T90=250℃for toluene,T90=120℃for CO,and T90=540℃for CH4).Scale-up of the synthesis of CoxMn1-xOy catalyst(1 kg)can be achieved via ball milling,which may provide a potential strategy for real world catalysis.
基金supported by the U.S.National Science Foundation(DMR-1808675)
文摘Gold（I） thiolate compounds （i.e. AuLSR） are important precursors for the synthesis of atom- ically precise Aun（SR）m nanoclusters. However, the nature of the AuI-SR precursor remains elusive. Here, we report that the Aul0（TBBT）10 complex is a universal precursor for the synthesis of Aun（TBBT）m nanoclusters （where TBBT 4-tertbutylbenzenethiol/thiolate）. Interestingly, the Aul0（TBBT）10 complex is also found to be re-generated through extended etching of the Aun（SR）m nanoclusters with excess of TBBT thiol and O2. The formation of well-defined Aul0（TBBT）10 complex, instead of polymeric AuKSR, is attributed to the bulkiness of the TBBT thiol. Through 1D and 2D NMR charcteriztions, the structure of Aul0（TBBT）10 is correlated with the previously reported X-ray structure, which contains two inter-penetrated Aus（TBBT）5 rings. The photophysical property of Au10（TBBT）10 complex is further probed by femtosecond transient absorption spectroscopy. The acces- sibility of the precise Au10（TBBT）10 precursor improves the efficiency of the synthesis of the Aun（TBBT）m nanoclusters and is expected to further facilitate excellent control and understanding of the reaction mechanisms of nanocluster synthesis.
