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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Impact of the Reconstruction of Gold Particles on the Heats of Adsorption of Linear CO Species Adsorbed on the Au Sites of a 1% Au/Al2O3 Catalyst
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Impact of the Reconstruction of Gold Particles on the Heats of Adsorption of Linear CO Species Adsorbed on the Au Sites of a 1% Au/Al2O3 Catalyst

机译：金颗粒的重构对1％Au / Al2O3催化剂的Au位上吸附的线性CO物种的吸附热的影响

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摘要

The adsorption of CO at 300 K on a reduced(H2,713 K)1% Au/Al2O3 solid leads to the formation of a linear CO species adsorbed on the Au particles(denoted L1)characterized by an IR band at 2098 cm~(-1)that slightly shifts to higher wavenumbers with the decrease in the coverage.For adsorption pressures P_a > 5 kPa,it is shown that there is a progressive reconstruction of the Au surface with the increase in the duration of the adsorption t_a leading to the disappearance of the Au sites associated with the L1 CO species and to the formation of new Au sites forming a linear CO species(denoted L2)characterized by an IR band at 2070 cm~(-1).The heats of adsorption of the two adsorbed species are determined as the function of their respective coverages by using the adsorption equilibrium infrared spectroscopy procedure previously developed.It is shown that they linearly decrease with the increase in their coverages from 62 to 43 kJ/mol for the L1 and from 100 to 50 kJ/mol for the L2 CO species at coverages 0 and 1,respectively.The values for the L1 CO species are consistent with a previous study on Au/TiO2 and with literature data on model Au particles.The higher heat of adsorption of the L2 CO species as compared to that of L1 can be a driving force for the reconstruction of the Au particles.Moreover,it is shown that the L2 CO species presents a property similar to that of adsorbed CO species on reduced supported metal particles:the position of its IR band shifts to lower wavenumbers with the decrease in its coverage(the singleton is situated at 2025 cm~(-1)).The sintering of the gold particles as a function of the number of pretreatment/reconstruction cycles leads to the detection of a third linear CO species characterized by an IR band at 2048 cm~(-1)at 300 K with heats of adsorption of 80 and 60 kJ/mol at low and high coverages,respectively.
机译：在还原的（H2,713 K）1％Au / Al2O3固体上300 K的CO吸附导致形成线性的CO物种吸附在以2098 cm〜（ -1）随着覆盖率的降低而略微移向更高的波数。对于吸附压力P_a> 5 kPa，表明随着吸附时间t_a的增加，Au表面逐渐进行重构，从而导致与L1 CO物种相关的Au位点消失，并形成新的Au位点，形成一个线性的CO物种（表示为L2），其特征是在2070 cm〜（-1）处的IR波段。通过使用先前开发的吸附平衡红外光谱法确定物种的覆盖率，结果表明，随着L1覆盖率从62 kJ / mol和43 kJ / mol以及100 kJ至50 kJ的覆盖率增加，它们呈线性下降/ mol（对于L2 CO物种） L1 CO物种的值与先前关于Au / TiO2的研究以及模型Au颗粒的文献数据相一致.L2 CO物种的吸附热比L1高。可以证明，L2CO的性质与还原的负载金属粒子上吸附的CO的性质相似：其IR谱带的位置随着（单晶位于2025 cm〜（-1）处）。金颗粒的烧结与预处理/重构循环次数的函数关系导致检测到第三种线性CO物种，其特征为在300 K下2048 cm〜（-1）的红外波段在低和高覆盖下分别具有80和60 kJ / mol的吸附热。

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