Thermodynamics of Carbon Monoxide Adsorption on Cu/SBA-15 Catalysts: Under Vacuum versus under Atmospheric Pressures
Thermodynamics of Carbon Monoxide Adsorption on Cu/SBA-15 Catalysts: Under Vacuum versus under Atmospheric Pressures
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DOI：
10.1021/acs.jpcc.1c10722
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
T. Han;Ilkeun Lee;Yueqiang Cao;Xinggui Zhou;F. Zaera
中科院分区：
文献类型：
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作者：
T. Han;Ilkeun Lee;Yueqiang Cao;Xinggui Zhou;F. Zaera
利用现场红外吸收光谱实验数据，估算了一氧化碳在铜基催化剂上的吸附热力学。在真空环境下和在CO气体存在下进行了直接的能量比较。结果表明，从第一种情况到第二种情况，从ΔH°ads=−82 kJ/Δ到CO-atm=−21 kJ/m o l，吸附热值降低了近4倍。此外，对数据的等量分析表明，后者的大小在低覆盖范围内减小到低于ΔH°ads的值，CO-atm=−18kJ/mol，这与在其他系统中报道的趋势相反。用相关的吸附标准熵解释了这些观测结果，在气相CO存在的情况下，该吸附标准熵是在ΔS°Ads，CO-atm∼−24J/(MolK)下估算的，这个数值比CO凝聚的标准熵小得多。CO吸附的过剩熵大于CO缩合的过剩熵是由于气相分子引起的吸附置换和吸附辅助吸附步骤等附加现象引起的吸附状态的过剩熵。
The thermodynamics of the adsorption of carbon monoxide on a copper-based catalyst were estimated by using data fromin situinfrared absorption spectroscopy experiments. A direct comparison was performed between the energetics under a vacuum environment versus in the presence of CO gas. It was found that the magnitude of the enthalpy of adsorption is reduced by almost a factor of 4 in going from the first case to the second, from ΔH°ads,vacuum= −82 kJ/mol to ΔH°ads,CO-atm= −21 kJ/mol. Furthermore, isosteric analysis of the data indicated that the magnitude of the latter decreases in the low-coverage limit, to values below ΔH°ads,CO-atm= −18 kJ/mol, a trend opposite to what has been reported in other systems. These observations are explained in terms of the associated standard entropy of adsorption, which in the presence of gas-phase CO was estimated at ΔS°ads,CO-atm∼ −24 J/(mol K), a value much smaller in magnitude than the standard entropy of CO condensation. The excess entropy of CO adsorption over that of CO condensation is here ascribed to excess entropy in the adsorbed state due to additional phenomena induced by the gas-phase molecules such as adsorbate displacement and adsorbate-assisted adsorption steps.