CO2在Pd表面吸附的热力学

 用密度泛函方法和相对论有效原子实势,分别对PdCO₂，PdCO和PdH的基态几何构型进行优化, 得到PdCO₂分子基态为Cs构型, Pd与CO2分子在同一平面, 键长PdC为0.203 0 nm, CO为0.118 3 nm, CO′为0.121 0 nm, 键角∠OCO′为154.215°,电子状态为1A′; PdCO分子基态电子状态为1+, 键长PdC为0.183 4 nm, CO为0.114 0 nm, 键角∠PdCO为180°; PdH分子基态为2∑, 键长PdH为0.152 6 nm。根据电子-振动近似理论计算了不同温度下金属Pd 与CO₂，CO及H2分子反应的生成热力学函数, 导出了反应平衡压力随温度的变化关系。分析认为杂质CO₂气体引起Pd合金膜中毒可能是由于CO₂分子吸附在Pd膜表面,形成Pd的CO₂化合物后，再自发分解为PdO和CO，而使Pd表面出现O和CO中毒所致。

Thermodynamics of CO_2 adsorbed on palladium surface

The structures of PdCO₂, PdCO, and PdH are optimized by the relativistic effective core potential (RECP) and the density functional theory B3P86 method. The results show that the stable geometry of Pd-CO₂ molecule is plane structure. The ground state of PdCO2 is (X1A′) of Cs group. The structure parameters of RPdC, RCO, RC O′ and∠OCO′ are 0.203 0 nm, 0.118 3 nm, 0.121 0 nm and 154.215°,respectively. For PdCO molecule, the ground state is 1∑+, and the structure parameters of R(PdC), R(CO), and ∠PdCO are 0.183 4 nm, 0.114 0 nm, and 180°, respectively. The ground state of PdH is 2∑, and the bond length is 0.152 6 nm. Furthermore, the thermodynamic functions of PdCO₂, PdCO, and PdH are also calculated according to electronic-vibration approximation. An