H2、O2与Pd反应的平衡压力研究

基于电子与核振动近似方法，应用密度泛函B3P86方法和相对论有效核势SDD计算，结合统计热力学方法, 研究了100K～1000K温度范围内Pd与H2、O2反应的标准生成热力学函数以及反应平衡压力与温度的关系. 结果表明：Pd与H2、O2反应是放热反应，Pd原子吸附H2的放热量大于吸附O2的放热量，温度升高不利于吸附反应进行；Pd对O2的自发吸附温度很低，室温下几乎不能进行，而对H2的自发吸附温度可高达500K以上；在100K~284.394K可自发吸附O2和H2的温度范围内，O2的反应平衡压力比H2的平衡压力高出9~18个数量级. 因此，O2作为杂质气体对目标反应Pd-H2的影响非常有限.

Equilibrium pressures for reactions of Pd with H2 and O2

At the temperature from 100K to 1000K, the standard formation enthalpy changes, entropy changes, free energy changes, and equilibrium gas pressures for reactions of Pd with gases H2 and O2 have been calculated combining density functional method B3P86 and basis set SDD with statistic thermodynamics, based on the method of electron and nuclear vibration approximation. The results show that Pd adsorbing H2 and O2 are exothermal reactions with larger released heat for adsorbing H2 than O2, and the released heats both rise with increasing temperature, which is unfavorable to the adsorbing reactions; the temperature for Pd automatically adsorbing O2 is so low that reaction hardly occurs at room temperature; on the contrary, the temperature for Pd automatically adsorbing H2 is over 500K; the equilibrium gas pressures of O2 are far larger than that of H2 by 9-18 orders of magnitude at the automatically adsorbing temperatures from 100K to 284.394K. Therefore, the O2 acted as an impurity gas affects the Pd-H2 reaction at very low level.