SOFC中Ni-YSZ阳极催化剂上的CH_4吸附活化机理研究

Adsorption and Activation of CH_4 in the Ni-YSZ SOFC Anode Catalyst

分别在600℃、700℃和800℃原位动态下,Ni-YSZ阳极催化剂上吸附CH4的DR FT-IR谱表明,在2937和2860cm-1的吸收峰分别对应于CH3反对称和CH3对称伸缩振动吸收,这是CH4在Ni-YSZ阳极的Ni金属活性位上发生解离脱氢所致,说明CH4可发生解离生成中间物种CHx(x=1～3)。计算结果表明,在CH4分子与金属Ni阳极催化剂的相互作用的四种可能途径中,前三种反应途径可能得到的中间体构型均不能收敛,从而前三种反应途径发生的可能性很小。而优化第四种反应途径时却得到了稳定的中间体构型。这表明,CH4中靠Ni端较近的C-H键已被Ni原子微弱地活化,一个强束缚的原子-分子复合物NiCH4已形成,使得CH4的Td对称性降到C2v的对称性,从而使得红外禁阻的谱带发生分裂并可在实验检测到。本计算结果与实验所发现的事实相一致。

The DR-P-FIR spectra of adsorbed CH4 on Ni-YSZ anode at 600℃, 700℃ and 800℃ show that the absorption peaks in 2937 and 2860cm-1 occur in the CH3 asymmetric and symmetric stretching vibration bands. It＇s caused by the CH4 dissociation in the active metal site of Ni on the anode, the abstraction of hydrogen and the production of CHx （x = 1 - 3）. Calculation results show that, of the four possible dissociations of CH4 molecules on a Ni-based anode, the configuration of the intermediate products from the first three cannot be convergent, and thus the likelihood of the three reactions is small. Optimizing the fourth can produce a stable intermediate configuration. This indicates that, with the C-H bond of CH4 close to Ni support weakly activated by Ni atoms, a strongly-bonded atom-molecule NiCH4 complex is formed, lowering the symmetry of CH4 from Td to C2v, and making the infrared forbidden band split and detectable in the experiment. The calculation results are consistent with those of the experiment.