Comparative Study of Oxygen Reduction Reaction Mechanisms on the Pd(111) and Pt(111) Surfaces in Acid Medium by DFT
Comparative Study of Oxygen Reduction Reaction Mechanisms on the Pd(111) and Pt(111) Surfaces in Acid Medium by DFT
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酸性介质中Pd(111)和Pt(111)表面氧还原反应机理的DFT对比研究
DOI：
10.1021/jp309094b
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发表时间：
2013-01-24
影响因子：
3.7
通讯作者：
Chen, Shengli
中科院分区：
文献类型：
--
作者：
Ou, Lihui;Chen, Shengli
采用密度泛函理论（DFT）的几何优化和最小能量路径计算方法，研究了Pd（111）和Pt（111）表面上氧还原反应（ORR）的机理，包括O-2分子的吸附、解离以及解离后吸附物的质子化.结果表明，在水合质子存在下，Pd（111）表面上的ORR是通过O-2分子的吸附和解离进行的，而Pt（111）表面上的ORR可能同时涉及O-2分子的吸附和解离以及OOH物种的形成和解离.在整个四电子ORB期间，在Pd（111）和Pt（111）表面上，吸附的O原子质子化生成OH是速率控制步骤（rds）。关于ORR的rds的这样的发现可以很好地解释为什么更弱地结合原子氧的Pt-和Pd-基催化剂具有更好的ORB。活动通过比较Pd（111）和Pt（111）表面上的ORR机理发现，O-2分子在Pt（111）表面上更容易发生吸附和解离过程，解离产物在Pt（111）表面上更容易质子化生成H2O分子.因此，两种金属之间的ORR的催化活性之间的差异很大，解释了为什么Pt可以作为ORR电催化剂，而廉价的Pd不能。
DFT geometry optimization and minimum energy path calculations were used to investigate the mechanisms of oxygen reduction reaction (ORR) on the Pd(111) and Pt(111) surfaces, including the adsorption I and dissociation of O-2 molecule and the protonation of dissociated adsorbates. The results indicated that in the presence of a hydrated proton ORR on the Pd(111) surface proceeded through the adsorption and dissociation of O-2 molecule, whereas ORR on the Pt(111) surface may involve in parallel the adsorption and dissociation of O-2 molecule as well as the formation and dissociation of OOH species. During the entire four-electron ORB., the protonation of adsorbed O atom to form OH is the rate-determining step (rds) on both of the Pd(111) and Pt( 111) surfaces. Such a finding about the rds of ORR can well explain why Pt- and Pd-based catalysts that more weakly bind atomic oxygen have better ORB. activity. Comparison of the ORR mechanisms on the Pd(111) and Pt(111) surfaces revealed that the adsorption and dissociation processes of O-2 molecule more easily occurred on the Pt(111) surface and that the serial protonation of the dissociative product to form H2O molecule also more easily occurred on the Pt(111) surface than on the Pd(111) surface. Therefore, the difference between the catalytic activities for ORR between both metals was large, explaining why Pt can serve as ORR electrocatalysts and the inexpensive Pd cannot.