Selectivity of Palladium鈥揅obalt Surface Alloy toward Oxygen Reduction Reaction
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- 作者：Do Ngoc Son ; Kaito Takahashi
- 刊名：The Journal of Physical Chemistry C
- 出版年：2012
- 出版时间：March 15, 2012
- 年：2012
- 卷：116
- 期：10
- 页码：6200-6207
- 全文大小：331K
- 年卷期：v.116,no.10(March 15, 2012)
- ISSN：1932-7455
文摘
Oxygen reduction reaction (ORR), O2 + 4(H+ + e鈥?/sup>) 鈫?2H2O, is one of the most important fundamental reactions occurring on the cathode catalytic surface of hydrogen fuel cells. Developing new catalysts by alloying metals other than the well-known but expensive Pt is the most feasible and economical way to improve the proficiency of fuel cells to a practicable level. In this paper, we employed density functional theory calculations to study the ORR mechanism on a promising and cheaper catalyst of PdCo(111) surface alloy. From the calculated enthalpy of mixing, we found that the alloy is most stable at about 30% Co; hence, the alloying substrates were sampled at this concentration of Co for exploring the ORR intermediates. We discovered on the PdCo substrates a new intermediate OHO that was not seen previously for Pt and Pd resulting in a new reaction pathway. From the detailed analysis on the reaction free energy diagrams, we gauged the ORR efficiency of the alloy versus Pt. The obtained results are in agreement with experiments in which the ORR activity of the alloy was found to be higher than that of Pt. We found that maximizing the number of Co atoms at the second atomic layer underneath a Pd skin provides the highest activity for the ORR.