Investigation into the Competitive and Site-Specific Nature of Anion Adsorption on Pt Using In Situ X-ray Absorption Spectroscopy
Investigation into the Competitive and Site-Specific Nature of Anion Adsorption on Pt Using In Situ X-ray Absorption Spectroscopy
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DOI：
10.1021/jp8067359
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发表时间：
2008-11-20
影响因子：
3.7
通讯作者：
Ramaker, David E.
中科院分区：
文献类型：
--
作者：
Arruda, Thomas M.;Shyam, Badri;Ramaker, David E.
原位X射线吸收光谱沿着电化学测量（CV和RDE）和先前发表的EQCN数据提供了对酸性介质（HClO4）中碳载铂簇（1 - 2 nm）不同面/位点上氯中毒性质的进一步理解。在研究的Cl-浓度（10（-3）和10（-2）M）下，氯化物显示吸附在Pt（111）面上的3重位点。当Cl-在Pt（111）表面上形成压缩吸附层时，发现顶部氯化物存在于窄电位范围（0.4 - 0.7 V RHE）内，迫使一些Cl-存在于顶部/桥接位点。阴离子（Cl-，Br-，OH-，和HSO 4-）吸附在Pt的不同表面上的相互作用也被认为是。例如，O/OH可以很容易地取代边缘/角落上的顶部氯化物，但不能取代Pt（111）位点上的Cl-，因此Cl-显著提高了Pt（111）位点上水活化的过电位。氯化物也会显著改变ORR，导致氯化物浓度每增加10倍，超电位增加约85 mV，在Pt（111）位点的高浓度下，超电位总共增加150 - 200 mV。最后，Cl-离子不能取代在Pt（111）面上形成的硫酸氢盐覆盖层;然而，一旦硫酸氢盐吸附在较高电位下受到干扰，硫酸氢盐就不能取代Cl-吸附。这些相对的阴离子吸附偏好可以帮助解释重要的ORR对阴离子吸附的不同依赖性，并表明Cl-中毒的影响可能与Pt颗粒尺寸密切相关。
In situ X-ray absorption spectroscopy along with electrochemical measurements (CV and RDE) and previously published EQCN data provide further understanding of the nature of chloride poisoning on different faces/sites of carbon supported platinum clusters (1-2 nm) in acidic medium (HClO4). Chloride is shown to adsorb in 3-fold sites on the Pt(111) faces at the investigated Cl- concentrations (10(-3) and 10(-2) M). Atop chloride was found to be present within a narrow potential range (0.4-0.7 V RHE) when compressed adlayers of Cl- are formed on the Pt(111) faces forcing some Cl- to exist in atop/bridged sites. The interplay of anionic (Cl-, Br-, OH-, and HSO4-) adsorption on the different surfaces of Pt are also considered. For example O/OH can easily displace atop chloride on the edges/corners but not the Cl- at the Pt(111) sites, and therefore Cl- dramatically raises the overpotential for water activation at the Pt(111) sites. Chloride also drastically alters the ORR causing an increase of the overpotential by similar to 85 mV for every 10-fold increase in chloride concentration with a total 150-200 mV increase in the overpotential at large concentrations at the Pt(111) sites. Finally Cl- ions cannot displace the bisulfate overlayer on the Pt(111) faces after it is formed at lower potentials; however, once the bisulfate adsorption is disturbed at higher potentials, the bisulfate cannot displace the Cl- adsorption. These relative anion adsorption preferences can help to explain the different dependencies of the important ORR on anion adsorption, and suggests that the effect of Cl- poisoning might be quite dependent on the Pt particle size.