Origin of non-Faradayicity in electrochemical promotion of catalytic ethylene oxidation.
Origin of non-Faradayicity in electrochemical promotion of catalytic ethylene oxidation.
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催化乙烯氧化的电化学促进中非法拉第性的起源。
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
R. Imbihl
中科院分区：
文献类型：
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作者：
Arafat Toghan;Liz M. Rösken;R. Imbihl
在低压条件下(p约为10(-6)-10(-4)mbar)，以氧化钇(YSZ)为催化剂，研究了铂催化氧化C(2)H(4)的电化学促进作用。所有测量都使用超高真空系统进行，其中差动泵浦四重质谱仪(QMS)用于速率测量，光电子发射显微镜(PEEM)用于空间分辨测量。在开路条件下，p(C(2)H(4))的循环变化出现明显的速率滞后，这归因于碳基CH(X)吸附抑制了O(2)的吸附，从而毒化了反应。施加正电位会导致溢出氧部分去除抑制CH(X)的附着层，从而触发从表面的有毒状态到碳覆盖率降低的活性状态的转变。点火效应和电化学促进效应与表面碳附着层的存在有关。在该反应体系中观察到的非法拉第效应被解释为点火效应。
The electrochemical promotion of catalytic C(2)H(4) oxidation has been investigated under low pressure conditions (p approximately 10(-6)-10(-4) mbar) with a Pt film on yttrium stabilized zirconia (YSZ) as catalyst. All measurements were conducted with a UHV system with a differentially pumped quadruple mass spectrometer (QMS) for rate measurements and a photoelectron emission microscope (PEEM) for spatially resolved measurements. A pronounced rate hysteresis upon cyclic variation of p(C(2)H(4)) was observed under open circuit conditions which is attributed to carbonaceous CH(x) adlayer inhibiting O(2) adsorption and hence poisoning the reaction. Application of a positive potential causes a partial removal of the inhibiting CH(x) adlayer by spillover oxygen thus triggering a transition from thus poisoned state of the surface to an active state with reduced carbon coverage. The ignition effect and therefore also the electrochemical promotion effect are linked to the presence of a carbon adlayer on the surface. The non-Faradayicity which is observed in this reaction system is explained as an ignition effect.