Cheah Seng Kian, Bernardet Véronique P, Franco Alejandro A, Lemaire Olivier, Gelin Patrick
CEA (Alternative Energies and Atomic Energy Commission of France), DRT, LITEN, DEHT, LCPEM (Laboratory of Components for Fuel Cells and Electrolyzers, and of Modeling), F-38054 Grenoble, France.
Université Lyon 1, CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l'environnement de Lyon, F-69626 Villeurbanne, France.
Phys Chem Chem Phys. 2016 Jun 1;18(22):15278-88. doi: 10.1039/c6cp01845a.
The CO oxidation reaction on carbon-supported Pt nanoparticles (average size of 2.8 to 7.7 nm) was studied under flowing conditions at atmospheric pressure and temperatures between 300 and 353 K by coupling quadrupole mass spectrometry (QMS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The Pt loading was varied between 20 and 60 wt%. Gases diluted in He (0.5 mol%) were used together with Ar as a tracer. Reactions with CO and O2 introduced separately onto the samples were studied by QMS, applying successive step changes of the reaction mixtures. Variations in the rate of the reactions were observed and correlated with changes of the calculated coverage of the Pt surface by CO and/or O adspecies at varying steps of the experiment. The transient reaction of CO(g) with adsorbed O (Oad) was fast and mass transport-limited while that of O2(g) with adsorbed CO (COad) was sluggish. Following the same experimental procedures, FTIR spectra of adsorbed CO after varying steps were recorded, confirming the variations of COad and Oad as determined by QMS and indicating changes in the CO distribution over varying types of Pt surface sites. The influence of the adlayer composition (co-adsorption of COad and Oad), the particle size/structure and some possible surface reconstruction effects on the CO oxidation rate were evidenced and discussed. The structure of the Pt nanoparticles supported on carbon appears as an important factor for the efficiency of the so-called O2 bleeding as a CO mitigation strategy in polymer electrolyte membrane fuel cells.
通过将四极杆质谱（QMS）与漫反射红外傅里叶变换光谱（DRIFTS）联用，在大气压和300至353 K的温度下，对负载在碳上的铂纳米颗粒（平均尺寸为2.8至7.7 nm）上的CO氧化反应进行了流动条件下的研究。铂负载量在20至60 wt%之间变化。用氦气稀释的气体（0.5 mol%）与氩气一起作为示踪剂使用。通过QMS研究了分别引入到样品上的CO和O₂的反应，采用反应混合物的连续阶跃变化。观察到反应速率的变化，并与实验不同步骤中计算得到的铂表面CO和/或O吸附物种覆盖度的变化相关联。CO(g)与吸附的O（Oad）的瞬态反应很快且受质量传输限制，而O₂(g)与吸附的CO（COad）的反应则很缓慢。按照相同的实验步骤，记录了不同步骤后吸附CO的FTIR光谱，证实了QMS测定的COad和Oad的变化，并表明了不同类型铂表面位点上CO分布的变化。证明并讨论了吸附层组成（COad和Oad的共吸附）、颗粒尺寸/结构以及一些可能的表面重构效应对CO氧化速率的影响。负载在碳上的铂纳米颗粒的结构似乎是聚合物电解质膜燃料电池中作为CO缓解策略的所谓O₂排放效率的一个重要因素。
