Mesoporous carbon aerogel supported PtCu bimetallic nanoparticles via supercritical deposition and their dealloying and electrocatalytic behaviour
Mesoporous carbon aerogel supported PtCu bimetallic nanoparticles via supercritical deposition and their dealloying and electrocatalytic behaviour
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DOI：
10.1016/j.cattod.2017.09.023
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发表时间：
2018-07-15
期刊：
影响因子：
5.3
通讯作者：
Erkey, Can
中科院分区：
文献类型：
--
作者：
Barim, Sansim Bengisu;Bozbag, Selmi Erim;Erkey, Can
以超临界二氧化碳（scCO（2））为原料，采用连续超临界沉积（SCD）法制备了介孔碳气凝胶（CA）负载PtCu纳米粒子。研究了金属沉积顺序、退火温度和金属成分对PtCu平均粒径、粒径分布和分散性的影响。用两种Pt：Cu摩尔比（1：1和1：3）和两种不同的沉积顺序（即先沉积Pt或先沉积Cu）制备四组PtCu/CA样品。X射线衍射和电子显微镜数据表明，所制备的样品形成均匀分布的无序PtCu合金纳米粒子的CA载体上的窄粒度分布。在600-950 ℃范围内增加退火温度使平均粒度从1.8 nm增加到4.5 nm，并导致CA表面上分离的Cu纳米颗粒的消除。通过循环伏安法进行负载的PtCu纳米颗粒的脱合金化，并且使用旋转盘电极（RDE）实验研究脱合金化的纳米颗粒（在300个电势循环之后）对氧还原反应（ORR）的活性。在去合金化期间，在初始循环沿着观察到与Cu的本体溶解和沉积以及Cu从合金化PtCu纳米颗粒的溶解和再沉积相关的峰，所述峰与新Pt位点的产生相关。具有Pt的负载纳米颗粒：通过先沉积Cu制备的Cu摩尔比为1：1和1：3的催化剂在脱合金后对ORR的活性较低。相反，通过沉积Pt制备的纳米颗粒在脱合金后首先表现出有希望的电催化活性。Pt：Cu摩尔比为1：3的样品比摩尔比为1：1的样品具有更高的活性。使用Pt：Cu摩尔比为1：3的样品，在800 ℃下退火，获得了137 m2/g的增强的ESA和0.123 A/mg（Pt）的脱合金诱导的增强的质量活度。另一方面，在950 ℃退火的相同样品具有最高的比活度，为0.165 mA/cm（2）。
Mesoporous carbon aerogel (CA) supported PtCu bimetallic nanoparticles were prepared via a sequential supercritical deposition (SCD) method using supercritical carbon dioxide (scCO(2)). The effects of deposition order of the metal, annealing temperature and metal composition on the average PtCu particle size, size distribution and dispersion were investigated. Four sets of PtCu/CA samples were prepared with two Pt:Cu molar ratios (1:1 and 1:3) and with two different deposition orders (i.e. either Pt or Cu first). X-ray diffraction and electron microscopy data showed that all of the as-prepared samples formed homogeneously distributed disordered PtCu alloy nanoparticles with narrow particle size distributions on the CA support. Increasing annealing temperature in the range 600-950 degrees C increased the average particle size from 1.8 nm to 4.5 nm and resulted in the elimination of separate Cu nanoparticles on the CA surface. The dealloying of the supported PtCu nanoparticles were carried out by cyclic voltammetry and the activity of the dealloyed nanoparticles (after 300 potential cycles) towards the oxygen reduction reaction (ORR) was investigated using rotating disc electrode (RDE) experiments. During dealloying, peaks associated with bulk dissolution and deposition of Cu and dissolution and re-deposition of Cu from the alloyed PtCu nanoparticles were observed at initial cycles along with peaks associated with creation of new Pt sites. Supported nanoparticles with Pt: Cu molar ratios of 1:1 and 1:3 which were prepared by deposition of Cu first had low activities towards ORR after dealloying. On the contrary, nanoparticles prepared by depositing Pt first exhibited promising electrocatalytic activities after dealloying. Samples with a Pt: Cu molar ratio of 1:3 showed higher activities than those with a molar ratio of 1:1. An enhanced ESA of 137 m(2)/g and dealloying induced enhanced mass activity of 0.123 A/mg(Pt) was obtained using the sample with a Pt: Cu molar ratio of 1:3, which was annealed at 800 degrees C. On the other hand, the same sample annealed at 950 degrees C had the highest specific activity of 0.165 mA/cm(2).