后处理调控PtCe催化剂表面形貌及表面压缩应变行为探究
发布时间：2018-08-31 08:12
【摘要】：由于铂(Pt)特殊的电子结构(空d轨道)使其具有较高的析氢催化活性和催化稳定性等优势,在燃料电池、尾气净化、石油化工及氢能源制备等领域有着广泛的应用。然而,纯Pt/C作为催化剂,在催化反应的过程中容易产生颗粒聚集,不仅降低Pt的利用率,而且还降低了 Pt的催化活性,阻碍了 Pt在工业和商业中的实际运用,使其优良的催化性能无法大规模推广。因此,研发一种低Pt用量且高催化活性的Pt基催化剂是当今燃料电池领域的研究热点。本文采用离子束溅射技术(IBS)制备了不同Ce含量的PtCe/C合金催化剂,接着进行400℃真空热处理,通过测试合金催化剂的电化学性能确定最优Ce含量,最后对Ce含量最优样品进行不同时间的腐蚀。然后,通过CV分析催化剂的析氢峰面积,LSV分析催化剂的交换电流密度;采用电感耦合等离子体发射光谱(ICP-AES)分析催化剂的元素含量,X射线衍射(XRD)分析物相组成,高分辨透射电镜(HR-TEMSTEM)分析催化剂的表面形貌和颗粒结构及晶格相,X射线光电子能谱(XPS)分析表面元素化学态变化。结果表明:(1)电化学催化性能分析表明靶位移动30mm时制备的PtCe/C合金催化剂的催化性能最好,其交换电流密度最接近纯Pt/C催化剂的值,Ce含量达到最优。接着对Ce含量最优样进行电化学去合金化处理发现,腐蚀1h的PtCe/C合金催化剂的催化性能最好,其交换电流密度i0达到5.72×10-3A/cm2比纯Pt/C(3.9410-3A/cm2)提高了 45.18%,其析氢峰积分面积为5.28×10-4A·V比纯Pt/C(2.45×10-4A·V)提高了 115.51%,极大地增加了催化剂与电解液的接触面积,而Pt载量为9.64×10-2mg/cm2比纯Pt/C(1.43×10-1mg/cm2)减少了32.59%,充分体现了低Pt用量高催化活性的特点。(2)XRD检测发现,腐蚀前后PtCe/C合金催化剂的Pt峰相对于纯Pt/C均向大角度偏移,说明Ce的加入导致Pt的晶面间距减小。并且经过电化学去合金处理后,PtCe/C合金催化剂的Pt峰向大角度偏移更大,这是由于去合金化处理刻蚀掉大量Ce元素,产生大量的零维缺陷,不仅降低了晶粒的晶面间距,而且也进一步在样品表面形成了类蜂窝状的纳米多孔结构,增加了样品的表面粗糙度和与电解液接触的比表面积。(3)STEMEDS及HR-TEM检测分析表明电化学去合金化处理后存在分布均匀、粒径范围为6-10nm的以Pt为主要成分的球状颗粒,裸露在颗粒表面的Pt元素相对含量增高,与反应物接触更充分,颗粒中Pt的晶面间距相对于标准Pt被压缩发生晶格压缩应变,降低了 Pt与含氧中间体的结合力,提高了 Pt对催化析氢的反应活性。(4)XPS分析表明,电化学腐蚀后样品的Pt4f峰的结合能向低能级区移动,使Pt更接近费米能级附近,化合态pt2+的含量增多49.84%,提高了电子云密度;同时样品表面存在大量电负性较高且容易得到电子的晶格氧。二者综合增强PtCe/C合金催化剂的催化活性。
[Abstract]:Platinum (Pt) has been widely used in fuel cell, tail gas purification, petrochemical industry and hydrogen energy preparation due to its high catalytic activity and stability due to its special electronic structure (empty d orbit). However, as a catalyst, pure Pt/C is easy to produce particle aggregation in the process of catalytic reaction, which not only reduces the utilization ratio of Pt, but also reduces the catalytic activity of Pt, which hinders the practical application of Pt in industry and commerce. Its excellent catalytic performance can not be popularized on a large scale. Therefore, research and development of a Pt catalyst with low Pt content and high catalytic activity is a hot topic in fuel cell field. In this paper, PtCe/C alloy catalysts with different Ce content were prepared by ion beam sputtering technique (IBS), and then vacuum heat treatment at 400 鈩，
本文编号：2214411
[Abstract]:Platinum (Pt) has been widely used in fuel cell, tail gas purification, petrochemical industry and hydrogen energy preparation due to its high catalytic activity and stability due to its special electronic structure (empty d orbit). However, as a catalyst, pure Pt/C is easy to produce particle aggregation in the process of catalytic reaction, which not only reduces the utilization ratio of Pt, but also reduces the catalytic activity of Pt, which hinders the practical application of Pt in industry and commerce. Its excellent catalytic performance can not be popularized on a large scale. Therefore, research and development of a Pt catalyst with low Pt content and high catalytic activity is a hot topic in fuel cell field. In this paper, PtCe/C alloy catalysts with different Ce content were prepared by ion beam sputtering technique (IBS), and then vacuum heat treatment at 400 鈩，
本文编号：2214411
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