晶相设计钌基纳米催化剂提高CO_(2)甲烷化活性  

Phase engineering of Ru-based nanocatalysts for enhanced activity toward CO_(2)methanation

作　　者：杨冲亚 王玮珏 卓红英 沈铮[1] 张天雨 杨小峰[1] 黄延强[1] Chongya Yang;Weijue Wang;Hongying Zhuo;Zheng Shen;Tianyu Zhang;Xiaofeng Yang;Yanqiang Huang(CAS Key Laboratory of Science and Technology on Applied Catalysis,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China;College of Environmental Science and Engineering,Beijing Forestry University,Beijing 100083,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院大连化学物理研究所,中国科学院航天催化材料重点实验室,辽宁大连116023 [2]北京林业大学环境科学与工程学院,北京100083 [3]中国科学院大学,北京100049

出　　处：《Chinese Journal of Catalysis》2024年第6期226-236,共11页催化学报（英文）

基　　金：国家重点研究与发展计划(2022YFA1506200);中国科学院青年基础研究项目(YSBR-022);中国科学院战略重点研究项目(XDB36030200);国家自然科学基金(22208021,21978286,21925803,U19A2015);中国科学院青年创新促进会(Y2022061);辽宁省青年拔尖人才(XLYC2203108,2007082,1907170).

摘　　要：金属纳米颗粒在许多化学反应中表现出优异的催化性能,因而广泛用于能源和环境等催化领域.形貌是影响其催化行为的关键因素之一,它通过改变金属纳米颗粒表层原子排列结构,进而调控化学反应过程中的物质吸附、催化机理和反应动力学.此外,由于金属存在多种晶相结构,其纳米颗粒暴露的表面结构也可通过改变晶相得以实现.该调控策略可使得纳米颗粒具有独特的表面结构,并展现出不同的催化性能.因此,金属纳米颗粒的晶相设计为优化金属催化剂的催化性能提供了一种有效方式.Ru基纳米催化剂对CO_(2)甲烷化反应具有较好的活性和选择性,且密堆积的Ru(0001)晶面被证明是hcp相Ru纳米催化剂的活性中心,而(10-11)面对CO_(2)甲烷化反应的贡献较小.因此,开发具有更丰富密堆积fcc-(111)表面的Ru基纳米催化剂,有望大幅提高CO_(2)甲烷化的活性.本文首先通过密度泛函理论计算和微观动力学模拟,研究了fcc相Ru纳米催化剂的密堆积(111)晶面上CO_(2)加氢反应的催化机理.结果表明,与hcp-(0001)相比,该密堆积的fcc-(111)表面因能促进CO_(2)的吸附活化,而具有更好的CO_(2)甲烷化反应活性.制备了具有完全暴露fcc-(111)晶面的二十面体Ru金属纳米颗粒,并将其负载于惰性载体氧化铝上,结果表明,CO_(2)甲烷化活性比传统六方密堆积相(hcp)的钌基催化剂高5‒8倍,证实了fcc相催化剂具有更高的甲烷化催化性能.同时,在较高的反应温度下,fcc-晶相的Ru基催化剂在初始反应阶段甲烷化反应活性逐渐下降,但其CO_(2)甲烷化活性仍远高于hcp-相催化剂.原位X射线衍射和环境透射电镜等结果表明,在反应温度高于250°C条件下,fcc-晶相的金属催化剂发生部分晶相转变.该相变主要发生于Ru金属纳米颗粒的聚集体,并伴随着金属粒子的团聚和粒径的增长;然而,单颗粒分散的Ru纳米粒子在相同条件下仍能维持其fcThe catalytic behavior of metal nanocatalysts is intrinsically contingent on the diversity of their exposed surfaces,which can be substantially regulated through the phase engineering of metal nanoparticles.In this study,it is demonstrated that the face-centered cubic(fcc)phase Ru with a close-packed(111)surface presents superior catalytic activity towards CO_(2)methanation.This behavior is attributed to its enhanced capability toward CO_(2)chemisorption derived from its inherently high surface reactivity.Complete exposure of such surfaces was successfully achieved experimentally by the synthesis of icosahedral Ru metal nanoparticles,which exhibited remarkable performance for CO_(2)methanation with 5–8 times higher activity than its conventional hexagonal close-packed(hcp)counterpart when supported on inert supports.However,for the joined fcc-Ru nanoparticles in the fresh catalyst,an fcc-to hcp-phase transformation was observed at a relatively high temperature with the in situ characterizations,which resulted in metal agglomeration and led to catalyst deactivation.However,the CO_(2)conversion was still much higher than that of the hcp-phase Ru nanocatalysts,as the monodispersed particles could maintain their fcc phase.Our results demonstrate that phase engineering of Ru nanocatalysts is an effective strategy for a catalyst design with improved catalytic performance.However,the phase transformation could represent a latent instability of the catalysts,which should be considered for the further development of robust catalysts.

关 键 词：晶相设计 面心立方相 钌纳米催化剂 二氧化碳甲烷化 相变 

分 类 号：O643.36[理学—物理化学] TB383.1[理学—化学]