Synthesis of Atomically Dispersed Rh Catalysts on Oxide Supports via Strong Electrostatic Adsorption and Characterization by Cryogenic Infrared Spectroscopy
Synthesis of Atomically Dispersed Rh Catalysts on Oxide Supports via Strong Electrostatic Adsorption and Characterization by Cryogenic Infrared Spectroscopy
复制标题
DOI：
10.1021/acs.jpcc.2c05426
复制
发表时间：
2022-10
期刊：
影响因子：
--
通讯作者：
C. Asokan;Mingjie Xu;S. Dai;Xiaoqing Pan;P. Christopher
中科院分区：
文献类型：
--
作者：
C. Asokan;Mingjie Xu;S. Dai;Xiaoqing Pan;P. Christopher
氧化物负载的铑催化剂的应用范围从汽车催化中的氮氧化物还原反应到碳氢化合物升级中的加氢反应。人们对合成催化剂的兴趣源自于促进这种稀有元素的有效利用和发现替代催化反应性的潜力，其中Rh以原子分散的形式存在于氧化物载体上而不是Rh纳米颗粒上。合成原子分散的铑催化剂具有挑战性，因为金属物质通常在热力学上更倾向于形成簇。表征氧化物负载的 Rh 物质的结构也具有挑战性，因为已知 Rh 在氧化物载体上可移动，导致表征期间发生烧结或再分散。在这里，我们确定了 pH 值、Rh 前体形态和载体组成对通过强静电吸附在商业相关氧化物载体（CeO2 和 γ-Al2O3）上合成原子分散的 Rh 物种的影响。 CO 探针分子红外光谱 (CO-FTIR) 用于区分原子分散的 Rh 物种与 Rh 簇，重点放在防止 Rh 迁移的低温下的测量。像差校正扫描透射电子显微镜成像证实了 CO-FTIR 对 Rh 物种的结构分析。据观察，对于Rh前体强静电吸附到氧化物载体上的最佳合成条件对于产生原子分散的Rh物质也是最佳的。这里提出的合成和表征方法提供了一种可以促进催化反应结构-功能关系发展的方法。
Oxide-supported Rh catalysts are utilized in applications ranging from NOxreduction reactions in automotive catalysis to hydrogenation reactions in hydrocarbon upgrading. Interest in synthesizing catalysts in which Rh exists as atomically dispersed species on oxide supports rather than Rh nanoparticles derives from the potential to promote the efficient use of this rare element and uncover alternative catalytic reactivity. Synthesizing atomically dispersed Rh catalysts is challenging because the metal species often thermodynamically prefer to form clusters. Characterizing the structure of oxide-supported Rh species can also be challenging because Rh is known to be mobile on oxide supports, leading to sintering or redispersion during characterization. Here, we establish the influence of pH, Rh precursor speciation, and support composition on the synthesis of atomically dispersed Rh species on commercially relevant oxide supports (CeO2and γ-Al2O3) via strong electrostatic adsorption. CO probe molecule infrared spectroscopy (CO-FTIR) is used to distinguish atomically dispersed Rh species from Rh clusters, and focus is placed on measurements at cryogenic temperature that prevent Rh mobility. The structural analysis of Rh species by CO-FTIR is substantiated by aberration-corrected scanning transmission electron microscopy imaging. It is observed that synthesis conditions that are optimum for strong electrostatic adsorption of Rh precursors onto the oxide supports are also optimum for producing atomically dispersed Rh species. The synthesis and characterization approach presented here provides a methodology that could facilitate the development of structure–function relationships for catalytic reactions.