负载型Au催化剂因其在诸多反应过程中的高催化活性而备受研究者关注. 然而针对负载型催化剂中Au物种结构的有效调控, 以及催化过程中真实构-效关系的探索一直充满了挑战. 用CeO₂为Au物种担载基底, 通过简单煅烧处理引起的CeO₂结构变化, 进而实现Au/CeO₂之间界面作用力的调控. 此研究发现Au纳米颗粒中Au⁰物种具备更为高效的催化室温CO氧化活性, 结合多种原位表征分析, 其室温条件下催化转化效率更依赖于CO吸附能力. 而相比于单原子Au₁和纳米Au颗粒, 所制备的团簇Au/CeO₂催化剂在较高温度(>50 ℃)展现出优异的催化CO氧化反应性能. 随着温度升高, 催化剂表界面O参与的MvK反应路径更易发生, 因此具有更多表界面活性O物种和Au^δ＋位点的团簇Au/CeO₂催化剂展现出最为优异的催化CO氧化性能. 这些发现为高效负载型Au催化剂的制备提供了新思路并深化了对Au/CeO₂催化作用机制的理解.

Supported Au-based catalysts have been attracting continuous attention owing to their outstanding performance in various catalytic applications. However, the complicated environment on the catalyst surface severely hampered the unambiguous illustration of the structural-function relationship for Au-based catalysts. In this work, we developed a facile strategy to fabricate various Au species [Au^n＋ (n>1), Au^δ＋ (0<n<1) and Au⁰] onto the CeO₂ support, which the Au/CeO₂ interaction was distinctively modulated by the CeO₂-x with different calcination temperatures. As-prepared Au/CeO₂-x were valued as catalysts for CO oxidation reaction, which is important for both environmental application and model catalysis. The as-formed clustered Au with δ＋ oxidation state on CeO₂-400 demonstrates the best catalytic performance at 50 ℃, while the Au nanoparticles with dominant Au⁰ atoms are superior for catalyzing CO oxidation at room temperature. However, the monodispersed Au^n＋ single-sites with the highest dispersion are almost inactive for CO oxidation below 50 ℃. On the basis of structural characterizations and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results, we reasonably speculated that the electronic state of Au species plays a predominant role at room temperature for catalytic performance owing to the differentiated CO adsorption ability. This speculation is well in line with our former research finding that the Au^n＋ sites are weak in capturing CO molecules and Au⁰ is favorable for CO adsorption. The surficial O atoms, especially the lattice O atoms, play a minor role in catalyzing CO oxidation for the Au particles within Au/CeO₂-700, implying that the reactant molecules might prefer a L-H pathway at room temperature. In contrast, the clustered Au^δ＋ with moderate CO adsorption ability and abundant interfacial site was apt to participate in the surface reaction with a MvK pathway, in which the reaction between surficial lattice O atoms and adsorbed CO molecules significantly contribute to the catalytic activity. Therefore, the Au/CeO₂-400 catalyst coupling with moderate CO adsorption ability and abundant active O atoms displayed the best catalytic efficiency at elevated temperatures. These findings in this work provided a facile route for the fabrication efficient Au/CeO₂ catalyst, and shed light on the molecular understanding of the reaction path over various Au sites.