Key Laboratory for Special Fuctional Aggregate Materials of Education Ministry, School of Chemistry and Chemical Engineering , Shandong University , Jinan 250100 , P. R. China.
School of Resources and Environment , University of Jinan , Jinan 250022 , P. R. China.
ACS Appl Mater Interfaces. 2018 Apr 25;10(16):13614-13624. doi: 10.1021/acsami.8b02557. Epub 2018 Apr 12.
The palladium species in ceria-based catalysts have a significant influence on their catalytic performance. In this work, the structure evolution of palladium species induced by various calcination rate was investigated and then these calcined catalysts were applied to NO + CO catalytic reaction. Systematic investigations by various measurements demonstrate that the calcination rate and catalytic process play crucial roles on the formation ways of palladium species and identify the forms of active palladium surface sites for NO + CO reaction. Results indicate that the calcination process resulted in the formation of three types of palladium components: PdO interacted with ceria supports (PdO /Pd-O-Ce cluster), PdO nanoparticles on the surface, and Pd ions incorporated into the subsurface lattice (Pd-O-Ce solid solution). It is also proven that the state and distribution of palladium components are dependent on the calcination rate: rapid calcination rate is beneficial for the generation of PdO species (PdO /Pd-O-Ce and PdO), while slow calcination rate makes contribution to the formation of Pd-O-Ce. Furthermore, the subsequent catalytic process could induce the decomposition of PdO /Pd-O-Ce and formation of more fractions of active Pd species in PdO oxide phase. On the basis of the catalytic performances, we found the superior catalytic properties are detected for catalysts containing 0.5% Pd (0.5% is corresponding to the palladium content in molar ratio) with fast calcination rate. This is due to the synergistic effect of active Pd in PdO decomposed form PdO /Pd-O-Ce in the catalytic process and the palladium ions in Pd-O-Ce solid solution.
铈基催化剂中的钯物种对其催化性能有重要影响。在这项工作中，研究了不同煅烧速率诱导的钯物种结构演变，然后将这些煅烧催化剂应用于 NO + CO 催化反应。通过各种测量的系统研究表明，煅烧速率和催化过程对钯物种的形成方式起着至关重要的作用，并确定了用于 NO + CO 反应的活性钯表面位点的形式。结果表明，煅烧过程导致了三种类型的钯组分的形成：与氧化铈载体相互作用的 PdO（PdO /Pd-O-Ce 团簇）、表面上的 PdO 纳米颗粒和掺入次表面晶格中的 Pd 离子（Pd-O-Ce 固溶体）。还证明了钯组分的状态和分布取决于煅烧速率：快速煅烧速率有利于 PdO 物种（PdO /Pd-O-Ce 和 PdO）的生成，而缓慢的煅烧速率有利于 Pd-O-Ce 的形成。此外，随后的催化过程会诱导 PdO /Pd-O-Ce 的分解和氧化钯相中更多活性钯物种的形成。基于催化性能，我们发现具有快速煅烧速率的 0.5%Pd（0.5%是指钯含量的摩尔比）催化剂具有优异的催化性能。这是由于在催化过程中 PdO 分解形式的 PdO /Pd-O-Ce 中的活性 Pd 与 Pd-O-Ce 固溶体中的钯离子之间的协同作用所致。
