石墨碳氮化物上单金属原子的稳定化,Advanced Functional Materials

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石墨碳氮化物上单金属原子的稳定化
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2017-01-13 , DOI: 10.1002/adfm.201605785
Zupeng Chen ₁ , Sharon Mitchell ₁ , Evgeniya Vorobyeva ₁ , Rowan K. Leary ₂ , Roland Hauert ₃ , Tom Furnival ₂ , Quentin M. Ramasse ₄ , John M. Thomas ₂ , Paul A. Midgley ₂ , Dariya Dontsova ₅ , Markus Antonietti ₅ , Sergey Pogodin ₆ , Núria López ₆ , Javier Pérez-Ramírez ₁

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石墨碳氮化物（g-C ₃ N ₄）具有独特的性质，可作为单原子非均相催化剂（SAHC）的载体。了解合成方法，载体性质和金属特性如何影响金属中心的隔离对于指导其设计至关重要。这项研究比较了通过在g‐C ₃ N _4中掺入钯，银，铱，铂或金来制备SAHC的直接途径和合成途径的有效性形态各异（散装，中孔和脱落）。负载金属的形态（单原子，二聚体，簇或纳米粒子），分布和氧化态通过多种技术进行表征，包括广泛使用像差校正电子显微镜。通过使用可共聚金属前体和使用高表面积载体的直接方法，最容易获得SAHC。相比之下，尽管合成后途径可以改善对金属负载的控制，但纳米颗粒的形成更为普遍。载流子形态的比较还指出了缺陷在稳定单个原子中的作用。不同的金属分散体通过密度泛函理论和动力学蒙特卡洛模拟得到合理化，强调了吸附能与扩散动力学之间的相互作用。对1-己炔进行连续三相半氢化的评估表明，控制金属与载体的相互作用以及暴露表面层的金属位点是设计高效SAHC的关键挑战。

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Stabilization of Single Metal Atoms on Graphitic Carbon Nitride

Graphitic carbon nitride (g‐C₃N₄) exhibits unique properties as a support for single‐atom heterogeneous catalysts (SAHCs). Understanding how the synthesis method, carrier properties, and metal identity impact the isolation of metal centers is essential to guide their design. This study compares the effectiveness of direct and postsynthetic routes to prepare SAHCs by incorporating palladium, silver, iridium, platinum, or gold in g‐C₃N₄ of distinct morphology (bulk, mesoporous and exfoliated). The speciation (single atoms, dimers, clusters, or nanoparticles), distribution, and oxidation state of the supported metals are characterized by multiple techniques including extensive use of aberration‐corrected electron microscopy. SAHCs are most readily attained via direct approaches applying copolymerizable metal precursors and employing high surface area carriers. In contrast, although post‐synthetic routes enable improved control over the metal loading, nanoparticle formation is more prevalent. Comparison of the carrier morphologies also points toward the involvement of defects in stabilizing single atoms. The distinct metal dispersions are rationalized by density functional theory and kinetic Monte Carlo simulations, highlighting the interplay between the adsorption energetics and diffusion kinetics. Evaluation in the continuous three‐phase semihydrogenation of 1‐hexyne identifies controlling the metal–carrier interaction and exposing the metal sites at the surface layer as key challenges in designing efficient SAHCs.

更新日期：2017-01-13

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