单层石墨相氮化碳负载Pt4团簇吸附O2的第一性理论研究

采用第一性原理密度泛函理论结合周期性平板模型模拟研究了Pt₄团簇吸附单层石墨相氮化碳(g-C₃N₄)的几何结构和电子性质,以及氧气在其表面上的吸附行为。同时,对比分析了氧气在纯净的石墨相氮化碳和Pt₄团簇上的吸附行为。计算结果表明, Pt₄团簇吸附在3-s-三嗪环石墨相氮化碳表面,并与四个边缘氮原子成键,形成两个六元环时为最稳定构型。Pt₄团簇倾向于吸附在三嗪环石墨相氮化碳的空位并与邻近三个氮原子成键。由于Pt与N原子较强的杂化作用,以及金属与底物之间较多电子转移增强了Pt₄团簇吸附g-C₃N₄的稳定性。另外,对比分析了氧气在纯净的g-C₃N₄和金属吸附的g-C₃N₄上吸附行为,发现金属原子的加入促进了电子转移,同时拉长了O―O键长。Pt₄吸附3-s-三嗪环g-C₃N₄比Pt₄吸附三嗪环g-C₃N₄表现出微弱的优势,表现出明显的基底扭曲以及较大的吸附能。这些结果表明,化学吸附通过调节电子结构和表面性质增强催化性能的较好方法。

Pt4 Clusters Supported on Monolayer Graphitic Carbon Nitride Sheets for Oxygen Adsorption: A First-Principles Study

The structural and electronic properties of Pt₄ nanoparticles adsorbed on monolayer graphitic carbon nitride (Pt₄/g-C₃N₄), as well as the adsorption behavior of oxygen molecules on the Pt₄/g-C₃N₄ surface have been investigated through first-principles density-functional theory (DFT) calculations with the generalized gradient approximation (GGA). The interaction of the oxygen molecules with the bare g-C₃N₄ and the Pt₄ clusters was also calculated for comparison. Our calculations show that Pt nanoparticles prefer to bond with four edge N atoms on heptazine phase g-C₃N₄ (HGCN) surfaces, forming two hexagonal rings. For s-triazine phase g-C₃N₄ (TGCN) surfaces, Pt nanoparticles prefer to sit atop the single vacancy site, forming three bonds with the nearest nitrogen atoms. Stronger hybridization of the Pt nanoparticles with the sp2 dangling bonds of neighboring nitrogen atoms leads to the Pt₄ clusters strongly binding on both types of g-C₃N₄ surface. In addition, the results from Mulliken charge population analyses suggest that there are electrons flowing from the Pt clusters to g-C₃N₄. According to the comparative analyses of the O₂ adsorbed on the Pt₄/HGCN, Pt₄/TGCN, and pure g-C₃N₄ systems, the presence of metal clusters promotes greater electron transfer to oxygen molecules and elongates the O―O bond. Meanwhile, its greater adsorbate-substrate distortion and large adsorption energy render the Pt₄/HGCN system slightly superior to the Pt₄/TGCN system in catalytic performance. The results validate that being supported on g-C₃N₄ may be a good way to modify the electronic structure of materials and their surface properties improve their catalytic performance.