Characterization of atomic structure of single Pt atoms on N-doped graphene

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K15439
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 29020:Thin film/surface and interfacial physical properties-related
• Research Institution: Hokkaido University
• Principal Investigator: Yamazaki Kenji 北海道大学, 工学研究院, 助教 (10732985)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: 金属単原子 / 単原子触媒 / TEM / グラフェン / 単原子スパッタリング

Outline of Final Research Achievements

Single-atom catalysts are attracting attention due to their superior catalytic activity and cost. Nitrogen (N) enhances the stability of single platinum (Pt) atoms on graphene because Pt atoms dispersed by plasma sputtering in an N2 atmosphere are less likely to aggregate. However, the atomic structure of Pt and N on graphene has not been clarified. Here, we experimentally revealed the atomic arrangement of Pt, N, and carbon (C) by scanning transmission electron microscopy and electron energy loss spectroscopy. Pt and N atoms were adsorbed near the step edge of nanographene stacked on single-layer pristine graphene, rather than on the terrace. DFT calculation using the experimental structure confirmed that the single Pt atom has high stability because N strengthens the bond between Pt and C at the step edge. In addition to a large decrease in the population of Pt 5dxy-orbital, an increase in the population of 5dyz-orbital was observed.

Free Research Field

表面科学

Academic Significance and Societal Importance of the Research Achievements

単原子触媒の化学反応活性の高さは吸着構造に大きく影響する。これまでにグラフェン上のPt単原子の多くがグラフェンのステップエッジに多く吸着し、ステップエッジでの原子配置を明らかにしたが、より単原子が安定に存在する窒素ドープグラフェンの原子配置を明らかにした例はこれまでなかった。本研究では収差補正走査透過型顕微鏡（STEM）を用いた電子エネルギー損失分光(EELS)マッピングによって窒素ドープグラフェン上のPt単原子の原子配置を始めて明らかにし、理論計算によって吸着構造の電子状態を明らかにした。