Chemical Dopants on Edge of Holey Graphene Accelerate Electrochemical Hydrogen Evolution Reaction

• Published in: Advanced science 2019-05, Vol.6 (10), p.1900119-n/a
• Main Authors: Kumatani, Akichika, Miura, Chiho, Kuramochi, Hirotaka, Ohto, Tatsuhiko, Wakisaka, Mitsuru, Nagata, Yuki, Ida, Hiroki, Takahashi, Yasufumi, Hu, Kailong, Jeong, Samuel, Fujita, Jun‐ichi, Matsue, Tomokazu, Ito, Yoshikazu
• Format: Article
• Language: English
• Subjects: Carbon; Chemical bonds; chemical doping; Chemical vapor deposition; Communication; Communications; Defects; electrochemical water splitting; Fuel cells; Graphene; graphene edge; Microscopy; Nitrogen; noble metal‐free catalysts; Phosphorus; scanning electrochemical cell microscopy
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.201900119

Carbon‐based metal‐free catalysts for the hydrogen evolution reaction (HER) are essential for the development of a sustainable hydrogen society. Identification of the active sites in heterogeneous catalysis is key for the rational design of low‐cost and efficient catalysts. Here, by fabricating holey graphene with chemically dopants, the atomic‐level mechanism for accelerating HER by chemical dopants is unveiled, through elemental mapping with atomistic characterizations, scanning electrochemical cell microscopy (SECCM), and density functional theory (DFT) calculations. It is found that the synergetic effects of two important factors—edge structure of graphene and nitrogen/phosphorous codoping—enhance HER activity. SECCM evidences that graphene edges with chemical dopants are electrochemically very active. Indeed, DFT calculation suggests that the pyridinic nitrogen atom could be the catalytically active sites. The HER activity is enhanced due to phosphorus dopants, because phosphorus dopants promote the charge accumulations on the catalytically active nitrogen atoms. These findings pave a path for engineering the edge structure of graphene in graphene‐based catalysts. Edge engendering of holey graphene with the edge containing abundant chemical dopants can provide designable carbon‐based electrocatalysts for water splitting. The edge‐enhanced catalytically active sites facilitate hydrogen evolution reactions, directly confirmed by in situ electrochemical measurements with scanning electrochemical cell microscopy. The origin of the catalytic ability is also investigated by density functional theory.