A supramolecular strategy to precisely fabricate binary-doped metal-free graphdiyne for high-performance zinc-air batteries

Binary-doped metal-free carbon materials are promising bifunctional catalysts for rechargeable zinc-air batteries (ZABs) due to their synergetic effect. However, the fabrication of co-doped carbon materials with a well-defined structure, elemental composition and homogeneous distribution of doping elements is highly challenging, creating demand for novel designs and synthesis methods. Herein, a supramolecular strategy is proposed to precisely fabricate binary-doped metal-free graphdiyne. Specifically, trifluoro-substituted graphdiynes with guest molecules (melamine or 1,3,5-triaminobenzene) assembled via hydrogen bonding (N-HMIDLINE HORIZONTAL ELLIPSISF) are synthesized. The introduction of guest molecules into the pore structure of trifluoro-graphdiyne achieves defined non-metal binary doping (N and F atoms) of graphdiyne. The electron transport and charge distribution of the supramolecular-system-based trifluoro-graphdiyne can be tuned by altering the guest molecules. ZABs constructed by the as-prepared trifluoro-graphdiyne supramolecular systems exhibit impressive electrochemical performances, with a low voltage gap of 0.83 V and long-term stability of over 1000 cycles. The peak power density of the ZABs is up to 94.1 mW cm-2 with a high specific capacity of 707.8 mA h g-1 and energy density of 700.3 W h kg-1 (current density: 25 mA cm-2). The proposed supramolecular strategy creates a new route to non-metal multi-doped carbon materials for efficient bifunctional oxygen electrocatalysis and high-performance ZABs, expanding new applications of graphdiyne for ZABs. A supramolecular binary doping metal-free graphdiyne is achieved via controllable N-HMIDLINE HORIZONTAL ELLIPSISF hydrogen bonds between trifluoro-graphdiyne skeleton and guest molecules. The as-prepared zinc-air battery exhibits high cycling stability and specific capacity.