I. INTRODUCTION

With growing interest in high-performance energy devices, development of carbonaceous support with high electrochemical activity and stability has become of central importance for commercialization. To fulfil this purpose, phenolic networks have been frequently used as a carbon precursor that can impart intriguing electrochemical properties typically after pyrolysis. However, most phenolic networks only produce non-graphitizable hard carbons with low residual carbon content, where π-π networks of sp² carbons are rarely recovered during thermal treatment. In this work, for the first time, we achieve graphitizable phenolic networks using a planarized modularization strategy of TA moieties with consecutive C-C coupling and C-O binding at each aromatic unit, producing greatly enhanced structural cyclicity in the form of soft carbon after pyrolysis.

II. RESULTS AND DISCUSSION

Polyphenols are intrinsically prone to full thermal dissociation upon high-temperature carbonization due to thermal instability of ester linkages in the molecular structure, rarely leaving residual carbon support for further electrochemical reactions. To overcome this limitation and improve the carbonizability of polyphenol-based complexes with graphitic structures, in this report, we employed a planarizing modularization strategy of polyphenols through rearrangement of the molecular structure of tannic acid (TA). During this rearrangement process, TA molecules simultaneously undergo C-C coupling and C-O bonding at each aromatic unit with remarkably enhanced molecular cyclicity to generate modularly interconnected TA (m-TA). The carbonized m-TA provides high residual carbon content (42% after 900°C pyrolysis) and maintains the intrinsic graphitic carbonaceous matrix. Furthermore, electrochemically active metallic species (Ni, Co, Fe, or Sn) were readily introduced along with a planarized frame of the carbonized m-TA. As such, the graphitic sp² domains hybridized with reduced metallic nanoclusters present in carbonized m-TA synergistically imparted outstanding ionic and electrical conductivities. The ideally created new electrochemical platform of graphitically carbonized m-TA was utilized as a highly stable anode for secondary battery systems and as on-demand electrocatalyst for water splitting with tunable activity. Therefore, our suggested modular interconnecting strategy of m-TA is expected to be utilized as a general platform for other polyphenolic species.

REFERENCES

1. Choi. G.H. et al., “Modularly aromatic-knit graphitizable phenolic network as a tailored platform for electrochemical applications,” Energy Environ. Sci., Vol. 14, No. 5, pp. 3203-3215, 2021.