Modularly aromatic-knit graphitizable phenolic network as a tailored platform for electrochemical applications

Abstract

Polyphenols hold tremendous potential for various electrochemical applications due to their non-covalent bonding-based simple coating process and high compatibility with chelating active metallic species. However, polyphenols are intrinsically prone to full thermal dissociation upon high-temperature carbonization due to the thermal instability of ester linkages in the molecular structure, rarely leaving a residual carbon support for further electrochemical reactions. To overcome this limitation and improve the carbonizability of polyphenol-based complexes, 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 a 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 an on-demand electrocatalyst for water splitting with tunable activity.