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

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.