Mussel-inspired surface functionalization of porous carbon nanosheets using polydopamine and Fe3+/tannic acid layers for high-performance electrochemical capacitors

Abstract

A facile mussel-inspired surface modification of interconnected porous carbon nanosheet (IPCN) electrodes is demonstrated through the formation of a polydopamine coating and the subsequent layer-by-layer deposition of ferric ions (Fe³⁺) and tannic acid, with the aim of developing high-performance electrochemical capacitors. After the deposition of the polydopamine coating, the specific capacitance increases by ∼40% as compared to that of an unmodified IPCN electrode. This increase in the capacitance can be explained based on the pseudocapacitance induced by the catechol groups of polydopamine. Furthermore, the electrodes coated with both polydopamine and layers of Fe³⁺ and tannic acid exhibit an additional increase in the capacitance to ∼244 F g⁻¹ at 5 mV s⁻¹, which is ∼83% higher than that of the unmodified IPCN electrode. This is attributable to the presence of many redox moieties, which are introduced by polydopamine and tannic acid. Furthermore, the strong interactions between the Fe³⁺ ions and the catechol groups result in improved capacitance retention even after 1000 cycles. The mussel-inspired surface modification of IPCN electrodes demonstrated in this work can potentially be exploited for developing novel pseudocapacitive electrode materials with excellent performances.